阅读说明：本技术 一种提高h13钢综合力学性能的热处理工艺 (Heat treatment process for improving comprehensive mechanical property of H13 steel ) 是由 王岳峰 王天生 史新琦 孙晓文 于 2020-08-12 设计创作，主要内容包括：本发明公开了一种提高H13钢综合力学性能的热处理工艺,属于热处理工艺技术领域,包括球化退火、正火、球化退火、等温淬火和回火五个步骤。本发明的工艺可以提高H13钢的综合力学性能,并且工艺流程简单,易于控制,有利于实现工业化生产。(The invention discloses a heat treatment process for improving comprehensive mechanical property of H13 steel, belonging to the technical field of heat treatment processes and comprising five steps of spheroidizing annealing, normalizing, spheroidizing annealing, isothermal quenching and tempering. The process can improve the comprehensive mechanical property of the H13 steel, has simple process flow and easy control, and is beneficial to realizing industrial production.)

1. A heat treatment process for improving comprehensive mechanical properties of H13 steel is characterized by comprising the following steps:

(1) and spheroidizing annealing: putting H13 steel into a heating furnace, heating to 885-895 ℃ along with the furnace, preserving heat for 1-1.5H, cooling to 745-755 ℃ along with the furnace, preserving heat for 1-1.5H, cooling to 500 ℃ along with the furnace, and then discharging from the furnace for air cooling;

(2) normalizing: putting the H13 steel subjected to the heat treatment in the step (1) into a heating furnace, heating the H13 steel to 975-985 ℃ along with the furnace, preserving the heat for 1-1.5H, and then discharging the H13 steel out of the furnace and air cooling;

(3) and spheroidizing annealing: putting the H13 steel subjected to the heat treatment in the step (2) into a heating furnace, heating the H13 steel to 885-895 ℃ along with the furnace, preserving heat for 1-1.5H, cooling the H13 steel to 745-755 ℃ along with the furnace, preserving heat for 1-1.5H, cooling the H13 steel to 500 ℃ along with the furnace, and then discharging the H13 steel out of the furnace for air cooling;

(4) and isothermal quenching: putting the H13 steel subjected to the heat treatment in the step (3) into a heating furnace, heating to 1020-1040 ℃ along with the furnace, preserving heat for 20-30 min, then quickly cooling to 310-355 ℃ in a salt bath furnace, preserving heat for 3-5H, discharging and air cooling;

(5) and tempering: and (3) putting the H13 steel subjected to the heat treatment in the step (4) into a heating furnace, heating to 555-565 ℃, preserving heat for 1-1.5H, discharging from the furnace, air cooling, then putting into the heating furnace, heating to 575-585 ℃, preserving heat for 1-1.5H, discharging from the furnace, and air cooling.

2. The heat treatment process for improving the comprehensive mechanical property of the H13 steel according to claim 1, wherein the Charpy U-notch impact energy of the H13 steel after the isothermal quenching heat treatment in the step (4) is 27-40J.

3. The heat treatment process for improving the comprehensive mechanical property of the H13 steel according to claim 1, wherein the unnotched impact energy of the H13 steel after the isothermal quenching heat treatment in the step (4) is not less than 392J.

4. The heat treatment process for improving the comprehensive mechanical property of the H13 steel according to claim 1, wherein the Rockwell hardness of the H13 steel subjected to the isothermal quenching heat treatment in the step (4) is 51-53.6 HRC.

5. The heat treatment process for improving the comprehensive mechanical property of the H13 steel according to claim 1, wherein the tensile strength of the H13 steel after the isothermal quenching heat treatment in the step (4) is 2002-2224 MPa, and the elongation is 10.8-16.2%.

6. The heat treatment process for improving the comprehensive mechanical property of the H13 steel according to claim 1, wherein the Charpy U-notch impact energy of the H13 steel after the tempering heat treatment in the step (5) is 14-16J.

7. The heat treatment process for improving the comprehensive mechanical property of the H13 steel as claimed in claim 1, wherein the Rockwell hardness of the H13 steel after the tempering heat treatment in the step (5) is 52.9-53.4 HRC.

Technical Field

The invention relates to a heat treatment process, in particular to a heat treatment process for improving comprehensive mechanical properties of H13 steel.

Background

The H13 steel is under the mark of 4Cr5MoSiV1 in China. The H13 steel is a chromium-based hot-work die steel having excellent hardenability, and can be quench-hardened when cooled in air. The steel is widely used for industrial manufacture due to excellent hardenability and toughness, but the prior H13 steel subjected to conventional heat treatment has relatively poor comprehensive mechanical properties, and the Rockwell hardness is 52 HRC, AK_U10J, standard nothingThe impact work of the mouth impact test piece is about 300J.

