CN116083777A - Powder metallurgy high-performance 316L medical stainless steel and preparation method thereof - Google Patents
Powder metallurgy high-performance 316L medical stainless steel and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
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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
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
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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
- B22F1/09—Mixtures of metallic powders
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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
- B22F3/12—Both compacting and sintering
- B22F3/14—Both compacting and sintering simultaneously
- B22F3/15—Hot isostatic pressing
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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
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/14—Making metallic powder or suspensions thereof using physical processes using electric discharge
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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Abstract
The invention discloses a powder metallurgy high-performance 316L medical stainless steel and a preparation method thereof, wherein the 316L medical stainless steel is formed by uniformly mixing stainless steel powder and fine rare earth powder and then processing the stainless steel by a hot isostatic pressing mode, the addition amount of the rare earth powder is calculated by a specially designed formula on the basis of the content of characteristic elements of the stainless steel powder, various problems caused by unreasonable addition amount of the rare earth are solved, in addition, the rare earth is selected from La and Ce elements with low cost, and the content ratio of the La and the Ce is La: ce=1:1. The invention takes a specific amount of fine rare earth powder as alloying element to be fully mixed with stainless steel powder, ensures that the rare earth elements are uniformly distributed in the alloy in the solidification forming process, effectively refines the grain size of the alloy, furthest purifies impurity elements in the alloy, improves the comprehensive performance of the alloy, and can simultaneously avoid harmful effects on human bodies caused by overhigh addition amount of a certain single element.
Description
Technical Field
The invention belongs to the technical field of biomedical metal materials, and particularly relates to powder metallurgy high-performance 316L medical stainless steel and a preparation method thereof.
Background
Stainless steel is well known as one of the most widely used metallic materials in the biomedical industry today. Particularly, after the 316L medical stainless steel is successfully developed, the medical stainless steel has remarkable effect in the aspects of artificial implantation of hip joints, orthopedic devices, orthodontics, cardiovascular diseases and the like. However, with further study on the performance of the existing 316L stainless steel and feedback of clinical test results, the existing 316L medical stainless steel is found to have the following problems:
firstly, in the environment of human body fluid, the 316L medical stainless steel has higher pitting corrosion sensitivity and is easy to appearDissolution of alloying elements such as Ni, cr, mo, etc. caused by pitting corrosion, to produce metal ions (such as Cr 3+ 、Ni 2+ ) Inducing local tissue lesions of the human body;
secondly, after the 316L medical stainless steel is pitted in the body fluid environment of a human body, the mechanical property of the implant can be seriously affected, so that the 316L medical stainless steel is invalid in the actual service environment, the service life is reduced, and even the human body is seriously damaged;
thirdly, the biocompatibility is poor, the surface of the 316L medical stainless steel is basically not bioactive, the implantation effect is easily affected, and implantation failure is caused.
In conclusion, how to simultaneously improve pitting corrosion resistance and mechanical properties and enhance biocompatibility is a key technical problem in preparing 316L medical stainless steel at present. The rare earth elements can effectively purify harmful impurity elements such as oxygen, sulfur and the like in molten steel, so that the pitting corrosion resistance of the 316L medical stainless steel can be effectively improved by adding a proper amount of rare earth elements in the smelting process. However, the cast alloy structure is dendrite, and galvanic corrosion exists between dendrite phases and inter-dendrite phases caused by element segregation, which still can negatively affect the corrosion resistance of the alloy. Although element segregation can be eliminated by a subsequent heat treatment means, the grain size of the 316L medical stainless steel can grow up, and the mechanical property of the alloy is reduced. For example, homogenization for 2 hours at 1200 ℃ makes the alloy composition uniform, but the grain size is as high as several hundred microns. And secondly, the rare earth elements are added to purify harmful elements such as oxygen, sulfur and the like in the steel matrix, so that the pitting corrosion resistance of the 316L medical stainless steel can be effectively improved, but the pitting corrosion resistance of the stainless steel can be reduced due to the excessively high rare earth addition amount, and the stainless steel can be harmful to human bodies. Therefore, the calculation of the optimal rare earth addition is particularly important, and the following challenges are mainly faced at present: on one hand, the rare earth addition is less, compared with the alloy element which belongs to trace elements, the segregation phenomenon is easy to occur in the smelting process, the purification effect of the rare earth on molten steel is reduced, and the grain size of the alloy cannot be obviously refined; on the other hand, in the homogenization process, a part of rare earth elements can be dissolved into an alloy matrix at a high temperature of 1200 ℃, compared with the alloy matrix, the part of the rare earth elements can be ignored in solid solution strengthening effect, but the rare earth content for purifying impurity elements can be reduced, the purification effect is reduced, and meanwhile, the difficulty is increased for calculating the optimal rare earth addition. In addition, the biological effects of rare earth elements such as anti-tumor, anti-cancer, anticoagulation and the like can effectively improve the biocompatibility of the 316L medical stainless steel in a certain concentration range. However, too high rare earth concentration not only increases production cost, but also causes damage to human body.
