CN110791620A

CN110791620A - Superfine heat treatment method for hot-work die steel

Info

Publication number: CN110791620A
Application number: CN201911258529.2A
Authority: CN
Inventors: 叶国梁; 陈雨飞
Original assignee: HUBEI RISHENG TECHNOLOGY Co Ltd
Current assignee: HUBEI RISHENG TECHNOLOGY Co Ltd
Priority date: 2019-12-10
Filing date: 2019-12-10
Publication date: 2020-02-14
Anticipated expiration: 2039-12-10
Also published as: CN110791620B

Abstract

The application discloses a superfine heat treatment method for hot-work die steel, which comprises the following steps: after forging, carrying out spheroidizing annealing and superfine quenching, wherein the quenching temperature is 1040-1060 ℃, the medium is water, and the time is 10-100 min; and the spheroidizing annealing is carried out at the temperature of 860-900 ℃ for 10-24 h. The invention adopts water AS a medium to carry out quenching treatment through superfine heat treatment, and the hot-work die rigid strip structure after the superfine heat treatment can not only meet the requirements of international standards, but also basically meet the requirements of eight grades of SA-SB series strip structures, and the spheroidized structure can meet the requirements of five grades of AS 1-AS 5.

Description

Superfine heat treatment method for hot-work die steel

Technical Field

The application relates to the technical field of metal heat treatment, in particular to a superfine heat treatment method for hot work die steel.

Background

The hot working die is mainly used for hot deformation processing and pressure casting. After the hot working die is forged, heat treatment is performed. Heat treatment is an important step essential for the production of hot-work molds. The heat treatment aims to change the structure of the steel and improve the mechanical properties such as hardness, toughness and the like by heating and cooling. Different heat treatment processes are adopted for different hot working dies so as to achieve the required service performance. Heat treatment has a significant impact on both the quality and the service life of hot work dies.

After the hot die steel is forged, spheroidizing annealing is carried out to ensure certain hardness, and a semi-finished product can be formed by surface cleaning and tolerance control. 5H12, H13 and 8418 are not good in forging temperature control, mainly have high forging temperature, cause chain and net structures after forging, coarse crystal grains and uneven metallographic structures, and cannot improve the poor structure state after annealing. The actual service life of the steel will be reduced to a great extent. Along with the improvement of quality requirements of users, the current quality phenomenon can not meet the requirements of the users, and the metallographic structure after spheroidizing annealing is required to be controlled to a certain extent. The North America NADCA # 207-: the strip structure is required to reach SA-SD 16 qualified grades, and the spheroidized structure is required to reach 25 qualified grades of nine qualified grades of AS 1-AS 9, but the spheroidized annealed structure after forging is difficult to reach the requirements specified by the standard.

The requirement of the standard can be met by adopting an ultra-fining and spheroidizing annealing process. However, the steel is quenched by using water as a quenching medium, so that the quenching is stronger than that of oil, and is environment-friendly. But poor control easily causes the condition that the steel is cracked and scrapped.

Therefore, it is a subject to be studied whether or not ultrafine quenching can be achieved using water as a medium.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a superfine heat treatment method for hot die steel. The process can be perfectly carried out by taking water as a medium through the change of the process conditions.

A hot-work die steel superfine heat treatment method comprises the steps of carrying out spheroidizing annealing and superfine quenching after forging, wherein the superfine quenching is carried out at the quenching temperature of 1040-1060 ℃ and the medium of water for 10-100 min;

further, the concrete steps of the ultra-fine quenching are as follows: isothermal preheating is carried out at the temperature of 660-680 ℃; then raising the temperature to 1060 ℃, preserving the heat for more than 8 hours, and then placing the mixture in water for cooling.

Further, the temperature rise rate is 1-2 ℃/min,

further, the ultra-fine quenching is carried out under the condition of filling inert gas.

Further, the ultra-fine quenching is carried out under the action of ultrasonic waves.

Furthermore, the power of the ultrasonic wave is 500-1000W, and the frequency of the ultrasonic wave is 20-25 kHz.

