A kind of nitrogenous nickelles stainless steel and metallurgy forming process for powder thereof
Technical field
The present invention relates to the stainless steel production field, particularly relate to a kind of nitrogenous nickelles stainless steel and powder metallurgy preparation technology thereof.
Background technology
Present widely used chromium-nickel austenitic stainless steel exists following subject matter: (1) hardness is on the low side, can't carry out phase transformation strengthening, and wear resistance is relatively poor; (2) the quick growth of stainless steel output and breed structure is unreasonable, causes the nickel resources critical shortage, and price rises steadily, and cost pressure strengthens; (3) contain the apparatus that nickel and stainless steel directly contacts as human body implant and various human bodies and can produce " nickel is quick " effect, HUMAN HEALTH is caused damage.These unfavorable factors have limited nickeliferous stainless application.Therefore, research prepares the resource-conserving nickelles stainless steel with other element replacement nickel becomes the frontier that the Materials science worker makes great efforts to seek.Nitrogen can replace the nickel in the austenitic stainless steel, economizes on resources environmental friendliness, economic environmental protection.Nitrogenous austenitic stainless steel has become the preferred material of following Sustainable development.
The preparation method of high nitrogen stainless steel mainly contains smelting process and powder metallurgy process.Can obtain high nitrogen content and high-strength and high ductility high nitrogen stainless steel material by the high pressure melting, but high pressure melting method equipment complexity, investment are greatly, development is restricted, and the nitrogen element skewness of obtained nitrogenous nickelles stainless steel material is easy to generate segregation phenomena.Document Simmons J W.Overview:high-nitrogen alloying of stainless steels[J] .Materials Science and Engineering, 1996, A207:159-169 and document Simmons J.W, Kemp W E, Dunning J S.The PM processing ofhigh-nitrogen stainless steels[J] .JOM, 1996,48 (4): 20-23 analyzed powder metallurgy prepare high nitrogen stainless steel can crystal grain thinning, reduce composition and microstructure segregation, obtain the distribution of uniform alloy constituent element and nitrogen, can relatively easily obtain more high nitrogen-containing, can realize near-net forming, also can prepare the high nitrogen stainless steel goods that utilize casting forging method to be difficult to make.And this method technology is flexible, fund input is few, and cost is lower.
Document [Li Songlin, Qu Xuanhui, Li Yimin, Huang Baiyun. external injection forming stainless steel progress of research [J]. powder metallurgy industry, 2001,11 (3): 18-20] and document [Tandon R, Simmons JW, Russell J H, Covino B S.Properties of high-strength nitrogen-alloyed stainless steel consolidated by metal injectionmolding[J] .Advances in Powder Metallurgy and Particulate Materials, 1997,3 (18): 123-134] reported employing metal injection moulding (Metal Injection Molding, abbreviation MIM) method can be produced complex-shaped, the stainless steel components of excellent property.Its goods relative density can reach more than 95%, and crystal grain is tiny, homogeneous microstructure, its yield strength, tensile strength, toughness, erosion resistance etc. all are higher than or are equivalent to casting and forged article, and the MIM technological artifacts need not follow-up machining or the only a spot of machining of need.But the granularity of MIM technical requirements powder<20 μ m, the easy sintered compact that obtains high compactness under this kind condition; And obtaining the high-tension apparatus that the superfine aerosolization powder of granularity needs requirements at the higher level, the powder by atomization cost is bigger.
Therefore,, reduce whole technology cost for making the equally distributed nickelles stainless steel material of high-performance, high compactness, complicated shape, high nitrogen-containing and nitrogen element, need be to being that the powder metallurgy MIM technology of raw material is improved than coarse meal.
Summary of the invention
The object of the present invention is to provide a kind of nitrogenous nickelles stainless steel material and metallurgy forming process for powder thereof, the nickel that solution contains the nickel and stainless steel existence costs an arm and a leg and the medical problems such as harm that contain nickel and stainless steel to HUMAN HEALTH, obtained the densification degree height, the resource-conserving nickelles stainless steel material of mechanical property, excellent anti-corrosion performance reduces the technology cost.
The composition quality per-cent of the nitrogenous nickelles stainless steel of the present invention is: Cr16.5%~17.5%, and Mn10%~12%, Mo2.0%~2.5%, C≤0.02%, Si≤0.5%, P+S≤0.025%, N0.6%~1.0%, surplus is iron and trace impurity.
