Short Stress Rolling Mill

The short stress rolling mill refers to the profile rolling mill with short stress loop of the working machine. The stress loop of the working frame refers to the connection of the neutral line of the elastic deformation section of the stressed parts in the rolling mill after the rolling force is applied to the rolling mill. The length of the stress loop is the sum of the lengths of the stressed parts in the rolling mill. The elastic deformation produced by each stressed part in the rolling stand is directly proportional to its sectional area and inversely proportional to its length. The shorter the stress loop in the stand, the smaller the elastic deformation produced, the greater the stiffness of the rolling mill (see the stiffness coefficient of the rolling mill) and the higher the accuracy of the rolled products.

There are two ways to shorten the stress loop of the rolling mill: one is to change the form of the bearing structure of the rolling mill, that is, to reduce the number of bearing parts in the rolling mill base. For example, for the houseless rolling mill, shorten the stress loop by shortening the length of the stressed parts; The second is to change the transmission path of the force, such as making the rolling force not directly act on the upper part of the archway window, but on the column close to the rolling mill, so as to shorten the stress loop.

The advantages of short stress line rolling mill are:

(1) The high rigidity of the rolling mill ensures the high precision of the product, and it is easy to realize negative deviation rolling.

(2) It can realize symmetrical adjustment. This is of great significance for stabilizing operation, improving operation rate, saving maintenance and replacement time of guide beam, reducing operation accidents, avoiding process accidents such as rolled piece elbow, impact and roll winding, and improving the service life of guide.

(3) Because the rolling mill changes the transmission path of force and changes the concentrated load of the pressed screw into the dispersed load scattered on both sides of the bearing pedestal, the stress condition of the bearing and the bearing pedestal is better, and the service life of the bearing is more than 1.5 times higher than that of the ordinary rolling mill, so as to reduce the cost of the product.

(4) The roll system of this rolling mill shall be pre-installed and adjusted before roll change, and the new roll system can be changed about 10min after shutdown. The adjusted new roll system can ensure that the products are qualified after rolling one or two pieces of steel. Therefore, the mill has good preset performance, fast roll change and high yield.

Short stress line rolling mill, also known as no archway rolling mill, is a kind of high stiffness rolling mill. When used as section steel rolling mill, it should not only have high radial stiffness, but also have high axial stiffness. At present, various types of short stress line mills have been developed in China, such as GY type, HB type, CW type, SY type, GW type and DW type. Among them, there are three representative types: Gy type short stress line mill, Hb type non-archway mill and Sy type high stiffness mill. These rolling mills are self-developed with reference to the P-60 Memorial archless rolling mill in Sweden and in combination with their different conditions. Therefore, the high-stress line structure of their main stress parts is similar, but there are some differences in support mode and some specific structures, and each has its own characteristics.

If you are interested in the short stress rolling mill, please mail at marketing2@hanrm.com.

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What Is Cold Rolling Mill?

Cold rolling mill is a new type of steel bar cold rolling equipment. The machine can process hot-rolled wire rods and circles with a diameter of 6.5 mm to 12 mm into cold-rolled ribbed bars with a finished specification diameter of 5 mm to 12 mm. The cold-rolled ribbed steel bar rolled by cold rolling mill is an updated product of cold drawn low-carbon steel wire in prestressed concrete members. In cast-in-situ concrete structure, it can replace grade I steel bar to save steel. It is a better kind of cold-worked steel of the same kind. If speed regulation is not required in the rolling process of the cold rolling mill, AC motor can be used; If speed regulation is required in the rolling process of the cold rolling mill, DC motor can be used.

Structure Composition:

The cold rolling mill is composed of working mechanism and transmission mechanism, in which:

① The working mechanism is composed of frame, roll, roll bearing, roll adjustment mechanism, guide device, rolling seat, etc.

② The transmission mechanism is composed of gear base, reducer, roll, connecting shaft, coupling, etc.

The gantry horizontal double active rolling mill set is composed of two active rolling mills. The installation mode and structure of the two rolling mills are the same. The main transmission part adopts the structural form of "motor → reducer → cardan shaft → rolling mill". 

The two rolling mills are horizontal rolling mills, and the rolls are installed horizontally. The rolling mill adopts gantry archway, the roll ring is sleeved on the roll spindle, and the nuts are fixed. The two ends of the roll spindle are equipped with bearing pedestal and installed in the middle of the gantry. The bearing pedestal and the gantry archway frame are installed together to fix the rolls horizontally in the middle of the gantry. 

The installation methods of the upper and lower rolls are the same. One pass reducing mill flattens the raw materials, extrudes the rib reinforcement with the crescent on both sides through the two-pass forming mill, twists the guide and adjusts the rolled piece to realize that after one pass rolling, the elliptical rolled piece is twisted by 90 ° and enters the two-pass forming mill to roll the finished reinforcement.

Working Principle:

The cold rolling mills use the motor to drag the reinforcement, and the load-bearing roll and working roll of the cold rolling mill jointly apply the force to the two surfaces of the reinforcement. By changing the gap between the two rolls, the purpose of rolling cold-rolled ribbed bars with different diameters is realized.

① Bearing roll: the bearing roll of the cold rolling mill is the roll closest to the base. When producing ribbed reinforcement, the roll plays the role of supporting the reinforcement, and evenly disperses the gravity of the reinforcement and the gravity of the work roll on the bearing roll, so as to produce ribs on the lower surface of the reinforcement.

