CN112226667B

CN112226667B - Preparation method of chromium stainless pre-hard plastic die steel

Info

Publication number: CN112226667B
Application number: CN202011064443.9A
Authority: CN
Inventors: 唐佳丽; 吴欣容; 蔡武; 胡峰荣; 王建; 张璨; 刘迎骥
Original assignee: Pangang Group Jiangyou Changcheng Special Steel Co Ltd
Current assignee: Pangang Group Jiangyou Changcheng Special Steel Co Ltd
Priority date: 2020-09-30
Filing date: 2020-09-30
Publication date: 2022-02-01
Anticipated expiration: 2040-09-30
Also published as: CN112226667A

Abstract

The invention provides a preparation method of chromium stainless pre-hard plastic die steel, which comprises the following steps: A) preparing materials; adding lime in the process of proportioning; B) melting the furnace burden obtained in the step A) in an electric furnace, and adding Fe-Si blocks and Al blocks in the melting process; C) performing LF smelting on the molten steel obtained in the step B), and feeding an Al wire into the molten steel in an amount of 0.06 wt%; D) carrying out VD vacuum refining on the molten steel obtained in the step C), and forbidding Al adjustment after VD is finished; E) pouring the molten steel obtained in the step D), and then cogging and rolling; F) and heating, rolling and air cooling the cogging-rolled steel billet in sequence to obtain the chromium stainless pre-hard plastic die steel. The high-quality pre-hardened plastic die steel is manufactured by technical control of smelting purity control, high-temperature heating of steel ingots, rolling cogging deformation guarantee, online pre-hardening and the like.

Description

Preparation method of chromium stainless pre-hard plastic die steel

Technical Field

The invention relates to the technical field of die steel, in particular to a preparation method of chromium stainless pre-hard plastic die steel.

Background

With the development of plastic varieties and plastic molds, the varieties and the usage amount of plastic mold steel are also increasing. The plastic die steel is generally prepared by quenching and tempering normalized 45 Cr and 40Cr for plastic dies, so that the hardness is low, the wear resistance is poor, the surface roughness value is high, the appearance quality of processed plastic products is poor, and the service life of the dies is short. The precision plastic mold and the plastic mold with high hardness are made of CrWMo, Cr12MoV and other alloy tool steels, so that the precision plastic mold and the plastic mold have poor machining performance, are difficult to machine a complex cavity and cannot solve the problem of heat treatment deformation. Therefore, it is important to provide a high-quality plastic die steel with high surface quality.

Disclosure of Invention

The invention aims to provide a preparation method of chromium stainless pre-hard plastic die steel, and the die steel prepared by the preparation method provided by the application has good surface quality and high qualification rate.

In view of the above, the present application provides a method for preparing chromium stainless pre-hard plastic die steel, comprising the following steps:

A) the formula comprises the following components: 0.29 to 0.33wt% of C, 0.50 to 0.80wt% of Si, 12.5 to 14.0wt% of Cr, 0.01 to 0.04wt% of Al, less than or equal to 1.00wt% of Mn, less than or equal to 0.005wt% of S, less than or equal to 0.60wt% of Ni, less than or equal to 0.02wt% of As, less than or equal to 0.01wt% of Sn, less than or equal to 0.01wt% of Pb, less than or equal to 0.01wt% of Bi, less than or equal to 0.0002wt% of H, less than or equal to 0.0025wt% of O, and less than or equal to 0.04wt% of As + Sn + Pb + Sb + Bi; adding lime in the process of proportioning;

B) melting the furnace burden obtained in the step A) in an electric furnace, and adding Fe-Si blocks and Al blocks in the melting process;

C) performing LF smelting on the molten steel obtained in the step B), and feeding an Al wire into the molten steel in an amount of 0.06 wt%;

D) carrying out VD vacuum refining on the molten steel obtained in the step C), and forbidding Al adjustment after VD is finished;

E) pouring the molten steel obtained in the step D), and then cogging and rolling;

F) and heating, rolling and air cooling the cogging-rolled steel billet in sequence to obtain the chromium stainless pre-hard plastic die steel.

