Introduction to cold heading products for precision manufacturing of hardware fasteners
Overview of cold heading process
Cold heading process is a new process for metal pressure processing with little or no cutting. It uses the plastic deformation of metal under the action of external force, and uses the mold to redistribute and transfer the metal volume to form the required parts or blanks. It is most suitable for producing standard fasteners such as bolts, screws, nuts, rivets, and pins.
This process is usually carried out at room temperature and can improve the mechanical properties of metal parts. For example, the tensile strength of bolts after cold heading is about 10% higher than that of cutting, and some can even be increased by 20%. This is because the metal fibers of the cold heading products will not be cut off, the internal structure of the metal is compacted, and the accompanying work hardening phenomenon improves the mechanical properties of the metal.
Product features
1.High material utilization rate: Taking cold heading bolts as an example, the material utilization rate of the new process "concave" hexagonal head bolts can reach more than 99%, and the material utilization rate of nuts can also reach 80% About, compared with cutting processing, it greatly reduces material waste.
2.High productivity: For example, compared with the original cutting process, the productivity of cold heading nuts is about 25-30 times higher. The application of multi-station cold heading machines enables the simultaneous processing of various processes on one machine tool, reducing equipment investment, production site occupation and the transportation of semi-finished products between various processes, reducing the labor intensity of workers and improving working conditions.
3.Good product quality: It can improve the surface finish of the product. The general finish can reach V5, and the special requirements can reach V6. In addition, for bolts and nuts produced in large quantities, their accuracy can be guaranteed.
Raw material requirements
4.High plasticity and low hardness: Due to the tangential tensile stress on the side surface of the blank during cold heading, longitudinal surface cracks are easily generated. Therefore, the raw materials are required to have higher plasticity and lower hardness. For steel, the surface hardness is generally required to be 75-85HRB.
5.High surface quality: The cold heading process is mainly used for the production of standard parts. These products are generally no longer cut, especially standard parts such as screws and bolts. The shank is rarely deformed during the cold heading process and still maintains the original surface of the blank. Therefore, the raw materials for cold heading must have a low surface roughness, and surface defects such as scratches, pitting, and rust are not allowed.
High dimensional accuracy: In order to ensure the volume of the blank is accurate, the diameter tolerance of the blank must be very small.
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