CN1809650B - Hot press-formed article and method for its manufacture - Google Patents

Hot press-formed article and method for its manufacture Download PDF

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Publication number
CN1809650B
CN1809650B CN200480017496.8A CN200480017496A CN1809650B CN 1809650 B CN1809650 B CN 1809650B CN 200480017496 A CN200480017496 A CN 200480017496A CN 1809650 B CN1809650 B CN 1809650B
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zinc
steel
iron
hot press
oxide film
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CN1809650A (en
Inventor
吉川幸宏
今井和仁
福井国博
土岐保
须藤俊太郎
尾林彰
市川正信
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Nippon Steel Corp
Toyoda Iron Works Co Ltd
Toyota Motor Corp
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Toyoda Iron Works Co Ltd
Sumitomo Metal Industries Ltd
Toyota Motor Corp
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Priority claimed from JP2003307348A external-priority patent/JP4506128B2/en
Application filed by Toyoda Iron Works Co Ltd, Sumitomo Metal Industries Ltd, Toyota Motor Corp filed Critical Toyoda Iron Works Co Ltd
Priority claimed from PCT/JP2004/005873 external-priority patent/WO2004094684A1/en
Publication of CN1809650A publication Critical patent/CN1809650A/en
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Abstract

The present invention provides a hot press formed product being improved in corrosion resistance and in the adhesion of a coating film, which is produced by subjecting a zinc-based metal plated steel product to a hot press forming, and has a zinc-based metal plating layer containing and, formed thereon, a zinc oxide layer, wherein the uppermost zinc oxide layer has an average thickness of 2 mum or less; and a hot press formed product being excellent in corrosion resistance, the adhesion of a coating film, the resistance to corrosion after coating, and weldability, which has a basis steel plate (1) and, formed thereon, a layer (2) consisting essentially of an iron-zinc solid solution phase and, as the uppermost layer, a zinc oxide layer (3) having an average thickness of 5 mum or less, andhas substantially no iron-zinc intermetallic compound phase, wherein the iron-zinc solid solution layer (2) and the zinc oxide layer (3) contain Al in a total amount of 0.5 g/m<2> or less and/or contain Al oxides in a total amount of 5 mg/m<2> or less in terms of Al.

Description

Hot press-formed article and manufacture method thereof
Technical field
The present invention relates to the hot press-formed article and the manufacture method thereof of the steel of high strength and spraying back solidity to corrosion and spraying associativity excellence.Hot press-formed article of the present invention and manufacture method thereof are specially adapted to the running gear of so-called automobile and the manufacturing that reinforcement requires high strength and corrosion proof parts.
Background technology
In recent years, turn to purpose with light weight, realize the high strength of steel plate, constantly make progress and employed steel plate is carried out light-weighted effort for the fuel rate of utilization that improves automobile.But,, then by hot press-formed making trolley part the time, will take place to scratch and the steel fracture, and understand the shape problem of unstable that occur molding because of rebound phenomenon if the intensity of steel plate uprises.
Technology as making high-strength parts is high tensile steel plate not to be carried out drawing, and carries out drawing with low intensive state, quenches after drawing and improves the method for intensity.At this moment, the steel composition with steel plate is chosen as and can quenches.
Other technologies are the hot stamping technology of carrying out drawing by the heating steel plate.In hot stamping, because make the steel plate low strengthization, so even the higher steel plate of the strength ratio under the normal temperature also can not make the problems referred to above take place and carries out drawing by heating.
By combined quench in hot stamping, also can further realize the high strength of member.Be about to have the steel plate that the steel that can quench forms and be heated to quenching temperature, hot press-formed in this temperature, and in press tool, or after drawing chilling and quenching.Thus, compare, can make more high-intensity molding with only adopting the situation of quenching or hot stamping.For this reason, generally in hot stamping, quench.If in press tool, quench, then after drawing, be not intended to the thermal treatment of quenching, promptly can side by side realize being shaped and quenching.Reference example such as spy open the 2002-102980 communique.
Because hot press-formed is the manufacturing process of processing heating back steel plate, so the oxidation of inevitable surface of steel plate.For example, even the steel plate that heats in non-oxidizing atmosphere is taking out from process furnace and is carrying out between the punching press, because of touching atmosphere, and at the oxide compound of the surface of steel plate formation iron.And, added cost heat gain in this non-oxidizing atmosphere.
The ferriferous oxide that surface of steel plate forms comes off when punching press and is attached to mould, has hindered productivity, and remaining in the molding after drawing have the epithelium that is made of this ferriferous oxide (below, abbreviate the iron-oxygen scale film as), influences outward appearance.And, if remaining this kind iron-oxygen scale film in molding, then because the associativity on iron-oxygen scale film and molding surface is poor, so carry out chemical transformation in following operation handles and sprays if do not remove the iron-oxygen scale film, then spray associativity problem can take place, therefore the solidity to corrosion after the spraying reduces.
Therefore, the 6th invention institute record of opening the 2003-2058 communique as the spy before the spraying hot press-formed article, by sandblasting or the surface of shot peening cleaning molding, is removed surperficial iron-oxygen scale film usually., this hydro-peening is handled comparatively numerous and diverse, and the productivity of hot stamping is significantly reduced.And, might in molding, produce strain.
On the other hand, generation for the ferriferous oxide that suppresses to cause by the oxidation of surface of steel plate, and after shaping, also has a solidity to corrosion, open the technology that has proposed the hot stamping zinc-based metal plated steel sheet in 2001-353548 communique and the Te Kai 2003-73774 communique the spy, having proposed hot stamping aluminium in the 2000-38640 communique is the technology of steel plating plate.
But, be under the situation of steel plating material at hot stamping aluminium, when steel heat, produce the phase mutual diffusion between coating and the steel substrate, generate the intermetallic compound of Fe-Al and Fe-Al-Si at the coating interface.Because this intermetallic compound, under the hot stamping temperature,,, and then diminish the outward appearance of molding so when continuous molding, can damage hot stamping with the plating mould than coating hard more.
In addition, be in the hot stamping of steel plating material at aluminium, generate the oxide scale film of aluminium during heating at coating surface.The oxide scale film of this aluminium is though unlike the oxide scale film of iron, in the problem that still can spray associativity, may not satisfy automobile exterior panel, the running gear spraying associativity with desired strictnesses such as members.In addition, be difficult to form widely used chemical transformation processing epithelium as spraying base treatment.
On the other hand, be under the situation of steel at hot stamping zinc, form iron-zinc (Fe-Zn) intermetallic compound by the mutual diffusion mutually of coating and steel mother metal.Because this intermetallic compound is similarly hard, so still can damage the hot stamping mould.Perhaps, if insufficiently make pure zinc mutually residual, then because the fusing point specific heat press temperature of zinc is low, so in hot stamping, also can pollute mould sometimes because of fused zinc disperses because of heating.
In the spy opens the zinc-based metal plated steel sheet that proposed in the 2003-73774 communique hot press-formed, by the heat treated heating of for example alloying, and be the surface of coating at the zinc of steel plate, be pre-formed zinc oxide film.The zinc oxide film on this steel plating plate surface, in hot press-formed and prior adding pine for having as preventing that zinc from being the effect of the barrier layer of coating evaporation., in this communique,, do not mention the existence and the effect thereof of any relevant surface oxidation zinc layer for by hot press-formed molding.The thickness of the oxide scale film that plays a role (being zinc oxide film) is that about 0.01~5.0 μ m is just very abundant though put down in writing as the barrier layer, but, the barrier layer is put in the evaporation of the zinc when its conduct prevents hot stamping, therefore be the thickness that is heated to the zinc oxide film on the zinc-based metal plated steel sheet surface before the hot stamping temperature, rather than the thickness of the zinc oxide film on the molding surface that obtains by hot stamping.
The hot press-formed article of zinc-based metal plated steel sheet sprays after shaping mostly and uses as parts.This sprays parts, compares with the parts that hot press-formed article to naked steel plate sprays, and generally shows the further solidity to corrosion of having improved.
