CN104775075A - SAE8620H gear steel and production method thereof - Google Patents

Abstract

The invention relates to SAE8620H gear steel. The SAE8620H gear steel comprises the following components in percentage by weight: 0.18-0.23% of C, 0.15-0.35% of Si, 0.70-0.90% of Mn, less than or equal to 0.030% of S, less than or equal to 0.030% of P, 0.40-0.65% of Cr, 0.40-0.70% of Ni, 0.15-0.25% of Mo, 0.025-0.050% of Al, less than or equal to 0.20% of Cu and the balance of Fe, wherein the amount of Fe is equal to an extra amount except the amount of main components and residual components; and the SAE8620H gear steel also comprises the following gas components in steel in percentage by weight (Wt%): less than or equal to 20*10<-6> of O, less than or equal to 2*10<-6> of H and less than or equal to 70*10<-6> of N. The SAE8620H gear steel disclosed by the invention has the following effects: firstly, the production cost can be effectively reduced; secondly, uniform components can be ensured, and a stability guarantee of end hardenability can be provided; thirdly, high cleanability of molten steel can be ensured; and fourthly, only a casting blank slow cooling process is adopted, and rolled round steel is not subjected to a slow cooling process, so that the production efficiency can be greatly improved, and the cost of production procedures can also be effectively reduced.

Description

A kind of SAE8620H Pinion Steel and manufacture method thereof

Technical field

The invention belongs to metallurgical technology field, relate to a kind of transmitting gear mainly for the manufacture of various heavy-duty car, heavy digger, slingcart, heavy machine tool and other heavy-duty machinery, gear shaft, and higher SAE8620H Pinion Steel and manufacture method thereof are required to hardening capacity.

Background technology

SAE8620H steel is the steel grade introduced from U.S. AISI (SAE) standard, is widely used in the Cr-Ni-Mo system case-hardening steel of carburizing and carbonitriding.In steel, Cr, Ni, Mo content is lower, has good forging property, machinability and welding property, and part from carburizing temperature direct quenching, can form carbide tendency less in cementation process.SAE8620H steel is mainly for the manufacture of transmitting gear, the gear shaft of various heavy-duty car, heavy digger, slingcart, heavy machine tool and other heavy-duty machinery, also miniature gear and the gear shaft of transmission large torque is needed for the manufacture of cross-country jeep, cross country motorcycle etc., require good obdurability, wear resistance, withstand shocks, bending and contact stress, and also to be out of shape little, precision is high, noise is low.For the manufacture of gear, because its machining deformation amount is little, hardenability band is narrow and stable, be one of very strict Pinion Steel kind of specification of quality.

Publication number CN201010603965.1, the patent of invention of by name " a kind of CrNiMo system free-cutting pinion steel and manufacture method thereof ", the good cutting ability mainly solving that following process has, H band are narrow.But this patented invention content is for adding S steel, situation is controlled to non-metallic inclusion and does not explain, and after rolling, adopting slow cooling operation, increasing process cost.

" 150t converter+LF+RH short route produces the mass analysis of Pinion Steel SAE8620H " by name document, adopt short route operation to produce Pinion Steel SAE8620H, its chemical composition adopts arrowband to control, and averaged Oxygen content controls at 16 × lO ^-6, refining controlling (FeO+MnO) %<1%, continuous casting adopts induction stirring etc., and property indices all reaches high-quality steel level.But in document actual constituent proportioning, Mn, Cr, Ni, Mo content controls higher, the middle upper limit of standard control all partially, wherein the working control of Mn content is at 0.85-0.95%, the working control of Cr content is at 0.58-0.65%, the working control of Ni content in the working control of 0.55-0.65%, Mo content at 0.16-0.24%.Ni, Mo mischmetal cost intensive, causes production cost higher.

" production domesticization of SAE8620H steel and the research of applying " by name, " exploitation of SAE8620 H Automobile Gear Steels ", " the production domesticization research of SAE8620H Pinion Steel ", " high quality Pinion Steel SAE8620H (Z) novel process for refining is put into practice ", " development of American Standard SAE8620H Pinion Steel ", documents such as " developments of heavy-load automobile Pinion Steel 8620H ", manufacture SAE8620H Pinion Steel, all adopt traditional electric furnace smelting method, because electric furnace production efficiency is low, cost is high, electric furnace is power consumption rich and influential family, the bad place of electric power resource is difficult to get the Green Light, converter smelting is utilized to be one of trend of development.

