Several methods for straightening industrial furnaces

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　I. Cooling and straightening in industrial furnaces 　　(1) Before straightening, it is necessary to carefully check the workpiece’s specifications, verify technical parameters such as hardness, remove any dirt from the centering holes, and check whether there is any deviation in these holes. 　　(2) For rod-shaped workpieces with a general hardness of below 40HRC, cold pressing is performed on the convex surface of the workpiece at room temperature ； Cold impact on the concave surface of rod workpieces with a hardness of over 40HRC. 　　(3) Plate-shaped workpieces with a general hardness of 40HRC or higher are straightened by cold methods, while thin sheets with a hardness below 40HRC can be straightened by hammering on the front surface. 　　(4) When striking the concave surface, a hammer with appropriate hardness should be selected, and care must be taken to avoid creating very deep dents in the workpiece inside the heat treatment furnace. 　　(5) Cold hammering should be performed as much as possible on non-critical parts of the workpiece. 　　II: Quenching and straightening of industrial furnaces (1) Quenching and straightening is generally used for tools such as pullers, pushers, large-diameter drills, milling cutter shanks, and shear blades. 　　(2) For high-speed steel tools, the temperature at which calibration stops is slightly higher than room temperature. 　　(3) The shutdown temperature for carbon steel and low-alloy steel is generally around 80°C. 　　(4) During thermal calibration, careful measurements should be taken to strictly avoid sharp bends and double bends. 　　III: Thermal baking straightening of industrial furnaces (1) For high-speed steel tools that have been tempered, thermal baking straightening should be employed, using gas-air heating. 　　(2) The area to be heat-treated should preferably be a non-working area or a part that is not critical, and the heat treatment temperature should not exceed 700℃ ； When heating critical areas, the temperature must not exceed 560°C. 　　(3) After the hot-fired tool has cooled to room temperature, it should be recalibrated. 　　IV. Isothermal straightening of industrial furnaces (1) For ordinary isothermal tools, the convex surface is cold-pressed using a rack press. 　　(2) For cutting tools with a diameter greater than 16 mm, when the above method is ineffective, it is permissible to heat the drill bit grooves to no more than 560°C and press them using a screw press. 　　(3) The runout of the isothermal tool should be controlled below 0.15 mm. 　　(4) When the tool becomes brittle, straightening such a tool should be stopped. 　　V. Tempering and straightening of industrial furnaces (1) Workpieces that have been straightened through quenching are generally straightened again through tempering. 　　(2) Heat-pressing the convex surface of high-speed steel tools after tempering. 　　(3) For carbon steel and low-alloy steel, after tempering, hot-press the convex surface or strike the concave surface with a sharp hammer while it is still hot. 　　(4) For thin plate workpieces, tempering and straightening can be carried out by using clamps to apply pressure during tempering; after full heating, the parts are removed and pressure is applied again, and after the pressure is fully applied, they are held at that temperature for a certain period of time. 　　(5) For long workpieces that are difficult to straighten, such as broaches, the two convex surfaces can be pressed together; after tempering, they must be cooled to room temperature before the pressure can be removed. 　　(6) For straight-shank drill bits, pressure tempering can be carried out using a △-shaped tempering fixture. 　　VI. Straightening of hot spots in industrial furnaces (1) The straightening of hot spots in heat treatment furnaces is generally applied to carbon steel and low-alloy steel; oxygen-acetylene gas or oxygen-gas is used to address the hot spots on the protruding parts of the workpieces. Carbon steel is cooled by water, while low-alloy steel is cooled by oil or air. 　　(2) The temperature required for straightening at the hot spot varies depending on the material of the workpiece, the location of the hot spot, and the degree of bending; however, care must be taken to avoid melting the surface of the workpiece or causing quenching cracks. 　　(3) The hot spot should be located at a secondary position on the workpiece. 　　(4) For alloy steel workpieces with complex shapes or large sizes, the area surrounding the heat spot should be preheated using a flame before the heat spot is applied, with the preheating temperature not exceeding the tempering temperature; low-temperature tempering is then carried out after that. There are shortcomings; it is for reference only.