Open among the embodiment of 2003-73774 communique the spy, solidity to corrosion after the spraying of the hot press-formed article of zinc-based metal plated steel sheet is tested.Specifically, the situation that the expansion amplitude in 480 hours salt spray testings is lower than 4mm is judged as " spraying back solidity to corrosion is good ".
, improve year by year spraying the corrosion proof required standard in back, according to the kind of parts, above-mentioned judgment standard becomes insufficient.Particularly, can enumerate the car body outside plate, running gear member etc. as requiring to spray the higher parts of back solidity to corrosion.
Therefore, in the hot press-formed technical field of zinc-based metal plated steel sheet, aspire for stability and the manufacturing of high productivity ground, except that high strength, the spraying associativity is good, the molding that spraying back solidity to corrosion is further improved.In addition, if require outward appearance good, then assemble by spot welding mostly or install, so also require spot weldability good because of hot press-formed article.
Summary of the invention
In first mode of the present invention, be high strength and spraying back solidity to corrosion and the excellent hot press-formed article of spraying associativity, it is characterized in that, more than steel surface is with 1 μ m and the thickness below 50 μ m to have the zinc that contains iron-zinc solid solution phase be coating, do not have zinc oxide film at an upper portion thereof in fact, perhaps with mean thickness below 2 μ m and exist.This hot press-formed article, can be zinc-plated by hot stamping be that steel obtain.
The zinc that comprises iron-zinc solid solution phase is coating, also can in fact only be made of iron-zinc solid solution phase.The zinc that is present in surface of steel plate is that the total zinc amount in coating and the zinc oxide film is preferably 10g/m 2More than and at 90g/m 2Below.
In hot stamping, usually with steel, be typically steel plate, be heated to 700 ℃~1000 ℃ and drawing.For this reason, on the surface of the molding that the zinc-based metal plated steel sheet hot stamping is obtained, form the oxide scale film (being zinc oxide film) of quite thick zinc.And distinguished that formed thick oxide scale film has a negative impact to spraying the back solidity to corrosion in this hot stamping.
In addition, in the hot stamping operation of reality, the surface of steel plate before punching press has operator's sebum and the situation that sweat adheres to.If carry out hot stamping, and implement spraying thereafter, the spraying associativity local extreme ground deterioration of then described sebum and sweat attachment portion with this state.At this moment, the thickness of the oxide scale film after the drawing of attachment portions such as described sebum and sweat is than other part thickenings.
By the zinc oxide film that the surface produced of the hot press-formed article of zinc-based metal plated steel sheet is removed fully by processing such as shot-peenings or its mean thickness is reduced to below the 2 μ m, can stablize and improve the spraying associativity of hot press-formed article.As a result of, spraying back solidity to corrosion is also good.
The hot press-formed article of the first above-mentioned mode, can make by the method that comprises following operation, promptly to zinc-plated be that steel carry out hot press-formed operation, thereafter the mean thickness for the zinc oxide film on the top layer that makes resulting molding becomes below the 2 μ m, and with the operation of partly or entirely removing of this oxidation film layer.Hot press-formed operation, the zinc that resulting molding is possessed comprise iron-zinc solid solution layer be coating with and on zinc oxide film (oxide scale film) mode and carry out.
Removing the operation of zinc oxide film also can be undertaken by shot-peening and/or liquid honing.When using the shot-peening method, preferably be that 100~500 μ m steel balls use as the ball bullet with average particulate diameter.
In second mode of the present invention, be that high strength and outward appearance are good, spraying back solidity to corrosion and spraying associativity excellence, the hot press-formed article of good weldability in addition, it is characterized in that, have the zinc oxide film as the superiors, constitutionally has the iron-zinc solid solution layer that is formed by iron-zinc solid solution phase under it, but does not comprise the layer of the iron-zinc intermetallic compound of real mass.The mean thickness of zinc oxide film is below the 5 μ m.Iron-zinc solid solution layer, preferred mean thickness is 10~40 μ m.The total amount of contained Al is 0.5g/m in iron-zinc solid solution layer and the zinc oxide film 2Below, perhaps in these layers as the total content of the Al of Al oxide compound at 5mg/m 2Below.
The hot press-formed article of above-mentioned second mode can be made by the method that includes following operation, be about to steel be heated to the heating process of fixed temperature and and then heating process with the stamping procedure of steel with high temperature drawing like this.Steel are, (1) Al content is the following molten zinc plating steel of 0.35 quality % or the galvanized steel of alloying, and perhaps the Fe content in (2) electro-galvanizing steel or the coating is the following plating zn-fe alloy steel of 20 quality %.The coating adhesion amount of these steel platings is 40g/m 2More than and at 80g/m 2Below.In heating process, after in oxidizing atmosphere, steel being warmed up to 850 ℃~950 ℃ temperature range from room temperature with the V-bar below 15 ℃/second, in this temperature range, keep more than 30 seconds, and described heating-up time and described hold-time add up to more than 3 minutes and below 10 minutes.In stamping procedure, in 700 ℃~950 ℃ temperature range, steel are carried out drawing.
The hot press-formed article of second mode because by the zinc oxide film of the superiors and be present under it the iron that is formed by iron-zinc solid solution phase in essence-the zinc solid solution layer is covered, so corrosion resistance excellent.In addition, the zinc oxide film associativity excellence on top layer also is difficult for during drawing peeling off, because there is not the layer of the iron-zinc intermetallic compound phase that comprises hard, therefore be difficult for taking place the damage of mould, the molding outward appearance is good, and spraying associativity during for spraying and spraying back solidity to corrosion are also excellent.In addition, these drawing product can be stablized and high productivity ground is made.
Description of drawings
Fig. 1 is the mode chart of near surface of the hot press-formed article of second mode of the present invention.
Fig. 2 is the mode chart of near surface of the general hot press-formed article of prior art.
Embodiment
Below, be under the situation of steel plate at steel, the present invention is described in detail.But, hot press-formed, except that steel plate, also can bar, wire rod, tubing etc. for example be undertaken by bending machining, extrusion processing etc.Therefore, the steel among the present invention are not limited to steel plate.In the following description, only otherwise specify, % is quality %.
First embodiment
In the hot press-formed article of first embodiment of the present invention, there is iron-zinc solid solution phase at surface of steel plate.And coating integral body also can be made of this solid solution phase in fact.
In the present invention, so-called iron-zinc solid solution phase, its crystalline network is identical with base material α-Fe, but lattice parameter is bigger, and be considered to be in the phase of sneaking into zinc in the iron.By and can confirm this existence mutually with the X-ray diffraction device with X ray microprobe Atomic Absorption SpectrophotometerICPs such as (being known as EPMA or XMA).
If heating galvanizing is a steel plate, the then iron phase mutual diffusion of zinc in the coating and base material steel plate at first forms iron-zinc intermetallic compound phase in coating.If carry out above-mentioned phase mutual diffusion heat-up time by rising Heating temperature and/or prolongation, then iron-zinc intermetallic compound is transformed to sosoloid gradually.Its result is, final intermetallic compound disappears, and zinc is that coating is made of iron-zinc solid solution phase in essence.
Though the zinc of the hot press-formed article of first mode is coating, also can the lingering section intermetallic compound, be preferably in essence and constitute by iron-zinc solid solution phase.
Because comprising the zinc of iron-zinc solid solution phase is coating, its hardness and steel plate are approaching, so if adding before hot stamping pines for generating this iron-zinc solid solution phase, then press formability can become good.
The zinc that comprises iron-zinc solid solution phase is the zinc content of coating, is preferably more than 5%, more preferably more than 10%.If the zinc content of coating is low excessively, then the solidity to corrosion of coating becomes insufficient, so solidity to corrosion reduces after the spraying of hot press-formed article.
The zinc that comprises iron-zinc solid solution phase is the thickness of coating, forms more than the 1 μ m.If the thickness of this coating is lower than 1 μ m, then solidity to corrosion is insufficient.Also have because if then have the tendency of weldability variation later, so practical going up is made as 50 μ m with its upper limit.Zinc is that the thickness of coating is preferably 5~25 μ m.
