CN115747639A - Bainite non-quenched and tempered steel material, steering knuckle and preparation method - Google Patents
Bainite non-quenched and tempered steel material, steering knuckle and preparation method Download PDFInfo
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- CN115747639A CN115747639A CN202211333639.2A CN202211333639A CN115747639A CN 115747639 A CN115747639 A CN 115747639A CN 202211333639 A CN202211333639 A CN 202211333639A CN 115747639 A CN115747639 A CN 115747639A
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Abstract
A bainite non-quenched and tempered steel material, a steering knuckle and a preparation method relate to the technical field of non-quenched and tempered steel materials, and further improve the toughness of the automobile steering knuckle. The material comprises the following components in percentage by weight: c:0.33 to 0.37%, si: 0.15-0.35%, mn: 1.9-2.05%, P is less than or equal to 0.03%, S: 0.04-0.07%, cr:0.20% -0.50%, V:0.20 to 0.30 percent. The preparation process comprises the following steps: s1, smelting in an electric furnace; s2, refining in an LF (ladle furnace); s3, carrying out VD vacuum treatment S4 and casting ingots; s5, heat treatment; s6, rolling; s7, air cooling; s8, finishing; and S9, flaw detection. The steering knuckle preparation method comprises the following steps: t1, blanking; t2, induction heating; t3, primary forging; t4, intermediate forging; t5, finish forging; t6, trimming; and T7, forcibly cooling by a fan.
Description
Technical Field
The invention relates to the technical field of non-tempered steel materials, in particular to a bainite non-quenched and tempered steel material, a steering knuckle and a preparation method.
Background
The automobile steering knuckle is one of important safety parts on an automobile chassis, not only bears double tasks of steering and bearing, but also bears loads generated by impact from the ground, wheel sideslip steering brake and the like, and meanwhile, the automobile steering knuckle is also an important assembly part, a main pin hole of the automobile steering knuckle is connected and matched with the left end and the right end of a front axle through pins, and the shaft diameter of the main pin hole is connected and matched with a front wheel through an inner bearing, an outer bearing, a hub and the like, so that the front wheel of an automobile in the process of running can fly out due to failure and fracture of the automobile steering knuckle, and serious consequences can be caused. Therefore, the knuckle material is required to have high toughness.
At present, the traditional material of the heavy commercial vehicle steering knuckle is medium carbon alloy structural steel such as 40MnB or 40Cr, the medium carbon alloy structural steel is used after quenching and tempering treatment, and the hardness is generally required to be 255 HBW-302 HBW. The shaft neck can be subjected to induction quenching treatment, and certain effective hardening layer depth and surface hardness are required, wherein the effective hardening layer depth is 3-8 mm, and the surface hardness is 50-63 HRC; or may not be subjected to induction hardening treatment. The hardening and tempering process of the parts consumes a large amount of energy, so that the cost of the steering knuckle is increased; if the quenching and tempering are improper, the problems of part deformation, cracking and the like can also occur.
As the material of the steering knuckle requires very high toughness, the prior art has no case of applying non-quenched and tempered steel material to the steering knuckle of a heavy commercial vehicle.
Disclosure of Invention
In order to further improve the obdurability of the automobile steering knuckle, the invention provides a bainite non-quenched and tempered steel material, the steering knuckle and a preparation method.
The technical scheme of the invention is as follows:
a bainite non-quenched and tempered steel material comprises the following components in percentage by weight: c:0.33% -0.37%, si: 0.15-0.35%, mn: 1.9-2.05%, P is less than or equal to 0.03%, S: 0.04-0.07%, cr:0.20% -0.50%, V:0.20 to 0.30 percent.
Preferably, the bainite non-quenched and tempered steel material has a carbon equivalent Ceq value of 0.82-0.92% and Ceq = C + (1/10) Si + (2/11) Mn + (1/5) Cr + (1/3) V, wherein C, si, mn, cr and V represent mass percentages of corresponding elements in the bainite non-quenched and tempered steel material.
Preferably, the tensile strength of the bainite non-quenched and tempered steel material is 900MPa to 1050MPa, the non-proportional elongation strength is 700MPa to 800MPa, the elongation at break is 13 percent to 18 percent, and the reduction of area is 38 percent to 50 percent.
Preferably, the metallographic structure of the bainite non-quenched and tempered steel material is a mixed structure of bainite and an island-shaped structure.
Preferably, the island-like structure is a mixed structure of martensite, pearlite, or retained austenite, into which the carbon-rich austenite region is transformed during cooling.
A method of producing a non heat treated steel bainitic material as defined above, the method comprising the steps of making the non heat treated steel with the composition of the non heat treated steel bainitic material as a controlling factor for the process steps, the process steps comprising:
s1, smelting in an electric furnace;
s2, LF refining;
s3, performing VD vacuum treatment;
s4, ingot casting;
s5, heat treatment;
s6, rolling;
s7, air cooling;
s8, finishing;
and S9, flaw detection.