② Work roll: the work roll of the cold rolling mill is above the load-bearing roll and is the farthest from the base. Therefore, when producing ribbed reinforcement, the roll mainly plays the role of rolling the reinforcement lifted by the load-bearing roll, so as to produce ribs on the upper surface of the reinforcement.

Maintenance:

① Check whether the electrical system of the cold rolling mill is normal before starting each shift;

② Check whether the oil level of each oil tank is normal;

③ Whether each oil filling part is filled with oil;

④ Whether the base metal feeding is reasonable;

⑤ After checking the above items;

⑥ The electrical part of the cold rolling mill should often clean up dust and sundries;

⑦ Frequently check whether the fastening of moving parts is loose and reasonable.

⑧ During the production process, the cold rolling mill shall not be used beyond the limit to avoid damage to some mechanical parts of the cold rolling mill. It shall be rolled according to the rolling standard, so as to ensure the safe use of cold rolling mill equipment and the qualification of products.

If you are interested in the cold rolling mills, please mail at marketing2@hanrm.com.

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Intermediate Frequency Coreless Induction Melting Furnace

Medium frequency coreless induction melting furnace (non-vacuum) adopts controllable silicon static medium frequency power supply for induction heating, which is used for smelting and thermal insulation of non-ferrous metals such as copper, aluminum and stainless steel. Generally, according to the capacity of the furnace body, it is divided into aluminum shell structure and steel shell structure. 

The aluminum shell structure generally adopts the tilting furnace mode powered by a reducer (there are also a few hydraulic tilting furnaces), and the steel shell structure generally adopts the tilting furnace mode powered by hydraulic pressure.

Use Environment and Conditions

1. Ambient temperature 2℃～35℃;

2. The relative humidity does not exceed 90%;

3. The altitude does not exceed 1000 meters;

4. There is no conductive dust and corrosive gas around;

5. There is no danger of explosion and violent vibration around;

6. The cooling water temperature is not less than 5℃ and not more than 35℃. The outlet water temperature is not more than 55℃, the pH value is within the range of 6 to 8.5, and the hardness is not more than 8 degrees (1 liter of water contains 10 mg Cao per degree);

 

7. Three-phase power supply voltage fluctuation is not more than 10%.

Main Technical Parameters

1. Power supply voltage: three-phase 380V

2. Power frequency 50Hz

3 if voltage 1000V

4 if frequency 1500hz

5. Working temperature: 1600 ℃

6. The inlet pressure of cooling water is 0.15 ~ 0.2MPa

Structure Description

The equipment is composed of furnace body, thyristor medium frequency power supply device (optional configuration: furnace tilting controller and cooling system)

1. The furnace body is composed of furnace shell, induction coil, furnace lining, Rzs reducer and other main parts. During smelting, the induction coil, water-cooled cable, capacitor cabinet and thyristor medium frequency power cabinet must be cooled with water. The furnace lining is close to the induction coil and is made of quartz sand. The tilting of the furnace body is directly driven by the tilting reduction box. The tilting reduction is a two-stage worm gear speed change, with good self-locking, stable and reliable rotation. In case of emergency power failure, the furnace can be tilted manually to avoid danger.

2. Intermediate Frequency Device

Thyristor medium frequency power supply is a device that changes three-phase power frequency into single-phase medium frequency to supply power required by the furnace. See the operation manual for circuit principle, operation and maintenance.

Features of Medium Frequency Coreless Induction Melting Furnace

Induction furnace has the advantages of low noise, low power consumption, fast melting speed, high reliability, compact structure, simple operation, reliable operation, high production efficiency, less unit energy, strong overload capacity, easy control of metal composition and less burning loss.

If you are interested in induction melting furnaces, please mail at marketing2@hanrm.com for your solution.

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LF Ladle Furnace Refining Process

1. LF Ladle Furnace Refining Process

LF refining is to pour molten steel into the ladle furnace and remove 50-90% of the oxidized slag, add reducing slag and deoxidizer for reduction refining. If the stirring time, slag amount and stirring power under heating are appropriately increased, 100% slag removal during tapping can further reduce the sulfur content in the steel, so that [%S] <30ppm and [%O] <20ppm can make the molten steel become clean steel.

2. LF Ladle Furnace Refining Deoxidation

The solubility of oxygen in liquids and solids is very limited, and the solubility of oxygen in solid steel is much lower than in liquids. In LF refining, the molten steel from the primary furnace often contains strong oxidizing properties, which makes the LF furnace complete deep deoxidation and desulfurization and other refining tasks constitute a limiting factor. The hazards of oxygen are mainly manifested in:

(1) The LF furnaces need to smelt ultra-low sulfur steel, and the oxygen content in the molten steel or the oxygen potential of the slag will affect the equilibrium distribution of sulfur in the steel slag, and due to the presence of oxygen, the tension between the steel slag will decrease, which will affect the residual properties and quantity of sulfur-containing non-metallic inclusions in steel, so good desulfurization must first have good deoxidation.

(2) The solubility of oxygen in steel decreases significantly with the decrease of temperature, and precipitates in the form of FeO. During the cooling and crystallization process of molten steel, [C] and [O] segregate and aggregate in molten steel due to selective crystallization. , Which causes the re-oxidation of carbon. The resulting CO gas will destroy the compactness or continuity of the steel, which is the main reason for the defects such as pores, looseness and rising of the steel billet.

