CN105177274A - Laser hardening process - Google Patents
Laser hardening process Download PDFInfo
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- CN105177274A CN105177274A CN201510677513.0A CN201510677513A CN105177274A CN 105177274 A CN105177274 A CN 105177274A CN 201510677513 A CN201510677513 A CN 201510677513A CN 105177274 A CN105177274 A CN 105177274A
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Abstract
The invention discloses a laser hardening process. The laser hardening process is characterized by selecting the appropriate laser irradiation conditions, reinforcing the surfaces of metal parts and effectively improving the abrasion resistance, the hardness and the surface roughness of the metals. The laser processing process comprises the following steps: carrying out pretreatment on metals before hardening the metals, selecting appropriate laser parameters comprising power, pot diameter and scanning speed, and detecting hardness and depth of hardening layers, wherein the laser power is 500W-2KW, the defocusing distance is 0-2mm, the laser spot diameter is 2-5mm, the pulse frequency is 5-10kHz, the scanning speed is 10-100mm/s, the protective gas is oxygen or nitrogen, and the flow is 4-5L/min. The laser hardening process is high in production efficiency, small in heat influence area and small in quenching stress and deformation, is capable of reaching high hardness, high abrasion resistance and high fatigue strength, and is environmentally-friendly and pollution-free.
Description
Technical field
The present invention relates to a kind of laser hardening technique.
Background technology
The surface property that various process for treating surface improves bearing is all have employed, to give full play to the potentiality of material in the country of industrial technology prosperity.Laser surface treating technology also obtains investigation and application widely.
Within 1980, LASER HEAT TREATMENT is used in bearing industry by USSR (Union of Soviet Socialist Republics), and its advantage is: the bearing surface wear resistance through laser reinforcing improves greatly.After steel alloy bearing parts laser reinforcing, bearing work-ing life can be improved.Carbon steel bearing part can replace high quality steel part after adopting laser treatment, thus can save expensive alloys steel.Ball track surface also can adopt laser intensify treatment.United States Navy penetrates in face weapons center and army missile portion and achieves many successes to carrying out for parts such as missile-borne cam, gear, bearings laser phase-transformation hardening to replace carburizing or nitridation process respectively.Locking bit cone endoporus ball runway place hardness for ball (ball) should higher than other this technical requirements of position hardness, JohnF.Fischer proposes measure ball runway being carried out to laser transformation selective sclerosing in patent US4303137, can meet the demands after quench cooled.The technology adopting laser beam melts powdered coating materials to make it to be attached to substrate surface is proposed in patent US4243867.On this basis, GunesM.ecer proposes the new technology that obtains composite bearing surface in patent US4474861, namely first by high-density thermals source such as laser, hard metal-powder is coated to bearing surface, then between hard coat, softer metals powder is filled, after softer metals is solidified and is filled with the gap between hard surface coatings, carry out processing with conventional means effects on surface and obtain required composite bearing.The softer metals be suitable for comprises bearing metals and such as silver, tin, nickel, copper, lead and respective alloy material thereof.With regard to strengthening mechanism and the fabric study aspect of laser transformation hardening, many experts and scholars' results of study show, its hardened layer structure property is better than conventional quenching.Laser quenching rapid heating and the feature cooled fast, make laser quenching surface have the hardness and wear resistance higher than conventional quenching, part heart portion can be made still to keep good plasticity and toughness simultaneously.A large amount of investigation and application example show both at home and abroad, and general Cooling Velocity of Hardened Layer of Laser Quenching hardness ratio conventional quenching improves 15% ~ 20%, and wear resistance also can significantly improve.The cost of LASER HEAT TREATMENT than flame or induction heat treatment high.Because LASER HEAT TREATMENT can not produce much distortion, do not need machining subsequently, also eliminate the manufacturing procedure such as annealing, sandblasting, rectification required for each procedure simultaneously.Therefore, in many cases, generally or economical.In general, although the case depth that laser transformation hardening obtains is significantly less than the degree of depth that normative heat treatment reaches, its anti-fatigue performance and wear resistance better than normative heat treatment.Aktiebolaget SKF thinks and can obtain suitable benefit from the effect that surface treatment obtains.This surface treatment working method of SKF exploitation comprises: (1) obtains cementation zone with chemical heat treatment method.This method comprises and carbon or nitrogen being penetrated in common rapid steel microstructure, or little degree changes carbon content.(2) partial heat treatment is carried out to common rapid steel under hardening, to obtain cementation zone by methods such as laser, electron beam or induction quenchings.The electron beam surface transformation hardening technology of aeroplane engine mainshaft bearing circle has been studied successfully by Aktiebolaget SKF of the U.S..The working conditions of bearing is usually very complicated, and its form lost efficacy also is usually the composite type of various of failure.Any surface reinforcing method has its scope of application and best applications condition, and various surface strengthening technology has bigger difference on strengthening layer thickness and performance, only selects rational technique just can reach the object improving bearing life.
