CN1049697C - Steel sheet having excellent processing characteristics manufacturing method therefor, and galvanized steel sheet and resin coating steel sheet - Google Patents

Abstract

To produce a cold rolled steel sheet good in punching workability and free from the generation of burrs by prescribing the king and quantity of each contained element in a steel compsn. and deciding the content of Ti from the relationship among each content of C, N and S. The compsn. of a cold rolled steel sheet is composed of the one satisfying the requirements of, by mass, <=0.008% C, <=1.0% Si, 0.25 to 1.0% Mn, <=0.1% P, 0.01 to <0.025% S,% 0.1% Al, <=0.01% N and <=0.2% Ti, also satisfying 4<=Ti*<=C; where Ti*=Ti-[48/14N+(48/32)S], and the balance Fe with inevitable impurities. By this compsn., the quantity of Ti4 C2 S2 to be formed in the steel sheet and the dispersing state thereof are controlled, by which the cold rolled steel sheet satisfying all of formability, punching workability and surface properties can be obtd.

Description

Excellent processing characteristics steel plate and preparation method thereof

Hot-rolled steel sheet and cold-rolled steel sheet are widely used in various uses, as the outside plate of automobile and household electrical appliance, because they have the characteristic that satisfies various different purposes.Such as, be used for computer and household electrical appliance, often need punch process movable floor parts as the metal sheet of VTR (video tape recorder) and tape recording machine bottom board.Any burr that protrudes in this parts surface specified altitude does not have on the interdisciplinary theory of these parts.Such as, the head that changes that many times forms the axle of VTR head punches, but when jagged, then this plug can not be inserted when assembling.Also have, ought place the surface that is stamped when slide unit blocks maybe.And can not work well the time, or when rupturing and cause short circuit current, " burr " can cause a lot of troubles.

Routinely, low-carbon (LC) Al killed steel often is used to the purposes of this kind material, but as is used for the purposes that punching press is handled.In this carbon aluminium-killed steel, carbon is separated out in the coarse-grain granulosa of crisp cementite (iron carbide), this is to the effect of having cracked when punch process, so that burr seldom occurs, and the shear loading of wearing and tearing is always very little, the precipitate of MnS has same effect to the generation of crackle, and the equifinality that cementite produces is proved.

The precipitate of similar cementite and MnS is being an a crucial factor aspect the flow of metal ability of Control Critical, and its two second phases that produce the source as crackle cause a lot of problems in extruding flanging and stretching flanging process.Therefore, even the punch process of carbon aluminium-killed steel is fine, but the edge of their incompatibility stamping surfaces must bear secondary processing, handles as forming flanging or stretching hemmed.

On the other hand, be the more complicated shape that produces final machinofacture recently, and also will satisfy the user that the flanging characteristic and the stretching flanging of product processing also must reach good degree to the more requirement of the press forming of simplification.Recently,, adopt ultralow-carbon to add the carbon-nitrification element of specified amount in a large number, as the IF-base steel of specified amount titanium or niobium for satisfying these demands.

This have a low yield strength, and the steel of the IF-base of high-elongation and superior press formability is used as the part material that is attended by the processing of height material deformation widely, as, the car body material.Yet conventional IF-base steel has some shortcomings, as: compare with carbon aluminium-killed steel, pressworkability is very poor, and after the punching press big burr is arranged on the edge.The disposal to smear metal when final surfaceness and machining is also unsatisfactory, so this can not be used IF-base steel by special purpose.

In other words, for the pressure forming that---mainly is that metal sheet is stamped to form---for household electrical appliance and trolley part, although above-mentioned IF base steel has superior plasticity, but still it is inapplicable, to compare press formability poor because it is with carbon aluminium-killed steel, and big burr is arranged on the edge at this steel after the drawing.Such as, when being used for trolley part, the sticking power in steel cross section that has these burrs is very poor, and this causes the ill effect of corrosion and so on.Other problem is, so that during shipment, owing to burr produces metal powder in the abrasion of transportation, it scratches the surface of product thereupon when the metal sheet after the punching press being piled up in the cabin.A lot of purposes need be holed or car goes out screw thread, but this bad finished surface roughness of IF base steel and mach smear metal processing are regarded as shortcoming.

