CN110923584B

CN110923584B - Long-life die-casting die steel and heat treatment process thereof

Info

Publication number: CN110923584B
Application number: CN201911409031.1A
Authority: CN
Inventors: 雷佳乐; 朱裕华
Original assignee: Chongqing Youte Mould Co ltd
Current assignee: Chongqing Youte Mould Co ltd
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2022-04-05
Anticipated expiration: 2039-12-31
Also published as: CN110923584A

Abstract

The invention discloses long-life die-casting die steel which comprises the following components in percentage by mass: c: 0.33% -0.41%, Si: not more than 0.5%, Mn: not more than 0.5%, Cr: 4.8% -5.5%, Mo: 2.0% -2.4%, V: 0.3% -0.8%, Ni: not more than 0.40% and the balance Fe and unavoidable impurities; compared with the prior art, the invention has the advantages of excellent heat conduction performance, toughness and ductility, small heat deformation amount and greatly prolonged service life of the die steel.

Description

Long-life die-casting die steel and heat treatment process thereof

Technical Field

The invention relates to the technical field of die steel, in particular to long-life die-casting die steel and a heat treatment process thereof.

Background

The die steel is a steel grade used for manufacturing dies such as cold-stamping dies, hot-stamping dies and die-casting dies. The die is a main processing tool for manufacturing parts in industrial departments of mechanical manufacturing, radio instruments, motors, electric appliances and the like. The quality of the die directly affects the quality of the pressure processing technology, the precision yield of products and the production cost, and the quality and the service life of the die are mainly affected by die materials and heat treatment except by reasonable structural design and processing precision.

The existing die steel (such as 1.2344 type die steel) has the problems of large heat deformation, poor heat conduction performance, poor toughness and ductility, and short service life of the die after the die steel is processed and formed.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide the die-casting die steel with long service life, which aims to solve the problem that the service life of a die is short after the die is processed and formed due to the problems of large thermal deformation, poor heat conduction performance, poor toughness and ductility in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme: the long-life die-casting die steel comprises the following components in percentage by mass:

C：0.33％-0.41％、

si: not more than 0.5 percent,

Mn: not more than 0.5 percent,

Cr：4.8％-5.5％、

Mo：2.0％-2.4％、

V：0.3％-0.8％、

Ni: not more than 0.40 percent,

The balance being Fe and unavoidable impurities.

Compared with the prior art, the invention has the following beneficial effects:

after all the components are processed and prepared according to a certain proportion, compared with a similar product (1.2344 type die steel), the long-life die-casting die steel has excellent heat conduction performance, toughness and ductility, is small in heated deformation amount, and greatly prolongs the service life of the die steel.

Drawings

FIG. 1 is a metallographic structure of a long-life die casting die steel of sample 1;

FIG. 2 is a metallographic structure of a long-life die casting mold steel of sample 2;

FIG. 3 is a metallographic structure of a long-life die casting mold steel of sample 3;

FIG. 4 is a metallographic structure of a long life die casting mold steel of sample 4;

FIG. 5 is a metallographic structure of a long life die casting mold steel of sample 5;

FIG. 6 is a metallographic structure of a long life die casting mold steel of sample 6;

FIG. 7 is a metallographic structure of a long life die casting mold steel of sample 7;

FIG. 8 is a CCT plot of a long life die casting mold steel of sample 3;

FIG. 9 is a graph showing the tempering characteristics of the long life die casting die steel of sample 3.

Detailed Description

The present invention will be described in further detail below by way of specific embodiments:

examples

Table 1: components in the sample die Steel (wt%)

TABLE 1

Test specimen	C	Si	Mn	Cr	Mo	V	Ni	P	S	H	Fe
													1	0.33	0.5	0.5	4.8	2	0.3	0.4	0.015	0.003	2ppm	Balance of
2	0.41	0.1	0.2	5.5	2.4	0.8	0.1	0.005	0.001	1ppm	Balance of
												3	0.36	0.4	0.35	5	2.2	0.5	0.3	0.01	0.001	2ppm	Balance of
4	0.38	0.23	0.48	4.92	2.1	0.7	0.26	0.012	0.003	1ppm	Balance of
												5	0.35	0.42	0.16	5.12	2.3	0.6	0.32	0.013	0.002	1.6ppm	Balance of
6	0.4	0.36	0.1	5.38	2.26	0.56	0.18	0.006	0.0015	0.9ppm	Balance of
												7	0.37	0.16	0.41	5.26	2.35	0.32	0.38	0.008	0.0026	1.3ppm	Balance of

The sample 1 was subjected to the heat treatment according to the following procedure:

firstly, pressurizing a die steel ingot by a forging machine, wherein the initial forging temperature of the die steel ingot is 1020 ℃, preserving heat for 20 hours, and then cooling to ensure that the final forging temperature of the die steel ingot is 850 ℃, and preserving heat for 14 hours;

then transferring the steel ingot of the mold into an annealing furnace with the temperature of 840 ℃, reducing the temperature in the annealing furnace to 810 ℃ at the cooling speed of 7 ℃/h, and then carrying out air cooling;

then putting the steel ingot of the mold into a quenching furnace with the temperature of 1040 ℃, preserving the heat for 5 hours, and then reducing the temperature in the quenching furnace to 1000 ℃ within 80 s;

and finally, putting the steel ingot of the mold into a tempering furnace with the temperature of 530 ℃, preserving the heat for 5 hours, and then cooling to the room temperature.

