Several common heat treatment methods

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Normalizing: steel or steel parts are heated to an appropriate temperature higher than AC3 or ACM critical point for a certain time, and then cooled in air to obtain pearlite structure;

Annealing: the hypoeutectoid steel workpiece is heated to 20-40 ℃ higher than AC3, then slowly cooled in furnace (or buried in sand or lime) to below 500 ℃, and cooled in air after holding for a period of time;

Solution heat treatment: the alloy is heated to high temperature, the single phase region is kept at constant temperature, so that the excess phase is completely dissolved in the solid solution, and then quickly cooled to obtain supersaturated solid solution;

Aging: after solution heat treatment or cold plastic deformation, the properties of the alloy will change with time at or slightly above room temperature;

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

Aging treatment: heating at the precipitation temperature of strengthening phase and keeping the temperature to precipitate strengthening phase, harden and improve the strength;

Quenching: This is a heat treatment process in which the steel is austenitized and cooled at an appropriate cooling rate, resulting in unstable structural transformation such as martensite in the whole or specific section of the workpiece;

Tempering: a heat treatment process in which the quenched workpiece is heated to an appropriate temperature below the critical point AC1 for a certain period of time and then cooled in a satisfactory manner to obtain the required microstructure and properties;

Carbonitriding of steel: carbonitriding is a process in which carbon and nitrogen penetrate into the steel surface at the same time. Carbonitriding, also known as cyaniding, is widely used in medium temperature gas carbonitriding and low temperature gas carbonitriding. The main purpose of medium temperature gas carbonitriding is to improve the hardness, wear resistance and fatigue strength of steel. The main purpose of low temperature gas carbonitriding is to improve the wear resistance and bite resistance of steel.

Quenching and tempering: the combination of quenching and high temperature tempering is usually called quenching and tempering. Quenching and tempering are widely used in various important structural parts, especially for connecting rods, bolts, gears and shafts working under alternating loads. At the same hardness, the mechanical properties of tempered sorbite are better than that of normalized sorbite. Its hardness depends on the high temperature tempering temperature, and is related to the tempering stability of the steel and the cross-section size of the workpiece, usually between hb200 and 350.

Brazing: a heat treatment process in which two workpieces are bonded to the filler metal.

Vacuum heat treatment furnace