CN1791696A - Steel bar for steering rack, method for producing the same, and steering rack using the same - Google Patents
Steel bar for steering rack, method for producing the same, and steering rack using the same Download PDFInfo
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Abstract
A steel bar for a steering rack which comprises, in mass %, 0.50 to 0.60 % of C, 0.05 to 0.5 % of Si, 0.2 to 1.5 % of Mn, 0.0005 to 0.003 % of B, 0.005 to 0.05 % of Ti, 0.0005 to 0.1 % of Al and 0.002 to 0.02 % of N, wherein quenched and tempered structures of the portion located at a depth from the surface of the steel bar of D/4, wherein D is the diameter of the steel bar, satisfy the following requirements I), II) and III): I) the area percentage of the sum of tempered bainite and tempered martensite structures is 30 to 100 %, II) the area percentage of a regenerated pearlite structure is 0 to 50 %, and III) the area percentage of the sum of tempered bainite, tempered martensite and regenerated pearlite structures is 50 to 100 %.
Description
Technical field
The present invention relates to be used for steel bar for steering rack, its manufacture method of steering gear of automobile and the steering rack that uses it.
Background technology
Power-assisted mode (hydraulic type power steering) that the turning to of automobile is categorized as by oil pressure and the power-assisted mode (column assist power-assisted) by electricity.
The hydraulic type power steering is existing main flow, and it utilizes engine output by from the pressure oil that oil pump sprayed of running operating physical force being carried out power-assisted.But in the hydraulic type power steering, use, so have the problem that reduces the vehicle fuel utilization ratio because be output as propulsion source with engine.
To this, the column assist power-assisted is utilized the motor assisted diversion power that is driven running by the electric energy of battery.The electric turning booster device is compared with above-mentioned hydraulic type power steering, because the fuel availability of automobile is improved, so popularize gradually in recent years.
In automobile, the steering rack that the subtend left and right directions extends has following requirement:
1) edge etc. is subjected to impacting the shock-resistant characteristic of the excellence of degree that also can be damaged even automobile is driven,
2) though the characteristic that the stress in bending effect also can not be ruptured (fracture-resistant), and
3) wear resistance of rack tooth
In steering rack so, used in the past be the S45C steel (for example, open clear 62-178472 communique and the spy opens clear 62-180018 communique with reference to the spy), medium carbon steel (for example, open the 2000-153336 communique and the spy opens the 2001-79639 communique) etc. with reference to the spy.Also have, improve wear resistance by forming cementation zone on the surface, and also improve the intensity (fracture-resistant) of relative stress in bending by high-frequency quenching.
Even for example improve the flexural strength of steering rack by high-frequency quenching, if but excessive load acts on the high-frequency quenching layer temporarily chaps, then might this be full of cracks enlarge, until fracture to inside.
In addition, in the column assist power-assisted of popularizing gradually in recent years, the contact surface of steering rack and pinion(gear) (Pinion Gear) is pressed with the tendency higher than hydraulic type power steering, in the S45C steel, and its wear resistance deficiency.Also have in medium carbon steel, improve wear resistance if improve the amount of C, but shock-resistance can descend.
For example open in the flat 10-8189 communique and put down in writing: carry out under the situation of high-frequency quenching adding B, even the diastrophic steering rack steel that the excessive load effect does not have brittle rupture to take place yet the spy.This steering rack steel is to have omitted the steel that Q-tempering is handled, and its tissue is essentially ferritic-pearlitic.
Summary of the invention
The object of the present invention is to provide that a kind of to improve wear resistance and shock-resistance also excellent, and the steering rack that can prevent the expansion of chapping is with rod iron and manufacture method thereof and the steering rack that uses it.
Present inventors have finished the present invention according to following discovery: even increase the C amount, if but add B then can prevent the decline of shock-resistance, if in addition within the limits prescribed then can improve the flexural deformation energy, with tempering bainite tissue, tempered martensite and the control of regeneration pearlitic structure thus even be full of cracks takes place a bit also can prevent that the expansion of chapping from connecting.
Promptly, steel bar for steering rack of the present invention contains C:0.50～0.60 quality %, Si:0.05～0.5 quality %, Mn:0.2～1.5 quality %, B:0.0005～0.003 quality %, Ti:0.005～0.05 quality %, Al:0.0005～0.1 quality % and N:0.002～0.02 quality %.If the diameter of above-mentioned steel bar for steering rack is D, the Q-tempering tissue apart from the part of case depth D/4 of bar steel is adjusted into satisfies following I), II) and condition III)
I) the total area percentage of tempering bainite tissue and tempered martensite is 30～100%.
II) area percentage of regeneration pearlitic structure is 0～50%.
III) the total area percentage of tempering bainite tissue, tempered martensite and regeneration pearlitic structure is 50～100%.
Also have, above-mentioned driving rack bar steel can also contain Cr.Also can contain free-cutting machinability element (S, Pb, Bi, Te, Mg, Ca, rare earth element, Zr etc.) in addition.
Steel bar for steering rack of the present invention, can make by the following method, with rolling steel disc and bar steel quench more than 780 ℃ from temperature, make the bainite structure of part of depth D/4 and martensitic stucture with after adding up to 30～100% (area percentages), put into the stove of the atmosphere temperature that is heated to 660～720 ℃ of temperature, carry out the short period of time temper below 20 minutes, be cooled to room temperature.
Description of drawings
The graphic representation of the time when Fig. 1 is the thermal treatment of expression when making steel bar for steering rack of the present invention and the relation of temperature.
Fig. 2 is an approximate three-dimensional map of representing the shape of test board used in the experimental example.
Fig. 3 is the mode chart of the schematic configuration that comprises the electric turning booster device that rotates tooth bar of expression one embodiment of the present invention.
Fig. 4 A is the side-view of the partly cut-away of steering rack 8, and Fig. 4 B is the sectional view along the 4B-4B line of Fig. 4 A.
Fig. 5 is the sketch chart of the testing apparatus of the static rupture test of positive input.
Fig. 6 is the sketch chart of the testing apparatus of the static rupture test of contrary input.
Fig. 7 is the sketch chart of the testing apparatus of contrary input shock test.
Fig. 8 is the sketch chart of the testing apparatus of bending strength test.
Fig. 9 is the sketch chart of the testing apparatus of positive input long duration test.
Figure 10 is the sketch chart of the testing apparatus of contrary input long duration test.
Figure 11 A is the outline elevation of test film, and Figure 11 B is the sketch chart of the testing apparatus of fatigue-bending test.
Embodiment
Steel bar for steering rack of the present invention contains C:0.50～0.60 quality %, Si:0.05～0.5 quality %, Mn:0.2～1.5 quality %, B:0.0005～0.003 quality %, Ti:0.005～0.05 quality %, Al:0.0005～0.1 quality %, N:0.002～0.02 quality %.In addition, be preferably the Cr that contains (not comprising 0 quality %) below the 1.5 quality %.Also having remainder is Fe and unavoidable impurities.
The qualification reason of mentioned component, as described below.
The C amount is made as more than the 0.50 quality %, is because the wear resistance can improve as steering rack (for example, column assist power-assisted use steering rack) fully the time.Preferred C amount is more than the 0.52 quality %.But the C amount is too much, then can reduce the shock-resistant characteristic of steering rack.Therefore, the C amount is made as below the 0.60 quality %, is preferably below the 0.58 quality %, more preferably below the 0.56 quality %.
