CN1159487A - Spring having high nitrided properties and method for manufacturing the same - Google Patents
Spring having high nitrided properties and method for manufacturing the same Download PDFInfo
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- CN1159487A CN1159487A CN 96107326 CN96107326A CN1159487A CN 1159487 A CN1159487 A CN 1159487A CN 96107326 CN96107326 CN 96107326 CN 96107326 A CN96107326 A CN 96107326A CN 1159487 A CN1159487 A CN 1159487A
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Abstract
A method for forming a spring which can reduce variations in the surface hardness and the thickness of the hardened layer when the spring is nitrided. Before nitriding the spring, the thickness of an oxide film formed on the surface of the spring is reduced to 1.5 micrometer or less by electropolishing or any other suitable means so that the residual stress of the spring will be-5 kgf/mm2 to 5kgf/mm2 near its surface. Wit this arrangement, it is possible to increase the surface hardness and the thickness of the nitrided layer of the spring obtained by nitriding.
Description
The present invention relates to a kind of spring that requires high antifatigue, for example engine valve door spring, and the method for making this spring.
By quenching and tempering has produced the thick oxide film of 2-5 μ m being used to form on the steel wire of spring, make the oilness when improving its reeler and contacting with the formation spring.
Spring low-temperature annealing, descaling and the nitriding subsequently that forms by this spring wire.The unrelieved stress that is produced when forming spring for eliminating, low-temperature annealing is necessary.Then need scale removal for removing this oxide film and improving follow-up nitriding treatment effect.The general shot-peening scale removal of using.
But the such problem of spring of usefulness shot-peening scale removal: after the nitriding, the variation of the case depth that hardness and nitrogenize form is quite big.
By the various test-results that address this problem, we find the following fact.
＜1〉any unrelieved stress that may remain in the spring near surface all hinders the sclerosis of this spring.
＜2〉shot-peening that is used for scale removal causes unrelieved stress at the spring near surface.The variation of hardness and case depth causes residual stress distribution inequality in the spring after the nitriding.
Therefore, be effective nitriding of narrow and small variation, it is important removing the maintenance of this oxide film and unrelieved stress as far as possible for a short time.
According to the present invention, the spring that provides height to ooze the atmosphere performance, the thickness of its lip-deep oxide film before its nitriding, is not more than 1.5 μ m, and the unrelieved stress that it is surperficial before its nitriding, is not less than 5kgf/mm
2, be not more than 5kg/mm
2
Obtain this spring with one of following three kinds of methods.
(1) method that comprises the steps: with steel wire bend to spring-like, with this spring-like steel wire low-temperature annealing, with method chemistry and/or electricity the oxide thickness that forms on this Steel Wire Surface is reduced to 1.5 μ m or still less, and with this spring-like steel wire nitriding.
(2) method that may further comprise the steps; With steel wire bend to spring-like, with this spring-like steel wire low-temperature annealing, with mechanical means the oxide thickness that forms on this Steel Wire Surface is reduced to 1.5 μ m or still less, with this steel wire low-temperature annealing in inert gas atmosphere or under vacuum, and to its nitriding.
(3) method that may further comprise the steps: the oxide thickness that forms on the Steel Wire Surface is reduced to 1.5 μ m or still less, this steel wire is formed spring-like, with this spring-like steel wire low-temperature annealing in inert gas atmosphere or under vacuum, and to its nitriding.
We are interpreted as any definite in the above described manner various condition now
Oxide thickness: 1.5 μ m or still less
The diffusion of nitrogen when the zone of oxidation that is thicker than 1.5 μ m hinders nitriding.Be that zone of oxidation is removed fully ideally.
Unrelieved stress: be no less than-5kg/mm
2, and be not more than 5kg/mm
2
Exceed this scope, nitrogen spread slow so that can not reach effective nitriding.
Remove the method for oxide film.
