What are the key links in the manufacturing process of bimetallic screws?

1. Raw material selection and preparation
Alloy steel materials: Bimetallic screws are made of high-quality 38CrMoAIA (JIS sacm645) and 42CrMo (AISI4140) alloy steel materials. They have high strength, good toughness and strong wear resistance, and are suitable for manufacturing screws that withstand high loads and harsh environments.
Material inspection and cutting: Before manufacturing begins, the raw materials must be strictly inspected to ensure that their chemical composition, mechanical properties and microstructure meet the standards. Subsequently, the raw materials are cut into suitable billets according to the design size and specifications.

2. Forming process
Forging or casting: After the billet is heated, the basic shape of the screw is formed through forging or casting. The forging process causes the material to undergo plastic deformation by applying pressure, thereby improving the density and mechanical properties of the screw; casting forms the desired shape by molten metal and injecting it into a mold.
Machining: The formed screws also need to undergo a series of machining processes, such as turning, milling, drilling, etc., to achieve precise size and shape requirements.

3. Heat treatment process
Vacuum quenching: As a key heat treatment step, vacuum quenching improves the hardness and strength of the material while reducing distortion and oxidation by heating the screw at high temperature and cooling it rapidly in a vacuum environment. This step is essential to ensure the high performance of bimetallic screws.
Tempering: The quenched screws also need to be tempered to eliminate quenching stress, improve toughness, and stabilize the size.

4. Surface treatment
Nitriding: In order to improve the wear resistance and corrosion resistance of the screws, nitriding is usually performed. Nitriding increases the surface hardness by forming a hard nitride layer on the surface of the screw.
Chromium plating: Chrome plating is a commonly used surface decoration and protection process that can improve the corrosion resistance and aesthetics of the screws.
High-frequency quenching: For certain specific parts, such as the threaded part, high-frequency quenching may be required to improve its wear resistance.

5. Quality inspection and packaging
After completing all manufacturing processes, the bimetallic screws need to be quality inspected, including dimensional inspection, mechanical properties test, corrosion resistance test, etc., to ensure that the product meets the standards.
The screws that pass the quality inspection will be properly packed with necessary quality certification documents and logos, and then prepared for shipment.