CN101812643B - Boracic pinion steel and preparation method thereof - Google Patents
Boracic pinion steel and preparation method thereof Download PDFInfo
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- CN101812643B CN101812643B CN2009102299977A CN200910229997A CN101812643B CN 101812643 B CN101812643 B CN 101812643B CN 2009102299977 A CN2009102299977 A CN 2009102299977A CN 200910229997 A CN200910229997 A CN 200910229997A CN 101812643 B CN101812643 B CN 101812643B
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Abstract
The invention relates to boracic pinion steel and a preparation method thereof. The boracic pinion steel comprises the following component by weight percent: 0.16 to 0.24 percent of C, less than or equal to 0.35 percent of Si, 0.70 to 1.25 percent of Mn, less than or equal to 0.030 percent of P, less than or equal to 0.03 percent of S, 0.80 to 1.45 percent of Cr, 0.020 to 0.080 percent of Ti, 0.005 to 0.003 percent of B, 0.015 to 0.05 percent of Al, less than 2.5*10-4 percent of H, 30*10-4 to 120 *10-4 percent of N, and less than or equal to 18 *10-4 percent of T.O, Fe and unavoidable foreign matters. The following process route can be adopted for the production: primary smelting furnace (electric furnace or revolving furnace) - refining furnace (LF furnace and the like) - vacuum refining furnace (VD furnace or RH furnace, etc.) - continuous casting - rolling. Compared with 20CrMnTiH and sub-steel number thereof, the boracic pinion steel has high hardenability, stability and narrow flap, improves the application performance, can satisfy the performance requirements of the heavy-load vehicles and large shaft gear components, can substitute partial pinion steel such as Cr-Ni-Mo, Cr-Mo and the like, and has low production cost.
Description
Technical field
The present invention relates to metallurgical technology field, belong to the steel alloy class, relate to a kind of boracic pinion steel and preparation method thereof.
Background technology
Pinion Steel is a large usage quantity in the automotive material, one of critical material of having relatively high expectations, and it not only influences the vehicle life-span, technico-economical comparisones such as energy consumption, and also also most important for satisfying safety, environmental protection and comfort requirement.Domestic Automotive Industry flourish not only makes Pinion Steel output be improved largely, and also increasingly high to the requirement of its quality, promoted the upgrading of automotive material.Energy-saving and environmental protection, safe, comfortable, intelligence and network are the general trends of automotive industry technical development; Automobile industry development is to practice thrift alloy (elements such as Cr, Ni, Mo) resource to the requirement of part development; This just need be from designing the most economical Pinion Steel of exploitation, can satisfy light, in, the performance requriements of heavy-duty car gear.For security and the safety that improves automobile, increasingly high requirement has been proposed all for the hardening capacity of Pinion Steel, non-metallic inclusion, oxygen level, microstructure etc.At present, the Pinion Steel of evaluation high quality level mainly shows four aspects: terminal hardenability band is narrow, plastisied dispersion little (common level 6～8HRC, advanced level 4～6HRC); The clarity height (common level total oxygen≤20ppm, the advanced level total oxygen≤15ppm); Grain fineness number tiny evenly (common level>=5 grade, advanced level>=6 grade); Good processability.
External Pinion Steel is on general carbusintering base steel plinth, to develop, and in view of the resource of various countries and the difference of the condition of production, its alloy system is inequality; Like German Mn-Cr system (part is added micro-B); Japan Cr system and Cr-Mo system, U.S. Cr-Ni-Mo system, French Cr-Ni system and Cr-Mo system.In recent years, along with the development of China's machine building industry, the especially development of automobile industry, the consumption of Pinion Steel is also growing, and is also increasingly high to the requirement of Pinion Steel.High-performance, long lifetime, economy and easy processing have become the main developing direction of current research and development new gear steel.At present; What China used in a large number is that Cr-Mn-Ti is a Pinion Steel; Cr-Mn-Ti is that Pinion Steel is compared with other serial Pinion Steel, has the advantage of aspects such as cost is low, little, the easy processing treatment of grain growth tendency, and 20CrMnTiH and sub-grade of steel thereof are that it represents steel grade; Dominate in China's gear industry accounts for about 60% of China's Pinion Steel total amount.But in production and use, also exposed some problems, still not ideal enough to the control of its hardening capacity aborning, terminal hardening capacity fluctuation is bigger, and hardening capacity is on the low side, can not satisfy the performance requriements of heavy-load automobile and big profile shaft tooth class part.In addition, 20CrMnTiH and sub-grade of steel thereof are mainly controlled its passing through property value through adjustment C, Mn, Cr content, and C, Mn, Cr are middle upper limit control basically in process of production, and alloy consumes high, and production cost increases.