The concrete steps of the metallurgy forming process for powder of nitrogenous nickelles stainless steel are: after weighing is good than (PW:HDPE:SA is 65~70:29~34:1~6) according to the certain mass mark with binding agent paraffin (PW), high density polyethylene(HDPE) (HDPE), stearic acid (SA), melt each constituent element and stir, be broken into particulate state after the cooling; Multicomponent binding agent and raw material powder are carried out mixing on rubber mixing machine according to 60%~66% loading capacity, melting temperature is 130~150 ℃, mixing time 60~120min; Mixingly be broken into the injection feeding after evenly; Injection obtains the base that is shaped on the feeding injector then, 155~175 ℃ of injection temperatures (annotating the mouth place), and injection pressure is 85~110MPa, through the injection base smooth surface that injection moulding machine obtains, inner zero defect; The injection base soaks 10~12h earlier in trieline solution, obtain the solvent degreasing base; Hot degreasing is carried out in dry back in debinding furnace under inert atmosphere, obtain having the hot degreasing base of certain intensity; Under different sintering conditions, carry out the nitrogen-based atmosphere sintering then and obtain sintered compact, nitrogen-based atmosphere is nitrogen or nitrogen/hydrogen gas mixture, gas flow is 1.5~2L/min, temperature rise rate is 8~10 ℃/min, sintering temperature is 1280 ℃~1360 ℃, sintering time is 30min~150min, and sintering pressure is 0.05~0.7MPa.
The thick stainless steel raw material powder that the metallurgy forming process for powder of nitrogenous nickelles stainless steel adopts, its globule size is-500~-300 orders.
The hot degreasing of solvent degreasing base is at H among the described preparation technology
2Perhaps in the inert atmosphere with dried solvent degreasing base heating (in the SX2-10-13 resistance furnace), be raised to 200 ℃, insulation 30min with the speed of 1~3 ℃/min; Speed with 1~2 ℃/min is raised to 300 ℃, insulation 30min; Speed with 1~2 ℃/min is warmed up to 350 ℃, insulation 60min; Speed with 1~2 ℃/min is warmed up to 450 ℃, insulation 30min; Speed with 1~2 ℃/min is warmed up to 500 ℃, insulation 60min; Speed with 5~10 ℃/min is warmed up to 800~900 ℃ then, insulation 60min; Cool to room temperature at last with the furnace and obtain the hot degreasing blank of certain intensity.
In the described preparation process, to relative density〉90% sintered compact is at N
2Carrying out hot isostatic pressing HIP densification technology under the protection handles.It is 100~130MPa that HIP handles heat preservation pressure, and temperature is 1100~1300 ℃, and soaking time is 60~180min.
The invention has the advantages that:
1, since the solubleness of nitrogen in steel in solid-state much larger than the solubleness in molten steel.Adopt powder metallurgy process to carry out Solid Solution Nitriding, can obtain the high stainless material of nitrogen content.Powder metallurgy is that raw material carries out material preparation with the powder, can relatively easily obtain higher nitrogen content and the distribution of nitrogen uniformly.Made the austenitic stainless steel material of nitrogen content with injection molding process greater than 0.6wt%.
2, preparation high-nitrogen nickel-free stainless steel has solved nickel austenite stainless steel and has been applied to " nickel is quick " effect that medical field occurs, and can reduce nickeliferous stainless product cost.Nitrogen replaces nickel as the alloying element in the austenitic stainless steel, saves resource, environmental friendliness, economic environmental protection.
3, the present invention is a raw material with thick nitrogen-contained stainless steel powder, and metal injection moulding MIM technology and hot isostatic pressing HIP densification technology are combined, and has reduced Financial cost, can obtain high compactness, high performance no nickel resources saving type stainless material.The material relative density that obtains〉98%, mechanical property and corrosion resistance nature are better than traditional austenitic stainless steel.The nickelles stainless steel material that this technology makes, meet that developing material proposes economize on resources, health environment-friendly, the better requirement of performance.
4, adopt injection molding process can make complicated shape than gadget, need not follow-up machining or only need a spot of machining.This technology can produce and be applicable to industrial production and the required various parts of daily life, and especially nickel-less austenitic stainless steel need be widely used in biomedical sector.
Embodiment
Embodiment 1: granularity is-400 purpose nitrogen-contained stainless steel powder and multicomponent binding agent
The main chemical of the nitrogenous nickelles stainless steel powder of-400 order aerosolizations is Cr17.1%, Mn11.7%, Mo2.41%, N0.46%, C0.019%, Si0.5%, P+S0.024% and micro impurity element, and surplus is Fe; The quality proportioning of binding agent paraffin (PW), high density polyethylene(HDPE) (HDPE), three kinds of polymkeric substance of stearic acid (SA) is defined as PW:HDPE:SA=70:29:1.
With binding agent and raw material powder is that 64% loading capacity is carried out mixing on two roll rubber mixing machines according to volume fraction, melting temperature is 140 ℃, mixing time 90min, mixingly be broken into the injection feeding after evenly, then injection on the feeding injector is obtained the base that is shaped, 170 ℃ of injection temperatures (annotating the mouth place), injection pressure is 100MPa.Injection base smooth surface, inner zero defect.The injection base carries out solvent degreasing 10h earlier in trieline solution, to slough the above polymkeric substance of 50wt%, then in nitrogen N
2In be to carry out hot degreasing in the debinding furnace, obtain perfect sunken hot degreasing base with certain intensity.