The sample 2 was subjected to the heat treatment according to the following procedure:

firstly, pressurizing a die steel ingot by a forging machine, wherein the initial forging temperature of the die steel ingot is 1070 ℃, preserving heat for 16 hours, and then cooling to ensure that the final forging temperature of the die steel ingot is 880 ℃, and preserving heat for 10 hours;

then transferring the steel ingot of the mold to an annealing furnace with the temperature of 850 ℃, reducing the temperature in the annealing furnace to 820 ℃ at the cooling speed of 9 ℃/h, and then carrying out air cooling;

then putting the steel ingot of the die into a quenching furnace with the temperature of 1050 ℃, preserving the heat for 3 hours, and then reducing the temperature in the quenching furnace to 1010 ℃ within 60 seconds;

and finally, putting the steel ingot of the mold into a tempering furnace at 680 ℃, preserving heat for 4 hours, and then cooling to room temperature.

The heat treatment of sample 3 was carried out according to the following steps:

firstly, pressurizing a die steel ingot by a forging machine, wherein the initial forging temperature of the die steel ingot is 1060 ℃, preserving heat for 16.5 hours, then cooling to ensure that the final forging temperature of the die steel ingot is 870 ℃, and preserving heat for 11 hours;

then transferring the steel ingot of the mold to an annealing furnace with the temperature of 846 ℃, then reducing the temperature in the annealing furnace to 814 ℃ at the cooling speed of 8 ℃/h, and then carrying out air cooling;

then placing the steel ingot of the mold into a quenching furnace with the temperature of 1045 ℃, preserving the heat for 4 hours, and then reducing the temperature in the quenching furnace to 1010 ℃ within 70 s;

and finally, putting the steel ingot of the mold into a tempering furnace at the temperature of 600 ℃, preserving heat for 4.5 hours, and then cooling to room temperature.

The heat treatment of sample 4 was carried out according to the following steps:

pressurizing a die steel ingot by a forging machine, wherein the initial forging temperature of the die steel ingot is 1040 ℃, preserving heat for 18 hours, and then cooling to ensure that the final forging temperature of the die steel ingot is 855 ℃, and preserving heat for 13 hours;

then transferring the steel ingot of the mold to an annealing furnace with the temperature of 840 ℃, reducing the temperature in the annealing furnace to 812 ℃ at the cooling speed of 8 ℃/h, and then carrying out air cooling;

then putting the steel ingot of the mold into a quenching furnace with the temperature of 1040 ℃, preserving the heat for 5 hours, and then reducing the temperature in the quenching furnace to 1005 ℃ within 60 seconds;

and finally, putting the steel ingot of the mold into a tempering furnace with the temperature of 560 ℃, preserving the heat for 4.5 hours, and then cooling to the room temperature.

The heat treatment of sample 5 was carried out according to the following steps:

firstly, pressurizing a die steel ingot by a forging machine, wherein the initial forging temperature of the die steel ingot is 1060 ℃, preserving heat for 18.5 hours, then cooling to ensure that the final forging temperature of the die steel ingot is 870 ℃, and preserving heat for 12 hours;

then transferring the steel ingot of the mold into an annealing furnace with the temperature of 850 ℃, reducing the temperature in the annealing furnace to 816 ℃ at the cooling speed of 9 ℃/h, and then carrying out air cooling;

then putting the steel ingot of the die into a quenching furnace with the temperature of 1050 ℃, preserving the heat for 4 hours, and then reducing the temperature in the quenching furnace to 1000 ℃ within 80 s;

and finally, putting the steel ingot of the mold into a tempering furnace at the temperature of 620 ℃, preserving the heat for 5 hours, and then cooling to the room temperature.

The heat treatment of sample 6 was carried out according to the following procedure:

pressurizing a die steel ingot by a forging machine, wherein the initial forging temperature of the die steel ingot is 1030 ℃, preserving heat for 16 hours, and then cooling to enable the final forging temperature of the die steel ingot to be 855 ℃, and preserving heat for 13 hours;

then transferring the steel ingot of the mold to an annealing furnace with the temperature of 846 ℃, then reducing the temperature in the annealing furnace to 810 ℃ at the cooling speed of 7.5 ℃/h, and then carrying out air cooling;

then placing the steel ingot of the mold into a quenching furnace with the temperature of 1045 ℃, preserving the heat for 3 hours, and then reducing the temperature in the quenching furnace to 1008 ℃ within 75 s;

and finally, putting the steel ingot of the mold into a tempering furnace with the temperature of 650 ℃, preserving the heat for 4.6 hours, and then cooling to the room temperature.

