CN103620081A - Steel product and manufacturing method therefor - Google Patents

Steel product and manufacturing method therefor Download PDF

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CN103620081A
CN103620081A CN201280031158.4A CN201280031158A CN103620081A CN 103620081 A CN103620081 A CN 103620081A CN 201280031158 A CN201280031158 A CN 201280031158A CN 103620081 A CN103620081 A CN 103620081A
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compound layer
layer
steel
fluorine
nitrogen
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CN103620081B (en
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西川晃司
富士川尚男
渡边崇则
岩村英明
藤田守弘
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Air Water Inc
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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
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • 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
    • C23C8/02—Pretreatment of the material to be coated
    • 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
    • C23C8/80—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Braking Arrangements (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

A steel product that combines excellent corrosion resistance and adhesiveness is provided. The steel product is obtained by forming a nitride compound layer and a nitrogen diffusion layer on the surface layer of a steel base material. The nitride compound layer contains a first compound layer that is formed on the nitrogen diffusion layer side, and a second compound layer that is formed on the surface side of the first compound layer. The first compound layer has an e-structure composed mainly of Fe3N, and the second compound layer has a higher nitrogen concentration than the first compound layer, and has protrusions and recesses formed on the surface. This configuration enables a nitride compound layer with excellent adhesiveness, extremely low carbon content and high corrosion resistance to be formed.

Description

Steel work and manufacture method thereof
Technical field
The present invention relates to steel work and manufacture method thereof, described steel work is by steel being implemented to follow the surface treatment of nitriding treatment, can make erosion resistance and cementability improve, and by being applied to the backing metal (Li gold) such as brake facing, brake-shoe, clutch plate etc., the goods that can make its weather resistance improve.
Background technology
The general most use of the friction members such as the brake facing using in automobile etc., brake-shoe, clutch plate using friction materials be bonded on the steel of backing metal and member.The bonding force of friction materials and backing metal and the performance of stopper, correlation of attributes are also very important factors from secure context.
In order to obtain the strong bonding force to friction materials, long ago just start to adopt and utilize the methods such as shot-peening to make the method for the face roughening of backing metal.In addition, if bonding interface gets rusty, bonding force can significantly reduce, and is therefore also considering on the basis of erosion resistance, and enforcement formation zinc phosphate etc. changes into the processing (routine patent documentation 1 described as follows) of tunicle and undercoat.
Yet the existing problems aspect thermotolerance such as tunicle that change into as described above, exist and cause erosion resistance and adaptation to reduce such problem because of heat.For stopper, clutch coupling, in the situation that it is extremely unsatisfactory to produce the characteristic of large heat of friction erosion resistance, adaptation reduction.
On the other hand, for mechanical component, the wearability of structural member, the weather resistance that makes to comprise various steel improves, in field, using nitriding treatment widely.Wherein also know: for the steel except stainless steel, by forming nitride compound layer on its surface, can improve erosion resistance.As one of its purposes, for example, be applied to the backing metal of brake facing.Steel except stainless steel are implemented to the backing metal after nitriding treatment, and be formed with the above-mentioned backing metallographic phase ratio that changes into tunicle, more favourable aspect erosion resistance.Therefore, also studied gas soft nitriding has been processed to the backing metal (routine patent documentation 2 described as follows) that is applied to brake facing.
But, in the situation that utilizing nitriding treatment to form backing metal, if only form simply nitride compound layer on surface, erosion resistance is improved, be inadequate.In order to improve the cementability of the pad material (パ ッ De material) making as friction materials when bonding, need to form micron-sized concavo-convex on its surface.
At this, salt Bath Nitriding Treatment is easy to form more concavo-convex surface, is therefore applied to backing metal (for example patent documentation 3).In salt Bath Nitriding Treatment, and by common gas soft nitriding, process the nitride that forms similarly, form Fe-C-N based compound.Therefore, with patent documentation 2 similarly, cannot say aspect erosion resistance it is sufficient.
Prior art document
Patent documentation
Patent documentation 1: Japanese kokai publication hei 5-346129
Patent documentation 2: Japanese Patent Publication 53-47218
Patent documentation 3: Japanese kokai publication sho 62-261726
Summary of the invention
Invent problem to be solved
In above-mentioned patent documentation 2, recorded: in order to improve the cementability with friction materials, and it is concavo-convex to form warty, cancellous projection etc.But, if only processed by general gas soft nitriding, be difficult to form concavo-convex that cementability is fully improved, and all do not mention for its concrete method.In addition, for process the Fe-C-N based compound forming by gas soft nitriding, aspect the erosion resistance of himself, in the such purposes of the backing metal of brake facing, be also inadequate.In addition, by general gas soft nitriding, process in the nitride compound layer forming, usually form the defect that arrives diffusion layer from surface, thereby erosion resistance is brought to detrimentally affect.Owing to there being above-mentioned problem, so practical situation are: the application of gas nitriding in backing metal do not make progress as realistic problem.
On the other hand, in above-mentioned patent documentation 3, as the method that forms Fe-C-N based compound, used salt Bath Nitriding Treatment.Salt Bath Nitriding Treatment is different from the nitriding treatment of common use gas, easily on surface, is formed for guaranteeing the concavo-convex of adhesiveproperties.On the other hand, because be solid-liquid reaction, so the mother metal compositions such as Fe also carry out to the reaction of stripping in salt bath simultaneously.Therefore, the perforation defect that arrives diffusion layer is compared with using the nitriding treatment of gas, is easier to form.Thereby, in order to make the concavo-convex increase on surface and to compare with common salt Bath Nitriding Treatment, erosion resistance is improved, need to form magnetite layer on surface, can easily expect that this layer also needs quite thick thickness.
That is, in application salt Bath Nitriding Treatment in the situation that, especially aspect erosion resistance, be preferably formed thick zone of oxidation and defect is carried out to sealing of hole, by the method, can expect the raising of erosion resistance to a certain degree.But the intensity of Z 250 self is extremely low, if make zone of oxidation form thicklyer, thereby it is high in magnetite layer, to propagate the possibility that crack friction materials peels off.In addition, process and compare with gas nitriding, connect the more of defect, size is larger, therefore, and is not easy to carry out sufficient sealing of hole.Thereby, even form zone of oxidation as recorded in patent documentation 3, also cannot say necessarily and can obtain sufficient erosion resistance, therefore, can say practical method anything but.
On the other hand, also can study and use the good stainless steel of erosion resistance and its cementability is improved, or formation has the plating layer of intensity to a certain degree.But practical situation are that these methods remain the method that cost is high and be difficult to application.Therefore, strongly need to develop the technology that erosion resistance and cementability is taken into account by less expensive method.
The present invention is the invention completing in view of situation as above, and its object is to provide, and has steel work and the manufacture method thereof of excellent erosion resistance and cementability concurrently.
For solving the means of problem
In order bringing into play, to use nitriding treatment less expensive of gas and the advantage that erosion resistance is high, on steel, to form the upper layer that erosion resistance is higher and cementability is higher, carried out various research simultaneously.It found that: halogens is diffused to after the degree of depth more than surperficial 1 μ m of distance, in the gas atmosphere of carbonaceous sources not, carry out nitriding treatment, form thus nitride compound layer, as shown in Figure 1, this nitride compound layer comprises the first compound layer and the second compound layer, and this is two-layer and form, described the first compound layer be in nitrogen diffused layer side, form with Fe 3n is the layer of the epsilon structure of main body, and described the second compound layer is that in the face side of above-mentioned the first compound layer, to form and compare with the first compound layer nitrogen concentration higher and be formed with the heterogeneous layer of concave-convex surface.And, judge the nitride compound layer that comprises above-mentioned 2 layers and have high adhesion and erosion resistance concurrently, thereby completed the present invention.