In order to improve press formability (and the processibility in the machining process), the method that the back is talked is feasible.But although in fact have only part metals in fact to be stamped, but the mechanical property of these metal other parts is inevitable impaired, and this has caused the undercapacity that will become serious problems.

Tried multiple processing method and improved the be stamped quality at position of steel plate, as correct cleaning with adopt various punching presses and the mold pressing model.Various methods at workpiece material have been proposed, as, the sclerosis on the sclerosis of steel plate or steel plate top layer.The specific example that a kind of steel plate hardening process is arranged is to add such as phosphorus to strengthen the sosoloid element.Another is special, and to make the case-hardened example of steel be that low annealing back imposes the method for plastix strain by rolling this steel plate to its upper layer, or make the method (spy opens flat 1-255626,2-133561,3-199343 and 3-202442) etc. of surface carburization or carburizing.Yet by this manufacturing process, though the punch process property improvement, the basic mechanical property of steel plate greatly worsens as unit elongation and γ value.By the method for a kind of nitriding in back or carburizing, need special equipment.The method that produces a large amount of MnS precipitates by interpolation manganese and sulphur also proposes (spy opens flat 1-230748 and 6-73457).But these methods have increased the sulphur content in the steel widely, and this not only makes steel easy to crack in hot procedure, but also frequent appearance and the pore spot defect relevant with bubble take place and the new problem of relevant surface imperfection with crackle.

In view of mentioned above, it or not the requirement of satisfying comprehensive gratifying shaping, but this steel also has to satisfy the requirement of good cutting and pressworkability aspect, these requirements are the requirements to this steel of household electrical appliance and trolley part, what press for is not the additive that rolls up as sulphur, but it is close with ultra low carbon IF base steel to develop a kind of component, and also has the steel of the improvement of good shaping and punch process characteristic.

To steel galvanizing, on galvanizing surface, be coated with plastic layer then as protection against corrosion with improve outward appearance, or the basic skills that produces impression of the hand (improving anti-impression of the hand) when suppressing touch is known.But the steel plate that is used for electrical equipment base plate or electric installation shell must have assembly electrical ground usually, and this makes the electroconductibility of this part become a fundamental characteristics.In order to ensure this electroconductibility, plastic layer just can not be thick in the degree that is enough to guarantee anticorrosive or anti-impression of the hand ability.Be head it off, proposed to give steel galvanizing, then improve anti-impression of the hand ability and still fall the method for the surface conductivity of this steel ground connection that is enough to provide enough simultaneously with as thin as a wafer organic plastics layer.This organic plastics layer as thin as a wafer seems not enough for the requirement of satisfying simultaneously electrical ground with anti-impression of the hand ability.Therefore, still need to develop a kind of have gratifying electrical ground with the surface-treated steel of anti-impression of the hand performance.

Consider above-mentioned situation, the objective of the invention is to provides a kind of steel by adjusting chemical ingredients well, this steel keeps the good shaping and the machinability of IF base steel plate, and the problem of inside or surface imperfection does not appear, but also good punch process is provided, do not occur and there is burr.

Another purpose provides good shaping, and this not only shows in the present invention deep-draw and extrusion molding, but also presses afterwards flanging processing and stretching flanging that good processing characteristics is arranged to this steel drift.

Another object of the present invention is by make basic raw material reaches provides good machinability or processibility at its surface galvanizing steel plate galvanized with above-mentioned steel plate.

Still a further object of the present invention is to provide and have good resistance corrosion and impression of the hand ability by be coated with plastic layer on whole galvanizing surface, and don't loses the steel plate of the plastic layer of grounded capacity.

