CN-117512294-B - Heat treatment method for ferrite-pearlite type steel structure

Abstract

The invention discloses a ferrite-pearlite steel structure heat treatment method, relates to the technical field of metal material heat treatment, and aims to solve the technical problems that ferrite-pearlite steel treated by the existing heat treatment process is excessive in strength and insufficient in toughness. The ferrite-pearlite steel structure heat treatment method comprises the steps of heating a ferrite-pearlite steel workpiece to a temperature 30-60 ℃ higher than Ac3, and carrying out first heat preservation treatment under the temperature condition, wherein the time of the first heat preservation treatment is at least the time required for uniform temperature distribution of the steel workpiece, after the first heat preservation treatment, cooling the steel workpiece to a temperature 0-60 ℃ higher than Ac1, carrying out second heat preservation treatment, and cooling to normal temperature, wherein the time of the second heat preservation treatment is at least the time required for uniform temperature distribution of the steel workpiece. The technical scheme provided by the invention is used for carrying out heat treatment on the ferrite-pearlite steel workpiece so as to improve the toughness of the steel workpiece.

Inventors

• LI ZHENJIANG
• QI HUIPING
• YANG WEN
• DU SHIWEN
• YAN PENGTAO
• YAN JIANGTAO
• WANG YONGDONG
• PANG YOUCHAO
• Wu Pengzhe

Assignees

• 太原科技大学
• 山西富兴通重型环锻件有限公司

Dates

Publication Date

20260508

Application Date

20230926

Claims (9)

1. 1. A method for heat-treating a ferrite-pearlite structure, comprising: Heating the ferrite-pearlite steel workpiece to a temperature 30-60 ℃ higher than Ac3, and performing first heat preservation treatment under the temperature condition, wherein the time of the first heat preservation treatment is at least the time required for uniformly distributing the temperature of the steel workpiece; after the first heat preservation treatment, cooling the steel workpiece to a temperature which is 0-60 ℃ higher than Ac1, and performing second heat preservation treatment, wherein the time of the second heat preservation treatment is at least the time required for uniformly distributing the temperature of the steel workpiece; And cooling the steel workpiece subjected to the second heat preservation treatment to normal temperature to obtain the steel workpiece subjected to the heat treatment.
2. 2. The method for heat treatment of a ferrite-pearlite structure according to claim 1, characterized in that the time required for the first heat preservation treatment is: when the thickness of the steel workpiece is not more than 200mm, the required time is 0.5-4 h; Every 25mm of the steel workpiece is increased on the basis of 200mm in thickness, and the required time is increased by 0.5-1 h on the basis of 0.5-4 h.
3. 3. The method of heat treatment of a ferrite-pearlite structure according to claim 1 or 2, characterized in that the time of the second heat preservation treatment is: and when the thickness of the steel workpiece is not more than 200mm, the second heat preservation treatment time is 0.5-6 h.
4. 4. A ferrite-pearlite structure heat treatment method as set forth in claim 3, wherein the second heat-insulating treatment time is increased by 1 to 2 hours on the basis of 0.5 to 6 hours every 25mm on the basis of 200mm in thickness of the steel workpiece.
5. 5. The method for heat treatment of ferrite-pearlite structure according to claim 1, characterized in that the cooling rate in the process of cooling the steel work piece after the first heat preservation treatment to 0-60 ℃ higher than Ac1 is 20-300 ℃ per hour.
6. 6. The method for heat treatment of ferrite-pearlite structure according to claim 1, characterized in that in the process of heating the steel workpiece to a temperature 30-60 ℃ higher than Ac3, the heating rate at the time of heating is 20-300 ℃ per hour.
7. 7. The method for heat treatment of ferrite-pearlite structure according to claim 1, characterized in that in the process of cooling the steel work piece after the second heat preservation treatment to normal temperature, the cooling means is furnace cooling and/or air cooling.
8. 8. The method for heat treatment of a ferrite-pearlite structure according to claim 1, characterized by further comprising, before heating the steel workpiece to a temperature 30 to 60 ℃ higher than Ac 3: And obtaining a round bar of the steel workpiece, and detecting the upper limit austenite temperature Ac3 and/or the lower limit austenite temperature Ac1 of the round bar by using a thermal expansion method.
9. 9. The method of heat treatment of a ferrite-pearlite steel structure according to any one of claims 1 to 8, characterized in that the alloy grades of the ferrite-pearlite steel work piece include Q235, Q345, S355, 30Mn, 40MnVN, 38MnVS, 48MnV, 30MnVS, 15CrMo or 20CrMo.

