CN101353770A - High strength stainless gear steel and preparation thereof - Google Patents

Abstract

The invention discloses a high-strength stainless pinion steel and a preparation method thereof. The high-strength stainless pinion steel is characterized by comprising the chemical elements proportioning by weight percentage as follows: 0.10 percent to 0.20 percent of C, less than or equal to 0.50 percent of Mn, less than or equal to 0.50 percent of Si, 12.5 percent to 15.0 percent of Cr, 1.50 percent to 3.00 percent of Ni, 4.00 percent to 6.50 percent of Mo, 0.5 percent to 0.85 percent of V, 12.5 percent to 14.5 percent of Co, 0.20 percent to 1.50 percent of W and less than or equal to 0.20 percent of Nb, and the rest are Fe and other unavoidable impurities. The manufacturing method thereof comprises the following steps of: preparation of raw materials, injection of electrode bars by a vacuum inductance furnace, air cooling, machining, re-melting by a vacuum consumable electrode melting furnace, steel ingot annealing and machining, forging, upsetting, molding by forging or by rolling and annealing. The high-strength stainless pinion steel and preparation method of the invention can satisfy the requirements of new-generation pinion steel and realize good matching of high strength, high stiffness, high toughness and corrosion resistance.

Description

A kind of high strength stainless gear steel and preparation method thereof

Technical field

The invention belongs to the metallurgical material field, particularly a kind of high strength stainless gear steel in the field of metallurgy and preparation method thereof.

Background technology

Both at home and abroad the development trend of Pinion Steel mainly is to improve intensity, toughness, anti-corrosion, heatproof and improve work-ing life.Pinion Steel is to be the low-alloy case-hardening steel of representative with AISI9310 the earliest, and normal temperature uses down after the low-temperaturetempering, have the conventional use properties that requires, but corrosion resisting property is relatively poor, and use temperature is lower.Fa Zhan Pinion Steel M50NiL subsequently, its principal character is that heat resistance improves.This steel adopts secondary hardening mechanism design mix, and high tempering more than 500 ℃ can stablize use below 350 ℃, but corrosion resisting property is relatively poor.

The corrosion-resisting steel that uses mainly is high carbon martensite stainless bearing steel 9Cr18 (AISI440), 9Cr18Mo (440C) at present, and such steel has high carbon, chromium content, produces thick eutectic carbides when solidifying, and can not change by later thermal treatment.Thick carbide easily causes high stress concentration to cause and peels off, and the chromium content that reduces martensitic matrix causes after the thermal treatment that hardness is on the low side, solidity to corrosion descends, and reduces work-ing life.

Along with gear train assembly high speed, high hertz stress, heatproof, understanding anti-corrosion and loss of weight demand, particularly gear capacity and heart portion yield strength mutual relationship are caused developing rapidly of superstrength gear, bearing steel.Present existing steel grade can't satisfy the requirement of transmission system to gear of new generation.The high strength stainless gear steel of our development adopts secondary hardening mechanism design mix now, adds multiple strong carbide forming element, helps obtaining surperficial ultrahigh hardness; Add a large amount Co refinement M ₂The X phase, the M of precipitation small and dispersed on the low carbon martensite matrix ₂X mutual-assistance core has superstrength and high tenacity coupling, the superstrength that can get both under suitable temperature tempering (Rm 〉=1800MPa, Rp0.2 〉=1400MPa) and high tenacity.Under hardness is condition about HRC50, its K _ICValue can reach 110Mpa.m ^1/2More than.Finally surperficial room temperature hardness can reach HRC more than 65 after carburizing thermal treatment, and its etch resistant properties is very good.Therefore this novel material of development can satisfy transmission system all requirements to gear steel of new generation now.

The representative grade of steel AISI9310 of present domestic use Pinion Steel, M50NiL, 9Cr18Mo (440C) etc., wherein stainless gear steel 9Cr18Mo (440C) can not reach the good combination of high-strength, high-ductility, anti-corrosion, heatproof simultaneously.Chemical ingredients external and the new invention high strength stainless gear steel sees Table 1.

