What are the methods and means of heat treatment? How are they achieved? Today, I want to give you a brief introduction to this aspect, hoping to help you.

1. heat treatment method: Different heat treatment methods can be selected according to different purposes and purposes.

Quenched and tempered steel: high temperature tempering after quenching (500-650 ℃)

Spring steel: medium temperature tempering after quenching (420-520 ℃)

Carburizing steel: quenching after carburizing, low temperature tempering (150-250 ℃)

After low-carbon steel and medium-carbon (alloy) steel are quenched into martensite, the general rule is that as the tempering temperature increases, the strength decreases, and the plasticity and toughness increase. However, due to the different carbon content of low and medium carbon steels, the tempering temperature has different effects on them. Therefore, in order to obtain good comprehensive mechanical properties, the following methods can be used:

(1) Select low-carbon (alloy) steel and temper at low temperature below 250 ℃ after quenching to obtain low-carbon martensite. In order to improve the surface wear resistance of this steel, only by increasing the carbon content of each surface layer, the surface carburizing, commonly known as carburizing structural steel.

(2) After quenching (the so-called quality adjustment treatment), medium carbon steel with high carbon content should be used and tempered at high temperature (500-650°C) to maintain sufficient strength under high plasticity conditions. Usually, this kind of steel is called quenched and tempered steel. If it is desired to obtain high strength and prefer to reduce the plasticity and toughness, low-temperature tempering can be used to carry out low-carbon content gold tempering, thereby obtaining the so-called "ultra-high-strength steel".

(3) for the carbon content between the high carbon (such as 60,70 steel) and some high carbon steel (such as 80,90 steel) between the steel, if used in the manufacture of spring, in order to ensure high elastic limit, yield limit and fatigue limit, quenching after the use of medium temperature tempering.

Suzhou Heat Treatment

2. operation process:

(1) tempered steel:

1. Pre-heat treatment: normalizing-> annealing (pearlitic steel)-> high temperature tempering (martensitic steel)

(1) The purpose of normalizing is to refine the grains, reduce the degree of banding in the organization, adjust the hardness, and facilitate mechanical processing. After normalizing, the steel has equiaxed fine grains.

2. Quenching: The steel body is heated to 850°C for quenching. The quenching medium can be selected according to the size of the steel part and the hardenability of the steel. In general, water, oil or even air may be selected for quenching. The steel in the quenched state has low plasticity and high internal stress.

3. Tempering:

(1) In order to make the steel have high plasticity, toughness and appropriate strength, the steel should be tempered at a high temperature of about 400-500°C. Steels that are more sensitive to temper brittleness should be cooled rapidly after tempering to suppress the occurrence of temper brittleness.

(2) If the parts are required to have particularly high strength, temper at about 200°C to obtain a medium-carbon tempered martensite structure.

(3) Spring steel:

1. Quenching: oil quenching at 830-870 ℃.

2. Tempering: Tempering at 420-520°C to obtain tempered troostite tissue.

(4) Carburizing steel:

1. Carburizing: A chemical heat treatment, which refers to the penetration of element C into the surface of steel parts in an active medium containing certain chemical elements at a certain temperature. Partial preheating (850 ℃) carburizing (890 ℃) diffusion (840 ℃) process

2. Quenching: Carbon and low-alloy carburized steels are usually quenched directly or once.

3. Tempering: low temperature tempering, eliminate internal stress, improve the strength and toughness of carburized layer. The tempering temperature of the middle tooth thread produced by our company is about 360 ℃, and the tempering temperature of the self-tapping screw (wall plate nail) is about 200 ℃, and then it is cooled to 34-35 ℃ and 39-40 ℃ respectively. Back to Sohu to see more