In view of the above, the present inventors have proposed a powder metallurgy high-performance 316L medical stainless steel and a method for preparing the same, so as to overcome the drawbacks of the prior art.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the high-performance 316L medical stainless steel for powder metallurgy and the preparation method thereof, and the invention calculates and mixes specific amount of fine rare earth powder into the 316L medical stainless steel powder, meanwhile, the rare earth is La and Ce, the content ratio of the La and the Ce is La:Ce=1:1, and the 316L medical stainless steel with excellent performance is prepared by adopting the hot isostatic pressing technology, so that various defects of the prior 316L medical stainless steel caused by unreasonable addition of the rare earth are overcome.
The invention aims at solving the problems by the following technical scheme:
the invention provides a high-performance 316L medical stainless steel by powder metallurgy, wherein the 316L medical stainless steel is formed by uniformly mixing stainless steel powder and rare earth powder and then processing the mixture in a hot isostatic pressing mode, and the addition amount of rare earth in the 316L medical stainless steel is shown in the following formula (1):
RE (wt.%) =wt.% g+2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al) formula (1);
wherein RE (wt.%) is the total amount of added rare earth, g is the ultimate solid solubility of rare earth elements in alpha-Fe at room temperature, the rare earth elements are one or more of Ce, la and Y, the ultimate solid solubility of Ce, la and Y is 0.0048, 0.0032, 0.0001, S, al and O are the contents of elements in stainless steel powder in sequence.
Further, the total amount of the added rare earth consists of two rare earth elements of La and Ce, and the content ratio of the two rare earth elements is La:Ce=1:1, namely the addition amount of the rare earth elements in the 316L medical stainless steel is as follows: RE (wt.%) =0.5 x (0.0048+0.0032) +2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al).
Further, the rare earth powder has a particle diameter of 5 to 10 μm.
Further, the particle size of the stainless steel powder is 15-106 μm.
On the other hand, the invention provides a preparation method of powder metallurgy high-performance 316L medical stainless steel, which comprises the following specific steps:
step one, preparing stainless steel powder: selecting an as-cast 316L stainless steel bar with a set specification, preparing the as-cast 316L stainless steel bar into stainless steel powder with the particle size of 15-106 mu m by utilizing plasma rotary electrode powder making equipment, and measuring the components and the content of the stainless steel powder;
step two, selecting the granularity of rare earth powder, selecting rare earth elements and calculating the addition amount of rare earth:
selection of rare earth powder particle size: rare earth powder with granularity of 5-10 mu m is selected;
rare earth element selection: selection of rare earth element species
Calculating the addition amount of rare earth: RE (wt.%) =wt.% g+2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al), where RE (wt.%) is the total amount of added rare earth, g is the limiting solid solubility of rare earth elements in α -Fe at room temperature, S, al and O are the content of elements in the stainless steel powder;
step three, fully and uniformly mixing the stainless steel powder obtained in the step one with the rare earth powder required by calculation in the step two;
step four, preparing 316L medical stainless steel by a hot isostatic pressing mode: specifically, firstly, designing a corresponding sheath according to actual production requirements; then the powder mixed in the third step is put into the sheath, vacuumized at the temperature of 300-400 ℃ and cooled to 10 ℃ when the vacuum degree -3 Taking out the sheath for sealing welding when the temperature is lower than the preset temperature; finally, carrying out heat isostatic pressing under the conditions that the temperature is 1200-1300 ℃ and the pressure is 150MpaPress sintering for 2-4 hours;
and fifthly, machining the stainless steel prepared in the step four according to the requirement of the size of the implant to obtain the 316L medical stainless steel implant.