Further, the spheroidizing annealing specifically comprises the steps of controlling the temperature to 880 ℃, preserving heat for 5-10 hours, then rapidly cooling to 650-690 ℃, and preserving heat for 4-8 hours.

Further, the rapid cooling is carried out at a cooling speed of 20-50 ℃/s.

Has the advantages that: the invention adopts water AS a medium to carry out quenching treatment through superfine heat treatment, and the hot-work die rigid strip structure after the superfine heat treatment can not only meet the requirements of international standards, but also basically meet the requirements of eight grades of SA-SB series strip structures, and the spheroidized structure can meet the requirements of five grades of AS 1-AS 5.

The invention further improves and combines the ultrasonic processing method, the process can eliminate the tissue inheritance of the alloy steel and improve the effect of the tissue uniformity, and the ultrasonic quenching process can generate cavitation and acoustic flow effect, accelerate the cooling speed of the sample, and ensure that the grain size is finer and more uniform compared with the conventional quenching process.

The hot die steel treated by the method has obviously higher mechanical properties, such as strength, toughness and other performance values than those without ultrafine treatment.

Drawings

FIG. 1 is a metallographic structure diagram of H13 round steel before being untreated

FIG. 2 is a metallographic structure diagram of H13 round steel after treatment

FIG. 3 is a metallographic structure diagram of an 8418 plate before being untreated

FIG. 4 is a metallographic structure diagram of 8418 plate after treatment

FIG. 5 is a metallographic structure diagram of 5H12 round steel before being untreated

FIG. 6 is a metallographic structure diagram of a processed 5H12 round steel

Detailed Description

In order to make the technical solution of the present application better understood, the technical solution of the present application will be clearly and completely described below with reference to the embodiments of the present application.

Example 1

The H13 round steel is used as a treatment object, and the metallographic structure of the H13 round steel before treatment is shown in figure 1. (AS15 grade 500X)

After forging, under the condition of filling inert gas, controlling the temperature to 860 ℃, preserving heat for 5h, then rapidly cooling (the cooling speed is 20 ℃/s) to 650 ℃, and preserving heat for 6 h; isothermal preheating is carried out, and the preheating temperature is 660 ℃; rapidly heating to 1060 deg.C (with heating rate of 1 deg.C/min), maintaining for 20min, cooling to below 1050 deg.C, placing in water, and cooling. And finally cooling with the furnace to below 400 ℃.

The metallographic structure of the H13 round steel processed by the steps is shown in figure 2. (AS3 grade 500X)

Example 2

The 8418 plate is taken as a treatment object, and the metallographic structure of the 8418 plate before treatment is shown in fig. 3. (AS18 grade 500X)

After forging, under the condition of filling inert gas, firstly controlling the temperature to 880 ℃, preserving heat for 10h, then quickly cooling (the cooling speed is 50 ℃/s) to 690 ℃, preserving heat for 8h, then carrying out isothermal preheating, quickly heating (the heating speed is 2 ℃/min) to 1060 ℃, preserving heat for 60min, then reducing the temperature to below 1050 ℃, putting into water, and cooling.

The metallographic structure of the 8418 plate processed in the steps is shown in fig. 4. (AS2 grade 500X)

Example 3

The 5H12 round steel was treated, and the microstructure of the 5H12 round steel before treatment was shown in fig. 5. (AS13 grade 500X)

After forging, under the condition of filling inert gas, firstly controlling the temperature to be 890 ℃, preserving the heat for 6h, then quickly cooling (the cooling speed is 50 ℃/s) to 680 ℃, preserving the heat for 7h, and then carrying out isothermal preheating, wherein the preheating temperature is 1010 ℃; rapidly heating to 1060 deg.C (temperature rising rate of 2 deg.C/min), maintaining for 30min, cooling to below 1050 deg.C, placing in water, and cooling.

The metallographic structure of the 5H12 round steel processed by the steps is shown in FIG. 6. (AS2 grade 500X)

It can be seen from the tests of examples 1 to 3. Compared with the hot work die steel treated by the method before treatment, the hot work die steel has obviously finer and more uniform particles.

