CN112517911B - Sintering process of high-nitrogen nickel-free stainless steel - Google Patents
Sintering process of high-nitrogen nickel-free stainless steel Download PDFInfo
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- CN112517911B CN112517911B CN202011420613.2A CN202011420613A CN112517911B CN 112517911 B CN112517911 B CN 112517911B CN 202011420613 A CN202011420613 A CN 202011420613A CN 112517911 B CN112517911 B CN 112517911B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
- B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
- B22F3/101—Changing atmosphere
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
Abstract
The invention discloses a high-nitrogen nickel-free stainless steel sintering process, which comprises the following steps of: step one, preparing a high-nitrogen nickel-free stainless steel feed: mixing high-nitrogen nickel-free stainless steel powder and a binder according to the proportion of 8:1, uniformly mixing, and then placing the obtained mixture into a feeding crusher to prepare granular feeding with uniform size; step two, injection molding; step three, degreasing; sintering nitriding; step five, argon sintering; step six, secondary sintering nitriding; and seventhly, carrying out solution treatment on the product, and removing chromium nitride precipitates in the product. According to the invention, the sintering defective products are sintered and qualified through Ar reduction and secondary sintering nitriding, so that the rejection rate is greatly reduced, the cost is reduced, and the method can be used for mass production.
Description
Technical Field
The invention relates to the technical field of stainless steel, in particular to a high-nitrogen nickel-free stainless steel sintering process.
Background
Austenitic stainless steel is one of the most important engineering materials, such as 316l, aisi, etc., and is widely used in industry due to its advantages of strong corrosion resistance, high ductility, non-magnetic property, etc. The nickel element is one of elements capable of stabilizing an austenitic structure, and thus, a large amount of nickel is contained in the conventional stainless steel. Nickel has limited application in the consumer electronics and biomedical fields due to its poor biocompatibility, high cost, and the like. In recent years, nitrogen has been introduced into austenitic stainless steel to replace nickel, and high nitrogen nickel-free stainless steel has emerged. The solid solubility of nitrogen in austenite is much higher than in liquid iron, and therefore powder metallurgy has the irreplaceable advantage of producing high nitrogen nickel-free stainless steel.
Powder injection molding-sintering nitriding processes are emerging processes for producing high nitrogen nickel-free stainless steel, which have begun to be applied in industry. Although high nitrogen nickel-free stainless steel has many advantages over conventional austenitic stainless steel, such as good biocompatibility, good corrosion resistance, higher strength and hardness, better stabilization of austenitic structure, etc. However, the existing high-nitrogen stainless steel sintering process has industrial difficulties, and the main reasons are unstable sintering, large fluctuation of sintering size and no mass production.
Disclosure of Invention
The invention aims to provide a high-nitrogen nickel-free stainless steel sintering process which aims at overcoming the defects of the prior art, reduces the defective products after Ar reduction, sinters and meets the sintering standard, thereby greatly reducing the rejection rate, reducing the cost and realizing mass production.
In order to achieve the above object, the present invention is achieved by the following technical scheme.
A high nitrogen nickel-free stainless steel sintering process comprises the following steps:
step one, preparing a high-nitrogen nickel-free stainless steel feed: mixing high-nitrogen nickel-free stainless steel powder and a binder according to the proportion of 8:1, uniformly mixing, and then placing the obtained mixture into a feeding crusher to prepare granular feeding with uniform size;
step two, injection molding: molding the feed obtained in the step one in an injection molding machine to obtain an injection blank with a desired structure;
step three, degreasing: placing the injection blank obtained in the second step on a special ceramic jig, and degreasing by using a special degreasing furnace to obtain a degreased piece;
sintering nitriding: and (3) placing the degreased piece obtained in the step (III) into a sintering furnace for nitriding and sintering to obtain a high-nitrogen nickel-free stainless steel sintered piece, wherein the specific steps are as follows:
a. degreasing under negative pressure: nitrogen is introduced, and the furnace temperature is heated to 850 ℃;
b. and (3) vacuum internal combustion: vacuumizing a sintering furnace, maintaining the furnace temperature at 850 ℃, and preserving the heat for 60min;
c. partial pressure sintering: introducing nitrogen, increasing partial pressure sintering pressure, raising the furnace temperature to 1050 ℃, and preserving heat for 60min;
d. partial pressure sintering is carried out: introducing nitrogen, raising the furnace temperature to 1240 ℃, and preserving heat for 210min; then the furnace temperature is reduced to 900 ℃;
e. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
step five, argon sintering: and (3) placing defective sintered parts in the step (IV) into the sintering furnace for argon sintering to obtain compact sintered parts, wherein the specific steps are as follows:
f. and (3) vacuum internal combustion: vacuumizing the sintering furnace, maintaining the furnace temperature at 1050 ℃, and preserving the heat for 210min;
g. partial pressure sintering: argon is introduced, partial pressure sintering pressure is increased, furnace temperature is increased to 1240 ℃, and heat preservation is carried out for 210min; then the furnace temperature is reduced to 1050 ℃;
h. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
step six, secondary sintering nitriding: and (3) putting the compact sintered part prepared in the fifth step into the sintering furnace for secondary nitriding sintering to prepare a high-nitrogen nickel-free stainless steel product with stable size, wherein the method comprises the following specific steps of:
i. and (3) vacuum internal combustion: vacuumizing the sintering furnace, maintaining the furnace temperature at 1050 ℃, and preserving the heat for 210min;
j. partial pressure sintering: introducing nitrogen, increasing partial pressure sintering pressure, raising the furnace temperature to 1200 ℃, and preserving heat for 60min; then the furnace temperature is reduced to 1050 ℃;
k. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
and seventhly, carrying out solution treatment on the product, and removing chromium nitride precipitates in the product.