In sum, produce the steel mill of SAE8620H Pinion Steel at present, mostly adopt traditional electrosmelting, energy consumption cost is higher; The method adding S can be adopted to realize to improve machinability or then realized by the content of raising expensive metal Ni, Mo to improve the performance index such as SAE8620H hardening capacity, and taking to roll rear retarded cooling process.In the depressed situation in current steel market, these manufacture method or technique can add manufacturing cost undoubtedly, thus the development of restriction iron and steel enterprise.

Summary of the invention

For overcoming above-mentioned technical disadvantages, the invention provides a kind of SAE8620H Pinion Steel and production method thereof, it has stable performance, work-ing life extends, and the feature such as production cost is lower.

The present invention solves the technological method that its technical problem adopts: a kind ofsAE8620H Pinion Steel, its component and weight percent are: C:0.18%-0.23%, Si:0.15%-0.35%, Mn:0.70-0.90%, S≤0.030%, P≤0.030%, Cr:0.40%-0.65%, Ni:0.40%-0.70%, Mo:0.15%-0.25%, Al:0.025%-0.050%, Cu≤0.20%, Fe: be the surplus outside above-mentioned principal constituent and following residual components; It also comprises gaseous constituent in the steel of following weight percent (Wt%): O≤20 × 10 ^-6, H≤2 × 10 ^-6, N≤70 × 10 ^-6.

The manufacture method of above-mentioned SAE8620H Pinion Steel, the steps include:

The first step: converter smelting, guarantee that molten iron enters stove S≤0.020%, ladle uses last stove for crossing LF process and not having to produce the steel grade containing Ti or B, strict control terminal C >=0.06%, adopts slide plate pushing off the slag, stops tapping process slag, terminal P is controlled≤0.015%, target P controls≤0.012%, and tapping process alloy adds and can adjust according to practical situation, and actual add-on meets LF Composition Control area requirement with molten steel composition and is as the criterion;

Second step: LF refining, requirement is arrived at a station temperature >=1539 DEG C, guarantee that the good and slag look of slag fluidity bleaches, process divide on a small quantity many batches add reductor and safeguard refining slag, bottom blowing Ar atmospheric pressure controls not rout up the top of the slag for principle with molten steel, refining time >=55min, out-station temperature is opened and is watered stove span of control 1639 ± 5 DEG C, and even watering stove span of control is 1634 ± 5 DEG C;

3rd step: RH vacuum outgas is smelted, Fruit storage is carried out to molten steel, under 0.266KPa vacuum tightness treatment time >=18min, pure degassing time >=8min, calcium iron wire is fed after vacuum breaker, namely calcium iron wire 300 meters (open water stove feed quantity increase by 150 meters) is fed before soft blow calmness, connect and water soft argon blowing time >=15 minute of stove, open and water soft argon blowing time >=20 minute of stove, soft blow controls not blow break face and the top of the slag slightly fluctuates and is as the criterion, guarantee that the large-sized inclusions floating in steel is got rid of, in soft blow process, forbid molten steel exposed;

4th step: continuous casting, Prepared by Low Superheat Pouring: open and water stove≤40 DEG C, connects and waters stove≤35 DEG C, to increase the thin equiax crystal district of strand, reduces component segregation; Omnidistance anaerobic molding casting, large bag to tundish adopts long nozzle to add the cast of Ar gas shielded, adopt submerged nozzle molding casting simultaneously, large bag long nozzle depth of penetration >=200mm, middle water-coating port depth of penetration 120 ± 20mm, middle bag adds insulating covering agent, crystallizer adds the measures such as covering slag and prevents molten steel secondary oxidation; Guarantee that pulling rate is stable, middle bag level stability in most significant digit, ensure the stable of mold liquid level, stop artificial disturbance mold liquid level; Adopt M-EMS, the growth of fragmentation or suppression column crystal, form proportion of equiaxed grain higher, the generation of the composition of even remaining liquid phase and temperature, suppression " bridging " phenomenon, after continuously cast bloom has cut by predetermined length, steel billet is hung in burial pit and carry out slow cooling, slow cooling time >=48h, or Hong Song Steel Mill carries out heating rolling;