In order to improve the strength and the toughness of H13 steel, Chinese patent with application number 201910602981.X discloses high-toughness high-crack-resistance hot-work die steel and a manufacturing method thereof, wherein the Rockwell hardness is 45-48 HRC, the impact energy of a standard unnotched impact specimen is more than or equal to 350J, and the tensile strength is more than or equal to 1350 MPa. The Chinese patent with the application number of 201910216546.3 discloses H13 die steel and a production method thereof, and the impact energy of the standard unnotched impact specimen is more than or equal to 280J.

Disclosure of Invention

The invention aims to provide a heat treatment process for improving comprehensive mechanical properties of H13 steel and improve comprehensive mechanical properties of H13 steel.

In order to solve the technical problems, the invention adopts the technical scheme that: a heat treatment process for improving comprehensive mechanical properties of H13 steel comprises the following steps:

(1) and spheroidizing annealing: putting H13 steel into a heating furnace, heating to 885-895 ℃ along with the furnace, preserving heat for 1-1.5H, cooling to 745-755 ℃ along with the furnace, preserving heat for 1-1.5H, cooling to 500 ℃ along with the furnace, and then discharging from the furnace for air cooling;

(2) normalizing: putting the H13 steel subjected to the heat treatment in the step (1) into a heating furnace, heating the H13 steel to 975-985 ℃ along with the furnace, preserving the heat for 1-1.5H, and then discharging the H13 steel out of the furnace and air cooling;

(3) and spheroidizing annealing: putting the H13 steel subjected to the heat treatment in the step (2) into a heating furnace, heating the H13 steel to 885-895 ℃ along with the furnace, preserving heat for 1-1.5H, cooling the H13 steel to 745-755 ℃ along with the furnace, preserving heat for 1-1.5H, cooling the H13 steel to 500 ℃ along with the furnace, and then discharging the H13 steel out of the furnace for air cooling;

(4) and isothermal quenching: putting the H13 steel subjected to the heat treatment in the step (3) into a heating furnace, heating to 1020-1040 ℃ along with the furnace, preserving heat for 20-30 min, then quickly cooling to 310-355 ℃ in a salt bath furnace, preserving heat for 3-5H, discharging and air cooling;

(5) and tempering: and (3) putting the H13 steel subjected to the heat treatment in the step (4) into a heating furnace, heating to 555-565 ℃, preserving heat for 1-1.5H, discharging from the furnace, air cooling, then putting into the heating furnace, heating to 575-585 ℃, preserving heat for 1-1.5H, discharging from the furnace, and air cooling.

The technical route of the method is as follows: the H13 steel is heated to 1030 ℃ for austenitization after the preliminary heat treatment of spheroidizing annealing, normalizing and spheroidizing annealing, then is put into a salt bath furnace with the temperature near the martensite start transformation point of austenite for isothermal bainite transformation, and then is air-cooled to room temperature to obtain a nano bainite structure.

The physical metallurgy principle of the method is as follows: heating the H13 steel blank to a temperature above Ac1 to dissolve irregular carbides in the original structure, and then cooling the H13 steel blank to a temperature below Ac1 to spheroidize the carbides. Heating the spheroidizing annealed H13 steel to a temperature above Ac3 in the subsequent normalizing process, preserving the heat, further dissolving irregular carbides into a matrix, changing the form and distribution of the carbides, performing air cooling to obtain a martensite structure, and then performing spheroidizing annealing once again to obtain fine and uniformly distributed spherical carbides in the H13 steel matrix structure. And then, after austenitizing and holding the H13 steel subjected to the preliminary heat treatment for a period of time, carrying out bainite transformation in the process of carrying out low-temperature (near the martensite start transformation point of austenite) isothermal quenching in a salt bath furnace, wherein thin-film austenite is distributed among bainite laths because Si element inhibits the precipitation of carbide in the isothermal transformation process, and the width of the bainite laths is reduced, namely nano bainite is formed. And the mechanical property of the nanometer bainite is very excellent, so that the comprehensive mechanical property of the H13 steel can be improved.