In the Pinion Steel, mainly being the nitride AlN prevention grain growth with aluminium abroad, is in the Pinion Steel at Cr-Mn-Ti, is carbonitride Ti (NC) the prevention grain growth with titanium.Two kinds of infusible compound particles all are box-shaped, also do not have reliable experimental can be quantitative explanation Ti (NC) particle bigger to the bending resistance fatigue property influence of gear.
Current, exploitation high-performance, economical Pinion Steel have become a main direction of Pinion Steel technical development.Cr-Ni-Mo, Cr-Mo are that alloy element resource shortage such as Cr contained in the automobile carbonized Gear Steel, Ni, Mo, price are high, and production cost is high.Mn and Cr are the alloying elements that improves the hardening capacity efficient and cost-effective; B not only improves the hardening capacity of material; And the reinforcement crystal boundary, so Mn-Cr system and Mn-Cr-B are the automobile carbonized Gear Steel can satisfy gently, in, the performance need of heavy-duty car carburized gears, generally acknowledged economical Pinion Steel; This also meets the development trend of automobile gear steel, i.e. Cr-Ni-Mo → Cr-Mo → Mn-Cr → Mn-B.Therefore, Mn-Cr system and Mn-Cr-B to be that the automobile carbonized Gear Steel should become low, in year automobile gear with the main steel grade of material.Mn-Cr is that Pinion Steel mainly is used on the gear of Santana, Audi and Jetta car at present, and the center brand also can be used for Fukang Car, IVECO Light-duty Vehicle and high-power marine gearbox etc.The main trade mark has 16MnCr5,20MnCr5,25MnCr5 and the 28MnCr5 etc. that produce by the germany volkswagen company standard.Mn-Cr-B is that the main trade mark of Pinion Steel has by germany volkswagen company standard production ZF6 (16CrMnBH) and ZF7 (20CrMnBH).Mainly be used on the gear of steyr automobile, the effect of B in this type steel mainly is to form spherical BN, reduces solid solution N amount in the steel, improves the toughness of steel.
Patent CN101096742 has developed a kind of automobile high-strength Pinion Steel, and its composition quality per-cent is: C:0.20-0.40, Si:0.20-0.50; Mn:0.50-1.00, Cr:0.80-1.30, Nb:0.015-0.080; V:0.030-0.090; Mo:0.15-0.55, Al:0.015-0.050 surplusly is Fe and inevitable impurity.The present invention mainly through adding Nb, the V element of trace, improves grain fineness number, hardening capacity and the bandwidth of Pinion Steel, the comprehensive mechanical property of increase Pinion Steel, improves work-ing life, reduces production costs.
Patent CN101319294A has developed a kind of fine grain carburizing gear steel and preparation method thereof, and its composition (weight %) is: C 0.15-0.25%, Si≤0.35%, Mn 0.60-0.90%; Cr 0.80-1.20%, P≤0.015%, S≤0.010%; Nb0.02-0.08%, B 0.005-0.0035%, Mo 0.15-0.35%; Al0.02-0.06%, Ti0.01-0.04% surplusly is Fe and inevitable impurity.The present invention reaches crystal grain thinning and improves the effect of Pinion Steel thermoplasticity through interpolation Nb, B, Ti; Adopt the cold rolling Rolling Production technology that is lower than 900 ℃ to make the second phase particle that disperse distributes in the steel compare the raising of carburizing crystal grain, bending fatigue strength, the corresponding raising of contact fatigue life with existing carbonized Gear Steel 20CrMoH.
Patent CN1861830A has developed a kind of steel for heavy loading gear, and its composition (weight %) is: C 0.17%-0.25%, Si 0.05%-0.15%, Mn 0.2%-0.5%; Cr 1.4%-2.5%, P≤0.015%, S 0.002%-0.01%, Nb0.03%-0.15%; Mo 0.1%-0.8%, Al 0.015%-0.060%, Ni 1.5%-4.0%, RE 0.001%-0.05%; [O]≤0.0015%, [N] 0.005%-0.03%, surplus for Fe and inevitable impurity is also surplus has＜0.2%V.A kind of high-tensile, HI high impact merit, little, the easy heavy-load gear steel of processing of carburizing and quenching distortion have been invented; Mainly through adding Nb, Cr, Ni, Mo, V crystal grain thinning and guaranteeing enough hardening capacity; Add RE and guarantee low [O] content; Easy oxidation elements such as the fatigue strength when guaranteeing heavy duty, reduction Si, Mn are with further raising carburizing and basic toughness.