Example 4

H13 round steel is taken as a processing object, after forging, under the condition of filling inert gas, the temperature is firstly controlled at 885 ℃, the temperature is kept for 5H, then the round steel is rapidly cooled (the cooling speed is 20 ℃/s) to 650 ℃, and the temperature is kept for 6H. Isothermal preheating is carried out at 660 ℃, and the preheating temperature is 1010 ℃; rapidly heating to 1060 deg.C (heating rate of 1 deg.C/min), maintaining for 20min, cooling to 1050 deg.C or below, cooling in water, and performing ultrasonic treatment (ultrasonic power of 800W and ultrasonic frequency of 25 kHz).

Example 5

The 8418 plate is taken as a processing object, after forging, under the condition of filling inert gas, the temperature is controlled at 900 ℃, the temperature is kept for 10 hours, then the forging steel plate is rapidly cooled (the cooling speed is 50 ℃/s) to 690 ℃, and the temperature is kept for 8 hours. Then isothermal preheating is carried out, the preheating temperature is 680 ℃, then rapid heating (the temperature rising speed is 2 ℃/min) is carried out to 1060 ℃, heat preservation is carried out for 60min, then the temperature is reduced to below 1050 ℃, the mixture is placed in water for cooling, and ultrasonic treatment is carried out simultaneously (the ultrasonic power is 800W, and the ultrasonic frequency is 25 kHz).

Example 6

The method comprises the steps of using 5H12 round steel as a processing object, controlling the temperature at 880 ℃, preserving heat for 6H after forging under the condition of filling inert gas, then quickly cooling (the cooling speed is 50 ℃/s) to 680 ℃, preserving heat for 7H, carrying out isothermal preheating, quickly heating (the heating speed is 2 ℃/min) to 1060 ℃, preserving heat for 30min, then reducing the temperature to below 1050 ℃, placing in water for cooling, and simultaneously carrying out ultrasonic processing (the ultrasonic power is 800W, and the ultrasonic frequency is 25 kHz).

Example 7

And (5) testing mechanical properties. Mechanical property tests were performed on the products treated in examples 1 to 6. The results obtained were as follows: example 1 impact toughness of 10.3J/cm²Example 4 impact toughness of 12.1J/cm²Example 2, impact toughness 23.8J/cm²Example 5 impact toughness of 33.1J/cm²Example 3 impact toughness of 30.2J/cm²Example 6 has an impact toughness of 38.0J/cm²，

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A superfine heat treatment method for hot die steel is characterized in that spheroidizing annealing and superfine quenching are carried out after forging, wherein the superfine quenching is carried out at the quenching temperature of 1040-1060 ℃ and the medium of water for 10-100 min.

2. The method for ultrafining heat treatment of hot work die steel as claimed in claim 1, wherein the concrete steps of the ultrafining quenching are: isothermal preheating is carried out at the temperature of 660-680 ℃; then raising the temperature to 1060 ℃, preserving the heat for more than 8 hours, and then placing the mixture in water for cooling.

3. The method of claim 2, wherein the temperature is raised at a rate of 1 to 2 ℃/min.

4. The method for ultrafinely heat treating a hot die steel as claimed in claim 1, wherein the ultrafinely quenching is performed under the condition filled with an inert gas.

5. The method for ultrafinely heat treating a hot work die steel as claimed in claim 1, wherein the ultrafinely quenching is performed by the ultrasonic waves.

6. The method of claim 5, wherein the ultrasonic power is 500-1000W and the ultrasonic frequency is 20-25 kHz.

7. The method for ultrafine heat treatment of hot work die steel according to claim 1, wherein the spheroidizing annealing is carried out by controlling the temperature to 880 ℃, keeping the temperature for 5-10 hours, then rapidly cooling to 650-690 ℃, and keeping the temperature for 4-8 hours.

8. The method of claim 7, wherein the rapid cooling is performed at a cooling rate of 20 to 50 ℃/s.