Table 1

The patent No.	C	Mn	Si	Cr	Ni	Mo+1/2 W	Co	Mo	V	W	Nb
												US 5288347 A	0.16 0.25	≤ 1.0	≤ 2.0	11.00 15.00	≤ 2.0		12.0 21.0	0.5 3.0
JP 5247593 A	0.16 0.25	≤ 2.0	≤ 2.0	10.00 15.00	≤ 2.0	0.5 3.0	12.0 21.0		0.1 0.5		＜ 0.1
												US 5, 424,028	0.10 0.25	≤ 1.0	≤ 1.0	13.00 19.00	1.75 5.25		5.0 14.0	3.0 5.0	0.25 1.25		0.01 0.10
New invention GBC-1	0.10 0.20	≤ 0.50	≤ 0.50	12.5 15.0	1.50 3.00		12.5 14.5	4.00 6.50	0.50 0.85	0.20 1.50	≤ 0.20

Introduce according to patent US 5288347 A,,,, 120～450 ℃ of scope tempering, can obtain high strength, high tenacity and corrosion resistance then-50～-100 ℃ of sub-zero treatments through 950～1150 ℃ of solid solutions by this patent composition control.Intensity can reach Rm 〉=1714MPa, fracture toughness property K _ICReach 77.47Mpa.m1/2.

Introduce according to patent JP 5247593 A,,, be cooled to rapidly 120～475 ℃ of scope tempering, can obtain high strength, high tenacity and corrosion resistance then below-50 ℃ through 1000～1150 ℃ of solid solutions by this patent composition control.

Introduce according to patent US 5,424,028,,, be cooled to below-79 ℃,, and be cooled to-196 ℃,, can obtain high rigidity, high strength, high tenacity through three such tempering then 496 ℃ of tempering through 1050 ℃ of solid solutions by this patent composition control.

See from table 1, neoteric high strength stainless gear steel GBC-1 is different with the composition of above-mentioned three kinds of steel.In the patent US 5288347A composition of the U.S., do not add W, Nb, V; Added W, Nb, V in the patent JP 5247593A composition of Japan, but different with the span of control of new invention steel; In patent US 5,424,028 composition of the U.S., do not add W, the span of control of other composition is all more approaching.U.S. US 5,424 in addition, and the heat treating regime of introducing in 028 this patent is the same substantially with neoteric GBC-1 Heat Treatment Of Steel system, and table 2 is exactly U.S. US 5,424,028 patent and new invention patent performance comparing result.

Table 2

From table 2, new invention steel and U.S. US 5,424,028 patent steel are compared not only intensity height, and toughness index K _ICAlso high, Here it is, and we invent the purpose of this steel, promptly will pass through effectively control chemical ingredients, and handle through best heat treating regime, make the good combination of steel acquisition high strength and high tenacity.

Summary of the invention

The purpose of this invention is to provide a kind of high strength stainless gear steel and preparation method thereof, make this stainless gear steel possess high strength, high rigidity, high tenacity, erosion resistance simultaneously.

The present invention realizes that the technical scheme of above-mentioned purpose is: a kind of high strength stainless gear steel, the chemical element that comprises following weight percent proportioning: C:0.10～0.20%, Mn :≤0.50%, Si≤0.50%, Cr:12.5～15.0%, Ni:1.50～3.00%, Mo:4.00～6.50%, V:0.50～0.85%, Co:12.5～14.5%, W:0.20～1.50%, Nb :≤0.20%, all the other are Fe and unavoidable impurities.

The present invention adopts secondary hardening mechanism design mix, by adding the C-Cr-Co-Ni-Mo-V-W element, and through suitable temperature tempering, precipitation is separated out second phase tiny, disperse on martensitic matrix, makes steel obtain the good combination of high strength, high rigidity and high tenacity.

The Cr element that adds a large amount in the steel not only can improve the corrosion resisting property of steel, also improves the high temperature resistant use properties of steel simultaneously.Add the W element in the steel, can strengthen sosoloid on the one hand, on the other hand, produce dispersion-strengthened.Be steel when timeliness, precipitation is separated out tiny solid matter cube M2X phase on martensitic matrix, has increased the secondary hardening effect, and the intensity, hardness of steel are improved.

Effect and the W of Mo are similar.Add a large amount Co in the steel, the adding of Co has reduced the solubleness of Mo in matrix, has promoted to contain the precipitation of compound between Special Metal of Mo.Because the M2X of Mo alloying has high stability mutually, has slowed down by M ₂₃C ₆Carbide replaces process, has improved the temper resistance of steel, makes steel when 500 ℃ of tempering, still keeps above high strength of 1800MPa and the high rigidity of HRC50.

