7 Types of Thermomechanical Treatment You Should Know

Thermomechanical treatment is a metal heat treatment process that combines pressure processing with heat treatment.

It is a process method that effectively uses deformation strengthening and phase transformation strengthening on metal materials, combines pressure processing with heat treatment operations, and unifies the forming process with obtaining final properties.

Next, let’s learn about the categories and applications of thermomechanical treatment:

1. Review iron carbon phase diagram

7 Types of Thermomechanical Treatment You Should Know 1
SymbolMeaning
A1Temperature at which austenite, ferrite, cementite or carbide coexist in equilibrium
A3The highest coexistence temperature of austenite and ferrite in hypoeutectoid steel in equilibrium
Ac1Temperature at which austenite begins to form when steel is heated
Ac3The temperature at which all ferrite is transformed into austenite when hypoeutectoid steel is heated.
Ar1The temperature at which austenite decomposes into ferrite and pearlite during high temperature austenitizing and cooling of steel.
Ar3The temperature at which the cooling austenite begins to precipitate free ferrite.
AcmThe highest temperature at which austenite and cementite or carbide coexist in hypereutectoid steel in equilibrium state is the upper critical point of hypereutectoid steel.
AccmThe final temperature at which all secondary cementite dissolves into austenite during heating.
ArcmThe temperature at which austenite begins to precipitate secondary cementite during cooling.

Thermomechanical treatment

A comprehensive strengthening process combining deformation strengthening and phase transformation strengthening.

It includes two processes of plastic deformation and solid phase transformation of metal materials, which are organically combined to influence the phase transformation process and products by making use of the changes in the structure of metal materials during deformation, so as to obtain the desired structure and properties.

2. High temperature deformation hardening

7 Types of Thermomechanical Treatment You Should Know 2

Process characteristics

Deformation is carried out above Ar3 of steel or between Ar1 and Ar3 or above the solution heat treatment temperature of alloy, and then quenching and tempering are carried out.

Effect and application

Canceling reheating and quenching can increase the strength of steel by 10~30%, improve the toughness and fatigue resistance of steel, and reduce temper brittleness.

It can improve the strength and plasticity of nonferrous alloys.

It is used to produce plates, strips, pipes, wires and bars of carbon steel, low and medium alloy steel, as well as mechanical parts with simple shapes.

3. Controlled rolling

7 Types of Thermomechanical Treatment You Should Know 3

Process characteristics

The steel is deformed above Ar3 or between Ar1 and Ar3, and then air or water cooled to above 550 ℃, and then air cooled to obtain ferrite pearlite or bainite structure.

Effect and application

While increasing the yield strength, excellent low-temperature toughness can be obtained, which can be used to produce low carbon steel, non quenched and tempered weldable steel plate, strip, wire rod and other products containing Nb, V, Ti.

4. Low temperature deformation hardening

7 Types of Thermomechanical Treatment You Should Know 4

Process characteristics

The steel is deformed in the stable zone of undercooled austenite (500~600 ℃), and then quenched and tempered.

Effect and application

Under the condition of ensuring the plasticity of steel, the strength of steel can be greatly improved.

It is applicable to parts of medium alloy high strength steel with high strength requirements, steel wires of high strength steel with small section, or high alloy steel molds, high-speed steel tools, etc.

5. Isothermal deformation heat treatment

7 Types of Thermomechanical Treatment You Should Know 5

Process characteristics

(a) In the pearlite transformation temperature range of steel, deformation occurs before and during pearlite transformation;

(b) Deformation occurs after pearlite transformation.

Effect and application

(a) Fine ferrite sub grains and spherical carbides are obtained, which can improve the impact toughness of steel several times, and can be used to produce small parts of alloy structural steel;

(b) It can greatly shorten the spheroidizing process time, reduce the spheroidizing process temperature, and improve the spheroidizing structure. It is used for tool steel and bearing steel.

6. Deformation heat treatment inducing martensitic transformation

7 Types of Thermomechanical Treatment You Should Know 6

Process characteristics

Deformation is carried out in the temperature range Ms ~ Md of steel.

Effect and application

Improve the strength under the condition of ensuring plasticity.

It is applicable to austenitic stainless steel and transformation induced plasticity steel (TRIP steel).

7. Deformation aging treatment of supersaturated solid solution

7 Types of Thermomechanical Treatment You Should Know 7

Process characteristics

After solution treatment, the steel or alloy shall be cold worked or warm worked before aging.

Effect and application

The strength is significantly improved, and the necessary plasticity can still be ensured.

Used for steel grades or alloys requiring strengthening, such as austenitic steel, maraging steel, nickel base superalloy, aluminum alloy, copper alloy, etc.

8. Pre thermomechanical treatment

7 Types of Thermomechanical Treatment You Should Know 8

Process characteristics

Cold deformation is carried out at room temperature, then intermediate tempering is carried out, and secondary rapid heating quenching and final tempering are carried out.

Effect and application

It can still retain the effect of deformation strengthening, and can be used to produce cold rolled steel tubes, cold drawn high-strength steel wires, or small parts with simple shapes that can be cold formed.

Leave a Comment

Your email address will not be published. Required fields are marked *