Preferably, in the step A), the burden adopted by the burden is low-P and low-S scrap steel, the steel grade, or return materials and alloy materials of similar steel grades.

Preferably, in the step B), the temperature of the molten steel is 1600-1700 ℃.

Preferably, in the step C), the holding time of the white slag in the LF smelting is more than or equal to 15min, and Al is adjusted to 0.06% by feeding an Al wire after the LF smelting is finished.

Preferably, in the step D), the maintaining time of the VD in vacuum refining is more than or equal to 1min under the condition that the ultimate vacuum degree is less than or equal to 70 Pa.

Preferably, in the step D), the flow of Ar is adjusted to be less than or equal to 20L/min 1min before the vacuum breaking of VD vacuum refining; the argon blowing time is more than or equal to 25min, and the ladle pouring temperature is 1500-1600 ℃.

Preferably, in step D), the VD vacuum refining has a [ H ] of less than or equal to 2.0 ppm.

Preferably, the flow of the poured argon gas is 0.3-0.5 MPa.

Preferably, the heating comprises a preheating section, a heating section and a soaking section; the temperature of the preheating section is less than or equal to 700 ℃, the temperature of the heating section is 850-900 ℃, the temperature of the heating section is 1000-1120 ℃, and the temperature of the soaking section is 1150-1200 ℃; the heating time is more than or equal to 150min, and the soaking time is more than or equal to 45 min.

Preferably, the finishing temperature of the continuous rolling is more than or equal to 950 ℃.

The application provides a preparation method of chromium stainless pre-hard plastic die steel, which is characterized in that high-quality pre-hard plastic die steel CGS-313 is manufactured by technical control of smelting purity control, steel ingot high-temperature heating, rolling cogging deformation guarantee, online pre-hardening and the like: the flaw detection qualification rate GB/T4162B grade qualification rate is more than or equal to 95 percent; non-metallic inclusions: A. c, D-type inclusions are less than or equal to 1.5 grade, B-type inclusions are less than or equal to 2.0 grade, and the qualification rate is more than or equal to 95 percent; the hardness difference of the pre-hardened round steel is less than or equal to 3HRC, and the qualification rate is more than or equal to 95 percent.

Drawings

FIG. 1 is a photograph of a finished chromium stainless pre-hard plastic mold steel made in accordance with the present invention;

FIG. 2 is a photograph of a finished pre-hardened round bar prepared in comparative example 2 of the present invention;

FIG. 3 is a photograph of a finished pre-hardened round bar prepared in comparative example 2 of the present invention;

FIG. 4 is a metallographic photograph of a finished pre-hardened round bar prepared according to an embodiment of the present invention;

fig. 5 is a metallographic photograph of a finished pre-hardened round bar prepared according to a comparative example of the present invention.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

In order to improve the surface quality of the die steel and the qualification rate, the application provides a preparation method of chromium stainless pre-hard plastic die steel, which specifically comprises the following steps:

In the preparation process, smelting is firstly carried out, and materials are required to be prepared according to final components before smelting; in the application, lime is added by 1.9 wt% -2.3 wt% based on the ingredients in the process of ingredient preparation. The burden of the burden consists of low P and low S scrap steel, the original steel, or return steel material and alloy material of similar steel grade, and the carbon in the burden is more than or equal to 1.5 percent; p is less than or equal to the standard upper limit of-0.005 percent; si is less than or equal to 0.80 percent, so that the components of the final product can reach the following components: 0.29 to 0.33wt% of C, 0.50 to 0.80wt% of Si, 12.5 to 14.0wt% of Cr, 0.01 to 0.04wt% of Al, less than or equal to 1.00wt% of Mn, less than or equal to 0.005wt% of S, less than or equal to 0.60wt% of Ni, less than or equal to 0.02wt% of As, less than or equal to 0.01wt% of Sn, less than or equal to 0.01wt% of Pb, less than or equal to 0.01wt% of Bi, less than or equal to 0.0002wt% of H, less than or equal to 0.0025wt% of O, and less than or equal to 0.04wt% of As + Sn + Pb + Sb + Bi; lime is added in the process of proportioning. In the aspect of controlling the components, the impurity elements (P, S, penta-harmful As + Sn + Pb + Sb + Bi) and the gas (O, H) are mainly controlled, and the purity is improved.

