As an important fastening element in modern industry, the manufacturing process of rivet nuts integrates a number of precision process technologies. This special fastener with internal threads is widely used in automobile manufacturing, electronic equipment, rail transportation and other fields, especially suitable for thin plate connection and working conditions where tapping is not possible. The following will systematically sort out its complete manufacturing chain from raw materials to finished products.
The manufacturing process starts with the material selection link, and carbon steel, stainless steel and aluminum alloy are the main base materials. Carbon steel is represented by low carbon steel such as 1015 and 1022 and SCM435 alloy steel. The former is suitable for conventional strength requirements, while the latter is used in high-load scenarios such as heavy machinery. Stainless steel materials mainly use A2/A4 series, which performs well in corrosive environments such as food machinery and marine equipment. Aluminum alloys such as 5052 and 6061 have become the first choice for aerospace and electronic product housings due to their lightweight advantages.
Raw materials need to undergo a pretreatment process before entering the cold heading process. Carbon steel materials need to be spheroidized annealed. By heating the steel to the Ac1 temperature range and then slowly cooling it, the layered cementite in the pearlite is transformed into a spherical structure. This process can significantly improve the plasticity and processing properties of the material. For aluminum alloy materials, stress relief annealing is required to eliminate the residual stress inside the material and prevent deformation or cracking during subsequent processing.
The forming stage uses a multi-station cold heading process to continuously extrude the material through a precision mold. The standard process includes key steps such as bottom positioning, upsetting shaping, edge chamfering and center perforation. For closed rivet nuts with complex structures or special specifications, secondary processing is required with CNC lathes after cold heading to ensure that key dimensions meet micron-level precision requirements.
Internal thread processing is the core link that determines product performance, and mainly uses tapping cutting and rolling extrusion. The rolling forming process has become the preferred processing method for high-strength rivet nuts because of its advantages in maintaining the integrity of metal streamlines and improving the density of thread surface. This process applies high pressure to the workpiece through a high-speed rotating rolling wheel, causing the material to undergo plastic deformation to form a precise thread profile, which can increase the thread strength by more than 30% compared to traditional cutting methods.
The heat treatment process is treated differently according to the material difference, and medium carbon steel and alloy steel products need to be quenched and tempered. Taking SCM435 material as an example, after quenching at 850℃ and tempering at 500℃, an ideal hardness value of 28-36HRC can be obtained, achieving the best balance between strength and toughness. Stainless steel material has good corrosion resistance and usually does not require additional heat treatment.
Surface treatment is a key step to improve product durability. Common processes include electrogalvanizing, Dacromet coating, phosphating, etc. Among them, trivalent chromium Dacromet coating can provide more than 500 hours of salt spray protection. For occasions where conductive properties are required, nickel plating or anodizing is used. The surface hardness of 6061 aluminum alloy can reach more than HV400 after hard anodizing.
Quality control runs through the entire production process. In addition to conventional dimensional tolerance testing, thread gauge testing, axial tensile testing and anti-rotation performance verification are also required. According to the DIN7337 standard, M6 steel rivet nuts must withstand an axial tensile force of at least 12kN. Stainless steel products must pass a 96-hour neutral salt spray test, and no red rust corrosion should occur on the surface. Common problems such as tapping eccentricity and incomplete tooth profiles during production are mainly controlled through mold precision maintenance and processing parameter optimization.
From spheroidizing annealing to final inspection, precise control of each process creates excellent mechanical properties for rivet nuts. This seemingly simple fastener is actually the result of material engineering and precision manufacturing technology, and its reliable connection performance is continuously driving the advancement of modern industrial assembly technology.
Post time: Apr-11-2025