Interpretation of the effects of the melting and casting process on the microstructure and properties of copper-steel bimetallic composite materials
Abstract: High-lead bronze CuPb15Sn7/45 steel bimetallic layered composite materials were prepared using the melt-cast composite method. The influence of process parameters such as heating conditions and cooling rates on the copper-steel composite interface and structural properties was studied. The results show that when the furnace charging temperature is 900°C, the holding temperature is 1015°C, the holding time is 5 minutes, and nitrogen cooling is used, the copper-steel interface has excellent metallurgical bonding properties, and the interface tensile fracture strength reaches 200 MPa; the copper alloy The distribution of lead particles in the area is relatively uniform, and the burning loss of lead element is less than 1%; the structure and grain size distribution of the steel matrix are reasonable, showing excellent melting and casting composite effect.
As the requirements for the comprehensive performance of engineering materials become higher and higher, it is increasingly difficult for parts made of a single metal material to meet their all-round performance requirements. Coupled with the gradual scarcity of precious metal resources, bimetallic layered composite materials have gradually been promoted and applied in industry. On the basis of maintaining the original characteristics of each layer of metal, the overall performance of layered metal composite materials has been significantly improved, and its preparation process has attracted more and more attention.
High-lead bronze has good thermal conductivity, wear resistance, impact resistance and seizure resistance, and is widely used in the manufacture of hydraulic components such as plunger pump cylinders. At the same time, since the lattice type, lattice constant and number of external electron atoms of copper and iron are very close, they have good composite metallurgical compatibility. The copper-steel bimetallic layered composite material prepared with steel as the matrix layer and high-lead bronze as the composite layer combines the excellent properties of both materials. At present, common methods for preparing copper-steel bimetallic layered composite materials include explosive composite method, rolling composite method, diffusion composite method, centrifugal casting method, melting casting method and powder sintering method. Among them, the explosive compounding method and the rolling compounding method are mainly used to prepare bimetallic layered plates; the diffusion compounding method has a long preparation cycle, and long-term heat preservation can easily cause serious oxidation and burning loss of lead elements, and the cost is also high; the centrifugal casting method can easily cause Macro-segregation of lead element; powder metallurgy involves many processes, long preparation cycle, and high cost.
The melt-cast composite method in which two materials are heated at the same time has obvious technical and cost advantages in preparing copper-steel bimetallic layered composite materials. This article will study the influence of specific process parameters on the microstructure and properties of copper-steel bimetallic materials through melt-cast composite experiments. The laws provide a theoretical basis for formulating a reasonable copper-steel bimetal melting and casting composite plan.
1. Test plan
1.1 Test materials
The materials used in the test include high-lead bronze CuPb15Sn7 and 45 steel. The chemical compositions of the two materials are shown in Table 1. Before the test, the 45 steel was processed into a cylinder of Φ42 mm × 45 mm, a groove of Φ32 mm × 7 mm was machined at one end, and the copper alloy was processed into a disc of Φ30 mm × 6 mm. After machining, it needs to go through surface treatment processes such as sandpaper grinding, alkali washing, pickling, and 80°C saturated borax water immersion, and then assembled as shown in Figure 1 for a casting test.