The Si amount is made as more than the 0.05 quality %, is because carry out the deoxidation of steel.The amount of preferred Si is more than the 0.10 quality %, is preferably especially more than the 0.15 quality %.But the amount of Si is too much, then can reduce the machinability when forming rack tooth.Therefore, the amount of Si is made as below the 0.5 quality %, is preferably below the 0.35 quality %, more preferably below the 0.30 quality %.
The Mn amount is made as more than the 0.2 quality %, is not only because in order to improve the intensity of steel,, thereby improve flexural deformation energy when steel are processed into steering rack also in order to make it generate bainite structure easily by improving hardenability.The amount of preferred Mn is more than the 0.5 quality %, is preferably especially more than the 0.7 quality %.But the amount of Mn is too much, and is then dark excessively by the hardened layer of high-frequency quenching, reduces the flexural deformation energy.Therefore, the amount of Mn is made as below the 1.5 quality %, is preferably below the 1.3 quality %, more preferably below the 1.2 quality %.
The B amount is made as more than the 0.0005 quality %, is in order to guarantee shock-resistant characteristic in the steel of the present invention that has increased the C amount.The amount of preferred B is more than the 0.0007 quality %.But the amount of B is too much, then can generate deleterious B based compound and can reduce shock-resistant characteristic on the contrary.Therefore, the amount of B is made as below the 0.003 quality %, is preferably below the 0.0025 quality %, more preferably below the 0.0020 quality %.
Ti forms the formation that TiN suppresses BN by combining with N in the steel, and is effective to the above-mentioned effect of guaranteeing B.Therefore the amount of Ti is more than the 0.005 quality %, is preferably more than the 0.010 quality %, more preferably more than the 0.012 quality %.But the amount of Ti is too much, then can reduce the shock-resistant characteristic of steering rack on the contrary.Therefore the amount of Ti is made as below the 0.05 quality %, is preferably below the 0.04 quality %, more preferably below the 0.035 quality %.
Making it contain Al and N, is because by forming AlN, the austenite grain in the time of can the refinement high-frequency quenching.The amount of Al is more than the 0.0005 quality %, is preferably more than the 0.010 quality %, more preferably more than the 0.020 quality %.Also having the amount of N is more than the 0.002 quality %, is preferably more than the 0.003 quality %, more preferably more than the 0.004 quality %.But the amount of Al, N is crossed and is reduced shock-resistant characteristic at most.Therefore, the amount of Al is made as below the 0.1 quality %, is preferably below the 0.08 quality %, more preferably below the 0.05 quality %.The amount of N is made as below the 0.02 quality %, is preferably below the 0.01 quality %, more preferably below the 0.007 quality %.
Making it contain Cr, is in order to improve hardenability.Though the lower limit of the amount of Cr does not limit especially, for example about 0.05 quality %, be preferably about 0.08 quality %, more preferably about 0.10 quality %.But the amount of Cr is too much, and then the hardened layer that is formed by high-frequency quenching is dark excessively, and flexural deformation can be not enough.Therefore the amount of Cr for example is made as below the 1.5 quality %, is preferably below the 1.0 quality %, more preferably below the 0.50 quality %.
Also have steel bar for steering rack of the present invention, can also contain free-cutting machinability element (S, Pb, Bi, Te, Mg, Ca, rare earth element, Zr etc.) as required.The amount of these free-cutting machinability elements such as following degree, for example, S:0.06 quality % following (not containing 0 quality %), Pb:0.3 quality % following (not containing 0 quality %), Bi:0.2 quality % following (not containing 0 quality %), Te:0.1 quality % following (not containing 0 quality %), Mg:0.01 quality % following (not containing 0 quality %), Ca:0.01 quality % following (not containing 0 quality %), rare earth element (REM): 0.01 quality % following (not containing 0 quality %), Zr:0.3 quality % following (not containing 0 quality %).These free-cutting machinability elements can add separately or two or more combination is added.
As rare earth element, can exemplify out Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.
So steel bar for steering rack of the present invention, the Q-tempering tissue apart from the part of depth D/4 (D represents the bar steel diameter) on surface of bar steel can be as following 1), 2) and 3) adjust.
1) total of tempering bainite tissue and tempered martensite (below, be expressed as " TB+TM " sometimes) is 30～100% (area percentages).
2) the regeneration pearlitic structure is 0～50% (area percentage).
3) total of tempering bainite tissue, tempered martensite and regeneration pearlitic structure (below, be expressed as " TB+TM+RP " sometimes) is 50～100% (area percentages).
Below, the part of depth D/4 that the distance of above-mentioned bar steel is surperficial abbreviates D/4 portion as.
Below, the reason of these organizational controls is described.
Tempering bainite tissue and tempered martensite are the tissues that obtains through Q-tempering by with the bar steel after rolling, and the expansion of the be full of cracks that the high-frequency quenching layer is taken place when preventing as steering rack connects effectively.
Promptly, steering rack is because high-frequency quenching portion (skin section) is extremely hard, if bestow bigger bending then turn near the root of tooth (usually, near the D/4 portion) the high-frequency quenching layer break easily, if have tempering bainite tissue and tempered martensite remaining on high-frequency quenching portion and the border of not implementing high-frequency quenching portion, then can prevent to enlarge to inside, can prevent breaking of steering rack self in the be full of cracks that the high-frequency quenching layer takes place.Therefore the fiery bainite structure of D/4 part and the total (TB+TM) of tempered martensite are more than 30%.Be preferably more than 40%, more preferably more than 50%.
The regeneration pearlitic structure is the tissue that produces in tempering process, be with rolling after other tissue of pearlitic structure phase region of steel.Regeneration pearlitic structure, different with tempering bainite tissue and tempered martensite, inoperative to the expansion perforation that prevents to chap, the regeneration pearlitic structure is too much, also can reduce the flexural deformation energy.Therefore the pearlitic structure of regenerating is made as below 50%.Be preferably below 40%, more preferably below 30%.The pearlitic structure of regenerating in addition tails off, and shock-resistant characteristic has the tendency that further improves.
Even obtain tempering bainite tissue and tempered martensite by Q-tempering in addition, if but, can not prevent that then the expansion of chapping from connecting from rolled stock the ferritic-pearlitic tissue or the soft ferritic tissue residue of (keeping the rolling material of state afterwards).
Therefore, be necessary to reduce these tissues, promptly be necessary to increase tempering bainite tissue and tempered martensite in other words from rolled stock.Total (TB+TM+RP) by 3 tissues that these Q-tempering operations generated is) more than 50%, be preferably more than 60%, more preferably more than 70%.
The diameter of steel bar for steering rack of the present invention does not limit especially, still considers and is processed into steering rack, is generally about 10～40mm.Be preferably about 15～38mm, more preferably about 20～36mm.
Aforesaid steel bar for steering rack can be made, for example in the following way, the steel disc that mentioned component is formed is rolled, bar steel to gained quenches, and after obtaining bainite structure and martensitic stucture, carries out the temper between high temperature, short time.
