CN114293098A - High-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forge piece - Google Patents
High-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forge piece Download PDFInfo
- Publication number
- CN114293098A CN114293098A CN202111440389.8A CN202111440389A CN114293098A CN 114293098 A CN114293098 A CN 114293098A CN 202111440389 A CN202111440389 A CN 202111440389A CN 114293098 A CN114293098 A CN 114293098A
- Authority
- CN
- China
- Prior art keywords
- quenched
- steel
- tempered steel
- percent
- strength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
The invention discloses novel high-strength and high-toughness bainite type non-quenched and tempered steel which comprises the following components in percentage by mass: 0.16 to 0.25 percent of C; 0.40 to 0.70 percent of Si; mn 2.00% -2.90%; p is less than or equal to 0.015 percent; 0.015-0.065% of S; 0.10 to 0.30 percent of Cr; v0.020% -0.080%; 0.015-0.050% of Ti; b0.0005 to 0.0025; 0.015 to 0.035 percent of Al; 0.004-0.006% of N; the balance of iron and inevitable impurities. The non-quenched and tempered steel can obtain a bainite structure in a wider cooling speed range; the cheap Mn, B and other alloy elements are utilized, no precious alloy elements are used, and the cost is low; the tempering process is omitted in the preparation process, and air is blown to cool to room temperature after forging, so that the production cost is further reduced, the production period is shortened, and the energy is saved and the environment is protected; compared with the prior ferrite and pearlite type non-quenched and tempered steel, the steel has the advantages of high strength, good plasticity and toughness and the like, and can be used for replacing the quenched and tempered steel to produce large-size automobile steering knuckles and other safety parts with the diameter of more than 50 mm.
Description
Technical Field
The invention relates to the field of alloy steel, in particular to high-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forgings.
Background
Compared with quenched and tempered steel, the non-quenched and tempered steel forging omits the production processes of quenching, high-temperature tempering (quenching and tempering), straightening and the like, simplifies the production process flow, saves energy, reduces the manufacturing cost, and has good environmental protection effect, thereby being more and more widely applied to the mechanical manufacturing industries of automobiles, tractors, standard parts, petroleum and the like. At present, the most used non-quenched and tempered steel is mainly ferrite + pearlite type non-quenched and tempered steel, but the strength level of the steel is usually below 1000MPa, and the plasticity and toughness are also poor, so the steel is usually applied to parts such as crankshafts, connecting rods and the like with low requirements on toughness. In order to meet the higher requirements of safety parts such as steering knuckles, front axles and the like on the toughness of steel, research and development of bainite type non-quenched and tempered steel with good toughness matching are carried out at home and abroad in recent years.
Since a bainite-based non-heat-treated steel forging has a structure mainly composed of bainite by controlling the cooling rate after forging, it is desired to obtain a bainite structure in a wide cooling rate range. The bainite type non-quenched and tempered steel developed at present, such as 25Mn2CrVS, 12Mn2VBS and the like, is difficult to meet the requirements of large-specification forgings such as commercial vehicle steering knuckles and the like, because the hardenability of the 25Mn2CrVS steel is insufficient, when the size of the forgings is large, such as the diameter is larger than 50mm, more pro-eutectoid ferrite exists in the forging structures, and the strength and the toughness of the steel are deteriorated; for 12Mn2VBS steel, although the steel has better hardenability and toughness, the strength level is lower (the tensile strength is less than 850MPa) due to the lower carbon content, so that the requirement on the mechanical property of forgings such as large-specification steering knuckles is difficult to meet.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide novel high-hardenability and high-toughness bainite type non-quenched and tempered steel which can be used for manufacturing safety parts such as commercial vehicle steering knuckles with the diameter of 50mm and above.
The technical scheme is as follows: the invention relates to high-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forgings, which comprises the following components in percentage by mass: 0.16 to 0.25 percent of C; 0.40 to 0.70 percent of Si; mn 2.00% -2.90%; b0.0005 to 0.0025; p is less than or equal to 0.015 percent; 0.015-0.065% of S; 0.10 to 0.30 percent of Cr; v0.020% -0.080%; 0.015-0.050% of Ti; 0.015 to 0.035 percent of Al; 0.004-0.006% of N; the balance of iron and inevitable impurities.
The function and the proportion of each element in the technical scheme of the invention are as follows:
c: in order to obtain the required strength level after forging and controlled cooling, the content of C in the steel is required to be more than 0.16 percent; however, increasing the C content greatly impairs the plasticity, toughness, ductile-brittle transition temperature, cold workability, etc. of the steel. Therefore, the C content should be controlled below 0.25%.