Further, the diameter of the 316L stainless steel bar material selected in the step one is 68mm, and the length is 650-700 mm.
Further, the model of the plasma rotary electrode powder manufacturing equipment in the step one is PREP 2000.
Further, parameters of the plasma rotary electrode powder process equipment during powder process in the step one are designed as follows: the rotating speed is 22000r/min, the feeding is 20mm/min, the current is 1000+/-100A, and the rated PV is 40mm.
Further, in the second step, the rare earth is La and Ce elements, and the content ratio of La to Ce=1 to 1.
And in the third step, stainless steel powder and rare earth powder are mixed and then screened by a round hole screen of an oversized stage, so as to obtain uniformly mixed powder.
The invention uses fine rare earth powder (5-10 μm) as alloying element, and adopts hot isostatic pressing technique to prepare high-performance 316L medical stainless steel. The addition amount of the rare earth powder is calculated according to the deduction formula provided by the invention. The biggest problem of the alloy material in the traditional vacuum arc melting is segregation of element components, and the adoption of the hot isostatic pressing technology can be effectively improved, but the main problem facing the prior 316L medical stainless steel can not be solved. Therefore, the invention considers the unique advantages of the hot isostatic pressing process, adopts the hot isostatic pressing process to prepare the alloy, and improves the uniformity of alloy components. In order to improve the comprehensive performance of the alloy, the invention adopts fine rare earth powder as alloying elements for the first time, and the fine rare earth powder is fully mixed with 316L medical stainless steel powder, so that the rare earth elements are uniformly distributed in the alloy in the solidification forming process, the grain size of the alloy is effectively refined, the impurity elements in the alloy are purified to the greatest extent, and the comprehensive performance of the alloy is improved.
In addition, the current selection method for rare earth elementsThe formula is single rare earth element, and the content is required to be determined by a trial-and-manufacture process. On one hand, the addition of excessive rare earth elements can cause the growth of inclusions in the steel, and the pitting corrosion resistance of the alloy is reduced; on the other hand, a proper amount of rare earth is beneficial to human bodies, such as: anticoagulation, anti-inflammatory, hypoglycemic, etc., but excessive rare earth elements can have adverse effects on human health and in vivo metabolism. Therefore, the determination of the rare earth addition amount in the alloy has very important significance. The main existence mode of rare earth elements in 316L stainless steel is as follows: solid solution state and compound state. The preparation method of the 316L medical stainless steel adopted by the invention is powder metallurgy, and rare earth can be approximately considered to be uniformly distributed in a steel matrix according to the powder mixing principle and the characteristics of the powder metallurgy. Thus, the limiting solid solubility may represent the maximum solubility of the different rare earth elements in the alloy; while the rare earth compound is mainly REO 2 、RE 2 O 2 S and REALO 3 These three forms, thereby determining the optimum addition amount of the rare earth element in the steel represented by the above formula (1).
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a powder metallurgy high-performance 316L medical stainless steel and a preparation method thereof, wherein fine rare earth powder is used as alloying elements for the first time, the 316L medical stainless steel is prepared by adopting a hot isostatic pressing process method, and various problems caused by unreasonable rare earth addition are thoroughly solved by adopting a designed rare earth addition calculation formula. Compared with the traditional preparation process, the comprehensive performance of the 316L medical stainless steel is remarkably improved, and the method specifically comprises the following steps: the cast segregation is reduced, the corrosion resistance of the alloy is improved, and the damage to human body is reduced; the grain size of the hot isostatic pressing state alloy can be effectively refined, the mechanical property of the alloy is improved, and the service life is prolonged; can effectively purify the alloy matrix, reduce the pitting sensitivity and improve the biocompatibility of the alloy.