Wherein the nitrogen content of the high-nitrogen nickel-free stainless steel feed in the step one is less than 0.3%.
Wherein the nitrogen content of the compact sintered part obtained in the step five is less than 0.5%.
Wherein the nitrogen content of the high-nitrogen nickel-free stainless steel product with stable size in the step six is more than 0.65 percent.
The beneficial effects of the invention are as follows: the invention relates to a high-nitrogen nickel-free stainless steel sintering process, which comprises the following steps of: step one, preparing a high-nitrogen nickel-free stainless steel feed: mixing high-nitrogen nickel-free stainless steel powder and a binder according to the proportion of 8:1, uniformly mixing, and then placing the obtained mixture into a feeding crusher to prepare granular feeding with uniform size; step two, injection molding: molding the feed obtained in the step one in an injection molding machine to obtain an injection blank with a desired structure; step three, degreasing: placing the injection blank obtained in the second step on a special ceramic jig, and degreasing by using a special degreasing furnace to obtain a degreased piece; sintering nitriding: and (3) placing the degreased piece obtained in the step (III) into a sintering furnace for nitriding and sintering to obtain a high-nitrogen nickel-free stainless steel sintered piece, wherein the specific steps are as follows: a. degreasing under negative pressure: nitrogen is introduced, and the furnace temperature is heated to 850 ℃; b. and (3) vacuum internal combustion: vacuumizing a sintering furnace, maintaining the furnace temperature at 850 ℃, and preserving the heat for 60min; c. partial pressure sintering: introducing nitrogen, increasing partial pressure sintering pressure, raising the furnace temperature to 1050 ℃, and preserving heat for 60min; d. partial pressure sintering is carried out: introducing nitrogen, raising the furnace temperature to 1240 ℃, and preserving heat for 210min; then the furnace temperature is reduced to 900 ℃; e. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃; step five, argon sintering: and (3) placing defective sintered parts in the step (IV) into the sintering furnace for argon sintering to obtain compact sintered parts, wherein the specific steps are as follows: f. and (3) vacuum internal combustion: vacuumizing the sintering furnace, maintaining the furnace temperature at 1050 ℃, and preserving the heat for 210min; g. partial pressure sintering: argon is introduced, partial pressure sintering pressure is increased, furnace temperature is increased to 1240 ℃, and heat preservation is carried out for 210min; then the furnace temperature is reduced to 1050 ℃; h. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃; step six, secondary sintering nitriding: and (3) putting the compact sintered part prepared in the fifth step into the sintering furnace for secondary nitriding sintering to prepare a high-nitrogen nickel-free stainless steel product with stable size, wherein the method comprises the following specific steps of: i. and (3) vacuum internal combustion: vacuumizing the sintering furnace, maintaining the furnace temperature at 1050 ℃, and preserving the heat for 210min; j. partial pressure sintering: introducing nitrogen, increasing partial pressure sintering pressure, raising the furnace temperature to 1200 ℃, and preserving heat for 60min; then the furnace temperature is reduced to 1050 ℃; k. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃; and seventhly, carrying out solution treatment on the product, and removing chromium nitride precipitates in the product. According to the invention, the sintering defective products are sintered and qualified through Ar reduction and secondary sintering nitriding, so that the rejection rate is greatly reduced, the cost is reduced, and the method can be used for mass production.
Detailed Description
The invention will be described with reference to specific embodiments.