The present invention also has a purpose to provide to make the method for the steel with above-mentioned characteristic, and is promptly stable and be suitable for method by industrial-scale production.

Ladle of the present invention is drawn together the following following column element of representing content with weight %:

Carbon: 0.0010-0.010% is more preferably 0.0010-0.008%;

Silicon: 1% or still less, be more preferably 0.25% or still less;

Manganese: 0.1-1.0% is more preferably 0.2-1%;

Phosphorus:, be more preferably less than 0.05% less than 0.1;

Sulphur: 0.01-0.025%;

Nitrogen: less than 0.01%;

Titanium:, be more preferably less than 0.15% but also will satisfy less than 0.2%:

(Ti ^*/48)/(C/12+S/32)＝0.8-4.0

Yet,

Ti ^*＝Ti-(48/14)N

Inside mainly comprises Ti ₄C ₂S ₂And all the other are iron and inevitable impurity.

Mainly by Ti ₄C ₂S ₂The precipitate size that constitutes is preferably 1000-10000 , is 5 * 10 and separate out quantity ³Individual/mm ²(preferably less than 5 * 10 ⁵).

Steel of the present invention is through cold rolling or hot rolling, when hot rolling, by described (Ti ^*/ 48)/(C/12+S/32) value of being calculated is in the scope of 1.0-3.0, and mainly is Ti ₄C ₂S ₂Precipitate be of a size of 1000-10000 , and the quantity of described precipitate is preferably 5 * 10 ³Individual/mm ²

When cold rolling, by described (Ti ^*/ 48)/(C/12+S/32) value of being calculated is in the scope of 0.8-4.0, and is more preferably in the scope of 1.0-2.5.Mainly be Ti ₄C ₂S ₂Precipitate remove Ti ₄C ₂S ₂Also contain TiS outward, and it is of a size of 1000-10000 , its quantity is preferably 5 * 10 ⁵Individual/mm ²

Described hot-rolled steel or cold-rolled steel can use by its present state, and its surface can be zinc-plated to improve resistance to corrosion and outward appearance.By the present invention, this method is included in hot rolling or at least one side of cold-rolled steel sheet forms 3-4g/m ²Zinc coating, on the zinc coating of steel, form 1-2.5g/m then again ²Plastic coating.The plastic coating of this steel plays a part the anticorrosive and anti-impression of the hand ability of further improvement.

The present invention is a feature with the method for making this hot rolling or cold-rolled steel sheet also.Preferred composition by this hot-rolled steel making method has satisfied the composition to the described element of this hot-rolled steel sheet condition, and then, by described (Ti ^*/ 48)/(C/12+S/32) value of being calculated drops in the scope of 1.0-3.0, and at this steel behind 1100-1200 ℃ temperature range internal heating, at (Ar ₃Transition temperature+80 ℃) to (Ar ₃Transition temperature-40 ℃) it is rolling to finish thermoforming in the temperature range, then batches in being lower than 700 ℃ temperature range and produces inside mainly by Ti ₄C ₂S ₂The precipitate of forming, it is of a size of 1000-10000 , and its quantity is 5 * 10 ³Individual/mm ²

The preferred kind of this cold-rolled steel manufacture method is characterised in that chemical ingredients satisfies previous listed element, and then by (Ti ^*/ 48)/(C/12+S/32) value of being calculated drops in the scope of 0.8-4.0.Behind the temperature range internal heating of this steel, at (Ar at 1100-1200 ℃ ₃Transition temperature+80 are ℃ to Ar ₃Finish hot rolling in the temperature range of transition temperature-40 ℃.Batch in the temperature range between 600-700 ℃ then, after steel cold rolling, anneal so that produce inside mainly with Ti ₄C ₂S ₂The precipitate of forming, it is of a size of 1000-10000 , and its quantity is 1 * 10 ⁴-5 * 10 ⁵Individual/mm ²

Fig. 1 represents that sulphur content is to the curve of burr height in the punching press course of processing and the influence of γ value in the steel

Fig. 2 is the curve of sulphur content and surface crack generation exponential relationship in the expression steel.