2. According to the powder metallurgy high-performance 316L medical stainless steel and the preparation method thereof, the rare earth is selected as La and Ce elements, and the content ratio of La to Ce=1 to 1, so that the powder metallurgy high-performance 316L medical stainless steel has the following advantages: firstly, la and Ce are low in price compared with other rare earth elements, so that the production cost can be reduced; trivalent Ce ions have corrosion inhibition effect, so that the corrosion sensitivity of steel can be reduced; thirdly, the harmful effect on human body caused by the excessively high addition amount of a certain single element can be avoided.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate principles of the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a flow chart of the process for preparing 316L medical stainless steel according to the invention;
FIG. 2 is a microscopic image of the grain size of a 316L stainless steel prepared by a conventional method;
FIG. 3 is a microscopic view of the grain size of a 316L stainless steel produced by hot isostatic pressing (powder metallurgy) in accordance with the present invention;
FIG. 4 is a graph showing the test results of pitting corrosion resistance of 316L stainless steel prepared by different processes of embodiment 1 of the invention in NaCl solution;
FIG. 5 is a graph showing the results of mechanical property tests of 316L stainless steel prepared by the different processes of embodiment 1 of the invention.
Detailed Description
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples do not represent all implementations consistent with the invention. Rather, they are merely examples of devices that are consistent with aspects of the invention that are set forth in the following claims.
The present invention will be described in further detail below with reference to the drawings and examples for better understanding of the technical solutions of the present invention to those skilled in the art.
Referring to FIG. 1, the invention provides a powder metallurgy high-performance 316L medical stainless steel and a preparation method thereof, and the specific preparation process comprises the following steps:
step one, preparing stainless steel powder: selecting an as-cast 316L stainless steel bar with a set specification, preparing the as-cast 316L stainless steel bar into stainless steel powder with the particle size of 15-106 mu m by utilizing plasma rotary electrode powder making equipment, and measuring the components and the content of the stainless steel powder;
specifically, in the first step, the specification of the 316L stainless steel bar is 68mm in diameter and 650-700 mm in length, the model of the plasma rotary electrode powder making equipment is PREP 2000, and parameters set during powder making are as follows: the rotating speed is 22000r/min, the feeding is 20mm/min, the current is 1000+/-100A, and the rated PV is 40mm.
Step two, selecting the granularity of rare earth powder, calculating the addition amount of rare earth and selecting rare earth elements:
selection of rare earth powder particle size: rare earth powder with granularity of 5-10 mu m is selected;
calculating the addition amount of rare earth: RE (wt.%) =wt.% g+2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al), where RE (wt.%) is the total amount of added rare earth, g is the limiting solid solubility of rare earth elements in α -Fe at room temperature, S, al and O are the content of elements in the stainless steel powder;
rare earth element selection: selecting the types and the contents of rare earth according to the calculated rare earth addition; the rare earth is selected to be La and Ce elements, and the content ratio of La to Ce=1:1, because La and Ce are low in price compared with other rare earth elements, the production cost can be reduced, trivalent Ce ions have corrosion inhibition effect, and the corrosion sensitivity of steel can be reduced; meanwhile, the two components have the same proportion, so that the harmful effect on human bodies caused by the excessively high addition amount of a certain single element can be avoided.
Step three, fully and uniformly mixing the stainless steel powder obtained in the step one with the rare earth powder required by calculation in the step two; specifically, in order to ensure that the powder is fully mixed, the two kinds of powder are mixed and then are sieved by a round hole sieve with a larger level, so that the uniformly mixed powder is obtained.
Step four, preparing 316L medical stainless steel by a hot isostatic pressing mode: specifically, firstly, designing a corresponding sheath according to actual production requirements; then the powder mixed in the third step is put into the sheath, vacuumized at the temperature of 300-400 ℃ and cooled to 10 ℃ when the vacuum degree -3 Taking out the sheath for sealing welding when the temperature is lower than the preset temperature; finally, hot isostatic pressing sintering molding is carried out under the conditions that the temperature is 1200-1300 ℃ and the pressure is 150MPa, and the sintering time is 2-4 hours.
And fifthly, machining the stainless steel prepared in the step four according to the requirement of the size of the implant to obtain the 316L medical stainless steel implant.