The adding of Ni promotes the martensitic transformation of steel, follows this effect, and the mechanical property of steel is improved.Ni and Co fit applications can effectively improve the toughness of steel in this steel in addition.AFC277 steel (C0.15, Ni 0, Co 13.5, Cr 14.5, Mo 5.0) does not contain Ni, and other composition and this steel are similar, and the impact value of AFC277 steel has only the Akv5 joule, and this steel grade can reach more than the Akv60 joule.

Strong carbide forming element V, Nb etc. have also been added in addition in the GBC-1 steel, their adding, though unable to get up is strengthened the effect of sosoloid, but they have improved the ability that forms the MC carbide, help forming tiny even and very stable (V, Nb) C double carbide through carburizing treatment, thereby obtain the top layer ultrahigh hardness.W, Mo, V, Nb have the effect of crystal grain thinning, raising intensity, add the effect of Co, Ni, Mo, make the core of steel have superstrength and high tenacity.

The manufacture method of described high strength stainless gear steel comprises following steps:

(1) metal charge of selecting low impurity content for use is as starting material, and metal Ni, Mo, Co, Cr, V, Nb etc. use low S, P as far as possible, and pure iron, mother alloy etc. are from materials, and is must cleaning dry, no greasy dirt, and rustless, composition is accurate;

(2) smelting technology: adopt two vacuum technologies to smelt i.e. vacuum induction+vacuum consumable remelting.When vacuum induction was smelted, vacuum tightness reached the following fashion material of 2.7Pa, the order charging of charging order: pure iron-Ni, Mo, Cr, Co, V-pure iron.When filling with substance is reserved small amount of N i, Mo, Cr, Co, V.Furnishing is got the finished product sample after dividing Ni, Mo, Cr, Co, V fine melt fully to stir after the fine melt composition analysis.Refining period, temperature was controlled at 1570 ℃～1590 ℃, refining time 〉=45 minute, and pouring temperature is controlled at 1540 ℃～1560 ℃.Leak rate≤0.4PaL/S during the vacuum consumable remelting, hydraulic pressure 〉=0.25MPa, the short arc melting is adopted in water temperature difference≤10 ℃, and control voltage is stable, and weldering was finished 20 minutes, and refining was finished 45 minutes, took off the ingot air cooling.Air cooling 10～12h after annealing after the steel ingot demoulding;

(3) forging process: the steel ingot Heating temperature is at 1180 ℃～1220 ℃, stops forging temperature 〉=800 ℃, carries out 670 ℃～700 ℃ annealing after the forging;

(4) rolling technology: Heating temperature is 1100 ℃～1150 ℃ when rolling, rolls back 760 ℃～810 ℃ annealing;

(5) thermal treatment process: 1000 ℃～1150 ℃ solid solutions and be lower than-80 ℃ of sub-zero treatments, again through 500 ℃～530 ℃ timeliness be lower than-80 ℃ of sub-zero treatments.

Preferably, in the described step (3), steel ingot adopts two rammers two to pull out technology when forging.

The present invention compared with prior art has following beneficial effect:

1. this steel is under solid solution condition, and intensity and hardness are all lower, about HRC36.The purpose of solid solution mainly is that alloying element is dissolved in the middle of the matrix, carries out tissue for next step ageing treatment and prepares.

2. this steel is through 1000 ℃～1150 ℃ solid solutions be lower than-80 ℃ of sub-zero treatments, again through 500 ℃～530 ℃ timeliness be lower than-80 ℃ of sub-zero treatments, intensity can reach more than the 1800MPa, yield strength reaches more than the 1400MPa, hardness can reach more than the HRC50, elongation reaches more than 18%, and ballistic work reaches more than the 100J, fracture toughness property value K _ICReach 100MPam ^1/2

3. according to the requirement of material use properties, ceiling temperature solid solution (about 1100 ℃) and be lower than-80 ℃ of sub-zero treatments during this steel adopts, again through 500 ℃～530 ℃ timeliness be lower than-80 ℃ of sub-zero treatments, when the proof strength index reaches 1800MPa, ballistic work (Aku) can reach more than the 100J, fracture toughness property value K _ICReach 110MPam ^1/2More than.