(3) During the cooling and solidification process of molten steel, the precipitated oxygen reacts with elements such as Si, Mn, Al in the steel to form non-metallic inclusions, which are one of the main causes of hairline defects in high-quality steel. In addition, due to the increase in the content of non-metallic inclusions, various performance indicators of steel, such as proportional limit, impact energy and elongation, and magnetic permeability, are also reduced.

(4) Oxygen in steel aggravates the harmful effects of sulfur, because FeO and FeS can form a low-melting eutectic with a melting point of 1213K, which deteriorates the plasticity of the steel or damages the body during hot working.

LF furnace generally chooses precipitation deoxidation and diffusion deoxidation, such as equipped with vacuum device and vacuum deoxidation.

(1) Precipitation Deoxygenation

Precipitation deoxidation is a method of directly adding massive deoxidizers to molten steel after removing the oxidized slag to generate stable compounds and separate them from the molten steel into the slag. The deoxidizing elements dissolved in the molten steel react with the dissolved oxygen in the molten steel. The deoxidation products in the molten steel float up and are removed due to their low density. The general formula for the deoxidation reaction of elements in molten steel is x[M]+y[O]=MxOy.

A1 and the composite deoxidizer composed of alloys containing A1 and alkaline earth elements are used more in industrial production. This is because Al2O3, the deoxidation product of A1, can easily form a low-melting, easy-to-grow compound deoxidation product (such as mCaO•n Al2O3) with other deoxidation products, which is beneficial to floating up and discharging molten steel, thereby reducing the amount of such fire impurities in the steel.

(2) Diffusion Deoxidation

Diffusion deoxidation is to add deoxidizer (mainly powdered deoxidizer) to the slag surface, and the deoxidation reaction is carried out at the interface between steel and slag. When the powdered deoxidizer is added to the slag, the content of FeO in the slag is bound to decrease, and the distribution balance of oxygen in the steel slag is destroyed. In order to achieve the rebalancing, the oxygen in the molten steel diffuses or transfers to the slag, so as to continuously reduce the oxygen content in the slag, so that the oxygen in the molten steel can be continuously removed.

(3) LF Ladle Furnace Refining Desulfurization

Generally, sulfur is a harmful element in steel, which has many effects on the quality of steel. Therefore, desulfurization is one of the important metallurgical tasks in steelmaking production. For desulfurization reaction, LF furnace refining has good thermodynamic and kinetic conditions. LF furnace refining is of great significance to the production of low-sulfur steel.

Different from alkaline oxidation slag desulfurization, the desulfurization reaction equation of LF alkaline reduction slag is:

　　[FeS] + (CaO) = (CaS) + (FeO)        (1)

　　[MnS] +( CaO) = (CaS) + (MnO)         (2)

Since [S] in steel mostly exists in the form of [FeS], the desulfurization reaction is mainly based on formula (1). It can be seen from the above formula that the desulfurization reaction is related to the basicity of the slag, (FeO) and (MnO) in the slag, and the amount of slag. At the same time, the desulfurization reaction is a slag-steel reaction, so the fluidity of the slag has a greater influence on the desulfurization reaction. 

In the actual production process, within a certain alkalinity range. The distribution coefficient of sulfur increases as the alkalinity of the slag increases, but when it reaches a certain level, it decreases with the increase in alkalinity. The reason is that the increase in the slag (CaO) content makes the fluidity of the slag worse and causes the desulfurization reaction. The kinetic conditions of the desulfurization are worsened, which in turn affects the progress of the desulfurization reaction. 

It can be seen from formula (1) that the increase of the content of (FeO) in the slag is not conducive to the progress of the desulfurization reaction. LF is refined into a reducing atmosphere, and the reduced slag with high basicity is conducive to the progress of the desulfurization reaction. 

The amount and fluidity of the refined slag have a greater impact on the quality of the final steel. Theoretically, the refined slag with good fluidity is beneficial to the slag-steel reaction to promote the desulfurization reaction, and a large amount of slag is beneficial to the sulfur removal in the steel. However, the increase in the amount of slag increases the thickness of the slag layer, which is not conducive to the desulfurization and the floating of inclusions. At the same time, it increases the consumption of metal materials and increases the production cost.

(4) Removal of Inclusions

Argon blowing at the bottom of ladle is the last important process before molten steel continuous casting, which is very important to the quality of liquid steel and billet. There are two main ways for inclusions to float up in liquid steel: relying on their own buoyancy and adhering to the bubble surface. 

In the process of molten steel movement, inclusions will collide and agglomerate into large particle inclusions to float up by their own buoyancy (some inclusions will adhere to the bubble surface and float up by the buoyancy of bubbles). 

Therefore, the ladle bottom blowing system plays an important role in the removal of inclusions in molten steel, and the size of bubbles and the flow of molten steel will affect the floating of inclusions.

The process of removing inclusions by bubbles can be divided into the following processes: 

(1) The bubbles approach and collide with the inclusions; 

(2) The liquid film is formed between the bubbles and the inclusions; 

(3) The inclusions oscillate on the surface of the bubble or along the bubble Surface slippage; 

(4) The liquid film is discharged and ruptured to form a dynamic three-phase contact nucleus (TPC); 

(5) Bubbles/inclusion nuclei are stabilized; 

(6) Bubbles/inclusion aggregates float up. 