5th step: heating rolling, strand after slow cooling process or the red steel billet that send are heated, Heating temperature is 1160-1200 DEG C, heat-up time >=288 minutes, strand adopts high-pressure water descaling after coming out of the stove, ensure the Ex-all of iron oxide on surface of billet steel skin, roughing start rolling temperature 1120-1160 DEG C, finishing temperature 850-940 DEG C;

6th step: finishing, after being rolled into round steel, online hot saw scale, serves cold bed naturally cooling, packaging and warehousing after finishing, completes the manufacturing of SAE8620H Pinion Steel.

The invention has the beneficial effects as follows: one is that the alloying elements cr in steel, Ni, Mo content all control at standard min by the present invention, effectively reduces production cost; Two is that the present invention passes through to smelt composition arrowbandization and controls, and low overheat, end induction stirring, stablize the segregation of the continuous casting process minimizing chemical elements such as pulling rate, guarantees uniform composition, provides guarantee to the stability of H; Three is present invention employs the long nozzle wrapped greatly to tundish to add the cast of Ar gas shielded, submerged nozzle, the measures such as middle covering agent, crystallizer protecting residue carry out whole process protection cast to molten steel, prevent molten steel secondary oxidation, reduce non-metallic inclusion, ensure the Cleaning ability of molten steel; Four is that the present invention only takes strand slow cooling, and milling round steel, without slow cooling operation, is greatly enhanced productivity, and effectively reduces production process cost simultaneously.

Embodiment

Below in conjunction with embodiment, the present invention is further described.

a kind ofsAE8620H Pinion Steel, its component and weight percent are: C:0.18%-0.23%, Si:0.15%-0.35%, Mn:0.70-0.90%, S≤0.030%, P≤0.030%, Cr:0.40%-0.65%, Ni:0.40%-0.70%, Mo:0.15%-0.25%, Al:0.025%-0.050%, Cu≤0.20%, Fe: be the surplus outside above-mentioned principal constituent and following residual components; It also comprises gaseous constituent in the steel of following weight percent (Wt%): O≤20 × 10 ^-6, H≤2 × 10 ^-6, N≤70 × 10 ^-6.

The manufacture method of above-mentioned SAE8620H Pinion Steel, the steps include:

The first step: converter smelting, guarantee that molten iron enters stove S≤0.020%, ladle uses last stove for crossing LF process and not having to produce the steel grade containing Ti or B, strict control terminal C >=0.06%, adopts slide plate pushing off the slag, stops tapping process slag, terminal P is controlled≤0.015%, target P controls≤0.012%, and tapping process alloy adds and can adjust according to practical situation, and actual add-on meets LF Composition Control area requirement with molten steel composition and is as the criterion;

Second step: LF refining, requirement is arrived at a station temperature >=1539 DEG C, guarantee that the good and slag look of slag fluidity bleaches, process divide on a small quantity many batches add reductor and safeguard refining slag, bottom blowing Ar atmospheric pressure controls not rout up the top of the slag for principle with molten steel, refining time >=55min, out-station temperature is opened and is watered stove span of control 1639 ± 5 DEG C, and even watering stove span of control is 1634 ± 5 DEG C;

3rd step: RH vacuum outgas is smelted, Fruit storage is carried out to molten steel, under 0.266KPa vacuum tightness treatment time >=18min, pure degassing time >=8min, calcium iron wire is fed after vacuum breaker, namely calcium iron wire 300 meters (open water stove feed quantity increase by 150 meters) is fed before soft blow calmness, connect and water soft argon blowing time >=15 minute of stove, open and water soft argon blowing time >=20 minute of stove, soft blow controls not blow break face and the top of the slag slightly fluctuates and is as the criterion, guarantee that the large-sized inclusions floating in steel is got rid of, in soft blow process, forbid molten steel exposed;