As previously mentioned, because inevitable in the oxidation on the hot press-formed light plate surface of industry, so resulting molding, general is the oxide scale film that coating surface has zinc, i.e. zinc oxide film at the zinc that comprises iron-zinc solid solution phase.Manufacture method according to the hot press-formed article of first mode, as described later, preferably by molding being removed the processing of zinc oxide film, be that zinc oxide film on the coating is actually and does not exist and make zinc, even perhaps exist, as mean thickness also below 2 μ m.This is because if mean thickness surpasses 2 μ m, and then the associativity variation of zinc oxide film itself sprays associativity and also becomes insufficient, and the situation of spraying back solidity to corrosion deterioration is also more.The thickness of zinc oxide film is preferably below the 1 μ m, more preferably below the 0.5 μ m.The thickness of zinc oxide film can be measured by the microscopic observation (opticmicroscope or electron microscope) in molding cross section.
But, remove in fact comparatively difficulty of this zinc oxide film fully.Even the zinc oxide film on the top layer that is generated when removing hot stamping fully, because easily oxidation of zinc, the zinc that comprises iron-zinc solid solution phase in atmosphere is that the zinc in the coating is oxidized, so be certain to exist the zinc oxide film of extremely thin (nanometer scale).But if the zinc oxide film of this degree, problem can not take place in essence on performance.The state of so-called " zinc oxide film does not exist in fact " comprises the situation that has this extremely thin oxide scale film.In zinc oxide film, except zinc oxide, also contain the oxyhydroxide etc. of zinc sometimes and as the oxide compound of the aluminium of composition in the plating etc., in the present invention, zinc oxide film also comprises the situation that contains these compositions beyond the zinc oxide.
Though the described zinc that comprises iron-zinc solid solution phase is the total amount of the zinc that comprised in coating and the zinc oxide film, determine according to desired corrosion proof standard, be 10~90g/m as preferred range 2If the zinc total amount is lower than 10g/m 2, then solidity to corrosion becomes insufficient, and is opposite if surpass 90g/m 2, deteriorated weldability then.The zinc total amount is 45~70g/m more preferably 2When calculating adhesion amount, do not change substantially because consider the area of the dull and stereotyped state before being shaped and the difference of the area after the shaping, so adopt the value of trying to achieve as benchmark in the present invention with the area of dull and stereotyped state.
The base material steel plate does not limit especially to composition in the present invention.Composition of steel can well be selected according to the coating associativity after the wettability when the molten zinc plating, the plating.Quench and this feature of realization raising intensity because hot stamping has to utilize, so the steel of hardenability is preferred.In addition, from carrying out the punch process of high-strength steel easily, high tension steel is preferred.
Under the situation of in being set in the hot stamping operation, quenching, because the intensity after the quenching of steel plate is mainly by carbon content decision, so, under the situation of the high-strength shaped product of needs, preferably be made as C content more than 0.1% and below 3%.If C content surpasses this upper limit, then toughness might reduce.
With the wettability of fused zinc in, for in-problem situations of its wettability such as high Si steel, can adopt the pre-treatment that is used to improve the coating associativity of surfacing and preplating etc.
In addition, as described later, in the present invention because preferably use alloy galvanized steel plate, so in order to carry out the alloying of iron-zinc after plating in the short period of time, the preferred low steel of P content as the steel plating plate.Under situation about setting with the processing of tinuous production alloy plating, P content is preferably below 0.2%.
The hot press-formed article of the present invention's first mode can be made by the method for following explanation.
The zinc-based metal plated steel sheet that is used for hot stamping, having zinc on the base material steel plate is plated film.Zinc is the kind of plated film, as long as finally can access the hot press-formed article of first party formula, does not do special qualification.That is, can be pure zinc plated film, also can be the zinc alloy plated film that suitably adds alloying elements such as Mn, Ni, Cr, Co, Mg, Sn, Pb according to its purpose.For zinc is plated film, contains Be, B, Si, P, S, Ti, V, W, Mo, Sb, Cd, Nb, Cu, Sr etc. inevitably from its raw material.
Desirable zinc is that plated film is zinc alloy epitheliums such as zinc-iron, zinc-nickel, zinc-cobalt, zinc-chromium, zinc-manganese.This is that its fusing point is compared higher with pure zinc plated film because of these zinc alloy plated films, and the zinc in hot press-formed in the plated film is difficult to evaporation.
Preferably form though zinc alloy is a plated film, also can form by other plating methods of plating etc. by fusion plating.
From cost and aspect of performance, highly preferred zinc-based metal plated steel sheet is an alloy galvanized steel plate.These be behind molten zinc plating by carrying out heat treated, make from Fe in the steel plate and the Zn alloying (solutionizing) in the coating.If by by the alloying of this heat treated, make the content of the iron in the plated film be formed on than higher more than 10%, then because the heating with the relatively shorter time can form iron-zinc solid solution phase fully before drawing, so comparatively favourable in practicality.
Usually, because comprise Al in the molten zinc plating liquid, so also include Al in the plated film.If the content of Al does not then have special problem greatly about below 0.5% in the plated film.But, be formed on more than 10% in order to make the iron level in the plated film by alloying by heat treated, then the content of Al is about low for favourable below 0.4%.
The plating adhesion amount is considered the evaporation of the zinc in the aftermentioned heating process and is removed minimizing in the oxide scale film operation, makes its skin section at final drawing product, as the remaining 10g/m of zinc 2Above degree is comparatively abundant.Specifically, select according to the needed solidity to corrosion standard in the employed position of molding.For example, in the strict trolley part of solidity to corrosion, the plating adhesion amount of preferred single face is formed on 50g/m as zinc 2More than.
To so and the zinc-based metal plated steel sheet of preparation carries out hot stamping.Heating means during hot stamping are not done qualification especially, but common using gas stove or electric furnace heat.Heating atmosphere is not done qualification, gets final product in the atmosphere.
By this heating, the part of contained zinc evaporation in the plated film, and become zinc oxide film and be present in top, and remaining part or all be diffused in the base material steel, is coating thereby form the zinc that comprises iron-zinc solid solution phase.The thickness of zinc oxide film mostly is more than the 3 μ m when heating in common air atmosphere also according to heating condition.When heating, under the situation of the thickness of controlling formed zinc oxide film energetically, also can adjust atmosphere.For example, under the situation of gas stove, set the concentration of oxygen than the lowland by the adjustment of air-fuel ratio, thereby can reduce the mean thickness of oxide scale film.
Material temperature during hot stamping is generally about 700~1000 ℃.Therefore, furnace temperature also can be set at about 700~1000 ℃.If the material heating temperature is too high, then the thickness of solid solution phase and oxide scale film becomes excessive sometimes, deteriorated weldability, the associativity deterioration of zinc oxide film, thereby spraying associativity deterioration.In addition, if Heating temperature is low excessively, then material softening is insufficient, needs excessive stamping pressure during hot stamping, becomes the reason that surface of steel plate produces defective and steel plate fracture sometimes.
For the situation of hardened steel, because the cooling gradient is relevant with this hardenability, so need cool off the material that is heated to specified temperature with certain above cooling gradient.Therefore, if the material heating temperature is not set to more than the certain temperature, then can not be able to not guarantee to cool off fully gradient.From this viewpoint, preferred especially heating condition makes material temperature become 800~900 ℃ for furnace temperature is set for.
Though do not do special qualification heat-up time, for the gauge control of solid solution phase and zinc oxide film in the purpose condition, and have optimum value.If be for example about several seconds or weak point very heat-up time, be that the generation of iron-zinc solid solution phase of producing of the mutual diffusion mutually of the Fe in Zn and the mother metal in the plated film becomes insufficient then by zinc.In addition, opposite if become heat-up time and surpass 10 minutes long-time, then according to the atmosphere in the stove, zinc oxide film thickness also can become excessive sometimes.Certainly, consider power loss, long-time heating is also not preferred.Be about 4~7 minutes preferred heat-up time.
If carry out drawing immediately after heating, then Ci Shi manufacturing process can be identical with common punching press.Material temperature during hot stamping generally is preferably more than 700 ℃.This temperature can be adjusted according to material thickness, intensity, shaping form.Preferably heated material is arranged in the stamping machine with conveyance as far as possible promptly, carries out drawing.