4. this steel adopts lower limit temperature solid solution (about 1050 ℃) and is lower than-80 ℃ of sub-zero treatments, again through 500 ℃～530 ℃ timeliness be lower than-80 ℃ of sub-zero treatments, intensity can reach 1900MPa, ballistic work (Aku) more than 80J, fracture toughness property value K _ICAt 90MPam ^1/2More than.

5. this steel can satisfy the requirement of Pinion Steel of new generation fully in the every performance index after certain thermal treatment, reaches high strength, high rigidity, high tenacity, corrosion resistant good combination.

Description of drawings

Fig. 1 is 1 ton of vacuum induction furnace smelting powertrace synoptic diagram.

Fig. 2 is a Φ 360mm consumable remelting processing curve synoptic diagram.

Fig. 3 is a Φ 360mm steel ingot annealing process curve synoptic diagram.

Fig. 4 is a steel ingot heating process curve synoptic diagram.

Fig. 5 forges material or blank anneal process curve synoptic diagram.

Embodiment

Embodiment

At one ton of vacuum induction furnace smelting cast ∮ 290mm electrode, vacuum consumable remelting Φ 360 steel ingot after annealings forge 90*100mm blank after annealing behind the jumping-up, rolling for steel rolling.

1, vacuum induction furnace technology

1.1, chemical component weight per-cent span of control sees Table 3:

Table 3 (%)

Element	C	Mn	Si	P	S	Cr	Ni	Mo	V	Co	W	Nb
													Standard	0.10 0.20	≤ 0.50	≤ 0.50	≤ 0.008	≤ 0.005	12.5 15.0	1.50 3.00	4.00 6.50	0.50 0.85	12.5 14.5	0.20 1.50	≤ 0.20
Span of control	0.11 0.15	≤ 0.10	≤ 0.10	≤ 0.008	≤ 0.004	13.5 14.8	1.80 2.80	4.30 5.80	0.60 0.75	12.0 14.0	0.45 1.10	0.02 0.05

1.2, processing requirement:

(1) vacuum tightness≤2.7Pa begins charging;

(2) the order charging of charging order: pure iron-Ni, Mo, Cr, Co, V-pure iron.When filling with substance is reserved small amount of N i, Mo, Cr, Co, V, and furnishing is got the finished product sample after dividing Ni, Mo, Cr, Co, V fine melt fully to stir after the fine melt composition analysis;

(3) temperature control in refining period is 1570--1590 ℃, and the hold-time was greater than 45 minutes;

(4) cast Φ 290 electrodes, teeming temperature 1540--1560 ℃;

(5) air cooling after the electrode demoulding.Smelting technology curve: see Fig. 1.

2, smelting technology-consumable remelting processing

2.1, crystallizer Φ 360mm;

2.2, adopt this steel grade heelpiece, car bits, dummy electrode are with this steel grade or approximate steel grade;

2.3, leak rate≤4.0Pa L/S;

2.4, arc length: the short arc melting, control voltage is stable;

2.5, hydraulic pressure: 〉=0.25MPa, the temperature difference≤10 ℃;

2.6, cooling: weldering was finished 20 minutes, and refining was finished 45 minutes, took off the ingot air cooling.Process curve is seen Fig. 2;

2.7, steel ingot demoulding after heat send annealing, annealing process curve is seen Fig. 3.

3, forging process

3.1, the steel ingot heating curve sees Fig. 4;

Steel ingot jumping-up 2～3 times, fiery again temperature 1160-1180 ℃, insulation 1h.Stop forging temperature 〉=800 ℃, forge that the back is red send annealing.Steel billet or forging material are forged back air cooling 10～12h after annealing;

3.2, steel billet or forge the material annealing process curve and see Fig. 5;

3.3, finished product polishing (or car light), flaw detection.

4, steel rolling process

4.1, heating process

The cooling of Heating temperature final forging temperature heat-up time

1100～1150 ℃ 〉=1: 25 〉=850 ℃ air coolings

4.2, the same Fig. 5 of stocking annealing process curve.

5, assay

5.1, the relation of different chemical composition and performance

The difference of new invention steel and other similar steel grade mainly is to have increased element W, below main contrast add W and do not add W Effect on Performance.Comparing result sees Table 4 and table 5.