Because the diffusion of nitrogen when oxide film hinders the nitriding processing is so must be removed.But as being removed with the shot-peening method, will produce unrelieved stress, this reduces the efficient that nitriding is handled.Therefore, it is necessary removing oxide film with the method that does not produce unrelieved stress.These methods comprise chemical method, as pickling, and electric method, as electropolishing.Can use a kind of in these methods separately, maybe certain methods wherein can be used in combination.
As with the method that produces unrelieved stress, remove this oxide film as shot-peening or any other mechanical means, then must be with the spring low-temperature annealing to remove the unrelieved stress that be produced.This annealing must or be filled with rare gas element under vacuum, as carrying out in the atmosphere of argon gas in case the formation again of oxidation film.
Can be before spring wire be formed spring in the above described manner rather than remove zone of oxidation on this spring wire after this.In this case, the method for available any hope usefulness comprises the method removal oxide film that produces unrelieved stress.After forming spring, by make it to stand in inert atmosphere or vacuum under low-temperature annealing remove unrelieved stress, thereby do not form oxide film yet.
Narrate embodiments of the invention now.
Embodiment 1
Oil temper wire with diameter 4mm forms spring.Remove to make behind its lip-deep oxide film and stand low-temperature annealing, so that the difference to some extent each other of the oxide thickness of each spring and unrelieved stress.The nitriding that they were stood 450 ℃, 4 hours is handled.Be to estimate the nitriding effect, measure each spring from the hardness of the surperficial 20 μ m degree of depth as surface hardness.Also have, we measure and are reduced to from the surface to hardness and the degree of depth of the core hardness equivalence thickness as nitrided case.The results are shown in table 1.Higher surface hardness and/or deeper nitrided case mean higher nitriding treatment effect.The core hardness HV of any nitriding spring is about 470.
Seen in table 1, oxide film the surface hardness thin and spring that unrelieved stress is lower is higher and nitrided case is thicker.
Embodiment 2
As follows, form spring with three kinds that have the different thickness oxide film different steel wires.Make it to stand the processing shown in the table 2.Before making it nitriding, we measure the oxidated layer thickness and the unrelieved stress of every kind of spring.After the nitriding, surface measurements hardness and nitriding depth.The results are shown in table 2 and table 3.Carry out 450 ℃, 20 minutes low-temperature annealing.
Spring wire I: oxidated layer thickness=0 μ m.
Spring wire II: oxidated layer thickness=1.1 μ m.
Spring wire III: oxidated layer thickness=4.2 μ m.
Seen in table 2 and table 3, the arbitrary embodiment of the present invention all is being better than Comparative Examples aspect surface hardness and the nitriding depth.This excellent results has shown high nitriding treatment effect.
According to the present invention, the unrelieved stress in the spring has been reduced to minimum before nitriding.Therefore, it can the high-level efficiency nitriding.And the variation minimum of surface hardness and nitriding depth also is possible.
