Study On Technology Of Bimetal Welding Prototyping Based On Single-pass Multi-layer Model

Welding prototyping shows a wide application prospects in the metal manufacturing field, due to a series of characteristics, for example, low cost, high efficiency, good properties, and so on. Composed structure of copper alloy and steel can effectively reduce the cost and satisfy the application, which is widely used in manufacturing field. Nowadays, some traditional methods for bimetal fabrication can be selected, which are casting, explosive welding, rolling, extrusion, and so on. But most of them are limited to specific shape and materials, or even not-ideal binding ability. Although novel rapid prototyping methods can manufacture bimetal with complicate shapes and perfect properties, such as multi-layer spray deposition and laser deposition, they will carry a cost penalty for their prices. Thus, it is meaningful to introduce welding prototyping into bimetal manufacturing field.In this article, silicon bronze and mild steel are selected as formed material. Based on the single-pass multi-layer model, bimetal wall-shape parts in different sequences of steel-to-bronze and bronze-to-steel are formed. Fabrication parameters are designed in details through experimental study. And then interface characteristics and tensile properties are investigated. At the same time, the process in the single-pass multi-layer fabrication is studied and some solutions are attempted to improve the manufacturing level.Results show that in the process of fabricating steel-to-bronze bimetal, moderate parameters should be chosen to ensure the quality and efficiency when specific steel bead is formed. An intermixing zone with12μm near the steel-to-bronze interface can be found, and a large number of a(Fe)-s(Cu) two-phase mixtures exist in the intermixing zone; Fe elements dissolve into the bronze side as the form of particles and big chunks; Si elements concentrate around the place where Fe elements appear for the physical and chemical reasons. Tensile test shows that the average tensile strength and elongation of the bimetal can reach305MPa and48.5%respectively, indicating a firm connection on the interface of steel-to-bronze bimetal. Different from the former one, it is inclined to generate the defects of cracks and collapsed phenomenon for bronze-to-copper bimetal. Experiment proves that heat input should be controlled below390J·mm-1to avoid these defects. However, heat input can not be too small to release the stress for poor thermal treatment, because it could not put an end for the Cu elements in steel. Therefore, heat input in the process should be in a moderate zone to reach the mechanical characteristics like steel-to-bronze bimetal wall-shape part.This thesis also attempts to fabricate parts in a short culling time between every two adjacent layers.30-layer hollow cylinder is manufactured by adjusting welding parameter. And a40-degree-inclined wall-shape part is formed with excellent surface by adding laser into the MIG welding arc. It offers a novel way to form single-pass multi-layer metal part.