Among them, bubbles play an important role in the collision and adsorption of inclusions, namely steps (2)-(5). Therefore, controlling the establishment of a reasonable bottom blowing system according to different smelting conditions at the factory site plays an important role in improving the quality of molten steel.

If you are interested in LF ladle furnace, please mail at marketing2@hanrm.com for your solution.

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1,000,000 Tons Hot Rebar Rolling Mill Line Rolling Case

The bar production line adopts 150 mm × 1 5 0 m m × 600 mm / 900 mm / 1200 mm continuous casting billet as raw material, hot rolled Φ 1 2 ~ Φ 3.2 m round steel or deformed steel bar. The bar line is a fully continuous hot rolling production line, which can realize continuous torsion-free rolling of the whole line. 

Some Data of the Rebar Rolling Mill Line:

Annual productivity: 1 million tons;

Billet specifications: 150mm×150mm×6000mm/9000mm/12000mm square steel billet;

Single billet weight: 1 ton (6m), 1.5 ton (9m), 2 ton (12m);

Finished product specifications: Φ12~Φ32mm small bar (round steel/rebar), of which Φ12~Φ22mm is slit rolling;

Finished steel types: ordinary carbon structural steel, high-quality carbon structural steel, low alloy steel, alloy structural steel;

Rolling speed: the maximum speed of single-line rolling is 18m/s;

The total installed capacity of the main rolling mill: 16.8MW.

TMT Rebar Rolling Mill Equipment Composition and Production Process:

The rebar rolling mill production line is mainly composed of loading equipment in front of the furnace, heating furnace, discharge equipment after the furnace, dephosphorization device, rough and intermediate finishing mills (18 rolling mills), rough, intermediate and finishing rolling flying shears, vertical loopers, water cooling devices, rack walking cooling bed, fixed-length cold shear, bar collection equipment, and packing device. 

The production process flow mainly includes feeding, heating, dephosphorization, continuous rolling, flying shear, cooling, collection and packaging, etc. 

The process flow chart is as follows:

The transmission of this hot strip production line can be divided into two parts. One part is the main driving part of the rolling mill for hot continuous rolling of steel billets, including the roughing mill, intermediate rolling mill and finishing mill; the other is the auxiliary driving part, including flying shears, roller drives, etc. The capacity of the main drive rolling mill motor is generally between 500kW and 1.5MW; the capacity of the auxiliary drive motor is generally below 300kW.

There are 18 rolling mills in the whole line, which are arranged in a full continuous horizontal and vertical alternate arrangement. The rolling mill motor adopts a 6-pole 690V AC asynchronous variable frequency motor with a power of 600kW~1.5MW. The total capacity of the rolling mill motor is 16.8MW. 1#~6# motors are rough rolling mills, 7#~12# motors are medium rolling mills, and 13#~18# motors are finishing mills. The 18 rolling mill motors are divided into 5 busbar groups according to the principle of power uniformity (as shown in the figure below), which are driven by their respective inverters.

Each busbar group is composed of four parts: power distribution cabinet, rectifier cabinet, inverter cabinet, and braking cabinet. They are connected in common busbar mode, and the rectification capacity of each busbar group is 4MW. The rolling pieces between the roughing and intermediate rolling mills are rolled with micro-tension and no torsion. The six rolling mills of the finishing mill are equipped with 5 vertical loops. The rolling pieces can be rolled without tension and torsion in the finishing mill.

Advantages of the Main Drive of the Hot Rebar Rolling Mill Line

1. With three voltage levels of 380V, 480V, and 690V, it can meet the voltage level requirements of AC main drive motors of mainstream rolling mills in the iron and steel industry;

2. Adopting optical fiber parallel technology, the power of a single system is 200kW~2MW, and it supports the parallel connection between systems, which fully meets the demand for large-capacity AC drives of the AC high-power main drive motor of the steel rolling production line in the steel industry;

3. Application of high-end vector variable frequency drive technology, its excellent performance, steady-state speed accuracy, low-frequency torque characteristics, torque response, speed response, speed range and other performance fully meet the process drive requirements of the AC main drive system of the rolling mill line in the steel industry;

4. The perfect DP non-standard function and the online FVC/SVC switching function help ensure the safety and reliability of the system and meet the continuous production requirements of steel enterprises under special working conditions;

5. Support 3 kinds of communication protocols, industrial Ethernet, PROFIBUS-DP and Modbus RTU, which is convenient for the field bus application in the steel industry;

6. With corresponding four-quadrant products, the application of the main drive of the rolling line can omit the brake cabinet, and at the same time can improve the energy utilization rate and increase the system power factor (up to 0.99 or more), which can reduce the capacity cost of the power supply transformer on the grid side. It also helps users save investment in reactive power compensation equipment; it also greatly reduces external harmonics, adhering to the concept of green environmental protection;

 

7. The seamless combination of fault memory and touch screen facilitates on-site equipment maintenance and diagnosis;

8. The same structure is modularized in parallel, which is convenient for installation, replacement and maintenance.

If you are interested in the hot rebar rolling mill line, please mail at marketing2@hanrm.com.

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What Is Universal Rolling Mill?