It is narrow hardening capacity Pinion Steel and working method thereof that CN101289731A has invented Cr-Mn-Ti, and its composition is: C:0.13-0.23%, Si:0.17-0.30%; Mn:0.80-1.25%, Cr:0.90-1.35%, P≤0.030%; S≤0.050%, [O]≤20 * 10
-6, [H]≤2.5 * 10
-6, Ti 0.04-0.010% surplusly is Fe and inevitable impurity.The present invention mainly controls the purpose that realizes pressing narrow hardenability band through the steel grade design and the intensifies process of narrow composition.
CN1851024A has invented a kind of heavy-load gear steel, and its composition weight percent is: C 0.14-0.20, Si≤0.12, Mn1.2-1.6; Cr 1.30-1.80, P≤0.03, S 0.015-0.04, W≤0.05; Ti 0.04-0.010, [O]≤20ppm surplusly is Fe and inevitable impurity.The present invention is not owing to add noble elements such as Ni, Mo, and thermal treatment process is simplified, and makes production cost reduce about 30%, and production efficiency improves, and can reduce problems such as heat treatment deformation, is particularly suitable for making heavy lift vehicle traction Pinion Steel.
CN101148737A has invented a kind of boron-containing steel and preparation method thereof, and its composition weight percent % is: C 0.32-0.44, Si 0.15-0.37; Mn 1.10-1.40, B 0.0005-0.0035, P≤0.030; S≤0.030, Al 0.015-0.070 surplusly is Fe and inevitable impurity.The present invention with the hardening capacity of assurance steel, makes this steel be used in important mechanical component through the micro-B element of control (behind the broken sky of VD, wrap up in adding with the aluminium suitcase after feeding Al line, Ti line in succession, the recovery is 50-70%).
It is Pinion Steel that the Pinion Steel of patent CN101096742, CN101319294A exploitation is Cr-Mo; The former realizes the raising of Pinion Steel quality, performance through Nb, V microalloying; The latter mainly crosses and adds Nb, B, Ti element and adopt specific rolling technology to improve the performance of Pinion Steel; Though both have improved the performance of Pinion Steel, be unfavorable for the reduction of cost.It is Pinion Steel that the heavy-load gear steel of patent CN1861830A exploitation belongs to Cr-Ni-Mo, through adding the effect that Nb, V and RE realize improving its performance.It is Pinion Steel that patent CN101289731A, CN1851024A exploitation Pinion Steel belong to Cr-Mn-Ti.The CN101289731A mainly design of the steel grade through narrow composition and intensifies process controls that to realize pressing narrow Cr-Mn-Ti be the purpose of Pinion Steel hardenability band, and not relating to Cr-Mn-Ti is the change of Pinion Steel composition.CN1851024A mainly improves the hardening capacity element Cr through increasing in the steel, improve the intensity of steel, improves use properties.Patent CN101148737A boron-containing steel does not belong to Pinion Steel.
In the structure iron field, hardening capacity is to carry out high-quality and institute's problem of consideration at first during the design of selection and composition economically.Say that from hardness it is measuring of steel quenching post-hardening layer depth.The mechanical property of steel, especially ys and impelling strength and hardening capacity are closely related, and are difficult to complete through hardening during heavy in section structure unit thermal treatment.Therefore, the hardening capacity problem of structure iron always causes people's great attention.
Boron is as the effective element that improves steel hardenability, and it uses the history in existing more than 60 year.During the nearly last ten years, owing to practice thrift the pressure of alloying element, reduction steel product cost.Simultaneously, the experimental technique that some are advanced and physical analysis technology is as from roentgenogramX; Electron probe microanalysis (EPMA), secondary ions emission spectrum, the development of Auger spectroscopy etc.; People are deepened continuously to what hydroboration mechanism was understood; Be accompanied by developing rapidly of steelmaking process control techniques, occurred further enlarging the preferably opportunity that boron is used in steel, boron steel has got into a new developmental stage.Improve the mechanism of action and the utilisation technology of hardening capacity about boron, so far still discuss, in the development, but relevant basic law is identified:
(1) acting to the hardening capacity of steel is solid solution boron, and the mechanism of action mainly is boron gathering partially at austenite grain boundary.
(2) micro-solid solution boron can improve the hardening capacity of steel strongly, has the boron-containing quantity of a best results, and result of study varies with each individual, but many within 0.0005%～0.0030% scope.
(3) element such as carbon and oxygen, nitrogen has material impact to the hardening capacity effect that boron improves steel.
