Steel material preparation method and alloy steel material

Abstract

The embodiment of the invention discloses a steel material preparation method and an alloy steel material. The method comprises the steps that a blank is subjected to thermal desorption and atmosphere reduction, the blank subjected to atmosphere reduction is sintered, the sintered blank is subjected to high-partial-pressure sintering under the partial pressure of 70-85 KPA, the high-partial-pressure sintering temperature is 900-1150 DEG C, and the blank subjected to high-partial-pressure sintering is cooled to obtain the alloy steel material. Nitrogen fixation is conducted on the blank through high partial pressure sintering, nitrogen elements in the blank are fixed so as to prevent the situation that the nitrogen elements in the blank are not evenly distributed due to the fact that the nitrogen elements in the blank are lost, and then the situation that the local magnetic conductivity of the blank is too high due to the fact that the nitrogen elements in the blank are not evenly distributed is avoided. The high partial pressure sintering step has a nitrogen fixation effect, so that the magnetic conductivity of the prepared alloy steel material can be greatly reduced, and the alloy steel material can be completely non-magnetic. As heat treatment and nitrogen fixation are not carried out on the blank any more, local size reduction of the blank caused by heat treatment is avoided, and the size stability of the finally-manufactured alloy steel product is guaranteed.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of steel material preparation, and specifically to a steel material preparation method and alloy steel material. Background Art

[0002] Metal Injection Molding (MIM) is an emerging technology that combines traditional powder metallurgy process with existing plastic injection molding technology. It not only has the characteristics of high material utilization rate of powder metallurgy products, but also has the advantages of high production efficiency of injection molding, uniform product structure, close to net shape, and high dimensional accuracy. It is now widely used in a variety of material systems such as high specific gravity, hard alloy, stainless steel, low alloy steel, magnetic materials, etc., and its products have also been used in many industries such as computers, mechanical automation, automobiles and ships, and medical equipment.

[0003] The existing process uses a vacuum sintering furnace to sinter the blank obtained by injection molding, and then performs heat treatment to fix nitrogen. However, this process will cause the local size of the blank to be smaller, and will cause the nitrogen element inside the blank to be unevenly distributed, so that the local magnetic permeability of the blank is greater than 1.05h / m, and the product defect rate is high. Summary of the invention

[0004] The embodiments of the present application provide a method for preparing a steel material and an alloy steel material, which can effectively ensure the dimensional stability of the alloy steel product and ensure that the alloy steel product is non-magnetic.

[0005] A first aspect of an embodiment of the present application provides a method for preparing a steel material, comprising the following steps:

[0006] Thermal stripping: In a protective gas atmosphere, the blank obtained by injection molding is thermally stripped, and the temperature is maintained for 90 to 180 minutes;

[0007] Atmosphere reduction: performing atmosphere reduction on the blank in a reducing atmosphere, heating the blank to 1000-1100° C. and maintaining the temperature for 60-180 min;

[0008] Sintering: Sinter the blank after atmosphere reduction, the sintering temperature is ≥1300℃, and the sintering time is 120~240min;

[0009] High partial pressure sintering: The sintered blank is subjected to high partial pressure sintering at a partial pressure of 70-85KPA, and the temperature of high partial pressure sintering is 900-1150°C;

[0010] Cooling: The blank that has completed high partial pressure sintering is cooled to obtain alloy steel material.

[0011] Optionally, in the high partial pressure sintering step, the duration of high partial pressure sintering of the green body is 2 to 3 hours.

[0012] Optionally, the protective gas in the thermal stripping step includes nitrogen.

[0013] Optionally, the temperature of the blank is raised to 750-850° C. during the thermal stripping step.

[0014] Optionally, the heating rate of the blank in the thermal stripping step is 3-5°C / min.

[0015] Optionally, in the sintering step, the green body that has completed the atmosphere reduction is sintered at a partial pressure of 50 to 70 KPA.