Table 4 (%)

The patent No.	C	Mn	Si	Cr	Ni	Co	Mo	V	W	Nb
											US 5,424, 028	0.12			14.00	2.00	12.50	4.75	0.60		0.02
Test material 1	0.12	≤ 0.10	≤ 0.10	13.92	2.14	12.52	4.74	0.58		0.02
											Test material 2	0.12	≤ 0.10	≤ 0.10	14.10	2.00	12.48	4.74	0.60	0.45	0.02
Test material 3	0.13	≤ 0.10	≤ 0.10	13.80	2.10	12.68	4.72	0.57	1.10	0.04
											GBC-1 of the present invention	0.10 0.20	≤ 0.50	≤ 0.50	12.5 15.0	1.50 3.00	12.5 14.5	4.00 6.50	0.50 0.85	0.20 1.50	≤ 0.20

Table 5

From table 5, behind the adding W element, intensity and fracture toughness property index K _ICObviously improve, when W content reaches 1.1% in the steel, K _ICReached 108Mpa.m ^1/2

Table 6 is compositions of 7 embodiment;

Table 7 is compositions of 1 Comparative Examples;

Table 8 is that embodiment 1～7 adopts the different resulting rod mechanical performances of thermal treatment process (16 embodiment).

Table 6 (wt%)

Embodiment	C	Mn	Si	Cr	Ni	Co	Mo	V	W	Nb
											1	0.12	0.05	0.05	13.92	2.14	12.52	4.74	0.58		0.02
2	0.12	0.05	0.05	14.10	2.00	12.48	4.74	0.60	0.45	0.02
											3	0.13	0.05	0.05	13.80	2.10	12.68	4.72	0.57	1.10	0.04
4	0.11	0.04	0.05	13.90	1.90	12.50	5.00	0.60	1.10	0.04
											5	0.11	0.04	0.05	13.90	2.00	12.50	4.80	0.60		0.04
6	0.12	0.05	0.05	14.00	2.00	12.50	4.90	0.60		0.02
											7	0.12	0.05	0.05	14.20	1.80	12.00	4.80	0.60	0.50	0.02
New invention GBC-1	0.10 0.20	≤ 0.50	≤ 0.50	12.5 15.0	1.50 3.00	12.5 14.5	4.00 6.50	0.50 0.85	0.20 1.50	≤ 0.20

Table 7 (wt%)

The patent No.	C	Mn	Si	Cr	Ni	Co	Mo	V	W	Nb
											US 5,424,028	0.12			14.00	2.00	12.50	4.75	0.60		0.02

Table 8

Claims (3)

1. a high strength stainless gear steel is characterized in that, comprises the chemical element of following weight percent proportioning: C:0.10～0.20%, Mn :≤0.50%, Si≤0.50%, Cr:12.5～15.0%, Ni:1.50～3.00%, Mo:4.00～6.50%, V:0.50～0.85%, Co:12.5～14.5%, W:0.20～1.50%, Nb :≤0.20%, all the other are Fe and unavoidable impurities.

2. the manufacture method of a high strength stainless gear steel as claimed in claim 1 is characterized in that comprising following steps:

(1) select for use the metal charge of low impurity content as starting material;

(2) smelting technology: adopt vacuum induction and vacuum consumable remelting processing, when vacuum induction was smelted, vacuum tightness reached the following fashion material of 2.7Pa, and refining period, temperature was controlled at 1570 ℃～1590 ℃, refining time 〉=45 minute, pouring temperature is controlled at 1540 ℃～1560 ℃; Leak rate≤0.4PaL/S during the vacuum consumable remelting, hydraulic pressure 〉=0.25MPa, the short arc melting is adopted in water temperature difference≤10 ℃, and control voltage is stable;

(3) forging process: the steel ingot Heating temperature is carried out 670 ℃～700 ℃ annealing at 1160 ℃～1220 ℃ after the forging;

(4) rolling technology: Heating temperature is 1100 ℃～1150 ℃ when rolling, rolls back 760 ℃～810 ℃ annealing;

(5) thermal treatment process: adopt 1000 ℃～1150 ℃ solid solutions and be lower than-80 ℃ of cryogenic treatment process, again through 500 ℃～530 ℃ timeliness be lower than-80 ℃ of cryogenic treatment process.

3. the manufacture method of high strength stainless gear steel as claimed in claim 2 is characterized in that in the described step (3), and two rammers two were pulled out when steel ingot forged.

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