Effect of forging on metal structure and properties and forging defects

SCZY LTD has made a lot of Forging Parts , such as: Brass Forging Parts, Steel Forging Parts, Stainless Steel Forging Parts, Aluminum Forging Parts, Closed Die Forging Parts, etc. Now we would like to talk about the influence of forging process on forging quality. The forging process generally consists of the following processes, namely, feeding, heating, forming, post-forging cooling, pickling and post-forging heat treatment. A series of forging defects may occur if the process is improper during the forging process. The heating process includes furnace temperature, heating temperature, heating rate, holding time, furnace gas composition and the like. If the heating is improper, for example, the heating temperature is too high and the heating time is too long, it will cause defects such as decarburization, overheating, and overburning. For billets with large cross-sectional dimensions and poor thermal conductivity and low plasticity, if the heating speed is too fast, the holding time is too short, the temperature distribution is often uneven, thermal stress is caused, and the billet is cracked. The forging forming process includes deformation mode, deformation degree, deformation temperature, deformation speed, stress state, mold and lubrication conditions of the tool and die, etc. If the forming process is improper, it may cause coarse grains, uneven grains, various cracks, fold. Cold current, eddy current, as-cast tissue residue, etc. During the post-forging cooling process, if the process is improper, it may cause cooling cracks, white spots, reticulated carbides, and the like.

(IV) Effect of forging structure on microstructure and properties after final heat treatment Austenitic and ferritic heat-resistant stainless steel, high-temperature alloy, aluminum alloy, magnesium alloy, etc., in the process of heating and cooling, there is no homogeneous transformation of materials As well as some copper alloys and titanium alloys, the structural defects generated during the forging process cannot be improved by heat treatment. Materials with isomeric transformation during heating and cooling, such as structural steel and martensitic stainless steel, due to certain defects in the microstructure caused by improper forging process or some defects left by the raw materials, the quality of the forged parts after heat treatment Great impact. The examples are as follows:

1) The structural defects of some forgings can be improved in the post-forging heat treatment, and the satisfactory microstructure and properties can still be obtained after the final heat treatment of the forgings. For example, coarse-grained and Weiss microstructures in generally overheated structural Steel Forgings , slightly reticulated carbides and bearing steels due to improper cooling, etc.

2) The structural defects of some forgings are difficult to eliminate with normal heat treatment, and can be improved by high temperature normalizing, repeated normalizing, low temperature decomposition, high temperature diffusion annealing and the like. For example, low-order coarse crystals, twinned carbides of 9Cr18 stainless steel, and the like.

3) The structural defects of some forgings cannot be eliminated by the general heat treatment process, and as a result, the performance of the forged parts after the final heat treatment is degraded or even unqualified. For example, severe stone fractures and facet fractures, over-fired, ferritic belts in stainless steel, carbide meshes and belts in high-alloy tool steels.

4) The structural defects of some forgings will further develop during the final heat treatment and even cause cracking. For example, the coarse-grained structure in alloy structural steel forgings, if not improved after forging heat treatment, often causes martensite needle coarseness and unqualified performance after carbon, nitrogen co-infiltration and quenching; coarse ribbon carbonization in high-speed steel Things, often cause cracking during quenching. The common defects in the forging process and their causes are described in detail in Chapter 2. It should be noted that the common defects in various forming methods and the major defects of various material forgings are regular. Different forming methods have different stress and strain characteristics due to different stress conditions, so the main defects may be different. For example, the main defect when the blank is upset is that the side surface produces a longitudinal or 45° crack, and the as-cast material is thickened, and the as-cast structure remains in the upper and lower ends; the main defect in the rectangular section blank is the lateral crack of the surface. And corner cracks, internal diagonal cracks and transverse cracks; the main defects in open die forging are filling, folding and misalignment. Common defects in each major forming process are detailed in Chapter 4. Different kinds of materials, due to their different compositions and structures, have different structural changes and mechanical behaviors during heating, forging and cooling. Therefore, the forging process is not proper, and the defects may be special. For example, the defects of the high-alloy tool steel forgings are mainly coarse carbide particles, uneven distribution and cracks. The defects of high-temperature alloy forgings are mainly coarse crystals and cracks; the defects of austenitic Stainless Steel Forgings are mainly intercrystalline chromium-depleted. The resistance to intergranular corrosion is reduced, the ferrite band structure and cracks, etc.; the defects of Aluminum Alloy Forgings are mainly coarse crystal, folding, eddy current, and through flow. For more information about us, you can visit: www.sczyltd.com

Shenzhen SCZY Technology Co., Ltd
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