As mentioned above, steel of the present invention (hereinafter comprise cold rolling and hot-rolled steel two kinds), the composition, it mainly is Ti that inside comprises in specific steel is arranged₄C ₂S ₂Or Ti₄C ₂S ₂With the precipitate of TiS, and described precipitate preferably has specific size and amount. These are the punching press characteristics that keep good with the similar condition of conventional ultra low carbon IF steel constituent basically and achieve success in the improvement that reaches aspect punching press and the machining characteristics.

More particularly, by sulfur content being kept minimum to improve punch process, it mainly is Ti that sulphur has formed₄C ₂S ₂Or Ti₄C ₂S ₂Precipitate with TiS, by size and the amount of suitably adjusting this precipitate, the defective of pointing out in the example of common process is avoided, and can obtain good shaping and pressworkability in the subsequent technique process, but also satisfies the steel of flanging processing and stretching flanging processability. For guaranteeing this good pressworkability, the burr height after the punch process should be less than 25 μ m, and are more preferably less than 15 μ m.

Usually, punch process is at room temperature carried out, and material temperature does not rise basically, because obtain the described result of improvement, and with regard to the situation of precipitate and field trash, size and the requirement of distribution aspect are at room temperature processed. Also have, when machined, temperature is quite high, thereby the field trash in the material must be the type that desirable material machining characteristics can be provided by melting (field trash) in the temperature range that occurs when the machined. Mainly by Ti₄C ₂S ₂The precipitate that forms is endowed these whole characteristics, and the machined aspect large improvement, be proved such as punch process. With Ti₄C ₂S ₂Compare, the TiS precipitate is large, and can cause blemish, but when its size was in the scope of 1000-10000 , this blemish can not occur, and hot-working and the punch process characteristic improved are proved to be and Ti₄C ₂S ₂Material is the same.

As if but when the microscope grade was observed the steel plate that is stamped, the surface of shearing at first was accompanied by the drift that falls in the front and back of steel plate and forms with contacting of steel plate. The stress that concentrates on the described shear surface causes increase detrusion, thereby causes the formation in hole, and they form crackle subsequently, and said crackle becomes larger in steel plate front and the back side, and these crackles have just obtained stamping steel plate when combining. Therefore, it is effective promoting the development of above-mentioned hole and crackle will prove aspect the burr size after reducing punch process. Yet, at Ti₄C ₂S ₂And among the TiS, these precipitates are sizable, so that near the development strong detrusion place of crackle and hole carries out, and the result, punch process is obviously improved, and the burr size has also reduced.

On the other hand, aspect the stretching flanging, the edge in the hole that punching press forms broadens in what is called " crimping " process of carrying out by means of taper or cylindricality drift. The hole forms in the crystal boundary junction, and becomes the crackle that penetrates this steel. Therefore, preferably reduce the amount of precipitate and field trash, they are to promote to form these holes and crackle.

As can be seen, because the size of precipitate and field trash is given different effects to punching press with the deburring characteristic. The following exploration of the inventor confirms, among various precipitates and field trash, if Ti particularly₄C ₂S ₂Or Ti₄C ₂S ₂Be controlled as optimised quantity with size and the dispersion amount of TiS, then punch process and stretching flanging double goal can reach and without planar defect.

Also have, the precipitate in ultra low carbon IF steel and field trash are except the MnS and the Al that usually contain in the steel₂O ₃, also comprise the additives of titanium outward, such as TiC, Ti₄C ₂S ₂、TiS、TiN、FeTiP、Ti ₂O; And contain Nb (C, N) in the steel of niobium additive. They are with respect to separately size and be distributed with separately characteristic, and in the formability of observing steel, after machinability, punching press and the deburring characteristic, following corresponding data is proved.

