CN101988141A - Non-quenched and tempered steel controlled cooling heating processing technology - Google Patents
Non-quenched and tempered steel controlled cooling heating processing technology Download PDFInfo
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- CN101988141A CN101988141A CN2010105463355A CN201010546335A CN101988141A CN 101988141 A CN101988141 A CN 101988141A CN 2010105463355 A CN2010105463355 A CN 2010105463355A CN 201010546335 A CN201010546335 A CN 201010546335A CN 101988141 A CN101988141 A CN 101988141A
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Abstract
The invention discloses a non-quenched and tempered steel controlled cooling heating processing technology. In the heating processing technology, isothermal treatment is carried out on the non-quenched and tempered steel after forging, and the technological parameters therein are as follows: the minimum cooling velocity Vc or the longest cooling time tc of the non-quenched and tempered steel piece before the isothermal treatment; the minimum cooling temperature Tmin of the steel piece before the isothermal treatment; the isothermal temperature Tiso of the steel piece; and the shortest isothermal holding time tiso of the steel piece. The four technological parameters are determined according to the actual chemical components and hardness requirements. The non-quenched and tempered steel obtained by the heating processing technology is a microstructure of undercooled austenite transformed at the constant temperature, and is uniform and stable, therefore the mechanical property thereof is also uniform and stable, and the microstructure and the mechanical property thereof are superior to the microstructure and mechanical property of the practical product under the continuous cooling condition; in the heating processing technology, the isothermal treatment is carried out under the conditions of at a certain temperature and no less than a certain cooling velocity, which is in favor of smooth production; and the adjusted regulation technological parameters are adopted for the steel with the same steel specification in the invention, and the parts with different validities and the parts requiring for different mechanical properties can be manufactured, which is in favor of expanding application ranges and reducing cost.
Description
Technical field
The present invention relates to a kind of thermal treatment process of steel, particularly a kind of non-hardened and tempered steel controlled chilling thermal treatment process.
Technical background
State-of-the-art connection rod of automobile engine is modifiedly (to remove quenching from non-in the world today, high tempering) steel spalling separation connecting rod cap and connecting rod body save branch and forge and process connecting rod cap, the body multiple working procedure, both energy-conservation, consumption reduction, simplified processing process, improve the quality of products again (bearing transvrsal stress because of connecting rod slides when avoiding occurring the work of quenching crack and connecting rod bolt), it is the peculiar technology of germany volkswagen company, key is to use this class non-hardened and tempered steel except requiring specific chemical ingredients, also require to specify the end quenching distance that specific hardness value is arranged at grade of steel, and hardness fluctuations very little (± HRC2), thereby steel mill to produce the qualification rate of this steel very low, cost up.At present, this steel of the still more difficult stably manufactured of China steel mill, the user needs import mostly, and price is very high, is about two times with trade mark steel.Comparing with the quenched and tempered steel product does not have the advantage that reduces production costs, thereby is difficult to wide popularization and application.Non-hardened and tempered steel spalling connecting rod requires controlled chilling behind the forging and molding, obtains nodular troostite (P) tissue, free ferrite (F)≤10%.Hardness is HRC29～31.Hardness is too high, because of being prone to hard crisp martensite (M) tissue the fragility increase can not be used; Hardness is low excessively, except intensity does not reach requirement, also can when fractured connecting rod covers viscous deformation take place and whole connecting rod is scrapped.
Yield strength σ 0.2 〉=520Mpa (σ b 〉=900Mpa with the use of Jetta car connecting rod, δ 5 〉=10%, ψ 〉=20%) 70S non-hardened and tempered steel is an example, now with forging process and forge back supercooled austenite (A) anisothernal transformation and the cold curve generalization figure of control as shown in Figure 1, as can be seen from Figure 1, the phase transformation that supercooled austenite takes place is carried out in a temperature range, the microstructure that forms has certain difference, the perlite sheet spacing that high temperature forms is big, hardness is low, the perlite sheet spacing that low temperature forms is little, the hardness height, and also this species diversity strengthens along with the increase of speed of cooling.And cause the steel part comprehensive mechanical property to reduce.From Fig. 1, it can also be seen that to have only when the speed of cooling of steel part equals V3, could obtain the mechanical property of technical requirements.Moreover on industrial production, the cooling of may command steel part speed of cooling, adjustable amplitude is very little, thereby the strict chemical ingredients and the hardening capacity characteristic that mainly rely on used steel guarantee.
