Study on Control Technology of NM360 Steel\'s On-line Quenching Plate Shape
Keywords: Quenching plate shape control technology, NM360 steel, pre-process, post-process, on-line quenching.
Introduction
NM360 steel is a medium-strength steel produced by normalizing and tempered hot rolling process. It is widely used in the fields of construction, pipelines, ships and other forged parts. Compared with the cold-rolled NM360 steel with high strength, the hot-rolled steel has some disadvantages, such as low cold bending performance, large internal stress and low impact toughness. Therefore, it is necessary to control the shape of steel in quenching to meet the engineering and processing requirements.
Quenching plate shape control technology
Quenching plate shape control technology is divided into pre-process and post-process. The pre-process is about pre-forming the steel into the required shape, and the post-process is about the quenching medium directing and the quenching temperature controlling respectively.
Pre-process
In order to form the required shape of steel, a high-accuracy die with rigid structure is preferred. The main parameters which affect the forming accuracy of the die are blank-holding pressure, slide frequency and stroke pressure. To ensure good plate shape, the parameters should be properly adjusted according to the material and the die size. The die should also be relatively easy to maintain and troubleshoot.
Post-process
Quenching medium: In quenching process, medium material and heat transfer mode are two important aspects. Considering the requirements of production and heat transfer, a small particle medium with a particle size of 50-300mm is preferred, such as iron sand, iron chips or quartz sand.
Quenching temperature: The quenching temperature of steel plate is related to the material, plate size and other parameters, which should be adjusted according to different materials and plate size. The quenching temperature should be controlled in the range of 850-900 ° C, suitable for different materials.
Experimental Study
To verify the quenching process of NM360 steel, experiments are conducted to study the effects of temperature, speed and other parameters on the plate shape.
Quenching stability tests: Quenching stability test is conducted to study the effect of quenching on the accuracy of the steel plate. The experiments are conducted at different quenching temperatures and speeds. The differences between the two plates indicate how much the quenching can deform the plate.
Wear tests: Wear tests are conducted to study the effect of quenching on the wearability of the steel plate. Quenching is usually used for wear-resisting parts. The wear resistance of the steel plate can be measured by measuring the wear rate of the steel plate at different temperatures and speeds.
Fatigue tests: Fatigue tests are conducted to study the effect of quenching on the fatigue strength of the steel plate. Low temperature quenching can increase the fatigue strength of the steel plate, while high temperature quenching can reduce the fatigue strength.
Conclusion
Based on the experiments, the quenching plate shape of NM360 steel meets the requirements of the technical specification and meets the requirements of the workpiece shape. The pre-process of die equipment shape as well as the post-process of on-line quenching temperature control can effectively ensure the quenching accuracy of NM360 steel.
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