To further verify the efficacy of the present invention, the inventors performed the following specific examples:
example 1
1) Preparation, particle size selection and component determination of 316L medical stainless steel powder:
preparation of the powder: the method comprises the steps of purchasing an as-cast 316L stainless steel bar with the diameter of 68mm and the length of 650-700 mm, preparing powder by using a plasma rotary electrode powder preparation device (PREP 2000), wherein the granularity of the prepared powder is 15-53 mu m, and the main parameters during powder preparation are as follows: rotational speed: 22000r/min, feed: 20mm/min, current: 1000±100A, rated PV:40mm.
The powder ingredients were measured as shown in table 1 below:
TABLE 1
2) Selection of rare earth powder granularity, calculation of rare earth addition amount and selection of rare earth elements:
selection of rare earth powder particle size: rare earth powder with granularity of 5-10 mu m is selected;
rare earth element selection: the rare earth element combination mode La of the embodiment is Ce=1:1;
calculating the addition amount of rare earth: RE (wt.%) =wt.% g+2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al) =0.5 x (0.0048+0.0032) +2x0.008+0.001+0.5x (0.025-2x0.008-3x0.001) =0.024, the addition amounts of ce and La each account for 50%.
3) The rare earth powder and 316L medical stainless steel powder are fully and uniformly mixed:
in order to ensure that the powder is fully mixed, the two powders are mixed and then sieved by a 63 mu m round hole sieve, so as to obtain the uniformly mixed powder.
4) Hot isostatic pressing:
the diameter of the sheath is 60mm, the height is 100mm, the mixed powder is put into the sheath, the vacuum is pumped at the temperature of 300-400 ℃ and the vacuum degree is reduced to 10 -3 Taking out the sheath for sealing welding; finally, hot isostatic pressing sintering is carried out under the conditions that the temperature is 1250-1300 ℃ and the pressure is 150MPa, and the sintering time is 3 hours.
In addition, in order to compare and illustrate the effect of the embodiment, the inventor simultaneously makes two groups of comparison experiments, and comparative example 1 is 316L medical stainless steel prepared by a conventional method; comparative example 2 differs from this example only in that the rare earth powder added is coarse powder, i.e., rare earth powder having a particle diameter of more than 10 μm.
5) The inventors tested two sets of comparative realizations and the properties of the alloys obtained in this example, with the following results:
grain refinement: scanning electron microscope, the results are shown in figures 1 and 2;
pitting resistance: an electrochemical workstation, the test results are shown in figure 3;
mechanical properties: the mechanical testing machine and the test results are shown in figure 4.
From the above experimental data results, the following conclusions can be drawn: 1. the crystal grain of the 316L medical stainless steel produced by the preparation method is greatly thinned and is reduced to 11 mu m from 52 mu m; 2. compared with the 316L medical stainless steel prepared by the conventional technical means, the pitting corrosion resistance is greatly enhanced, and the pitting corrosion potential is improved by 100mV; 3. according to the Hall-Petch formula, the strength is improved, the yield strength is improved by about 100Pa, the plasticity is improved to a certain extent, and the strength is improved by about 10%. Therefore, the preparation method provided by the invention is a method capable of effectively improving the comprehensive performance of the 316L medical stainless steel.
Example 2
1) Preparation, particle size selection and component determination of 316L medical stainless steel powder:
preparation of the powder: the method comprises the steps of purchasing an as-cast 316L stainless steel bar with the diameter of 68mm and the length of 650-700 mm, preparing powder by using a plasma rotary electrode powder preparation device (PREP 2000), wherein the granularity of the prepared powder is 53-106 mu m, and main parameters during powder preparation are as follows: rotational speed: 22000r/min, feed: 20mm/min, current: 1000±100A, rated PV:40mm.
The powder ingredients were measured as shown in table 1 below:
TABLE 1
2) Selection of rare earth powder granularity, calculation of rare earth addition amount and selection of rare earth elements:
selection of rare earth powder particle size: rare earth powder with granularity of 5-10 mu m is selected;
rare earth element selection: the rare earth element combination mode La of the embodiment is Ce=1:1;
calculating the addition amount of rare earth: RE (wt.%) =wt.% g+2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al) =0.5 x (0.0048+0.0032) +2x0.008+0.001+0.5x (0.025-2x0.008-3x0.001) =0.024, the addition amounts of ce and La each account for 50%.
