CN104611666A - Hot carburizing method for carburizing parts - Google Patents
Hot carburizing method for carburizing parts Download PDFInfo
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- CN104611666A CN104611666A CN201510017315.1A CN201510017315A CN104611666A CN 104611666 A CN104611666 A CN 104611666A CN 201510017315 A CN201510017315 A CN 201510017315A CN 104611666 A CN104611666 A CN 104611666A
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- Prior art keywords
- carburizing
- nitrogen
- atmosphere
- enriched gas
- furnace
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
Abstract
The invention discloses a hot carburizing method for carburizing parts. The hot carburizing method particularly comprises the following steps: carrying out high temperature heating treatment on metal parts required to be carburized inside a carburizing furnace at the temperature of 880 DEG C to 930 DEG C, and introducing nitrogen-base atmosphere and enriched gas into the carburizing furnace, wherein the quantities of the introduced nitrogen-base atmosphere and the enriched gas depend on the CO value inside the carburizing furnace; purifying impurities and harmful elements such as H, Mn, S, Si and P, produced during the carburization process, by using nitrogen-base atmosphere and enriched gas, so as to obtain metal parts with relatively high carbon content and relatively good quality on surfaces of the metal parts. The hot carburizing method provided by the invention is simple and low in cost, the quality is ensured, the processing time is shortened, and the economic benefit is high.
Description
Technical field
The present invention relates to carburizing tech field, refer more particularly to a kind of hot method for carburizing for carburized parts.
Background technology
Under carburizing refers to that part is placed in high temperature austenite state, and add carrier gas in rich carbon atmosphere, long-time heating makes surface obtain the process of saturated carbon.In traditional carburization process, methyl alcohol is the carrying object as diluent gas, but methyl alcohol decomposes insufficient below 720 DEG C, if misoperation can be explosion caused, and the carbon black produced, affect carbon potential observing and controlling in follow-up stove.Although the Virahol that current carburizing uses as rich carbon agent, the methyl alcohol of carrier agent at high temperature can fast decoupleds, but be transformed into supervital carbon atom, actual temperature in stove then must more than 950 DEG C, under this condition, in stove, the density of carbon atom and vigor could increase, infiltration rate improves, but simultaneously also along with the unfavorable situation occurring living-article grain growth.Under the restriction of temperature, improved infiltration rate in cementation process and concentration is unappeasable, because have the CO of the about 1/3 and H of 1/3 when low temperature in carburizing atmosphere in the past simultaneously
2and a small amount of CO
2, H
2o, they stop in stove, gathering just creates carbon black, and the appearance of a large amount of carbon black not only reduces infiltration rate, and plugs pipeline.If reduce the infusion volume of methyl alcohol, Virahol, although can reduce the formation of carbon black, relative infiltration rate is just lower, causes the waste of the energy and the expenditure of cost.
Summary of the invention
The object of the invention is to overcome above-mentioned weak point of the prior art and provide that a kind of technique is simple, cost is low, the hot method for carburizing for carburized parts of energy saving resources.
The present invention realizes in the following way:
A kind of hot method for carburizing for carburized parts, it is characterized in that: specific as follows: to needing the metal parts of carburizing to carry out high-temperature heating treatment in the cementing furnace under 880 DEG C of-930 DEG C of high temperature, in cementing furnace, pass into nitrogen-based atmosphere and enriched gas simultaneously, the amount passing into nitrogen-based atmosphere and enriched gas depends on the CO value in process furnace, and the CO value in described process furnace controls within the scope of 0.1-0.5mg/ ㎡ in heat-processed always; Nitrogen-based atmosphere and enriched gas is utilized to carry out purifying in cementation process the impurity and H, Mn, S, Si, P harmful element produced, to obtain the higher and quality preferably metal parts of metal parts surface carbon content.
Described nitrogen-based atmosphere is the nitrogen of 40% by mass ratio: the methanol mixed of 60% forms.
Described enriched gas is following one wherein: CH, CH
4, CH
3cOCH
3, C
3h
8o.
Beneficial effect of the present invention is: a. nitrogen methanol technics is compared with traditional carburization process, the time shorten of Deep Carburization Process 1/5 ~ 1/6, the resources such as the electric power consumed and methyl alcohol also greatly reduce, and in the control of surface carbon concentration, n-formyl sarcolysine alcohol technique wants relatively easy simultaneously; B., in strong cementation process, the surface carbon concentration of nitrogen methanol technics is substantially the same with ordinary process, but nitrogen methanol technics is slightly fast in the process rising carbon potential, the demand of Virahol reduces relatively, after diffusion, the concentration on surface all meets the demands, and can ensure the quality of products and can reduce costs.
