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Why heat treatment? Analysis of screw heat treatment process

Why heat treatment? Analysis of screw heat treatment process

Screw heat treatment, we also call screw hardening. After quenching and tempering or quenching, the internal quality of the screw can be effectively improved. Next, we will introduce some common heat treatment concepts.

1 Normalizing:

The heat treatment process is to heat the steel or steel parts to an appropriate temperature above the critical point AC3 or ACM and keep it for a certain period of time and then cool it in the air to obtain a pearlite structure.

2 Annealing: The hypoeutectoid steel workpiece is heated to 20~40 degrees above AC3, and after holding for a period of time, it is slowly cooled with the furnace (or buried in sand or cooled in lime) to a heat treatment process of cooling in air below 500 degrees.

3Solid solution heat treatment: the alloy is heated to a high temperature single-phase region and maintained at a constant temperature, so that the excess phase is fully dissolved into the solid solution, and then rapidly cooled to obtain a supersaturated solid solution.

4 Aging: After the alloy is subjected to solution heat treatment or cold plastic deformation, its properties change with time when it is kept at room temperature or slightly higher than room temperature.

5Solid solution treatment: fully dissolve various phases in the alloy, strengthen the solid solution and improve toughness and corrosion resistance, eliminate stress and soften, so as to continue processing and forming

6 Aging treatment: Heating and keeping the temperature at the precipitation temperature of the strengthening phase, so that the strengthening phase is precipitated, hardened, and the strength is improved

7 Quenching: After austenitizing the steel, it is cooled at an appropriate cooling rate, so that the workpiece occurs in all or a certain range in the cross section, and the unstable structure such as martensite is transformed into a heat treatment process.

8 Tempering: Heat the quenched workpiece to an appropriate temperature below the critical point AC1 for a certain period of time, and then cool it by a method that meets the requirements to obtain the required structure and properties.

9 Carbon-ammonia co-infiltration of steel: Carbon-ammonia co-infiltration is the process of infiltrating carbon and ammonia into the surface of steel at the same time. Traditionally, carbon-ammonia co-infiltration, also known as nebulization, is currently widely used in medium-temperature gas carbon-ammonia co-infiltration and low-temperature gas carbon-atmosphere co-infiltration (ie, gas soft ammoniation). The main purpose of carbon ammonia co-infiltration in medium temperature gas is to improve the hardness, wear resistance and fatigue strength of steel. Low-temperature gas carbon-ammonia co-infiltration is mainly ammonia infiltration, and its main purpose is to improve the wear resistance and seizure resistance of steel.

10 Quenching and tempering treatment: It is generally customary to combine heat treatment with quenching and high temperature tempering as quenching and tempering treatment. Quenching and tempering treatment is widely used in various important structural parts, especially those connecting rods, bolts, gears and shafts that work under alternating loads. After quenching and tempering, the tempered sorbite structure was obtained, and its mechanical properties were better than the normalized sorbite structure with the same hardness. Its hardness depends on the high temperature tempering temperature and is related to the tempering stability of the steel and the size of the workpiece section, generally between HB200-350.

11 Brazing: A heat treatment process in which two workpieces are bonded together with brazing filler metal. The overheated screw can eliminate the defects in the blank, improve the process performance, improve the mechanical properties of the metal material, give full play to the potential of the material, save the material, and prolong the service life of the screw.