3) The rare earth powder and 316L medical stainless steel powder are fully and uniformly mixed:
in order to ensure that the powder is fully mixed, the two powders are mixed and then sieved by a 150 mu m round hole sieve, so as to obtain the uniformly mixed powder.
4) Hot isostatic pressing:
the diameter of the sheath is 60mm, the height is 100mm, the mixed powder is put into the sheath, and the powder is pumped at the temperature of 300-400 DEG CVacuum, the vacuum degree is reduced to 10 -3 Taking out the sheath for sealing welding; finally, hot isostatic pressing sintering is carried out under the conditions that the temperature is 1200-1250 ℃ and the pressure is 150MPa, and the sintering time is 4 hours.
The alloy performance obtained in the embodiment 2 is tested in the same way, and the pitting corrosion resistance and the mechanical property of the alloy are equivalent to those of the embodiment 1, namely, the invention shows that the 316L medical stainless steel powder with the fine grain diameter (15-53 μm) is changed into the powder with the thicker grain diameter (53-106 μm), and the 316L medical stainless steel produced by the preparation method still has obvious performance advantages, and the utilization rate of the powder is improved within a certain range.
Example 3
1) Preparation, particle size selection and component determination of 316L medical stainless steel powder:
preparation of the powder: the method comprises the steps of purchasing an as-cast 316L stainless steel bar with the diameter of 68mm and the length of 650-700 mm, preparing powder by using a plasma rotary electrode powder preparation device (PREP 2000), wherein the granularity of the prepared powder is 15-53 mu m, and the main parameters during powder preparation are as follows: rotational speed: 22000r/min, feed: 20mm/min, current: 1000±100A, rated PV:40mm.
The powder ingredients were measured as shown in table 1 below:
TABLE 1
2) Selection of rare earth powder granularity, calculation of rare earth addition amount and selection of rare earth elements:
selection of rare earth powder particle size: rare earth powder with granularity of 5-10 mu m is selected;
rare earth element selection: the rare earth element combination mode La of the embodiment is Ce=1:1;
calculating the addition amount of rare earth: RE (wt.%) =wt.% g+2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al) =0.5 x (0.0048+0.0032) +2x0.008+0.001+0.5x (0.025-2x0.008-3x0.001) =0.024, the addition amounts of ce and La each account for 50%.
3) The rare earth powder and 316L medical stainless steel powder are fully and uniformly mixed:
in order to ensure that the powder is fully mixed, the two powders are mixed and then sieved by a 63 mu m round hole sieve, so as to obtain the uniformly mixed powder.
4) Hot isostatic pressing:
the diameter of the sheath is 60mm, the height is 100mm, the mixed powder is put into the sheath, the vacuum is pumped at the temperature of 300-400 ℃ and the vacuum degree is reduced to 10 -3 Taking out the sheath for sealing welding; finally, hot isostatic pressing sintering is carried out under the conditions that the temperature is 1275-1300 ℃ and the pressure is 150MPa, and the sintering time is 2 hours.
In addition, in order to compare and illustrate the effect of the present example, the inventors set two comparative experiments of concentration gradient of rare earth addition amount, and the addition amount of rare earth La in comparative example 3 was 0.036wt.%; the addition amount of rare earth La in comparative example 4 was 0.012wt.%, whereas in this example La was added by 0.012wt.%, and Ce was added by 0.012wt.%, i.e., 0.024wt.% total
5) The inventors tested the above two sets of comparative realizations and the alloy properties obtained in this example, with the following results:
from the above experimental data results, the following conclusions can be drawn: the yield strength MPa and the pitting corrosion potential mV of the finally obtained 316lL medical stainless steel alloy are improved by about 100% by the rare earth addition concentration calculated by the invention, and the alloy is obviously superior to other comparative examples.
The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the 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.
