Analysis of the technological process of sewing machine fastener production technology

In the industry's Eleventh Five-Year Plan, sewing machine fasteners (screws), machine needles, and rotary hooks are included in key research projects. Through the efforts of related enterprises in the past four or five years, the production equipment and process technology of sewing machine fasteners have been innovated, and great progress has been made. Huayi has developed into the largest sewing machine fastener supporting enterprise in China. Now take it as an example to look at the technology and technology of sewing machine fasteners.

The production of sewing machine fasteners has gone through process links such as wool, spheroidization, wire drawing, cold heading, cutting, groove milling, thread rolling (thread rolling), heat treatment, grinding processing, and surface treatment. There are corresponding requirements in the setting of process parameters in each link. For example, in terms of material selection, nuts, screws larger than M4, and spring pin types should be made of No. 15 (15#) steel; the core strength of the fastener is required to be higher and the surface is subject to wear, which is larger than that of M4 screws and shaft positions. Use 20 chromium steel (20Cr) for screws. If there are parts with high core toughness, strength and wear resistance, tight screws less than or equal to M4, bit screws less than or equal to M4, etc., should be SCM415 type Steel; inner hexagon (including inner hexagon set) screws, outer hexagon screws, SCM435 type steel can be used.

In the production technology of sewing machine fasteners, such as the current spheroidization process, in the past, only the annealing method was used, which caused the fastener products to be easily deformed and cracked in the subsequent processing and quenching process, but now the spheroidization is adopted. The result of annealing is a spherical pearlite structure, in which cementite is spherical particles dispersed on the ferrite matrix, not only has low hardness, but also the surface is not easy to decarburize, so that the material has low sulfur content, is stable and reliable, and is easy to process. In addition, during quenching and heating, the austenite grains are not easy to grow, and the tendency of deformation and cracking of the workpiece during cooling is small. Another example is the cold heading process, which uses multi-station cold heading equipment such as two-die four-stroke, three-die three-stroke and five-die five-stroke, which can reduce subsequent processing procedures and ensure product size consistency. Another example is the heat treatment process, which uses carbonitriding technology. This is because the special screws for sewing machines require high hardness, high wear resistance, high impact toughness and fatigue strength. The conventional heat treatment is a carburizing process. This process will Facing the technical difficulties of deformation control, the scrap rate is high, and the carbonitriding process can reduce the deformation and improve the hardenability of the product.