The universal rolling mill is composed of a pair of horizontal rolls and a pair of vertical rolls. The axis of the four rolls is in a plane. The horizontal rolls are the driving rolls and the vertical rolls are the driven rolls (some rolling mill vertical rolls can also be driven). It can process the rolled pieces on four sides, and the two-high horizontal rolling mill is used as the auxiliary stand (edge ​​rolling machine).

Universal rolling mills are mainly used to roll various types of steel, such as H-beam, rail, I-beam, channel steel, steel sheet pile, U-beam, L-beam, unequal angle steel and other types of steel, because it is suitable for many Variety of steel rolling, hence the name "universal rolling mill".

Features of Universal Rolling Mill

1. The complex section shape composed of four rollers can compress all components of the section at the same time, the deformation of the rolled piece is uniform, the speed difference around the section is small, and the internal stress of the rolled piece is small.

2. Rolls with a smaller diameter can be used (because there is no need to slot on the rolls) to roll products with higher legs and wider waists, and the inner sides of the legs can be made without slope. This is difficult to achieve on an ordinary two-high rolling mill.

3. The reduction of the leg and waist of the rolling piece can be adjusted separately, which simplifies the adjustment of the rolling mill during rolling.

4. The rolling precision is high, the roll wear is less, and the energy consumption is reduced.

According to the structure of the universal rolling mill, there are four main types: closed-end, UD (Universal-Duo) prestressed/short-stressed, SC (Schloemann-Siemag compact stand) connecting plate three-type and compact rolling mill.

The Development History of Universal Rolling Mill

1. The world's first universal rolling mill was built in the Arbed factory in Luxembourg in 1902, but the I-beam with a wider flange was rolled at that time, and the inner side still had a slope.

2. In 1914, the German Payin Company adopted the Green rolling method (a side rolling mill and a universal rolling mill are used together) to build the Payin H-shaped steel plant; the rolling of the rails adopts the traditional two-roll pass method.

3. In 1973, the French Vendell-Sidelor Company developed a new process for rolling steel rails on a four-high rolling mill and obtained a patent. Japan, Brazil, and the United States have followed suit and introduced them.

4. In 1998, Maanshan Iron & Steel rolled out China's first H-beam with a universal rolling mill imported from abroad.

5. Localized import and export: Since then, Laiwu Steel, Rizhao, Jinxi and other steel mills have successively introduced foreign universal rolling mills. By 2007, the number of universal rolling mills in China has shown a rapid increase, and most of the equipment has been imported at high prices from abroad. Among them, in 2003, the 300H section steel production line designed and manufactured by Tianjin Zhongzhong Science and Technology Engineering Co., Ltd. was put into operation, marking the official launch of China's self-developed universal rolling mill. Since then, the universal rolling mills of Dalian Zhengda, Tangshan Shengda, Anshan Zizhu (Anshan No. 3 Rolling), and Anshan Baode, designed and manufactured by Tianjin Zhongzhong, have been put into operation one after another.

If you are interested in our rolling mill machine, please mail at marketing2@hanrm.com.

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Bar Heating Induction Furnace

The induction furnace for bar heating is well understood from the literal meaning, that is, the medium frequency furnace for heating bar. However, the connotation is not simple, and the bar heating process is relatively complex. Why do we think the bar heating induction furnace is complex? Let's give you a detailed introduction.

1. Differences between bar heating induction furnace and other heating furnaces

1) The heating principle is different

Most of the previous bar heating furnaces used coal, gas, oil, and resistance heating. The heating principle is radiation heating, that is, the furnace is heated to a certain temperature and transmitted to the heating bar through heat radiation, so that the bar temperature can reach the process heating temperature; The medium frequency furnace for bar heating adopts the principle of electromagnetic induction heating, which cuts the metal through the magnetic line of force, forms a vortex in the bar, the current flows, and the bar heats itself, so as to achieve the purpose of heating the bar. In other words, in the past, the heating furnace heated the bar through heat conduction, but now the heating furnace of Haishan electric furnace generates eddy current through the magnetic line of force, making the bar heat itself.

2) The heating speed is different

The previous bar heating furnace had to raise the furnace temperature to the process temperature for a long time; Now, the bar heating of electric furnace, the instantaneous electromagnetic induction of the medium frequency furnace can make the bar reach the temperature required by the heating process, which does not need the preliminary preparation for furnace temperature rise and reduces the labor intensity.

3) Meet the environmental protection requirements

The previous heating furnace will produce a large amount of smoke and dust in the combustion of coal, oil and gas, while the bar heating induction furnace makes the bar heat itself and will not produce smoke and dust, which meets the environmental protection requirements. It belongs to the heating industry and advocates the development of water temperature heating equipment.

4) The utilization rate of bar material is different

In the past, the heating time of heating furnace was long, the oxidation burning loss was large, and the utilization rate of bar oxide scale was reduced; Nowadays, the medium frequency furnace for bar heating of Haishan electric furnace has fast heating speed, reduced oxidation burning loss, greatly reduced relative oxide scale and greatly improved bar utilization.

2. Basic parameters of induction furnace for bar heating

1) The induction furnace for bar heating is expressed by heating power and heating frequency: 

the heating power is 100kW -- 20000KW; The heating frequency is different according to the outer diameter of the bar, and the frequency range is 50Hz --- 8000Hz:

2) The medium frequency furnace for bar heating is mainly composed of the thyristor control circuit, and the model is expressed as: 

KGPS power / frequency; 

The heating furnace head is expressed as GTR - bar diameter; 

KGPS is used together with GTR and cannot be used alone.