Si: si is a commonly used deoxidizer in steel, has a high solid solution strengthening effect, and can shift the C curve to the right by Si element, so that the hardenability of the steel is improved. The Si content is too low, so that the effect is weak; however, the Si content is too high, so that the plasticity and the toughness of the steel are low, the decarburization sensitivity of the steel is increased, and the fatigue property of the forged piece is deteriorated. Therefore, the content of Si is controlled to be 0.40-0.70%.
Mn: mn is an effective element for deoxidation and desulfurization in steel, can also improve the hardenability and strength of the steel, and is the most effective cheap alloy element for forming a Babyite structure. When the carbon content is constant, the Mn content is increased, the bainite content in the steel is increased, and the effect is more obvious particularly under the condition of low cooling speed. However, too high Mn content leads to too high residual austenite content after deformation and too low bainite transformation temperature, which results in too low yield strength of the steel and tends to increase unevenness of the structure. Therefore, the Mn content is controlled to be 2.00-2.90%.
P: p can form micro segregation when molten steel is solidified, and then is partially gathered at a grain boundary when the molten steel is heated at high temperature, so that the brittleness of the steel is obviously increased. In addition, the reduction of the P content reduces the deformation resistance of the steel, so that the P content is controlled to be less than 0.015%.
S: since the improvement of the strength of the steel material deteriorates the machinability, the addition of an appropriate amount of S element in combination with Mn forms MnS inclusions which are advantageous in the machinability, and the machinability of the bainite type non-heat-treated steel can be remarkably improved. Therefore, the S content is controlled to be 0.015-0.065%.
Cr: cr can effectively improve the hardenability of steel, greatly reduce the bainite transformation starting point, obtain a certain amount of bainite in the air cooling process, and simultaneously prevent cracking caused by too fast cooling speed. However, since too high a content deteriorates the toughness of steel and increases the cost of steel, the Cr content is controlled to 0.10 to 0.30%.
V: v belongs to a strong carbonitride forming element, is easy to form a fine V (C, N) precipitated phase with C, N in steel, refines austenite grains in the forging and heating process, and further refines the bainite structure after phase transformation. Considering that the V content is too high, the cost is increased, the precipitation of proeutectoid ferrite is easily promoted, and the strength of steel is reduced, the V content is controlled to be 0.020-0.080%.
Ti: the effect is similar to that of V, and the Ti (C, N) formed by C, N elements in the steel has good grain refining effect. Due to the lower bainite transformation temperature, the precipitation strengthening effect of Ti (C, N) is limited. In the invention, Ti mainly plays the roles of inhibiting austenite grains from growing large, refining bainite tissues and fixing nitrogen in the forging and heating process. Too high Ti content tends to produce coarse TiN particles precipitated in liquid state, deteriorating the fatigue properties of the steel. Therefore, the content is controlled to be 0.015 to 0.050%.
B: b can remarkably improve hardenability of steel, delay ferrite and pearlite transformation, and can obtain a bainite structure in a considerably large cooling rate range. The content of B is too high, so that the steel is easy to generate boron brittleness, and the hot working performance is influenced. Therefore, the content of B is controlled to be 0.0005 to 0.0025%.
N: n forms carbonitrides and nitrides such as V (N, C), TiN, AlN and the like with V, Ti, Al and the like, and mainly plays roles of grain refinement and precipitation strengthening effect enhancement in bainite type non-quenched and tempered steel, but too high content of N reduces ductility and toughness of the steel. Therefore, the content of N is controlled to be 0.004-0.006%.
Al: al is the main deoxidizing element in steel. In addition, AlN formed by Al and N can effectively prevent austenite grains from being coarsened, further refine a bainite structure and improve the toughness of the steel. Too high Al content tends to increase the content of oxide inclusions in the steel, affecting the fatigue properties and workability of the steel. Therefore, the Al content is controlled to be 0.015-0.035%.
Further, the mass percentages of Mn and B elements satisfy the relation: mn (%) is more than or equal to 2.40 and B (%) +100B (%) is less than or equal to 3.00; wherein Mn (%), B (%) represent the mass percentages of Mn and B, respectively. λ ═ Mn (%) +100B (%). When the lambda value is less than 2.40, although the contents of the individual Mn or B elements may be both in the above-described most suitable range, it is difficult to obtain a sufficient bainite structure, thereby obtaining an excellent strength, plasticity, and toughness combination; when the lambda value is more than 3.00, the hardenability is too high, and the steel tends to have a large martensite structure, which deteriorates the plasticity and toughness of the steel.
