CN101886241B - Heat treatment nitridation technology for metal - Google Patents
Heat treatment nitridation technology for metal Download PDFInfo
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- CN101886241B CN101886241B CN 200910051262 CN200910051262A CN101886241B CN 101886241 B CN101886241 B CN 101886241B CN 200910051262 CN200910051262 CN 200910051262 CN 200910051262 A CN200910051262 A CN 200910051262A CN 101886241 B CN101886241 B CN 101886241B
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Abstract
The invention discloses a heat treatment nitridation technology for metal. The technology is characterized in that pre-oxidation is carried out before nitridation to form a uniform oxidation film on a metal surface. The technology comprises the following steps: 1) vacuumizing a furnace; 2) charging nitrogen and uniformly heating to 520-570 DEG C; and 3) charging oxygen in the nitrogen atmosphere. In the invention, pre-oxidation is carried out before nitridation so as to form an even active oxidation film on a metal surface layer. The active oxidation film on the metal surface is a core absorbed by initial active nitrogen atoms, so that active nitrogen can be absorbed on the metal surface more effectively to speed up nitridation. Therefore, after the active oxidation film is formed on the metal surface, the nitridation process development has high stability.
Description
Technical field
The invention belongs to the metallic surface heat treatment process, relate in particular to steel-iron components and mould nitrogenize thermal treatment process.
Background technology
The thermal treatment nitrogenize be iron and steel under 520 ℃～570 ℃ temperature condition, nitrogenize and tufftride in ammonia+nitrogen or ammonia+methyl alcohol+nitrogen atmosphere.In recent years, on nitrogenize and soft-nitriding process, numerous embodiments is arranged: for example say and fill ammonia after vacuumizing in advance, or ammonia+methyl alcohol nitrogenation treatment technology; Also have rough vacuum heating formerly, afterpulse fills ammonia and carries out technologies such as nitrogenize.Existing hard nitrogenize technology, the cycle, generally at 24～28 hours, nitride layer reached 0.2～0.3mm, and in the nitriding process, the nitrogen gesture is wayward, forms crisp phase owing to the nitrogen gesture is too high, causes the degradation of mechanical component.
Summary of the invention
The technical problem that the present invention solves provides a kind of heat treatment nitridation technology for metal, can not only reduce the process time, and iron and steel can stably obtain good nitride layer tissue after treatment, has preferable toughness and hardness.
The present invention adopts following technical scheme:
A kind of heat treatment nitridation technology for metal is characterized in that before nitriding, carrying out preoxidation earlier, makes the metallic surface form uniform sull, comprises the steps:
(1) retort is vacuumized;
(2) inflated with nitrogen, even heating is to 520-570 ℃;
(3) under nitrogen atmosphere, fill oxygen.
Preferably, filling oxygen afterwards, gaseous constituent is 20% oxygen and 80% nitrogen.
The present invention has carried out pre-oxidation treatment before nitrogenize, make metal surface form layer of even active oxidation film.Actual production shows, in common nitridation process, the time phenomenon of in nitrogenize, can not oozing nitrogen arranged.Its reason is exactly when initial, and the metallic surface does not form the nuclear of ability adsorption activity nitrogen.In the nitriding process of nitrogenize, activated nitrogen atom is adsorbed on metallic surface, reaches the metallic surface of just jumping over after certain potential barrier and spreads to metal inside.And the active oxidation film of metallic surface then is the nuclear of initial activity nitrogen-atoms absorption, makes active nitrogen can be adsorbed on metallic surface in higher efficiency, has accelerated the speed of nitrogenize.Therefore after the metallic surface formed the active oxidation film, the differentiation of nitridation process was very stable.
Preferably, nitriding process is to charge into the mixed gas that comprises ammonia and nitrogen, divides two stages, and ammonia and nitrogen ratios are 1: 1 in the fs, and ammonia and nitrogen ratios are 1: 3 in the subordinate phase.
Preferably, the inflation mode of said nitriding process is the pulsed inflation, vacuumizes in advance before each inflation, to get rid of decomposed gas.Each pulse cycle all is under vacuum state, to send in the stove quantitative ammonia-nitrogen is stable.Owing at traditional injection-exhaust air technique, also do not get rid of entrap bubble fully, enter with regard to replenishing new gas; The unordered mixing of new and old gas makes ammonia in stove in the decomposition course, and ammonia dissociation rate is difficult to control; It is fixed to cause atmosphere nitrogen gesture not weigh; Too high and low excessively ammonia dissociation rate all influences the quality of the permeating speed and the nitrided case of nitrogenize, therefore length not only consuming time, and poor effect.And in the present invention; Before each inflation all is vacuum state, like this through the reacted atmosphere of emptying, imports the period (PW) of new gas; Regulate the input gas vol; Controlled the ammonia dissociation rate in the stove, reached the content of the active nitrogen of control decomposition, to keep relative constant nitrogen gesture ratio.