In addition, also known: in the situation that to above-mentioned nitride compound layer form take the zone of oxidation that ferriferous oxide is main body situation, by the additional shot peening of particulate, unwanted nitride, oxide compound, oxynitride etc. on surface are removed, can further improve cementability and erosion resistance.
That is, will being intended to of steel work of the present invention, it is on the top layer of the mother metal as steel, to be formed with the steel work of nitride compound layer and nitrogen diffused layer,
Above-mentioned nitride compound layer comprises: the first compound layer forming in nitrogen diffused layer side and the second compound layer forming in the face side of above-mentioned the first compound layer,
Above-mentioned the first compound layer is with Fe 3n is the layer of the epsilon structure of main body,
Above-mentioned the second compound layer is that compare nitrogen concentration with the first compound layer higher and on surface, form irregular layer.
In addition, will being intended to of the manufacture method of steel work of the present invention, its surface to steel implements to make after the fluoridation of fluorine diffusion, and implement to make the gas nitriding that nitrogen spreads to process, thereby form nitride compound layer and nitrogen diffused layer on the top layer of mother metal, wherein,
Above-mentioned fluoridation comprises: limit imports fluorine source gas to processing in stove, limit makes the operation of fluoridizing that fluorine reacts with steel, with under the state of supply that stops fluorine source gas, keep heating, the fluorine that makes to be soaked in above-mentioned steel surface at least diffuses to the diffusing procedure of the degree of depth more than 1 μ m
In above-mentioned gas nitriding treatment, utilize the not gas atmosphere of carbonaceous sources to carry out reduction and the gasification of the fluorine composition after above-mentioned diffusion, and nitrogen is spread soak into form nitride compound layer and nitrogen diffused layer.
Invention effect
The above-mentioned nitride compound layer of steel work of the present invention comprises: the first compound layer forming in nitrogen diffused layer side and the second compound layer forming in the face side of above-mentioned the first compound layer.Above-mentioned the first compound layer is with Fe 3n is the layer of the epsilon structure of main body, and above-mentioned the second compound layer is that compare nitrogen concentration with the first compound layer higher and on surface, form irregular layer.
About above-mentioned the second compound layer, be formed with concave-convex surface, this concave-convex surface has the interrupted ditch portion of a plurality of prescribed depth.In addition, the nitride compound that by Fe-N is also forms to outside growth.In addition, by comparing with the first compound layer the nitride that nitrogen concentration is higher, form.Therefore,, even for example at adhesive friction material and to the large shear-stress of this friction materials load in the situation that, its surperficial concaveconvex shape is also difficult to destroyed.
In addition, the second compound layer of the formation concave-convex surface that is for Fe-N and the first compound layer forming in nitrogen diffused layer side especially, with the Compound Phase ratio of Fe-C-N system, erosion resistance is more excellent.In addition, the effect based on fluoridation and gas nitriding processing, becomes finer and close nitride compound layer, connects to the existence of the such defect of nitrogen diffused layer few from surface.Thereby, become the nitride compound layer that erosion resistance is extremely excellent.
In steel work of the present invention, in the situation that the concave-convex surface of above-mentioned the second compound layer has the degree of depth to high-density, be recess more than 0.5 μ m,
Complicated the concaveconvex shape more than degree of depth 0.5 μ m is formed at skin section, and it becomes the upper layer excellent in adhesion with friction materials etc.
In steel work of the present invention, in the situation that the surface nitrogen concentration of above-mentioned the second compound layer is more than 12 quality %,
By improving nitrogen, to the intrusion amount of skin section, make more than the surface nitrogen concentration of the second compound layer reaches 12 quality %, to form the nitride compound of high N concentration, thereby can promote the outside growth of nitride compound.Thereby the complicated concave-convex surface that becomes specific thickness forms and the upper layer excellent in adhesion of itself and friction materials etc. in skin section.
In steel work of the present invention, in the situation that the thickness of above-mentioned the second compound layer is more than 0.7 μ m,
By improving nitrogen, to the intrusion amount of skin section, make more than the thickness of the second compound layer reaches 0.7 μ m, to form the nitride compound of high N concentration, thereby can promote the outside growth of nitride compound.Thereby the complicated concave-convex surface that becomes specific thickness forms and the upper layer excellent in adhesion of itself and friction materials etc. in skin section.
In steel work of the present invention, in the situation that the thickness of above-mentioned the first compound layer is more than 5 μ m,
Nitride compound layer integral body becomes finer and close, connects to the existence of the defect of nitrogen diffused layer and becomes seldom, becomes the goods that erosion resistance is extremely excellent.
In steel work of the present invention, in the situation that the long-pending ratio of the real surface of surperficial per unit area is to be greater than 1.8 value,
Real surface for apparent surface is long-pending is long-pending very large, and the concavo-convex degree of concave-convex surface uprises just, thereby can guarantee reliably stable adhesiveproperties.
In steel work of the present invention, the zone of oxidation that ferriferous oxide is main body of take forming on the second compound layer below thickness 3 μ m is used as in outermost situation,
Can further improve erosion resistance.That is, for above-mentioned nitride compound layer, the concentration of the N of intrusion is also high, and particularly the nitride compound layer of a side of close nitrogen diffused layer becomes finer and close compound layer.Yet making to connect defect is not extremely difficult completely, and likely produces the rust as path.Therefore,, by being covered by zone of oxidation, can further improve erosion resistance.Based on the present invention and nitride compound layer possess: the erosion resistance of a) comparing nitride compound layer self with other nitriding method is higher, b) can on nitrogen diffused layer, form dense compound layer, c) easily become all few, such conditions favourable for erosion resistance of the quantity of perforation defect in generation source of rust and volume, therefore, only form the zone of oxidation below the thickness 3 μ m that do not hinder cementability, just become the major part of the perforation defect in nitride compound layer is carried out to sealing of hole and the very high upper layer of erosion resistance.Thereby, for example, in the situation that be applied to the backing metal of brake-shoe, can effectively prevent because there is peeling off of friction materials that corrosion causes.
In steel work of the present invention, in the situation that be present in perforation defect in the second compound layer, take the oxide compound that ferriferous oxide is main body and carried out sealing of hole,
Can further improve erosion resistance.That is, for above-mentioned nitride compound layer, the concentration of the N of intrusion is also high, and particularly the nitride compound layer of a side of close nitrogen diffused layer becomes finer and close compound layer.Yet making to connect defect is not extremely difficult completely, and likely produces the rust as path.Therefore,, by being carried out sealing of hole by zone of oxidation, can further improve erosion resistance.Based on the present invention and nitride compound layer possess: the erosion resistance of a) comparing nitride compound layer self with other nitriding method is higher, b) can on nitrogen diffused layer, form dense compound layer, c) easily become all few, such conditions favourable for erosion resistance of the quantity of perforation defect in generation source of rust and volume, therefore, only form the zone of oxidation below the thickness 3 μ m that do not hinder cementability, just become the major part of the perforation defect in nitride compound layer is carried out to sealing of hole and the very high upper layer of erosion resistance.Thereby, for example, in the situation that be applied to the backing metal of brake-shoe, can effectively prevent because there is peeling off of friction materials that corrosion causes.