Further, in order to obtain a fine bainite structure and further obtain excellent mechanical properties, particularly plasticity and toughness, it has been found through a large number of studies and analyses that, unlike ferrite + pearlite-type non-quenched and tempered steel, most (90% or more) of V elements of the bainitic-type non-quenched and tempered steel are in solid solution and almost all of Ti elements are in carbonitride M (C, N) due to a low transformation temperature. In contrast, V + Ti is adopted for composite micro-alloying, so that on one hand, a proper amount of undissolved Ti-rich M (C, N) is ensured to inhibit grain growth during austenitizing heating, and simultaneously, a proper amount of dissolved V, Ti plays a role in inhibiting C diffusion in the bainite phase transformation process, thereby further refining the bainite structure. Namely, the content of the beta-cyclodextrin needs to satisfy the parameter beta relation: 0.050 ≤ 0.9V (%) + [ Ti (%) -3.43N (%) ] ≤ 0.080, and β ═ 0.9V (%) + [ Ti (%) -3.43N (%) ]. When the value of β is less than 0.050, although the contents of the individual V, Ti elements may be all within the most suitable ranges described above, excellent ductility and toughness cannot be obtained; when the value of β is more than 0.080, the effect is saturated and the cost of steel is increased.
Further, the tensile strength of the material after the non-quenched and tempered steel is forged into the forged piece with the equivalent diameter of 50mm is 1100-1300MPa, and the yield strength is 800-950 MPa.
Further, after the non-quenched and tempered steel is forged into a forged piece with the equivalent diameter of 50mm, the post-fracture elongation of the material is 14-17%, the reduction of area is 45-55%, and the U-shaped impact energy is 60-90J.
The invention principle is as follows:
(1) the Mn and B elements are reasonably matched, a bainite structure is obtained in a wider cooling speed range, and the bainite structure is obtained after controlled cooling after forging large-size forgings with the diameter of more than 50 mm;
(2) the microalloying element V, Ti is added in a compounding way, so that on one hand, a proper amount of undissolved M (C, N) particles rich in titanium are ensured to inhibit the growth of crystal grains during austenitizing and heating, and simultaneously, a proper amount of dissolved V, Ti plays a role in inhibiting the diffusion of C in the bainite phase transformation process, thereby further refining the bainite structure.
(3) The hardness and strength level of the material are improved by utilizing the fine grain strengthening and precipitation strengthening effects of microalloying V, Ti and the like, so that good mechanical properties are obtained.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:
compared with the prior art, the novel bainite non-quenched and tempered steel provided by the invention can obtain a bainite structure in a wider cooling speed range; the cheap Mn, B and other alloy elements are utilized, no precious alloy elements are used, and the cost is low; the tempering process is omitted in the preparation process, and air is blown to cool to room temperature after forging, so that the production cost is further reduced, the production period is shortened, and the energy is saved and the environment is protected; compared with the prior ferrite and pearlite type non-quenched and tempered steel, the steel has the advantages of high strength, good plasticity and toughness and the like, and can be used for replacing the quenched and tempered steel to produce large-size automobile steering knuckles and other safety parts with the diameter of more than 50 mm.
Detailed Description
The technical solution of the present invention is further explained below.
Sample preparation:
according to the designed chemical composition range, 3 furnaces of the steel of the invention and 2 furnaces of the comparative steel are smelted on a 110kg vacuum induction furnace, and the specific chemical compositions are shown in table 2, wherein furnace numbers 1-3 are the steel of the invention, and furnace numbers 4-5 are the comparative steel. Forging the 110kg steel ingot into a bar with the diameter of 50mm and 80mm, and blowing and cooling after forging. The standard room temperature tensile sample (the gauge length d0 is 5mm and the gauge length l0 is 5d 0) and the Charpy U-shaped impact sample required by the experiment are processed according to the national standard. In the specific production process, the corresponding steel can be obtained by using the corresponding preparation process.
And (3) performance testing:
the specimens were subjected to tensile and impact tests at room temperature and the results are shown in Table 3.
As can be seen from Table 3, after the steel of the invention is forged into bars with two specifications (directly 50mm and 80mm) and is controlled to be cooled, the mechanical properties of the tensile strength of more than or equal to 1100MPa, the yield strength of more than or equal to 800MPa, the elongation after fracture of more than or equal to 14%, the reduction of area of more than or equal to 45% and the room temperature impact energy (KU2) of more than or equal to 60J can be obtained, and the steel presents good matching of strength, plasticity and toughness. Compared with the comparative steel, the mechanical properties of the steel of the invention are obviously improved under the same treatment process.