Ti ₄C ₂S ₂，TiS：

If Ti₄C ₂S ₄Precipitate is of a size of 1000-10000 , is 5 * 10 for its amount of hot-rolled steel³Individual/mm²Or more, for cold-rolled steel 1 * 10⁴-5×10 ⁵Individual/mm²Between, so not only machinability and punch process are obviously improved, and to the formative of burr etc. in fact also without harmful effect. Difference between the permissible dose between above-mentioned hot rolling and cold-rolled steel is because cold-rolled steel requires the cause of high and surface accuracy. Because excessive described precipitate detrimentally affects the possibility of surface accuracy, so cold-rolled steel is provided with this restriction. To satisfy and the following Ti that mainly contains₄C ₂S ₂The steel billet of the relevant condition of precipitate composition in 1100-1200 ℃ temperature range, heat, then at (Ar₃Transition temperature+80 ℃) to (Ar₃Transition temperature-40 ℃) finishes the shaping hot rolling in the temperature range. For hot-rolled steel, this material is then rolled in the temperature range that is lower than 700 ℃. But for cold-rolled steel, then after hot rolling, then carry out with conventional method cold rolling after in 600-700 ℃ of scope for batching, anneal with effective technique. When the above-mentioned steel billet of heating, TiS can be at Ti₄C ₂S ₂The terminal stage that generates is separated out. The size of TiS is when finishing hot rolling and Ti₄C ₂S ₂Size to compare be sizable so that when adopting hot rolling blemish may appear. Therefore, when in fact adopting this steel, condition must be set with restricted T iS precipitate as much as possible.

Yet, after hot rolling, carry out cold rolling in, large TiS precipitate is broken into fritter when cold rolling, and in the annealing process of back, find hardly the increase of TiS precipitate, so but the pressworkability that improves is kept, and the harmful effect that causes blemish then is eliminated, show and Ti to change₄C ₂S ₂Identical effect. Being stranded this, mainly is being Ti when adopting₄C ₂S ₂Precipitate contain the cold-rolled steel of TiS the time, can obtain the obvious improvement of press formability aspect, prerequisite is, the size of this precipitate remains within the 1000-10000 , its amount remains on 1 * 10⁴-5×10 ⁵Individual/mm²Within.

Also have, will reduce with the deviation of the optimum condition of heating-up temperature and hot rolling and mainly contain Ti₄C ₂S ₂Or Ti₄C ₂S ₂And the amount of the precipitate of TiS, so that show that not only the improvement of punch process and stretching flanging aspect is very poor, and generation can cause that the shaping to steel plays the TiC of illeffects, thereby not reach purpose of the present invention.

TiC，Nb(C.N)：

When this precipitate is about 100 , because should be undersized, so that not only the shaping of steel produced and be harmful to effect, and the improvement of press formability aspect be also very poor. A kind of compound by interpolation titanium and niobium in the ultra low carbon IF cold-rolled steel improves the punch process of this steel and the technique of shaping is known (Japanese Patent Publication, flat 6-73457). But, the inventor's evaluation certificate, the niobium that adds in the 0.003-0.03% scope in steel produces Nb (C.N) in steel, and consumes carbon, and the result does not produce improving punch process and the effective Ti of stretching flanging₄C ₂S ₂, thereby do not reach purpose of the present invention.

FeTiP：

Be similar to Ti although fold the size of thing FeTiP₄C ₂S ₂Size and to improving punch process and stretching flanging performance is effective, yet owing to membranaceous precipitate occurs at crystal boundary, so that the rapid variation of the shaping of steel.

TiN

Although the size of precipitate TiN is similar to Ti₄C ₂S ₂Size, and obtains the identical result that improves, but because it is excessively soft in actual applications, thereby almost can not measure any improvement aspect the punch process, and the improvement aspect the stretching flanging is very poor. In addition, the rising of temperature has reduced cutting effect during owing to machined, so machined is unsatisfactory. Nitrogen content also is difficult to adjust, and the effective improvement that consequently contains machinability, stampability and the stretching flanging aspect of the steel of this titanium compound is difficult to reach.