Laser surface treating technology present Research
In the research of laser quenching, domestic and international expert predicts around laser quenching temperature field simulation and case depth, the abrasion resistance properties of hardened layer and fatigue strength, pretreatment coating the aspect such as development and specific absorption carried out extensive research.Composition and preparation technology determine materials microstructure structure, and certain weave construction determines its use properties.Laser technical parameters should be in optimized selection to obtain desirable microtexture and material property.Generally speaking, still not deep enough in the fundamental research controlled in laser scanning technique and process parameter optimizing thereof at present, also lack systematicness, performance optimization target often concentrates on case depth, surface hardness two indices, to other performance index study few.In fact, practical application effect not only refers to case depth, and after also comprising workpiece laser quenching, whether surface hardness, unrelieved stress, tissue distribution and the aspect such as case depth and homogeneity of structure meet the requirements.So the relation of laser technical parameters and hardenability band inner tissue performance should be furtherd investigate further, to by selecting suitable laser technical parameters to control the structure property in hardenability band.Such as initial hardness is not determine the single factor of heavy loading material wear-resistant performance, and wear resistance to a great extent, is decided by the structural capacity that the toughness of material and intense plastic strain condition cause material to be reinforced.In general, when not necessarily surface hardness is maximum, material is the most wear-resisting, wear resistance is also decided by case depth and toughness index, and the toughness of laser hardening layer and plasticity are seldom taken into account, so be the importance needing further investigation further based on the optimal control of the laser scanning processing parameter of many-sided performance index comprehensive.Complete processing changes the heterogeneous microstructure of material, and the change of material property stems from the change of heterogeneous microstructure, namely heterogeneous microstructure is the tie linking processing behavior and final performance, is therefore understand complete processing to the important means of final performance impact by the change of analysis of material microtexture state.
In laser strengthening, material be processed region thermal cycling change depend on acting light bundles, action time, the heat conductivility of treated material and the factors such as condition of surface, geometrical shape of workpiece, and under existence conditions be difficult to these factors are accurately controlled.Generally speaking, the research work for the purpose of laser surface intensified is at present based on material surface performance test and numerical simulation analysis, very imperfect to the understanding of modifying process and mechanism of action, thus hinders the development of this modern technique.Therefore, disclose change and the related law of material surface state on a microscopic scale, not only to the material modification mechanism inquired under lasing, there is important theory value, and to developing, improving laser surface modification technique, this technology is applied more fully and has great importance.
Laser transformation hardening technology is applied to the surface property improving bearing etc., need use for reference the features and application experience of other surface treatment methods, for realizing the direct application of laser reinforcing technology in industries such as bearings, should consider following aspect problem.Comparative analysis is done to various method for curing:
(1) case depth
In laser quenching research and apply, people extremely pay close attention to hardened layer performance and case depth, the metal parts Cooling Velocity of Hardened Layer of Laser Quenching layer depth comprising gear is generally about lmm, great majority 0.6 ~ o.8mm between, and practical application obtains desirable effect.But compared with conventional surface process, people always can propose hardened-depth and spend shallow problem.