After the batching is completed, the furnace burden after batching is subjected to electric furnace smelting, LF smelting, VD smelting and die casting in sequence. In the process of electric furnace smelting, the proportioned furnace burden is sent to an electric furnace to be melted so as to ensure the degassing strength of the electric furnace, Fe-Si and Al blocks are adopted to ensure the deoxidation effect, the tapping temperature after the electric furnace smelting is finished is 1600-1700 ℃, and in a specific embodiment, the tapping temperature is 1653-1688 ℃; 9.4-10.2 kg of Fe-Si is added to each ton of furnace burden, and 1.87-2.50 kg of Al blocks are added to each ton of furnace burden.

According to the invention, the molten steel smelted by the electric furnace is subjected to LF smelting, and an Al wire is fed into the molten steel in an amount of 0.06 wt%; before LF smelting, firstly adjusting the flow of argon, then immediately feeding an aluminum wire into molten steel in an amount of 0.06wt%, wherein the wire feeding speed is more than or equal to 2.5 m/s; the white slag retention time in the LF furnace treatment is more than or equal to 15 minutes; and feeding an Al wire to adjust Al to 0.06 percent when the LF treatment is finished, ensuring that Al enters specification internal control, and forbidding to adjust Al after VD is finished. Adding Fe-Si and Al blocks, feeding aluminum wires and controlling the content of the aluminum wires in electric furnace smelting to deoxidize molten steel, and if the addition amount of Al is less and the deoxidizing effect is not good, adding more Al to generate B-type and D-type inclusions.

According to the method, the molten steel after LF smelting is subjected to VD vacuum refining, and in the vacuum refining process, the holding time is more than or equal to 15min when the ultimate vacuum degree is less than or equal to 67 Pa; 1min before breaking, regulating the Ar flow to be less than or equal to 20L/min, measuring the temperature and sampling after breaking; determining [ H ] or taking [ H ] sample for analysis, wherein the content of [ H ] is less than or equal to 2.0 ppm; the soft argon blowing time is more than or equal to 25min, and the ladle pouring temperature is 1500-1600 ℃.

The obtained molten steel is poured, the pouring is carried out under the argon protective atmosphere, and the flow of argon is 0.3-0.5 MPa. After the pouring is finished, rolling and cogging are carried out, wherein the rolling and cogging are firstly heated and cogging is carried out, the heating temperature is 1200-1500 ℃, and the time is 1.0-3.0 h; more specifically, the heating temperature is 1200-1300 ℃, and the time is 1.5-3.0 h.

After the rolling cogging, carrying out continuous rolling, wherein the heating comprises a preheating section, a heating first section, a heating second section and a soaking section; the temperature of the preheating section is less than or equal to 700 ℃, the temperature of the heating section is 850-900 ℃, the temperature of the heating section is 1000-1120 ℃, and the temperature of the soaking section is 1150-1200 ℃; the heating time is more than or equal to 150min, and the soaking time is more than or equal to 45 min; the adoption of the heating of the sections can prevent the generation of cracks and play a certain homogenizing effect on the segregation of the material, thereby ensuring that the structure is uniform. And controlling the finish rolling temperature of the continuous rolling to be more than or equal to 950 ℃, and air-cooling the finished round steel after rolling to obtain the finished die steel. The control of the rolling cogging and continuous rolling temperature and time leads the material to be plastically deformed in the optimal temperature area, thus obtaining the optimal structure and performance.

For further understanding of the present invention, the following examples are provided to illustrate the preparation method of the die steel of the present invention, and the scope of the present invention is not limited by the following examples.

