Microstructure for 45# Thick Wall SMLS Tube

45 # thick-walled smls tube quenching temperature in A3 + (30 ~ 50) , in the actual operation, the general is to take the upper limit. High quenching temperature can make the workpiece heating speed, surface oxidation reduced, and can improve work efficiency. In order to homogenize the austenite of the workpiece, a sufficient holding time is required. If the actual installed capacity is large, you need to extend the insulation time. Otherwise, there may be due to uneven heating caused by the phenomenon of insufficient hardness. But the insulation time is too long, there will be thick grain, oxidative decarburization serious ills, affecting the quality of quenching. We believe that if the furnace installed capacity is greater than the provisions of the process, heating and heating time to be extended 1/5.

Because 45 # precision steel pipe hardenability is low, it should use the cooling rate of 10% brine solution. After the workpiece into the water, it should be hardened, but not cold, if 45 # precision steel pipe in the brine cold thoroughly, it is possible to crack the workpiece, this is because when the workpiece cooled to 180  or so, the austenite quickly changed to horse The body is caused by excessive tissue stress. Therefore, when quenching the workpiece quickly cooled to the temperature area, it should be taken to slow the cold method. As the water temperature is difficult to grasp, to be experienced operation, when the water in the workpiece jitter stop, you can air cooling (such as oil cool better). In addition, the workpiece into the water should not be static, should be in accordance with the geometric shape of the workpiece, for the rules of movement. Static cooling medium with static workpieces, resulting in uneven hardness, uneven stress leaving the workpiece deformation, or even cracking.

45 # thick-walled seamless steel pipe quenched and tempered after quenching hardness should reach HRC56 ~ 59, the possibility of lower cross-section, but not lower than the HRC48, otherwise, it shows that the workpiece is not fully quenched, the organization may appear Soxhlet Body and even ferrite tissue, this organization through the tempering, still remain in the matrix, not the purpose of quenching and tempering.

45 # thick-walled seamless steel pipe after quenching high temperature tempering, heating temperature is usually 560 ~ 600 , hardness requirements for HRC22 ~ 34. Because the purpose of quenching and tempering is to get comprehensive mechanical properties, the hardness range is wide. But the drawings have hardness requirements, it is necessary to adjust the tempered temperature according to the drawings to ensure the hardness. If some shaft parts require high strength, hardness requirements on the high; and some gears, with keyway shaft parts, due to tempering but also after milling, plug processing, hardness requirements on the lower. On the tempering holding time, depending on the hardness requirements and the size of the workpiece, we believe that the hardness after tempering depends on the tempering temperature, and the tempering time is not, but must be back through, the general workpiece tempering holding time is always more than an hour.