Table 2 chemical compositions (mass%,%) of examples of the present invention
| Furnace number | C | Si | Mn | P | S | Cr | V | Ti | B | Al | N | Fe |
| 1 | 0.21 | 0.50 | 2.87 | 0.007 | 0.035 | 0.17 | 0.042 | 0.035 | 0.0006 | 0.020 | 0.0045 | Surplus |
| 2 | 0.21 | 0.55 | 2.15 | 0.009 | 0.059 | 0.22 | 0.045 | 0.036 | 0.0027 | 0.028 | 0.0051 | Surplus |
| 3 | 0.18 | 0.47 | 2.39 | 0.010 | 0.039 | 0.21 | 0.066 | 0.024 | 0.0016 | 0.019 | 0.0042 | Surplus |
| 4 | 0.20 | 0.51 | 2.06 | 0.006 | 0.035 | 0.18 | 0.039 | 0.032 | 0.0007 | 0.020 | 0.0047 | Surplus |
| 5 | 0.25 | 0.35 | 1.92 | 0.009 | 0.045 | 0.50 | 0.120 | — | — | 0.019 | 0.0057 | Surplus |
TABLE 3 Strength and plasticity of examples of the invention
Claims (5)
1. A high-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forgings is characterized by comprising the following components in percentage by mass: 0.16 to 0.25 percent of C; 0.40 to 0.70 percent of Si; mn 2.00% -2.90%; b0.0005 to 0.0025; p is less than or equal to 0.015 percent; 0.015-0.065% of S; 0.10 to 0.30 percent of Cr; v0.020% -0.080%; 0.015-0.050% of Ti; 0.015 to 0.035 percent of Al; 0.004-0.006% of N; the balance of iron and inevitable impurities.
2. The high strength and toughness bainite non-quenched and tempered steel suitable for large-specification forgings according to claim 1, wherein the mass percentages of Mn and B elements satisfy the following relation: mn (%) is more than or equal to 2.40 and B (%) +100B (%) is less than or equal to 3.00; wherein Mn (%), B (%) represent the mass percentages of Mn and B, respectively.
3. The high strength and toughness bainite non-quenched and tempered steel suitable for large-specification forgings according to claim 1, wherein V, Ti and the mass percentage of N elements satisfy the relation: 0.050 ≤ 0.9V (%) + [ Ti (%) -3.43N (%) ] ≤ 0.080; wherein V (%), Ti (%), and N (%) represent the mass percentages of V, Ti, and Nb, respectively.
4. The high strength and toughness bainite non-quenched and tempered steel suitable for large-specification forgings as claimed in claim 1, wherein the tensile strength of the material after forging the non-quenched and tempered steel into a forging with an equivalent diameter of 50mm is 1100-1300MPa, and the yield strength is 800-950 MPa.
5. The high strength and toughness bainite non-quenched and tempered steel suitable for large-specification forgings according to claim 1, wherein the post-fracture elongation of the material after forging the non-quenched and tempered steel into a forging with an equivalent diameter of 50mm is 14-17%, the reduction of area is 45-55%, and the U-shaped impact energy is 60-90J.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111440389.8A CN114293098A (en) | 2021-11-30 | 2021-11-30 | High-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forge piece |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111440389.8A CN114293098A (en) | 2021-11-30 | 2021-11-30 | High-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forge piece |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114293098A true CN114293098A (en) | 2022-04-08 |
Family
ID=80966446
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111440389.8A Pending CN114293098A (en) | 2021-11-30 | 2021-11-30 | High-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forge piece |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114293098A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115386803A (en) * | 2022-08-31 | 2022-11-25 | 马鞍山钢铁股份有限公司 | Non-quenched and tempered steel with high strength and toughness for wind power bolt and production method thereof |
| CN117512448A (en) * | 2023-10-16 | 2024-02-06 | 南京钢铁股份有限公司 | Bainite type non-quenched and tempered steel for heavy commercial vehicle steering knuckle |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63166949A (en) * | 1986-12-27 | 1988-07-11 | Aichi Steel Works Ltd | Non-heattreated steel for hot forging |
| CN101541992A (en) * | 2006-12-11 | 2009-09-23 | 株式会社神户制钢所 | High-strength steel sheet |
| JP2010242170A (en) * | 2009-04-06 | 2010-10-28 | Nippon Steel Corp | High strength hot forging non-heat treated steel excellent in toughness and method for manufacturing the same |
| CN105112774A (en) * | 2015-08-28 | 2015-12-02 | 浙江美力科技股份有限公司 | Air cooling hardened spring steel with high obdurability, low-medium-carbon and microalloy and forming and heat treatment process thereof |
-
2021