The preparation process of the chromium stainless pre-hard plastic die steel comprises the following steps: steel ingot smelting in a steel-making main factory → 825 rolling mill cogging → rolling round steel by a continuous rolling unit → air cooling → tempering → flaw detection → inspection; the specific production process comprises the following steps:

1) the material smelting adopts a process route of electric furnace + LF + VD + die casting:

A) the requirements for ingredients

(a) Filling 795-814 kg of lime on the bottom of the furnace before charging, and then charging;

(b) 35-45 t of furnace charge comprises low-P and low-S scrap steel, return materials of the steel grade or similar steel grades, alloy materials and the like, and the carbon of the burden is more than or equal to 1.5%; p is less than or equal to the standard upper limit of-0.005 percent; si is less than or equal to 0.80 percent;

(c) the steel remaining amount of the electric furnace and the pouring allowance during pouring are fully considered for the ingredients, and the pouring allowance is calculated according to 1.3-1.5 t;

(d) chemical composition requirements, as shown in table 1:

TABLE 1 CGS-313 chemical composition requirements data Table (wt%)

Note: as + Sn + Pb + Sb + Bi is less than or equal to 0.04;

B) smelting method

(a) Feeding furnace materials to be molten, ensuring the degassing strength of the electric furnace in the process, adopting 375-405 kg of Fe-Si (taking the furnace materials as the base) and 78-95 kg of Al blocks (taking the furnace materials as the base) to ensure the deoxidation effect, and ensuring the tapping temperature to be 1653-1688 ℃;

(b) hoisting the ladle to an LF furnace station and requiring:

(b1) adjusting the flow of argon, immediately feeding an aluminum wire into the molten steel according to 0.06 percent (the wire feeding speed is more than or equal to 2.5m/s), and measuring the temperature after the aluminum wire is fed;

(b2) the white slag retention time in the LF furnace treatment is more than or equal to 15 minutes;

(b3) feeding an Al wire to adjust Al to 0.06% after LF treatment is finished, ensuring that Al enters specification internal control, and forbidding Al adjustment after VD is finished;

(c) VD vacuum refining

(c1) The thickness of the slag in the tank is 60-100 mm, the temperature is measured, and the argon flow is adjusted;

(c2) the holding time is more than or equal to 15min when the ultimate vacuum degree is less than or equal to 67 Pa;

(c3) 1min before breaking, regulating the Ar flow to be less than or equal to 20L/min, measuring the temperature and sampling after breaking;

(c4) determining [ H ] or taking [ H ] sample for analysis, wherein the content of [ H ] is less than or equal to 2.0 ppm;

(c5) the soft argon blowing time is more than or equal to 25min, and the ladle pouring temperature is 1542-1552 ℃;

(d) pouring

The protecting slag and the heating agent of the large western protected ingot are adopted during pouring, the smoothness of a slit type argon protecting device is required to be confirmed before pouring, the argon flow of argon protection during pouring is controlled to be 0.3-0.5 MPa, and the poured steel ingot is sent to a steel rolling mill in a hot state;

2) rolling cogging process

Heating and cogging the steel ingot, keeping the temperature at 1207-1227 ℃, keeping the temperature for 1.5-2.0h, rolling the steel ingot into a blank of 180mm multiplied by 180mm by a 825 rolling mill unit, and polishing the surface of the blank after annealing to ensure the surface quality of the finished round steel;

3) tandem rolling process

A) The heating process of the repaired steel billet is shown in table 2:

TABLE 2 heating technical data table for continuous rolling steel billet

Rolling the rolled steel into a material by using a continuous rolling unit, controlling the finish rolling temperature to be more than or equal to 950 ℃, air-cooling the rolled finished round steel, and detecting the hardness by using a portable hardness tester to ensure the uniformity of the hardness;

B) the finished round steel is tempered by an RODR1500 roller bottom, and the tempering process is shown in Table 3:

TABLE 3 RODR1500 roller bottom tempering process data sheet

Specification (mm)	Tempering system (temperature is selected according to specific requirements of users in range)
		16≤Φ＜30	575 to 625 ℃, 9.0 to 10.0 hours of air cooling
30≤Φ＜45	575 to 625 ℃, 9.5 to 10.5 hours of air cooling
		45≤Φ＜60	575-625 ℃, 10.0-11.0h, air cooling
60≤Φ＜75	575 to 625 ℃, 10.5 to 11.5 hours of air cooling
		75≤Φ≤90	575 to 625 ℃, 11.0 to 12.0 hours of air cooling

