Steel quenching process

Steel quenching is one of the steel after austenitizing with appropriate cooling rate and cooling parts within the cross section all or within a certain range unstable martensite structure change of heat treatment process. one The technological process of hardening workpiece artifacts commonly: quenching to cleaning and tempering, sandblasting, Or shot peening, etc. ) Surface cleaning and inspection. And easy deformation of the workpiece shaft parts: quenching to cleaning to tempering, straightening, to deal with stress - sand - inspection. 2. The preparation before quenching ( 1) Check the quantity, material and size of workpiece, and check whether there is any crack on the artifacts, bruised, lack of edge, sharp edges, sharp corners and corrosion defect affecting the quality of quenching. ( 2) According to drawings and process documents, clear the specific requirements of the quenching, such as the local scope of quenching hardness, etc. ( 3) According to quenching requirements, choose the appropriate tooling design, proper binding, some of the artifacts in easy to produce crack place, take the corresponding protective measures, such as iron or asbestos rope bandage and wall hole, etc. ( 4) Surface oxidation and decarburization of the workpiece, should be allowed in the salt bath furnace or pre vacuum protective atmosphere furnace heating, or take the following precautions: a. Coating, recommended to choose the following coating formula: (1) 10% graphite + 90% grease ( The mass fraction) 。 ② 100gSiO2+5gAl2O3+25gNaSiO3+40gH2O. Hot coating is 0. 05 ~ 0. When the heating temperature is less than 10 mm 1050 ℃ anti oxidation and decarbonization. (3) 20 gsio2 + 10 al2o3g feldspar gcr2o3 10 + 10 + 10 g gsic + 8 gksio3 0 + 12 ~ 15 gh2o0 thermal coating. 2 to 0. 30 mm, heating temperature is less than 1200 ℃ anti oxidation and decarbonization. b。 The artifacts into charcoal or have already used cast iron iron box, affix a seal. ( 5) A large number of artifacts must be single or small batch test quenching, formulating process rear can batch quenching, often in the process of production and sampling. 3. Furnace charging, 1) Allow different material but with the same heating process of artifacts in the same furnace heating. ( 2) Furnace charging artifacts should be dry, can not have oil and other dirt. ( 3) Cross section size of different artifacts in the same furnace, big should be put in at the back of the chamber of a stove or furnace, large and small workpiece heat preservation time are calculated respectively. ( 4) Furnace charging when the workpiece must be regularly put on furnace charging rack or furnace bottom, or special tools stacked with hooks, forceps, shall not be within the workpiece directly behind charging, so as to avoid bruising artifacts or damage to the lining. ( 5) Slender workpiece must be in pit type furnace or salt furnace vertical hanging heating, in order to reduce deformation. ( 6) In his chamber furnace heating workpiece, generally for single permutation, workpiece clearance 10 ~ 30 mm. Small to allow proper stacking, but the heat preservation time should be appropriately increased. Four. Heat 1. Heating mode ( 1) Carbon steel and alloy steel workpiece, generally can be directly loaded than stipulated by the high quenching temperature in the furnace of 20 ~ 30 ℃ heating. ( 2) High carbon high alloy steel and complex shape workpiece should be preheated. 2. The heating temperature. 3. The calculation of workpiece heating time: furnace heating temperature of workpiece shall, in accordance with the provisions of the range of appropriate time, the necessary organizational transformation and diffusion. Heating time is from the workpiece loading charging, electric heat to keep out the whole heating process. Heating time and the effective thickness of the workpiece, steel, furnace charging ways, with the furnace, furnace temperature and furnace installed and sealing performance level and other factors. 4. The choice of effective thickness, At the same time for annealing and normalizing process) ( 1) Round rod workpiece diameter calculation. ( 2) In flat workpiece thickness calculation ( Thermal insulation coefficient selection ceiling) 。 ( 3) The diameter of the solid cone from big end 1/3 height on calculation.