After carrying out shaping, cool off immediately by hot stamping.Though method of cooling is not done special qualification, when quenching, enough cooling gradient in the time of should guaranteeing to quench.Combination water-cooled mechanism is comparatively effective in press tool for this reason.Use all can in the direct water-cooling mode of directly watering on material with to any of indirect water-cooling mode that mould inside carries out water-cooled.Though directly water or do not water at material surface, the thickness and the structure of the zinc oxide film on surface can produce some difference, all can reach the zinc oxide film thickness that mean thickness is first mode below the 2 μ m with any method.
If carry out heating and cooling under common hot stamping condition, then on the surface of hot press-formed article, zinc oxide film can typically generate with the thickness more than the 3 μ m.Because when the spraying of carrying out continuously, the existence of this zinc oxide film makes spraying associativity and spraying back solidity to corrosion deterioration, therefore will be removed.
The thickness of the zinc oxide film that the molding surface is generated is restricted to below the 2 μ m according to first embodiment, the adjustment of forming by the plating carried out before hot press-formed, and the adjustment of the condition beyond the atmosphere of the heating and cooling of hot stamping is not to realize.But, need various conditions are carried out strict control for this reason.Therefore, industrial method of removing the zinc oxide film on top layer with certain means in hot press-formed back is easy and realistic.
The method of removing surface oxidation zinc layer can be by appropriate means enforcement arbitrarily.The shot-peening method of the fine steel ball of for example oriented surface of steel plate projected at high velocity, spray to surface of steel plate with high pressure and to contain the liquid honing that grinds material, utilize grinding to brush to carry out surfacing, utilize sand paper grinding etc.As the component surface of complicated processing shape being carried out the method that homogeneous is handled, preferred shot-peening method or liquid honing method.When utilizing sand paper to grind the oxide scale film that removes the de-plating top layer, have grinding over-drastic tendency, from this point, the shot-peening method is comparatively excellent.
The shot-peening method also is meant the ball method of blowing (shot peening), thereby typically refers to by removed the method for surface contaminants and corrosion etc. by the steel ball of centrifugal force or the hundreds of μ m of air pressure projection diameter.In the present invention, by projection ball bullet, preferably use steel ball as institute.General purpose in order to eliminate rust, projection are called the steel cuttings of corner angle abrasive material or are cut off very carefully to such an extent that the method for steel wire is comparatively suitable.But, for situation of the present invention, also can only remove the superfluous zinc oxide film in surface, do not damage the zinc-plated system layer that comprises iron-zinc solid solution phase as much as possible.When being suitable for abrasive material, embodiment as described later is because zinc coating also is damaged easily when removing zinc oxide film, so condition enactment is difficult to.Therefore preferred ball bullet be spherical and its hardness also the degree with steel is suitable.
The condition of shot-peening can suitably be adjusted with the surperficial state of oxidation according to the shape of molding.General because to compare stand-off distance elongated with the material of writing board shape when handling molding, so obtain effective shot blasting effect, preferably be suitable for the grenade instrumentation of Scroll-type in order to prevent to throw energy decrement.Under the situation of writing board shape and small shaping product, also can use the air spray of air pressure type.In addition, if the steel ball of projection is meticulous, thereby then because the energy decrement epithelium ability of removing reduces, so preferably use the steel ball of average particulate diameter 100~500 μ m magnitudes.Injecting time, as the time of shot-peening bundle spot (shot pattern) arrival privileged site, approximately just enough from about several seconds to 30 seconds.
Liquid honing is the method for water that contains the grinding material of silicon grain etc. with the high pressure spraying more than the 100MPa.Identical with shot-peening, can be not that coating imposes substantial damage and only removes the zinc oxide film on top layer to mother metal and zinc.Because make water, particularly because might get rusty, so after processing, make its thorough drying in end face portion.
Any of shot-peening and liquid honing all has the effect of the zinc oxide that not only can remove the top layer, also has the effect of the oxide skin of the iron of removing end face.
Second embodiment
The hot press-formed article of second embodiment of the present invention, shown in the mode chart of Fig. 1, have near the top layer by the iron that forms by the iron-zinc solid solution phase in essence-zinc solid solution layer shown in 2 (below, abbreviate solid solution layer as), have the surface tissue that the zinc oxide 3 that forms the top layer exists at an upper portion thereof.That is, on the steel 1 of base material, the order be formed with iron-zinc solid solution layer 2 with and on zinc oxide film 3.As shown in Figure 2, do not form generally being seenly, between iron-zinc solid solution layer 2 and zinc oxide film 3, have the surface tissue of the layer 4 of the iron-zinc intermetallic compound contain real mass.Iron-zinc solid solution layer 2 and zinc oxide film 3 are that steel plate forms by heating galvanizing in oxidizing atmosphere.
In the present invention, so-called iron-zinc solid solution phase, though its crystalline network is identical with base material α-Fe, lattice parameter is bigger, and is considered to be in the phase of sneaking into zinc in the iron.The iron that forms by this iron-zinc solid solution phase-zinc solid solution layer in essence, can by and confirm its existence and thickness with X-ray diffraction device and X ray microprobe Atomic Absorption SpectrophotometerICPs such as (EPMA or XMA).Because the hardness of iron-zinc solid solution layer approaches steel plate, therefore different with the Fe-Zn intermetallic compound, therefore easy damaged mould not can avoid the bad order of the molding that caused by the mould damage.
Iron-the thickness of zinc solid solution layer is preferably the scope of 10~40 μ m.If the thickness of solid solution layer is insufficient than the little then solidity to corrosion of 10 μ m, if above 40 μ m then weldability become insufficient.In addition, the zinc content in iron-zinc solid solution layer is preferably more than 5%.The thickness of iron-zinc solid solution layer is 15~35 μ m more preferably.The thickness measurement method is described in an embodiment.
In the hot press-formed article of second embodiment of the present invention, near the steel plate top layer, there is not the intermetallic compound phase.So-called intermetallic compound phase is that observed δ 1 phase, Γ equate the intermetallic compound between iron-zinc in the plated film of for example alloy galvanized steel plate.Intermetallic compound is because hardness is higher, so easily mould is caused damage in drawing.In addition, carrying out under the situation of severe processing owing to crack in mutually at intermetallic compound, the associativity that is easy to generate epithelium descend and spraying after bad order.This fact that do not exist of intermetallic compound phase can be confirmed by the outward appearance structure observation.
That is, in this hot press-formed article, seen in the plated film of alloy galvanized steel plate to iron-zinc intermetallic compound disappear mutually.Certainly, there is not pure zinc phase yet.Can realize this disappearance mutually by the heating process of hot stamping and the heating of stamping procedure.Therefore, also can exist in the steel plate before hot stamping intermetallic compound mutually with pure zinc mutually.
Zinc oxide film by the surface and be present in it iron-zinc solid solution layer of (not being mingled with above-mentioned intermetallic compound phase) just down can be guaranteed the solidity to corrosion of drawing product.But if zinc oxide film becomes blocked up, then remove the associativity deterioration of zinc oxide film self, the spraying associativity become insufficient outside, weldability is deterioration also.The mean thickness of zinc oxide film is formed on below the 5 μ m for this reason.Lower limit to the thickness of zinc oxide film is not done special restriction.As described later, during the hot stamping zinc-based metal plated steel sheet, the thickness of zinc oxide film mostly is greatly more than the 3 μ m in oxidizing atmosphere.Yet the thickness of oxidisability layer also can be thinner than 3 μ m, for example the thinness of 0.1 μ m.
In zinc oxide film, except that zinc oxide, contain in addition zinc other zinc such as oxide compound compound or as the situation of the oxide compounds such as Al of composition in the coating.In the present invention, make zinc oxide film form the coating that contains this.The thickness of zinc oxide film, the microscopic observation (opticmicroscope or electron microscope) of section that can be by molding is observed.
