Regenerative reheating furnace
The heating value of blast furnace gas is low, and the heating capacity is not enough when it is sent directly to the rolling furnace.If the coke oven gas is insufficient, excess blast furnace gas has to be released or burned for nothing, resulting in a waste of energy or air pollution.Regenerative continuous heating furnace is a new technology developed in the United States, Japan, Britain and other countries in the 1990s. It USES high-temperature flue gas to preheat the regenerator in the regenerator first, and then replaces the valve to let the air or gas to be burned into the regenerator to absorb the heat of the regenerator (Figure 1).In this way, the air or combustion gas can be increased by 500 ~ 800℃, and the combustion temperature can be increased to 1300℃, which can meet the needs of billet heating.
Due to the low price of blast furnace gas, a domestic factory with four coke oven gas mixed or mixed with heavy oil heating furnace to regenerative heating furnace, full use of blast furnace gas, heating costs are basically reduced to a quarter of the original, less than two years can be recovered.Its low oxygen combustion and low NOx emission content also reached a good level.The technology can be used in heating furnace and heat treatment furnace.At present, many Chinese iron and steel joint enterprises with blast furnace gas have completed the transformation of regenerator and obtained remarkable benefits.
2. Strong cooling of suspension
Due to the high final rolling temperature, high temperature of spinning wire rod or cold bed wire rod, plus speed up, the original cooling capacity is not enough has been one of the problems that troubles the rod mill.It is a great breakthrough in cooling theory that the strong cooling technology of suspension makes use of the destruction of the steam film caused by heavy weight suspended turbidity.The water penetration device of bar suspension, which is jointly completed by Hebei University of Science and Technology and Xuangang No.2 Rolling Co., LTD., has been proved by production practice that the cooling effect is very remarkable.A new nozzle device is designed in this system. The suspension circulating system is unobstructed and reliable after nearly two years' operation.The success of this technique provides an effective method for solving high spinning temperature, insufficient cold bed capacity, and improving mechanical properties and pass rate of products.
The rod suspension in water device don't have to lengthen the original water cooling section, just add a small reservoirs, cooling water through the filter and recycle, so it is existing in the implementation of workplace rolling and cooling, with low temperature rapid cooling after finishing, or finishing, greatly improve the product of the mechanical performance index of the feasible cooling technology.
3 Flat blank broadening rolled narrow band
Many medium and narrow strip mills use continuous casting billets with the same width and size.Sometimes there is a surplus of roll width, so there is a need to roll a wider strip with a narrow strip.For this reason, by using the forced wide opening pass with the characteristic of cutting depth, the medium blank of the wider strip can be rolled out, and the wider strip can be rolled out by finishing rolling, which can better meet the market demand.The common ways of rolling the width of narrow billet are cutting and butterfly bending.The former makes use of the metal with less elongation in the rolling deformation zone to obstruct the elongation of other metals after the uneven deformation is pressed down, resulting in forced width. At present, the strip with a width of 16 times wider than the blank can be produced.
Round steel positioning caliper
It is the hope of many rod mills to measure the line size, adjust the roll gap and enlarge the proportion of high precision products.The imported rotary scanning caliper can be used to measure on line the outer edge of the entire convex profile of the rolling piece moving at high speed, but it costs millions of yuan and the large length of the whole machine takes up a lot of space in the existing water-cooled section with very limited length.In fact, the production of round bar line mainly grasp the height of the rolling piece and the ear at the roll gap. If the measuring instrument can be placed still, it can be greatly simplified.The 8-point fixed measuring diameter produced by Tianjin Zhaorui measurement and Control Company can measure the size of rolled piece in motion with a non-rotating fixed probe, which can reflect the main dimensions such as height and width, although it does not continuously reflect the changes around the rolled piece.In particular, the width of the instrument is less than 300mm, placed on the rail car, it is very convenient to enter or exit the rolling line, suitable for the field use of the finishing rolling exit water cooling section is short.After several years of use on site, it is proved that the purging system is reasonable and the light source life is much longer than the imported rotary caliper, while the price is only one sixth of the imported instrument.
Replace bakelite bearing with rolling bearing
Bakelwood bearing bush is a kind of old sliding bearing bush used for a long time, although the price is cheap, but the rigidity is small, wear fast, when the temperature fluctuation is large, easy to appear rolled piece size fluctuation.To this end, a workshop will be three high 400 rolling mill instead of a sealed rolling bearing.After a period of use, the results are good.Roughing billet with size fluctuation in the front three high mill is also controlled here, which greatly reduces the subsequent accidents, plays a significant role in ensuring production and improving product size accuracy, and also significantly reduces water consumption.
6 arc teeth to replace the plum sleeve
Plum flower sleeve transmission is a very old transmission roller way, it is not uniform in the moment of transmission, because of the dead weight rotation often has the suspension falling process, causing greater noise, but also has an impact on the accuracy of the product, serious light and dark alternate stripes.This is because the connecting rod must have a considerable amount of space between the plum and the sleeve in order to be able to tilt.Therefore, when transferring torque, the dead weight and inclination Angle of the connecting rod make the sleeve bear uneven force.During loading, the force point of the plum petal is easy to change, especially after the wear of the old sleeve, resulting in uneven upper and lower torques, roll slip.Therefore, replacing the plum sleeve with a curved tooth or other hand can reduce the number of spare parts, improve the quality of the operating environment, and bring convenience to the production and maintenance. All the investment will be recovered in half a year.
