Some considerations for rolling tube rolling
(1) The material is soft and plastic, and it is easy to be rolled. As the plasticity decreases and the hardness increases, the amount of deformation decreases. Generally, steel and copper are rolled better, and cast iron is poor. Wrought iron, ductile iron is better than gray cast iron. When the cast iron piece is rolled, when the material hardness of the casting is not uniform, the defects (pores, blisters, etc.) of the rolled surface are revealed. Therefore, when the surface of the casting is lacking in color and the quality is poor, the rolling process should not be used. The amount of rolling interference has a great influence on surface roughness and geometric accuracy.
(2) Whether the selection of rolling pressure is correct or not, it has an effect on surface roughness, size and precision after rolling. In general, the rolling pressure increases and the surface roughness increases. However, the rolling pressure is increased to some extent and the surface roughness does not continue to increase. If it continues to increase, the rolling surface begins to deteriorate and cracks may occur. Increasing the surface roughness of the workpiece is better by rolling. When the pre-machining roughness reaches Ra1.6, the roughness can reach Ra0.2 or more as long as the interference is suitable. However, when the pre-machining roughness is only Ra6.4 to Ra3.2, and the machined surface has a chaotic pattern of vibration, the deeper blade cannot be rolled, which only increases the interference and rolls again. If the ellipticity and taper of the hole are too large, the above defects still exist after rolling, and the roughness is large. Therefore, the pre-machined surface is as small as Ra3.2, which can achieve small roughness and better precision.
(3) The rolling speed has little effect on the surface roughness, so we can increase the speed of rolling to increase production efficiency. The number of rolling should not be too much. The amount of feed should be determined by the diameter of the ball. The smaller the feed amount, the smaller the surface roughness. The feed rate should be determined by experiment. Rolling tools usually have balls, cylindrical rollers, conical rollers, rollers, and the like. However, the use of balls as deforming members reduces the cost of the entire rolling tool. Moreover, the ball has high precision, high hardness, and small contact surface with the workpiece. With a small rolling pressure, a small interference can obtain a higher pressure and a smaller roughness. Moreover, the ball has a long service life, is not easy to wear, and is cheap and easy to change.