The world No. 1 in crude steel production steel plant, over 70% of the HSS for bar and wire are from us.

YUAN HUI
YUAN HUI
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High speed steel rolls (hss rolls)processing and application

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Aiming at the problems of difficulty in processing high-speed steel rolls and low processing efficiency, this article elaborates on the characteristics of high-speed steel rolls, tool materials, machine tool performance, processing technology and use. The influence of factors such as tool selection, processing technology, machine tool requirements and roll use on the application of high-speed steel rolls is clarified.

Keywords: high-speed steel rolls processing, hss rolls application

In the mid-1990s, China took the lead in successfully developing centrifugally cast high-speed steel rolls and successfully applied them to hot-rolling narrow-strip steel mills, and subsequently to bar mills, high-speed wire rod mills and spring flat steel mills.

This technology was awarded a national invention patent in 2001, and the centrifugally cast high-speed steel roller ring developed in 2005 was also awarded a national invention patent.

The high-speed steel rolls and roll rings produced by the company have formed a series of products with multiple specifications and varieties.

In 2001, the company successfully developed large-scale centrifugally cast high-speed steel rolls, which were successfully used in continuous casting, continuous rolling, and hot continuous rolling production lines. The large-scale centrifugally cast high-speed steel rolls successfully developed by the company in 2005 have also been successfully used in hot continuous rolling production lines, and have achieved good results.

As a rising star, LMM Roll Manufacturing Factory has been concentrating on the research and production of high standards and high materials. As a processing technician, it has explored and experimented with the processing technology and processing tools of high-speed steel rolls.

features and Management Requirements of rolling mill Rolls in Plate Mills

Main features of high speed steel rolls

High-speed steel roll materials contain high amounts of vanadium, molybdenum, tungsten, chromium and other alloying elements. Therefore, the main types of carbides in the roll structure are MC type and M2C type. The carbides have high hardness and good wear resistance; they have a relatively high Good thermal stability. When rolling is stable, the roll surface has high hardness and good wear resistance; high-speed steel rolls have good hardenability, and the hardness almost does not drop from the roll surface to the inside of the working layer, thus ensuring This ensures that the roll has equally good wear resistance from the outside to the inside; during use of the high-speed steel roll, under good cooling conditions, a thin and dense oxide film is formed on the surface of the roll body. This uniform, thin and dense oxide film It can exist for a long time without falling off, which significantly improves the wear resistance of high-speed steel rolls; the high-speed steel roll material has a large expansion coefficient and good thermal conductivity. While the roll wears slightly along with the rolling groove during the rolling process, due to the high-speed steel material Its own expansion makes the pass shape continue to become smaller. Therefore, the rolling groove of the high-speed steel roll does not change much during the rolling process, and the consistency of the pass size is maintained for a long time, which is conducive to controlling the negative deviation rolling of the rolled material.

High speed steel roll processing technology

Tool material selection

The cutting part of the tool is in direct contact with the roll and is subjected to great cutting pressure and impact. It also rubs violently with the roll under high temperature and high pressure, and the working conditions are very harsh. High-speed steel roll processing tools usually use super-hard materials such as diamond and cubic boron nitride (CBN). The cutting speed is 10 to 20 times higher than ordinary carbide tools, and the processing surface roughness is very small. . CBN cutting tools have higher hardness, thermal stability and chemical inertness than diamond, as well as good infrared transmission and wide bandgap and other excellent properties.

Cubic boron nitride (CBN) is second only to diamond and has high hardness and wear resistance. It is currently the first choice material for high-speed steel roll processing tools in steel rolling companies. At present, there are two types of CBN tool synthesis: polycrystalline wafers (synthesized from CBN and binder) and composite wafers (synthesized from CBN and binder on cemented carbide sheets). In the processing of high-speed steel rolls, cermet binders and ultra-fine grain CBN materials are often used, and the commonly used brands are MBN3500 and MBN5000. Practice has also proven that these two grades of CBN material tools are the best choice for processing high-speed steel rolls.

High-speed steel roll processing technology optimization

Taking high-speed steel grooving rollers as an example, due to the large amount of rough machining of new rolls with grooves, the tools wear quickly and have short lifespans. Therefore, a blade slightly smaller than the diameter of the base circle of the pass is generally used to cut out the groove shape on the roll body. Then use CBN tools to cycle through the CNC machining program. The cutting amount adopts different parameters according to the different parts of the machining hole pattern. Generally, the cutting depth is selected as 0.3mm~0.4mm, the cutting speed is 60m/min~80m/min, the feed amount is set as needed in the processing program, the roller ring part is about 0.8mm/r, and the hole groove arc part 0.3mm/r~0.5mm/r, the bottom of the hole groove (large arc of base circle) is 0.3mm/r~0.4mm/r, for finishing.