[0016] Optionally, before the thermal stripping step, the following steps are also included:

[0017] Granulation: Stainless steel powder and a binder are mixed and granulated to obtain a granular feed; the mass fraction of the stainless steel powder is 88-92%, and the mass fraction of the binder is 8-12%; the stainless steel powder includes Cr, Mn, Mo, N, C, and Fe elements;

[0018] Injection molding: The granular feed is injection molded to obtain the blank.

[0019] A second aspect of an embodiment of the present application provides an alloy steel material, which is prepared according to the method described in the first aspect.

[0020] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0021] High partial pressure sintering is used to fix nitrogen in the blank, fixing the nitrogen element in the blank to prevent the loss of nitrogen in the blank from causing uneven distribution of nitrogen inside the blank, thereby avoiding excessive local magnetic permeability of the blank due to uneven distribution of nitrogen inside the blank. Therefore, the high partial pressure sintering step can greatly reduce the magnetic permeability of the prepared alloy steel material due to its nitrogen fixing effect, and can achieve complete non-magnetic alloy steel material. At the same time, since the blank is no longer heat-treated to fix nitrogen, the local size reduction of the blank due to heat treatment can be avoided, thereby ensuring the stability of the size of the final alloy steel product, and making it easier for technicians to control the product size. DETAILED DESCRIPTION

[0022] The embodiments of the present application provide a method for preparing a steel material and an alloy steel material, which can effectively ensure the dimensional stability of the alloy steel product and ensure that the alloy steel product is non-magnetic.

[0023] The following is a description of the steel material preparation method in the embodiment of the present application:

[0024] The steel material preparation method comprises the following steps:

[0025] Thermal stripping: In a protective gas atmosphere, the blank obtained by injection molding is thermally stripped, and the temperature is maintained for 90 to 180 minutes;

[0026] Atmosphere reduction: performing atmosphere reduction on the blank in a reducing atmosphere, heating the blank to 1000-1100° C. and maintaining the temperature for 60-180 min;

[0027] Sintering: Sinter the blank after atmosphere reduction, the sintering temperature is ≥1300℃, and the sintering time is 120~240min;

[0028] High partial pressure sintering: The sintered blank is subjected to high partial pressure sintering at a partial pressure of 70-85KPA, and the temperature of high partial pressure sintering is 900-1150°C;

[0029] Cooling: The blank that has completed high partial pressure sintering is cooled to obtain alloy steel material.

[0030] Among them, the sintering step and the high partial pressure sintering step are different in partial pressure and temperature, and the effects on the blank are also different. The sintering step can increase the density of the blank and improve the density of the blank, so that the blank has stronger rigidity and higher hardness. The high partial pressure sintering step can fix nitrogen in the blank, fix the nitrogen element in the blank to prevent the loss of nitrogen in the blank from causing uneven distribution of nitrogen elements inside the blank, and thus avoid the local magnetic permeability of the blank being too high due to uneven distribution of nitrogen elements inside the blank. Therefore, the high partial pressure sintering step can greatly reduce the magnetic permeability of the prepared alloy steel material due to its nitrogen fixing effect, and can achieve complete non-magnetic alloy steel material.

[0031] In a preferred embodiment, the high partial pressure sintering time of the green body in the high partial pressure sintering step is 2 to 3 hours.

[0032] In a preferred embodiment, the protective gas in the thermal stripping step includes nitrogen, which can protect the blank from being oxidized at a high temperature.

[0033] In a preferred embodiment, the temperature of the blank is raised to 750-850° C. during the thermal stripping step.

[0034] In a preferred embodiment, the heating rate of the blank in the thermal stripping step is 3-5° C. / min.

[0035] In a preferred embodiment, in the sintering step, the green body that has completed the atmosphere reduction is sintered at a partial pressure of 50-70 KPA.