The Heating temperature of quenching in this manufacture method is more than 780 ℃, is preferably more than 800 ℃.The Heating temperature of quenching is low excessively, and then the TB+TM+RP after the tempering has the tendency that diminishes.Can generate the softish ferrite lamellae in addition, make the undercapacity of steering rack.The upper limit of Heating temperature for example is about 860 ℃, to be preferably about 850 ℃.Heating temperature is too high when then quenching, and the bending of bar steel has the tendency that becomes big.
The cooling conditions that quenches, be necessary to make by formed above-mentioned bainite structure of D/4 portion and the adding up to more than 30% (area percentage) of martensitic stucture of quenching, be preferably more than 40% (area percentage), more preferably more than 50% (area percentage).The condition of such controlled chilling, can carry out suitable setting according to composition of steel etc., for example, wish the zone about 800～300 ℃ of temperature (being preferably 750～350 ℃), cool off with 30～80 ℃/second of speed of cooling (being preferably 40～70 ℃/second).
The resulting intermediate that has imported bainite structure and martensitic stucture like this with reference to Fig. 1, comprises temperature-rise period with below 20 minutes, and the treatment time t that is preferably below 15 minutes carries out temper, and air cooling is to room temperature.Making the atmosphere temperature T 2 of the employed stove of temper is about 660～720 ℃, is preferably about 680～700 ℃.
If the atmosphere temperature T 2 of stove is made as more than 660 ℃, even carry out the tempering of the short period of time below 20 minutes, also can reduce the Vickers' hardness (it is following for example can to obtain 320HV) when tempered, can improve the machinability when being processed into steering rack thereafter.Also have, the atmosphere temperature T 2 of stove is preferably 680～700 ℃.
In order to control the tissue after the tempering, become in above-mentioned D/4 portion 27, the area percentage of the total of tempering bainite tissue and tempered martensite is 30～100%, the area percentage of regeneration pearlitic structure is 0～50%, and the area percentage of the total of tempering bainite tissue, tempered martensite and regeneration pearlitic structure is 50～100%, preferably in above-mentioned tempered condition (more than 660 ℃, in 20 minutes) scope in, do not make tempering temperature too high, tempering time is long.
This is that tempering time is long because if tempering temperature is too high, and then the area percentage by formed bainite structure of controlled chilling and martensitic stucture reduces easily, and perlite is regenerated curved characteristic decline easily.
The steel bar for steering rack of the present invention that so obtains, because wear resistance improves and shock-resistance is also excellent, and flexural deformation can be excellent, so exceedingly useful to steering rack (particularly column assist power-assisted steering rack).
Experimental example 1～36
The steel of composition shown in following table 1～2 of melting are rolled into the bar steel of diameter 30mm.After then being heated to the temperature shown in table 1～2, finish quenching by controlled chilling to room temperature.Also has in this controlled chilling the conversion water yield and water-cooled time and control the tissue of bar steel.Cooled bar steel is finished tempering by the time shown in delay table 1～2 in the stove that is heated to the atmosphere temperature shown in table 1～2.Bar steel after the tempering is put cold.
Tissue to the D/4 portion of the tissue of the D/4 portion of the bar steel after quenching and the bar steel after the tempering, observe (5000 times of multiplying powers) by electron microscope, obtain the area occupation ratio of martensitic stucture and bainite structure and tempered martensite, tempering bainite tissue and regeneration pearlitic structure.
Experimental example 1～19 its composition and to organize both sides all suitably to be included in of the present invention be in the scope of technology, experimental example 20～36 its compositions and organize at least one side improper are outside scope of the present invention.
Also have fracture-resistant (flexural deformation energy), shock-resistant characteristic, wear resistance when investigating bar steel after the tempering, and carried out following experiment as steering rack.
Pliability test
After bar steel after the tempering carried out drawing and be processed to form diameter 27.5mm, cutting formed rack tooth.The degree of depth of rack tooth is approximately about D/4.Then with following condition by tooth portion is carried out high-frequency quenching, make steering rack.
The high-frequency quenching condition
Use coil: face quenches with (diameter 40mm, thickness 2mm)
Voltage: 4.0kV
Electric current: 4.5A
Frequency: 40kHz
Type of heating: move quench (translational speed 3.0mm/ second)
Cooling: the mixed solvent of water soluble oils and water
Use the steering rack of gained, having carried out is that the opposite side of tooth of length of support, steering rack is 3 pliability tests of pressing position with 400mm, estimates according to following standard.
*: the be full of cracks expansion that takes place at the high-frequency quenching layer penetrates into inside, and steering rack is fractured into two
Zero: be full of cracks Halfway Stopping, not fracture
Shock test
After bar steel after the tempering carried out drawing and be processed to form diameter 27.5mm, cut out JIS3 U nick-break test sheet from D/4 portion, high-frequency quenching is carried out on the surface that otch is formed side.The high-frequency quenching condition is 3.5mm/ second except that translational speed, and is identical with the situation of above-mentioned pliability test.Test film to gained carries out pendulum impact experiment (test temperature: room temperature), obtain impact value according to JIS-Z2242.
Wearing test
Be modulated into the plectane that has with by the tempering bar steel same characteristic features of experimental example gained.Be the steel of the bar steel identical component of melting and experimental example, become diameter 53mm by forge hot, cut into the plectane of thickness 15mm after, with the condition identical with each experimental example quench, tempering,
Then be machined into semi-circular plate (the diameter 44mm on upper strata, the thickness 3mm on upper strata of 2 layers of shape as shown in Figure 2; The diameter 50mm of lower floor, the thickness 5mm of lower floor), upper layer part has been carried out high-frequency quenching.The condition of high-frequency quenching is except that translational speed is 2.5mm/ second, identical with the situation of above-mentioned pliability test.Resulting test board is carried out dials method (pin on disk) wearing test, the wearing and tearing reduction of determination test sheet.Also have the detailed conditions of wearing test, as follows.
Lubricated: dry type
Test film surfaceness: Ra0.25 μ m
Peripheral speed: 0.05m/ second
Face is pressed: 0.05Gpa
Pin: SUJ2 (diameter 5mm, Rockwell hardness (HRC) 64)
The result represents in table 1～2.