By adjusting the parameters of the CNC roll special lathe CK84100, the rotation speed during processing was increased several times after optimization, which greatly shortened the processing time of high-speed steel rolls on the lathe and improved the processing efficiency of high-speed steel rolls. Originally, an arc-shaped pass cutter was used for chamfering, but the surface of the high-speed steel roll often collapsed and the chamfering depth was not enough. To this end, the pass processing technology is optimized: first, a pointed cylindrical tool is used to rough process the chamfer part, and then an arc tool is used to fine process the pass part, which solves this problem better. The finished pass is mainly processed with a CNC lathe in one go. Because the finished pass has a strong impact on the blade, the CNC blade collapses. To this end, the following optimization is carried out: first use a carbide turning tool to rough-turn the pass shape of the high-speed steel roll on an ordinary lathe; then put it on a CNC lathe for cylindrical finishing. This solves the problem better and at the same time ensures the smoothness of the base circle of the finished hole pattern.

Application of high-speed steel rolls

The application of high-speed steel rolls is an important part of the development of modern steel rolling production. It is another major change in the development of the steel industry after microalloying and controlled rolling and cooling technology. High-speed steel rolls have been widely used in steel rolling production in the fields of plates, sections, bars and wire rods in Japan, not only for work rolls, but also for support rolls. The good wear resistance of high-speed steel rolls is inseparable from its characteristics that are obviously different from traditional rolls.

Use of high-speed steel rolls

During the use of high-speed steel rolls, the cooling of the roll body requires the use of clean, low-temperature water, which must ensure both water pressure and water quantity. This avoids thermal cracks in the roll body caused by overheating, and the expansion of thermal cracks causing the roll body to peel off. It also reduces the phase change in the roll body structure caused by excessive temperature of the roll body. The ideal cooling system is to have multiple nozzles distributed in an annular shape on the roller body to ensure continuous and sufficient water flow to the contact surface. Generally, the water temperature does not exceed 40℃, the water pressure is controlled at 0.4MPA~0.6MPA, and the water volume is not less than 300L/min~500L/min. Ensure that 70%~80% of the water volume is on the outlet side, and the water flow should be aimed at the rolling surface. Avoid scattering. In addition, high-speed steel rolls have high sensitivity to hot cracking. Before the roll comes into contact with red steel, the cooling water needs to be turned on in advance to cool the roll body. When steel jamming or pile-up occurs, water cooling should be continued to allow the temperature of the rolled material and rolls to cool down before the water is stopped, and the rolled pieces accumulated in the rolling groove should be removed.

Effect of using high-speed steel rollers

After using high-speed steel rolls, the number of roll replacements on the machine is reduced, time is saved, and the rolling mill operation rate and output are improved. The surface quality of the rolled material is good. High-speed steel rolls have relatively high hardness, which can effectively resist corrosion on the roll surface during the rolling process, reducing the occurrence of pitting, improving the surface quality of rolled materials, and improving market competitiveness.

Conclusion

High-speed steel rolls have high hardness and wear resistance. Under the same rolling conditions, compared with chilled cast iron rolls and high-nickel-chromium composite cast iron rolls, the wear amount is smaller, and the single-groove rolling volume is doubled. It can greatly improve the surface quality of steel and effectively control the negative dimensional accuracy. The advantages of the online bar unit have become increasingly prominent. However, the material of high-speed steel roll processing tools is a major bottleneck restricting its development. With the continuous upgrading of CBN tool materials, through reasonable processing technology, and when the machine tool rigidity meets the processing conditions, the processing difficulty will gradually decrease, the processing efficiency will be further improved, and the cooling method of high-speed steel rolls will also be improved. To this end, the promotion and application of high-speed steel rolls has broad prospects, which will definitely bring the advantages of high-speed steel rolls to the extreme and promote another leap forward in steel rolling production equipment.

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Rolling mill rolls product

Classification by roll material:

Cast iron mill rolls

  • Alloy indefinite chilled cast iron rolls
  • Alloy chilled cast iron rolls
  • Alloy SG ductile cast iron roll
  • Pearlitic ductile cast iron roll
  • Bainite ductile cast iron roll
  • Centrifugal cast iron roll


Cast steel mill rolls   

  • Alloy cast steel rolls
  • Semi-steel roller
  • Graphite steel rolls
  • High-chromium steel roll
  • High-speed steel roll


Forging mill rolls

Sort by position on the rolling mill:

Work rolls
backup rolls

Intermediate roll

Product advantage

The world No. 1 in crude steel production steel plant, over 70% of the HSS for bar and wire are from us.

LMM high-speed steel rolls have higher steel passing per groove (times) due to their good wear resistance, which saves roll changing time, improves rolling mill operation rate, reduces roll consumption, and improve the overall efficiency of the factory.
Generally, the amount of steel passing in a single groove (times) is 3 to 5 times that of cast iron rolls.

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