4th step: continuous casting, Prepared by Low Superheat Pouring: open and water stove≤40 DEG C, connects and waters stove≤35 DEG C, to increase the thin equiax crystal district of strand, reduces component segregation; Omnidistance anaerobic molding casting, large bag to tundish adopts long nozzle to add the cast of Ar gas shielded, adopt submerged nozzle molding casting simultaneously, large bag long nozzle depth of penetration >=200mm, middle water-coating port depth of penetration 120 ± 20mm, middle bag adds insulating covering agent, crystallizer adds the measures such as covering slag and prevents molten steel secondary oxidation; Guarantee that pulling rate is stable, middle bag level stability in most significant digit, ensure the stable of mold liquid level, stop artificial disturbance mold liquid level; Adopt M-EMS, the growth of fragmentation or suppression column crystal, form proportion of equiaxed grain higher, the generation of the composition of even remaining liquid phase and temperature, suppression " bridging " phenomenon, after continuously cast bloom has cut by predetermined length, steel billet is hung in burial pit and carry out slow cooling, slow cooling time >=48h, or Hong Song Steel Mill carries out heating rolling;

5th step: heating rolling, strand after slow cooling process or the red steel billet that send are heated, Heating temperature is 1160-1200 DEG C, heat-up time >=288 minutes, strand adopts high-pressure water descaling after coming out of the stove, ensure the Ex-all of iron oxide on surface of billet steel skin, roughing start rolling temperature 1120-1160 DEG C, finishing temperature 850-940 DEG C;

6th step: finishing, after being rolled into round steel, online hot saw scale, serves cold bed naturally cooling, packaging and warehousing after finishing, completes the manufacturing of SAE8620H Pinion Steel.

Embodiment 1 is within the scope of Chemical Composition of the present invention, and determine that embodiment 1,2 Chemical Composition (Wt%) is as shown in table 1, wherein all control Fe is 97.5-98.0, O≤20 × 10 ^-6, H≤2 × 10 ^-6, N≤70 × 10 ^-6.The smelting of embodiment 1,2 and the operation of rolling control as shown in table 2, and obtained SAE8620H Pinion Steel finished product high-low time tissue and H performance are respectively as shown in table 3, table 4.

Comparative example 1 in table 1, table 2, table 3, table 4 is the chemical composition of the SAE8620H of document " 150t converter+LF+RH short route produces the mass analysis of Pinion Steel SAE8620H ", production process and quality product situation; Comparative example 2 is the chemical composition of the SAE8620H of the document production domesticization of the SAE8620H Pinion Steel " research ", production process and quality product situation.

Table 1 SAE8620H Pinion Steel chemical composition (Wt, %)

Sequence number	C	Si	Mn	P	S	Cr	Ni	Mo	Cu	O/ppm	N/ppm	H/ppm
													Embodiment 1	0.19	0.25	0.74	0.016	0.002	0.45	0.45	0.16	0.08	12	54	0.5
Embodiment 2	0.18	0.25	0.74	0.017	0.003	0.45	0.46	0.17	0.05	17	62	0.1
													Contrast 1	0.22	0.21	0.89			0.61	0.58	0.20
Contrast 2	0.18	0.24	0.79	0.017	0.010	0.60	0.51	0.22	0.09

Roll control smelted by table 2 SAE8620H Pinion Steel

Table 3 SAE8620H Pinion Steel high-low time tissue

Table 4 SAE8620H Pinion Steel H

Sequence number	J6mm (HRC)	J9mm(HRC)
			Embodiment 1	37.7	29.9
Embodiment 2	36.5	27.9
			Contrast 1	39	23.0
Contrast 2	37.5	30.5

Controlled by the actual constituent of table 1-table 4, production process controls and product structure property situation shows, the cleanliness factor of the SAE8620H Pinion Steel round steel that the present invention produces is high, high-low time tissue, H index are good, quality product is good, there is the advantage that production cost is low simultaneously, the present invention simultaneously has following several advantage: one is that the alloying elements cr in steel, Ni, Mo content all control at standard min by the present invention, effectively reduces production cost; Two is that the present invention passes through to smelt composition arrowbandization and controls, and low overheat, end induction stirring, stablize the segregation of the continuous casting process minimizing chemical elements such as pulling rate, guarantees uniform composition, provides guarantee to the stability of H; Three is present invention employs the long nozzle wrapped greatly to tundish to add the cast of Ar gas shielded, submerged nozzle, the measures such as middle covering agent, crystallizer protecting residue carry out whole process protection cast to molten steel, prevent molten steel secondary oxidation, reduce non-metallic inclusion, ensure the Cleaning ability of molten steel; Four is that the present invention only takes strand slow cooling, and milling round steel, without slow cooling operation, is greatly enhanced productivity, and effectively reduces production process cost simultaneously.