Table 1
| Embodiment | Steel are formed (unit=quality %; Remainder is Fe and unavoidable impurities) | Quenching process | Tempering process | Pliability test | Impact value (J/cm 2) | Wearing and tearing decrement (mg) | ||||||||||||
| C | Si | Mn | B | Ti | Cr | Al | N | Heating temperature (℃) | Tissue [B+M] (area %) | Furnace temperature (℃) | Residence time (minute) | Tissue [TB+TM] (area %) | Tissue [RP] (area %) | Tissue [TB+TM+RP] (area %) | ||||
| 1 | 0.52 | 0.20 | 0.83 | 0.0016 | 0.021 | - | 0.041 | 0.0040 | 810 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 56 | 10 |
| 2 | 0.56 | 0.18 | 0.89 | 0.0014 | 0.022 | - | 0.040 | 0.0042 | 810 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 51 | 6 |
| 3 | 0.53 | 0.19 | 1.06 | 0.0012 | 0.023 | - | 0.048 | 0.0049 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 52 | 8 |
| 4 | 0.54 | 0.22 | 0.72 | 0.0017 | 0.020 | - | 0.040 | 0.0044 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 54 | 7 |
| 5 | 0.54 | 0.24 | 0.88 | 0.0008 | 0.022 | - | 0.041 | 0.0042 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 51 | 7 |
| 6 | 0.53 | 0.24 | 0.76 | 0.0018 | 0.022 | - | 0.045 | 0.0044 | 830 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 52 | 6 |
| 7 | 0.54 | 0.20 | 0.75 | 0.0010 | 0.015 | - | 0.048 | 0.0047 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 53 | 7 |
| 8 | 0.53 | 0.22 | 0.82 | 0.0014 | 0.023 | - | 0.040 | 0.0041 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 53 | 6 |
| 9 | 0.54 | 0.23 | 0.83 | 0.0011 | 0.022 | 0.13 | 0.050 | 0.0041 | 830 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 53 | 7 |
| 10 | 0.54 | 0.24 | 0.82 | 0.0016 | 0.020 | 0.21 | 0.048 | 0.0046 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 54 | 8 |
| 11 | 0.53 | 0.24 | 0.86 | 0.0013 | 0.021 | - | 0.049 | 0.0041 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 52 | 9 |
| 12 | 0.54 | 0.21 | 0.75 | 0.0014 | 0.022 | - | 0.042 | 0.0049 | 830 | 80 | 690 | 10 | 80 | 0 | 80 | ○ | 51 | 8 |
| 13 | 0.53 | 0.23 | 0.73 | 0.0012 | 0.022 | - | 0.048 | 0.0043 | 830 | 70 | 690 | 10 | 70 | 0 | 70 | ○ | 51 | 8 |
| 14 | 0.53 | 0.24 | 0.74 | 0.0013 | 0.021 | - | 0.046 | 0.0045 | 820 | 60 | 690 | 10 | 60 | 0 | 60 | ○ | 52 | 8 |
| 15 | 0.53 | 0.20 | 0.83 | 0.0011 | 0.021 | - | 0.047 | 0.0044 | 810 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 53 | 7 |
| 16 | 0.54 | 0.23 | 0.84 | 0.0012 | 0.021 | - | 0.040 | 0.0041 | 820 | 90 | 690 | 5 | 90 | 0 | 90 | ○ | 52 | 8 |
| 17 | 0.55 | 0.24 | 0.86 | 0.0013 | 0.022 | - | 0.048 | 0.0047 | 820 | 90 | 720 | 10 | 70 | 20 | 90 | ○ | 50 | 7 |
| 18 | 0.54 | 0.21 | 0.86 | 0.0010 | 0.022 | - | 0.047 | 0.0049 | 840 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 53 | 7 |
| 19 | 0.53 | 0.22 | 0.77 | 0.0013 | 0.022 | - | 0.040 | 0.0044 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 51 | 8 |
The total of [B+M] expression bainite structure and martensitic stucture; The total of [TB+TM] expression tempering bainite tissue and tempered martensite; [RP] expression regeneration pearlitic structure.
The total of [TB+TM+RP] expression tempering bainite tissue, tempered martensite and regeneration pearlitic structure.
Table 2
| Embodiment | Steel are formed (unit=quality %; Remainder is Fe and unavoidable impurities) | Quenching process | Tempering process | Pliability test | Impact value (J/cm 2) | Wearing and tearing decrement (mg) | ||||||||||||
| C | Si | Mn | B | Ti | Cr | Al | N | Heating temperature (℃) | Tissue [B+M] (area %) | Furnace temperature (℃) | Residence time (minute) | Tissue [TB+TM] (area %) | Tissue [RP] (area %) | Tissue [TB+TM+RP] (area %) | ||||
| 20 | 0.46 | 0.23 | 0.82 | 0.0017 | 0.022 | - | 0.042 | 0.0043 | 820 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 61 | 62 |
| 21 | 0.64 | 0.22 | 0.76 | 0.0011 | 0.021 | - | 0.044 | 0.0041 | 830 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 16 | 5 |
| 22 | 0.55 | 0.21 | 0.12 | 0.0015 | 0.022 | - | 0.045 | 0.0043 | 810 | 10 | 690 | 10 | 10 | 0 | 10 | × | 51 | 7 |
| 23 | 0.53 | 0.24 | 1.60 | 0.0017 | 0.020 | - | 0.050 | 0.0045 | 830 | 90 | 690 | 10 | 90 | 0 | 90 | × | 53 | 9 |
| 24 | 0.53 | 0.21 | 0.82 | 0.0002 | 0.023 | - | 0.046 | 0.0048 | 830 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 23 | 8 |
| 25 | 0.54 | 0.21 | 0.82 | 0.0054 | 0.021 | - | 0.050 | 0.0048 | 830 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 14 | 7 |
| 26 | 0.54 | 0.23 | 0.79 | 0.0014 | 0.002 | - | 0.049 | 0.0047 | 840 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 26 | 7 |
| 27 | 0.55 | 0.22 | 0.88 | 0.0013 | 0.113 | - | 0.041 | 0.0045 | 810 | 90 | 690 | 10 | 90 | 0 | 90 | ○ | 24 | 5 |
| 28 | 0.54 | 0.22 | 0.85 | 0.0014 | 0.022 | 1.64 | 0.044 | 0.0042 | 830 | 90 | 690 | 10 | 90 | 0 | 90 | × | 52 | 8 |
| 29 | 0.54 | 0.21 | 0.88 | 0.0013 | 0.021 | - | 0.050 | 0.0045 | 020 | 20 | 690 | 10 | 20 | 0 | 20 | × | 51 | 0 |
| 30 | 0.53 | 0.22 | 0.83 | 0.0014 | 0.024 | - | 0.043 | 0.0041 | 810 | 20 | 730 | 10 | 10 | 40 | 50 | × | 18 | 9 |
| 31 | 0.55 | 0.23 | 0.80 | 0.0012 | 0.023 | - | 0.043 | 0.0048 | - | 0 | - | - | 0 | 0 | 0 | × | 21 | 6 |
| 32 | 0.53 | 0.22 | 0.79 | 0.0014 | 0.020 | - | 0.044 | 0.0041 | 840 | 90 | 750 | 5 | 30 | 60 | 90 | × | 10 | 9 |
| 33 | 0.54 | 0.22 | 0.78 | 0.0014 | 0.023 | - | 0.041 | 0.0042 | 830 | 90 | 750 | 10 | 10 | 70 | 80 | × | 15 | 8 |
| 34 | 0.53 | 0.23 | 0.79 | 0.0012 | 0.022 | - | 0.042 | 0.0043 | 830 | 90 | 740 | 30 | 10 | 60 | 70 | × | 17 | 7 |
| 35 | 0.53 | 0.21 | 0.74 | 0.0013 | 0.022 | - | 0.042 | 0.0049 | 760 | 40 | 690 | 10 | 40 | 0 | 40 | × | 52 | 8 |
| 36 | 0.54 | 0.20 | 0.74 | 0.0014 | 0.022 | - | 0.045 | 0.0045 | 750 | 30 | 690 | 10 | 30 | 0 | 30 | × | 51 | 8 |
The total of [B+M] expression bainite structure and martensitic stucture; The total of [TB+TM] expression tempering bainite tissue and tempered martensite; [RP] expression regeneration pearlitic structure.
The total of [TB+TM+RP] expression tempering bainite tissue, tempered martensite and regeneration pearlitic structure.