For the manufacture method of steel work of the present invention, before gas nitriding is processed, implement to make halogens diffusion, soak into the halogenization processing to the degree of depth more than 1 μ m.Then, make this halogens and pass through NH 3the decomposition of gas and the reactive with active hydrogen that produces cause reduction reaction, thereby are vaporized.Then, carbonaceous sources not with NH 3gas is to carry out nitriding treatment under the atmosphere of main body.Thus, can form the nitride compound layer with following concave-convex surface, described concave-convex surface has interrupted ditch the portions more than a plurality of degree of depth 0.5 μ m.
The general nitride compound layer forming by nitriding treatment, has the as easy as rolling off a log carbon existing, the character of the carbon in base material of being accommodated in around.The carbon content of the nitride compound layer forming in the present invention on the other hand, is few.That is, do not become Fe-C-N system, and become the nitride compound layer of Fe-N system.Compare with the nitride compound layer that forms Fe-C-N system, the erosion resistance of the present invention that forms the nitride compound layer of Fe-N system becomes extremely excellent.
Owing to being easy to form the concavo-convex of surface, the situation of the surface treatment method that therefore use salt Bath Nitriding Treatment is used as backing metal is at present also a lot.Yet, in salt Bath Nitriding Treatment, with the compound of cyanogen system, carry out nitriding treatment, therefore, nitrogen is inevitable to spread with carbon simultaneously.Therefore, in the nitride compound layer on top layer, inevitably contain the carbon of high density, can judge this situation and for erosion resistance, play disadvantageous effect.
Therefore, in the present invention, adopt and use the not nitrogenize of carbonaceous sources to carry out nitriding treatment with gas.Thus, even contain carbon with high density to a certain degree in material, also can form the few and high nitride compound layer of erosion resistance of carbon content.That is,, in general nitriding treatment, carbon component contained in mother metal can not contain in nitride compound layer with keeping away.In the present invention, the reduction by the diffusion of the fluorine in fluoridation and fluorine composition thereafter, is activated surface, thereby N is more easily invaded.Surface after this activation, the active hydrogen that the decomposition by ammonia produces is promoted with the reacting of carbon that is present in nitride compound layer.By this reaction, carbon is removed in nitride compound layer with the form of hydrocarbon etc.
That is, by controlling the reduction of above-mentioned fluoridation and this fluorine composition, can form interrupted ditch portion and the concave-convex surface complex-shaped, cementability is high having more than a plurality of degree of depth 0.5 μ m.In the present invention, can be by the gas nitriding at the temperature of 600 ℃ of following left and right be processed and is formed above-mentioned concave-convex surface as basic surface treatment.Thus, the surface after fluorine composition is reduced becomes the state being activated, and the carbon concentration in nitride compound layer is reduced, thereby can form the nitride compound layer of the Fe-N system that erosion resistance is high.
In the manufacture method of steel work of the present invention, in above-mentioned fluoridation, repeat to fluoridize operation and diffusing procedure more than 2 times in the situation that,
Can make fluorine diffusion soak into the darker position of the skin section of steel, reduction and the gasification of fluorine composition are thereafter brought to very large impact, very heavy back forms the nitride compound layer that carbon concentration is low and erosion resistance is high.
In the manufacture method of steel work of the present invention, state on the implementation after gas nitriding processing,
On surface, form the oxide skin that ferric oxide is main body of take below thickness 3 μ m, thus the perforation defect that is present in nitride compound layer is carried out to sealing of hole, in the case,
Can further improve erosion resistance.That is, for above-mentioned nitride compound layer, the concentration of the N invading is also high, and particularly the nitride compound layer of a side of close nitrogen diffused layer becomes finer and close compound layer.Yet making to connect defect is not extremely difficult completely, likely produces the rust as path.Therefore,, by being carried out sealing of hole by oxide treatment, can further improve erosion resistance.Based on the present invention and nitride compound layer possess: the erosion resistance of a) comparing nitride compound layer self with other nitriding method is higher, b) can on nitrogen diffused layer, form dense compound layer, c) easily become all few, such conditions favourable for erosion resistance of the quantity of perforation defect in generation source of rust and volume, therefore, only form the zone of oxidation below the thickness 3 μ m that do not hinder cementability, just become the major part of the perforation defect in nitride compound layer is carried out to sealing of hole and the very high upper layer of erosion resistance.Thereby, for example, in the situation that be applied to the backing metal of brake-shoe, can effectively prevent because there is peeling off of friction materials that corrosion causes.
In the manufacture method of steel work of the present invention, state on the implementation after gas nitriding processing,
Implementing median size is the particulate shot peening below 100 μ m, and the unwanted nitride of covering outmost surface, oxide compound, oxynitride etc. are removed, and makes thus the concave-convex surface more than degree of depth 0.5 μ m expose, in the case,
Can make the bonding force of above-mentioned concave-convex surface further improve.That is, at the particle of the nitride forming by nitriding treatment, not when nitride compound layer is combined fully, or when concavo-convex by nitride, oxide compound, oxynitride covering surfaces, likely damage the adhesiveproperties of this part.Therefore, by implement shot peening under weak condition, can make concave-convex surface expose, make bonding force more stable.
Above-mentioned shot peening is in order further to improve cementability and the processing of adjustment sheet surface state, can not remove by oxide treatment and will connect the part of defect sealing of hole.Thus, do not damage the erosion resistance improving by implementing oxide treatment, can improve cementability.
As mentioned above, steel work of the present invention and manufacture method less expensive are treated to main surface treatment method with gas nitriding by using, for example, can form the cementability making in the bonding situation of friction materials high and be extremely difficult for producing the upper layer of rust.Therefore, such as in the situation that be applied to the backing metal etc. of brake-shoe, through long-time, friction materials is not also peeled off, and becomes the goods of excellent in te pins of durability.
Accompanying drawing explanation
Fig. 1 means the schematic diagram of the nitride compound layer of steel work of the present invention and the layer structure of nitrogen diffused layer.
Fig. 2 mean measure embodiment with the N concentration of the skin section of comparative example 1 must the figure of result.
Fig. 3 means the figure of embodiment and the surface of comparative example 1,2 and the SEM observations of section.
Fig. 4 be to embodiment and comparative example 2 measure surface shapes and measurement result.
Fig. 5 means the figure as the surperficial SEM observations of the C2-2 of embodiment and C2-3.
Embodiment
Next, illustrate and be used for implementing mode of the present invention.
The steel work of present embodiment is on the top layer of the mother metal as steel, to be formed with the steel work of nitride compound layer and nitrogen diffused layer.
Above-mentioned nitride compound layer comprises: the first compound layer forming in nitrogen diffused layer side and the second compound layer forming in the face side of above-mentioned the first compound layer.
Above-mentioned the first compound layer is with Fe 3n is the layer of the epsilon structure of main body, and above-mentioned the second compound layer is that compare nitrogen concentration with the first compound layer higher and on surface, form irregular layer.
