Due to the good mechanical properties and excellent economic and technical value of precision cold-drawn tubes, in economically developed areas, more than 80% of the cylinders use high-precision cold-drawn tubes. The use of high-precision cold-drawn tubes to manufacture cylinders and rollers is the only way for China's hydraulic and pneumatic industry to be in line with international standards. Pay attention to the following points when rolling:
1. Whether the selection of rolling pressure is correct will directly affect the surface roughness, size and precision after rolling. In general, surface roughness increases with increasing rolling pressure. However, when the rolling pressure is increased to a certain extent, the surface roughness will not be improved. If it continues to increase, the rolled surface will deteriorate and even cracks will appear.
2. Rolling is the perfect way to improve the surface roughness of the workpiece. When the pretreatment roughness reaches Ra1.6, as long as the amount of interference is appropriate, the roughness can reach above Ra0.2. However, when the pre-processing roughness is only Ra6.4~ra3.2, and there are vibrations and random tool marks on the machined surface, deep tool marks cannot be rolled, which will only increase interference and re-roll. If the ellipticity and taper of the hole are too large, the above-mentioned defects will still exist after rolling, and the roughness will be relatively large. Therefore, the pre-processed surface should be less than ra3.2, and the geometric accuracy should be greater than grade I and grade II to obtain smaller roughness and ideal precision.
3. This material is soft, malleable and easy to roll. The amount of deformation decreases with decreasing plasticity and increasing hardness. In general, steel and copper roll better than cast iron. Malleable and nodular cast irons roll better than gray cast iron. When rolling cast iron parts, when the material hardness of the casting is not uniform, the defects (pores, sand holes, etc.) on the rolling surface will be exposed immediately. Therefore, the rolling process should not be used when there are many defects on the surface of the casting and the quality is poor.
4. The size of the rolling interference has a great influence on the surface roughness and geometric accuracy. Tests have shown that a very reasonable rolling interference is 0.027-0.036mm, and the surface roughness is very small. Interference is affected by many factors, so the determination of interference should be determined through multiple experiments under specific conditions. Rolling tools usually include balls, cylindrical rollers, tapered rollers, rollers, etc. However, the use of balls as deformation members can reduce the cost of the entire rolling tool. In addition, the steel ball has high precision, high hardness, and a small contact surface with the workpiece. The smaller the rolling pressure, the smaller the interference, and the larger the pressure, the smaller the roughness. Moreover, the ball has a long service life, is not easy to wear, is cheap, and is easy to replace.
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