Ti ₂O：

The size of this precipitate compares Ti₄C ₂S ₂Size large, thereby the improvement of the limit property aspect of punch process and stretching is poor. In addition, since possible blemish, TiO₂Undesirable.

MnS：

MnS has field trash and precipitate, the former is 1/10 of the former size take micron as the latter of unit, when sulphur increases, the field trash piece that increases means that punch process is enhanced, but as shown in the Japanese Patent Publication 6-73457 that formerly mentions, improve punch process sexual needs 0.02% or more sulphur, a large amount of sulphur can cause shaping variation and blemish.

As implied above, in containing the IF-base steel of Ultra-low carbon titanium, obtaining and produce field trash and precipitate, the combination of multiple possible compound is arranged. In these various compounds, precipitation size is the Ti of 1000-10000 ₄C ₂S ₂(or Ti₄C ₂S ₂And TiS) to punching press and the good effect of stretching flanging demonstration, and do not cause adverse effect to being shaped. In addition, if suitably adjust composition and the machined condition of this steel plate, take cause precipitate mainly by its amount as 5 * 10³Individual/mm²Or more Ti₄C ₂S ₂Or (Ti₄C ₂S ₂And TiS) forms (for hot rolled steel plate), and on the other hand, cold-rolled steel sheet is then remained on 1 * 10 with this amount⁴-5×10 ⁵Individual/mm²Scope in, so these characteristics then can be extremely effectively mode be proved. These new knowledges have become basis of the present invention. Below, clarify the reason of setting steel plate chemical composition of the present invention.

C：0.0010-0.010％

Carbon combines with titanium and generates Ti ₄C ₂S ₂, it is indispensable element.Carbon content must be at least 0.0010%, and still, if carbon content is excessive, the TiC amount that is then produced increases and the ductility or the unit elongation decline of metal thereupon, and yield strength rises, and shaping and stretching-flanging are subjected to injurious effects.In view of the above fact, for guaranteeing good shaping, on be defined as 0.010%.

Si:1.0% or still less

Silicon is to improve intensity and the effective element that do not lose ductility or unit elongation, but when silicone content was too high, the zone of oxidation that produces during annealing is looked very big, and follow-up forming process is produced harmful effect, but also causes the uneven distribution of zinc coating.Owing to these reasons, silicone content is limited to 1.00% or still less, moreover, in the alloy molten galvanizing process of steel plate, tend to occur ungalvanized position, so preferably silicone content is limited to 0.20% owing to forming described zone of oxidation.

Mn：0.1-1.0％

Manganese produces MnS, is the auxiliary element that improves stretching-flanging and punch process.For showing these improvement effectively, manganese content is necessary for 0.10% or more.Yet, when this content is excessive to being shaped and the generation of stretchings-flanging is harmful to effect, so manganese content must be limited to 1% or still less.

P:0.1% or still less

Phosphorus is suspended in the steel or forms the FeTiP precipitate, and in the previous case, phosphorus is strengthening element, then produces harmful effect on the contrary to being shaped.Under latter event, owing to form precipitate, improvement is arranged slightly, but the extreme difference that influences to being shaped so find punching press and stretching-flanging, so phosphorus should be limited to 0.1% or still less, better be to be limited to 0.05% or still less.

S：0.01-0.025％

Sulphur combines with the titanium of mentioning later and is mainly to contain Ti in formation ₄C ₂S ₂Or (Ti ₄C ₂S ₂During and TiS) precipitate is indispensable element, improves punch process, Ti for these precipitates are shown ₄C ₂S ₂Or (Ti ₄C ₂S ₂And TiS) amount is necessary for 5 * 10 ³Individual/mm ²Or it is more.Therefore sulphur content is necessary for 0.010% or more.These effects were maximum at 0.025% o'clock, and when this content.When being exceeded, not only press forming is produced harmful effect, and surface imperfection is tending towards increasing, so will be defined as 0.025% on it.

