The production process of cold-headed parts mainly includes the following steps:
- Raw Material Preparation: Select suitable metal wire, typically carbon steel, alloy steel, or stainless steel. The diameter needs to be determined based on the final product dimensions. The wire needs to be annealed to improve its plasticity, facilitating subsequent processing.
- Cold Heading: Feed the wire into a cold heading machine, where it undergoes plastic deformation at room temperature using molds. The cold heading machine uses multi-station molds to gradually form the part. Common stations include cutting, pre-forming, and final forming. For example, bolt head forming may require 3-5 stations, with a pressure range typically between 50-200 tons.
- Threading: For parts requiring threads (such as bolts), threads are processed using a thread rolling machine or thread rolling mill. The thread rolling speed is recommended to be controlled between 100-300 rpm to ensure thread accuracy and surface quality.
- Heat Treatment: Perform quenching and tempering treatment (such as quenching + tempering) according to the material and requirements to improve strength and hardness. For example, carbon steel parts may be quenched at 850-900℃ and then tempered at 400-600℃.
- Surface Treatment: Common methods include electro-galvanizing, hot-dip galvanizing, and Dacromet coating to improve corrosion resistance. The thickness of the hot-dip galvanized layer is typically 40-80μm, and the immersion temperature needs to be controlled at around 450℃.
- Inspection and Packaging: Dimensions, hardness, torque, etc., are tested. After passing inspection, the parts are packaged according to requirements (e.g., in boxes or bags).
