1. The chemical composition and mechanical properties o […]
1. The chemical composition and mechanical properties of raw materials for cold heading of cold head screw machine should meet the relevant standards of multi-station automatic cold heading machine.
2. The raw materials must be spheroidized and annealed. The metallographic structure of the material is spherical pearlite 4-6.
3. The hardness of the raw material, in order to reduce the material's cracking tendency as much as possible, and to increase the service life of the mold, it is also required that the cold drawn material has the lowest possible hardness to improve the plasticity. The hardness of raw materials is generally required to be HB110 ~ 170 (HRB62-88).
4. The precision of cold-drawn material should generally be determined according to the specific requirements of the product and the process conditions. In general, multi-station cold heading machines have lower requirements for diameter reduction and strong shrinking dimensional accuracy.
5. The surface quality of the cold drawn material requires that the lubricating film is dull and dark, and at the same time, the surface must not have scratches, folds, cracks, roughening, rust, oxide scale and pits and pits.
6. It is required that the total thickness of the decarburized layer in the radial direction of the cold drawn material does not exceed 1-1.5% of the diameter of the raw material (the specific situation depends on the requirements of each manufacturer).
7. In order to ensure the cutting quality during cold forming, the cold drawn material is required to have a hard surface and a soft core.
8. Cold drawing materials should be subjected to cold upset forging test. The Wenzhou cold heading machine also requires that the material's sensitivity to cold work hardening should be as low as possible to reduce the deformation process due to the increase in deformation resistance due to cold work hardening.