It will be understood that the invention is not limited to what has been described above and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (10)
1. The high-performance 316L medical stainless steel for powder metallurgy is characterized in that the 316L medical stainless steel is formed by uniformly mixing stainless steel powder and rare earth powder and then processing the mixture in a hot isostatic pressing mode, and the addition amount of rare earth in the 316L medical stainless steel is shown in the following formula (1):
RE (wt.%) =wt.% g+2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al) formula (1);
wherein RE (wt.%) is the total amount of added rare earth, g is the ultimate solid solubility of rare earth elements in alpha-Fe at room temperature, the rare earth elements are one or more of Ce, la and Y, the ultimate solid solubility of Ce, la and Y is 0.0048, 0.0032, 0.0001, S, al and O are the contents of elements in stainless steel powder in sequence.
2. The high-performance 316L medical stainless steel according to claim 1, wherein the total amount of the added rare earth is composed of two rare earth elements La and Ce, and the content ratio of the two rare earth elements la:ce=1:1, namely, the addition amount of the rare earth elements in the 316L medical stainless steel is as follows: RE (wt.%) =0.5 x (0.0048+0.0032) +2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al).
3. The high-performance 316L medical stainless steel for powder metallurgy according to claim 1, wherein the rare earth powder has a particle size of 5 to 10 μm.
4. The high-performance 316L medical stainless steel for powder metallurgy according to claim 1, wherein the particle size of the stainless steel powder is 15-106 μm.
5. The method for preparing the high-performance 316L medical stainless steel by powder metallurgy according to any one of claims 1 to 4, which is characterized by comprising the following specific steps:
step one, preparing stainless steel powder: selecting an as-cast 316L stainless steel bar with a set specification, preparing the as-cast 316L stainless steel bar into stainless steel powder with the particle size of 15-106 mu m by utilizing plasma rotary electrode powder making equipment, and measuring the components and the content of the stainless steel powder;
step two, selecting the granularity of rare earth powder, selecting rare earth elements and calculating the addition amount of rare earth:
selection of rare earth powder particle size: rare earth powder with granularity of 5-10 mu m is selected;
rare earth element selection: selection of rare earth element species
Calculating the addition amount of rare earth: RE (wt.%) =wt.% g+2wt.% s+1wt.% al+0.5 (wt.% O-2wt.% S-3wt.% Al), where RE (wt.%) is the total amount of added rare earth, g is the limiting solid solubility of rare earth elements in α -Fe at room temperature, S, al and O are the content of elements in the stainless steel powder;
step three, fully and uniformly mixing the stainless steel powder obtained in the step one with the rare earth powder required by calculation in the step two;
step four, preparing 316L medical stainless steel by a hot isostatic pressing mode: specifically, firstly, designing a corresponding sheath according to actual production requirements; then the powder mixed in the third step is put into the sheath, vacuumized at the temperature of 300-400 ℃ and cooled to 10 ℃ when the vacuum degree -3 Taking out the sheath for sealing welding when the temperature is lower than the preset temperature; finally, carrying out hot isostatic pressing sintering molding under the conditions that the temperature is 1200-1300 ℃ and the pressure is 150MPa, wherein the sintering time is 2-4 hours;
and fifthly, machining the stainless steel prepared in the step four according to the requirement of the size of the implant to obtain the 316L medical stainless steel implant.
6. The method for preparing the high-performance 316L medical stainless steel by powder metallurgy according to claim 5, wherein the diameter of the 316L stainless steel rod is 68mm and the length is 650-700 mm in the first step.
7. The method for preparing high-performance 316L medical stainless steel according to claim 5, wherein said step-A plasma rotary electrode powder manufacturing equipment is PREP 2000.
8. The method for preparing high-performance 316L medical stainless steel according to claim 5, wherein the parameters of the plasma rotary electrode powder process equipment in the step one are as follows: the rotating speed is 22000r/min, the feeding is 20mm/min, the current is 1000+/-100A, and the rated PV is 40mm.
9. The method for preparing the high-performance 316L medical stainless steel by powder metallurgy according to claim 5, wherein the rare earth in the second step is La and Ce, and the content ratio of La to Ce=1 to 1.
10. The method for preparing the high-performance 316L medical stainless steel by powder metallurgy according to claim 5, wherein in the third step, stainless steel powder and rare earth powder are mixed and then screened by a round hole screen of an oversized stage, so as to obtain uniformly mixed powder.
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