3) The material of bar heating induction furnace heating bar is: alloy steel, alloy aluminum, stainless steel, alloy copper, titanium alloy and other metal materials

4) The heating temperature of medium frequency furnace for bar heating can be heated at different temperatures according to the heating process requirements. Generally speaking, the forging heating temperature is 1200 ℃; The quenching heating temperature of bar material is between 700 ℃ - 1000 ℃; The tempering heating temperature of bar material is between 450 ℃ - 600 ℃; Warm forging temperature is between 800 ℃ - 9000 ℃;

3. Auxiliary equipment of induction furnace for bar heating

Bar heating medium frequency furnace is commonly used in bar forging heating industry and bar quenching and tempering heating industry. Supporting auxiliary equipment can realize the automation of heating production line. These auxiliary equipment include automatic feeder, roller conveyor, cylinder pushing, temperature detection device, PLC control system, discharge system, hsbl cooling system, power supply device, etc, The main purpose is to realize the intellectualization of bar heating medium frequency furnace production line, and it is also the main force of intelligent factory construction at present.

To sum up, the bar heating medium induction furnace has obvious heating characteristics, is deeply loved by people in the heating industry, and is also the mainstream equipment in the bar heating industry at present.

If you are interested in bar heating induction furnace, please mail at marketing2@hanrm.com for your solution.

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How to Deal with the 9 Accidents in the Blast Furnace Production Process?

1. How to deal with sudden burning of air outlet and water cut?

The treatment scheme is as follows:

●  Stop the fuel injection at the air outlet quickly, spray water outside the air outlet for cooling, and arrange special personnel to monitor it to prevent burning out.

●  Change atmospheric operation or air release according to the situation.

●  Organize slag and iron out, prepare to stop air and replace it.

●  In order to reduce the leakage of water into the furnace, the wind should be reduced to strive for a bright tuyere before the wind is stopped, so as to prevent the tuyere from sticking to the iron and prolong the wind break time.

2. How to deal with the burning of air supply pipes?

●  When the blowing pipe is found to be red and the pit slag is found, the fuel injection shall be stopped.

●  It is found that the burning out part should be sprayed with water to prevent expansion.

●  Immediately change the atmospheric pressure and let the air pressure down to the point where no slag is poured.

●  Quickly open slag and iron port to discharge slag and iron, and then replace it after discharge.

3. How to deal with the emergency water stop of the blast furnace?

●  When the low water pressure alarm sends out a signal, it is necessary to prepare for an emergency water stop immediately. Firstly, reduce the cooling water of each part of the furnace body to ensure the cooling of the air outlet.

●  Immediately release the wind, organize slag and iron out quickly, and strive to stop the wind early and strive for no slag filling at the air outlet.

●  Start normal water supply, and operate in the following order after the water pressure is normal:

1) Check whether there are burnt air outlets and slag outlets. If so, quickly organize the replacement.

2) Turn down the main valve of tap water.

3) Firstly, the cooling water of vent shall be cooled. If it is found that the cooling water at the air outlet is exhausted or steam is generated, the water shall be slowly drained one by one or in sections to prevent the steam explosion.

4) After the water is normal at the air and slag mouth, the water supply shall be slowly restored from the furnace cylinder to the upper section, and the steam explosion shall be prevented.

5) Only when the water tank of each section is normal and the water pressure is normal, the air can be supplied.

4. What should the blower do to stop the air suddenly?

The main danger of sudden wind stop of the blower is:

●  The gas flows back to the air supply system, causing the blast of the air supply pipeline and fan.

●  All air outlets, blowpipes and elbows may be filled with slag due to sudden fan shutdown.

●  The explosion was caused by negative pressure in gas pipeline.

Therefore, in case of sudden wind stop of the fan, the following treatment shall be carried out immediately:

●  Close the mixing air control valve and stop coal injection and oxygen enrichment.

●  Stop feeding.

●  Stop the automatic regulation of the pressure valve group.

●  Open the top discharge valve and close the gas shut-off valve.

●  Steam the downcomer to the top and dust collector.

●  Send out the stop air signal, notify the hot blast stove to first heat the blast valve and open the cold blast valve and flue valve.

●  Organize the workers in front of the furnace to inspect the tuyere and immediately open the big cover of the elbow when the slag is entering to prevent the slag from filling the blowpipe and the elbow.

5. How to deal with the nodulation of blast furnaces?

The nodulation of the blast furnace is that the melted material in the furnace is condensed on the furnace wall, and it is integrated with the furnace wall refractory brick. It can not be eliminated automatically under normal smelting conditions, and the thicker the accumulated, the final serious impact on the furnace charge falling, even becomes an obstacle that can not be normal production of the blast furnace.

According to the chemical composition, the tumor can be divided into the carbonaceous tumor, gray matter tumor, alkali metal tumor and iron tumor; According to its shape, it can be divided into ring tumor and local tumor; According to the location of the tumor, it can be divided into upper tumor and lower tumor. 

The treatment method is:

Washing the tumor. The lower tumor is sometimes effective with a lot of fluorites. The method of cleaning the tumor: one is to adopt the method of full inversion and adding clean coke to strongly develop the edge airflow, so that the furnace tumor is melted under the action of the high-temperature airflow; the other is to spread the cleaning agent (such as soaking slag, fluorite, etc.) At the edge, use its good fluidity to wash the furnace wall. Both methods need to greatly reduce the load to prevent the furnace from cooling.