Because in the fused zinc plating bath, be added with a spot of Al, so molten zinc plating is to contain a spot of Al in the plated film of steel plate (for example, alloy galvanized steel plate).Therefore in molding, contain Al in iron-zinc solid solution layer that forms by plated film and the zinc oxide film to its hot stamping.In addition, because also contain the Al of trace in the generalized case base material steel, so Al might spread from the base material steel.
The hot press-formed article of second embodiment, the total amount of contained Al is 0.5g/m in zinc oxide film and the solid solution layer 2Below, be preferably 0.45g/m 2Below.Al is except existing as intermetallic compound and metal, and also the form with the Al oxide compound exists.The total content of the Al oxide compound that exists in zinc oxide film and the solid solution layer, as Al at 5mg/m 2Below, be preferably 3mg/m 2Below.
As the total content of Al with as the total content of the Al of Al oxide compound, if surpass the above-mentioned upper limit, it is just insufficient then to spray associativity.Because in the content of the content of Al and Al oxide compound, confirmed mutual association, so only measure the total content of Al or, can both judge whether it is the hot press-formed article good according to the spraying associativity of second embodiment as in the total content of the Al of Al oxidation either party.And, the total content of preferred Al and as two sides of the total content of the Al of Al oxide compound, the condition of the satisfied second embodiment defined.
The content of the oxide compound of Al and Al is not clear and definite as yet to the reason of the spraying negative impact that associativity produced.But, it is generally acknowledged that then they thicken at the zinc oxide film of hot press-formed article and the interface of solid solution layer if Al or Al oxide compound become too much, hinder the associativity of zinc oxide film, and the spraying associativity of molding is had a negative impact.
The content of Al and Al oxide compound, can be impregnated into respectively by the drawing product test portion that will measure surface area in the aqueous solution (concentration for example is about 5~10%) of hydrochloric acid and chromic acid, make epithelium (zinc oxide film and solid solution layer) dissolving, and the quantitative back of the Al that is contained in this solution is obtained.Al and Zn with respect to metallic state in hydrochloric acid (comprising intermetallic compound) and this two states of oxide compound dissolve, and the Al of metallic state and Zn do not dissolve in chromic acid.Therefore by with test portion dipping about 10 minutes in 5% chromium trioxide aqueous acid for example, just can only make the oxide dissolution of Al and Zn.As for Al in the lysate quantitatively, it is comparatively convenient to be undertaken by instrumental analysis such as for example ICP (high-frequency induction coupled plasma) (Inductively coupled plasma) luminescence analysis, atom light absorption methods.
As previously mentioned, this Al and Al oxide amount, the both sides that measure according to the Al in Al amount and the steel in the plated film change, and particularly the influence of Al amount is bigger in the plated film.Therefore, be under the situation about making at the processing starting material by molten zinc plating, the Al amount outbalance in the control plated film.About this point, relevant manufacture method is recorded and narrated below.For the situation of electro-galvanizing and electroplating zinc alloy, because plated film does not contain Al in fact, thus only from steel, spread Al, but because this is diffused as trace and can become problem, so do not need special countermeasure.
In second embodiment, the composition of the base material steel plate of hot press-formed article is not done special qualification.By the manufacture method of purposes and drawing product is considered, can determine suitable composition.
For example, as previously mentioned, owing in the hot stamping operation, pass through to quench and high strength, therefore under the situation that forms high-intensity molding, intensity after the quenching of steel plate is mainly by carbon content decision, therefore preferably is made as C content more than 0.1% and below 3%.If C content is than more than 3%, then toughness might reduce.Except C, also can in steel, add one or more of other alloying elements (for example, Mn, Cr, B) of known raising hardenability in right amount.
When the base material steel plate is carried out molten zinc plating, very necessary with the wettability of fused zinc.For in-problem steel grades of coating wettability such as high Si steel, can use surfacing and preplating etc. to improve the method for associativity.Therefore, in Fig. 1, between base material steel plate 1 and iron-zinc solid solution layer 2, the fusion solid solution layer that also can have pre-plating layer or after this form by thermal treatment.But there is more problem owing to generate intermetallic compound, therefore also not preferred.
In addition, when using alloy galvanized steel plate as the steel plating plate, the preferred poor steel plate of P is so that the alloying of the iron-zinc after plating can be carried out in the short period of time.Zinc-plated film is carried out under the situation of Alloying Treatment with tinuous production in imagination, the P amount is preferably below 0.2%.
Because the hot press-formed article of second embodiment has excellent spraying associativity, use so can after drawing, spray.But, can not spray yet and use according to using the position.
The hot press-formed article of second embodiment of the present invention can will become the heating process that raw-material steel plate heats with specified criteria by comprising, and then the method for the drawn-steel stamping procedure of high temperature is made.
As the steel plate that the processing starting material use, be not limited to have aforementioned structure near the top layer of the final hot press-formed article of making by heating process and pyritous punching press, there is no particular limitation, but preferably use zinc-based metal plated steel sheet as described below.
Single-face plating adhesion amount at zinc-based metal plated steel sheet is 40g/m 2More than and at 80g/m 2Below.If the coating adhesion amount is too small, according to the position, the situation that also has solidity to corrosion not meet the demands.In addition, pure zinc-plated in, in the manufacturing procedure when hot stamping, be not easy to form solid solution layer on the contrary, and form thicker oxide scale film and remaining intermetallic compound.If the coating adhesion amount surpasses 80g/m 2, then pine in hot press-formed adding usually, can not be in steel the zinc in the solid solution plated film fully, iron-zinc intermetallic compound and the metallic zinc that might remaining Γ equates.If remaining intermetallic compound, then top layer hardening, not only problem can take place in the processibility during punching press, causes the damage of mould, and can cause the reduction of die life and the deterioration of molding outward appearance.The coating adhesion amount is preferably 50g/m 2More than and at 70g/m 2Below.
In order to obtain this thick relatively zinc-based metal plated steel sheet, the method for fusion plating is compared on cost more favourable with plating.In addition, the method for the hot-dip galvanized steel sheet of alloying is more suitable for being used for second embodiment than simple hot-dip galvanized steel sheet.This be because, the hot-dip galvanized steel sheet of alloying, during heating when hot stamping, the phase mutual diffusion between iron-zinc is carried out apace, finally can easily not had the molding of iron-zinc intermetallic compound phase.But if can form by zinc oxide film given to this invention and surface tissue that iron-the zinc solid solution layer is constituted, then hot-dip galvanized steel sheet also can use as the processing starting material.
As previously mentioned, hot-dip galvanized steel sheet (hot-dip galvanized steel sheet that comprises alloying) contains a spot of Al usually in plated film.Like this, in molten zinc plating, for the diffusion of iron-zinc of suppressing coating-steel of base metal interface, and the scum silica frost amount of control plating bath, in plating bath, add about 0.1~0.2% Al usually.As previously mentioned, if the Al that is comprised in the iron-zinc solid solution layer of molding and the oxide scale film (zinc oxide film) amount (or Al oxide amount) surplus, then the spraying associativity to molding has a negative impact.From this point, the Al content in the plated film of the hot-dip galvanized steel sheet of hot-dip galvanized steel sheet or alloying is made as below 0.35%.
When the hot-dip galvanized steel sheet of alloying used as the starting material of hot stamping, the content of Fe was higher in the preferred plated film.This is because as mentioned above, by eliminating the intermetallic compound phase with relatively short time heating, and only form the surface structure that iron-the zinc solid solution layer forms by zinc oxide film and below thereof.But if the too high levels of the Fe in the plated film then according to circumstances, need reduce the linear velocity of fusion plating to heavens, this is unrealistic.The preferable range of the content of Fe is 10~20% in the plated film, more preferably 10~15%.
Though cost uprises, also the processing starting material of electroplating steel plate as hot stamping can be used.In electroplating steel plate, has the advantage that in plated film, does not contain Al usually.Electroplating steel plate also can be common pure steel plate galvanized, but is preferably plating iron-zinc (Fe-Zn) alloy steel plate (the Fe content in the plated film is below 20%).Fe-Zn alloy plating steel plate, identical with the hot-dip galvanized steel sheet of alloying except having the advantage that does not contain Al, have and can form solid solution layer with the relatively short time, and the additional advantage of remaining intermetallic compound not.