Preferably, the temperature in the retort is uniform.At any time keep part or mould under the uniform temperature condition, it is in the middle of the atmosphere that circulates always.So; No matter be heating or cooling conduction, can both control the deformation in the nitriding treatment process of part or mould, guarantee that simultaneously part and mould are under same temperature condition; The nitrogen-atoms that infiltrates metal has identical rate of diffusion, and nitride layer deep structure homogeneous microstructure is distributed.
The beneficial effect that the present invention has that nitrogenize workpiece and mould infiltration rate are fast, no blind hole deep hole effect, nitriding atmosphere are very easily controlled, steady quality, fragility can reach 0 grade.Corresponding common gases nitriding process, the present invention shortens the process-cycle, has simplified technology, has practiced thrift the energy, has improved quality product.
Embodiment
The present invention implements through following steps:
(1) workpiece or mould are taken out rough vacuum＜100MPa in advance;
(2) (get rid of influence the gas of nitrogenize after) fill with pure nitrogen gas, even heating is to 520-570 ℃ in the nitrogen atmosphere that circulates;
(3) fill with oxygen, make the metallic surface be pre-formed uniform active oxidation film;
(4) the nitriding fs, carry out the vacuum pulse formula with the ammonia-nitrogen ratios of 1: 1 (adjustable) and inflate-bleed nitriding;
(5) nitriding subordinate phase is carried out the vacuum pulse formula with the ammonia-nitrogen ratios of 1: 3 (adjustable) and is inflated-bleed nitriding;
(6) take out rough vacuum＜100MPa after nitridation process finishes, in nitrogen atmosphere, force cooling, speed of cooling >=10 ℃/minute;
(7) be cooled to and be lower than 100 ℃ and come out of the stove.
Compared with prior art, the present invention has increased active pre-oxidation process before nitriding.Actual production shows, in common nitridation process, the time phenomenon of in nitrogenize, can not oozing nitrogen arranged.Its reason is exactly when initial, and the metallic surface does not form the adsorbable nuclear of activated nitrogen atom.In the nitriding process of nitrogenize, activated nitrogen atom will be adsorbed on metallic surface, reaches the metallic surface of just jumping over after certain potential barrier and spreads to metal inside.And the active oxidation film of metallic surface then is the nuclear of initial activity nitrogen-atoms absorption, makes active nitrogen can be adsorbed on metallic surface in higher efficiency, has accelerated the speed of nitrogenize.Therefore after the metallic surface formed the active oxidation film, it was very stable that nitridation process develops.The formation of active oxidation film is different from general sull, the sull that under normal temperature and lesser temps, forms, and this sull does not have the attribute of " activity " in nitriding process, and it seldom or does not almost have the effect of adsorption activity nitrogen-atoms.(preferred temperature condition is 540 ℃) charges into pure nitrogen gas, under nitrogen protection under the hot conditions after vacuumizing; Charge into oxygen; The sull that this process and metallic surface form could generate the sull of " activity ", reaches the purpose of sull catalysis nitrogenize process.During preoxidation, the ratio of these two kinds of gases is 20% oxygen and 80% nitrogen.
In the nitriding treatment process, the gas that charges into is certain ammonia and nitrogen, and concrete ratio is looked different steel grades, different steps situation and decided.In the present embodiment, nitridation process in two stages, fs ammonia-nitrogen ratios is 1: 1, subordinate phase ammonia-nitrogen ratios is 1: 3.The mode of pouring is adjustable pulsed, reaches the adjustment PW through frequency being set or adjusting inflationtime.What need assurance is before charging into new gas each time, to be vacuum state in the stove.The atmosphere that feeds like this is constant, and the term harmonization in ammonia-nitrogen decomposition course makes the rate of decomposition of ammonia stable, and the nitrogen gesture is stable, and nitriding speed is fast, can reach the ideal nitrided case, and nitridation time shortens greatly.According to " vacuum-pulsed inflation-vacuum-pulsed inflation " cycle operation, can obtain stable nitrided structure, 0 grade of fragility has been practiced thrift the energy, work efficiency, has improved quality product.
Wherein, the ratio of ammonia and nitrogen, inflationtime, the amount of pouring, speed of cooling etc. are all relevant with material properties in the nitriding process.
No matter be preoxidation process or nitridation process, the gas circulation that all need keep stove to irritate interior flows.Temperature-rise period, metal parts just can be by even heating under gas strong convection thermal conduction condition; During preoxidation, the piece surface short period of time can evenly form the active oxidation film; During nitrogenize, the strong mixing convection gas can guarantee that the temperature in the stove is at every moment even, makes part nitriding in same temperature in the stove.In the present embodiment, big flow fan is set in stove, after the inflation, fan rotates, and furnace gas flows; When vacuumizing, fan quits work.No matter be heating or cooling conduction, can both control the temperature difference deformation in the nitriding treatment process of part or mould.Simultaneously, the nitriding under uniform temp of part and mould makes the nitride layer depth, homogeneous microstructure.