Experimental example 20～28th in the table 2, the inappropriate example of design mix.So it is promptly insufficient because of C quantity not sufficient wear resistance in experimental example 20.So experimental example 21 is opposite because the too much shock-resistant characteristic of C amount is insufficient.
Because the few hardenability of Mn amount is poor, so the total quantity not sufficient of tempering bainite tissue and tempered martensite, flexural deformation can be insufficient in experimental example 22.
Experimental example 23 is because the Mn amount is excessive, so the hardened layer during high-frequency quenching deepens, flexural deformation can be insufficient.
In experimental example 24～27, so because B or the improper shock-resistance of Ti amount are insufficient.
Experimental example 28 is because the Cr amount is excessive, so the hardened layer during high-frequency quenching deepens, flexural deformation can be insufficient.
Also have, from experimental example 29～36 as can be known,, but organize improper each characteristic also can be insufficient even the composition design suitably.The i.e. total quantity not sufficient of tempering bainite tissue and tempered martensite in experimental example 29～31 is so that flexural deformation becomes is insufficient.
In experimental example 32～34, because the regeneration pearlitic structure is too much, that flexural deformation can become is insufficient.In experimental example 35～36, because the total quantity not sufficient of tempering bainite tissue, tempered martensite and regeneration pearlitic structure, so flexural deformation can be insufficient.
Relatively therewith, experimental example 1～19, because composition designs and organizes both sides all very suitable, thus both sides' excellence of shock-resistant characteristic and wear resistance, and can prevent that the expansion of chapping from connecting.
According to steel bar for steering rack of the present invention,,, and can prevent that the expansion of chapping from connecting so wear resistance improves and shock-resistant characteristic is also excellent because to composition and organize both sides suitably to control.
Then, Fig. 3 is the mode chart of schematic configuration of the electric turning booster device of the expression steering rack that contains the steel bar for steering rack that has used the invention described above.
With reference to Fig. 3, electric turning booster device (EPS:Electric Power Steering System) 1 has: be connected in bearing circle and be the steering shaft 3 on the steering component 2; Be connected in tunnel shaft 5 on the steering shaft 3 by universal joint 4; Be connected in the shaft pinion 7 of tunnel shaft 5 by universal joint 6; The steering rack 8 of the steering shaft that has the rack tooth 8a that is meshed with the pinion(gear) 7a that is located at shaft pinion 7 leading sections and extend as left and right directions to automobile.
Steering rack 8 is supported on the vehicle body in the fixed housing (housing) 17 by not shown a plurality of bearings, can freely carry out linear reciprocation and move.The pair of end portions of steering rack 8 is two side-prominent to housing 17, combines with drag link 9 respectively in each end.Each drag link 9 is connected in corresponding turning to on the wheel 10 by corresponding steering arm (not shown).
Steering component 2 is subjected to operation to make steering shaft 3 rotation, and then this rotation is transformed into along the translational motion of the steering rack 8 of the left and right directions of automobile by pinion(gear) 7a and rack tooth 8a.Thus, realize turning to turning to wheel 10.
Steering shaft 3 is divided into input shaft 3a that is connected in steering component 2 and the output shaft 3b that is connected in shaft pinion 7, and these inputs, output shaft 3a, 3b are connected on same axis by torsion bar 11, and can rotate relatively mutually.
Be provided with by detecting the torque transducer 12 of moment of torsion between input, output shaft 3a, 3b via the relative swing offset amount of torsion bar 11, the moment of torsion detected result of this torque transducer 12, input ECU (Electric Control Unit: electronic control unit) 13.In EUC13,, turn to and auxiliaryly control with the driving of electro-motor 15 by driving 14 pairs in loop according to the speed of a motor vehicle detected result of moment of torsion detected result and never illustrated vehicle speed sensor gained.
The output rotation of electro-motor 15 is slowed down by retarding mechanism 16, is sent to shaft pinion 7 by output shaft 3b, tunnel shaft 5, is transformed into the translational motion of steering rack 8, thus assisted diversion.
As retarding mechanism, be a kind of gear mechanism that can example, have: be connected in the not shown turning axle of electro-motor 15 and the pinion(gear) 16a of the worm shaft that can rotate together etc.; Be engaged in this pinion(gear) 16a and be connected in the master wheel 16b of worm gear that output shaft 16b can rotate together etc.
Fig. 4 A is the cut-away section front view of steering rack 8, and Fig. 4 B is the sectional view along the 4B-4B line of Fig. 4 A.Steering rack 8 has: the main body 20 of the pole shape of diameter D; Be located at one one the par 21 of the side face 20a of this main body 20; Be located at the rack tooth formation portion 22 of this par 21.
Steering rack 8 uses the steel bar for steering rack of the invention described above and forms.Be steering rack 8 employed steel bar for steering rack, contain C:0.50～0.60 quality %, Si:0.05～0.5 quality %, Mn:0.2～1.5 quality %, B:0.0005～0.003 quality %, Ti:0.005～0.05 quality %, Al:0.0005～0.1 quality % and N:0.002～0.02 quality %.
Also have the Q-tempering tissue apart from the part of case depth D/4 (diameter with bar steel is D) of bar steel to satisfy following I), II) and condition III).
I) the total area percentage of tempering bainite tissue and tempered martensite is 30～100%.
II) area percentage of regeneration pearlitic structure is 0～50%.
III) the total area percentage of tempering bainite tissue, tempered martensite and regeneration pearlitic structure is 50～100%.
In being used to form the above-mentioned steel bar for steering rack of steering rack 8, preferably contain the 1.5 quality % Cr of following (not containing 0 quality %).
Contain in being used to form the above-mentioned steel bar for steering rack of steering rack 8, also contain following optional at least a, S:0.06 quality % following (not containing 0 quality %), Pb:0.3 quality % following (not containing 0 quality %), Bi:0.2 quality % following (not containing 0 quality %), Te:0.1 quality % following (not containing 0 quality %), Mg:0.01 quality % following (not containing 0 quality %), Ca:0.01 quality % following (not containing 0 quality %), rare earth element: 0.01 quality % following (not containing 0 quality %), Zr:0.3 quality % following (not containing 0 quality %).
As mentioned above, the carbon amount of the steel of formation steering rack 8 is 0.50～0.60 quality %.The carbon amount is made as 0.50 quality %, is because by steel are carried out high-frequency quenching described later, thereby improves the wear resistance of rack tooth 8a.But the carbon amount surpasses 0.60 quality %, and then the shock-resistant characteristic of steering rack 8 will descend, and thermal crack takes place when also having high frequency heat to handle easily.Therefore, the carbon amount is made as below the 0.60 quality %, is preferably below the 0.58 quality %, more preferably below the 0.58 quality %.
Also have, in the steel that forms steering rack 8, containing B is 5～30ppm.By adding the B more than the 5ppm, can strengthen the crystal boundary of high-frequency quenching part, can increase toughness especially and improve flexural deformation energy (fracture-resistant), on the other hand, cross 30ppm even make it contain B ultrasonic, because its effect is saturated, so preferably set in the scope of 5～30ppm.
High-frequency quenching and the tempering carried out after forming by rack tooth 8a, steering rack 8 be provided with hardened layer 25 in rack tooth formation portion 22 at least.The surface hardness of rack tooth formation portion 22 is set at Vickers hardness tester 680～800HV.