We have measured supercooled austenite continuous cooling transformation curve and end quenching curve generalization figure such as Fig. 2, shown in Figure 3 of a kind of 70S non-hardened and tempered steel from German import, the net thickness that is equivalent to Jetta car connecting rod key position bar portion is 6mm, be about the cooling situation of end quenching curve when forging the back air cooling, i.e. 6.2 ℃/s of speed of cooling V700 ℃ of ≈ in the time of 700 ℃ apart from the end 22mm place of quenching.Only under this cooling conditions, the hardness of product just is HRC30, and microstructure is that nodular troostite adds the small-amount free ferrite.Because same grade of steel chemical composition of steel fluctuates within the specific limits, (the end quenching curve is apart from the hardness at the end 22mm place of quenching must to influence the J22 of steel, therefore require to use the end quenching curve band of steel very narrow ± HRC2, promptly the hardness at this place is HRC30 ± 2, be HRC～32), could satisfy technical requirements, this is the technological line that the habitual steel characteristics of American-European old industrially developed country adapts to processing treatment technology, and, if product requires mechanical property to increase or net thickness, then must use the non-hardened and tempered steel of another trade mark to make, as when requiring yield strength σ 0.2 〉=650Mpa, then need to use the 70MnVS steel.Therefore, be that a kind of part need use a kind of non-hardened and tempered steel number basically.Thereby caused the grade of steel of these class steel many, with the few situation of grade of steel output, this also becomes produces one of high reason of this class steel product cost.
Summary of the invention
The purpose of this invention is to provide a kind of non-hardened and tempered steel controlled chilling thermal treatment process, this technology be with easily smelt, cost is low with now use the non-hardened and tempered steel material identical, but need not to guarantee the steel of end quenching curve band, forge the back and adopt the technology of accurate controlled chilling, guarantee microstructure and mechanical property that the stable acquisition of product needs, make auto parts for automobile making provides energy-conservation, consumption reduction, environmental protection and fine non-hardened and tempered steel, and reduced manufacturing cost, improved economic benefit.
The present invention carries out Isothermal Treatment after non-hardened and tempered steel is adopted forging, and processing parameter wherein is as follows:
(1) before the isothermal processes the minimum speed of cooling Vc of non-hardened and tempered steel steel part or the longest cooling time tc;
(2) the minimum cooling temperature Tmin of steel part before the isothermal processes;
(3) the isothermal temperature Tiso of steel part;
(4) the shortest isothermal hold-time tiso of steel part;
tc≥tn/60(min)
Logtn(s)＝a
1C-b
1Si+c
1Mn+d
1Cr+e
1Mo+f
1Ni+g
1Cu-h
1；
Tmin(℃)
Tmin(℃)a
2-b
2Mn-c
2V-d
2Nb-e
2Si-f
3Cr-g
3Mo-h
2Ni-i
2W；
Tiso(℃)
Tiso(℃)＝{[(a
3-b
3Ni-c
3Cu-d
3Mn+e
3Mo+f
3Cr+g
3Si+h
3V+i
3Ti)-20]-[HB-(j
3+k
3C+l
3Al+m
3Ti+n
3Si+o
3Mn+P
3Mo+q
3Ni+r
3Cu+s
3W)]}/x
3(C-y
3)；
tiso(min)≥tm/60
Logtn(s)＝a
4C+b
4V+c
4Ti+d
4Mo+e
4Cr+f
4Mn+g
4W+h
4Ni+i
4Si+j
4；
A in the formula
1-4, b
1-4, c
1-4, d
1-4, e
1-4, f
1-4, g
1-4, h
1-4, i
2-4, j
3-4, k
3, l
3, m
3, n
3, o
3, P
3, q
3, r
3, x
3And y
3Be coefficient, C, Si, Mn, Cr, Mo, Ni, Cu, Nb, W, V and Ti are the percentage ratio of the constituent content in the steel, and HB is the Brinell hardness of steel part requirement.
Advantage of the present invention is:
1, the existing thermal treatment process of the machine parts of non-hardened and tempered steel product all is to adopt two sections coolings of cooling continuously (air cooling, blowing cooling) (blowing back air cooling earlier) behind forging and molding, and the present invention forges back isothermal processes, air cooling again.
2, the present invention is the microstructure that supercooled austenite changes under constant temperature, and is uniform and stable, thereby mechanical property is also uniform and stable, is better than reality and produces microstructure and the mechanical property that forms under continuous cooling conditions.
3, the present invention be adopt more than or equal to after a certain cooling rate in a certain temperature isothermal processes, a certain speed of cooling of control (variable scope is very little) is much easier in producing than reality, what help producing carries out smoothly.