Table 1
| Oxide thickness (μ m) | Unrelieved stress (kgf/mm 2) | Surface hardness (HV) | Nitriding depth (μ m) | ||
| Embodiment | ?A | ????0 | ????2 | ????603 | ????160 |
| ?B | ????1.1 | ????-3 | ????597 | ????140 | |
| Comparative example | ?C | ????0 | ????-24 | ????589 | ????90 |
| ?D | ????0 | ????-74 | ????596 | ????80 | |
| ?E | ????2.0 | ????2 | ????555 | ????90 | |
| ?F | ????4.1 | ????2 | ????486 | ????50 | |
Table 2
| The steel wire type | Annealing atmosphere | The descaling method | Annealing atmosphere | Surface hardness (Hv) | Nitriding depth (μ m) | ||
| Embodiment | ?G | ??III | In atmosphere | Electropolishing | ??- | ????594 | ????160 |
| ?H | ??III | In atmosphere | Shot-peening | In argon gas | ????600 | ????140 | |
| ?I | ??I | In argon gas | ?- | ??- | ????609 | ????160 | |
| ?J | ??II | In argon gas | ?- | ??- | ????603 | ????150 | |
| Comparative example | ?K | ??III | In atmosphere | Shot-peening | ??- | ????594 | ????80 |
| ?L | ??III | In atmosphere | Shot-peening | In atmosphere | ????548 | ????90 | |
| ?M | ??I | In atmosphere | ?- | ??- | ????559 | ????60 | |
The steel wire type
I: oxidated layer thickness=0
II: oxidated layer thickness=1.1 μ m
III: oxidated layer thickness=4.2 μ m
Table 3
| Oxide thickness (μ m) | Unrelieved stress (kgf/mm 2) | ||
| Embodiment | ?G | ????0 | ????-4 |
| ?H | ????0.2 | ????3 | |
| ?I | ????0.3 | ????1 | |
| ?J | ????1.2 | ????-2 | |
| Comparative example | ?K | ????0 | ????-81 |
| ?L | ????2.4 | ????-3 | |
| ?M | ????2.1 | ????4 | |
Claims (4)
1. spring with high nitrided properties, before this spring nitriding, its surface is gone up oxide thickness and is not more than 1.5 μ m, and before its nitriding, its surperficial unrelieved stress is not less than 5kg/mm
2, and be not more than 5kg/mm
2
2. one kind prepares the method with spring having high nitrided properties, the method comprising the steps of: spring wire is formed the spring shape, makes this spring-like steel wire low-temperature annealing, with chemistry and/or mechanical means the oxide thickness that forms on this Steel Wire Surface is reduced to 1.5 μ m or littler, and with this spring-like steel wire nitriding.
3. one kind prepares the method with spring having high nitrided properties, the method comprising the steps of: spring wire is formed spring-like, make this spring-like steel wire low-temperature annealing, the thickness of formed oxide film on this Steel Wire Surface is reduced to 1.5 μ m or littler with mechanical means, with this steel wire low-temperature annealing in inert atmosphere or under the vacuum, and with this steel wire nitriding.
4. one kind prepares the method with spring having high nitrided properties, the method comprising the steps of: the thickness of the oxide film that forms on the spring wire surface is reduced to 1.5 μ m or littler, this steel wire is formed spring-like, with this spring-like steel wire low-temperature annealing in inert atmosphere or under the vacuum, and with this steel wire nitriding.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB961073268A CN1161490C (en) | 1996-03-09 | 1996-03-09 | Spring having high nitrided properties and method for manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB961073268A CN1161490C (en) | 1996-03-09 | 1996-03-09 | Spring having high nitrided properties and method for manufacturing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1159487A true CN1159487A (en) | 1997-09-17 |
| CN1161490C CN1161490C (en) | 2004-08-11 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB961073268A Expired - Fee Related CN1161490C (en) | 1996-03-09 | 1996-03-09 | Spring having high nitrided properties and method for manufacturing the same |
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|---|---|
| CN (1) | CN1161490C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104694872A (en) * | 2013-12-05 | 2015-06-10 | 上海中国弹簧制造有限公司 | Gas nitriding method for 55 SiCr steel bearing spring |
| CN111575637A (en) * | 2020-05-29 | 2020-08-25 | 青岛丰东热处理有限公司 | Method for low-temperature nitrocarburizing of austenitic stainless steel surface |
-
1996
- 1996-03-09 CN CNB961073268A patent/CN1161490C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104694872A (en) * | 2013-12-05 | 2015-06-10 | 上海中国弹簧制造有限公司 | Gas nitriding method for 55 SiCr steel bearing spring |
| CN104694872B (en) * | 2013-12-05 | 2017-06-20 | 上海中国弹簧制造有限公司 | The gas nitriding process of 55SiCr steel bearing springs |
| CN111575637A (en) * | 2020-05-29 | 2020-08-25 | 青岛丰东热处理有限公司 | Method for low-temperature nitrocarburizing of austenitic stainless steel surface |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1161490C (en) | 2004-08-11 |
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