Burst blasting, the upper furnace bulge forms a large area of ​​furnace bulge up and down, which cannot be solved by washing the furnace. The blasting method must be used. 

The blasting operation is as follows:

●  Lower the material surface so that the furnace knob is completely exposed. Before lowering the material, install a water spray device on the top of the furnace and a soft probe to control the temperature of the furnace top and accurately determine the position of the material surface, and add 3-5 batches of net coke to prevent the furnace from cooling when the air is re-aired.

●  After it is estimated that the furnace nodules are completely exposed, stop the air, observe the situation in the furnace from the top of the furnace, and determine the exact position of the furnace nodules.

●  Make a blast hole on the furnace wall of the nodule, put in explosives, explode the bulge in sections from bottom to top, first blast the root of the bulge, and move upward in turn.

●  The place where the explosives are placed should be 100~200mm away from the furnace wall to avoid blasting the furnace wall.

●  The amount of charge depends on the size of the hearth. You can first use a tube of explosive to try to explode.

●  ​​After blasting the tumor, add sufficient amount of net coke and reduce the load to prevent the furnace from cooling.

●  Since the hearth melts in the furnace, it is easy to cause the hearth to cool down during the rewinding period, and even the hearth freezes, and it is difficult to tap the slag and iron. Therefore, it is necessary to make preparations for the tapping hole.

6. How to deal with the furnace cylinder freezing?

When the furnace temperature drops to the slag iron can not flow out automatically from the slag iron port, the hearth is frozen. The freezing of the hearth is a serious accident in the production of the blast furnace. It takes a great cost to deal with the cylinder freezing, which brings great losses to the production of the blast furnace. Therefore, it is necessary to avoid such accidents as possible. The hearth freezing may occur in the following cases:

●  Continuous material collapse failed to be stopped in time.

●  No coke is added to the long-term low material line.

●  There is error in loading weighing, and the actual coke load is over checked.

●  A large amount of cooling water is leaked into the furnace.

●  The amount of net coke added after the explosion is insufficient, and the melting of the furnace tumor enters the hearth for direct reduction, which causes the temperature of the hearth to decrease sharply.

The treatment is as follows:

●  First, the large halo reduces the air by 20% - 30% or more, so as to ensure the coke in the furnace is slowly burned.

● Try to keep more air outlets working normally. If it is found that the automatic filling is dead, it should be poked in time. At least, the air outlets on both sides of slag iron mouth shall be kept to be able to enter the air.

●  It is hoped that the slag iron can be discharged regularly and one or two air outlets can be obtained by burning the iron port and slag port with oxygen to make the slag iron flow out.

●  When the hearth is frozen, a large amount of coke must be added in time, 10-20 batches can be added at a time, and the coke load is large and the blowing is stopped: the air temperature should be raised to the highest level; Reduce flux and basicity of slag.

●  During the freezing of the furnace hearth, it is necessary to avoid the wind break as far as possible to avoid further deterioration of the furnace condition.

●  If the hearth is seriously frozen and the iron is not produced from the iron port, two or three sets of slag holes can be removed, and the furnace can be built with fire resistance and then the iron can be discharged from the slag mouth.

●  If iron can not be discharged from slag port, the slag port shall be burnt upward with oxygen to connect with the two air outlets adjacent to the upper part. The slag outlet is used to air through two air outlets above the slag mouth to discharge the slag.

●  When the furnace temperature turns to heat, the slag port will be restored to normal operation first, then the air inlet shall be gradually increased, and the iron port shall be burnt with a large amount of oxygen to recover the normal operation of the iron port.

It takes a long time to deal with the hearth sintering, and it can not be achieved quickly. Only by relying on the unremitting efforts of the staff of each post of the BF, can the furnace be restored to normal by melting all the frozen materials in the hearth and discharging them out slowly.

7. How to deal with the emergency power failure of blast furnace?

If the power failure of a transmission line, thunderstorm and electric shock cause an emergency power failure, check whether there is wind at the air outlet and whether there is water in the cold actuator. If the fan is used to stop the wind due to power failure, it shall be treated as sudden wind stop of the fan; If emergency water stop is caused, it shall be treated as emergency stop water immediately; If both wind stop and water stop occur at the same time, the sudden wind stop treatment of fan shall be conducted first, and then emergency water stop treatment shall be carried out.

8. How to prevent the bottom burn through accident?

The bottom state of the hearth is an important factor to determine the life of the first generation of the BF. Therefore, the state of the hearth bottom should be closely followed and the maintenance and monitoring should be strengthened since the BF is put into operation. The burn-through accident at the bottom of the hearth can cause great danger to the production and operation personnel, even cause serious casualties, so as to prevent the occurrence.

There are many reasons for burning through, mainly:

● The bottom structure of the designed hearth is unreasonable, the refractory used is poor, the construction quality is not good, etc. (the 300m3 BF in Beitai);

●  The cooling system in production is unreasonable, the water temperature difference is unstable or high for a long time, especially in the areas with poor water quality, the scaling of water pipe affects the cooling;

●  The raw materials contain lead (the accident of LIANGANG No.4 furnace in July 1989 and March 1997) and alkali metal (June, 1980) which caused great damage to the hearth of furnace bottom;

●  The furnace is in bad condition, and the hearth is often piled up, so fluorite is frequently used to wash the furnace, which causes serious erosion of the hearth;

●  The iron mouth is too shallow for a long time (the accident of Angang 9 furnace in August 1950), the centerline of the iron port is not correct (the accident of No.3 furnace of Anshan Steel in September 1975), and the operation and maintenance are improper.