Accompanying drawing explanation
Fig. 1 Φ 100 × 200mm of the present invention obtains coupon and profile of tooth test block laboratory test results schematic diagram;
Fig. 2 delamination interpretation of the present invention graphic representation.
Embodiment
Now by reference to the accompanying drawings, the specific embodiment of the invention is described in detail in detail:
A kind of hot method for carburizing for carburized parts, specific as follows: to needing the metal parts of carburizing to carry out high-temperature heating treatment in the cementing furnace under 880 DEG C of-930 DEG C of high temperature, in cementing furnace, pass into nitrogen-based atmosphere and enriched gas simultaneously, the amount passing into nitrogen-based atmosphere and enriched gas depends on the CO value in process furnace, and the CO value in described process furnace controls within the scope of 0.1-0.5mg/ ㎡ in heat-processed always; Nitrogen-based atmosphere and enriched gas is utilized to carry out purifying in cementation process the impurity and H, Mn, S, Si, P harmful element produced, to obtain the higher and quality preferably metal parts of metal parts surface carbon content.
Nitrogen-based atmosphere of the present invention is the nitrogen of 40% by mass ratio: the methanol mixed of 60% forms.
Enriched gas of the present invention is following one wherein: CH, CH
4, CH
3cOCH
3, C
3h
8o.
Other metallic impurity materials (H, Mn, S, Si, P) under 880 DEG C of-930 DEG C of high temperature in carburized parts are most active, are easily removed by harmful element (H, Mn, S, Si, P) by nitrogen-based atmosphere and enriched gas.
Embodiment: be described in detail for nitrogen-based atmosphere and carburized parts process for the shaft pinion of Three-Gorges Ship-lift:
1, nitrogen based carburizing atmospher
In nitrogen, add hydrocarbon polymer or the hydrocarbon oxygen compound (gas or liquid) of proper amt, because the additive used is different, just have dissimilar nitrogen-based atmosphere.Wherein nitrogen+methyl alcohol atmosphere is the type extensively adopted at present.Enter after nitrogen and methyl alcohol mix by a certain percentage in stove, at high temperature cracking forms carburizing atmosphere.Work as N
2with CH
3when OH mixes in the ratio of 40%:60%, the CO:H in stove in splitting gas atmosphere
2: N
2be about 20%:40%:40%.The proportion of composing of the atmosphere of this ratio and the endothermic atmosphere of Sweet natural gas prepared by raw material is very close.In order to make atmosphere have higher carbon potential, also need in stove, to add a small amount of enriched gas, as CH, CH
4, CH
3cOCH
3(acetone) or C
3h
8o (Virahol) etc.For carburizing atmosphere, except there is higher carbon potential, also to there be larger carbon transfer coefficient and certain available carbon amounts.In gas carburizing process process, the CO content in carburizing atmosphere is generally not less than 15%.
2, the calculating of nitrogen-based atmosphere carburizing furnace gas
The atmosphere constituent after cracking that to be combined in stove of nitrogen and methyl alcohol is stablized, and adopts oxygen probe to be easy to the automatic control realizing atmosphere carbon potential.When technological design, need according to the technical requirements of part carburizing, part shape and carburizing area, design furnace gas composition and origin feed rate, to ensure quality product and to reduce energy consumption.
Select N
2+ CH
3oH adds C
3h
8the atmosphere of O, being with in horse pit carburizing furnace not, carries out analysis and calculation to the gear shaft carburizing in the Three-Gorges Ship-lift with 17CrNiMo6 steel making as application example.Pit carburizing furnace is divided into four district's temperature controls, and the temperature difference is at about ± 5 DEG C, and in burner hearth, useful volume is 0.8 × 0.8 × 3.14 × 6.4m
3, about 12.86m
3.
3, carburized parts related data
Carburized parts is the shaft pinion of Three-Gorges Ship-lift, material is 17CrNiMo6, physical dimension is tooth depth 600mm, tip diameter 1190.678mm, tooth face hardness HRC60+4, tooth core hardness HRC35 ~ 40, the process of flank of tooth carburizing and quenching, effective case depth 6.0 ~ 6.5mm, because leave process redundancy by the process of 8mm infiltration layer, except the flank of tooth, rest part is all brushed with antioxidizing paint, so living-article can be reduced to the right cylinder of diameter 2400mm, high 600mm; The surface carbon content of cementation zone requires to reach 0.90% ~ 1.0%, and in order to convenience of calculation, the mean carbon content of cementation zone gets 0.70%C.
Pit carburizing furnace dimensions of the loading space can put a shaft pinion, and during carburizing, reach the carburizing specification of quality of regulation, the working lipe that living-article need stop in stove is 200 hours.