A bainite non-quenched and tempered steel steering knuckle is prepared from the bainite non-quenched and tempered steel material serving as a raw material.
The preparation method of the bainite non-quenched and tempered steel knuckle comprises the following steps:
t1, blanking;
t2, induction heating;
t3, primary forging;
t4, medium forging;
t5, finish forging;
t6, trimming;
and T7, forcibly cooling by a fan.
Preferably, the temperature of the induction heating is 1160-1220 ℃; the temperature of the initial forging is 1100-1160 ℃; the temperature of the finish forging is 1000-1060 ℃.
Preferably, the cooling rate in the range from the finish forging temperature to 670 ℃ is controlled to be 1.0 ℃/S to 1.5 ℃/S.
Compared with the prior art, the invention has the following specific beneficial effects:
1. the invention considers the factors of cost and performance, adopts the chemical composition design idea of taking lower medium carbon, higher manganese and higher vanadium as microalloying elements, has less component design elements and is assisted with the idea of controlling carbon equivalent (Ceq), so that the part forms a mixed structure form which takes medium carbon bainite in various forms as a main part and a small amount of island-shaped structures after the cooling control process is implemented, the cutting processing is easy, the medium temperature tempering process which is usually necessary to use for medium carbon bainite steel is omitted, and the energy and the manufacturing cost are saved;
2. the material can be applied to the preparation of heavy commercial vehicle steering knuckles, the tensile strength of the material reaches 900-1100 MPa, and the performance index of the steering knuckle part reaches and exceeds the performance level of medium carbon alloy structural steel tempering through a suitable post-forging controlled cooling process, so that the service performance requirement is met.
3. A series of quality problems generated in the quenching and tempering heat treatment process, such as scrapping caused by factors of cracking, unqualified hardness, uneven hardness, deformation and the like, are avoided, and the investment of a new production line is reduced.
Drawings
FIG. 1 is a schematic diagram of upper bainite in a transmission electron microscope cooled by a fan according to the present invention;
FIG. 2 is a schematic diagram of the lower bainite in a transmission electron microscope cooled by fan forced cooling of the material of the present invention;
FIG. 3 is a schematic view of the pearlite in the transmission electron mirror with fan forced cooling of the material of the present invention.
Detailed Description
In order to make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the specification of the present invention, and it should be noted that the following embodiments are only used for better understanding of the technical solutions of the present invention, and should not be construed as limiting the present invention.
Example 1.
The embodiment provides a bainite non-quenched and tempered steel material which comprises the following chemical components in percentage by weight: c:0.35%, si:0.21%, mn:2.04%, P:0.011%, S:0.053%, cr:0.25%, V:0.25%, and a Ceq value of 0.88.
The induction heating temperature in the manufacturing process of the steering knuckle manufactured by applying the non-modulated steel material is as follows: 1160 to 1220 ℃; initial forging temperature: 1100 to 1160 ℃; finish forging temperature: 1000-1060 ℃, the cooling mode is forced cooling by a fan, and the cooling speed between the finish forging temperature and 670 ℃ is 1.0-1.5 ℃/S. The metallographic structure of the material is a mixed structure of bainite and an island-shaped structure, and the island-shaped structure is a mixed structure of martensite, pearlite or retained austenite converted from a carbon-rich austenite region in a cooling process.
The mechanical properties of the steering knuckle are tested as follows: tensile strength: 1010MPa, rp0.2 non-proportional elongation strength: 785MPa, elongation at break: 14%, reduction of area: 40 percent.
Example 2.
The embodiment provides bainite non-quenched and tempered steel which comprises the following chemical components in percentage by weight: c:0.35%, si:0.16%, mn:2.00%, P: less than or equal to 0.03%, S:0.055%, cr:0.26%, V:0.26%, and a Ceq value of 0.86.
The induction heating temperature in the manufacturing process of the steering knuckle manufactured by applying the non-modulated steel material is as follows: 1160 to 1220 ℃; initial forging temperature: 1100 to 1160 ℃; finish forging temperature: 1000-1060 ℃, the cooling mode is forced cooling by a fan, and the cooling speed between the finish forging temperature and 670 ℃ is 1.0-1.5 ℃/S. The metallographic structure of the material is a mixed structure of bainite and an island-shaped structure, and the island-shaped structure is a mixed structure of martensite, pearlite or retained austenite converted from a carbon-rich austenite region in a cooling process.
The mechanical properties of the steering knuckle are tested as follows: tensile strength: 990MPa, rp0.2 non-proportional elongation strength: 765MPa, elongation at break: 15.5%, reduction of area: 42 percent.
