The influence of raw materials on the microstructure and mechanical properties of forging

Raw materials for ingot casting forging, rolling, extrusion and forging stock. And rolling, extrusion and forging stock are respectively ingot are formed after rolling, extrusion and forging processing semi-finished products. For casting of spindle, furnace charge composition, method of smelting and forging process is the important link to determine its quality. While rolling, extrusion and forging processing, is another part in determining the quality of the corresponding semi-finished products. Raw materials before entering the forging process, need to the size, surface quality, chemical composition, microstructure, macrostructure and mechanical properties test, conform to the requirements of the technical conditions of the rear can put into production. The chemical composition of raw materials, high power organization, macrostructure and mechanical properties of forgings organization performance is the basic, and the size and the surface quality of the raw materials directly affect the forging process of plastic and forming. In addition, the malleability of raw materials and recrystallization characteristics is the foundation of the forging process parameters. Therefore, good quality of raw materials is a prerequisite to ensure the quality of forgings. However, the quality inspection of raw materials has certain limitations, Such as: the residual and the sample is not representative, etc. ) Test method, the technical conditions of raw materials, impossible to put all the inside of the steel quality problems are exposed, such as: internal composition and segregation, etc. Various defects existing in the raw materials, therefore, is bound to affect the quality of forgings and forging forming process of the final. The influence of raw materials on the microstructure and mechanical properties of forgings, basically has the following several aspects: 1. Chemical composition and the influence of impurity elements in the technical conditions of raw materials, the chemical elements are rules on the scope of the corresponding component, the impurity element S, P, Cu, Sn, Pb and so on also to have certain restriction. Chemical elements beyond the prescribed scope and content of impurity elements of forging forming and high quality will bring great influence. S, B, Cu, Sn elements such as formation of low melting point phase, forging heat brittle is seen. The essence of the Al content of alloy steels have effects on grain size. In order to obtain essence fine grained steel, residual aluminum content in the steel should be controlled within a certain range, Such as: 0 Al acid. 02 ~ 0. 04%) 。 Aluminum content too little, don't control the effect of grain growth; Aluminum content too much, the pressure process under the condition of the formation of fibrous tissue easily build wood grain fracture and fracture tear marks, etc. , these will decrease the mechanical properties of the forgings and using performance. In 1 cr18ni9ti austenitic stainless steel, Ti, Si, Al, Mo content, the more the ferrite phase, the more the more easily when forging forming surface crack, and parts of magnetic. The formation of the raw materials of eutectic relative forgings and forging quality has a great influence, it makes the material before forging heating easy to burn and reduce the material plasticity index, etc. Such as: a eutectic carbide in ledeburite tool steel, aluminum alloy extruded bars the tree branch in eutectic compounds, etc. Bulky beta phase directly affect the forging of titanium alloy materials and conventional mechanical performance. 2. Influence of internal defects in raw materials raw materials inside the shrink tube residual, subcutaneous bubble, serious carbide segregation, bulky non-metallic inclusions ( Slag) Defects, such as easy to make the forging cracks. Raw materials within the tree branch crystal, severe osteoporosis, non-metallic inclusion, white spots, skull patch, oxide film, layered, segregation, and defects such as mixed with different metal, easy cause forging performance degradation. Trace amounts of non-metallic inclusions on the cold roll and the service life of bearing steel also has a great influence. 3. Raw material of surface defects affect the surface crack of raw material, folding, scarring, coarse grain ring and so on easy to cause the surface of the forging cracks. 4. The influence of raw material flow for forging and die forging rolling, extrusion and forging stock have fibrous tissue, therefore its performance have direction, this also is the basic cause of forging a directional performance. The severity of the directivity, depends on the content of S and P and other impurities in raw materials, and depends on the forging ratio of raw materials. When selecting forging forging scheme, therefore, should be according to the force of the parts, pay attention to the correct flow distribution. The malleability of raw materials and recrystallization features of forgings and forging quality also has a great influence. Good malleability of material formability. In general carbon steel and alloy structural steel craft high plasticity, low deformation resistance, good malleability. Low and high alloy and high temperature alloy process plastic, large deformation resistance, malleability. Have all sorts of alloy aluminium alloy middle and certain critical deformation range, when the deformation extent within the scope of the special thick grain, decrease the mechanical properties of the forgings and forging should avoid this range of critical deformation.