Points to note when rolling high precision cold drawn tubes

- May 06, 2020-

Because high-precision cold-drawn tubes have good mechanical properties and excellent economic and technical value, cylinders used in many countries are manufactured with high-precision cold-drawn tubes. When rolling a high-precision cold-drawn tube, pay attention to the following points:

1. Whether the rolling pressure is selected correctly has an effect on the surface roughness, size and accuracy after rolling. Generally, the rolling pressure increases and the surface roughness increases.

2. Improve the surface roughness of the workpiece, and the effect of rolling processing is better. When the pre-processing roughness reaches Ra1.6, as long as the interference is suitable, the roughness can reach Ra0.2 or more. However, when the pre-processing roughness is only Ra6.4 ~ Ra3.2, and the processing surface has vibration and chaos, then the deeper blades cannot be rolled, which only increases the interference and rolls again.

3. The material is soft and plastic, so it is easy to be rolled. As the plasticity decreases and the hardness increases, the amount of deformation decreases accordingly. Generally, the rolling effect of steel and copper is better, and the effect of cast iron is worse. The rolling effect of malleable iron and ductile iron is better than that of gray cast iron. When rolling cast iron, when the hardness of the material of the casting is not uniform, the defects of the rolled surface will be exposed. Therefore, when the casting surface has more defects and the quality is poor, the rolling process should not be used.

4. The size of the rolling interference has a great influence on the surface roughness and geometric accuracy. The reasonable rolling interference is 0.027 ~ 0.036mm, at this time the surface roughness is small. The amount of interference is affected by many factors, so the amount of interference should be determined by multiple tests based on specific conditions. Rolling tools usually have balls, cylindrical rollers, conical rollers, rollers and so on. However, using balls as deformation members can reduce the cost of the entire rolling tool. In addition, the ball has high precision, high hardness, and small contact surface with the workpiece. With a smaller rolling pressure and a smaller interference, a higher pressure and a smaller roughness can be obtained. Moreover, the ball has a long use time, is not easy to wear, and is cheap and easy to replace.