Since the sixties in 20th century, research and the application work of Domestic Automotive Industry with regard to having carried out boracic pinion steel energetically is with 20MnVB, 20Mn
2Steel grades such as TiB replace 20CrMnTi to make the automobile carburized gears.First Auto Group, DongFeng Automobile Co., Ltd etc. once used 20MnTiB, 20Mn on " Jiefang brand " and " Dongfeng brand " 5t load-carrying vehicle variator and back axle gear
2TiB and 20MnVB steel, this is the technological innovation first time of Chinese gear industry, tries hard to set up the Pinion Steel series of China.Development along with automobile industry; Raising to the Pinion Steel accuracy requirement; The use of boron steel in the past exposes some problems, mainly is that hardening capacity is unstable, and hardenability band is wide; Influence processing, dimensional precision and the work-ing life of gear, so a lot of motor corporations just stop using boron steel to produce gear before and after 1980.This mainly contains the reason of two aspects:
(1) the above-mentioned serial gear steel capital is on the basis of single raising hardening capacity element M n, to add boron, and the hardening capacity of steel too relies on the influence of boron.
(2) smelted the equipment and the restriction of state of the art at that time, oxygen in the steel, nitrogen content are high, and the purity of steel is low, the especially effectively content of the boron precisely control of being unrealized of the content of boron in steel, content is unstable, fluctuation greatly.
Current, a kind of viewpoint thinks that with Cr-Mn-Ti be Pinion Steel series on the material behavior adjustment and the basis of improving, and replaces the external grade of steel of introducing, and sets up the alloying system that cost has more competitive power, under prior art progressive condition, is feasible.Simultaneously, paying attention to utilizing trace elements such as V, Nb, B also to become of automobile carbonized Gear Steel pursues one's goal.
Summary of the invention
The object of the invention is primarily aimed at Cr-Mn-Ti that present China accounts for the principal status of public economy be Pinion Steel (representing steel grade 20CrMnTiH and sub-grade of steel thereof) produce with use in the hardening capacity that exposes control undesirable; Terminal hardening capacity fluctuation is big, hardening capacity is on the low side; Can not satisfy problems such as heavy-load automobile and big profile shaft tooth class part performance requriements; And combination is accompanied by the raising of smelting technology level and detection technique at present; The content of boron in steel is the precisely controlled reality of content of boron especially effectively, proposes a kind of boracic pinion steel and preparation method thereof.Characteristics such as boracic pinion steel of the present invention has the hardening capacity height and stablizes, is with Pinion Steels such as narrow, alternative portion C r-Ni-Mo, Cr-Mo system, and production cost is low.
Because process step involved in the present invention is more, except that the processing condition that clearly limit, the process portion that the present invention does not specify is all by state of the art.
Technical scheme of the present invention is:
The present invention provides a kind of boracic pinion steel, and its chemical ingredients mass percent is: C:0.16%～0.24%, Si≤0.35%; Mn:0.70%～1.25%, P≤0.030%, S≤0.030%; Cr:0.80%～1.45%, Ti:0.020%～0.080%, B:0.0005%～0.0030%; Al:0.015%～0.050%, H≤2.5 * 10
-4%, N:30 * 10
-4%～120 * 10
-4%, T.O≤18 * 10
-4%; Surplus is Fe and unavoidable impurities.
Preferably, boracic pinion steel of the present invention, its chemical ingredients mass percent is: C:0.17%～0.22%; Si:0.15%～0.30%, Mn:0.80%～1.00%, P≤0.025%; S≤0.025%, Cr:1.00%～1.20%, Ti:0.035%～0.065%; B:0.0008%～0.0015%, Al:0.018%～0.040%, H≤2.5 * 10
-4%, N:45 * 10
-4%～85 * 10
-4%, T.O≤18 * 10
-4%; Surplus is Fe and unavoidable impurities.
The present invention also provides the preparation method of described boracic pinion steel, comprises refining just, refining, vacuum refinement, continuous casting and rolling technology step, and concrete steps are following:
1) refining just: first furnace adopts electric furnace or converter, and first furnace adopts the burden structure of " steel scrap+carbonaceous material " or " all molten iron ", and carbonaceous material comprises the molten iron or the pig iron, mixed carbon comtent 1.50%～4.60%;
Accomplish the decarburization dephosphorization of molten steel, the simultaneous oxidation decarburization balances the boiling, and removes section H and N in the steel; Control is furnace smelting endpoint C:0.04%～0.12% just, P≤0.015%, 1620 ℃～1680 ℃ of tapping temperatures;
2) no slag or few slag tapping; Tapping process according to actual terminal point C content, adds an amount of carbon dust along steel stream in advance, adds slag charge, alloy then and contains aluminium deoxidizer, contains aluminium deoxidizer add-on 1.5kg/t steel～3.0kg/t steel; Before the back of furnace tapping finishing just went to the refining station to molten steel, the control argon flow amount was advisable with top of the slag fine motion;
3) refining: refining furnace adopts the LF stove, send electrochemical slag, residue adjustment, line feeding, stirring at refining furnace, carries out the deoxidization desulfuration of molten steel, and removal is mingled with, adjustment composition, processing such as controlled temperature; At LF refining furnace white slag hold-time 18min～25min, control finishing slag staple mass percent: (CaO) 47%～60%, (SiO
2) 4%～12%, (Al
2O
3) 10%～25%, (FeO)+(MnO)≤1.0%;
4) alloying of boron: the refining of LF refining furnace closes on when finishing, feeding ferro-boron and titanium composite cored wire, or before the molten steel vacuum-treat, directly add ferro-boron;
5) vacuum refinement: vacuum refining furnace adopts VD stove or RH stove; Mainly accomplish molten steel at vacuum refining furnace and take off H, remove part N simultaneously; Molten steel after vacuum refinement is handled, H≤2.5 * 10
-4%;
6) molten steel is after vacuum refinement is handled, and molten steel keeps the argon gas soft blow, and time 10min～40min, soft blow state are top of the slag fine motion, and molten steel is not exposed;
7) continuous casting: the cast of molten steel full guard, ladle and tundish are all added a cover insulation, adopt the mold induction stirring;
8) rolling.