7 Induction heating
Direct rolling is the most ideal technology for energy saving, but when the continuous casting billet comes out of the mold and passes through the bending water-cooling section, the general corner temperature is already too low, and the caster is far away from the mill, the overall temperature also drops a lot, so the corner needs to be heated up.Electric induction heating has the advantages of less floor space, faster heating, no need to store energy, etc. Some domestic manufacturers have installed this kind of equipment, but did not achieve the desired effect.The main reason is that the selection of induction heating efficiency is too high, resulting in the billet heating far below the actual needs, so the billet can not meet the general requirements of rolling temperature.However, this technology is not uncommon abroad. Yingsteel USES Radyne's 10MW pipe induction heating system, which can rapidly heat pipes with an outer diameter of 168mm from 700℃ to 1100℃.There are 6 solid state heaters in this device, each with output power of 1650kW and frequency of 1kHz, and the moving speed of pipe is 1 7m/s, which is much higher than the speed of 0 3m/s of general continuous rolling billet roughing mill.
Radyne's induction heating coefficient design is 20% higher than it needs to be, leaving a substantial margin and allowing you to increase the rolling speed at will.The design of this system has reference value for domestic design. In the design of 165mm square billet by induction heating, the characteristics of corner vortex efficiency and solid core should also be considered, and the power should be no less than 10MW.
Thickness gauge and convexity control
Lack many of the hot rolled narrow strip steel workshop online thickness measurement device, the thickness of the products rely on artificial periodically, difficult to measure in time, not to mention the thickness control the thickness of the product size are volatile, even some cold rolled material supply some of the broadband in the workshop is only equipment center thickness gauge, crown cannot detect products, customers can not get smaller crown and a constant cold rolled material.On the one hand, it is due to the danger of X-ray thickness measurement, which is unwilling to be used on site; on the other hand, it is expensive (hundreds of thousands of yuan for one set), and the device protection system is complex.
It was once thought that only 800mm broadband can be installed to detect the convexity, but in fact, the 500mm broadband on site has been measured in 3-point form to directly learn the plate convexity, which can provide a reference for the control of the convexity of medium and wide strip steel, which is of great significance for the stability of product quality.
The emergence of laser thickness and width measuring instrument for hot rolling has brought convenience to steel rolling production.The laser hit on the red steel plate has a special spot, through the triangulation optical transformation, by the photoelectric coupler converted into an electrical signal.This signal, combined with computer recognition technology, can be used to determine the location of laser spots and thus measure the thickness of the strip.At present, laser thickness measurement accuracy is not as good as ray thickness measurement, but the relative thickness of steel plate cross-section can be compared.
High precision control of plate and strip hydraulic thickness
Due to the slow motion and poor accuracy of electric pressure, it is not suitable for fast adjustment online.Generally, the response speed of hydraulic cylinder is 6 times higher than that of electric pressing, and the precision is also much higher than that of electric pressing screw.The pM-AGC fast roll gap adjustment can be realized by installing hydraulic cylinder in the finished stand of strip finishing mill.The feedforward control of the pressure gauge can be realized if it is matched with the pressure sensor of the finished front shelf.If the thickness gauge is installed at the exit of the finished frame, the feedback control of the thickness gauge can be realized, which will compensate the influence of head and tail temperature difference caused by long rolling, greatly reduce the thickness deviation fluctuation of the whole strip, and ensure the product accuracy.A 3 m laser thickness gauge manufactured by Zhengzhou Optical Research Institute was used to monitor the thickness of the product in a factory, and the hydraulic monitoring AGC system was formed in conjunction with the computer and the hydraulic roller joint adjustment device to reduce the size fluctuation of the thickness of the strip head and tail.In the past, the head and tail thickness difference of plate was nearly 40 m. After using hydraulic pressure feedback AGC or thickness gauge to monitor AGC, the head and tail thickness difference decreased by more than 10 microns despite the increase of single weight and longer rolling time, which further improved the market competitiveness of the product.
Hydraulic AGC thickness control is also used in the old four - high plate mill.
No looped microtension rolling
The looper support is used to reflect the tension level between the frames, but it consumes a lot of energy when the thick billet is rolled, and it is not fast enough when the finished frame is rolled.Therefore, some foreign manufacturers successfully developed rolling without looper, without looper support.In the first place, the rolling speed and the stable tension should be accurately calculated, and the increment speed of dynamic drop should be compensated.In foreign countries, looping rolling is mainly based on current memory method, observer is established, and appropriate formula of moment arm coefficient is selected to calculate the tension, according to which the tension is controlled.
The actual continuous rolling tension mainly depends on the inlet and outlet speed difference of the front and rear mills during free rolling, and is also related to the influence of motor driving ability and tension on the front and rear sliding.The practical model of tension calculation is presented in the literature, which makes the calculation of continuous rolling parameters simple and intuitive.This formula can be used to calculate the rough rolling tension not only for strip but also for wire rod.
Hot rolling injection lubrication
Lubrication in hot continuous rolling process can reduce friction force and torque, reduce roll wear and improve surface quality.This technology is widely used in advanced industrial countries to reduce energy consumption and roll consumption.The greater the pressure, the more significant the lubrication effect.The friction coefficient can be reduced from 0.35 to 0.12, and the rolling force and roll consumption can be reduced by 20%.The application of hot rolling lubrication will make the friction coefficient set by the control system of hot rolling change greatly, but generally it is still within the range of "tension self-adjustment", and the distribution of rolling force also changes slightly.
Hot rolling injection requires a dedicated oil pump station, as well as a high-precision control valve for starting and stopping.It is required that the lubricating oil has good adhesion after being ejected and has a high cracking point at 600℃.In addition, attention should be paid to spray limit, to ensure that after rolling combustion.This technology can also be extended to section steel rolling, but pay attention to the uniform injection not excessive.
