The cylindricity error of the diameter of the blank before rolling is controlled by the method of grinding the basic data according to the above formula before rolling. The blank does not exceed the length of the blank. The roughness of the outer surface of the blank is not greater than the height of the support H (see Figure 1). Figure 1 is a schematic diagram of the thread rolling according to the recommended formula; where: D is the large diameter of the thread; h is the bearing-to-roller axis distance; a is the height difference between the workpiece axis and the roller axis, recommended value.
The size of a value directly affects the quality of the thread, and it is ideal after processing. At the same time, the strip-shaped hard alloy is inserted on the top of the support piece to increase the wear resistance and strength of the support contact surface, and the central parallelism of the support surface relative to the rolling wheel is controlled within a range, and the support high tolerance is controlled within the range. Before the rolling, the relative position of the rolling wheel is adjusted by the test touch method, and the processing method of the half-pitch of the rolling wheel is determined to ensure that the roughness of the thread reaches the requirement, thereby reducing or eliminating burrs and avoiding disorder. Rolling 1 force and rolling time selection Because rolling is a cold working process, the metal is plastically deformed to form a thread, and the cold hardening phenomenon occurs after rolling, so that the hardness and strength of the thread surface are improved. In particular, the hardness of the base is significantly increased. When the test bolts are heat treated and the hardness is reached, the hardness profile (HB) of the precision bolt thread surface shown in Figure 2 can be obtained. The workpiece material is chrome vanadium steel, and the thread size is M8. It can be seen that after processing The hardness of the thread bottom is about HB600, the heat generated by the rolling is large, and the wear on the rolling wheel is increased. To reduce the heat generated in rolling and improve the life of the rolling wheel, according to the test, the profile of the hardness of the thread surface (HB value) of Figure 2 is the most important thing is to choose a reasonable rolling time, according to the diameter of the thread should be controlled between.
At the same time, because the rolling time is related to the selection of the rolling pressure, in the initial production, only the calculated rolling pressure or the manual is selected. The conventional rolling pressure is used, the rolling time is increased, the heat is generated, and the rolling wheel is seriously damaged. In order to solve this problem, by increasing the rolling pressure and increasing the rolling pressure by one test, the rolling time can be shortened by 23 times until it is increased to 2.5 times the theoretical value. The heat is significantly reduced, the life of the rolling wheel is increased by a factor of three, and the surface roughness of the thread is also improved.
Rolling speed V Rolling speed selection is one of the factors that determine the degree of deformation and deformation speed of the material, which affects the quality of thread processing. It is more reasonable to select the rolling speed through experiments. Feeding amount S Rolling feed amount selection is too large to increase the productivity of the machine tool, but the workpiece is heated, and the roundness, outer diameter, and inner diameter of the thread are rounded. Therefore, when selecting the feed rate, it is necessary to be economical and to consider the machining accuracy. Through experiments, it is considered that Sr is ideal. After using the above process parameters, the thread precision and surface roughness of the rolling can fully meet the technical requirements. Through the actual production in recent years, the qualified rate of thread processing reaches 90%, and the effect is good in the assembly and use of the locomotive.
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