This be because, be lower than 680HV, then the surface hardness of rack tooth formation portion 22 is insufficient, relatively the fault bound step-down of flexural fatigue on the other hand, surpasses 800HV, then the toughness of skin section descends, with respect to static load or intend the flexural strength deficiency of static load.
Therefore, be made as 680～800HV, can improve the fault bound of relative flexural fatigue, and guarantee sufficient flexural strength with respect to static load or plan static load by the surface hardness that rack tooth is formed portion.
Also have, in rack tooth formation portion 22, the effective case depth d of the hardened layer 25 of the tooth bottom 24 between rack tooth 8a is preferably apart from the scope of the surface 0.1～1.5mm of tooth bottom 24.Here, the effective case depth d of hardened layer 25 is defined as the distance of the hardness position from the surface to 450HV, is equivalent to effective case depth.
The effective case depth d of the hardened layer 25 of tooth bottom 24 surpasses under the situation of 1.5mm, when being subjected to HI high impact, the place local bending at the pars intermedia of the lengthwise direction of steering rack 8 has the tendency that curves the chevron shape, its result might become on steering rack 8 and can not move by pinion(gear) 7a.On the other hand, when the effective case depth d of hardened layer 25 is lower than 0.1mm, near the flexural strength deficiency the tooth root of possible rack tooth 8a.
Therefore, be made as the scope of 0.1～1.5mm by effective case depth d with the hardened layer 25 of tooth bottom 24, can guarantee the teeth bending strength of rack tooth 8a, and make time spent steering rack 8 whole bending, the steering qualitiess when guaranteeing very of relaxing in big load.The effective case depth d of the hardened layer 25 of tooth bottom 24 more elects 0.3～1.2mm as.
For example, the tooth bottom is positioned at the degree of depth about D/4 and forms rack tooth 8a.Therefore, at the side face 20a of main body 21, apart from radially with the degree of depth on part 26 surfaces of rack tooth formation portion 22 subtends part 27 (being also referred to as (3/4) D portion 27) for (3/4) D, become through quenching part and without the approximate bounds of the part of quenching.
In above-mentioned (3/4) D portion 27, the total area percentage that is set at tempering bainite tissue and tempered martensite is 30～100%, the area percentage of regeneration pearlitic structure is 0～50%, and the total area percentage of tempering bainite tissue, tempered martensite and regeneration pearlitic structure is 50～100%.This can be by steering rack 8 the electron micrograph of cut surface observe.
Excessive flexural deformation takes place even be subjected to the tooth bar of big load, generate crackle in its part, by in the tempering bainite tissue of 30% remaining at least area percentage of above-mentioned (3/4) D portion and the propagation that tempered martensite prevents crackle, also can prevent the breakage that tooth bar breaks and is divided into two sections.Also have, in above-mentioned (3/4) D portion, the area percentage of regeneration pearlitic structure is made as below 50%, is because toughness is descended
Also have, preferably the surface from above-mentioned tooth bottom 24 does not make residual ferrite generate till the 0.1mm degree of depth.The plain body of residual iron generates, then because local strength is descended, so it will be got rid of.
Then, the manufacture method to this steering rack 8 describes.By mentioned component is formed and an enforcement milling cutter processing of the side face of the steel bar for steering rack of the present invention of tissue (for example the one-tenth of experimental example 1～19 is grouped into and organizes) having, form par 21, by implementing broaching processing, form the rack tooth formation portion 22 that comprises a plurality of rack tooth 8a in this par 21.Then, in rack tooth formation portion 22, embodiment such as heat-up time 5.5 seconds, behind the high-frequency quenching of 10 seconds cooling times of water-cooled, carry out for example temper under 170 ℃ of conditions of 1.5 hours, thereby realize forming steering rack 8 with Vickers hardness tester 680～800HV on the surface of rack tooth formation portion 22.
In the steering rack 8 that so obtains, as mentioned above, can guarantee wear resistance and necessary flexural strength as necessity of rack tooth 8a.Also have, prevent the propagation of crackle, thereby can prevent that steering rack 8 from breaking is two sections breakage to inside by tempering bainite tissue remaining in (3/4) D portion and tempered martensite.
And, be made as apart from the surface 0.1～1.5mm of tooth bottom 24 by effective case depth the hardened layer 25 of tooth bottom 24, can guarantee the teeth bending strength of rack tooth 8a, and make time spent steering rack 8 whole bending, the steering qualitiess when guaranteeing very of relaxing in big load.Effective case depth d is preferably apart from the surface 0.3～1.2mm of tooth bottom 24.
Below, enumerate embodiment steering rack of the present invention is described more specifically.
Embodiment
Use the steel of C amount 0.53 quality %, Si amount 0.23 quality %, Mn amount 0.8 quality %, S amount 0.018 quality %, Cr amount 0.30 quality %, B amount 0.015 quality %, behind the bar steel of rolling formation diameter 30mm, be heated to 780 ℃, then controlled chilling is to room temperature.Cooled bar steel was finished tempering in 15 minutes by being detained in the stove that is heated to 660 ℃ of atmosphere temperature.Bar steel after the tempering is put cold.More preferably above-mentioned Heating temperature is 820 ℃, and the atmosphere temperature during tempering is 690 ℃.
After the bar steel that so obtains carried out drawing and be processed to form diameter 27.5mm, form par 21, form rack tooth 8a in this par 21, as rack tooth formation portion 22 through machining.Then, carry out 5.5 seconds heat-up times, behind the high-frequency quenching by 10 seconds cooling times of water-cooled, under 170 ℃ of conditions of 1.5 hours, carry out temper, hardened layer 25 is set, manufacture the tooth bar of embodiment in rack tooth formation portion 22 in rack tooth formation portion 22.
In an embodiment, the surface hardness of rack tooth formation portion 22 is 710HV.In the degree of depth (3/4) the D portion 27 apart from the surface of back side portion 26 of rack tooth formation portion 22, the total area percentage of tempering bainite tissue and tempered martensite is 90%, and the regeneration pearlitic structure counts 0% with area percentage.The significant depth d of the hardened layer 25 of the tooth bottom 24 of rack tooth formation portion 22 is the surperficial 0.7mm apart from tooth bottom 24.
Comparative example
Use C amount 0.46 quality %, Si amount 0.19 quality %, Mn amount 0.86 quality %, S amount 0.053 quality %, Cr amount 0.13 quality %, the steel that do not contain B, behind rolling formation bar steel, be heated to 850 ℃, then be cooled to room temperature.Cooled bar steel is finished tempering by being detained more than 30 minutes in the stove that is heated to 610 ℃ of atmosphere temperature.Bar steel after the tempering is put cold.Use the bar steel so obtain, identical with embodiment thereafter, manufacture the steering rack of comparative example.
In comparative example, portion carries out common quenching, tempering in rack tooth formation.The surface hardness of rack tooth is 650HV.In (3/4) D portion, the total area percentage of tempering bainite tissue and tempered martensite is 70%, and the regeneration pearlitic structure counts 20% with area percentage.The significant depth of the hardened layer of tooth bottom is the surperficial 0.3mm apart from the tooth bottom.
Use two these embodiment and comparative example respectively, carried out following test.