The heating means of the heating process of hot stamping are not done special qualification.Usually, using gas stove or electric furnace add the raw-material zinc-based metal plated steel sheet of hot-work in oxidizing atmosphere.Though oxidizing atmosphere also can be an atmosphere, also can be the mixed gas of atmosphere and/or oxygen and other gas (for example, nitrogen, combustion gases etc.).
Add at this and to pine for, the part of the zinc that is comprised in the plated film, evaporation, or become zinc oxide film and be present in top, residual be diffused in the base material steel and solid solution in iron fully.Thus, intermetallic compound is not remaining mutually, forms the zinc oxide film on top and the iron-zinc solid solution layer of bottom from plated film.
The thickness of zinc oxide film, though according to heating condition, pining for multiform in adding of common air atmosphere becomes more than the 3 μ m.When the thickness of formed zinc oxide film of when heating control (oxide scale film) energetically, also can carry out the adjustment of heating atmosphere.For example, under the situation that is gas stove, set the concentration of oxygen than the lowland by the adjustment of air-fuel ratio, thereby can reduce the mean thickness of oxide scale film.
Material temperature during hot stamping, normally about 700~1000 ℃, furnace temperature also is made as same temperature usually.If the material heating temperature is too high, then exist the thickness of solid solution layer and oxide skin rete to become excessive, the deterioration of weldability meeting sometimes, the associativity of zinc oxide film is deterioration also, spraying associativity variation.On the other hand,, need excessive stamping pressure during hot stamping, become the reason of material surface generation defective or material fracture sometimes if Heating temperature is low excessively, then insufficient for material softening.
For the situation of hardened steel,, expect that temperature is heated to more than the certain value so need a person with the qualifications of a general, and in punching press, cool off with the cooling gradient more than the certain value because the cooling gradient is associated with this hardenability.Therefore, if the material heating temperature not more than certain value, then can not fully be guaranteed its cooling gradient.
In addition, in second embodiment,, do not make it residual mutually, zinc is diffused in the base material steel and eliminate intermetallic compound for by the heating in this manufacturing procedure.For this reason, the material heating temperature is set as comparatively more favourable than higher temperature.From above viewpoint, the material Heating temperature of second embodiment is made as 850~950 ℃ scope.
In heating condition, from the viewpoint of eliminating the intermetallic compound phase and controlling the thickness of solid solution layer and zinc oxide film, except aforesaid temperature, heating condition and heat-up rate are also very important.If be for example several seconds or extremely short, then very difficult to form by zinc fully be the mutual diffusion mutually of plated film and mother metal and iron-zinc solid solution layer epithelium of forming heat-up time.During by the steel plate of electric furnace or gas stove heating room temperature,, be difficult to obtain epithelium structure that intermetallic compound is subdued, shown in Figure 1 if be below 3 minutes the time heat-up time (total ascent time of intensification described later and maintenance).But, if be to surpass 10 minutes long-time heat-up time, then according to furnace atmosphere, the situation of zinc oxide film thickness surplus appears sometimes.Certainly, consider power loss, long-time heating is also also not preferred.Therefore, be made as heat-up time 3~10 minutes, be preferably 4~7 minutes.
In addition, be made as below 15 ℃/second from the average heating speed of room temperature until the Heating temperature of 850~950 ℃ scope.If to heat up than its faster speed, then form the residual high epithelium of hardness of iron-zinc intermetallic compound, the mould of loss when hot stamping perhaps, comprises low-melting pure zinc phase time at steel plate, and the metallic zinc of liquid state might be dispersed.Set heat-up rate if cross the lowland, it is long then to become heat-up time, diminishes the practicality of industry.Preferred heat-up rate is 3~12 ℃/second, more preferably 4~10 ℃/second.
Be warming up to 850~950 ℃ the temperature of scope with the speed below 15 ℃/second after, keep certain hour in this temperature range.If hold-time of this temperature range not more than 30 seconds, then have the mutually residual situation of intermetallic compound.
The punching press condition of stamping procedure can be identical with common hot stamping condition.Material temperature during shaping should be adjusted according to material thickness, intensity and shaping form, but the material temperature usually during punching press is more than 700 ℃.Therefore, preferably will be in advance as the zinc-based metal plated steel sheet of above-mentioned heating, carrying promptly is set to stamping machine and drawing.
Method of cooling in the hot stamping and after the punching press is not done special qualification.But, when quenching, the work of the needed cooling gradient of need guaranteeing to quench.For this reason, combination water-cooled mechanism is comparatively effective in press tool.Can use the direct water-cooling mode of on material, directly watering, or mould inside be carried out indirect water-cooling mode any of water-cooled.Though according to directly watering or do not water at material surface, and can produce some differences to the thickness and the structure of the zinc oxide film on surface, any mode all can access the structure of the epithelium of second embodiment.
In the method for second embodiment, after hot stamping, may not remove the operation of surface oxidation zinc layer.But, under the situation that requires very strict spraying associativity,, also can carry out removing all or part of operation of zinc oxide film by shot-peening and liquid honing though can cause productive reduction.
This zinc oxide film remove processing, comparing with aforesaid situation of removing ferriferous oxide of the prior art can be slight processing.For example, under the situation of shot-peening, can use the steel ball of diameter 100~150 μ m, the device by Scroll-type carry out the several seconds~about tens of seconds processing.
Liquid honing is to contain the method that silicon grain etc. grinds the water of material with the high pressure spraying more than the 100Mpa.Identical with shot-peening, can be not that coating produces substantial damage, and can only remove the zinc oxide film on upper strata mother metal and zinc.Because make water,, make its thorough drying after therefore handling so might get rusty in end face portion.
Shot-peening and liquid honing all not only have the effect of the zinc oxide film of removing the upper strata, also have the effect of the oxide skin of the iron of removing the end face generation.It is too much to remove the easy grinding of zinc oxide film with sand paper, therefore not preferred.
Embodiment
Following embodiment is used for illustration action effect of the present invention particularly, and should not be construed as is limitation of the present invention.
(embodiment 1)
Present embodiment illustration first embodiment of the present invention.
Zinc-based metal plated steel sheet as hot press-formed usefulness, what use is alloy galvanized steel plate, its feature is as follows, and the colding pressing of thickness of slab 2mm that will contain C:0.2%, Si:0.3%, Mn:1.3%, P:0.01% prolonged steel plate as the base material steel plate, and then the coating adhesion amount is single face 45~75g/m 2And the iron level in the plated film is 13~15%.But, in the routine No.5 of table 1, as a comparative example, use the cold-rolled steel sheet of not plating.
To so heat 3~10 minutes in the air atmosphere stove of the steel plate galvanized of preparation 850~950 ℃ of temperature in stove.By changing heating condition (combination of temperature * time), and the hot stamping of the thickness of the be made into conversion thickness of zinc oxide film and iron-zinc solid solution phase and the zinc amount in the solid solution phase is with for test materials.
Each is hot press-formed in order to simulate after taking out from stove for the test material, and the dull and stereotyped stamping machine of the water-cooled mechanism by having water jacket carries out cooling in 30 seconds immediately.
In cooled one side for the test material, carry out the shot peening of air pressure type, remove the zinc oxide film on top layer fully or by halves.It is 2kgf/cm that air is pressed 2, the distance between nozzle and the confession test materials is 20mm, is that the steel ball of 0.3mm uses as the ball bullet with average particulate diameter.The degree of shot-peening was adjusted according to the shot-peening time.
In the routine No.6 of table 1, do not carry out shot peening.In No.8 by utilizing sand paper to carry out the processing of removing of zinc oxide.Zinc coating as shown in table 1, as to utilize sand paper to remove fully.
In the hot press-formed molding of the simulation that so obtains, in such a way the result is estimated.
