Preparation method of high-nitrogen stainless steel powder for selective laser melting

Abstract

The invention discloses a preparation method of high-nitrogen stainless steel powder for selective laser melting, which specifically comprises the following steps: (1) placing low-nitrogen stainless steel alloy powder in a nitrogen atmosphere for pre-nitrogen increase to obtain high-nitrogen stainless steel alloy powder; and (2) the low-nitrogen stainless steel alloy powder and the high-nitrogen stainless steel alloy powder are subjected to high-energy mixing, and the high-nitrogen stainless steel alloy powder is obtained. According to the method, nitrogen is added to the low-nitrogen stainless steel powder in the modes of nitrogen pre-adding, high-energy mixing and the like, the uniformity of the powder is improved, printing element segregation is reduced, the method is used for preparing the high-nitrogen stainless steel under the conventional 3D printing condition, and the nitrogen content of complex parts can be effectively increased.

Description

Technical Field

[0001] The invention relates to the technical field of alloy powder preparation, and more particularly to a method for preparing high-nitrogen stainless steel powder for selective laser melting. Background Art

[0002] High nitrogen stainless steel achieves low-cost manufacturing of stainless steel by replacing nickel with nitrogen. However, the traditional high-pressure smelting process for preparing high nitrogen stainless steel is complicated, the equipment cost is high, and machining is difficult, which limits the production and application of high nitrogen stainless steel. At present, the methods used to prepare high nitrogen stainless steel at home and abroad include nitrogen pressure smelting, powder metallurgy and surface nitriding. Among them, the nitrogen pressure smelting method has excellent product quality in the method of preparing high nitrogen stainless steel, but it is limited by its high high-pressure manufacturing cost and complex equipment.

[0003] Metal additive manufacturing technology is a preparation and processing technology based on digital models. It uses high-energy heat sources to process powder materials and quickly stack them layer by layer. It is a major breakthrough in the world's manufacturing technology in the past 30 years and is regarded as a new technology that promotes the third industrial revolution of mankind. Selective laser melting (SLM) is an important branch of metal additive manufacturing. The SLM process is a process in which high-power lasers interact with metal powder materials to melt and solidify at high speed and stack them layer by layer.

[0004] Applying laser melting technology to the preparation of high nitrogen stainless steel can achieve "net forming" of parts and reduce subsequent machining. However, the preparation of high nitrogen stainless steel powder by selective laser melting has problems such as difficulty in preparation, high cost, and poor powder formability.

[0005] Therefore, how to simplify the preparation process of high nitrogen stainless steel powder for selective laser melting, reduce costs, and improve powder formability is an urgent problem that technicians in this field need to solve. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for preparing high nitrogen stainless steel powder for selective laser melting, so as to solve the problems of preparation difficulty, high cost and poor powder formability existing in the production process of high nitrogen stainless steel powder for selective laser melting in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for preparing high nitrogen stainless steel powder for selective laser melting, specifically comprising the following steps:

[0009] (1) placing low-nitrogen stainless steel alloy powder in a nitrogen atmosphere for pre-nitrogenation to obtain high-nitrogen stainless steel alloy powder;

[0010] (2) The low nitrogen stainless steel alloy powder and the high nitrogen stainless steel alloy powder are mixed with high energy to obtain the high nitrogen stainless steel powder for selective laser melting.

[0011] Furthermore, in the above step (1), the low nitrogen stainless steel alloy powder is 1Cr18Mn12Mo3N series, with a particle size of 15 to 53 μm, and its chemical composition by mass percentage is: Si: <0.3%, Cr: 10% to 19%, N: 0.3% to 0.5%, Mn: 11% to 18%, Mo: 2% to 3.03%, Ni<0.01%, C: ≤0.1%, O: ≤0.1%, S: <0.1%, P: <0.01%, Fe: balance.

[0012] Furthermore, in the above step (1), the operation of pre-nitrogenation is specifically as follows: placing the low-nitrogen stainless steel alloy powder in a nitrogen atmosphere at normal pressure, keeping it at 800° C. for 4 hours, and then cooling it with the furnace.

[0013] A further beneficial effect of the above method is that the present invention increases the nitrogen content of the low-nitrogen stainless steel alloy powder by the pre-nitrogen addition method, thereby ensuring the printing nitrogen content.

[0014] Furthermore, in the above step (1), the operation of pre-nitrogenation is specifically as follows: placing the low-nitrogen stainless steel alloy powder in a high-pressure nitrogen atmosphere of >3MPa, keeping it at 1100°C for 3 minutes, and then cooling it with the furnace.

[0015] A further beneficial effect of the above method is that the present invention increases the nitrogen content of the low-nitrogen stainless steel alloy powder by the pre-nitrogen addition method, thereby ensuring the printing nitrogen content.