Wherein hot degreasing process is as follows: at N
2In the atmosphere with dried solvent degreasing base in the SX2-10-13 resistance furnace, be raised to 200 ℃ with the speed of 2 ℃/min, insulation 30min; Speed with 1 ℃/min is raised to 300 ℃, insulation 30min; Speed with 1 ℃/min is warmed up to 350 ℃, insulation 60min; Speed with 1 ℃/min is warmed up to 450 ℃, insulation 30min; Speed with 1 ℃/min is warmed up to 500 ℃, insulation 60min; Speed with 8 ℃/min is warmed up to 850 ℃ then, insulation 60min; Cool to room temperature at last with the furnace and obtain the hot degreasing blank of certain intensity.
Hot degreasing blank is placed the N that flows
2In the atmosphere, degreasing blank is carried out normal pressure-sintered, gas flow is 1.5L/min, and temperature rise rate is 8 ℃/min, and sintering temperature is 1340 ℃, and sintering time is 120min, and sintering pressure is 0.1MPa.
The composition that obtains nitrogenous nickelles stainless steel is (mass percent): Cr16.9%, Mn11.3%, Mo2.45%, N0.78%, C0.015%, Si0.5%, P+S0.005% and micro impurity element, and surplus is Fe
With N
2Be transmission medium, sintered compact is carried out the HIP densification in the hope of obtaining more high-compactness and more high performance material.It is 120MPa that the preferable HIP that determines handles heat preservation pressure, and temperature is 1200 ℃, and soaking time is 120min.The relative density that HIP handles back stainless steel sample reaches 98.1%, and nitrogen content reaches 0.83%, yield strength σ
0.2=565MPa, tensile strength sigma=925MPa, unit elongation δ
0.5=46.0%, relative reduction in area can reach 39.5%, the Ep of anti-the pitting potential〉900mv.
Embodiment 2: granularity is-500 purpose nitrogen-contained stainless steel powder and multicomponent binding agent
The Chemical Composition of-500 order aerosolization powder of stainless steel be Cr17.0%, Mn11.3%, Mo2.30%, N0.42%, C0.018%, Si0.5%, P+S0.020% with and micro impurity element, surplus is Fe; The quality proportioning of binding agent paraffin (PW), high density polyethylene(HDPE) (HDPE), three kinds of polymkeric substance of stearic acid (SA) is defined as PW:HDPE:SA=68:29:3.
With binding agent and raw material powder is that 65% loading capacity is carried out mixing on two roll rubber mixing machines according to volume fraction; melting temperature is 140 ℃; time 90min is mixing even to guarantee; be broken into the injection feeding then; then injection on the feeding injector is obtained the base that is shaped; 165 ℃ of injection temperatures (annotating the mouth place), injection pressure is 100MPa.Injection base smooth surface, inner zero defect.The injection base carries out solvent degreasing 10h earlier in trieline solution, to slough the above polymkeric substance of 50wt%, then in nitrogen N
2In be to carry out hot degreasing in the debinding furnace, obtain perfect sunken degreasing base with certain intensity.
Wherein hot degreasing process is as follows: at N
2In the atmosphere with dried solvent degreasing base in the SX2-10-13 resistance furnace, be raised to 200 ℃ with the speed of 2 ℃/min, insulation 30min; Speed with 1 ℃/min is raised to 300 ℃, insulation 30min; Speed with 1 ℃/min is warmed up to 350 ℃, insulation 60min; Speed with 1 ℃/min is warmed up to 450 ℃, insulation 30min; Speed with 1 ℃/min is warmed up to 500 ℃, insulation 60min; Speed with 8 ℃/min is warmed up to 800 ℃ then, insulation 60min; Cool to room temperature at last with the furnace and obtain the hot degreasing blank of certain intensity.
Hot degreasing blank is placed the N that flows
2In the atmosphere degreasing blank is carried out normal pressure-sintered, N
2Gas flow is 1.5L/min, and temperature rise rate is 8 ℃/mim, and sintering temperature is 1320 ℃, and sintering time is 120min, and sintering pressure is 0.1MPa.
The composition that obtains nitrogenous nickelles stainless steel is (mass percent): Cr17.0%, Mn11.5%, Mo2.35%, N0.85%, C0.01%, Si0.5%, P+S0.002% and micro impurity element, and surplus is Fe
With N
2Be transmission medium, this sintered article is carried out the HIP densification in the hope of obtaining the more performance of high-compactness and Geng Gao.It is 120MPa that the preferable HIP that determines handles heat preservation pressure, and temperature is 1200 ℃, and soaking time is 150min.The relative density that HIP handles back stainless steel sample reaches 98.7%, and nitrogen content reaches 0.85%, yield strength σ
0.2=581MPa, tensile strength sigma=973MPa, unit elongation δ
0.5=48.4%, relative reduction in area can reach 42.3%, the Ep of anti-the pitting potential〉900mv.