Conditioning is the double heat treatment of quenching and high temperature tempering, its purpose is to make the workpiece with good comprehensive mechanical properties. Quenched and tempered steel with carbon quenched and tempered steel and alloy quenched and tempered steel two kinds big, either carbon steel or alloy steel, carbon content control more strictly. If carbon content is too high, the strength of the workpiece after tempering is high, but the toughness is not enough, such as the carbon content is too low, toughness and strength is insufficient. To make the conditioning get good comprehensive performance, general control the carbon content in the 0.30 ~ 0.50%.
904l stainless steel pipe is high nickel steel, hot and cold processing performance is good, better mechanical properties, and low price, wide source, so widely used. It is the biggest weakness of low hardenability, section size and require higher artifacts should not be used.
904L stainless steel pipe quenching temperature at 800 ℃, in practice, usually take limit. High heating speed, quenching temperature can make the workpiece surface oxidation reduction, and can improve working efficiency. To make the workpiece austenitic homogenization, you need enough time of heat preservation. If the actual furnace charging quantity, it should be appropriately extended holding time. Otherwise, there might be caused by uneven heating of hardness insufficient phenomenon. But the heat preservation time is too long, will also appear coarse grains, oxidation decarbonization serious ills, affect the quenching quality. We believe that such as furnace charging quantity is greater than the terms of the process documents, 1/5 heating heat preservation time should be extended.
Because steel hardenability is low, so the cooling speed of 10% saline solution should be adopted. Artifacts into the water, should be hardening, but not cold, if the artifact in brine is cold, it is possible to make the workpiece craze, this is because when the workpiece when cooled to about 180 ℃, austenite into martensite rapidly cause too much stress caused by the organization. Therefore, when the temperature of the quenching workpiece fast cooling to the area, should take the slow cooling method. Because of the water temperature is difficult to grasp, experience in operation, when the workpiece shaking stops in the water, then air cooling water (e.g., better oil cooling). In addition, the workpiece into the water should move should not be static, should according to the workpiece geometry, as a rule. The stillness of the cooling medium and the stillness of the workpiece, resulting in uneven hardness, the uneven stress and make the workpiece deformation is large, and even cracking.