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Methods to Improve Process Accuracy of Cold Heading Fasteners

2019/9/9 9:01:20 click:

Cold heading uses a die to press metal at normal temperature. The materials can be copper aluminum, carbon steel, alloy steel, stainless steel, titanium alloy, etc. The cold header can finish the cutting, heading, chamfering, thread rolling and other procedures in sequence.
First, a brief analysis of the characteristics of cold heading process
(1) Apply force to metal at normal temperature to make it produce characteristic shape and shape.
(2) Metal materials with good deformation must be selected, and their chemical composition and mechanical properties have strict requirements.
(3) The cold heading bolt and nut forming machinery has high efficiency.
(4) The workpiece has better surface quality and higher dimensional accuracy. Due to hardening during upsetting, the deformation amount should not be too large.
(5) The cold heading process is suitable for large batch and various standardized workpieces.
Second, the reasons that affect the precision of cold heading
(1) Chemical composition of raw materials: pure metal is better than alloy. Impurity elements usually cause brittleness reduction and deformation. Various alloys have different effects.
(2) Metallographic composition of raw materials: Different properties, shapes, sizes, quantities and states of metals have different effects on deformation.
(3) Process deformation temperature: The deformation increases with the increase of temperature, but this increase is not a simple straight-line increase.
(4) metal strain rate: the increase of strain rate has both the side of reducing metal deformation and the side of increasing metal deformation. The effect of these two factors ultimately determines the change of metal.
(5) Deformation mechanics requirements: compressive strain is beneficial to the exertion of deformation, while tensile strain is unfavorable to deformation.
(6) Other problem factors: under the condition of discontinuous deformation, the deformation of metal can also be improved.
Three, the selection of cold header equipment
(1) The connecting bearing capacity of crankshaft, machine body and impact connecting rod is large and the service life is long.
(2) The machine body is cast with nodular iron added with alloy, which has high tensile strength.
(3) Equipped with pneumatic clutch brake to reduce motor power consumption.
(4) The material cutting adopts a guide plate and the cutter bar has good balance.
(5) The cold header adopts open and closed clamp workpiece, and the clamp can be turned over or translated, which is favorable for forming process arrangement.
(6) Equipped with variable frequency speed regulation, stepless speed regulation is possible.
(7) Equipped with fault detector, the equipment will automatically stop when it fails, giving maximum protection to the equipment and mold.
(8) The lubricating oil circuit can effectively protect the workpiece on the basis of ensuring circulating filtration.
IV. Selection of Raw Materials for Workpieces
(1) The raw materials must be spheroidized and annealed, and their metallographic phase is spherical pearlite.
(2) In order to reduce the cracking of the material as much as possible and improve the service life of the die, it is also required that the cold-drawn material has as low hardness as possible to increase the deformation.
(3) The surface quality of the raw materials requires that the lubricating film is dull and dark, and at the same time, the surface shall not have defects such as scratches, folds, cracks, napping, rust, oxide scale and pitting.
(4) The raw materials shall be subjected to cold heading test, and the lower the hardening of the materials for cold working, the better.
This is the way to improve the process precision of cold heading fasteners. If you are interested in these, you can visit our official website for more content.
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