What is the national standard for the implementation of heat treatment carburizing?

National standards for the implementation of heat treatment carburizing:

1. Determination of the depth of the effective hardened layer after induction hardening or flame quenching of GB T 5617-1985 steel 4

2. GB T 9450-1988 Determination and verification of the depth of effective hardened layer in steel carburizing and quenching 4

3. GB T 9451-1988 Determination of the depth of the total hardened layer or the depth of the effective hardened layer on the thin surface of steel 5

4. GB T 9452-1988 Method for determining the effective heating zone of heat treatment furnace 13

5. GB T 11345-1989 Determination of nitriding layer depth and metallographic structure of steel parts.

Inspection 146, GB T 12603-1990 metal heat treatment process.

Classification and code 6

7. GB T 13321-1991 Steel hardness file test method 3

8. GB T 13324-1991 Terminology for heat treatment equipment.

Carburizing is generally for steel, and the carburizing of steel is that the steel parts are heated and insulated in the carburizing medium to make carbon atoms.

It penetrates into the surface of the steel to change the carbon concentration on the surface, so as to obtain a heat treatment process with a certain surface carbon content and a certain concentration gradient.

The purpose of carburizing is to achieve high surface hardness, wear resistance and high contact fatigue strength of machine parts.

and flexural fatigue strength.

Carburizing can be divided into three types: solid carburizing, liquid carburizing, and gas carburizing according to the different aggregation states of the insemint.

1. Determination of the depth of the effective hardened layer after induction hardening or flame quenching of GB T 5617-1985 steel 4

2. GB T 9450-1988 Determination and verification of the depth of effective hardened layer in steel carburizing and quenching 4

3. GB T 9451-1988 Determination of the depth of the total hardened layer or the depth of the effective hardened layer on the thin surface of steel 5

4. GB T 9452-1988 Method for determining the effective heating zone of heat treatment furnace 13

5 GB T 11345-1989 Depth determination of nitriding layer and metallographic structure inspection of steel parts 14

6 GB T 12603-1990 Metal heat treatment process classification and code 6

7. GB T 13321-1991 Steel hardness file test method 3

8. GB T 13324-1991 Terminology for heat treatment equipment.

9 GB T 15735-1995 Safety and health requirements for metal heat treatment production process 8

10 GB T 15749-1995 Quantitative Metallographic Hand Method 9

11 GB T 16923-1997 Normalizing and annealing of steel 8

12 GB T 16924-1997 Quenching and tempering of steel 10

13 GB T 17358-1998 Heat treatment production electrical energy consumption quota and method for calculation and determination thereof 6

14 GB T 7232-1999 Terminology for metal heat treatment processes.

15 GB T 18177-2000 gas nitriding of steel.

The heat treatment of carbon steel is generally quenched and tempered at low temperature after carburizing to obtain a surface layer with high hardness and a strong and tough heart. Depending on the composition of the steel, the following heat treatment methods are commonly used.

1) Pre-cooling, direct quenching and low-temperature tempering after carburizing.

This method is suitable for steels with low alloying element content and not easy to overheat, such as 20CrMnTi, 20CrTi, etc.

2) One quenching.

After carburizing, it is slowly cooled to room temperature, reheated and quenched and tempered at low temperature. It is suitable for carbon steel, low-alloy steel workpieces and solid carburized parts that are easy to overheat during carburizing.

3) Two quenching.

After carburizing, it is slowly cooled to room temperature, reheated twice, quenched and tempered at low temperature. It is suitable for intrinsically coarse-grained steel and workpieces with high performance requirements, but the production cycle is long, the cost is high, and it is easy to decarburize, oxidize and deform.

For steel grades such as 18Cr2Ni4Wa with a high degree of alloying, if pre-cooled and quenched after carburizing, there will be a large amount of residual austenite in the seepage layer, which will reduce the hardness. To this end, carburizing air cooling is used in production and then high-temperature tempering is carried out to decompose the residual austenite, and then heated quenching and low-temperature tempering are carried out.

Heat treatment and structure characteristicsThe general process route of carburized parts is: blanking, forging, normalizing, machining, carburizing, quenching + low temperature tempering, grinding. The carburizing temperature is 900 950, and the heat treatment after carburizing usually adopts direct quenching and low temperature tempering, but for steel grades that are easy to overheat during carburizing, such as Mn2, etc., it is necessary to normalize after carburizing to eliminate the superheated structure of coarse grains, and then quenching and low temperature tempering.

The quenching temperature is generally AC1+30 50. The structure in the state of use is: the surface is high-carbon tempered martensitic plus granular carbide plus a small amount of residual austenite (hardness up to HRC58 62), and the core is low-carbon tempered martensitic plus ferrite (quenched) or ferrite plus Torrosite (unquenched).

Carburizing is the process by which carbon atoms penetrate into the surface layer of steel. It is also to make the workpiece of low carbon steel have the surface layer of high carbon steel, and then after quenching and low temperature tempering, the surface layer of the workpiece has high hardness and wear resistance, while the central part of the workpiece still maintains the toughness and plasticity of the chain holding low carbon steel. Generally, the temperature of carburizing is 900 950, the quenching temperature is 800 850, the oil quenching temperature is 180 200.