Usually; The structure of part or mould is if exist blind hole, and old gas hold-up directly can influence the entering of new gas in the hole; So in the present invention " vacuum-pulsed inflation-vacuum-pulsed inflation " is in the cycle; Can force to help the discharge of these old gases, introduce new gas, make the nitriding condition at blind hole place consistent with non-blind hole.Solved the uneven problem of the dark blind hole nitride layer of blind hole.
Claims (5)
1. a heat treatment nitridation technology for metal is characterized in that before nitriding, carrying out preoxidation earlier, makes the metallic surface form uniform active oxidation film, comprises the steps:
(1) retort is vacuumized;
(2) fill pure nitrogen gas, even heating is to 520-570 ℃ in the nitrogen atmosphere that circulates;
(3) under nitrogen protection, fill oxygen.
2. heat treatment nitridation technology for metal according to claim 1 is characterized in that: the back gaseous constituent that fills oxygen is 20% oxygen and 80% nitrogen.
3. heat treatment nitridation technology for metal according to claim 2; It is characterized in that: nitriding process is to charge into the mixed gas that comprises ammonia and nitrogen; Divide two stages, ammonia and nitrogen ratios are 1: 1 in the fs, and ammonia and nitrogen ratios are 1: 3 in the subordinate phase.
4. heat treatment nitridation technology for metal according to claim 3 is characterized in that: the inflation mode of said nitriding process is the pulsed inflation, vacuumizes earlier before each inflation.
5. heat treatment nitridation technology for metal according to claim 4 is characterized in that: the temperature in the retort is uniform.
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| CN 200910051262 CN101886241B (en) | 2009-05-14 | 2009-05-14 | Heat treatment nitridation technology for metal |
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| CN 200910051262 CN101886241B (en) | 2009-05-14 | 2009-05-14 | Heat treatment nitridation technology for metal |
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| CN101886241B true CN101886241B (en) | 2012-05-30 |
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| CN104789923A (en) * | 2014-01-20 | 2015-07-22 | 广东柳菱宏通实业有限公司 | Application method of rare earth in pre-oxidation and soft nitriding technology |
| JP6487276B2 (en) * | 2015-06-01 | 2019-03-20 | 株式会社ジェイテクト | Manufacturing method of sliding member and manufacturing method of clutch plate |
| CN106835055B (en) * | 2017-03-08 | 2019-08-09 | 南华大学 | A kind of nuclear grade stainless steel of wear resistant corrosion resistant |
| CN106947938A (en) * | 2017-05-24 | 2017-07-14 | 昆山鑫昌泰模具科技有限公司 | The nitriding processing technology of cloth-feeding teeth of sewing machine |
| CN109811297A (en) * | 2017-11-21 | 2019-05-28 | 上海一普顿金属制品有限公司 | A kind of nitriding process on hot forged mould surface |
| CN110004401A (en) * | 2018-01-04 | 2019-07-12 | 中车齐齐哈尔车辆有限公司 | Metalwork Nitrizing Treatment method and nitriding metalwork |
| CN108747233B (en) * | 2018-05-04 | 2019-11-08 | 宁波市鄞州兴韩机械实业有限公司 | A kind of processing technology of mechanical main shaft |
| CN110423978A (en) * | 2019-07-24 | 2019-11-08 | 爱柯迪股份有限公司 | A kind of mold and Step for Die & Mold Nitridation technique |
| CN110724902A (en) * | 2019-11-18 | 2020-01-24 | 惠州市鑫洪柏精密五金制品有限公司 | Pollution-free steel gas blackening process |
Citations (1)
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| CN101368275A (en) * | 2007-08-15 | 2009-02-18 | 沈阳鼓风机(集团)有限公司 | 42CrMoE thermal treatment technique |
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101368275A (en) * | 2007-08-15 | 2009-02-18 | 沈阳鼓风机(集团)有限公司 | 42CrMoE thermal treatment technique |
Non-Patent Citations (3)
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| 代立新等.预氧化快速气体渗氮新工艺.《金属热处理》.1997,(第09期),第30-31页. * |
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Owner name: SHANGHAI GKN HUAYU DRIVELINE SYSTEMS CO., LTD. Free format text: FORMER NAME: NATIEFU DRIVE SHAFTS CO., LTD., SHANGHAI |
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Address after: 201315 Cambridge Road 950, Cambridge industry zone, Shanghai, Pudong Patentee after: Shanghai GKN Huayu Driveline Systems Co., Ltd. Address before: 201315 Cambridge Road 950, Cambridge industry zone, Shanghai, Pudong Patentee before: Natiefu Drive Shafts Co., Ltd., Shanghai |
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