4, the present invention adopts the adjusting process parameter can make the part and the part that requires mechanical property different (in the certain numerical value scopes) of availability difference (in the certain size scope) to same grade of steel.Existing technology then is a kind of size, and a kind of part of performance requriements needs a kind of grade of steel.So the present invention helps broadened application.
5, the present invention's technology does not need end quenching curve arrowband non-hardened and tempered steel, the then essential end quenching curve Ribbon Steel of existing technology, thereby can improve steel and smelt qualification rate and reduce production costs and price.
6, because enterprise wishes use in producing, government department encourages enterprise to use this class non-hardened and tempered steel to make machine parts, but owing to now steel are required very high (mainly being end quenching curve arrowband) with technology, the cost height, and be difficult to be extensive use of, to the technology of invention use, end quenching curve narrow bandwidth there is not strict demand, and can realize the many usefulness of a steel, control ratio is easier in addition, helps producing carrying out smoothly.
Description of drawings
Fig. 1 is that a kind of 70S non-hardened and tempered steel system connecting rod forges cooling control technology and supercooled austenite continuous cooling transformation curve generalization figure.
Fig. 2 is the supercooled austenite continuous cooling transformation graphic representation that Germany produces the 70S non-hardened and tempered steel.
Fig. 3 is that Germany produces 70S non-hardened and tempered steel end quenching graphic representation.
Fig. 4 is the swaging machine residual forging heat isothermal processes and the supercooled austenite isothermal transformation diagram of the present invention's 70S non-hardened and tempered steel automobile connecting bar.
Fig. 5 is the intensity under the different hardness and the synoptic diagram of plasticity after existing continuous process for cooling of 70S non-hardened and tempered steel and the isothermal processes of the present invention.
Embodiment
The present invention is according to the phase transformation characteristics of using steel and the relation of microstructure and performance, solve the problem that the non-hardened and tempered steel product exists now with another kind of thinking and method, what adopt is the variation of timely adjusting process parameter adaptation steel chemical ingredients and hardening capacity, with easy control isothermal processes (temperature of major control isothermal transformation), replace to be difficult to the speed of cooling of control, and the width of the end quenching curve band of steel is not needed to be strict with.
Be example now with 70S steel connecting rod, the present invention adopts and forges the back Isothermal Treatment, as shown in Figure 4, as can be seen from Figure 4, under the isothermal processes condition, because the pearlite type phase transformation takes place under a constant temperature supercooled austenite in the steel, microstructure is identical, mechanical property (as hardness, intensity, plasticity etc.) unanimity.And, can adopt different isothermal temperatures to obtain different mechanical properties.Thereby the width of steel end quenching curve band do not had special requirement, and can use a kind of grade of steel to make the different sizes and the part of intensity, promptly a steel (number) many with and replace steel alloy with carbon steel, become possibility for further reducing the steel production cost.
It can also be seen that from Fig. 4 the afterheat in casting isothermal processes novel process that the present invention uses both can avoid occurring hard crisp martensite fully, can avoid again too much soft free ferrite occurring, thereby the qualification rate of product is improved greatly.
As can be seen from Figure 4, the present invention's (isothermal processes) and existing treatment process (with adding continuous cooling) are compared, and steel part is intensity under same rigidity, and plasticity is higher, and along with hardness to increase its effect more obvious.The characteristic that this strong plasticity increases helps the product raising in work-ing life, and security increases.
The present invention carries out Isothermal Treatment after non-hardened and tempered steel is adopted forging, and processing parameter wherein is as follows:
(1) before the isothermal processes the minimum speed of cooling Vc of non-hardened and tempered steel steel part or the longest cooling time tc;
(2) the minimum cooling temperature Tmin of steel part before the isothermal processes;
(3) the isothermal temperature Tiso of steel part;
(4) the shortest isothermal hold-time tiso of steel part;
tc≥tn/60(min)
Logtn(s)＝a
1C-b
1Si+c
1Mn+d
1Cr+e
1Mo+f
1Ni+g
1Cu-h
1；
Tmin(℃)
Tmin(℃)a
2-b
2Mn-c
2V-d
2Nb-e
2Si-f
3Cr-g
3Mo-h
2Ni-i
2W；
Tiso(℃)
Tiso(℃)＝{[(a
3-b
3Ni-c
3Cu-d
3Mn+e
3Mo+f
3Cr+g
3Si+h
3V+i
3Ti)-20]-[HB-(j
3+k
3C+l
3Al+m
3Ti+n
3Si+o
3Mn+P
3Mo+q
3Ni+r
3Cu+s
3W)]}/x
3(C-y
3)；
tiso(min)≥tm/60
Logtn(s)＝a
4C+b
4V+c
4Ti+d
4Mo+e
4Cr+f
4Mn+g
4W+h
4Ni+i
4Si+j
4；
A in the formula
1-4, b
1-4, c
1-4, d
1-4, e
1-4, f
1-4, g
1-4, h
1-4, i
2-4, j
3-4, k
3, l
3, m
3, n
3, o
3, P
3, q
3, r
3, x
3And y
3Be coefficient, C, Si, Mn, Cr, Mo, Ni, Cu, Nb, W, V and Ti are the percentage ratio of the constituent content in the steel, and HB is the Brinell hardness of steel part requirement.