●  When there is a warning, the measures taken are not effective.

The main signs of burn through are:

●  The temperature difference of cooling wall water or the increase of heat flow intensity of the furnace hearth exceed the specified value or water cut-off;

●  The brick lining in some parts of the hearth is very thin and the shell is red;

●  The bottom cooling of the furnace is abnormal, the air cooling pipe is very red when the air is cold, and gas is emitted in some areas;

●  The iron is abnormal. The iron content increases after slag dropping, even the slag is first seen, and then the molten iron is seen. The iron loss is much each time.

●  Although titanium bearing material has been used to protect the furnace, the effect can not be seen because of the insufficient amount.

According to the causes of burn through, corresponding targeted measures shall be taken to prevent, and the preventive measures are as follows:

●  The reasonable bottom structure of hearth, such as ceramic cup structure, small microporous carbon brick structure, etc., is adopted, and high-quality refractory materials suitable for the bottom working conditions of hearth are selected, and the furnace is constructed carefully;

●  Lead containing charge shall not be used as far as possible, and alkali load of human furnace shall be limited (less than 3kg/t), and slag shall be used to discharge alkali if necessary;

●  Careful operation shall be taken to prevent the stack of the hearth, so as to avoid washing furnace, especially in the middle and later stage of the furnace, fluorite should be avoided;

●  Grasp the operation before the furnace, maintain the normal state of the iron port, and make the slag iron; The speed of molten iron should be controlled to avoid the iron water washing the hearth wall when the speed is too high;

●  Pay close attention to the working state of the cooler, strengthen the scientific management of cooling equipment. When the water temperature difference and heat flow intensity exceed normal, decisive measures shall be taken to restore it to normal, such as changing high-pressure water cooling, single continuous cooling, cleaning cooler, etc;

●  The furnace protection with Ti material shall be effective. The quantity of Ti-containing material shall be ensured to ensure that the content of molten iron reaches 0.08% ～ 0.10%. If the situation is serious, the [Ti] can be increased to 0.15%, and even 0.2% in a short time to save the emergency. After the temperature difference falls, it can be returned;

●  When the heat flow intensity continues to rise, the air outlet in the area with high water temperature difference shall be stopped, the pressure of the area shall be reduced and the slag mouth nearby shall be stopped. If the temperature difference is still higher than the specified limit value, the air cooler shall be stopped. After the water temperature difference drops to the normal value, the cast iron shall be smelted with low-pressure and low smelting strength.

9. How to deal with the fire running and cracking of the furnace body?

In the middle and late stage of BF production, the shell will be deformed or even cracked and the fire will run. If the treatment is not timely or not good, it will cause a big accident. The places where fire is easily run are corrugated pipes connected with the inlet and outlet of cooling wall and furnace shell, and the places easy to crack are the lower part of furnace body, furnace waist and around the iron port of furnace hearth.

The red, cracked and running fire of the furnace indicates that the high-temperature gas has been channeled to the place, and the cause or the lining has been eroded; Or the cooler is burnt; Or the rust joint between coolers has been damaged, and the high-pressure high-temperature gas can be channeled into the expansion joint between the cooling wall and the furnace shell in the gap formed by them. The high-temperature gas heats the cooling wall from the back to accelerate the burning of the cooling wall, and the shell of the heating furnace deforms or cracks at the stress concentration.

The following points should be followed in the treatment:

●  In case of running fire, water shall be immediately started. If no effect is found, change atmospheric pressure, reduce wind and release wind until the wind stops, and stop running fire.

●  Check whether the cooling wall is leaking. Water can be checked by water closing in different sections. If there is any water leakage, water shall be reduced or high-pressure steam shall be supplied as appropriate. If it is found that the wall is leaking, the brick lining in front of the wall will not be cut off as far as possible, or the slag skin can not be formed for self-protection.

●  If the refractory brick lining has been completely damaged, it can be repaired by spraying, and the cooler (replacement or inserting cooling rod, etc.) can be repaired by using this opportunity.

●  Repair welding furnace shell. The repair welding furnace shell should not use the method of attaching a steel plate to the crack. It should be repaired or butt welded after the original seam is processed. It should be noted that when the new steel plate is used for repair welding, the steel grade of the new steel plate and the original furnace shell steel plate should be the same. Welding rods must be matched, and the welding part must be processed into a K shape (because it cannot be processed into an X shape from the inner surface of the furnace shell), and the new steel plate should be heated accordingly when welding.

If the new steel plate is patched and the original cracks are not treated, high-temperature and high-pressure gas will flow between the new steel plate and the furnace shell. Not only will the original cracks continue to increase, but also the blast furnace gas will act on the welds. If the welding quality is not good (two pieces) The steel plate steel grade is different, the welding rod is not matched, etc.), it is more likely to cause the weld to crack, the high pressure and high-temperature gas rush out, the cracks and welds are blown up, and the hot coke runs out, causing major accidents.

If you are interested in the blast furnace, please send your tech requirement to marketing2@hanrm.com, our technical engineers will make the customized solution and quotation for you.