The manufacture method of the steel work of present embodiment is after fluoridation that fluorine spreads is implemented to make in surface to steel, enforcement is processed the gas nitriding of nitrogen diffusion, thereby on the top layer of mother metal, forms the manufacture method of the steel work of nitride compound layer and nitrogen diffused layer.
Above-mentioned fluoridation comprises: limit imports fluorine source gas to processing in stove, limit makes the operation of fluoridizing that fluorine reacts with steel, the fluorine that makes to soak at above-mentioned steel surface with keep heating under the state of supply that stops fluorine source gas at least diffuses to the diffusing procedure of the degree of depth more than 1 μ m
In above-mentioned gas nitriding treatment, utilize the not gas atmosphere of carbonaceous sources to carry out reduction and the gasification of the fluorine composition after described diffusion, and make nitrogen diffusion soak into form nitride compound layer and nitrogen diffused layer.
As mentioned above, the fluoridation that the diffusing procedure of operation and fluorine is fluoridized in application to steel surface can form dark fluorinated layer in the situation that not making surperficial fluorine concentration increase excessively.And, by carbonaceous sources not with NH 3for the gas nitriding of main body, process, form nitride compound layer.Thus, in nitrogen diffused layer side, form the first compound layer that connects the Fe-N system that defect is few, in face side, be formed with the second compound layer of concave-convex surface.Thus, can be made into the steel with cementability and the two equal excellent upper layer of erosion resistance.And, such as can be well using as backing metal of the brake facing of excellent in te pins of durability, brake-shoe, clutch plate etc. etc.
Present embodiment can be applicable to carbon steel, low alloy steel, high quality steel, for structure, rolled iron, high tension steel, steel for mechanical structure, carbon tool steel, alloy tool steel, high speed tool steel, bearing steel, spring steel, converted steel, nitriding steel, stainless steel, high temperature steel, casting forged steel etc. can form the various steel of nitride compound layer.Wherein, can preferably use rolled iron, high tension steel etc. for structure to use as the backing metal of brake facing, brake-shoe, clutch plate etc.
For above-mentioned steel, first carry out halogen processing.
By this halogenization, process and the surperficial oxidation overlay film of object being treated is removed, forming halogen layer simultaneously.In addition, the dehalogenate element of the halogenic ingredient reduction in this halogen layer is processed and nitriding treatment by carrying out, thereby nitrogen spread from the surface of object being treated, soaked into formation nitride compound layer and nitrogen diffused layer.
As above-mentioned halogenization, process, can enumerate fluoridation, chloridized, bromination processings, iodate processing etc., it is easy and in the industrial fluoridation that is easy to utilization preferably to dispose.
For above-mentioned fluoridation, for example, at NF 3in the fluorine source gas atmosphere that gas etc. comprise fluorine and/or fluorine cpd, at 200～600 ℃, keep heating specific time, the oxidation overlay film of steel surface is removed, form the fluorinated layer that comprises fluorochemical.
Now, iff in order to carry out nitriding treatment, need only the fluorinated layer forming less times greater than the degree at the formed oxidation overlay film of steel surface thickness.That is, if oxide film thereon is replaced into fluorochemical, be fully, particularly, form less than 1 μ m, mostly in situation, forming than its thinner fluorinated layer.
On the other hand, in the present embodiment, form the layer that soaks into of 1 μ m fluorochemical above, more preferably 1.5～4.5 μ m left and right and fluorine.By fluorine is soaked into so dark, thereby for example comprising NH thereafter 3while heating under the atmosphere of gas, because of NH 3the decomposition of gas and the active hydrogen and the fluorine that produce react, and gasify, and can form the concave-convex surface with a plurality of interrupted ditch portions.
Now, utilize NH 3gas also carries out nitriding treatment concurrently, carries out formation and the nitriding treatment of concave-convex surface simultaneously, thereby becomes processing more efficiently.By such processing, can form the nitriding treatment layer that comprises nitride compound layer and nitrogen diffused layer.Above-mentioned nitride compound layer comprises the first above-mentioned compound layer and the second compound layer and forms.
For the concave-convex surface of the second compound layer, preferably make the concave-convex surface to high-density with the recess more than degree of depth 0.5 μ m, more preferably more than 1 μ m and below 5 μ m.If this is because the degree of depth of concave-convex surface is excessively shallow, cannot obtain the cause of required adhesiveproperties.On the contrary, be due to following cause: if the degree of depth of concave-convex surface is excessively dark, die down with the bonding force of the first compound layer, peel off etc., thereby the danger that exists adhesiveproperties to decline.It should be noted that, for the recess more than above-mentioned degree of depth 0.5 μ m, more than preferably there are 2 places in every 50 μ m length (nominal length) on surface, more preferably there are 3 places more than.
At this, the concentration of the fluorine source gas using in fluoridation is adjusted to suitable concentration according to material of object being treated etc.At this, if the fluorine concentration on object being treated surface becomes too high, the part of generating gasification becomes too much during nitriding treatment, the surface element generation powder of nitride compound layer and cause cementability easily deteriorated.Therefore, the fluorine concentration on the object being treated surface before nitriding treatment operation is preferably made as below 60 quality %, is more preferably made as below 50 quality % left and right.
Thereby, with regard to the surface treatment method in the present invention, in order not make the fluorine concentration on object being treated surface extremely increase, and make fluorine soak into deeplyer, and be provided with the diffusing procedure of fluorine.That is, in fluoridation, arrange: fluoridize operation, to processing, in stove, pass into certain hour fluorine source gas and object being treated and fluorine are reacted; And diffusing procedure, stop the supply of fluorine source gas, keep heating certain hour, thereby promote the diffusion of fluorine, and the fluorine concentration of adjustment sheet face.Thus, can not make the fluorine concentration on object being treated surface exceedingly increase, and form the layer that soaks into of deep fluorine.
At this, above-mentioned fluoridation preferably repeats 2 times and fluoridizes above operation and diffusing procedure.This is due to following cause: the velocity of diffusion of the fluorine in steel is very slow, and therefore, in the situation that surperficial fluorine concentration occurs exceedingly to rise, by diffusion, its concentration being reduced needs for a long time, and efficiency can variation.
Specifically, more preferably use more than 200 ℃, preferably more than 300 ℃, more preferably at more than 400 ℃ temperature, be divided into the method for supplying with for several times fluorine source gas.Like this, by repeating to fluoridize operation and diffusing procedure, can make the fluorine concentration on object being treated surface not excessively increase, and form the layer that soaks into of deep fluorine.
If 200 ℃ of the temperature less thaies that comprises above-mentioned fluoridation of fluoridizing operation and diffusing procedure, the velocity of diffusion of fluorine is slow, in order to form fluorinated layer more than 1 μ m, need long-time, productivity variation.On the other hand, if the temperature of fluoridation surpasses 600 ℃, the velocity of diffusion of fluorine rises, and on the other hand, the speed of response of fluorine and steel exceedingly rises, and becomes and is difficult to control the fluorine concentration of material surface.Thereby, more than the temperature of above-mentioned fluoridation is preferably made as 200 ℃ and below 600 ℃.
In above-mentioned fluoridation, if make the degree of depth less than 1 μ m of fluorine diffusion, the concavo-convex height forming on surface becomes insufficient, cannot improve fully the bonding force with friction materials etc.On the other hand, if the depth of penetration of above-mentioned fluorine is greater than 5 μ m, the gas escaped quantity on surface becomes too much, and it is fierce that the porous on surface becomes, and it is easily destroyed that concaveconvex shape becomes, and easily cause powder.Thereby, in above-mentioned fluoridation, make the degree of depth of fluorine diffusion be preferably made as 1 μ m more than and below 5 μ m.