Claims (2)

1. a kind ofsAE8620H Pinion Steel, it is characterized in that component and weight percent are: C:0.18%-0.23%, Si:0.15%-0.35%, Mn:0.70-0.90%, S≤0.030%, P≤0.030%, Cr:0.40%-0.65%, Ni:0.40%-0.70%, Mo:0.15%-0.25%, Al:0.025%-0.050%, Cu≤0.20%, Fe: be the surplus outside above-mentioned principal constituent and following residual components; It also comprises gaseous constituent in the steel of following weight percent (Wt%): O≤20 × 10 ^-6, H≤2 × 10 ^-6, N≤70 × 10 ^-6.

2. the manufacture method of SAE8620H Pinion Steel as claimed in claim 1, is characterized in that step is:

The first step: converter smelting, guarantee that molten iron enters stove S≤0.020%, ladle uses last stove for crossing LF process and not having to produce the steel grade containing Ti or B, strict control terminal C >=0.06%, adopts slide plate pushing off the slag, stops tapping process slag, terminal P is controlled≤0.015%, target P controls≤0.012%, and tapping process alloy adds and can adjust according to practical situation, and actual add-on meets LF Composition Control area requirement with molten steel composition and is as the criterion;

Second step: LF refining, requirement is arrived at a station temperature >=1539 DEG C, guarantee that the good and slag look of slag fluidity bleaches, process divide on a small quantity many batches add reductor and safeguard refining slag, bottom blowing Ar atmospheric pressure controls not rout up the top of the slag for principle with molten steel, refining time >=55min, out-station temperature is opened and is watered stove span of control 1639 ± 5 DEG C, and even watering stove span of control is 1634 ± 5 DEG C;

3rd step: RH vacuum outgas is smelted, Fruit storage is carried out to molten steel, under 0.266KPa vacuum tightness treatment time >=18min, pure degassing time >=8min, calcium iron wire is fed after vacuum breaker, namely calcium iron wire 300 meters (open water stove feed quantity increase by 150 meters) is fed before soft blow calmness, connect and water soft argon blowing time >=15 minute of stove, open and water soft argon blowing time >=20 minute of stove, soft blow controls not blow break face and the top of the slag slightly fluctuates and is as the criterion, guarantee that the large-sized inclusions floating in steel is got rid of, in soft blow process, forbid molten steel exposed;

4th step: continuous casting, Prepared by Low Superheat Pouring: open and water stove≤40 DEG C, connects and waters stove≤35 DEG C, to increase the thin equiax crystal district of strand, reduces component segregation; Omnidistance anaerobic molding casting, large bag to tundish adopts long nozzle to add the cast of Ar gas shielded, adopt submerged nozzle molding casting simultaneously, large bag long nozzle depth of penetration >=200mm, middle water-coating port depth of penetration 120 ± 20mm, middle bag adds insulating covering agent, crystallizer adds the measures such as covering slag and prevents molten steel secondary oxidation; Guarantee that pulling rate is stable, middle bag level stability in most significant digit, ensure the stable of mold liquid level, stop artificial disturbance mold liquid level; Adopt M-EMS, the growth of fragmentation or suppression column crystal, form proportion of equiaxed grain higher, the generation of the composition of even remaining liquid phase and temperature, suppression " bridging " phenomenon, after continuously cast bloom has cut by predetermined length, steel billet is hung in burial pit and carry out slow cooling, slow cooling time >=48h, or Hong Song Steel Mill carries out heating rolling;

5th step: heating rolling, strand after slow cooling process or the red steel billet that send are heated, Heating temperature is 1160-1200 DEG C, heat-up time >=288 minutes, strand adopts high-pressure water descaling after coming out of the stove, ensure the Ex-all of iron oxide on surface of billet steel skin, roughing start rolling temperature 1120-1160 DEG C, finishing temperature 850-940 DEG C;

6th step: finishing, after being rolled into round steel, online hot saw scale, serves cold bed naturally cooling, packaging and warehousing after finishing, completes the manufacturing of SAE8620H Pinion Steel.