A high nitrogen nickel-free stainless steel sintering process comprises the following steps:
step one, preparing a high-nitrogen nickel-free stainless steel feed: mixing high-nitrogen nickel-free stainless steel powder and a binder according to the proportion of 8:1, uniformly mixing, and then placing the obtained mixture into a feeding crusher to prepare granular feeding with uniform size;
step two, injection molding: molding the feed obtained in the step one in an injection molding machine to obtain an injection blank with a desired structure;
step three, degreasing: placing the injection blank obtained in the second step on a special ceramic jig, and degreasing by using a special degreasing furnace to obtain a degreased piece;
sintering nitriding: and (3) placing the degreased piece obtained in the step (III) into a sintering furnace for nitriding and sintering to obtain a high-nitrogen nickel-free stainless steel sintered piece, wherein the specific steps are as follows:
a. degreasing under negative pressure: introducing nitrogen and heating the furnace to 850 ℃, wherein the step is to remove the adhesive which is not removed cleanly in the step three; b. and (3) vacuum internal combustion: vacuumizing a sintering furnace, maintaining the furnace temperature at 850 ℃, and preserving the heat for 60min;
c. partial pressure sintering: introducing nitrogen, increasing partial pressure sintering pressure, raising the furnace temperature to 1050 ℃, and preserving heat for 60min, wherein the step is to prevent ferrite in the product from leaving over, so that the magnetic permeability of the product is out of tolerance;
d. partial pressure sintering is carried out: introducing nitrogen, raising the furnace temperature to 1240 ℃, and preserving heat for 210min; then the furnace temperature is reduced to 900 ℃, and the product is sintered and compacted in the step;
e. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
step five, argon sintering: and (3) placing defective sintered parts in the step (IV) into the sintering furnace for argon sintering to obtain compact sintered parts, wherein the specific steps are as follows:
f. and (3) vacuum internal combustion: vacuumizing the sintering furnace, maintaining the furnace temperature at 1050 ℃, and preserving the heat for 210min;
g. partial pressure sintering: argon is introduced, partial pressure sintering pressure is increased, furnace temperature is increased to 1240 ℃, and heat preservation is carried out for 210min; then the furnace temperature is reduced to 1050 ℃;
h. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
step six, secondary sintering nitriding: and (3) putting the compact sintered part prepared in the fifth step into the sintering furnace for secondary nitriding sintering to prepare a high-nitrogen nickel-free stainless steel product with stable size, wherein the method comprises the following specific steps of:
i. and (3) vacuum internal combustion: vacuumizing the sintering furnace, maintaining the furnace temperature at 1050 ℃, and preserving the heat for 210min;
j. partial pressure sintering: introducing nitrogen, increasing partial pressure sintering pressure, raising the furnace temperature to 1200 ℃, and preserving heat for 60min; then the furnace temperature is reduced to 1050 ℃;
k. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
and step seven, carrying out solution treatment on the product to remove chromium nitride precipitates in the product, wherein the existence of the chromium nitride precipitates can reduce the rust resistance of the product, and when chromium exists in a chromium nitride form, the rust resistance of the chromium element can disappear, so that after the stainless steel is sintered and nitrided, the solution annealing treatment in step seven is needed to remove the chromium nitride precipitates.
Further, the nitrogen content of the high-nitrogen nickel-free stainless steel feed in the step one is less than 0.3%.
Further, the nitrogen content of the compact sintered part obtained in the step five is less than 0.5%.
Further, the nitrogen content of the high nitrogen nickel-free stainless steel product of the step six is more than 0.65%.
To explain further, the invention prepares the high-nitrogen nickel-free stainless steel with stable size and improves the Gao Zhicheng yield under the condition of not affecting the material performance; sintering the primary sintering defective products, and then nitriding for the second time to obtain the high-nitrogen nickel-free stainless steel with expected size, so that the rejection rate of the process is greatly reduced, and the cost is effectively reduced.
The foregoing is merely exemplary of the present invention, and those skilled in the art should not be considered as limiting the invention, since modifications may be made in the specific embodiments and application scope of the invention in light of the teachings of the present invention.