For the time of fluoridizing operation and diffusing procedure, according to the suitably settings such as machining state on material, surface.If treatment time less than 1 minute, is difficult to fluorine is soaked into fully.Otherwise if be greater than 120 minutes, the fluorine concentration of the depth of penetration of fluorine and surface element easily becomes superfluous, also variation of production efficiency in addition.Thereby, the treatment time of fluoridation be preferably made as 1 minute above and below 120 minutes.
Above-mentioned fluoridation can also be implemented in the stove that carries out nitriding treatment, also can in stove separately, implement fluoridation and nitriding treatment.In addition, also fluoridation chamber and nitriding treatment chamber can be set respectively in identical stove and implement to process.Now, fluoridation and nitriding treatment are preferably separately implemented in different stoves or in room.This is because following cause: thus, be easy to control the fluorine concentration of material surface and the depth of penetration of fluorine.
Implement after above-mentioned fluoridation, implement nitriding treatment.
Nitriding treatment is by comprising NH 3etc. steel work after fluoridation being kept heating and is carried out in the atmosphere gas of source gas in nitridation.
By above-mentioned nitriding treatment, can form the nitride compound layer of the second compound layer that is included in the first compound layer that nitrogen diffused layer side forms and forms in the face side of above-mentioned the first compound layer.Above-mentioned the first compound layer is with Fe 3n is the layer of the epsilon structure of main body, and above-mentioned the second compound layer is that compare nitrogen concentration with the first compound layer higher and on surface, form irregular layer.
It is high N concentration more than 12 quality % that above-mentioned the second compound layer is preferably made as surface nitrogen concentration.Thus, the second compound layer can become the layer that is formed with concave-convex surface and has given play to adhesiveproperties.Second compound layer with such concave-convex surface forms as described below: by fluoridation layer is carried out to defluorinate processing, make concavo-convex formation, along the protuberance forming thus, make nitride carry out outside growth, thereby form.The second compound layer now forming be contain a great deal of, with the compound layer of the less nitride compound of the first compound layer phase specific mass, its result, can think and become the compound layer with complicated concaveconvex shape that adaptation is higher.
The concave-convex surface of above-mentioned the second compound layer is preferably made as the concave-convex surface to high-density with the recess more than degree of depth 0.5 μ m.This is due to following cause: if the degree of depth deficiency of concave-convex surface 0.5 μ m likely cannot obtain enough adhesivepropertieies.
The condition optimization of nitriding treatment so that the mode that becomes more than 12 quality % of nitrogen concentration on surface set.This is due to following cause: by will be by NH 3decomposition and the active N that produces near surface high density supply with, thereby promote Fe in the mode that attracted by this N from internal divergence to surface element.On the other hand, if make surperficial nitrogen concentration raise too highly, easily cause the reduction of the toughness on the second compound layer surface, therefore preferably surperficial nitrogen concentration is made as below 20 quality %.
In addition, more than the thickness of above-mentioned the second compound layer is preferably made as 0.7 μ m, more than being more preferably made as 1 μ m.If the thickness deficiency of the second compound layer 0.7 μ m, is difficult to improve significantly bonding strength.On the other hand, if the thickness of the second compound layer is greater than 5 μ m, the layer thickening and embrittlement occurs that nitrogen concentration is high, likely causes bonding strength to reduce on the contrary.Thereby, more than preferably the thickness of the second compound layer being made as to 0.7 μ m and below 5 μ m.
Preferably that the real surface of surperficial per unit area is long-pending than being made as the value that is greater than 1.8.This is due to following cause: by forming above-mentioned concave-convex surface, thereby make the real surface of per unit area amass increase, make thus bond area increase, thereby improve cementability.The long-pending numerical value than referring to that the long-pending value of real surface obtains divided by the long-pending value of apparent surface of real surface of per unit area.
Above-mentioned real surface is long-pending amasss ratio as measured by the device that 3 D surface shape is analyzed with real surface.In addition, can measure the length of the jog in certain section, utilize with the real surface of recently calculating of slant range and amass ratio.In addition, can take 3D image, by this photographic images, be obtained.
If above-mentioned real surface is long-pending than being below 1.8, cannot expect the significantly raising of surperficial adaptation.On the other hand, if real surface is long-pending, than being greater than 5, above-mentioned second compound layer with concave-convex surface likely reduces with the intensity of being combined as the first compound layer of its bottom, the danger that exists on the contrary cementability to reduce.Therefore, preferably real surface is long-pending than for being greater than 1.8 and be the value below 5.In addition, make caking agent adhere to, be soaked in the whole region of convex-concave surface if also consider, more preferably this value is more than 2 and below 4.5.
Now, if nitriding treatment temperature lower than 450 ℃, the fluorine that soaked into reacts slack-off with the hydrogen of invading from steel surface, and the formation speed of the second compound layer is also slack-off, thereby makes productivity variation.Otherwise if be greater than 650 ℃, the growth of the second compound layer is too fast, extremely easily there is porous in the particularly skin section of the second compound layer, likely occurs the strength decreased of formed nitride compound and do not tolerate the situation of actual use.Thus, preferably above-mentioned nitriding treatment temperature is made as 450 ℃ above and below 650 ℃.More preferably more than nitriding treatment temperature is 500 ℃ and below 600 ℃.
By the time of above-mentioned nitriding treatment, thereby show the concave-convex surface as the distinctive surface shape of the present invention.That is, make soaked into fluorine and hydrogen react and gasify, and make the second compound layer along inside and outside growth.And, consider erosion resistance, be preferably made as for making the combination of the first compound layer and the second compound layer nitride compound layer growth be thickness 7 μ m above for the sufficient time.Particularly, also according to the material of used mother metal, determine, such as carbon steel, low alloy steel, high tension steel etc. if, be preferably made as 10 minutes above and 3 hours in.If treatment time less than 10 minutes, is difficult to form required nitride compound layer and surface shape.In addition, this is due to following cause:, enter into compound layer and only concerning it takes off charcoal, be also inadequate time for carbon contained in material.Otherwise, be due to following cause: even if be greater than the processing of 3 hours, in performance, also reach capacity, and cause productivity to reduce.
In addition, preferably make the thickness of above-mentioned the first compound layer form 5 μ m left and right.This is because form the cause of dense compound layer in mother metal one side that is formed on first compound layer on surface.
More than the nitride compound layer that makes the first compound layer and the combination of the second compound layer and obtain is preferably made as thickness 7 μ m, if the erosion resistance of considering, more preferably more than 8 μ m.On the other hand, if this thickness is greater than 25 μ m, comprise erosion resistance saturated in interior performance, and easily form thick porous layer on surface.Thereby, more than the thickness of nitride compound layer is preferably made as 7 μ m and below 25 μ m.If consider productivity in the scope that does not substantially reduce performance, more preferably the upper limit of thickness is made as below 20 μ m.
The nitrogenize gas using during as above-mentioned nitriding treatment, is made as not containing the gas that possesses the gas of carburizing.This is in order to form the nitride compound layer that erosion resistance is higher.Specifically, for example can exemplify and supply with only NH 3gas, NH 3gas and nitrogen, NH 3gas and hydrogen, NH 3the method of gas and nitrogen and hydrogen.