Gear shaft is after carburizing, and the carbon amounts that need increase is:
G＝2×3.14DBH△g (1)
In formula: D-part external diameter (cm)
B-part height (cm)
H-case depth (cm)
Carbon amounts (g) [the △ g=7.8g/cm increased in △ g-cementation zone
3× (0.7-0.1) %, carbon contents is averaged].
That is, G=2 × 3.14 × 240 × 60 × 0.8 × 7.8 × 0.006gC=3385.77gC
Therefore can calculate needs per hour to the carbon amounts of carburizing part supply in stove is:
3385.77gC÷200h＝16.93gC/h。
4, the carbon source in carburizing atmosphere and supply
At N
2+ CH
3play important activeconstituents in OH atmosphere and have CO, H
2and CH
4, say that carburization reaction has from thermodynamics:
2CO＝[C]+CO
2(2)
CO+H
2＝[C]+H
2O (3)
CH
4＝[C]+2H
2(4)
But driven terms of mechanics and industrial furnace production practice all show, the difference of three speed of response is very large, and its Chinese style (3) speed of response is the fastest, and be almost 40 times of formula (2), be 20 times of formula (4) simultaneously.According to the ultimate principle of reaction kinetics, if there is several reaction in system simultaneously, so whole system is by fastest reaction controlling, and in this atmosphere, carburizing is undertaken by reaction (3) in other words.Along with the carrying out of cementation process, CO and H in atmosphere
2continuous minimizing, H
2o constantly increases, and the carbon potential of atmosphere reduces, and carbon potential also decreases, and at this moment almost following reaction occurs simultaneously in atmosphere:
CH
4+H
2O＝CO+3H
2(5)
As can be seen from reaction (5), as long as there are enough CH in atmosphere
4just can by the H in atmosphere
2o reduces, and increases CO and 3H
2recover carbon potential and the carbon potential of atmosphere.CO is not carbon source it can be seen, but the transmitter of carbon, CH
4be only real carbon supplier, i.e. carbon source.Consider from furnace gas stability angle, in atmosphere, CO dividing potential drop should keep constant, therefore except successively supplying a constant basis N in stove
2+ CH
3outside OH mixture, also must add enriched gas according to the change of furnace gas composition, select to add C
3h
8o.So just there is reaction:
C
3H
8O＝CO+4H
2+2[C] (6)
So in cementation process, carbon source is exactly C
3h
8o.According to pertinent data, C
3h
8the carbon equivalent of O is 30g, 1 [mol] (mole, mol) C
3h
8o can provide 24 grams of carbon, in normal conditions, and often liter of C
3h
8o can provide:
24 grams of C/0.07 liter=311.69gC/L
For meeting the needs of 16.93gC/h in aforementioned calculating, minimum C
3h
8oH air demand is 16.93gC/h/311.69gC/L=0.054L/h.But, in order to object and the speed of carburizing can be reached, 12.86m in stove
3volume must have certain carbon concentration, consider the C be added in furnace gas simultaneously
3h
8o can not all be utilized, and wherein a small amount of precipitation in the gas phase becomes carbon black, separately has that part is residual releases outside stove in the offgas, therefore actually passes into obtain C
3h
8o is far longer than above-mentioned value.According to the result that actually operating draws, for the C of part carburizing
3h
8o should be 2 ~ 3L/h.
5, stove leaks gas volume
The fire door of pit carburizing furnace no longer opens after shove charge, generally on bell, is provided with waste-gas burning mouth, burner port is provided with regulated valve, when valve regulated to diameter is 2cm, can go out the consumption of furnace gas according to related data by formulae discovery below:
Q＝μF[2gh(г1-г)/г]1/2 m
3/s
Q-waste-gas burning mouth furnace gas consumption, m
3/ s
μ--steam coefficient, and desirable 0.9
F--leaving area, m
2
G--universal gravity constant, m/s
2, get 9.8m/s
2
The height of the furnace bottom of h--burner port, m, 6.4m
The unit weight of г 1-ambient air, kg/m
3, be about 1.04kg/m
3(when 50 DEG C)
The unit weight of г-furnace gas, kg/m
3, be about 0.186kg/m
3(when 920 DEG C)
Its calculation result is:
Q＝0.9×3.14×0.01×0.01×[19.6×6.4(1.04-0.186)/0.186]1/2
＝0.0002826×[575.944]1/2＝0.00678m
3/s＝24.42m
3/h
Be converted to the flow under standard state: 24.42 × 273/1193=5.56Nm
3/ h
The gas volume that leaks of burner port: 5.56Nm
3/ h.
The calculating of the air demand that 6, originates from
Therefore furnace gas supply is decided according to the outer discharge of furnace gas: 5.56Nm
3/ h.
