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How expensive are large forgings? What problems should be paid attention to in the forging process? What should I do if there are cracks?

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How expensive are large forgings? What problems should be paid attention to in the forging process? What should I do if there are cracks?

How expensive are large forgings? The forging process is to cut the material to the required size, heat, forge, heat treat, clean and inspect. In small-scale hand forging, all of these operations are carried out by several forge workers in small locations, exposed to the same hazardous environmental and occupational hazards; in large-scale forging workshops, different jobs present different hazards. Moderate-intensity physical labor, hot and dry microclimate environment, producing noise and vibration, and air pollution by smog.

Another is that workers are exposed to both high temperature air and thermal radiation, resulting in the accumulation of heat in the body. Heat plus metabolic heat can cause heat dissipation barriers and lesions. The amount of perspiration during 8-hour labor varies depending on the small gas environment, physical exertion and thermal adaptation, and is generally between 1.5-5 liters, or even higher. In the forging shop, near the furnace or the work point of the drop weight. Forging is carried out in the hot state of the metal (eg mild steel is forged in the temperature range 1250-750). Due to the amount of physical labor, injuries can occur if care is not taken. So be very careful.

How expensive are large forgings? Equipment used by forging manufacturers, such as air hammers, steam hammers, friction presses, etc. Gives a blast while working. When the equipment is subjected to such an impact load, it is easy to be suddenly damaged (such as the sudden break of the forging hammer piston rod), resulting in serious injury accidents. Noise and Vibration The 3360 forging hammer will inevitably produce low-frequency noise and vibration, but there may also be certain high-frequency components, and its sound pressure level is between 95-115 decibels. Workers exposed to forging vibration can cause temperament and functional impairments that reduce work capacity and affect safety. Therefore, relevant protective measures must be taken.

How expensive are large forgings? What should I do if forging cracks occur in forging production? This requires analysis of the reasons for this situation.

(1) Forging cracks caused by ingot defects Most ingot defects may cause cracks during forging. 2Cr13 spindle forging center crack. This is because the crystallization temperature range of the 6t ingot is narrow and the linear shrinkage coefficient is large during solidification. Insufficient condensation feeding, large temperature difference between inside and outside, large axial tensile stress, cracking along dendrites, forming intergranular cracks in the ingot shaft, and further expansion during forging, becoming a cracked ingot shaft forging. Large forging price

(2) Forging cracks caused by the precipitation of harmful impurities in the steel along the grain boundary The sulfur in the steel is often precipitated along the grain boundary in the form of FeS, and its melting point is only 982. At the forging temperature of 1200°C, FeS on the grain boundary will melt and surround the grains in the form of a liquid film, destroying the bond between grains, resulting in thermal embrittlement and cracks after slight forging. Large forging price

(3) The mechanical properties of the second phase in the forging cracked steel caused by the different phase (second phase) are often quite different from the mechanical properties of the metal matrix, so additional stress will be generated during the deformation and flow process, resulting in the overall process plasticity decline. Once the local stress exceeds the binding force between the heterophase and the matrix, voids are formed by separation. For example, oxides, nitrides, carbides, borides, sulfides, silicates, etc. in steel. if these phases are dense. During high temperature forging, the distribution of chains, especially weak bonds along grain boundaries, can cause cracks. Figure 6-10 shows the macroscopic morphology of the forging crack caused by the precipitation of fine AlN along the grain boundary of the 87t ingot of 20SiMn steel. The surface has been oxidized, showing a polyhedral columnar crystal. Microscopic analysis shows that the forging cracking is related to the precipitation of fine AlN along the primary grain boundaries.

The countermeasures are:

1) Limit the amount of aluminum added to the steel, remove nitrogen from the steel or suppress AlN precipitation by adding titanium; large forging prices

2) Adopt steel ingot hot delivery and supercooling phase change process;

3) Increase the heat transfer temperature (90) to directly heat forging; the price of large forgings

4) A sufficient homogenization annealing is carried out before forging, so that the precipitation phase diffuses in the grain boundary.

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