General workpiece salt furnace quenching process

1. Process live ( Check the technology conditions, quantity) To identify material, determine the quenching operation mode to choose fixture, binding wire, drying, heating and cooling to cleanup, tempering to sand blasting, rust - alignment - inspection to surrender. 2. Quenching heating ( 1) Equipment: medium temperature salt bath furnace, commonly used salt bath into allocation ratio and scope of use in the table below, 2) Heating method is as follows: a. General parts after drying, directly in the quenching furnace heating. b。 Parts in the salt bath heating, suspension method should be adopted, should maintain proper clearance between parts; In addition, parts and the distance between the electricity pole should be not less than 30 mm; Parts from the salt bath surface should be not less than 50 mm; Parts with insulation. 3. Quenching ( 1) Cooling medium, and its composition and working temperature shown in the table below: - 2) In the 650 ℃ cooling medium ( The mass fraction) Ability to compare, 10% NaCl aqueous solution & gt; 50% NaOH aqueous solution & gt; 180 ℃ left right lye & gt; Diesel & gt; Oil & gt; Around 180 ℃ nitrate & gt; Around 280 ℃ nitrate. ( 3) A cooling way. Only in a single liquid quenching: workpiece coolant, cooling to the end. b。 Precooling quenching: artifacts in immersion cooling agent in the air before the appropriate cooling in order to reduce the thermal stress. c。 Double liquid quenching: artifacts general water cooling, the first to be cold to martensite near began to change, and then set out in the oil in slow cooling, cooling time in the water according to the workpiece, the effective thickness of the 3 - commonly 5 mm/s computing. d。 Interrupted quenching: artifacts into low temperature molten salt first cooling, the delay is equal to 1/3 of the total heating time - 1/2, and finally remove cooling in the air. e. Hot bath quenching: artifacts in 150 - only 180 ℃ of nitrate or alkali in cooling, residence time is equal to 1/3 of the total heating time - 1/2, and finally remove cooling in the air. f。 Isothermal quenching: artifacts in isothermal cooling in the molten salt, temperature and residence time in the molten salt according to different steel grade of austenitic isothermal transformation curve and decide, stay time should keep to the end of the austenite transformation. 4. Quenching operation for hole, hole, sharp corners, thin edge, grooves and flange parts easy to crack and slender, thin sheet, thin wall and ring parts, such as easy deformation should be organized by quality controller series, study the measures to prevent quenching crack and deformation, the general operation shall abide by the following principles. ( 1) Artifacts of the axis shape and long column should be vertically into the coolant, and strictly control the time ( Some can use roll quenching method) 。 ( 2) Tabular artifacts to vertically into the coolant. ( 3) Cylindrical thin-wall workpiece to vertically into the coolant. ( 4) A concave surface of the workpiece cooling concave upward. ( 5) Thickness of workpiece, should first dip thick parts. 5. Tempering ( 1) General parts cooled to room temperature tempering, complex shape parts to tempering in time, to prevent deformation and cracking. ( 2) Isothermal quenching workpiece is not temper.