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Home » FAQs » Comparison and analysis of final heat treatment process for four kinds of Forged Steel Backup Rolls
Comparison and analysis of final heat treatment process for four kinds of Forged Steel Backup Rolls
2017-06-17 15:46:44

 The forged steel backup roller is the core component of modern steel rolling equipment, which mainly bears the rolling load of the work roll or intermediate roll. With large product specifications and high technical content, its performance directly determines the stability of the rolling mill, the direct production line and the quality of the products.

At present, the main production process of forging steel supporting roller in the final heat treatment refers to heat treatment of quenching and tempering on the surface of roller body parts, it is the key process of supporting roller working layer microstructure, hardness distribution, stress distribution and performance, but also the core of the manufacturing technology of supporting roller. Therefore, a great deal of attention has been paid to the research of the final heat treatment technology of the forged steel support roller at home and abroad.
The final heat treatment technology of forging steel supporting roller are mainly in the following 4 ways: trolley furnace or well furnace through heating quenching technology, continuous induction heating quenching technology, differential temperature furnace heating quenching technology and static low-frequency integral induction heating quenching technology. These 4 kinds of methods for different products and different users are in use, the temperature difference between the furnace heating and quenching technology in China and the most widely used and most advanced static low-frequency integral induction heating quenching technology at present in China is not reported, the world's only a few enterprises in japan. But the forged steel backup roller produced by this technology is well used in Baosteel mill.
Evolving ultimate heat treatment technology
Heating and quenching technology for trolley furnace or well furnace. Don't burn the whole heating quenching technology is the use of ordinary trolley or vertical furnace, the preheating furnace roll with rapid heating, fast temperature will rise to quenching temperature above 20 to 50 DEG C range, to the surface of the roller body temperature display to quenching temperature after heat insulation, heat preservation time for austenitic layer control in depth, and then burn through before released reach differential temperature quenching, quenching effect. Using this process, the supporting roller neck in a furnace, and through heating, equal to a strengthening, so in the roll body spray quenching followed when the roll neck to take protective measures to avoid hardening after tempering, the whole body roll roll neck at the same time, to meet the different requirements of hardness.
Continuous induction heating quenching technology. The continuous induction heating quenching technology of backup roller means quenching technology that the supporting roller is preheated in the trolley furnace and then lifted into the induction coil for heating and cooling at the same time. This is similar to a technology and production work roll and intermediate roll, the induction coil used for induction coil height is low, so the induction coil heating area is small, short heating time, the austenite layer depth is shallow; although there are water cooling ability, can make the surface of high hardness, but after quenching. The depth of hardened layer is shallow. In addition, when the backup roller is produced by the quenching technique, the roll neck can not be specially protected. At present, for some small depth (less than 40mm) of the supporting roller, continuous induction heating quenching technology was used in the absence of temperature difference between the furnace and the whole induction heating equipment production enterprises.
Heating quenching technique of differential furnace. Differential temperature quenching furnace heating technology refers to the trolley furnace heated roller body placed in a special open type differential temperature furnace, combustion gas or natural gas is used as heat source, on the surface of the roller body for rapid heating by high speed burner flames, causing the roll body temperature difference between inside and outside, the body surface to obtain a certain the depth of the austenite layer while the core region remains at the transition point below the surface of the cooling heat treatment method. The Chavinge process was originally developed in the United States in the 70s of the last century, and the special heat treatment furnace is an open and close type gas furnace. Later, this kind of process and equipment were adopted by many roller manufacturers in the world, and became the main form of heat treatment for backup roller. At present, it is the mainstream of domestic production of this kind of roller. Each roller manufacturer has propane gas, natural gas and producer gas according to its specific conditions, and the effect is better with a high calorific value. The main characteristics of differential temperature heating furnace is used in high speed burner can make the temperature heating rate reaches more than 200 DEG C for /h, supporting roller surface can be rapidly warming, in order to achieve good effect of temperature difference. The quenching mode of the differential furnace after heating is oil quenching, water quenching, oil cooling and spray cooling. In these cooling methods, the spray cooling is the most important, and the cooling intensity can be adjusted flexibly by adjusting the air pressure and water pressure. At present, the domestic large support roller manufacturers have adopted the production process, can obtain bainite based roll microstructure, hardness of roll body control in 55 ~ 71HSD, the depth of hardened layer is less than 90mm, hardness of roll body surface uniformity is controlled within 2 ~ 3HSD.
Low frequency static whole induction heating quenching technology. The low frequency static integral induction heating quenching technology is to use the low-frequency induction coil to carry on the whole heating to the surface of the support roll body, then to spray cooling quenching method. The technology is the last century in Japan in 80s by Hitachi (HITACHI) first application development, followed by Japan Steel Casting (JCFC) and Japan Steel (JSW) and other companies have carried out technological transformation, promotion and application of this method, which represents the advanced level of support and final heat treatment technology. Using the technology of production of forged steel supporting roller is to improve the surface hardness and roller body increase the hardness of body surface hardening layer depth and roll uniform effective method, compared with the differential temperature quenching process with high heating efficiency, good temperature, poor effect, high surface hardness of roll body hardened depth, consumption etc. The advantage of less energy.

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