As previously mentioned, the N selected
2+ CH
3the composition of OH cracking atmosphere is: 20%CO, 40%H
2, 40%N
2, its chemical equation is just:
2N
2+CH
3OH＝CO+2H
2+2N
2(7)
In normal conditions, the volume of 1 mole of (mol) gas is 22.4L, 2H
2be exactly 44.8L, nitrogen supply (NS) amount can be calculated thus:
44.8：X＝22.4×5:5560
X＝44.8×5560/22.4×5
X＝2224L＝2.224Nm
3
In normal conditions, CH
3oH is liquid, 1 mole of (mol) 32g (CH
3the proportion of OH is 0.791g/mL), be 40.46mL, form 5.56m according to determined ratio
3the air demand of/h, the quantity of methyl alcohol of needs supply per hour:
40.46：X＝22.4×5:5560
X＝40.46×5560/22.4×5
X＝2.01L
Therefore, for forming 5.56m in stove
3the 20%CO of/h, 40%H
2, 40%N
2carburizing atmosphere, its raw material supply amount is 2.224Nm
3/ h nitrogen, the methyl alcohol of 2.01L/h, the Virahol of 2 ~ 3L/h.
7, interpretation
In order to whether verification computation result is correct, according to the processing request of Three Gorges shaft pinion drawing, machined one piece and the on all four sample of living-article flute profile, material is 17CrNiMo6, modulus is 62.66725884, and flute profile sample comprises two complete flute profiles, is highly 300mm.Also machined a diameter is Φ 100 × 200mm coupon simultaneously.Flute profile sample, coupon and living-article are entered stove process simultaneously, ensure that the consistence of sample and living-article carburizing state.Then corrosion analysis is carried out by the module that sample to be cut into different thickness by wire cutting machine.
By obtaining coupon with Φ 100 × 200mm and profile of tooth test block experiment detects, by metallographic method and the delamination laboratory method mutual authentication achievement of infiltration layer.Its data are as shown in Fig. 1 form:
The result that can draw as Fig. 2 (delamination interpretation curve) is reanalysed to the data of such as Fig. 1:
As shown in Figure 2, depth of penetration is at 8.05 carbon content 0.36 places.Illustrate that carburized layer depth 6.0 ~ 6.5mm can ensure.
Think by analysis, Virahol is pyrolytic decomposition in carburizing, separate out a large amount of active particle carbon, but most of active particle carbon is all exist with the form of particle cluster, directly can not infiltrate living-article, particle cluster is bulk deposition in stove, just forms carbon black on living-article surface or gush from body of heater in vain to slattern.Nitrogen does not participate in reaction directly because of its physical property, but can play the effect of sweeping gas and dilution active particle group, and the active particle carbon that Virahol is decomposited obtains maximum service efficiency; Play conservation and improve the effect of living-article visual appearance.
Claims (3)
1. the hot method for carburizing for carburized parts, it is characterized in that: specific as follows: to needing the metal parts of carburizing to carry out high-temperature heating treatment in the cementing furnace under 880 DEG C of-930 DEG C of high temperature, in cementing furnace, pass into nitrogen-based atmosphere and enriched gas simultaneously, the amount passing into nitrogen-based atmosphere and enriched gas depends on the CO value in process furnace, and the CO value in described process furnace controls at 0.1-0.5mg/m in heat-processed always
2in scope; Nitrogen-based atmosphere and enriched gas is utilized to carry out purifying in cementation process the impurity and H, Mn, S, Si, P harmful element produced, to obtain the higher and quality preferably metal parts of metal parts surface carbon content.
2. a kind of hot method for carburizing for carburized parts according to claim 1, is characterized in that: described nitrogen-based atmosphere is the nitrogen of 40% by mass ratio: the methanol mixed of 60% forms.
3. a kind of hot method for carburizing for carburized parts according to claim 1, is characterized in that: described enriched gas is following one wherein: CH, CH
4, CH
3cOCH
3, C
3h
8o.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105929861A (en) * | 2016-05-11 | 2016-09-07 | 玛切嘉利（中国）有限责任公司 | System for controlling carbon potential in heat treatment of cold drawing welded pipe for hydraulic cylinder |
| CN113621910A (en) * | 2021-09-15 | 2021-11-09 | 江苏丰东热技术有限公司 | Heat treatment controllable atmosphere recovery device |
| CN113913731A (en) * | 2021-11-12 | 2022-01-11 | 陕西柴油机重工有限公司 | Press-in type controllable atmosphere generating device |
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| CN105929861A (en) * | 2016-05-11 | 2016-09-07 | 玛切嘉利（中国）有限责任公司 | System for controlling carbon potential in heat treatment of cold drawing welded pipe for hydraulic cylinder |
| CN113621910A (en) * | 2021-09-15 | 2021-11-09 | 江苏丰东热技术有限公司 | Heat treatment controllable atmosphere recovery device |
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Application publication date: 20150513 |