Example 3.
The embodiment provides bainite non-quenched and tempered steel which comprises the following chemical components in percentage by weight: c:0.33%, si:0.18%, mn:2.01%, P:0.006%, S0.049%, cr 0.24%, V0.24%, and Ceq 0.84.
The induction heating temperature in the manufacturing process of the steering knuckle manufactured by applying the non-modulated steel material is as follows: 1160 to 1220 ℃; the initial forging temperature is as follows: 1100 to 1160 ℃; the finish forging temperature is as follows: 1000-1060 ℃, the cooling mode is forced cooling by a fan, and the cooling speed in the temperature range from the finish forging temperature to 670 ℃ is as follows: 1.0-1.5 ℃/S. The metallographic structure of the material is a mixed structure of bainite and an island-shaped structure, and the island-shaped structure is a mixed structure of martensite, pearlite or retained austenite converted from a carbon-rich austenite region in a cooling process.
The normal-temperature microstructure form of the forged steering knuckle is as follows: a mixed structure mainly composed of bainite.
The mechanical properties are as follows: tensile strength: 960MPa, rp0.2 non-proportional elongation strength: 735MPa, elongation at break: 16.0%, reduction of area: 43.5 percent.
Example 4.
The embodiment provides bainite non-quenched and tempered steel which comprises the following chemical components in percentage by weight: c:0.36%, si:0.19%, mn:1.98%, P:0.009%, S0.06%, cr 0.24%, V0.27%, and Ceq 0.87.
The induction heating temperature in the manufacturing process of the steering knuckle manufactured by applying the non-modulated steel material is as follows: 1160 to 1220 ℃; initial forging temperature: 1100 to 1160 ℃; finish forging temperature: 1000-1060 ℃, the cooling mode is forced cooling by a fan, and the cooling speed between the finish forging temperature and 670 ℃ is 1.0-1.5 ℃/S. The metallurgical structure of the forged steering knuckle is a mixed structure mainly comprising bainite. The mechanical properties are as follows: tensile strength: 1000mpa, rp0.2 non-proportional elongation: 755MPa, elongation at break: 14.5%, reduction of area: and 43 percent.
More black island structures are distributed in the bainite matrix of the non-modulated steel material, and the non-modulated steel material is a carbon-rich structure with higher microhardness. The transmission electron microscope image of the non-modulated steel material structure after forced cooling by the fan is shown in the attached drawing, so that a large amount of upper and lower bainite structures can be clearly seen, the upper bainite structure is abundant, and the lower bainite structure also has a certain content. Upper bainite ferrite and carbide in upper bainite are alternately arranged in a sheet shape, strip-shaped Bainite Ferrite (BF) grows from an austenite crystal boundary to an inner crystal in parallel, and discontinuous short rod-shaped cementite is arranged between adjacent ferrite strips, as shown in figure 1; the lower bainite is irregularly crossed strips, the strips are supersaturated alpha ferrite, carbides are arranged in the bainite ferrite strips, the carbides and a BF main shaft form an angle of 45-55 degrees, and intermittent carbides are also distributed among the ferrite strips, as shown in figure 2. A small amount of pearlite is present in the sample near the core of the journal, as shown in fig. 3, due to the slow heat dissipation from the core, the higher temperature, and the transformation of super-cooled austenite to pearlite.
The bending fatigue properties of the 40Cr and the non-quenched and tempered steel sample prepared in the embodiment are respectively tested, a metal rotating bending fatigue test method GB/T4337-2008 is adopted, and the notch coefficient Kt =1.86. The fatigue limit of the notch sample is 225.0MPa and 235MPa respectively, the fatigue limit of the notch sample is equivalent to that of the notch sample, and even the sample prepared by the embodiment has better fatigue resistance.
Bench test verification was performed on the 40Cr knuckle and the non-quenched and tempered steel knuckle prepared in this example:
the test is carried out under the condition of atmospheric room temperature by using an Instron1346 type electro-hydraulic servo material testing machine, load control is adopted, the loading frequency f =7.6Hz, the stress ratio is 0.1, the load is in a sine wave shape, and the cycle frequency of 1, 000 and 000 is taken as the passing frequency of a part fatigue test. The test result shows that the fatigue load of the material is 170KN, the 40Cr steering knuckle is 160KN, and the non-quenched and tempered steel steering knuckle prepared by the embodiment has better fatigue resistance.