- 2021-11-30 CN CN202111440389.8A patent/CN114293098A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63166949A (en) * | 1986-12-27 | 1988-07-11 | Aichi Steel Works Ltd | Non-heattreated steel for hot forging |
| CN101541992A (en) * | 2006-12-11 | 2009-09-23 | 株式会社神户制钢所 | High-strength steel sheet |
| JP2010242170A (en) * | 2009-04-06 | 2010-10-28 | Nippon Steel Corp | High strength hot forging non-heat treated steel excellent in toughness and method for manufacturing the same |
| CN105112774A (en) * | 2015-08-28 | 2015-12-02 | 浙江美力科技股份有限公司 | Air cooling hardened spring steel with high obdurability, low-medium-carbon and microalloy and forming and heat treatment process thereof |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115386803A (en) * | 2022-08-31 | 2022-11-25 | 马鞍山钢铁股份有限公司 | Non-quenched and tempered steel with high strength and toughness for wind power bolt and production method thereof |
| CN115386803B (en) * | 2022-08-31 | 2023-07-25 | 马鞍山钢铁股份有限公司 | Non-quenched and tempered steel for high-strength and high-toughness wind power bolts and production method thereof |
| CN117512448A (en) * | 2023-10-16 | 2024-02-06 | 南京钢铁股份有限公司 | Bainite type non-quenched and tempered steel for heavy commercial vehicle steering knuckle |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN113322409B (en) | High-strength and high-toughness mining chain steel and manufacturing method thereof | |
| EP0648853B1 (en) | Non-heat-treated steel for hot forging, process for producing non-heat-treated hot forging, and non-heat-treated hot forging | |
| CN111118403B (en) | Ti microalloyed high-strength high-toughness bainite non-quenched and tempered steel and forging and cooling control process and production process thereof | |
| CN110079743B (en) | 1500 MPa-grade low-hydrogen delayed cracking sensitive hot forming steel and production method thereof | |
| CN113957335B (en) | Production and preparation method of non-quenched and tempered steel with tensile strength of 1100MPa | |
| CN114293098A (en) | High-strength and high-toughness bainite non-quenched and tempered steel suitable for large-specification forge piece | |
| AU2022208884A1 (en) | High-strength and toughness free-cutting non-quenched and tempered round steel and manufacturing method therefor | |
| AU2022208884A9 (en) | High-strength and toughness free-cutting non-quenched and tempered round steel and manufacturing method therefor | |
| CN111074148A (en) | 800 MPa-level hot stamping axle housing steel and manufacturing method thereof | |
| US20070006947A1 (en) | Steel wire for cold forging having excellent low temperature impact properties and method of producing the same | |
| CN112877591A (en) | High-strength and high-toughness steel for hardware tool and chain and manufacturing method thereof | |
| CN110724876A (en) | 1100 MPa-level hot-rolled high-strength steel plate and manufacturing method thereof | |
| CN114134431B (en) | 2000 Mpa-grade high-strength high-toughness high-hardenability spring steel by square billet continuous casting and rolling and manufacturing method thereof | |
| CN101660089A (en) | Tensile strength 600MPa grade aluminum system cold-rolled dual phase steel | |
| CN115369324B (en) | 38MnVS5 rare earth free cutting hot rolled round steel for automobile and preparation method thereof | |
| CN115896615A (en) | Sulfur-containing 37MnSiVSQ free-cutting non-quenched and tempered hot-rolled round steel and preparation method thereof | |
| CN111850397B (en) | High-temperature-resistant corrosion-resistant plastic die steel with excellent cutting performance and preparation method thereof | |
| JPH0425343B2 (en) | ||
| KR102174416B1 (en) | Low Carbon Bainite Micro-alloyed Steels for Cold Heading Applications having High Strength and High Impact Toughness and Method for Manufacturing the Same | |
| JP5233848B2 (en) | Non-tempered steel bar for direct cutting | |
| CN112410670A (en) | Bainite/martensite type non-quenched and tempered steel | |
| JP3059318B2 (en) | Manufacturing method of high fatigue strength hot forgings | |
| CN117512448A (en) | Bainite type non-quenched and tempered steel for heavy commercial vehicle steering knuckle | |
| CN115522139B (en) | F28MnVRE forgeable non-quenched and tempered hot-rolled round steel for piston and preparation method thereof | |
| JPH0470385B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20220408 |
|
| RJ01 | Rejection of invention patent application after publication |