[0016] Furthermore, in the above step (2), the high-energy mixing method is a high-energy ball milling method, with a ball-to-material ratio of 4:1, a rotation speed of 600 r / min, a time of 4 h, and a protective gas of nitrogen.

[0017] A further beneficial effect of adopting the above method is that the present invention can improve the uniformity of nitrogen distribution and reduce nitrogen segregation while increasing the overall nitrogen content through high-energy mixing.

[0018] Furthermore, in the above step (2), the nitrogen content of the high nitrogen stainless steel powder for selective laser melting is 0.8% to 1.1%.

[0019] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. The present invention adopts pre-nitrogen addition, high-energy mixing and other methods to nitrogen-add low-nitrogen stainless steel powder, which improves the uniformity of the powder and reduces the segregation of printing elements. It is used to prepare high-nitrogen stainless steel under conventional 3D printing conditions and can effectively increase the nitrogen content of complex parts.

[0021] 2. The low-nitrogen stainless steel alloy powder Cr18Mn11Mo3N used in the present invention is easy to prepare, and the pre-nitrogenation method is simple, which reduces the cost of preparing high-nitrogen stainless steel printing powder, and the reaction process does not need to increase the reaction pressure, thereby improving safety.

[0022] 3. The present invention improves the nitrogen content and controllability of the high nitrogen stainless steel powder for selective laser melting by adjusting the element content of the mixed powder raw materials, effectively improves its pitting corrosion resistance, stress corrosion resistance and other properties, has higher yield and tensile strength, can prepare a variety of high nitrogen stainless steel printing powders, and increases the feasibility of high nitrogen stainless steel 3D printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM image of the 1Cr18Mn12Mo3N low nitrogen stainless steel alloy powder in Example 1;

[0024] Figure 2 This is a SEM image of the 1Cr18Mn12Mo3N series high nitrogen stainless steel alloy powder in Example 1;

[0025] Figure 3 This is the SEM image of the high nitrogen stainless steel powder used for selective laser melting in Example 1. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] The method for preparing high nitrogen stainless steel powder for selective laser melting specifically comprises the following steps:

[0029] (1) placing 1Cr18Mn12Mo3N series low nitrogen stainless steel alloy powder with a particle size of 15 to 53 μm in a nitrogen atmosphere at normal pressure, keeping the temperature at 800° C. for 4 hours, and then cooling the furnace to perform pre-nitrogen addition to obtain 1Cr18Mn12Mo3N series high nitrogen stainless steel alloy powder;

[0030] (2) 1Cr18Mn12Mo3N series low nitrogen stainless steel alloy powder and 1Cr18Mn12Mo3N series high nitrogen stainless steel alloy powder were mixed at a mass ratio of 85:15 by high energy ball milling, with a ball-to-material ratio of 4:1, a rotation speed of 600 r / min, a time of 4 h, and a protective gas of nitrogen to obtain high nitrogen stainless steel powder for selective laser melting.

[0031] Example 2

[0032] The method for preparing high nitrogen stainless steel powder for selective laser melting specifically comprises the following steps:

[0033] (1) placing 1Cr18Mn12Mo3N series low nitrogen stainless steel alloy powder with a particle size of 15 to 53 μm in a 4 MPa high pressure nitrogen atmosphere, keeping the temperature at 1100° C. for 3 min, and then cooling the furnace to perform pre-nitrogen addition to obtain 1Cr18Mn12Mo3N series high nitrogen stainless steel alloy powder;

[0034] (2) 1Cr18Mn12Mo3N series low nitrogen stainless steel alloy powder and 1Cr18Mn12Mo3N series high nitrogen stainless steel alloy powder were mixed at a mass ratio of 75:25 by high energy ball milling, with a ball-to-material ratio of 4:1, a rotation speed of 600 r / min, a time of 4 h, and a protective gas of nitrogen to obtain high nitrogen stainless steel powder for selective laser melting.

[0035] Performance Testing

[0036] 1. In Example 1, the 1Cr18Mn12Mo3N low nitrogen stainless steel alloy powder is as follows Figure 1 shown.

[0037] Depend on Figure 1 It can be seen that before nitrogen addition, the powder showed a relatively uniform distribution of coarse and fine particles at the microscopic scale. Although there was a certain proportion of fine powder and coarse powder, the particle size distribution of the powder was relatively reasonable overall.

[0038] 2. The 1Cr18Mn12Mo3N series high nitrogen stainless steel alloy powder in Example 1 is as follows Figure 2 shown.

[0039] Depend on Figure 2 It can be seen that after nitrogen addition, the particle size and distribution of the powder did not change significantly, and a certain proportion of fine powder and coarse powder still existed.

[0040] 3. The high nitrogen stainless steel powder used for selective laser melting in Example 1 is as follows: Figure 3 shown.

[0041] Depend on Figure 3 It can be seen that after high-energy mixing, more fine powder appears in the powder, but the powder particle size distribution is uniform and can meet the printing requirements.