The following tests for user use of the non-quenched and tempered steel knuckle according to the embodiment were carried out:
two sets of the non-modulation steel steering knuckles of the embodiment are assembled to a double front axle, and a user use test is carried out, wherein the test driving road condition is as follows: the mining area, the gravel road and the mountain trails are all sand and stone pavements. The vehicle type information is as follows:
the vehicle type CA3312 dumper is provided with a double front axle and a rated load of 31 tons;
by 11, 16 days in 2011, the mileage of the two users using the test vehicle is shown in the following table.
| Vehicle model | Date of assembly | Counting date | Mileage (kilometer) |
| CA3312 | 2020-11-2 | 2021-11-16 | 137485 |
After the practical verification, the steering knuckle can still be normally used after about one year, and has good fatigue resistance.
Claims (10)
1. A bainite non-quenched and tempered steel material is characterized by comprising the following components in percentage by weight: c:0.33 to 0.37%, si: 0.15-0.35%, mn: 1.9-2.05%, P is less than or equal to 0.03%, S: 0.04-0.07%, cr:0.20% -0.50%, V:0.20 to 0.30 percent.
2. A bainitic non-heat-treated steel material according to claim 1, characterized in that it has a Ceq value of 0.82% to 0.92% and Ceq = C + (1/10) Si + (2/11) Mn + (1/5) Cr + (1/3) V, where C, si, mn, cr and V represent the mass percentages of the respective elements in the bainitic non-heat-treated steel material.
3. The non-quenched and tempered steel bainite material as claimed in claim 1, wherein the non-quenched and tempered steel bainite material has a tensile strength of 900 to 1050MPa, a non-proportional elongation of 700 to 800MPa, an elongation at break of 13 to 18%, and a reduction of area of 38 to 50%.
4. A bainite non-heat-treated steel material according to claim 1, wherein the metallographic structure of the bainite non-heat-treated steel material is a mixed structure of bainite and an island-like structure.
5. A bainitic non-quenched and tempered steel material according to claim 4, characterized in that the island-like structure is a mixed structure of martensite, pearlite, or retained austenite into which the carbon-rich austenite region is transformed during cooling.
6. A method of manufacturing a non heat treated steel material of bainite according to any one of claims 1 to 5, including the manufacture of non heat treated steel with the composition of the non heat treated steel material as a controlling factor for the process steps, which in particular include:
s1, smelting in an electric furnace;
s2, refining in an LF (ladle furnace);
s3, performing VD vacuum treatment;
s4, casting ingots;
s5, heat treatment;
s6, rolling;
s7, air cooling;
s8, finishing;
and S9, flaw detection.
7. A bainite non-quenched and tempered steel knuckle, characterized by being prepared from the bainite non-quenched and tempered steel material according to any one of claims 1 to 5 as a raw material.
8. A method of making a bainite non-hardened and tempered steel knuckle according to claim 7, comprising the steps of:
t1, blanking;
t2, induction heating;
t3, primary forging;
t4, medium forging;
t5, finish forging;
t6, trimming;
and T7, forcibly cooling by a fan.
9. The method for producing a bainite non-quenched and tempered steel knuckle according to claim 8, wherein the temperature of the induction heating is 1160 to 1220 ℃; the temperature of the initial forging is 1100-1160 ℃; the temperature of the finish forging is 1000-1060 ℃.
10. The method of manufacturing a bainite non-quenched and tempered steel knuckle according to claim 8, wherein a cooling rate in a range from the finish forging temperature to 670 ℃ is controlled to 1.0 ℃/S to 1.5 ℃/S.
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Citations (4)
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|---|---|---|---|---|
| CN1477226A (en) * | 2003-08-01 | 2004-02-25 | 清华大学 | Medium-low carbon manganese system self-hardening bainite steel |
| CN104651753A (en) * | 2014-11-28 | 2015-05-27 | 南京钢铁股份有限公司 | Non-quenched and tempered steel for heavy truck balance shaft and manufacturing method thereof |
| CN108103395A (en) * | 2017-11-17 | 2018-06-01 | 徐工集团工程机械有限公司 | A kind of non-hardened and tempered steel thrust wheel and preparation method thereof |
| CN115491605A (en) * | 2022-09-27 | 2022-12-20 | 东风商用车有限公司 | Bainite steel for hot forging, process, device and system for manufacturing hot forged parts |
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- 2022-10-28 CN CN202211333639.2A patent/CN115747639A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1477226A (en) * | 2003-08-01 | 2004-02-25 | 清华大学 | Medium-low carbon manganese system self-hardening bainite steel |
| CN104651753A (en) * | 2014-11-28 | 2015-05-27 | 南京钢铁股份有限公司 | Non-quenched and tempered steel for heavy truck balance shaft and manufacturing method thereof |
| CN108103395A (en) * | 2017-11-17 | 2018-06-01 | 徐工集团工程机械有限公司 | A kind of non-hardened and tempered steel thrust wheel and preparation method thereof |
| CN115491605A (en) * | 2022-09-27 | 2022-12-20 | 东风商用车有限公司 | Bainite steel for hot forging, process, device and system for manufacturing hot forged parts |
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