The static rupture test of positive input
Use testing apparatus as shown in Figure 5.Steering rack from the steering rack 8 of embodiment to comparative example is inserted the housing 17, respectively anchor post 31 is fixed at the two ends of housing 17.With the fixing steering rack 8 in neutral position, bestow driving torque to shaft pinion 7 from the rotary driver (rotoryactuator) that is connected on the shaft pinion 7.Driving torque is constantly increased, until making its destruction.
Load when be full of cracks takes place in the steering rack, the 305J of embodiment relatively, comparative example is 188J, and the strength at break of embodiment is compared with the strength at break in the comparison, distinguishing has approximately increased by 62%.
The static rupture test of contrary input
Use the testing apparatus that shows as Fig. 6.Steering rack from the steering rack 8 of embodiment to comparative example is inserted the housing 17, respectively anchor post 31 is fixed in by support bar 33 in the two ends of housing 17.Shaft pinion 7 is fixed in the neutral position by universal joint (joint) 34, the end of steering rack 8 is pressed in the load cylinder 35 by measuring cell (load cell), applied load till confirming be full of cracks sound takes place.The output that is connected in the dynamic strain meter 37 of measuring cell 36 is stored in the register 38.
Its result, the relative average 92Nm of the be full of cracks generation load of embodiment, the be full of cracks generation load average out to 51Nm of comparative example compares the strength at break of embodiment with the strength at break of comparative example, and distinguishing has approximately increased by 80%.
The dynamic rupture test of contrary input
Use the testing apparatus that shows as Fig. 7.Steering rack from the steering rack 8 of embodiment to comparative example is inserted the housing 17, the two ends of housing 17 are fixed on the anchor post 39 on a pair of fixed arm 40 of institute's fixed.Housing 17 makes it upwards erect and dispose in end of nearside mutually with shaft pinion 7.Shaft pinion 7 is fixed on the anchor post 41 in the neutral position.Member 42 is fixedly born in end at the steering rack 8 of shaft pinion 7 phase nearsides.
Test-results, relatively average 3 times till Li the destruction, embodiment till destroy average 15 times.Thereby the contrary input shock strength that confirms embodiment is more excellent than comparative example.
Bending strength test
Use testing apparatus as shown in Figure 8.Steering rack from the steering rack 8 of embodiment to comparative example is inserted the housing 17, respectively the two ends of housing 17 are fixed on the anchor post 48.Make steering rack 8 outstanding to greatest extent from the end of the housing 17 that approaches shaft pinion 7, with this state, that is pushed down the front end that is fixed in steering rack 8 by load cylinder 50 by measuring cell 51 bears member 49, applies load till to 8 getable ultimate loads of steering rack.
The output that is connected in the dynamic strain meter 52 of measuring cell 51 is imported ergometer 53, measure load.Its result, maximum is born load, and embodiment is 8.6KN, and comparative example is 7.4KN.Thus, confirming embodiment compares with comparative example and has the flexural strength of about increase by 16%.Also have, confirming both sides all is not " bendings " of fracture.
The positive input long duration test
Use testing apparatus as shown in Figure 9.Steering rack from the steering rack 8 of embodiment to comparative example is inserted the housing 17, respectively anchor post 54 is fixed at the two ends of housing 17.At the two ends of steering rack 8, be connected with servo-actuator (servo actuator) 55 respectively.By universal joint 56 and torque meter 57 rotary driver 58 is connected in shaft pinion 7, rotary driver 58 is bestowed driving torque to shaft pinion 7 thus.By driving torque is 50Nm, and frequency is 0.1～0.2Hz, carries out repeatedly 30,000 times.
After test is finished, measure abrasion loss to the engagement part of pinion(gear), the average 8.7 μ m of relative embodiment, comparative example average out to 27.8 μ m, thus confirm that embodiment compares the abrasion loss of minimizing about 70% with comparative example.
Contrary input long duration test
Use testing apparatus as shown in figure 10.Steering rack from the steering rack 8 of embodiment to comparative example is inserted the housing 17, respectively the two ends of housing 17 are fixed on the anchor post 59.Shaft pinion 7 is fixed in the neutral position by universal joint 60, and the drag link 9 of the end of the tooth sector 8 by being connected in shaft pinion 7 close sides is to the steering rack 8 bearing axle power from servo-actuator 61.The axle power that is carried on steering rack 8 is 9.8kN, is that 5Hz carries out till breakage with the frequency.Its result, till the relatively routine breakage 350,000 times, embodiment does not have breakage until 700,000 times yet.
Fatigue-bending test
Make the test film 62 shown in Figure 11 A by the starting material identical with embodiment.Test film 62 is the roughly round axle of total length 90mm.With an end 62a of distance test film 62 be that the position of 40mm is the center apart from N, form the necking part 65 of section bending with R5.The minimum diameter R of necking part 65 is 8mm.Clamp necking part 65 1 end 62a sides and become the cylindrical portion 62 that diameter P is 12mm.Also have, clamp necking part 65 the other end 62b sides form 1/20 taper with this hole enlargement along with the 62b side of the other end tapered portion 64.The maximum diameter Q of tapered portion 64 is 14mm.Comparative example is also made identical comparison test sheet.
Testing apparatus shown in use Figure 11 B has carried out the crooked fatigue experiment from test film 62 to the comparison test sheet.Make apart from an end 62a of test film 62 and give prominence to cantilever-shaped for the part till 50mm,, residue tapered portion 64 is fixed in the taper supported hole 67 of anchor post 66 with this state apart from M.By near the rotating roller 68 the end 62a of the test film 62 that is fixed, with frequency 20Hz repeated loading load, measure the stress and the number of occurrence by load cylinder 69, obtain the S-N curve.
The result of test, in the smooth (stress constriction) of S-N curve, the stress 1270MPa of relatively routine test film, the stress of test film 62 are 1450MPa, thereby confirm that fatigue resistance has approximately improved 15%.
Claims (12)
1. steel bar for steering rack, it is characterized in that, contain the Al of Ti, 0.0005～0.1 quality % of B, 0.005～0.05 quality % of Mn, 0.0005～0.003 quality % of Si, 0.2～1.5 quality % of C, 0.05～0.5 quality % of 0.50～0.60 quality % and the N of 0.002～0.02 quality %
When the diameter of establishing bar steel was D, the quenching/tempered structure apart from the part of case depth D/4 of bar steel was adjusted to and satisfies following I), II) and condition III),
I) area percentage of the total of tempering bainite tissue and tempered martensite is 30～100%;
II) area percentage of regeneration pearlitic structure is 0～50%;
III) area percentage of the total of tempering bainite tissue, tempered martensite and regeneration pearlitic structure is 50～100%.
2. according to the described steel bar for steering rack of claim 1, it is characterized in that it is following and do not comprise the Cr of 0 quality % to contain 1.5 quality %.
3. according to the described steel bar for steering rack of claim 1, it is characterized in that, also contain from following optional at least a,
S:0.06 quality % is following and not contain 0 quality %, Pb:0.3 quality % following and not contain 0 quality %, Bi:0.2 quality % following and not contain 0 quality %, Te:0.1 quality % following and not contain 0 quality %, Mg:0.01 quality % following and not contain 0 quality %, Ca:0.01 quality % following and do not contain 0 quality %, rare earth element: 0.01 quality % is following and not contain 0 quality %, Zr:0.3 quality % following and do not contain 0 quality %.
