1. Precise control of forging process parameters
Forging process parameters have a key influence on the toughness of 304 Stainless Steel Forgings. The first is the forging temperature. The forging temperature of 304 stainless steel needs to be strictly controlled in the appropriate range. Generally speaking, the initial forging temperature should not be too high, and it is advisable to control it at 1050-1100°C. The final forging temperature should not be too low, and it should not be lower than 900°C. If the initial forging temperature is too high, the stainless steel will stay at high temperature for too long, which will cause the grains to grow rapidly and reduce the toughness of the forgings. During the forging process, high-precision temperature monitoring equipment, such as thermocouple thermometers, should be used to monitor temperature changes in real time. At the same time, the forging ratio should not be ignored. A suitable forging ratio helps to break the original coarse grain structure and make the structure uniform and refined. Usually, it is more appropriate to choose a forging ratio of 3-5. Through multiple upsetting and drawing operations, the metal can be fully deformed in all directions, the internal structure can be optimized, and the toughness can be improved. In terms of deformation rate, a moderate deformation rate should be adopted. For example, when a hydraulic press is used for forging, the metal can be given enough time to adjust the internal structure, promote dynamic recrystallization, refine the grains, and improve toughness.
2. Fine control of microstructure
From the perspective of microstructure, grain boundary strengthening is an important means to improve toughness. In 304 stainless steel, grain boundary strengthening can be achieved by adding trace amounts of alloying elements. For example, adding an appropriate amount of titanium (Ti) or niobium (Nb) elements, these elements will be concentrated at the grain boundaries to form stable compounds such as TiC or NbC, thereby effectively preventing the migration of grain boundaries, inhibiting grain growth, refining the grain structure, and improving the toughness of forgings. In addition, the balance between dislocation strengthening and recovery is also critical. A large number of dislocations will be introduced during the forging process. Appropriate dislocation density can increase strength, but too many dislocations will reduce toughness. After forging, the dislocation state can be adjusted by controlling the cooling rate or performing appropriate heat treatment. For example, annealing treatment is carried out, and the temperature is kept in the range of 600-700°C for a period of time to rearrange and partially eliminate dislocations, thereby improving toughness while maintaining a certain strength.
3. Strict control of raw material quality
The quality of raw materials is the basis for improving the toughness of 304 Stainless Steel Forgings. When smelting 304 stainless steel, the chemical composition, especially the content of impurity elements, must be strictly controlled. Impurity elements such as sulfur (S) and phosphorus (P) should be reduced as much as possible. Sulfur easily forms low-melting eutectics at grain boundaries, and phosphorus reduces the grain boundary bonding force, which will significantly reduce the toughness of forgings. The use of advanced smelting technologies, such as AOD (argon oxygen decarburization refining) or VOD (vacuum oxygen decarburization refining), can effectively remove impurities and improve the purity of raw materials. At the same time, the metallographic structure of the raw materials should also be strictly inspected to ensure that its initial structure is uniform, avoid defects such as coarse grains and segregation, and provide good starting conditions for the subsequent forging of high-toughness forgings.
4. Reasonable post-processing operation
Post-processing is also very important for improving the toughness of 304 Stainless Steel Forgings. After forging, if machining operations are performed, appropriate cutting parameters should be selected. Excessive cutting force may introduce residual stress on the surface of the forging and reduce toughness. According to the size, shape and processing requirements of the forging, the parameters such as cutting speed, feed rate and cutting depth should be reasonably determined to reduce the generation of residual stress. In addition, heat treatment is also an effective post-processing method. In addition to the annealing treatment mentioned above, solid solution treatment can also be performed according to actual needs. Solid solution treatment can make the second phase such as carbide fully dissolved in the matrix, improve the uniformity of the matrix, eliminate the internal stress generated during the forging process, and thus improve the toughness of the forging. When performing solid solution treatment, parameters such as heating rate, holding time and cooling rate should be accurately controlled to ensure the best treatment effect.