Claims (4)
1. The high-nitrogen nickel-free stainless steel sintering process is characterized by comprising the following steps of:
step one, preparing a high-nitrogen nickel-free stainless steel feed: mixing high-nitrogen nickel-free stainless steel powder and a binder according to the proportion of 8:1, uniformly mixing, and then placing the obtained mixture into a feeding crusher to prepare granular feeding with uniform size;
step two, injection molding: molding the feed obtained in the step one in an injection molding machine to obtain an injection blank with a desired structure;
step three, degreasing: placing the injection blank obtained in the second step on a special ceramic jig, and degreasing by using a special degreasing furnace to obtain a degreased piece;
sintering nitriding: and (3) placing the degreased piece obtained in the step (III) into a sintering furnace for nitriding and sintering to obtain a high-nitrogen nickel-free stainless steel sintered piece, wherein the specific steps are as follows:
a. degreasing under negative pressure: nitrogen is introduced, and the furnace temperature is heated to 850 ℃;
b. and (3) vacuum internal combustion: vacuumizing a sintering furnace, maintaining the furnace temperature at 850 ℃, and preserving the heat for 60min;
c. partial pressure sintering: introducing nitrogen, increasing partial pressure sintering pressure, raising the furnace temperature to 1050 ℃, and preserving heat for 60min;
d. partial pressure sintering is carried out: introducing nitrogen, raising the furnace temperature to 1240 ℃, and preserving heat for 210min; then the furnace temperature is reduced to 900 ℃;
e. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
step five, argon sintering: and (3) placing defective sintered parts in the step (IV) into the sintering furnace for argon sintering to obtain compact sintered parts, wherein the specific steps are as follows:
f. and (3) vacuum internal combustion: vacuumizing the sintering furnace, maintaining the furnace temperature at 1050 ℃, and preserving the heat for 210min;
g. partial pressure sintering: argon is introduced, partial pressure sintering pressure is increased, furnace temperature is increased to 1240 ℃, and heat preservation is carried out for 210min; then the furnace temperature is reduced to 1050 ℃;
h. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
step six, secondary sintering nitriding: and (3) putting the compact sintered part prepared in the fifth step into the sintering furnace for secondary nitriding sintering to prepare a high-nitrogen nickel-free stainless steel product with stable size, wherein the method comprises the following specific steps of:
i. and (3) vacuum internal combustion: vacuumizing the sintering furnace, maintaining the furnace temperature at 1050 ℃, and preserving the heat for 210min;
j. partial pressure sintering: introducing nitrogen, increasing partial pressure sintering pressure, raising the furnace temperature to 1200 ℃, and preserving heat for 60min; then the furnace temperature is reduced to 1050 ℃;
k. forced cooling: introducing nitrogen, increasing the pressure, and rapidly cooling the furnace temperature to 60 ℃;
and seventhly, carrying out solution treatment on the product, and removing chromium nitride precipitates in the product.
2. The high nitrogen nickel-free stainless steel sintering process according to claim 1, wherein the process comprises the following steps: the nitrogen content of the high-nitrogen nickel-free stainless steel feed in the step one is less than 0.3%.
3. The high nitrogen nickel-free stainless steel sintering process according to claim 1, wherein the process comprises the following steps: and the nitrogen content of the compact sintered piece obtained in the step five is less than 0.5%.
4. The high nitrogen nickel-free stainless steel sintering process according to claim 1, wherein the process comprises the following steps: and the nitrogen content of the high-nitrogen nickel-free stainless steel product with stable size in the step six is more than 0.65%.
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| CN113502428B (en) * | 2021-06-23 | 2022-06-14 | 华南理工大学 | Method for preparing high-nitrogen nickel-free austenitic stainless steel and product thereof |
| CN113547119B (en) * | 2021-07-20 | 2022-07-22 | 东莞市华研新材料科技有限公司 | MIM316 sintering process |
| CN113732287A (en) * | 2021-09-13 | 2021-12-03 | 东莞市环力智能科技有限公司 | Non-magnetic sintering process for 17-4 products |
| CN114082950B (en) * | 2021-11-04 | 2024-04-16 | 金上晋科技(东莞)有限公司 | Method for improving mechanical properties of SUS630 stainless steel injection molding finished product |
| CN114182178B (en) * | 2021-12-09 | 2022-10-18 | 广州金南磁性材料有限公司 | Preparation method and application of high-nitrogen nickel-free austenitic stainless steel |
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| JPH0717983B2 (en) * | 1988-08-20 | 1995-03-01 | 川崎製鉄株式会社 | Method for producing high nitrogen stainless steel sintered body |
| JP3383099B2 (en) * | 1994-12-28 | 2003-03-04 | 三菱製鋼株式会社 | High corrosion resistant sintered products |
| CN107598161B (en) * | 2017-08-30 | 2019-07-12 | 中核四0四有限公司 | MOX pellet sintering atmosphere control method |
| CN111451507A (en) * | 2020-05-27 | 2020-07-28 | 江苏省海洋资源开发研究院(连云港) | Near-net forming method of high-nitrogen nickel-free austenitic stainless steel |
| CN111621705B (en) * | 2020-06-19 | 2021-05-25 | 深圳市泛海统联精密制造股份有限公司 | Preparation method of nickel-free duplex stainless steel |
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