For high-frequency quenching and brinelling, may not be that case depth is darker, surperficial bearing resistance be just higher, should there is best case depth; And concerning nitrogenize and tufftride process bearing, be then that case depth is darker, surperficial bearing resistance is higher.For gear, as Japanese rattan Tian Jun points out, if hardened layer is too shallow, Surface of Gear will occur to crush phenomenon.If case depth is excessive, surface withstand voltage intensity declines on the contrary, and increases process costs.So reasonably determine that case depth is very necessary.For the gear hardened by induction quenching, case depth should be got larger.Because its hardness gradient is relatively steeper, under flank of tooth hardened layer, there is an intensity lower than the tempering band of modified matrix strength, need to avoid.Certain large-scale large module gear steel mill domestic produces milling train gear, marine gear, military hardware gear etc., material is medium carbon steel and medium carbon alloy steel, as 45 steel, 40Cr, 42CrMo, 40CrNiMoA, 34CrNiMo steel etc., adopt laser quenching, actual case depth is about 0.5ram--0.8mm, and practical effect is fine.Theory and practice all shows, the Cooling Velocity of Hardened Layer of Laser Quenching degree of depth is 0.6mm-1.2mm is feasible, suitable.But someone thinks that the degree of depth of laser hardening is shallow relative to other Measures compare, is not suitable for the very large heavy parts of load.
(2) austenitic transformation and inhomogeneity of structure in rapid heating
When much studying austenitic transformation in rapid heating at present, do not consider the problem of inhomogenous austenite formation and inhomogeneity of structure.And in modeling effort rapid heating, inhomogenous austenite during austenitic transformation, should be furtherd investigate formed and the transition kinetics of process of cooling, thermodynamics and atomic diffusion process.Should by the change of the change of martensite transformation temperature under the different laser technical parameters of simulation, heating rate and rate of cooling, to make prediction on the impact of hardened layer microtexture and austenite homogeneity.In LASER HEATING process, laser quenching causes in surface exists uneven temperature field, to cause in lasing district the inconsistent of the precipitation condition of Thermal Cycling, cooling conditions and carbide everywhere.Because the ununiformity of temperature everywhere, heated time is different again at different temperatures, and the degree of austenitizing is relevant therewith, and under LASER HEATING condition, cementite is difficult to abundant dissolving, so the austenite generated is very uneven.In fact these uneven austenites include high-carbon segregation district (former pearlite region) and carbon-poor area (former cable tagma), they form low carbon martensite region and high carbon martensite region respectively in rapid quenching processes subsequently, cause the ununiformity of microhardness.Even if original structure is even, the carbon content of laser quenching martensitic range is still uneven.Whether inhomogeneity of structure has impact to performance, need study further.
(3) hardened layer homogeneity
At present, commonplace view is thought, hot spot internal temperature is high, and in flat distribution, outside edge, then temperature plunges, and the cross section that thus quenches is a flat-top crescent, and the object obtaining an even hardenability band with hope has larger distance.Although develop many beam shaping systems both at home and abroad, shape of beam is modulated into the uniform rectangle of power density distribution and band shape, make the ability exporting to workpiece in the same time identical, but in lasing district, edge is center rapid heat dissipation comparatively, cause surperficial each point temperature rise different, thus produce uneven strengthening layer.
(4) residual austenite content is on the impact of part quality
After laser quenching, there is abundant residues austenite in quenching structure, compared with integral quenching, the remained austenite content in laser quenching tissue is much bigger, and the residual austenite content of the laser quenching GCrl5 bearing steel of people's measuring is 19-30%.Residual austenite postpones notch root and crack tip stress concentration, can suppress the germinating of fatigue cracking, hinders the expansion of crackle, has the effect of lift-off fatigue resistance.But because residual austenite intensity is low, easily germinate fatigue cracking, can fatigue resistance be reduced again, for obtaining high fatigue resistance, whether residual austenite exists an optimum value, and whether the too high residual austenite content in surface is harmful to contact fatigue property, has no report.Residual austenite is soft metastable phase, and (as in the use procedure of tempering or part) spinodal decomposition is martensite or bainite under certain conditions; The result of decomposing is that the hardness of part improves, and toughness declines; Owing to there is larger ratio tolerance between austenite and martensite, thus cause bearing size to change and affect service precision.The stability of residual austenite is also an important aspect on the impact of dimensional stability.