[0036] In a preferred embodiment, before the thermal stripping step, the following steps are also included:

[0037] Granulation: The stainless steel powder and the binder are mixed and granulated to obtain a granular feed; the mass fraction of the stainless steel powder is 88-92%, and the mass fraction of the binder is 8-12%; the stainless steel powder includes Cr, Mn, Mo, N, C, and Fe elements;

[0038] Injection molding: The granular feed is injection molded to obtain a blank.

[0039] In the granulation step, the stainless steel powder and the adhesive can be mixed and granulated using an internal mixer to obtain a granular feed. In the injection molding step, the granular feed can be loaded into the injection molding machine barrel and heated to a specified temperature (generally the melting temperature of the adhesive, between 170-195°C) to make it fluid, and then injected into a customized mold under appropriate pressure to form a green blank.

[0040] The thermal degreasing step is thermal debinding, and a debinding furnace can be used to perform thermal debinding on the blank to remove the residual adhesive in the blank. In the embodiment of the present application, the blank is thermally debinded based on the above parameters, and the debinding rate of the blank can reach more than 6.8%.

[0041] The hot debinded blank can be sintered in a sintering furnace. During the atmosphere reduction, a reducing atmosphere such as nitrogen or a mixture of nitrogen and hydrogen can be introduced. During high partial pressure sintering, argon can be introduced to protect the blank from oxidation at high temperature.

[0042] In the cooling step, the green body that has completed high partial pressure sintering can be cooled naturally to room temperature, or can be cooled by water or forced ventilation with a blower. The embodiment of the present application does not limit the method of cooling the green body that has completed high partial pressure sintering.

[0043] The alloy steel material in the embodiment of the present application is described below:

[0044] The alloy steel material is prepared according to the steel material preparation method described above. The alloy steel material prepared by this method has greatly improved hardness and rigidity, and greatly reduced magnetic permeability, and can be completely non-magnetic.

[0045] In the embodiment of the present application, the blank is subjected to thermal stripping and atmosphere reduction, the blank after atmosphere reduction is sintered, the blank after sintering is subjected to high partial pressure sintering at a partial pressure of 70 to 85KPA, the high partial pressure sintering temperature is 900 to 1150°C, and the blank after high partial pressure sintering is cooled to obtain an alloy steel material. High partial pressure sintering is used to fix nitrogen in the blank, fix the nitrogen element in the blank to prevent the loss of nitrogen in the blank from causing uneven distribution of nitrogen elements inside the blank, and thus avoid excessive local magnetic permeability of the blank due to uneven distribution of nitrogen elements inside the blank. Therefore, the high partial pressure sintering step can greatly reduce the magnetic permeability of the prepared alloy steel material due to the nitrogen fixing effect, and can achieve complete non-magnetic alloy steel material. At the same time, since the blank is no longer subjected to heat treatment for nitrogen fixing, the local size reduction of the blank due to heat treatment can be avoided, thereby ensuring the stability of the size of the final alloy steel product, and making it easier for technicians to control the product size.

[0046] In order to further illustrate the embodiments of the present application in detail, a method for preparing a steel material and an alloy steel material provided by the present invention are described in detail below in combination with the embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] Weighing: Weigh each component according to the mass fraction of the following components to obtain stainless steel powder:

[0049] C: 0.20%, Si: 0.25%, S: 0.04%, P: 0.03%, Mn: 0.70%, Ni: 0.55%, Cr: 0.50%, Mo: 0.20%, Cu: 0.35%, O: 0.05%, N: 0.05%, and the balance is Fe.