4. the manufacture method of a steel bar for steering rack, it is characterized in that, the rolling steel disc that contains following composition, C:0.50～0.60 quality %, Si:0.05～0.5 quality %, Mn:0.2～1.5 quality %, B:0.0005～0.003 quality %, Ti:0.005～0.05 quality %, Al:0.0005～0.1 quality % and N:0.002～0.02 quality %
Bar steel by rolling gained is quenched more than 780 ℃ from temperature, make the area percentage apart from the total of the bainite structure of the part of case depth D/4 and martensitic stucture of bar steel be 30～100% after,
Put into the stove of the atmosphere temperature that is heated to 660～720 ℃ of temperature, carry out the short period of time temper below 20 minutes, be cooled to room temperature, thus, making the area percentage apart from the regeneration pearlitic structure of the part of case depth D/4 of above-mentioned bar steel is 0～50%, and making the area percentage of total of the tempering bainite tissue apart from the part of case depth D/4, tempered martensite and the regeneration pearlitic structure of above-mentioned bar steel is 50～100%
Wherein, D represents the diameter of bar steel.
5. the manufacture method of steel bar for steering rack according to claim 4 is characterized in that, above-mentioned steel disc contains below the 1.5 quality % and do not contain the Cr of 0 quality %.
6. the manufacture method of steel bar for steering rack according to claim 4 is characterized in that, above-mentioned steel disc also contains following choose wantonly out at least a,
S:0.06 quality % is following and not contain 0 quality %, Pb:0.3 quality % following and not contain 0 quality %, Bi:0.2 quality % following and not contain 0 quality %, Te:0.1 quality % following and not contain 0 quality %, Mg:0.01 quality % following and not contain 0 quality %, Ca:0.01 quality % following and do not contain 0 quality %, rare earth element: 0.01 quality % is following and not contain 0 quality %, Zr:0.3 quality % following and do not contain 0 quality %.
7. a steering rack is characterized in that, uses claim 1,2 or 3 described steel bar for steering rack and forms.
8. steering rack according to claim 7 is characterized in that,
Have: main body and be formed at side face local of aforementioned body and contain the rack tooth formation portion of a plurality of rack tooths,
At least be provided with the hardened layer that has been carried out high-frequency quenching processing and temper and has obtained in rack tooth formation portion;
The surface hardness of above-mentioned rack tooth formation portion is counted 680～800HV with Vickers' hardness.
9. steering rack according to claim 8 is characterized in that,
Aforementioned body contains radially with the part of rack tooth formation portion subtend with apart from being the part of 3/4D with the degree of depth of the part surface of above-mentioned rack tooth formation portion subtend radially;
Quenching/the tempered structure of the part of above-mentioned degree of depth 3/4D is adjusted into and satisfies following I), II) and condition III),
I) area percentage of the total of tempering bainite tissue and tempered martensite is 30～100%;
II) area percentage of regeneration pearlitic structure is 0～50%;
III) area percentage of the total of tempering bainite tissue, tempered martensite and regeneration pearlitic structure is 50～100%,
Wherein, D represents the diameter of bar steel.
10. steering rack according to claim 8 is characterized in that,
The tooth bottom is contained in above-mentioned rack tooth formation portion;
The effective case depth of above-mentioned tooth bottom is the surface 0.1～1.5mm apart from the tooth bottom.
11. steering rack according to claim 8 is characterized in that,
The tooth bottom is contained in above-mentioned rack tooth formation portion;
The effective case depth of above-mentioned tooth bottom is the surface 0.3～1.2mm apart from the tooth bottom.
12. steering rack according to claim 8 is characterized in that,
The tooth bottom is contained in above-mentioned rack tooth formation portion;
Residual ferrite is not contained in zone till the degree of depth of the surperficial 0.1mm bottom above-mentioned tooth.
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| JP148906/2003 | 2003-05-27 | ||
| JP2003148906A JP4197459B2 (en) | 2003-05-27 | 2003-05-27 | Steel bar for steering rack |
| JP157029/2003 | 2003-06-02 |
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| CN1791696A true CN1791696A (en) | 2006-06-21 |
| CN100419107C CN100419107C (en) | 2008-09-17 |
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| CNB200480013699XA Expired - Fee Related CN100419107C (en) | 2003-05-27 | 2004-05-27 | Steel bar for steering rack, method for producing the same, and steering rack using the same |
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| CN (1) | CN100419107C (en) |
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|---|---|---|---|---|
| JPH108189A (en) * | 1996-06-14 | 1998-01-13 | Daido Steel Co Ltd | Steel for induction hardening excellent in bendability and induction hardened part excellent in bendability using the same steel |
| CA2295881C (en) * | 1997-07-28 | 2005-10-18 | Nippon Steel Corporation | Method for producing ultra-high strength, weldable steels with superior toughness |
| JP2001026836A (en) * | 1999-07-13 | 2001-01-30 | Daido Steel Co Ltd | Steel for induction hardening and parts for machine structure excellent in cold workability, rolling fatigue strength and twisting fatigue strength |
-
2003
- 2003-05-27 JP JP2003148906A patent/JP4197459B2/en not_active Expired - Fee Related
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2004
- 2004-05-27 CN CNB200480013699XA patent/CN100419107C/en not_active Expired - Fee Related
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| CN103562423A (en) * | 2011-05-25 | 2014-02-05 | 株式会社神户制钢所 | Steel with excellent rolling fatigue characteristics |
| CN102392193A (en) * | 2011-11-10 | 2012-03-28 | 舞阳钢铁有限责任公司 | Extra thick quenched and tempered steel plate for ocean platform tooth bar and production method thereof |
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| US9976206B2 (en) | 2013-08-26 | 2018-05-22 | Nippon Steel & Sumitomo Metal Corporation | Rolled round steel material for steering rack bar, and steering rack bar |
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| CN105939919A (en) * | 2014-01-22 | 2016-09-14 | 日本精工株式会社 | Steering rack and method for manufacturing same |
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| US11021184B2 (en) | 2014-01-22 | 2021-06-01 | Nsk Ltd. | Steering rack and method for manufacturing the same |
| CN106048426A (en) * | 2015-04-14 | 2016-10-26 | 现代自动车株式会社 | Carbon steel composition for reduced thermal strain steering rack bar and method for manufacturing the same |
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| CN105002418A (en) * | 2015-07-23 | 2015-10-28 | 柳州市众力金铭热处理有限公司 | 45 wear-resistant steel rod matched with quartz sand rod mill |
| CN108001518A (en) * | 2017-12-25 | 2018-05-08 | 重庆耐世特转向系统有限公司 | Axis processing technique among automobile steering system high density tooth |
| CN108165890A (en) * | 2018-01-09 | 2018-06-15 | 北京科技大学 | A kind of preparation method of low-cost high-strength nanometer bainite abrasion-proof steel ball |
| CN111187994A (en) * | 2020-02-17 | 2020-05-22 | 本钢板材股份有限公司 | Steel C60 hot-rolled coil for high-C cutter and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100419107C (en) | 2008-09-17 |
| JP2004353005A (en) | 2004-12-16 |
| JP4197459B2 (en) | 2008-12-17 |
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