The pre-heat treatment of spheroidizing annealing, normalizing and spheroidizing annealing mainly has two functions: firstly, the hardness of the H13 steel can be reduced through the pretreatment, so that the H13 steel is convenient to cut and form and is prepared for subsequent heat treatment; secondly, H13 steel obtains spherical carbide with high spheroidization rate and dispersion distribution after the pretreatment. During the subsequent heat treatment, the spherical undissolved carbide can pin the grain boundary, prevent the growth of austenite grains and play the role of fine grain strengthening. Meanwhile, the spherical carbide distributed in a dispersion mode can passivate the crack tip, change the crack path, slow down the crack propagation and improve the toughness of the steel.

The nano bainite steel is more resistant to tempering than martensite steel, the strength and hardness of the nano bainite steel have smaller dependence on solid solution strengthening of carbon, and the thickness of bainite ferrite laths determines the overall strength. The traditional H13 steel adopts the heat treatment process of quenching and twice tempering to obtain a tempered martensite structure, in the tempering process, high-over-saturated carbon atoms are precipitated in the tempered martensite in the form of carburized particles, and the dislocation density of the martensite is also obviously reduced, so that the strength and hardness of the tempered martensite are sharply reduced along with the precipitation of cementite and the reduction of the dislocation density. The hardness of the nano bainite steel is not obviously reduced in a short-time tempering process, because the film-shaped residual austenite in the structure is decomposed into cementite and ferrite, carbide is precipitated at the boundary of bainite ferrite laths, and the precipitated carbide is pinned at the boundary to prevent the ferrite laths from coarsening and growing. As the strength and hardness of the nano bainite steel are mainly derived from the small thickness of bainite ferrite laths, the steel can resist the loss of hardness and strength, and therefore, the structure obtained by the H13 steel after being treated by the heat treatment process has better tempering performance and longer service life than the structure obtained by the heat treatment process of traditional quenching and twice tempering.

The invention has the beneficial effects that: 1. the comprehensive mechanical property of H13 steel is improved, the Charpy U-shaped notch impact energy of the H13 steel after isothermal quenching is 27-40J, the standard unnotched impact energy is more than or equal to 392J, the Rockwell hardness is 51-53.6 HRC, the tensile strength is 2002-2224 MPa, and the elongation is 10.8-16.2%; the standard Charpy U-shaped notch impact energy of the tempered H13 steel is 14-16J, the Rockwell hardness is 52.9-53.4 HRC, and the comprehensive mechanical properties of the heat-treated H13 steel are superior to those of the conventional heat-treated H13 steel; 2. the process flow is simple, easy to control and beneficial to realizing industrial production.

The present invention will be described in detail with reference to the accompanying drawings.

Drawings

FIG. 1 is a process diagram of heat treatment according to examples 1 to 6 of the present invention;

FIG. 2 is a tensile curve of H13 steel prepared in example 1;

FIG. 3 is a tensile curve of H13 steel prepared in example 2;

fig. 4 is a tensile curve of H13 steel prepared in example 3.

Detailed Description

The invention relates to a heat treatment process for improving comprehensive mechanical properties of H13 steel, which comprises the following steps.

(1) And spheroidizing annealing: putting H13 steel into a heating furnace, heating to 885-895 ℃ along with the furnace, preserving heat for 1-1.5H, cooling to 745-755 ℃ along with the furnace, preserving heat for 1-1.5H, cooling to 500 ℃ along with the furnace, and then discharging from the furnace for air cooling.

(2) Normalizing: and (2) putting the H13 steel subjected to the heat treatment in the step (1) into a heating furnace, heating to 975-985 ℃ along with the furnace, preserving heat for 1-1.5H, and then discharging from the furnace and air cooling.

(3) And spheroidizing annealing: and (3) putting the H13 steel subjected to the heat treatment in the step (2) into a heating furnace, heating to 885-895 ℃ along with the furnace, preserving heat for 1-1.5H, cooling to 745-755 ℃ along with the furnace, preserving heat for 1-1.5H, cooling to 500 ℃ along with the furnace, and then discharging from the furnace for air cooling.

(4) And isothermal quenching: and (4) putting the H13 steel subjected to the heat treatment in the step (3) into a heating furnace, heating to 1020-1040 ℃ along with the furnace, preserving heat for 20-30 min, then quickly cooling to 310-355 ℃ in a salt bath furnace, preserving heat for 3-5H, discharging from the furnace, and air cooling.

(5) And tempering: and (3) putting the H13 steel subjected to the heat treatment in the step (4) into a heating furnace, heating to 555-565 ℃, preserving heat for 1-1.5H, discharging from the furnace, air cooling, then putting into the heating furnace, heating to 575-585 ℃, preserving heat for 1-1.5H, discharging from the furnace, and air cooling.

The present invention will be described in detail with reference to specific examples.