[0050] Granulation: using an internal mixer to mix and granulate the stainless steel powder and the adhesive to obtain a granular feed; the mass fraction of the stainless steel powder is 88-92%, and the mass fraction of the adhesive is 8-12%;

[0051] Injection molding: injecting the granular feed into a mold to obtain a blank;

[0052] Thermal stripping: In a protective gas atmosphere, the blank is thermally stripped, the blank is heated to 750°C, the heating rate is 3°C / min, and the temperature is maintained for 90 to 180 minutes;

[0053] Atmosphere reduction: The blank is reduced in a reducing atmosphere, the temperature of the blank is raised to 1000-1100°C and maintained at the temperature for 60-180 minutes;

[0054] Sintering: The blank after atmosphere reduction is sintered at a partial pressure of 50KPA, a sintering temperature of 1300°C, and a sintering time of 120min;

[0055] High partial pressure sintering: The sintered blank is subjected to high partial pressure sintering at a partial pressure of 70KPA, and the temperature of high partial pressure sintering is 900℃;

[0056] Cooling: The blank that has completed high partial pressure sintering is cooled naturally to obtain alloy steel material.

[0057] Example 2

[0058] Weighing: Weigh each component according to the mass fraction of the following components to obtain stainless steel powder:

[0059] C: 0.20%, Si: 0.25%, S: 0.04%, P: 0.03%, Mn: 0.80%, Ni: 0.55%, Cr: 0.50%, Mo: 0.20%, Cu: 0.35%, O: 0.05%, N: 0.05%, and the balance is Fe.

[0060] Granulation: using an internal mixer to mix and granulate the stainless steel powder and the adhesive to obtain a granular feed; the mass fraction of the stainless steel powder is 88-92%, and the mass fraction of the adhesive is 8-12%;

[0061] Injection molding: injecting the granular feed into a mold to obtain a blank;

[0062] Thermal stripping: In a protective gas atmosphere, the blank is thermally stripped, the blank is heated to 800°C, the heating rate is 4°C / min, and the temperature is maintained for 90 to 180 minutes;

[0063] Atmosphere reduction: The blank is reduced in a reducing atmosphere, the temperature of the blank is raised to 1000-1100°C and maintained at this temperature for 60-180 minutes;

[0064] Sintering: The blank after atmosphere reduction is sintered at a partial pressure of 60KPA, a sintering temperature of 1350°C, and a sintering time of 180min;

[0065] High partial pressure sintering: The sintered blank is subjected to high partial pressure sintering at a partial pressure of 75KPA, and the temperature of high partial pressure sintering is 950°C;

[0066] Cooling: The blank that has completed high partial pressure sintering is cooled naturally to obtain alloy steel material.

[0067] Example 3

[0068] Weighing: Weigh each component according to the mass fraction of the following components to obtain stainless steel powder:

[0069] C: 0.20%, Si: 0.25%, S: 0.04%, P: 0.03%, Mn: 0.90%, Ni: 0.55%, Cr: 0.50%, Mo: 0.20%, Cu: 0.35%, O: 0.05%, N: 0.05%, and the balance is Fe.

[0070] Granulation: using an internal mixer to mix and granulate the stainless steel powder and the adhesive to obtain a granular feed; the mass fraction of the stainless steel powder is 88-92%, and the mass fraction of the adhesive is 8-12%;

[0071] Injection molding: injecting the granular feed into a mold to obtain a blank;

[0072] Thermal stripping: In a protective gas atmosphere, the blank is thermally stripped, the blank is heated to 800°C, the heating rate is 5°C / min, and the temperature is maintained for 90 to 180 minutes;

[0073] Atmosphere reduction: The blank is reduced in a reducing atmosphere, the temperature of the blank is raised to 1000-1100°C and maintained at the temperature for 60-180 minutes;

[0074] Sintering: The blank after atmosphere reduction is sintered at a partial pressure of 65KPA, a sintering temperature of 1350°C, and a sintering time of 180min;

[0075] High partial pressure sintering: The sintered blank is subjected to high partial pressure sintering at a partial pressure of 80KPA, and the temperature of high partial pressure sintering is 1050°C;

[0076] Cooling: The blank that has completed high partial pressure sintering is cooled naturally to obtain alloy steel material.

