Submerged Overlaying Welding Of Composite Alloy Coating With Ultra-Fine WC And Simulation Of Its Process

Rollers of continuous casting machines are main parts of continuous casting and rolling equipments, and they are liable to be destroyed by thermal fatigue and abrasion, so they have been often repaired by various surface cladding processes. Flux-cored wires as submerged arc surface hardening materials are widely used at home and abroad in recent years. They are considered as a new type of welding materials and can replace solid wires completely. The Flux-cored wires are of many advantages such as good flexibility in adjusting chemical composition, good welding quality, low cost etc, so they have been becoming the main stream of development and application of automatic welding materials. The properties of alloy coating for submerged overlaying welding are the same as that of laser clad coating. A new type of materials of composite alloy coating with ultra-fine WC for submerged overlaying welding on the surface of continuous casting machines rollers is studied in this paper.According to the characteristics of Cr13 series of flux-cored wires, the strengthening function of the alloy elements such as Cr, Ni, C and V is studied. The transition coefficient and the appropriate contents of alloy elements are determined through series of experiments and calculation. As a result, heat-resistant stainless-based composite coating material with excellent combination properties is designed, In order to improve the welding technology and the wear-resistance of the coating materials, ultra-fine WC is prepared by using the mechanical ball milling method and different sizes of Ultra-fine WC powders are blended into the alloy matrix Powders. The effect of different welding processes on the microstructure and mechanical properties of the composite coating are analyzed. In the present study, the experiments of the wear-resistance and heat fatigue -resistant properties of the cladding are also carried out, and the basic principles of the wear-resistance and heat fatigue -resistant of the cladding materials are discussed.The design of the welding wire is based on the common Cr13 series of flux-cored wire. Different from the single microstructure of Cr13 series of overlaying coating, the final overlaying materials obtained in the present study is a kind of composite alloy coating reinforced with different kinds of dispersion carbides by the interactions of the matrix alloy elements and ultra-fine WC powders blended into the alloy powders. The unique composite microstructure can both raise the hardness and improve application properties of theoverlaying coating greatly such as the fatigue heat-resistant and the wear-resistance properties. Thus it is very important to the application of the ultra-fine WC to welding materials.Based on FEM theory, a feasible dynamic simulation method on 3D welding temperature and stress fields are established. Taking the welding process of plane board as an example, the APDL (ANSYS Parametric Design Language) programs are compiled by applying ANSYS software. The heat source model of gauss function is used in computation. Consequently, the problem of moving heat source is well solved. It provides a theory foundation for optimizing welding technologies and analyzing the complicated welding temperature and stress fields. So it promotes the application of FEM on welding mechanical analysis.