Defects in forgings include surface defects and internal defects. Some forging defects will affect the processing quality of the subsequent processes, while others will seriously affect the performance of the forgings, reduce the service life of the finished parts, and even endanger safety. Therefore, in order to improve the quality of forgings and avoid the occurrence of forging defects, corresponding technical measures should be taken, and the quality control of the whole process should be strengthened.
In forging production, in addition to the shape and size required for forgings, the performance requirements of the parts during use must be met, including: strength pointer, plastic pointer, impact toughness, fatigue strength, fracture toughness. And stress corrosion resistance, etc., for high temperature working parts, as well as high temperature transient tensile properties, long-lasting properties, creep resistance and thermal fatigue properties. The raw materials for forging are ingots, rolled products, extruded materials and forged billets. The rolled material, the extruded material and the forged blank are respectively semi-finished products formed by rolling, extrusion and forging of the ingot.
In forging production, using reasonable process and process parameters, the organization and performance of raw materials can be improved by:
1. Breaking the columnar crystals, improving macrosegregation, changing the as-cast structure into a forged structure, and welding the internal pores under appropriate temperature and stress conditions to increase the density of the material;
2. The ingot is forged to form a fibrous structure, and further, by rolling, extrusion, die forging, the forging obtains a reasonable fiber direction distribution;
3. Control the size and uniformity of the grains;
4. Improve the distribution of the second phase (for example: alloy carbides in the Leysite steel);
5. Make the tissue deformed or deformed - a phase change strengthening. Due to the improvement of the above-mentioned structure, the plasticity, impact toughness, fatigue strength and long-lasting performance of the forgings are also improved, and then the final heat treatment of the parts can obtain a good combination of hardness, strength and plasticity required for the parts. performance. However, if the quality of the raw materials is poor or the forging process used is unreasonable, forging defects, including surface defects, internal defects or performance failure, may occur.