[0077] Example 4

[0078] Weighing: Weigh each component according to the mass fraction of the following components to obtain stainless steel powder:

[0079] C: 0.20%, Si: 0.25%, S: 0.04%, P: 0.03%, Mn: 1.00%, Ni: 0.55%, Cr: 0.50%, Mo: 0.20%, Cu: 0.35%, O: 0.05%, N: 0.05%, and the balance is Fe.

[0080] Granulation: using an internal mixer to mix and granulate the stainless steel powder and the adhesive to obtain a granular feed; the mass fraction of the stainless steel powder is 88-92%, and the mass fraction of the adhesive is 8-12%;

[0081] Injection molding: injecting the granular feed into a mold to obtain a blank;

[0082] Thermal stripping: In a protective gas atmosphere, the blank is thermally stripped, the blank is heated to 850°C, the heating rate is 5°C / min, and the temperature is maintained for 90 to 180 minutes;

[0083] Atmosphere reduction: The blank is reduced in a reducing atmosphere, the temperature of the blank is raised to 1000-1100°C and maintained at this temperature for 60-180 minutes;

[0084] Sintering: The blank after atmosphere reduction is sintered at a partial pressure of 65KPA, a sintering temperature of 1400°C, and a sintering time of 240 minutes;

[0085] High partial pressure sintering: The sintered blank is subjected to high partial pressure sintering at a partial pressure of 85KPA, and the temperature of high partial pressure sintering is 1150°C;

[0086] Cooling: The blank that has completed high partial pressure sintering is cooled naturally to obtain alloy steel material.

[0087] The magnetic permeability test was performed on the alloy steel materials obtained in Examples 1 to 4. The test results showed that the magnetic permeability of the alloy steel materials obtained in Examples 1 to 4 was 0, which was completely non-magnetic.

[0088] It can be seen from the above embodiments that the magnetic permeability of the prepared alloy steel material is greatly reduced, and the alloy steel material can be completely non-magnetic. At the same time, since the blank is no longer subjected to heat treatment for nitrogen fixation, the local size reduction of the blank caused by heat treatment can be avoided, thereby ensuring the stability of the size of the final alloy steel product and making it easier for technicians to control the product size.

[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a steel material, characterized in that: The following steps are involved: Thermal stripping: In a protective gas atmosphere, the blank obtained by injection molding is thermally stripped, and the temperature is maintained for 90 to 180 minutes; Atmosphere reduction: performing atmosphere reduction on the blank in a reducing atmosphere, heating the blank to 1000-1100° C. and maintaining the temperature for 60-180 min; Sintering: Sinter the blank after atmosphere reduction, the sintering temperature is ≥1300℃, and the sintering time is 120~240min; High partial pressure sintering: The sintered blank is subjected to high partial pressure sintering at a partial pressure of 70-85KPA, and the temperature of high partial pressure sintering is 900-1150°C; Cooling: The blank that has completed high partial pressure sintering is cooled to obtain alloy steel material.

2. The method according to claim 1, characterized in that: In the high partial pressure sintering step, the green body is sintered at high partial pressure for 2 to 3 hours.

3. The method according to claim 1, characterized in that The protective gas in the thermal stripping step includes nitrogen.

4. The method according to claim 1, characterized in that In the thermal stripping step, the temperature of the blank is raised to 750-850°C.

5. The method according to claim 1, characterized in that The heating rate of the blank during the thermal stripping step is 3-5°C / min.

6. The method according to claim 1, characterized in that In the sintering step, the green body that has completed the atmosphere reduction is sintered at a partial pressure of 50 to 70 KPA.

7. The method according to any one of claims 1 to 6, characterized in that: Before the thermal stripping step, the following steps are also included: Granulation: Stainless steel powder and a binder are mixed and granulated to obtain a granular feed; the mass fraction of the stainless steel powder is 88-92%, and the mass fraction of the binder is 8-12%; the stainless steel powder includes Cr, Mn, Mo, N, C, and Fe elements; Injection molding: The granular feed is injection molded to obtain the blank.

8. An alloy steel material prepared according to the method according to any one of claims 1 to 7.