Preferably, step 2) tapping process, the omnidistance Argon of ladle stirs, tapping prometaphase control argon pressure 1.60MPa～0.60Mpa, middle and later periods control argon pressure 0.60MPa～0.20Mpa.
Preferably, the vacuum refinement in the step 4) is at vacuum tightness 67Pa following vacuum outgas hold-time 12min～18min, argon flow amount 100L/min～300L/min, pressure 0.20MPa～0.30Mpa.
Preferably, the continuous casting in the step 6) adopts the cast of molten steel full guard, and ladle and tundish are all added a cover insulation, and tundish molten steel liquid level is not less than 700mm, 15 ℃～30 ℃ of molten steel cast superheating temperature, specific water 0.27L/kg～0.33L/kg.
Preferably, the continuous casting in the step 6), strand straightening temperature >=900 ℃, multi-point straightening.
Preferably, Heating temperature is 1180 ℃～1200 ℃ when rolling, allows the temperature difference≤30 ℃, heat-up time 3.0h～3.5h (strand heat is sent, heat-up time 2.0h～2.8h), 1100 ℃～1180 ℃ of start rolling temperatures, finishing temperature>=850 ℃.
Implement the narrow Composition Control of molten steel, same batch: C: ± 0.01%, Si: ± 0.03%, Mn, Cr: ± 0.02%, Ti: ± 0.015%, B: ± 0.0002%, H≤2.5 * 10
-4%, N: ± 20 * 10
-4%, T.O≤18 * 10
-4%.
Boron alloy method of the present invention, the recovery of boron is stabilized in more than 90%.
The characteristics of technical scheme of the present invention are:
(1) boracic pinion steel of the present invention is to be Pinion Steel main body composition suitably under the prerequisite of adjustment at Cr-Mn-Ti, adds micro-B element.Utilize Ti element fixed nitrogen and crystal grain thinning in the steel; And on the basis of elements such as C, Cr, Mn raising steel hardenability effect, add micro-B element, utilize the compound action of multiple element; Significantly improve the hardening capacity with stabilized steel, and available B substitutes portion C r, Mn.Boracic pinion steel of the present invention; Compare with 20CrMnTiH and sub-grade of steel thereof have hardening capacity high with stablize, be with narrow, use properties improves, and can satisfy heavy-load automobile and big profile shaft tooth class part performance requriements; Pinion Steels such as alternative portion C r-Ni-Mo, Cr-Mo system, characteristics such as production cost is low.
(2) boracic pinion steel of the present invention also is different from 20MnVB, 20Mn
2Pinion Steels such as TiB, 20MnVB, 20Mn
2Pinion Steels such as TiB all are on the basis of single raising hardening capacity element M n, to add boron; Make the hardening capacity of steel too rely on the influence of boron; Cause in use exposing the hardening capacity instability, hardenability band is wide, and the processing, dimensional precision and the work-ing life that influence gear improve.
(3) boracic pinion steel of the present invention is to utilize the carbonitride Ti (NC) of titanium to stop grain growth and nitrogen fixation, makes full use of the hardening capacity that the B element improves steel.The external close boracic pinion steel of composition with it; As press the germany volkswagen company standard and produce ZF6 (16CrMnBH) and ZF7 Pinion Steels such as (20CrMnBH); It all is nitride AlN prevention grain growth with aluminium; B main effect in this type of steel is to form spherical BN, reduces solid solution N amount in the steel, improves the toughness of steel.
