Cold upsetting is a forging process that uses dies to upset metal bars at room temperature. It is usually used to make the heads of screws, bolts, rivets, etc. It can reduce or replace cutting. The material for forging billet can be copper, aluminum, carbon steel, alloy steel, stainless steel and titanium alloy. Cold heading is usually carried out on a special cold heading machine, which is convenient for continuous, multi station and automatic production. On the cold heading machine, the cutting, upsetting, accumulation, forming, chamfering, twisting, shrinking and trimming processes can be completed sequentially. The following is a brief introduction to the common problems and solutions of the cold heading process.
1. What are the characteristics of cold heading technology?
(1) According to the theory of metal plastic deformation, a certain pressure is applied to the metal blank at room temperature to make it plastic deformation in the cavity and shape it according to the prescribed shape and size.
(2) It is necessary to select high-quality “plastic deformation” good metal materials, such as rivet screw steel, its chemical composition and mechanical properties have strict standards.
(3) cold heading bolts and nut forming machines have many models and series of machines. The equipment has reliable performance, high efficiency and stable product quality.
(4) the forming force of the product is large, and the power of configuration is high.
(5) good surface quality and high dimensional accuracy. Because of the cold work hardening in the upsetting process, the deformation should not be too large. Reduce cracking.
(6) cold heading technology is applicable to products with large quantities and various specifications so as to reduce costs.
Two. Matters needing attention in cold heading processing
(1) the corresponding fixture should be replaced according to the diameter of the steel bar.
(2) The mould and the central punch should be checked and confirmed to be free of cracks, and the concentricity between the upper and lower dies and the central punch should be corrected, bolts should be tightened, and safety protection should be done.
(3) After starting, it should run empty first, adjust the tightness of the upper and lower dies, calibrate the heading of the alignment die, and confirm the normal operation before it can be operated.
(4) the head should not be upset when the machine does not reach the normal speed. When the head size of the upsetting head is not uniform, the clearance between the punch and the fixture should be adjusted in time. The punch and guide block should be adequately lubricated.
(5) it is forbidden to replace shaft core, pin and change angle and speed regulation, nor to clean and refill.
(6) bending of steel bars exceeding the diameter specified in the nameplate is prohibited. When bending steel bars without cold drawing or with rusty skin, they should wear protective glasses.
(7) When bending high strength or low alloy steel bars, the maximum allowable diameter shall be converted according to the provisions of the mechanical nameplate and the corresponding mandrel shall be replaced.
Three. Performance requirements for special cold heading forming oils
(1) Excellent extreme pressure lubrication, high temperature resistance, extreme pressure and wear resistance, rust resistance and high temperature oxidation stability. Improving the precision and smoothness of the workpiece can prevent the sintering of the mould, satisfy the multi-position forming processing of standard and non-standard parts, and can be completely competent for cold heading stainless steel workpiece processing.
(2) Oil fume and “drifting fog” can be reduced to a minimum to meet the strict requirements of multi-die punching nuts with a strong die.
(3) It has good processing performance for products with large deformation, such as hollow, high strength bolts, sleeves, stainless steel hollow, semi-hollow rivets and so on.
(4) it can effectively protect the impact bar (punching needle) and die, prolong the service life and reduce the comprehensive cost.
(5) the heat dissipation is good, and the local temperature of workpiece and mold is too high during cold forming.
(6) high temperature resistance and good oil sludge. Low odor, low smoke, protect the operating environment.
(7) it has a certain degree of rust resistance, which can meet the rust prevention requirements in the process.
(8) it can meet the requirements of harsh cold heading stainless steel forming and large variant carbon steel forming.
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