Examples

Prepared according to the preparation process

And

the finished product of the pre-hardened round steel:

the chemical components are specifically shown in table 4:

table 4 composition data of pre-hardened round steel in examples

C	Si	Mn	P	S	Cr	Al	Ni
								0.305	0.565	0.315	0.015	0.001	12.85	0.037	0.11
As	Sn	Pb	Sb	Bi	H	O
								0.006	0.004	0.001	0.005	0.003	0.00005	0.0016

Note: as + Sn + Pb + Sb + Bi is 0.019;

after smelting, rolling and cogging and continuous rolling, the finished product of the pre-hardened round steel is obtained, and the specific control values of the procedures are as follows:

1. smelting method

(a) Charging materials are electrified and melted, the degassing strength of an electric furnace is ensured in the process, the deoxidation effect is ensured by adopting 395kgFe-Si and 85kgAl blocks, and the tapping temperature is 1670 ℃;

(b) hoisting the ladle to an LF furnace station and requiring:

(b2) the white slag retention time in LF furnace treatment is 20 minutes;

(c) VD vacuum refining

(c1) The thickness of the slag in the tank is 80mm, the temperature is measured, and the argon flow is adjusted;

(c2) the holding time is 20min when the ultimate vacuum degree is less than or equal to 67 Pa;

(c4) determining [ H ] or taking [ H ] sample for analysis, wherein the content of [ H ] is 0.5 ppm;

(c5) soft argon blowing time is 30min, and ladle pouring temperature is 1554 ℃;

(d) pouring

2) rolling cogging process

Heating and cogging a steel ingot, keeping the temperature at 1220 ℃, keeping the temperature for 1.5h, rolling the steel ingot into a blank of 180mm multiplied by 180mm by using a 825 rolling mill set, and polishing the surface of the blank after annealing so as to ensure the surface quality of a finished round steel;

3) tandem rolling process

A) The heating process of the repaired steel billet is shown in table 5:

TABLE 5 heating technical data table for tandem rolling steel billet

Rolling the rolled steel into a material by using a continuous rolling unit, controlling the finish rolling temperature to be 980 ℃, air-cooling the rolled finished round steel, and performing hardness detection by using a portable hardness tester to ensure the uniformity of hardness;

detecting inclusions in the finished pre-hardened round steel, wherein the detection result is shown in table 6;

TABLE 6 Inclusion data sheet for finished pre-hardened round bars of various sizes

	Coarse A	A is thin	B coarse	B is thin	Coarse fraction of C	Fine diameter of C	D coarse	D is thin	DS
										1#	0	0.5	0	1.0	0	0	0.5	1.0	1.0
2#	0	0.5	0	1.0	0	0	0.5	1.0	0

Tempering through RODR1500 roller bottom according to the process as shown in Table 7:

TABLE 7 data sheet of tempering process for finished pre-hardened round steel with different sizes

Specification (mm)	Tempering system
		30≤Φ＜45	Air cooling at 600 +/-10 ℃ for 9.5-10.5h
75≤Φ≤90	600 +/-10 ℃, 11.0-12.0h, air cooling

The hardness data table of the product after the tempering treatment is shown in table 8:

TABLE 8 hardness data sheet of the finished product after tempering

As can be seen from Table 8, the same section hardness difference was 3HRC or less.

As shown in fig. 1, the finished product produced in this example was tested for flaw detection, and as can be seen from fig. 1, the flaw detection yield was 100%.