Follow above-mentioned nitriding treatment operation, can implement as required surface oxidation operation.
By above-mentioned surface oxidation operation, form and to using oxide skin that ferriferous oxide is main body as outermost layer below thickness 3 μ m.The object of this oxide treatment operation is, by above-mentioned oxide compound, the perforation defective part of nitrogen diffused layer connecting to being present in the lower floor of nitride compound layer carried out to sealing of hole.The method is not particularly limited, such as adopting the nitriding treatment that continuing in the atmosphere containing oxidation source gas such as aerobic or water vapour to keep the method being oxidized under heating condition.In addition, can be the method being oxidized in refrigerating work procedure, can also be the first cooling method that then keeps heating to be oxidized once again.
The outmost surface portion that utilizes method of the present invention to carry out the steel after nitriding treatment becomes and has micron-sized concavo-convex complicated shape, the perforation defect of the first compound layer forming in nitrogen diffused layer side is fewer, thus, even if do not implement so strong oxide treatment, also can easily carry out sealing of hole.Thereby, even by utilizing the oxide treatment of the short period of time of refrigerating work procedure, also can improve fully erosion resistance.
More particularly, in the temperature of processed product, since the temperature of 600 ℃ of left and right, be reduced to 200 ℃ of left and right during, by utilization, exist the atmosphere of the oxidation source gas such as oxygen and/or water vapour to carry out cooling, thereby can be easy to make erosion resistance to improve.Can also in lower temperature province, implement oxide treatment, but in this case, need the time to a certain degree.Thereby, preferably by more than 450 ℃ temperature, be exposed to and comprise above-mentioned oxidation source gas 3 capacity % below, more preferably comprise in the atmosphere below 1 capacity %, thus form below 3 μ m with Fe 3o 4oxide skin for main body.
If above-mentioned oxide skin is greater than 3 μ m,, for example making friction materials bonding and applied shear-stress in the situation that, produce and destroy, easily cause thus peeling off of friction materials in the low oxide skin of intensity.Thereby, preferably the thickness of formed oxide skin is made as below 3 μ m, more preferably below 1.5 μ m.The method, can carry out forming required oxide skin in the cooling time of object being treated if, thus, also excellent aspect productivity.In addition, in the situation that forming above-mentioned oxide skin, in order to bring into play this effect, more than preferably its thickness being made as to 0.2 μ m.
In the present embodiment, after gas nitriding is processed, can implement particulate shot peening as required.
Particulate shot peening is that to utilize median size be the shot peening that the particulate below 100 μ m carries out, and can follow gas nitriding and process to carry out, and the oxide treatment that also can follow after gas nitriding is processed is carried out.Thus, the unwanted nitride of covering outmost surface, oxide compound, oxynitride etc. are removed, the concave-convex surface more than degree of depth 0.5 μ m is exposed.
; the object of above-mentioned oxide treatment is for carrying out sealing of hole by perforation defect as described above; therefore; after oxide treatment; sometimes further to its surface, give fine concaveconvex shape, or have the part that is formed with unwanted particle, nitride, oxide compound, oxynitride etc. in the mode on covering convex-concave surface.Under these circumstances, such as the additional median size of using, be the shot peening that 100 μ m are following, be preferably pressure particulate, 0.1～0.4MPa left and right such as granulated glass sphere below 70 μ m or ceramic particle.Thus, by these particles, nitride, oxide compound, oxynitride etc. are removed, thereby can become the condition of surface that cementability is higher.
As mentioned above, on the surface of steel work, form have concave-convex surface and with the second compound layer of the adaptation excellence of the first compound layer, form the high upper layer of cementability.In addition, the first compound layer in the high Fe-N system of the few erosion resistance of mother metal side formation perforation defect, also improves erosion resistance.In addition, in the situation that additional formation does not hinder and the oxide treatment operation of the thin zone of oxidation of the cementability of friction materials etc., the shot peening operation of adjusting for effects on surface state, can, by the perforation defect sealing of hole of a little existence in nitride compound layer, form the higher surface-treated layer of erosion resistance.
Thus, the deteriorated erosion resistance being suppressed that formed surface-treated layer becomes high and its cementability of cementability in surface shape is excellent processing layer also.For utilizing treatment process of the present invention, carried out surface-treated steel work, such as bonding backing metal of the friction members such as the brake facing by being applied to use, brake-shoe, clutch plate etc., thereby become the structural member with excellent weather resistance in automobile etc.
Next, embodiment is described.
Embodiment 1
As the steel for testing, prepared as the SS400 of rolled sheet material for general structure, as the SAPH440 of hot-rolled steel plate for vehicle structure, SPFH590 as automobile with processibility hot rolling high-tensile steel.
Embodiment: be heated in the stove by the test film of above-mentioned 3 kinds of steel grades in nitrogen atmosphere after 400 ℃, supply with nitrogen dilution and the NF of the 10 capacity % that obtain in stove 3gas is implemented the operation of fluoridizing of 5 minutes simultaneously.Then, stop NF 3the supply of gas, implements the fluoridation of the diffusing procedure of 15 minutes.Then, be heated to 500 ℃, to the NH that supplies with 70 capacity % in stove 3the H of gas and 30 capacity % 2gas is implemented the reduction (that is, defluorinate is processed) of the fluoridation layer of 20 minutes simultaneously.Then, be warming up to 550 ℃, to the NH that supplies with 70 capacity % in stove 3the N of gas and 30 capacity % 2gas is implemented the nitriding treatment of 60 minutes, is cooled to room temperature in nitrogen atmosphere.It should be noted that, for only implementing, above-mentionedly just under nitrogen atmosphere, carry out cooling test film after fluoridizing operation and diffusing procedure, investigate the thickness of fluorinated layer, confirm that arbitrary test film is all formed with the fluorinated layer of 1.5～2.0 μ m.
Comparative example 1(use fluoridation in the past and nitriding treatment product): in the stove by the test film of above-mentioned 3 kinds of steel grades in nitrogen atmosphere, be heated to after 400 ℃, to supplying with nitrogen dilution in stove the NF of 2.5 capacity % 3gas is implemented the fluoridation of 20 minutes simultaneously.Then, be warming up to 550 ℃, to the NH that supplies with 70 capacity % in stove 3the N of gas and 30 capacity % 2gas, carries out the nitriding treatment of 60 minutes, at room temperature cooling in nitrogen atmosphere.It should be noted that, for having implemented, after above-mentioned fluoridation, carry out cooled test film under nitrogen atmosphere, investigate the thickness of fluorinated layer, the fluorinated layer of arbitrary test film is that 0.4～0.6 μ m is thick, confirms thinner than embodiment.
Comparative example 2(salt Bath Nitriding Treatment product): also prepared the SAPH440 to carry out at 570 ℃ after the salt Bath Nitriding Treatment of 40 minutes test film.
For above-mentioned test film, will its surface be analyzed and result and the surperficial rust area while carrying out temperature 60 C, humidity 80%, the moistening test of 100 hours in constant temperature and humidity cabinet be shown in following table 1.It should be noted that, specific surface area in table refers to respect to measuring area amasss increase by generating the concavo-convex real surface that makes on surface, and the real surface of for example, calculating when its actual surface-area is carried out to three-dimensional measurement (can use the fine surface-profile measuring instrument of the pan focus PLUS optical profile type processed 3D of Zeta Instruments company) amasss/measure the value of the ratio of area.