(4) the accurate control of micro-B element in the steel of the present invention.The stable control of oxygen, nitrogen content in the smelting process, the reasonable control of titanium content, the adding opportunity of boron and mode and continuous casting protection cast are the keys that realizes that solid solution boron content is precisely controlled in the steel.
(5) boracic pinion steel of the present invention external refining in the preparation process realizes the narrow Composition Control of molten steel, and continuous casting guarantees the production of zero defect continuously cast bloom, has guaranteed the cleanliness factor of molten steel, steel tissue evenly, tiny, densification, be with narrow, the over-all properties height.
Description of drawings
Fig. 1～Fig. 8 is a boracic pinion steel hot-rolled state metallographic structure photo of the present invention.
Fig. 1 is a 1# steel hot-rolled state, 100 *; Fig. 2 is a 2# steel hot-rolled state, 100 *; Fig. 3 is a 3# steel hot-rolled state, 100 *; Fig. 4 is a 4# steel hot-rolled state, 100 *; Fig. 5 is a 1# steel hot-rolled state, 500 *; Fig. 6 is a 2# steel hot-rolled state, 500 *; Fig. 7 is a 3# steel hot-rolled state, 500 *; Fig. 8 is a 4# steel hot-rolled state, 500 *.
Embodiment
Following embodiment is used to set forth the present invention, but protection scope of the present invention is not limited to following examples.
The technological process of production is: electric arc furnace → LF refining furnace → VD vacuum refining furnace → bloom continuous casting → Φ 650 mill millings.
4 heats are produced in test, number 1#, 2#, 3# and 4# respectively; Compared steel numbering 5#, 6#, 7# and 8#.
1, electric arc furnace smelting
Burden structure is steel scrap+molten iron, and the molten iron ratio is greater than 45%; 4 wall lance oxygen decarburizations are main, and the decarburization of 1 fire door oxygen gun blowing is auxilliary; Combine winding-up carbon dust making foamed slag with oxygen blast; With addition of 35kg/t～40kg/t lime slag making dephosphorization; Eccentric bottom tapping stays steel to stay slag operation; Tapping process, argon bottom-blowing stirs, slag charge add-on 13kg/t～16kg/t in the ladle.Press heat, the major control processing parameter is listed in table 1.
Table 1 electric arc furnace smelting boracic pinion steel main technologic parameters
| The heat numbering | Burden structure | Total Intake Quantity, t | Weight of molten iron, t | The molten iron ratio, % | Mixed carbon comtent, % | Molten clear C content, % | Terminal point C content, % | Terminal point P content, % | Tapping temperature, ℃ | Tapping contains aluminium deoxidizer add-on, kg/t |
| 1# | Steel scrap+molten iron | 55.40 | 30.00 | 54.15 | 2.47 | 0.87 | 0.07 | 0.010 | 1665 | 2.0 |
| 2# | Steel scrap+molten iron | 56.20 | 28.00 | 49.82 | 2.29 | 0.96 | 0.06 | 0.010 | 1667 | 2.1 |
| 3# | Steel scrap+molten iron | 54.20 | 28.00 | 51.66 | 2.37 | 0.82 | 0.09 | 0.014 | 1663 | 2.2 |
| 4# | Steel scrap+molten iron | 54.40 | 27.30 | 50.18 | 2.31 | 0.76 | 0.09 | 0.013 | 1664 | 2.0 |
2, the LF refining furnace is smelted
The steel ladle bottom argon blowing gas mixing is mixed, and adopts the SiC diffusive deoxidation, analyzes once feeding aluminum steel deep deoxidation before the appearance, close on tapping before, feeding titanium heart yearn and silicon-calcium wire.Major control processing parameter and finishing slag staple are listed in table 2 and table 3 respectively.
Table 2LF refining furnace is smelted boracic pinion steel major control processing parameter
| The heat numbering | To furnaceman LF position molten steel temperature, ℃ | The aluminum steel feed quantity, kg/t | Once appearance is analyzed Al content, % | The white slag hold-time, min | Tapping temperature, ℃ |
| 1# | 1540 | 0.95 | 0.067 | 21 | 1620 |
| 2# | 1538 | 1.02 | 0.064 | 22 | 1621 |
| 3# | 1543 | 0.96 | 0.059 | 19 | 1616 |
| 4# | 1534 | 0.97 | 0.063 | 20 | 1617 |
Table 3LF refining furnace smelting boracic pinion steel finishing slag staple (mass percent, %)
| The heat numbering | CaO | SiO 2 | Al 2O 3 | FeO | MnO |
| 1# | 55.31 | 6.83 | 17.82 | 0.21 | 0.01 |
| 2# | 54.26 | 7.41 | 19.31 | 0.32 | 0.01 |
| 3# | 56.73 | 6.97 | 18.20 | 0.27 | 0.01 |
| 4# | 55.62 | 8.46 | 16.95 | 0.41 | 0.01 |
3, VD stove vacuum refinement
Ladle is gone into before the VD stove, removes the slag about 50%; Ladle adds ferro-boron (ferro-boron boron content 21.08%) to furnaceman VD position, carry out the molten steel vacuum-treat then.The major control processing parameter is listed in table 4.