Description

Heat treatment method for ferrite-pearlite type steel structure Technical Field The invention relates to the technical field of heat treatment of metal materials, in particular to a heat treatment method for ferrite-pearlite steel structure. Background The ferrite-pearlite steel has the advantages of short production period, simple process, low manufacturing cost and the like, and is one of the most widely applied steel types with the largest use amount. The existing heat treatment process of ferrite-pearlite steel mainly heats the corresponding steel workpiece to austenitizing and then directly cools the steel workpiece, the ferrite-pearlite steel treated by the traditional treatment process has higher strength, can meet the strength requirement, but has low impact toughness, particularly has poor low-temperature impact toughness, cannot meet the toughness requirement, and has potential safety hazard in the use process. Therefore, a new heat treatment process is urgently needed to solve the above technical problems. Disclosure of Invention In order to solve the technical problems that the strength of ferrite-pearlite steel treated by the existing heat treatment process is excessive and the toughness is insufficient, the invention provides a ferrite-pearlite steel tissue heat treatment method, and the invention is realized by the following technical scheme. The invention provides a ferrite-pearlite type steel structure heat treatment method, which comprises the following steps: heating a ferrite-pearlitic steel workpiece to a temperature 30-60 ℃ higher than Ac3, and performing first heat preservation treatment under the temperature condition, wherein the time of the first heat preservation treatment is at least the time required for uniformly distributing the temperature of the steel workpiece; after the first heat preservation treatment, cooling the steel workpiece to a temperature which is 0-60 ℃ higher than Ac1, and performing second heat preservation treatment, wherein the time of the second heat preservation treatment is at least the time required for uniformly distributing the temperature of the steel workpiece; And cooling the steel workpiece subjected to the second heat preservation treatment to normal temperature to obtain the steel workpiece subjected to the heat treatment. Compared with the prior art, in the ferrite-pearlite type steel structure heat treatment method, the steel workpiece is heated to the temperature of the first heat preservation treatment, namely, 30-60 ℃ higher than the Ac3 temperature, austenite of the steel workpiece can be obtained first, in the heat preservation process under the temperature condition, carbon, manganese and other elements in the steel workpiece are uniformly diffused, the stability of the steel workpiece can be improved, after the first heat preservation treatment is finished, the steel workpiece is cooled to the temperature of the second heat preservation treatment, namely, 0-60 ℃ higher than the Ac1 temperature, heat preservation treatment is carried out, the steel workpiece starts to form an austenite-ferrite two-phase structure, carbon atoms in the steel workpiece diffuse from ferrite to austenite more quickly at the temperature, the austenite carbon content is higher, and then in the cooling process, pearlite sheets generated by austenite transformation are finer, so that the toughness of the steel workpiece can be improved while the steel workpiece has excellent strength. And along with the extension of the heat preservation time, the carbon content in austenite in the steel workpiece can be further improved, so that a finer lamellar structure is formed in the subsequent cooling process, and the strength and toughness of the steel workpiece can be further improved. And cooling the steel workpiece subjected to the second heat preservation treatment to normal temperature to obtain the steel workpiece subjected to the heat treatment. By the technical scheme, the technical problems that the strength of ferrite-pearlite steel treated by the existing heat treatment process is excessive and the toughness is insufficient are solved, and the manufactured steel workpiece has the characteristics of high strength and good toughness. Further, in the ferrite-pearlite type steel structure heat treatment method of the present invention, the time required for the first heat preservation treatment is: when the thickness of the steel workpiece is not more than 200mm, the required time is 0.5-4 h; Every 25mm of the steel workpiece is increased on the basis of 200mm in thickness, and the required time is increased by 0.5-1 h on the basis of 0.5-4 h. Further, in the ferrite-pearlite type steel structure heat treatment method of the present invention, the time of the second heat-preserving treatment is: and when the thickness of the steel workpiece is not more than 200mm, the second heat preservation treatment time is 0.5-6 h. In the ferrite-pearlite type steel structure he