Analysis of heat treatment technology of Hi-Mn casting liners (2)
( Yue Weiguo, Yuan Fang, Liu Jincang)
Citic Heavy Industry Luoyang Heavy Iron Industry Co. Ltd.
2.Difference of preheating and heat preservation methods for large, medium and small size liners
- Big and medium size of the liners
It is essential to preheat and even temperature operation of the lining plate, directly related to the toughness of the lining plate. The quenching process includes expanding preheating and homogenizing. In this process, the influence of thermal stress and microstructure stress should be considered. This two types of lining plate preheating temperature should be taken above 650-700 °c ACI temperature, at this stage, the relevant personnel need to delay the appropriate insulation time, in order to reduce the two types of stress produced by the lining board, so that the lining plate plastic increase. The quenching temperature is 1100 °C, and the time from preheating and heat preservation to quenching temperature are short. When the quenching temperature is reached, the quenching operation needs to be completed in proper holding time, which can ensure the wear resistance of the product.
- The small size of the liners
This kind of lining plate preheating and heat preservation method is more, the related personnel needs to satisfy the rapid rise, the temperature quenching condition, need to control the heat preservation time, cause it to obtain the extension in the reasonable scope, so the lining plate’s plasticity and the yield ability will be strengthened.
3.Secondary dispersion solid solution treatment process for large, medium and small size liner
The secondary dispersion reliable solvent treatment of liner mainly refers to water toughening treatment and aging treatment. To keep the replacement frequency of the three kinds of lining plates synchronized, the related personnel needs to pass the heat treatment process, to extend the life of large and medium-sized liners. The thickness of the three types of lining board will affect the service time, so the thickness adjustment can be used to achieve the goal. The thickness of large and medium-size liners should be increased to 120mm, and the time of water toughening treatment and aging treatment should be prolonged at the same time.
In the optimal aging treatment, the related personnel, need to heat the quenched steel piece to keep it at 350 °C for 8 hours, and then do the cold treatment. The process mainly deals with the dissolved carbon, after it becomes carbide, it will be separated from the original lining plate, so the Brittleness and crack sensitivity of the steel lining plate will be reduced, and the second phase of the lining plate will be strengthened.
In the secondary dispersion solution treatment of steel liner, the related personnel needs to control the aging time and avoid the averaging phenomenon. Otherwise, the performance of the steel lining board will not improve but will reduce.
4.Optimization of lining plate and heat treatment of high manganese steel with chromium
There are many elements in the high manganese steel liner, and the heat treatment process will be changed when chromium is added. After water toughening, the steel lining plate’s temperature needs to be kept below 400 °C but can be raised to 350 °C. So in its installation in the relevant equipment, the relevant personnel also need to pay attention to the lining board cutting way to avoid cutting heating phenomena. In the installation, mainly avoid the use of oxygen gun heating cutting mode.
In practical installation applications, when some panels need to be replaced, the person concerned need to handle the panels in the form of large chamfered panels, rather than cutting the edges of the panels at will, thus, the problem of tempering and heating up of the lining plate after water toughening treatment will not occur. Controlling the installation and installation of the grid plate can reduce the crack phenomenon of the grid plate.
The chromium-added High Manganese Steel Lining plate is more wear-resistant than the High Manganese Steel Lining plate. It has many advantages in toughness and yield limit, so this material will gradually replace the High Manganese Steel Lining plate. The heat treatment process is more demanding. If something goes wrong, the carbide from the steel lining plate’s surface will be redissolved in the steel liners, so the Steel Liner’s performance will be rapidly reduced in the application. To solve this problem, the control of heating rate should be done well, the low-temperature heating rate should be less than 50 °C/h, and the holding temperature should be not less than 650 °C, but also not more than 700 °C
In the production and processing of high manganese steel liners, heat treatment is a vital link directly related to the performance of the product. The heat treatment process involves many processes, and many parameters need to be controlled, so the treatment process is prone to problems. The relevant personnel should also focus on solving these problems not to affect the processing of the high manganese steel lining plate mass. Besides, the appropriate staff should also improve the heat treatment process to enhance the treatment program.
(This article is chosen from Science and Wealth, only translated for study. )