Table 1
Figure BDA0000445075960000171
As shown in Table 1, in an embodiment, any steel grade has all formed the low nitride compound layer of carbon concentration on surface.In addition we know,, for comparative example 1,2, there is very high surface nitrogen concentration.
Fig. 2 represent to the concentration distribution of the depth direction of the N of the outmost surface portion of the embodiment of SAPH440 material and comparative example 1 measure and result.Known: the nitrogen concentration that has formed in an embodiment approximately 2 μ m is greater than the part of 10 quality %, on the other hand, in comparative example 1, there is no and form part as described above.In addition, if observe the passing of the nitrogen concentration starting from the surface of embodiment, formed and can think that nitrogen concentration is the ε (Fe of 8 quality % left and right 3n) the first compound layer of phase and can think its top layer side have be greater than 11 quality % high surface nitrogen concentration contain ζ (Fe 2n) the second compound layer of phase.Form inclination that N concentration in each layer starts from surface slowly to reduce, so-called and form, the second compound layer is concave-convex surface layer, and high with the bonding force of the first compound layer below it, can think its be can the strong stress of load layer.
Fig. 3 is to embodiment and comparative example 1, the surface of comparative example 2 and the result that section carries out SEM observation.From this surface SEM photo, with micron order, formed in an embodiment the concave-convex surface of a plurality of ditch shapes.This surface SEM photo illustrates: for fluoridation method in the past, fluorine is only at surface enrichment, but by applying after this suitable DIFFUSION TREATMENT, then carry out reduction and the nitriding treatment of fluorochemical, thereby can form the concave-convex surface with a plurality of ditch portion.That is, by enforcement, comprise the fluoridation of diffusing procedure, thereby make fluorine soak into deeplyer, by making soaked into fluorine composition reduce, gasify, thereby form recess.By the part for convex residual, from invading N around, realize high N concentration, thereby promote the growth of the nitride of protuberance.Thus, from the section SEM photo of embodiment, formed the second compound layer is compared and can be seen obvious aberration with the first compound layer, from its dark this situation, is the layer of the light element that contains a great deal of.It illustrates: by surface-area, become greatly, thereby from invading N around, become high N concentration, form the heterogeneous nitride different from the composition of nitride in the first compound layer, and grow, thus, become the more complicated shape of concave-convex surface.Thus, with regard to embodiment, compare with comparative example 1,2, can think and form significantly the large concave-convex surface of value of specific surface area.
For the surface layer structure of the long-pending embodiment having increased significantly of this real surface, the increase effect by bond area becomes the extremely excellent surface shape of cementability.It should be noted that, the surface layer structure of this embodiment is not found large difference between 3 kinds of steel grades for testing, this means the steel grade for other, also can profit use the same method to form dark fluorinated layer and reduce, gasify, thereby forming same surface shape.
In the outmost surface portion of the section SEM photo of the embodiment of Fig. 3, confirm second compound layer with concave-convex surface that the nitride by this high N concentration forms.The existence of this second compound layer brings very large impact to cementability.
In addition, about erosion resistance, embodiment compares with comparative example 1,2, obviously more excellent.Can not think simply to form the cause of the nitride layer of the Fe-N system that carbon concentration is low, also demonstrating the first compound layer that the diffusion layer side at the second compound layer forms becomes and connects the extremely fine and close layer that defect is few.
On the other hand, for the salt-bath nitriding product of comparative example 2, from surperficial SEM photo, on surface, form the nitride of convex, thereby made to show roughness, specific surface area change greatly, improved bonding force.But from section SEM photo, the bonding state of the nitride of talkative this convex and the nitride under it is not good.Although confirm larger hole, can think and compare with the situation that is formed with a plurality of concave-convex surfaces as embodiment, the closing force while applying shear-stress etc. is not by a long sight.In addition, as mentioned above, observe larger hole, can think that the perforation defect connecting to nitrogen diffused layer is also many.Known, be not only the compound layer of Fe-C-N system, and compare with embodiment, be the layer that erosion resistance is on duty mutually.
Fig. 4 represents for embodiment and comparative example 2, use contactless determinator (the fine surface-profile measuring instrument of the pan focus PLUS optical profile type processed 3D of Zeta Instruments company), through approximately 100 μ m long (nominal length) measure surface shape and measurement result.Figure is from the viewed curve of section side.It should be noted that, comparative example 2 be the value of specific surface area large, as the salt Bath Nitriding Treatment product that generally adopt at present concerning the nitriding treatment of brake-shoe etc.Comparative example 2 is milder concave-convex surface shape, and on the other hand, ditch portion (recess) more than the degree of depth 0.5 μ m of embodiment at least take the high-density more than 2～3 places in every nominal length 50 μ m and exists.In addition, known forming has the large recess of difference of height and the complicated concaveconvex shape of protuberance in short interval.As can be known from the above results, in an embodiment, it is large that the value of specific surface area becomes, and bond area increases.And, also increase the anchoring effect of realizing based on there is ditch portions more than a plurality of 0.5 μ m in the short cycle.Thus, form the surface shape that cementability and adaptation are very excellent.
Embodiment 2
Use SPFH590 material, implement adaptation evaluation test.As the nitridation treatment method of test film, for test film, under the condition of table 2, implement fluoridation.That is, utilize with nitrogen dilution and the NF of the 10 capacity % that obtain 3gas is implemented fluoridizing after operation of specified time, stops NF 3the supply of gas, implements the diffusing procedure of specified time.
For Embodiment B 2, the diffusing procedure of fluoridizing operation and 5 minutes that utilizes aforesaid method to implement 2.5 minutes, then further implements the diffusing procedure of fluoridizing operation and 10 minutes of 2.5 minutes.
For Embodiment C 2, the diffusing procedure of fluoridizing operation and 2 minutes that utilizes aforesaid method to implement 1 minute, then implements the diffusing procedure of fluoridizing operation and 3 minutes of 1 minute, and then implements the diffusing procedure of fluoridizing operation and 5 minutes of 1 minute.
Then, by the first homogeneous heating to 400 ℃ of these test films, at the NH of 50 capacity % 3the N of gas and 50 capacity % 2in gas atmosphere, carry out the reduction of fluorinated layer and process, with 3 ℃/min, be warming up to 580 ℃ simultaneously.Then, at 580 ℃ to the NH that supplies with 100 capacity % in stove 3gas 30 minutes, implements nitriding treatment, and carries out cooling.For the fluorinated layer thickness after the fluoridation of each test film and surperficial fluorine concentration, be shown in the lump table 2.
Table 2
Figure BDA0000445075960000201
Result by the B2 in table 2, C2 is known, is being divided into implement fluoridation for several times in the situation that, can, in the rising that suppresses surperficial fluorine concentration, form thick fluorinated layer.
Utilize above-mentioned method to carry out nitriding treatment to these test films.Now, as Embodiment C 2-2, after the nitrogenize of C2 finishes, cooling containing carrying out in the nitrogen of aerobic 0.1 capacity %, produce the test film of the oxide skin that is formed with mean thickness approximately 1.0 μ m.In addition, as Embodiment C 2-3, produce use the ceramic particle of median size approximately 60 μ m under the pressure of 0.2～0.3MPa, the surface of the cooled test film of C2-2 to be projected and test film.
