Manufacturing a high-performance bimetallic screw requires sophisticated manufacturing techniques. The main process is as follows:
1. Substrate Machining and Pretreatment: According to design requirements, a blank shape for the screw is machined using qualified substrate materials. Then, the surface to be clad with the alloy layer undergoes rigorous cleaning and treatment to remove oil, oxides, and other impurities, ensuring surface activity and creating favorable conditions for subsequent alloy bonding.
2. Alloy Layer Cladding: This is the core step in bimetallic screw manufacturing. Currently, widely used processes include:
* Plasma Arc Powder Cladding: Utilizing the high-temperature plasma generated by a plasma arc as a heat source, high-performance alloy powder is instantly melted and sprayed onto the screw substrate surface, forming a uniform and dense cladding layer. This process concentrates heat, minimizes the thermal impact on the substrate, and produces a high-quality cladding layer.
* Laser Cladding: Using a high-energy laser beam as a heat source, the synchronously fed alloy powder is melted, causing it to rapidly solidify on the substrate surface. Laser cladding offers higher precision, lower heat input, and a lower dilution rate between the cladding layer and the substrate, better preserving the original properties of the alloy layer.
*Other processes, such as tungsten inert gas welding (TIG welding), are also used; the specific choice depends on a comprehensive consideration of screw performance, cost, and efficiency.
3. Heat Treatment: The cladding process generates significant internal stress and microstructure changes. After cladding, the screw undergoes appropriate heat treatment (such as annealing, quenching, and tempering) to eliminate internal stress, stabilize the microstructure, optimize the overall mechanical properties of the substrate and cladding layer, and prevent deformation or cracking during future use.
4. Finishing and Inspection: After heat treatment, the screw requires precision machining to achieve the final dimensional accuracy and surface finish requirements. After machining, it undergoes rigorous non-destructive testing (such as ultrasonic testing and penetrant testing) to ensure the cladding layer is defect-free and well-bonded to the substrate. Key indicators such as surface hardness and geometric dimensions are also tested to ensure that each screw meets quality standards.