Table 4VD stove vacuum refinement boracic pinion steel major control processing parameter
| The heat numbering | Add ferro-boron amount, kg/t before the VD | Reach the following time of vacuum tightness 67Pa, min | The following hold-time of vacuum tightness 67Pa, min | Argon flow amount, L/min | Argon pressure, Mpa | [H] content after the vacuum outgas, 10 -4％ | Molten steel temperature after the vacuum outgas, ℃ | The soft blow time, min |
| 1# | 0.040 | 7 | 12 | 156 | 0.20 | 1.8 | 1574 | 14 |
| 2# | 0.046 | 7 | 12 | 156 | 0.26 | 1.7 | 1570 | 13 |
| 3# | 0.052 | 7 | 12 | 170 | 0.23 | 1.9 | 1571 | 11 |
| 4# | 0.053 | 7 | 12 | 174 | 0.25 | 1.6 | 1572 | 13 |
4, continuous casting
Continuous caster three machines three streams, casting blank specification 260mm * 300mm.Continuous casting adopts the protection of big bag long nozzle argon envelope, and tundish adds low-carbon (LC) insulating covering agent and carbonization rice husk insulation, tundish molten steel liquid level 700mm～750mm, mold submerged nozzle protection pouring type.Hydraulic non-sine oscillation; Mould liquid level is controlled automatically; Adopt the mold induction stirring, parameter 300A/3.0HZ; Two cold employings dynamically control gas one fog cooling a little less than cold mode; 3 alignings of strand.Produce boracic pinion steel continuous casting control process parameters and list in table 5.
Table 5 boracic pinion steel continuous casting control process parameters
| The heat numbering | Go up the steel temperature after the soft blow, ℃ | Molten steel temperature in the tundish, ℃ | Pulling rate, m/min | The specific water, L/kg | Strand advances straightening machine temperature, ℃ |
| 1# | 1568 | 1532～1540 | 0.57～0.60 | 0.30 | 920 |
| 2# | 1567 | 1534～1539 | 0.57～0.60 | 0.29 | 920 |
| 3# | 1567 | 1534～1537 | 0.57～0.60 | 0.30 | 918 |
| 4# | 1568 | 1535～1541 | 0.57～0.60 | 0.30 | 921 |
5, rolling
Strand heat is sent rolling, and heat is sent 700 ℃～730 ℃ of casting blank surface temperatures, 530 ℃～580 ℃ of the process furnace casting blank surface temperatures of packing into.1180 ℃～1200 ℃ of Heating temperatures, allow the temperature difference≤30 ℃, heat-up time 2.0h～2.8h, 1100 ℃～1180 ℃ of start rolling temperatures, finishing temperature>=850 ℃, the round steel of rolling specs Φ 130mm.Produce the rolling control process parameters of boracic pinion steel and list in table 6.
The rolling control process parameters of table 6 boracic pinion steel
| The heat numbering | Heating temperature, ℃ | Heat-up time, h | Start rolling temperature, ℃ | Finishing temperature, ℃ |
| 1# | 1190 | 2.4 | 1140 | 940 |
| 2# | 1189 | 2.5 | 1141 | 940 |
| 3# | 1194 | 2.4 | 1142 | 942 |
| 4# | 1193 | 2.4 | 1141 | 941 |
6, result data
(1) composition
Embodiment of the invention boracic pinion steel becomes to be respectively in table 7 with compared steel.
Table 7 embodiment of the invention boracic pinion steel and compared steel composition (mass percent, %)
(2) stocking service check result
Table 8, table 9 and table 10 are listed in this bright boracic pinion steel of embodiment and compared steel low power, micro test and jominy test respectively.
The macroscopic examination of table 8 embodiment of the invention boracic pinion steel and compared steel
The micro test of table 9 embodiment of the invention boracic pinion steel and compared steel
The jominy test of table 10 embodiment of the invention boracic pinion steel and compared steel
Can be found out by table 7: except that the B element, other alloying elements of compared steel 5# and 6# and embodiment 1#～4# steel are approaching, and the Mn of compared steel 7# and 8#, Cr content are higher.
Can be found out by table 8～table 10 and Fig. 1～Fig. 8: boracic pinion steel macrostructure of the present invention is good, and the inclusion rank is low, and gas content is low, and crystal grain is tiny, dense structure, and the banded structure rank is low, and terminal hardening capacity obviously improves and advantage such as stable.