Test film for after processing under the condition at embodiment and comparative example, attaches the surface of 2 pieces of test films each other with caking agent respectively, implements the salt spray testing of the use 5%NaCl aqueous solution of 1000 hours, then implements above-mentioned bonding strength test.The results are shown in table 3.
It should be noted that, for the test film (salt Bath Nitriding Treatment product) of the comparative example 2 in embodiment 1, also implement same bonding strength test, be shown in Table 3 in the lump.
Table 3
Figure BDA0000445075960000211
As shown in Table 3, utilize the thickness of the second compound layer of method formation of the present invention to bring very large impact to bonding strength.And, known by its thickness is suitably changed, and can obtain high-adhesive-strength.That is, in the situation that making its thickness significantly lower than 1 μ m, cannot expect the raising of bonding strength, otherwise, blocked up in the situation that, also demonstrate bonding strength and reduce.
As shown in Table 2, the thickness of the second compound layer brings very large impact to the fluorine concentration of fluorinated layer thickness, this fluorinated layer.For a of the too small comparative example 1 of the thickness of the second compound layer, low with the adaptation of caking agent, therefore, easily promote to get rusty, its result, bonding strength is low.On the other hand, for the b of the blocked up comparative example 1 of the second compound layer thickness, especially can see that the adaptation of the nitride compound layer of convex portion and bottom reduces.This can think following cause: the ratio gasifying when fluorinated layer is reduced is many, so the strength decreased of jog, and then also reduces with the adaptation of caking agent, so rust area also increases, result, and bonding strength reduces.
On the other hand, for embodiment, knownly compare with comparative example 2, rust area, bonding strength are all excellent.Particularly utilize the method for fluoridizing operation and diffusing procedure and also they alternately being repeated is not only set implements this situation of fluoridation, can reach more excellent result.Can judge: the method that does not make surperficial fluorine concentration exceedingly rise fluorine is soaked into by application, thus can form erosion resistance and the more excellent upper layer of cementability.
In addition, from the result of Embodiment C 2-2 and C2-3, for the situation of having added oxidation operation, compare especially erosion resistance with C2 and be improved.Therefore, can think and extremely be difficult for causing the reduction of the bonding strength that the generation because of rust causes, all demonstrate the value of high-adhesive-strength.
Fig. 5 illustrates the surperficial SEM photo of Embodiment C 2-2 and C2-3.The more weak oxide treatment that only application does not make surface shape seriously destroy, just carries out sealing of hole by the perforation defect existing in nitride compound layer, is therefore the test film that demonstrates high corrosion resistance.In addition, carry out particulate shot peening, do not make surperficial concaveconvex shape havoc unwanted, the particle that is attached to surface, nitride, oxide compound, oxynitride etc. are removed with the formed part of mode covering on convex-concave surface.Thus, result demonstrates, and under the state of erosion resistance, to improve the possibility of bonding strength high maintaining.Thus, result demonstrates, and additional, the additional of particulate shot peening operation that carry out treatment process are preferred embodiments.
Known according to above result, the surface treatment method of steel of the present invention is less expensive with gas nitriding, to be treated to main surface treatment method, can form the buckle layer that cementability is high, and can form the nitride compound layer that erosion resistance is high at steel surface.Thereby, for carrying out the steel after surface treatment by surface treatment method of the present invention, for example can form cementability in the situation of adhesive friction material high and be extremely difficult for producing the upper layer of rust, thus, through being also difficult for causing for a long time the problems such as peeling off of friction materials, that is, can be used as the member of excellent in te pins of durability.
Utilizability in industry
The prepared steel work of manufacturing method according to the invention has all excellent upper layers of surperficial cementability and erosion resistance both sides, such as can be well as the backing metal of the brake facing of excellent in te pins of durability, brake-shoe, clutch plate etc. etc.It should be noted that, the scope of application of the present invention is not limited to this.If in the situation that need the environment of erosion resistance to need adhesiveproperties, can bring into play excellent performance in various uses.
Nomenclature
1 second compound layer
2 first compound layers
3 nitrogen diffused layers
4 mother metals

Claims (11)

1. a steel work, is characterized in that,
On the top layer of the mother metal as steel, be formed with nitride compound layer and nitrogen diffused layer, wherein,
Described nitride compound layer comprises: the first compound layer forming in nitrogen diffused layer side and the second compound layer forming in the face side of described the first compound layer,
Described the first compound layer is with Fe 3n is the layer of the epsilon structure of main body,
Described the second compound layer is to compare nitrogen concentration height in quality % with the first compound layer to the Fe that comprises that is greater than 11 quality % 2the layer of the ζ structure of N,
Described ζ structure layer surface be formed with concavo-convex.
2. steel work according to claim 1, wherein,
The concave-convex surface of described the second compound layer be take the high-density more than 3 places in the nominal length of at least every 50 μ m and is had the recess more than degree of depth 0.5 μ m.
3. steel work according to claim 1 and 2, wherein,
The thickness of described the second compound layer is more than 0.7 μ m.
4. according to the steel work described in any one in claim 1～3, wherein,
The thickness of described the first compound layer is more than 5 μ m.
5. according to the steel work described in any one in claim 1～4, wherein,
The long-pending ratio of real surface of the per unit area on surface is for being greater than 1.8 value.
6. according to the steel work described in any one in claim 1～5, wherein,
On the second compound layer, be formed with and using zone of oxidation that ferriferous oxide is main body as outermost layer below thickness 3 μ m.
7. according to the steel work described in any one in claim 1～6, wherein,
The perforation defect existing in the second compound layer be take the oxide compound sealing of hole that ferriferous oxide is main body.
8. a manufacture method for steel work, is characterized in that,
After fluoridation that fluorine spreads is implemented to make in surface to steel, implement to make the gas nitriding that nitrogen spreads to process, thereby form nitride compound layer and nitrogen diffused layer on the top layer of mother metal, wherein,
Described fluoridation comprises: limit imports fluorine source gas to processing in stove, limit makes the operation of fluoridizing that fluorine reacts with steel, with under the state of supply that stops fluorine source gas, keep heating, the fluorine that makes to be soaked in described steel surface at least diffuses to the diffusing procedure of the degree of depth more than 1 μ m
In described gas nitriding is processed, utilize the not gas atmosphere of carbonaceous sources to carry out reduction and the gasification of the fluorine composition after described diffusion, and make nitrogen diffusion soak into form nitride compound layer and nitrogen diffused layer.
9. the manufacture method of steel work according to claim 8, wherein,
In described fluoridation, will fluoridize operation and diffusing procedure repeats more than 2 times.
10. the manufacture method of steel work according to claim 8 or claim 9, wherein,
After implementing described gas nitriding processing,
On surface, form the oxide skin that ferric oxide is main body of take below thickness 3 μ m, will be present in the perforation defect sealing of hole of nitride compound layer thus.
The manufacture method of the steel work in 11. according to Claim 8～10 described in any one, wherein,
After implementing described gas nitriding processing,
Implementing median size is the particulate shot peening below 100 μ m, and the unwanted nitride of covering outmost surface, oxide compound, oxynitride etc. are removed, and makes thus the concave-convex surface more than degree of depth 0.5 μ m expose.
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