1) zinc that comprises iron-zinc solid solution phase is the thickness measurement of coating:
Be made into the section test portion of hot press-formed article, carry out final mirror ultrafinish having carried out the above-mentioned face of handling a side of removing.In this test portion,, carry out X-ray analysis by EPMA with the condition that electron accelerating voltage 15kV, electric current 5~10nA, sweep velocity 2~5 μ m/ divide.Consider the zone that emits X ray from test portion, determine as follows mutually or iron-zinc the solid solution phase that occurred of the more close private side of zinc oxide film (mother metal side) and the interface of mother metal than Zn-Fe intermetallic compound, and with the Zn-Fe intermetallic compound mutually or the interface of zinc oxide film.
In the interface of iron-zinc solid solution phase and mother metal, the characteristic X ray strength of the Zn of iron-zinc solid solution phase is assumed to, 1/2 intensity position with the constant portion of iron-zinc solid solution phase is the center, the integrated intensity of the tail of steel of base metal side (tail) part is normal distribution, and intensity distribution is replaced into distribution function, from first error probability judged with the position of standard deviation 2 σ as the interface.Same is the integrated intensity of center from the part of the tail of ining succession towards iron-zinc solid solution phase according to constant portion or 1/2 intensity position greatly partly with Zn-Fe intermetallic compound phase or zinc oxide film, obtain the opposition side of iron-zinc solid solution phase the interface (that is, with intermetallic compound mutually or the interface of zinc oxide film).With the thickness of the length between this two side's interface as iron-zinc solid solution phase.
Under the situation that does not have iron-zinc intermetallic compound phase, as zinc the thickness of coating with the thickness of above iron of trying to achieve-zinc solid solution phase.When having iron-zinc solid solution phase, utilize observation by light microscope and obtain the thickness of this phase, and with the thickness addition of above-mentioned iron-zinc solid solution phase be the thickness of coating as zinc.
2) thickness measurement of zinc oxide film:
With the above-mentioned cross section test portion of observation by light microscope, and the thickness of zinc oxide film on surface that zinc oxide is removed a side of processing has been carried out in investigation.
3) adhere to the total amount of zinc
Adhering to the mensuration of the total amount of zinc carries out with following.
Cut out the test film of 10cm * 10cm from molding, and utilize sand paper to grind the thickness of coating of the opposing face (removing a side of processing) of mensuration face, removing dezincify fully is coating (comprising iron-zinc solid solution phase).So, will only all be dissolved in 10% the hydrochloric acid, and ask the zinc amount that exists in solution at the residual coated test film of one side.
4) performance test
The spraying associativity:
Molding is being carried out after chemical transformation handles (treatment solution: Japanese bonderizing system PBL-3080, treatment condition are the standard conditions of this treatment solution), on the face of a side of having carried out removing processing, implementing EFI and be coated with (gradient (slope) of the Northwest paint system GT10, target film thickness 20 μ m, voltage and powered-on mode: 200V switch on (from 0V to 200V with 30 seconds), sintering 160 ℃ * 20 minutes).
This electricity is adhered to the spraying material, impregnated in 40 ℃ the ion exchanged water 500 hours, after this on spraying face with the method cutting cross battens of the cross battens test put down in writing among the JIS G331212.2.5, and be with stripping test.Be qualified (zero) below 1% with the tessellated area occupation ratio (peeling off in 100 squares square number) of peeling off, surpassing 1% is defective (*).
Solidity to corrosion after the spraying:
Adhere to the spraying face that sprays material at described electricity, form reach with the cutting knife incision and the wound (cruciform mouth) of steel substrate after, in the salt spray testing use of JIS Z2371.With the maximum swelling width of the wound portion after 960 hours be test portion below the 2mm as being qualified (zero), the test portion that surpasses 2mm is as defective (*).
Concentrate in the table 1 and show the result.No.1~4th is according to example of the present invention.
Table 1
Figure DEST_PATH_S04817496819970226D000191
*Extraneous condition of the present invention.
(embodiment 2)
Present embodiment illustration second embodiment of the present invention.
1) manufacturing of hot press-formed article
Starting material steel plating plate:
The cold-rolled steel sheet of hardenability of thickness of slab 2mm that will contain C:0.2%, Si:0.3%, Mn:1.3%, P:0.01% is as the base material steel plate, and the coating adhesion amount is 50~65g/m at every single face 2, the alloy galvanized steel plate (mark: GA) as processing material use of the content of the Fe in the plated film in 13~15% scopes.
In addition, with the cold-rolled steel sheet of chemical constitution same as described above and thickness of slab as the base material steel plate, electrogalvanizing steel plate (mark: EG; Coating adhesion amount: every single face 30 or 70g/m 2), iron-zinc (Fe-Zn) alloy plating steel plate (mark: FZ, coating adhesion amount: every single face 45g/m 2, the Fe content in the plated film: 15%) and hot-dip galvanized steel sheet (mark GI, plating adhesion amount: each face 60g/m 2) also use as the processing starting material.In addition, as conventional example, use Aludip (mark AL; Coating adhesion amount: every single face 80g/m 2).
Contain in each steel plating plate of GA, the GI of Al and AL at plated film, investigate Al content in the plated film by the ICP luminescence analysis of solution that the plated film dissolving is obtained.In addition, contain GA, the FZ of Fe at plated film, and Fe is diffused in each steel plate of the GI of plated film and AL during the fusion plating, the content of the Fe in the plated film is also in kind investigated.
Heating process:
In stove, heat described steel plating plate with the heating condition shown in the table 2.And by change heating condition (combination of heat-up rate, Heating temperature, hold-time), and be made into changed that intermetallic compound has or not mutually, the sample of the thickness of the thickness of zinc oxide film and iron-zinc solid solution layer.
Stamping procedure:
Take out described sample from stove after, hot press-formed in order to simulate, promptly the dull and stereotyped stamping machine of the water-cooled mechanism by having water jacket carries out punching press and makes molding.The material temperature of (just) is represented with press temperature in table 2 during punching press.In the water-cooled press tool, kept for 30 seconds.Side by side realize the quenching of base material steel plate thus with drawing.
2) analysis of molding
The thickness of the having or not of intermetallic compound phase, zinc oxide film:
Generate the cross section test portion of hot press-formed article, and carry out final mirror ultrafinish.With this sample of observation by light microscope, and the having or not and the thickness of zinc oxide film of investigation intermetallic compound phase.
The thickness of iron-zinc solid solution layer:
Utilize EPMA, the condition of dividing with electron accelerating voltage 15kV, electric current 5~10nA, sweep velocity 2~5 μ m/ is carried out X-ray analysis to the cross section test portion (having carried out mirror ultrafinish) of hot press-formed article.The zone of the X ray that consideration is emitted from test portion, determine as follows mutually or iron-zinc the solid solution phase that occurred of the more close private side of zinc oxide film (mother metal side) and the interface of mother metal than Zn-Fe intermetallic compound, and with the Zn-Fe intermetallic compound mutually or the interface of zinc oxide film.
In the interface of iron-zinc solid solution phase and mother metal, the characteristic X ray strength of the Zn of iron-zinc solid solution phase is assumed to, 1/2 intensity position with the constant portion of iron-zinc solid solution phase is the center, the integrated intensity of the tail part of steel of base metal side is normal distribution, and intensity distribution is replaced into distribution function, from first error probability judged with the position of standard deviation 2 σ as the interface.Same is the integrated intensity of center from the part of the tail of ining succession towards iron-zinc solid solution phase according to constant portion or 1/2 intensity position greatly partly with Zn-Fe intermetallic compound phase or zinc oxide film, obtain the opposition side of iron-zinc solid solution phase the interface (that is, with intermetallic compound mutually or the interface of zinc oxide film).With the thickness of the length between this two side's interface as iron-zinc solid solution phase.
Al amount and Al oxide amount:
Cut out 2 test films of given area from hot press-formed article, a slice is immersed 10%HCl (resistanceization meter), again another sheet is immersed 5% CrO 3In, the dissolving top layer.According to the Al amount of separating out in each liquid (measuring), calculate the amount of Al amount and Al oxide compound by the ICP luminescence analysis.
3) performance test, other evaluations
The epithelium crackle:
Utilize the surface of observation by light microscope thermoforming product, whether investigation has produced crackle in the plated film on surface.As previously mentioned, if intermetallic compound exists mutually, then be easy to generate crackle in the plated film, thereby also be easy to generate the mould flaw.
