45 Steel Heat Treatment
Quenched with a hardness range is generally between 225-297HB. 45 # steel is quenched if, that is, quenching and tempering, the highest hardness should 297HB, namely 31 ~ 32HRC it! This is the ideal state. General may also reach this value.
45 steel hardened, quenched with water generally able to achieve if 40 ---- 60HRC (depending on the size and material of the water), oil quenching is generally between 30 ---- 55HRC (based on the size and type of material thickness is different quenching oil ).
Crack in the heat treatment process does not reach the number of split and there is no relationship between hardness and shape, and heat treatment of the workpiece, such as a relationship.
Low carbon steel commonly used normalizing. To give the pearlite structure after normalizing to facilitate cutting. High carbon steel, alloy steel annealing is applied (ordinary, ball, isothermal.)
Quenching quenching and tempering of the dual heat treatment, which aims to make the work with good mechanical properties.
Quenched and tempered steels are carbon steel and alloy quenched and tempered steel two categories, either carbon or alloy steel, the carbon content of more stringent controls. If the carbon content is too high, the strength of the workpiece after quenching is high, but the toughness is not enough, as the carbon content is too low, toughness and lack of strength. In order to get a good piece quenched overall performance, the general control of the carbon content of 0.30 to 0.50%.
When the tune of hardened, the entire section of the workpiece hardenability requirements, so that the workpiece with fine needle to get quenched martensite microstructure dominated. By tempering to obtain a uniform sorbite oriented microstructure. Each furnace is impossible to engage in small factories metallurgical analysis, generally only for hardness testing, that is to say, must meet hardness after quenching quenching hardness of the material, the hardness required to check in Figure tempering.
Operation workpiece quenching must be in strict accordance with the implementation of process documents, during the operation we just put some views on how to implement the process.
1, 45 quenched and tempered steel
45 is a medium carbon steel structural steel, hot and cold workability are good, good mechanical properties, and low prices, wide sources, so widely used. Its biggest weakness is the low hardenability, cross-sectional dimensions Japan is relatively high workpiece should not be used.
45 steel quenching temperature in A3 + (30 ~ 50) ℃, in practice, is usually taken caps. High quenching temperature to heat the workpiece speed, reduce surface oxidation, and can improve efficiency. The workpiece is uniform austenite, will require sufficient holding time. If the actual installed furnace capacity, would be appropriate to extend the holding time. Otherwise, there may be insufficient due to uneven heating caused by the hardness of the phenomenon. However, the holding time is too long, will also appear coarse grains, oxidation and decarbonization serious ills affecting quenching quality. We believe that such equipment is greater than the specified process documents furnace, the heating need to extend the holding time of 1/5.
Because the 45 steel hardenability low, it should be 10% larger cooling rate of the salt solution. The workpiece into the water, it should hardenability, but not chilled, if chilled brine workpiece, the workpiece is likely to crack, because when the workpiece is cooled to about 180 ℃, causing the austenite into martensite rapidly tissue caused by excessive stress. Therefore, when the quenching of the workpiece to the fast-cooling temperature region, it should take slow cooling method. As the water temperature is difficult to grasp, accountable experience to operate, when to stop dithering artifacts in the water, the water can be air-cooled (eg oil cooler can be better). In addition, the work should move into the water should not be static, should be in accordance with the geometry of the workpiece, as the rules of sport. Stationary cooling medium plus stationary workpiece, resulting in uneven hardness, stress uneven leaving large deformation of the workpiece, and even cracking.