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What needs to be done for cold roll production and processing?
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Cold roll production and processingWhat needs to be done?
Cold roll production and processing requires quenching and tempering. The purpose of quenching and tempering is to first process the roll core and roll neck to the required strength and hardness, and to prepare for the quenching of the roll body. If the strength requirement is not high, it can also be directly quenched without quenching and tempering. Oil cooling or spray cooling is used during tempering. Spray cooling can deepen the quenching and tempering depth of the roll.
Cold roll production and processing: quenching is an important heat treatment process for cold roll production and processing. In the early stages, the overall heating and quenching method is used after the roll neck is jacketed. With the development of heating technology, medium frequency or power frequency induction heating is mostly used. This induction heating can be single or dual frequency, and can be integral or mobile. Flames can also be used to achieve rapid heating. High-pressure water should be used for quenching and cooling, and cooling should continue for a certain period of time after quenching. Timely low-temperature tempering after quenching. For rolls with very low residual austenite content, it is necessary to add a cold treatment procedure before tempering. When a cold roll with a center hole is quenched, the hole should also be filled with water to accelerate the heat dissipation of the core.
Roughing shall beCold roll production and processingThe billet is annealed after. In order to reduce the risk of quenching cracks, cold rolls are usually designed with a central hole. At this time, attention should be paid to the processing quality of the center hole surface to avoid damage due to the fatigue of the center hole during use. If the hydrogen content and residual stress are properly controlled, no central hole will be left. The machining allowance should be considered in this way; no decarburized layer should be left on the product; no defects that are not conducive to quenching should be left; do not leave too much machining allowance during finishing; the amount of grinding after quenching should be as small as possible. Finishing and grinding shall be carried out before and after quenching. Cold rolls have high requirements for dimensional accuracy, concentricity and roughness. In addition, the residual stress of the quenching roller is very high, so the grinding wheel and grinding parameters should be carefully selected to avoid grinding cracks. Roll processing should use special machine tools, try to use CNC machine tools.
Cold roll production and processing: In addition to the regular material inspection, the cold roll should also pass a series of product inspection items. The inspection of machining accuracy should be carried out in accordance with the regular method. Roll hardness measurement includes three indicators, namely hardness (average hardness), hardness uniformity and hardness distribution with depth. regular tests refer to the first two. When using a Shore hardness tester to measure the hardness of the roll, the specified test conditions should be followed, especially the number of measuring points, the number of measurements at each point, the calculation method of average value and uniformity. When other types of hardness meters are used for measurement, the hardness conversion table used should be specified in advance. Non-destructive testing of rolls is usually carried out by ultrasonic flaw detectors. In the cold roll flaw detection standard, the roll body is usually divided into surface area, central area and intermediate area according to the stress state, and then the critical size of allowable defects in each area is specified according to the principle of fracture mechanics. Flaw inspectors should have knowledge of roll manufacture to determine the nature of defects and should also understand the use of rolls to estimate whether these defects will cause service damage under specific conditions of use.
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