Comparative example 1

The other steps are the same as the embodiment except that: the addition amounts of the deoxidizer Fe-Si and the Al block are respectively as follows: 355kg of Fe-Si and 65kg of Al blocks, and feeding Al wires to adjust the Al content to be 0.037%, wherein the content of non-metallic inclusions is required to be easily out of standard, and is shown in the following table 9:

TABLE 9 inclusion data Table for finished pre-hardened round bars prepared in comparative example 1

	Coarse A	A is thin	B coarse	B is thin	Coarse fraction of C	Fine diameter of C	D coarse	D is thin	DS
										1#	0	0.5	1.0	3.0	0	0	0.5	1.0	2.0
2#	0	0.5	0	2.0	0	0	0.5	1.0	1.5

Comparative example 2

The other steps are the same as the embodiment except that: the casting temperature of the smelting ladle is 1562 ℃, and then the pre-hardened round steel is segregated, as shown in table 10:

table 10 segregation degree data table of pre-hardened round steel for finished product prepared in comparative example 2

Comparative example 3

The other steps are the same as the embodiment except that: in the rolling process, continuous casting and rolling were directly performed without cogging, and as shown in table 11,

table 11 table of center porosity data of finished pre-hardened round steel prepared in comparative example 3

The photographs of the finished pre-hardened round bars prepared in comparative example 2 and comparative example 3 are specifically shown in fig. 2 and 3.

Comparative example 4

The other steps are the same as the embodiment except that: heating and cogging the steel ingot, wherein the heat preservation temperature is 1160 ℃, and the heat preservation time is 70 min; total heating time of continuously rolled steel billets: 120min, soaking time: and (3) 30 min. The hardness of the final pre-hardened round steel was not uniform, as shown in table 12,

table 12 table of hardness data of finished pre-hardened round steel prepared in comparative example 4

Fig. 4 and 5 are metallography photographs (the left side is the edge structure, and the right side is the center structure) of the pre-hardened round steel prepared in the examples and comparative examples, respectively, and it can be seen that the temperature and time control does not meet the requirements, so that the finished product structure is not uniform, and the crystal grains are coarse.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of chromium stainless pre-hard plastic die steel comprises the following steps:

B) melting the furnace burden obtained in the step A) in an electric furnace, and adding Fe-Si blocks and Al blocks in the melting process; adding 9.4-10.2 kg of Fe-Si into each ton of furnace charge, and adding 1.87-2.50 kg of Al block into each ton of furnace charge

D) carrying out VD vacuum refining on the molten steel obtained in the step C), and forbidding Al adjustment after VD is finished; the ladle pouring temperature of VD vacuum refining is 1542-1552 ℃;

E) pouring the molten steel obtained in the step D), and then cogging and rolling; the cogging rolling is firstly carried out heating cogging, the heating temperature is 1200-1500 ℃, and the time is 1.0-3.0 h;

F) heating, rolling and air cooling the cogging-rolled steel billet in sequence to obtain chromium stainless pre-hard plastic die steel; the heating comprises a preheating section, a heating section and a soaking section; the temperature of the preheating section is less than or equal to 700 ℃, the temperature of the heating section is 850-900 ℃, the temperature of the heating section is 1000-1120 ℃, and the temperature of the soaking section is 1150-1200 ℃; the heating time is more than or equal to 150min, and the soaking time is more than or equal to 45 min.

2. The process of claim 1, wherein in step a), the burden is low P and low S scrap steel, a steel grade.

3. The manufacturing method according to claim 1, wherein the temperature of the molten steel discharged in the step B) is 1600 to 1700 ℃.

4. The preparation method of claim 1, wherein in the step C), the holding time of the white slag in the LF smelting is more than or equal to 15min, and Al is adjusted to 0.06% by feeding Al wires at the end of the LF smelting.

5. The method according to claim 1, wherein in the step D), the VD vacuum refining is performed for a holding time of 1min or more at a limiting vacuum degree of 70Pa or less.

6. The preparation method according to claim 1, wherein in the step D), the Ar flow is adjusted to be less than or equal to 20L/min 1min before the vacuum break of the VD vacuum refining; the argon blowing time is more than or equal to 25 min.

7. The method according to claim 1, wherein in step D), the VD vacuum refining has a [ H ] content of 2.0ppm or less.

8. The production method according to claim 1, wherein the flow rate of the poured argon gas is 0.3 to 0.5 MPa.

9. The method according to claim 1, wherein the finishing temperature of the continuous rolling is not less than 950 ℃.