The mould flaw:
By the mould after the visual observation drawing, investigation has or not the mould flaw.
The spraying associativity:
Molding has been implemented chemical transformation processing (treatment solution: Japanese bonderizing system PBL-3080), and then implement electricity and adhere to spraying (Northwest paint system GT10, target film thickness: 20 μ m; And the gradient of voltage and powered-on mode: 200V energising (from 0V to 200V30 second), sintering 160 ℃ * 20 minutes).
This electricity is adhered to the spraying material, impregnated in 40 ℃ the ion exchanged water 500 hours, after this on spraying face with the method cutting cross battens of the cross battens test put down in writing among the JIS G3312 12.2.5, and be with stripping test.Be qualified (zero) below 1% with the tessellated area occupation ratio (peeling off in 100 squares square number) of peeling off, surpassing 1% is defective (*).
Solidity to corrosion after the spraying:
Adhere to the spraying face that sprays material at described electricity, form reach with the cutting knife incision and the wound (cruciform mouth) of steel substrate after, in the salt spray testing use of JIS Z2371.With the maximum swelling width of the wound portion after 960 hours be test portion below the 2mm as being qualified (zero), the test portion that surpasses 2mm is as defective (*).
Weldability:
In following spot welding condition, welding current is investigated.Specifically, according to, weld nugget (nugget) diameter (mm) becomes
Figure DEST_PATH_S04817496819970226D000211
(t: minimum current thickness of slab (mm)) ( Electric current), investigate the electric current (splash generation electric current) that splash begins to take place.Will from
Figure DEST_PATH_S04817496819970226D000213
The difference between current of the electric current that electric current takes place to splash is be decided to be qualified (zero) more than the 1000A, will be lower than being decided to be of 1000A defective (*).
In table 2, concentrate and show above mensuration and test-results.
Figure DEST_PATH_S04817496819970226D000221
As shown in table 2, the hot press-formed article of example of the present invention (No.1~4) can be produces damage and make mould, and spraying associativity, spraying back solidity to corrosion, weldability are all comparatively excellent.
Relatively therewith, at the remaining hot press-formed article (No.5,7,8,9,12,13) that the intermetallic compound phase is arranged of near surface, any all confirms to have flaw in the mould after punching press.These or coating form or plate the excessive test portion (No.9) of the thin excessively test portion (No.7) of diverse test portion (No.5,8) or coating adhesion amount or heat-up rate or hold-time or full heat-up time too short test portion (No.12,13).In the test portion (No.5,6) that the Al on top layer measures and the Al amount of oxidation is bigger, spraying associativity and spraying back solidity to corrosion are poor.Al content in they any epithelium is all bigger.In addition, the test portion that the thickness of zinc oxide film (oxide scale film) is bigger (No.7,9,10,11), its spraying associativity, spraying back solidity to corrosion, weldability are all relatively poor.Wherein, or the too high test portion (No.10) of the excessive test portion (No.9) of the thin excessively test portion (No.7) of coating adhesion amount or heat-up rate or Heating temperature or heat-up time long test portion (No.11).For the test portion (No.8) of hot stamping fusion Al-plated steel sheet,, also have spraying back solidity to corrosion also poor in addition because of remaining intermetallic compound produces damage to mould mutually.
Hot press-formed article of the present invention not only sprays the back corrosion resistance excellent, and the spraying associativity is also comparatively excellent, is specially adapted to the trolley part of running gear parts, reinforcement etc.In addition, according to the manufacture method of the hot press-formed article of this aspect, can be easily and stably make this hot press-formed article, therefore can reduce manufacturing cost certainly, and guarantee the bigger effect of performance aspect the stable quality of product.

Claims (10)

1. hot press-formed article, be to zinc-plated be that steel carry out hot stamping and are shaped, it is characterized in that, surface at this molding, have in fact by iron-zinc solid solution phase and constitute, and 1 μ m is above and the zinc below 50 μ m is coating, the mean thickness that is present in this zinc and is the zinc oxide film on the coating is below 2 μ m, and the described zinc that is made of iron-zinc solid solution phase in fact that is present in steel surface is that the total zinc amount in coating and the zinc oxide film is 10g/m 2More than and at 90g/m 2Below.
2. hot press-formed article according to claim 1 is characterized in that, is on the coating at described zinc, does not have zinc oxide film in fact.
3. hot press-formed article according to claim 1 and 2, wherein said zinc are the layer that coating does not have the iron-zinc intermetallic compound phase that contains real mass, and wherein satisfy in following (1) and (2) at least one:
(1) is contained in the total amount of the Al in described iron-zinc solid solution layer and the zinc oxide film at 0.5g/m 2Below; With
(2) be contained in described iron-zinc solid solution layer and the zinc oxide film as the total content of the Al of Al oxide compound at 5mg/m 2Below.
4. hot press-formed article according to claim 1 and 2 is characterized in that, the mean thickness of described iron-zinc solid solution layer is 10~40 μ m.
5. the manufacture method of a hot press-formed article is characterized in that, comprising:
Heating galvanizing is the heating process of steel;
Hot press-formed operation, by zinc-plated to be that steel carry out hot press-formed to heated, to have the thickness that is made of iron-zinc solid solution phase in fact be that the following zinc of the above 50 μ m of 1 μ m is the hot press-formed article of coating and the zinc oxide film on it thereby form; And
Remove the zinc oxide film operation, for the mean thickness of the zinc oxide film on the top layer that makes resulting hot press-formed article is below the 2 μ m, and by with average particulate diameter being the shot-peening method of the steel ball of 100~500 μ m as the use of ball bullet, remove the part or all of of this zinc oxide film, and the described zinc that is made of iron-zinc solid solution phase in fact that is present in steel surface is that the total zinc amount in coating and the zinc oxide film is 10g/m 2More than and at 90g/m 2Below.
6. method according to claim 5 is characterized in that described hot press-formed operation realizes the quenching of steel simultaneously.
7. the manufacture method of hot press-formed article according to claim 5 is characterized in that,
Described zinc-plated be that steel are that Al content is below the 0.35 quality %, the coating adhesion amount is 40g/m 2More than and at 80g/m 2Following molten zinc plating steel or hot dip alloyed galvanized steel;
In described heating process, after in oxidizing atmosphere, steel being warmed up to 850 ℃~950 ℃ temperature range from room temperature with the V-bar below 15 ℃/second, in this temperature range, keep more than 30 seconds, and described heating-up time and hold-time add up to more than 3 minutes and below 10 minutes; And
In described stamping procedure, steel are carried out drawing 700 ℃~950 ℃ temperature range.
8. according to each described method in the claim 5 to 7, it is characterized in that steel are that the content of the Fe in the plated film is the hot dip alloyed galvanized steel of 10~20 quality %.
9. a method of making hot press-formed article according to claim 1 and 2 is characterized in that, comprising:
Heating galvanizing is the heating process of steel;
Hot press-formed operation, by zinc-plated to be that steel carry out hot press-formed to heated, to have the zinc that is made of iron-zinc solid solution phase in fact be the hot press-formed article of coating and the zinc oxide film on it thereby form; And
Remove the part or all of operation of this zinc oxide film,
Wherein, described steel are that the Fe content in electro-galvanizing steel or the coating is the following zn-fe alloy electroplating steel products of 20 quality %, and its coating adhesion amount is 40g/m 2More than and at 80g/m 2Below;
In described heating process, after in oxidizing atmosphere, steel being warmed up to 850 ℃~950 ℃ temperature range from room temperature with the V-bar below 15 ℃/second, keep more than 30 seconds in this temperature range, and described heating-up time and described hold-time add up to more than 3 minutes and below 10 minutes;
In described stamping procedure,, steel are carried out drawing 700 ℃~950 ℃ temperature range.
10. method according to claim 9 is characterized in that, by at least a portion of employed mould in the stamping procedure is cooled off, and quenches in stamping procedure.
CN200480017496.8A 2003-04-23 2004-04-23 Hot press-formed article and method for its manufacture Expired - Lifetime CN1809650B (en)

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