(5) transformation behavior in friction, wear process
Most investigator finds: after laser transformation hardening process, and the wear resistance of hardened layer is compared with conventional quenching, being significantly improved of temper.The effect of plus load and frictional force, all finds phase transition phenomena on friction top layer, as deformation induced transformation hardening when the what is called " white " of iron and steel friction surface, the friction induced phase transition of austenitic stainless steel, the friction of high Mn austenitic steel etc.But friction induced phase transition behavior and mechanism thereof do not obtain pay abundant attention in tribology research.Reason is the limitation of detection means; Simultaneously morely when research material tribology mechanism lay particular emphasis on the performance of material own, and the phase transformation of less concern textura epidermoidea is on the impact of friction process and result.
Summary of the invention
The object of the invention is to propose a kind of laser hardening technique.
For reaching this object, the present invention by the following technical solutions:
A kind of laser hardening technique, by selecting suitable laser irradiation conditions, intensive treatment is carried out to metal parts surface, the wear resistance of effective raising metal, hardness and surfaceness, comprise: inspection hardness and case depth---are selected suitable laser parameter, comprised power, spot diameter and sweep velocity etc.---in metal pre-treatment before sclerosis.Laser apparatus is YAG laser.Laser power is 500W---2KW, and defocusing amount is 0mm----2mm, laser spot diameter 2mm---5mm; pulse-repetition 5kHz---10kHz; sweep velocity is 10mm/s---100mm/s, and shielding gas is oxygen or nitrogen, and flow is 4L/min---5L/min.
Embodiment
Embodiment 1
A kind of laser hardening technique, by selecting suitable laser irradiation conditions, carries out intensive treatment to metal parts surface, effectively improves the wear resistance of metal, hardness and surfaceness.Comprise: inspection hardness and case depth---are selected suitable laser parameter, comprised power, spot diameter and sweep velocity etc.---in metal pre-treatment before sclerosis.Laser apparatus is YAG laser.The metal of sclerosis is 40Cr, and laser power is 1.5KW, and defocusing amount is-0.2mm, laser spot diameter 3mm, pulse-repetition 6kHz, and sweep velocity is 20mm/s, and shielding gas is oxygen or nitrogen, and flow is 4L/min---5L/min.After entering laser hardening, hardness reaches HRC64, and hardening depth is 0.8mm.
Embodiment 2
A kind of laser hardening technique, by selecting suitable laser irradiation conditions, carries out intensive treatment to metal parts surface, effectively improves the wear resistance of metal, hardness and surfaceness.Comprise: inspection hardness and case depth---are selected suitable laser parameter, comprised power, spot diameter and sweep velocity etc.---in metal pre-treatment before sclerosis.Laser apparatus is YAG laser.The metal of sclerosis is 40 steel, and laser power is 0.6KW, and defocusing amount is-0.2mm, laser spot diameter 5mm, pulse-repetition 6kHz, and sweep velocity is 50mm/s, and shielding gas is oxygen, and flow is 4L/min---5L/min.After entering laser hardening, hardness reaches HRC64, and hardening depth is 1.1mm.
Claims (3)
1. a laser hardening technique, it is characterized in that by selecting suitable laser irradiation conditions, intensive treatment is carried out to metal parts surface, the wear resistance of effective raising metal, hardness and surfaceness, comprise: inspection hardness and case depth---are selected suitable laser parameter, comprised power, spot diameter and sweep velocity etc.---in metal pre-treatment before sclerosis.
2. method according to claim 1, is characterized in that, described laser apparatus is YAG laser.
3. method according to claim 1; it is characterized in that; described laser power is 500W---2KW; defocusing amount is 0mm----2mm; laser spot diameter 2mm---5mm, pulse-repetition 5kHz---10kHz, sweep velocity is 10mm/s---100mm/s; shielding gas is oxygen or nitrogen, and flow is 4L/min---5L/min.