The heat treatment of sample 7 was carried out according to the following procedure:

firstly, pressurizing a die steel ingot by a forging machine, wherein the initial forging temperature of the die steel ingot is 1060 ℃, preserving heat for 17 hours, and then cooling to ensure that the final forging temperature of the die steel ingot is 865 ℃, and preserving heat for 10 hours;

then transferring the steel ingot of the mold into an annealing furnace with the temperature of 840 ℃, reducing the temperature in the annealing furnace to 810 ℃ at the cooling speed of 8.5 ℃/h, and then carrying out air cooling;

then putting the steel ingot of the mold into a quenching furnace with the temperature of 1050 ℃, preserving the heat for 3.5 hours, and then reducing the temperature in the quenching furnace to 1000 ℃ within 68 s;

and finally, putting the steel ingot of the mold into a tempering furnace with the temperature of 590 ℃, preserving the heat for 4.3 hours, and then cooling to the room temperature.

The physical property test of thermal expansion coefficient was performed on the samples 1 to 7 after the heat treatment, and the data in table 2 were obtained:

TABLE 2

The thermal expansion coefficient of the conventional 1.2344 type die steel when the temperature is raised to 300 ℃ from room temperature is 13.4[10-6 m/(mxK) ], and is larger than that of the sample 1-sample 7, so that the die steel obtained by the invention has good thermal expansion performance and smaller deformation after heating.

The physical property test of thermal conductivity was performed on the heat-treated test pieces 1 to 7 and the conventional 1.2344 type die steel, and the data in table 3 were obtained:

TABLE 3

In the above table, the greater thermal conductivity of the model steels of samples 1 to 7 compared to that of model 1.2344 at the same temperature indicates that the model steels of the present invention have better thermal conductivity.

The physical property test of detecting the Rockwell hardness of the samples 1 to 7 after heat treatment by a Rockwell hardness test shows that the data in the table 4 are as follows:

TABLE 4

Test specimen	1	2	3	4	5	6	7
								Rockwell Hardness (HRC)	30	56	38	45	35	50	42

Randomly extracting samples 4, 6 and 7, respectively carrying out detection on the micro notch impact toughness values of the samples and the common 1.2344 type die steel at different temperatures under the same Rockwell hardness, and obtaining data in tables 5-7:

TABLE 5

TABLE 6

TABLE 7

The analysis in combination with tables 4, 5, 6 and 7 shows that the die steel prepared by the invention has better micro-notch impact toughness value than 1.2344 die steel under the same Rockwell hardness, which indicates that the die steel prepared by the invention has good toughness and ductility.

FIGS. 1 to 7 show the metallographic structure of the die steel obtained in examples 1 to 7, respectively, and it can be seen that the texture distribution is uniform.

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.

Claims

1. The long-life die-casting die steel comprises the following components in percentage by mass:

C：0.33％-0.41％、

si: not more than 0.5 percent,

Mn: not more than 0.5 percent,

Cr：4.8％-5.5％、

Mo：2.0％-2.4％、

V：0.3％-0.8％、

Ni: not more than 0.40 percent,

The balance of Fe and inevitable impurities; the method is characterized in that the heat treatment process of the long-life die-casting die steel comprises forging treatment, soft annealing treatment, quenching treatment and tempering treatment which are sequentially carried out, wherein the quenching treatment is that the die steel ingot subjected to the soft annealing treatment is placed into a quenching furnace with the temperature of 1040-1010 ℃, the temperature is kept for 3-5h, and then the temperature in the quenching furnace is reduced to 1000-1010 ℃ within 60-80 s;

the forging treatment is to pressurize the die steel ingot by a forging machine, the initial forging temperature of the casting is 1020-1070 ℃, the heat preservation is carried out for 16-20h, and then the temperature is reduced to lead the final forging temperature of the casting to be 850-880 ℃, and the heat preservation is carried out for 10-14 h;

the soft annealing treatment is to transfer the forged mold steel ingot into an annealing furnace with the temperature of 840-850 ℃, then to reduce the temperature in the annealing furnace to 810-820 ℃ at the cooling speed of 7-9 ℃/h, and then to carry out air cooling;

and the tempering treatment is to put the quenched steel ingot of the mold into a tempering furnace at the temperature of 530-680 ℃, preserve heat for 4-5h, and then cool the steel ingot to room temperature.

2. The long life die casting die steel as claimed in claim 1, wherein: the impurities comprise the following components:

p: not more than 0.015%,

S: not more than 0.003%,

H: not more than 2 ppm.

3. The long life die casting die steel as claimed in claim 1, wherein: the composition comprises the following components in percentage by mass:

C：0.36％、

Si：0.4％、

Mn：0.35％、

Cr：5％、

Mo：2.2％、

V：0.5％、

Ni：0.30％、

the balance being Fe and unavoidable impurities.

4. A long life die casting die steel as claimed in any one of claims 1 to 3, wherein: the Rockwell hardness is 30-56 HRC.