[0042] 4. In Example 1, the target chemical composition of the high nitrogen stainless steel powder for selective laser melting, the chemical composition of the 1Cr18Mn12Mo3N series low nitrogen stainless steel alloy powder, the chemical composition of the 1Cr18Mn12Mo3N series high nitrogen stainless steel alloy powder, and the actual chemical composition of the high nitrogen stainless steel powder for selective laser melting are shown in Table 1 (arranged in order from top to bottom), respectively, in terms of mass percentage.

[0043] Table 1 Chemical composition of each sample in Example 1

[0044] Si Cr N Mn Mo Ni C O S P Fe / 20～22 1.0～1.2 11～12 3～3.5 / / / / / margin 0.24 18.92 0.42 12.63 3.03 0.009 0.033 0.08 0.004 0.01 margin 0.24 18.92 3.00 12.63 3.03 0.009 0.033 0.16 0.004 0.01 margin 0.24 18.92 0.82 12.63 3.03 0.009 0.033 0.092 0.004 0.01 margin

[0045] It can be seen from Table 1 that before nitrogen addition, the nitrogen content of the powder is 0.42%. The nitrogen content can be increased to 3% by nitrogen addition. After high-energy mixing, the final nitrogen content is 0.82%, which achieves a good overall nitrogen addition effect.

[0046] 5. In Example 2, the target chemical composition of the high nitrogen stainless steel powder for selective laser melting, the chemical composition of the 1Cr18Mn12Mo3N series low nitrogen stainless steel alloy powder, the chemical composition of the 1Cr18Mn12Mo3N series high nitrogen stainless steel alloy powder, and the actual chemical composition of the high nitrogen stainless steel powder for selective laser melting are shown in Table 2 (arranged in order from top to bottom), respectively, in terms of mass percentage.

[0047] Table 2 Chemical composition of each sample in Example 2

[0048] Si Cr N Mn Mo Ni C O S P Fe / 9～11 1.0～1.2 17～19 2～3 / / / / / margin 0.22 10.02 0.42 17.63 2.73 0.009 0.015 0.0096 0.016 0.007 margin 0.22 10.02 3.02 17.63 2.73 0.009 0.015 0.0096 0.016 0.007 margin 0.22 10.02 1.06 17.63 2.73 0.009 0.015 0.0096 0.016 0.007 margin

[0049] It can be seen from Table 2 that before nitrogen addition, the nitrogen content of the powder is 0.42%. By nitrogen addition, the nitrogen content can be increased to 3.02%. After high-energy mixing, the final nitrogen content is 1.06%, which achieves a good overall nitrogen addition effect.

[0050] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high nitrogen stainless steel powder for selective laser melting, characterized in that: The specific steps include: (1) placing low-nitrogen stainless steel alloy powder in a nitrogen atmosphere for pre-nitrogenation to obtain high-nitrogen stainless steel alloy powder; (2) The low-nitrogen stainless steel alloy powder and the high-nitrogen stainless steel alloy powder are mixed with high energy to obtain the high-nitrogen stainless steel powder for selective laser melting.

2. The method for preparing high nitrogen stainless steel powder for selective laser melting according to claim 1, characterized in that: In step (1), the low nitrogen stainless steel alloy powder is of 1Cr18Mn12Mo3N series, with a particle size of 15 to 53 μm, and its chemical composition by mass percentage is: Si: <0.3%, Cr: 10% to 19%, N: 0.3% to 0.5%, Mn: 11% to 18%, Mo: 2% to 3.03%, Ni<0.01%, C: ≤0.1%, O: ≤0.1%, S: <0.1%, P: <0.01%, Fe: balance.

3. The method for preparing high nitrogen stainless steel powder for selective laser melting according to claim 1, characterized in that: In step (1), the pre-nitrogen addition operation is specifically as follows: placing the low-nitrogen stainless steel alloy powder in a nitrogen atmosphere at normal pressure, keeping the temperature at 800° C. for 4 hours, and then cooling it with the furnace.

4. The method for preparing high nitrogen stainless steel powder for selective laser melting according to claim 1, characterized in that: In step (1), the pre-nitrogen addition operation is specifically as follows: placing the low-nitrogen stainless steel alloy powder in a high-pressure nitrogen atmosphere of >3MPa, keeping the temperature at 1100°C for 3 minutes, and then cooling it with the furnace.

5. The method for preparing high nitrogen stainless steel powder for selective laser melting according to claim 1, characterized in that: In step (2), the high-energy mixing method is a high-energy ball milling method, with a ball-to-material ratio of 4:1, a rotation speed of 600 r / min, a time of 4 hours, and a protective gas of nitrogen.

6. The method for preparing high nitrogen stainless steel powder for selective laser melting according to claim 1, characterized in that: In step (2), the nitrogen content of the high nitrogen stainless steel powder for selective laser melting is 0.8% to 1.1%.

Images