Claims (1)
1. non-hardened and tempered steel controlled chilling thermal treatment process, this technology adopt non-hardened and tempered steel carries out isothermal processes after forging, and processing parameter wherein is as follows:
(1) before the isothermal processes the minimum speed of cooling Vc of non-hardened and tempered steel steel part or the longest cooling time tc;
(2) the minimum cooling temperature Tmin of steel part before the isothermal processes;
(3) the isothermal temperature Tiso of steel part;
(4) the shortest isothermal hold-time tiso of steel part;
tc≥tn/60(min)
Logtn(s)＝a
1C-b
1Si+c
1Mn+d
1Cr+e
1Mo+f
1Ni+g
1Cu-h
1；
Tmin(℃)
Tmin(℃)a
2-b
2Mn-c
2V-d
2Nb-e
2Si-f
3Cr-g
3Mo-h
2Ni-i
2W；
Tiso(℃)
Tiso(℃)＝{[(a
3-b
3Ni-c
3Cu-d
3Mn+e
3Mo+f
3Cr+g
3Si+h
3V+i
3Ti)-20]-[HB-(j
3+k
3C+l
3Al+m
3Ti+n
3Si+o
3Mn+P
3Mo+q
3Ni+r
3Cu+s
3W)]}/x
3(C-y
3)；
tiso(min)≥tm/60
Logtn(s)＝a
4C+b
4V+c
4Ti+d
4Mo+e
4Cr+f
4Mn+g
4W+h
4Ni+i
4Si+j
4；
A in the formula
1-4, b
1-4, c
1-4, d
1-4, e
1-4, f
1-4, g
1-4, h
1-4, i
2-4, j
3-4, k
3, l
3, m
3, n
3, o
3, P
3, q
3, r
3, x
3And y
3Be coefficient, C, Si, Mn, Cr, Mo, Ni, Cu, Nb, W, V and Ti are the percentage ratio of the constituent content in the steel, and HB is the Brinell hardness of steel part requirement.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010105463355A CN101988141A (en) | 2010-11-17 | 2010-11-17 | Non-quenched and tempered steel controlled cooling heating processing technology |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010105463355A CN101988141A (en) | 2010-11-17 | 2010-11-17 | Non-quenched and tempered steel controlled cooling heating processing technology |
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|---|---|
| CN101988141A true CN101988141A (en) | 2011-03-23 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102728754A (en) * | 2011-04-07 | 2012-10-17 | 江铃汽车股份有限公司 | Reinforced control cooling method for non-tempered steel forging |
| CN104593573A (en) * | 2015-02-28 | 2015-05-06 | 南京工程学院 | Combined thermomechanical treatment strengthening method for efficiently improving strength and toughness of non-quenched and tempered steel |
| CN112296247A (en) * | 2020-10-10 | 2021-02-02 | 中国重汽集团济南动力有限公司 | Cooling process for manufacturing expansion-breaking connecting rod blank by using 38MnVS6 medium carbon non-quenched and tempered steel |
-
2010
- 2010-11-17 CN CN2010105463355A patent/CN101988141A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102728754A (en) * | 2011-04-07 | 2012-10-17 | 江铃汽车股份有限公司 | Reinforced control cooling method for non-tempered steel forging |
| CN104593573A (en) * | 2015-02-28 | 2015-05-06 | 南京工程学院 | Combined thermomechanical treatment strengthening method for efficiently improving strength and toughness of non-quenched and tempered steel |
| CN112296247A (en) * | 2020-10-10 | 2021-02-02 | 中国重汽集团济南动力有限公司 | Cooling process for manufacturing expansion-breaking connecting rod blank by using 38MnVS6 medium carbon non-quenched and tempered steel |
| CN112296247B (en) * | 2020-10-10 | 2022-05-06 | 中国重汽集团济南动力有限公司 | Cooling process for manufacturing expansion-breaking connecting rod blank by using 38MnVS6 medium carbon non-quenched and tempered steel |
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Application publication date: 20110323 |