Claims (5)
1. the preparation method of a boracic pinion steel comprises refining just, refining, vacuum refinement, continuous casting and rolling technology step, said boracic pinion steel, and its chemical ingredients mass percent is: C:0.16%～0.24%; Si≤0.35%, Mn:0.70%～1.25%, P≤0.030%; S≤0.030%, Cr:0.80%～1.45%, Ti:0.020%～0.080%; B:0.0005%～0.0030%, Al:0.015%～0.050%, H≤2.5 * 10
-4%, N:30 * 10
-4%～120 * 10
-4%, T.O≤18 * 10
-4%; Surplus is Fe and unavoidable impurities;
Concrete steps are following:
1) refining just: first furnace adopts electric furnace or converter, and first furnace adopts the burden structure of " steel scrap+carbonaceous material " or " all molten iron ", and carbonaceous material comprises the molten iron or the pig iron, mixed carbon comtent 1.50%～4.60%;
Accomplish the decarburization dephosphorization of molten steel, the simultaneous oxidation decarburization balances the boiling, and removes section H and N in the steel; Control is furnace smelting endpoint C:0.04%～0.12% just, P≤0.015%, 1620 ℃～1680 ℃ of tapping temperatures;
2) no slag or few slag tapping; Tapping process according to actual terminal point C content, adds an amount of carbon dust along steel stream in advance, adds slag charge, alloy then and contains aluminium deoxidizer, contains aluminium deoxidizer add-on 1.5kg/t steel～3.0kg/t steel; Before the back of furnace tapping finishing just went to the refining station to molten steel, the control argon flow amount was advisable with top of the slag fine motion;
3) refining: refining furnace adopts the LF stove, send electrochemical slag, residue adjustment, line feeding, stirring at refining furnace, carries out the deoxidization desulfuration of molten steel, and removal is mingled with, the adjustment composition, and controlled temperature is handled; At LF refining furnace white slag hold-time 18min～25min, control finishing slag staple mass percent: (CaO) 47%～60%, (SiO
2) 4%～12%, (Al
2O
3) 10%～25%, (FeO)+(MnO)≤1.0%;
4) alloying of boron: the refining of LF refining furnace closes on when finishing, feeding ferro-boron and titanium composite cored wire, or before the molten steel vacuum-treat, directly add ferro-boron;
5) vacuum refinement: vacuum refining furnace adopts VD stove or RH stove; Mainly accomplish molten steel at vacuum refining furnace and take off H, remove part N simultaneously; Molten steel after vacuum refinement is handled, H≤2.5 * 10
-4%; Vacuum refinement is at vacuum tightness 67Pa following vacuum outgas hold-time 12min～18min, argon flow amount 100L/min～300L/min, pressure 0.20MPa～0.30MPa;
6) molten steel is after vacuum refinement is handled, and molten steel keeps the argon gas soft blow, and time 10min～40min, soft blow state are top of the slag fine motion, and molten steel is not exposed;
7) continuous casting: the cast of molten steel full guard, ladle and tundish are all added a cover insulation, adopt the mold induction stirring; Continuous casting adopts the cast of molten steel full guard, and ladle and tundish are all added a cover insulation, and tundish molten steel liquid level is not less than 700mm, 15 ℃～30 ℃ of molten steel cast superheating temperature, specific water 0.27L/kg～0.33L/kg;
8) rolling;
It is characterized in that, implement the narrow Composition Control of molten steel, same batch: C: ± 0.01%, Si: ± 0.03%, Mn, Cr: ± 0.02%, Ti: ± 0.015%, B: ± 0.0002%, H≤2.5 * 10
-4%, N: ± 20 * 10
-4%, T.O≤18 * 10
-4%.
2. the preparation method of boracic pinion steel as claimed in claim 1; It is characterized in that step 2) tapping process, the omnidistance Argon of ladle stirs; Tapping prometaphase control argon pressure 1.60MPa～0.60MPa, middle and later periods control argon pressure 0.60MPa～0.20Mpa.
3. the preparation method of boracic pinion steel as claimed in claim 1 is characterized in that, the continuous casting in the step 7), strand straightening temperature >=900 ℃, multi-point straightening.
4. the preparation method of boracic pinion steel as claimed in claim 1 is characterized in that, Heating temperature is 1180 ℃～1200 ℃ when rolling, allows the temperature difference≤30 ℃, heat-up time 3.0h～3.5h, 1100 ℃～1180 ℃ of start rolling temperatures, finishing temperature>=850 ℃.
5. the preparation method of boracic pinion steel as claimed in claim 1 is characterized in that, strand heat is sent, heat-up time 2.0h～2.8h.
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