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105714074A (en) * | 2016-01-12 | 2016-06-29 | 北京莱思创激光技术有限公司 | Laser quenching method for screwdriver |
| CN107350746A (en) * | 2017-07-31 | 2017-11-17 | 世通海泰泵业（天津）股份有限公司 | A kind of processing method of pump shaft |
| CN108114681A (en) * | 2016-11-29 | 2018-06-05 | 山东润博生物科技有限公司 | A kind of glyphosate preparation kneader |
| CN108220575A (en) * | 2017-12-30 | 2018-06-29 | 中钢集团邢台机械轧辊有限公司 | A kind of laser reinforcing process of shaft-like workpiece |
| CN108384926A (en) * | 2018-03-15 | 2018-08-10 | 温州市赢创新材料技术有限公司 | A kind of local laser process of surface treatment of austenitic stainless steel |
| CN108608670A (en) * | 2016-11-29 | 2018-10-02 | 山东润博生物科技有限公司 | A kind of glyphosate preparation extruder |
| CN108607800A (en) * | 2016-11-29 | 2018-10-02 | 山东润博生物科技有限公司 | A kind of glyphosate preparation vibrated fluidized bed |
| CN108607384A (en) * | 2016-11-29 | 2018-10-02 | 山东润博生物科技有限公司 | A kind of glyphosate preparation kneader stirring blade |
| CN109694943A (en) * | 2019-02-12 | 2019-04-30 | 上海理工大学 | A kind of composite surface treatment method strengthened for gear surface |
| CN113528760A (en) * | 2020-09-18 | 2021-10-22 | 上海炬辰激光技术有限公司 | Laser quenching hardening treatment process for shaft hub of reed damper |
| US20220099091A1 (en) * | 2020-09-30 | 2022-03-31 | Trane International Inc. | Compressor including laser-hardened bearing surfaces |
| CN117961304A (en) * | 2024-03-26 | 2024-05-03 | 季华实验室 | Gear steel and surface modification method and application thereof |
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Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105714074A (en) * | 2016-01-12 | 2016-06-29 | 北京莱思创激光技术有限公司 | Laser quenching method for screwdriver |
| CN108607384A (en) * | 2016-11-29 | 2018-10-02 | 山东润博生物科技有限公司 | A kind of glyphosate preparation kneader stirring blade |
| CN108114681A (en) * | 2016-11-29 | 2018-06-05 | 山东润博生物科技有限公司 | A kind of glyphosate preparation kneader |
| CN108114681B (en) * | 2016-11-29 | 2020-06-30 | 山东润博生物科技有限公司 | Kneading machine for preparing glyphosate |
| CN108608670A (en) * | 2016-11-29 | 2018-10-02 | 山东润博生物科技有限公司 | A kind of glyphosate preparation extruder |
| CN108607800A (en) * | 2016-11-29 | 2018-10-02 | 山东润博生物科技有限公司 | A kind of glyphosate preparation vibrated fluidized bed |
| CN107350746A (en) * | 2017-07-31 | 2017-11-17 | 世通海泰泵业（天津）股份有限公司 | A kind of processing method of pump shaft |
| CN108220575A (en) * | 2017-12-30 | 2018-06-29 | 中钢集团邢台机械轧辊有限公司 | A kind of laser reinforcing process of shaft-like workpiece |
| CN108384926B (en) * | 2018-03-15 | 2019-11-12 | 温州市赢创新材料技术有限公司 | A kind of local laser process of surface treatment of austenitic stainless steel |
| CN108384926A (en) * | 2018-03-15 | 2018-08-10 | 温州市赢创新材料技术有限公司 | A kind of local laser process of surface treatment of austenitic stainless steel |
| CN109694943A (en) * | 2019-02-12 | 2019-04-30 | 上海理工大学 | A kind of composite surface treatment method strengthened for gear surface |
| CN113528760A (en) * | 2020-09-18 | 2021-10-22 | 上海炬辰激光技术有限公司 | Laser quenching hardening treatment process for shaft hub of reed damper |
| US20220099091A1 (en) * | 2020-09-30 | 2022-03-31 | Trane International Inc. | Compressor including laser-hardened bearing surfaces |
| CN117961304A (en) * | 2024-03-26 | 2024-05-03 | 季华实验室 | Gear steel and surface modification method and application thereof |
| CN117961304B (en) * | 2024-03-26 | 2024-06-04 | 季华实验室 | Gear steel and surface modification method and application thereof |
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Application publication date: 20151223 |