By the way, Fig. 1 is to be the steel plate of 0.0052% carbon, 0.01% silicon, 0.4% manganese, 0.014% phosphorus, 0.03% aluminium, 0.08% titanium and 0.006% nitrogen at basal component, the expression sulphur content is from 0.002% curve that changes to punch process and γ value at 0.037% o'clock, in this figure, be used as control sample through the Al of box annealing type killed steel (C:0.044%, Al:0.045% have good punching press and machining characteristics).Fig. 2 represents the relation curve of sulphur content and surface imperfection ratio.

Carry out the physicals experiment by following mode.The forged 40Kg metal base of vacuum melting is heated to 1200 ℃, roughing is that thickness is the steel plate of 30mm then, then, after this base is heated to 1200 ℃, at thickness of slab is 4mm, outlet temperature is 920 ℃ or higher, rolling temperature be under 680 ℃ the condition with its hot rolling, then be cut into the steel plate that thickness is 3.2mm.Then this metal is cold-rolled to the steel plate that thickness is 0.8mm, and at 1 minute, after the continuous annealing of 800 ℃ of medial temperatures, carries out 1% rolling adjustment, the result produces the laboratory sample cold-reduced sheet.The one test sample of determining 10mm * 110mm is used to do the test of γ value, and surveys width and thickness of slab when the tension strain that applies 0-15%.At thickness is on the 0.8mm cold-rolled steel sheet, and the gap with 9% stamps out the annular back of 10mm diameter and surveys burr height, then assessment at the edge.To this surface of cold-rolled steel plate range estimation surface imperfection, the percentage ratio of the surface imperfection that occurs by finding on regular length is then estimated.

As the clear expression of Fig. 1 and Fig. 2, when sulphur content less than 0.01% the time, the burr height of punching course is very big, thereby does not reach purpose of the present invention.But sulphur content surpasses at 0.025% o'clock, and surface imperfection rolls up again, finishes thereby hinder the object of the invention.But when sulphur content is 0.01% or more and 0.025% or still less, surface imperfection and burr height can be limited as much as possible, and obtain high γ value.

Data among Fig. 1 and 2 show the influence that physical property produced of sulphur content to cold-rolled steel, and this influence is with very identical to the influence of the hot-rolled steel before cold rolling the carrying out.Sulphur content is fixed in the scope of 0.001-0.025%, free of surface defects is proved to be correct owing to the hot-rolled steel sheet of producing has good punch process.

N:0.01% or still less

Nitrogen combines with titanium and produces TiN, but in fact TiN has no effect to improving the punch process ability.With carbon bonded situation under nitrogen weaken the stretching-flanging and the tensile property of steel, therefore for avoiding this shortcoming to be defined as 0.01% on it.

Ti:0.2% or still less

Owing in steel, produce Ti ₄C ₂S ₂Or (Ti ₄C ₂S ₂And TiS) precipitate, and to pressworkability and stretching flanging performance generation improvement, so titanium is one of most important element.The lower value of titanium content must be decided according to the content of nitrogen in steel, sulphur and carbon.But the maximum level that reaches effect of the present invention is 0.2%, and higher content is not effective cost.Preferably titanium content is 0.15% or still less.

Remove and form Ti ₄C ₂S ₂Outside TiS, titanium also can form TiN according to the nitrogen of condition and solid solution, or forms TiC with the carbon of solid solution.The lower value of titanium must by consider they separately effect and decide based on the content that following formula (1) is pressed carbon, sulphur and nitrogen.When forming hot-rolled steel, this value should be in the scope of 1.0-3.0, for cold-rolled steel then in the scope of 0.8-4.0, and the content of various elements according to the adjustment that concerns of other element.

(Ti ^*/ 48)/(C/12+S/32) ... formula (1)

And Ti ^*=Ti-(48/14) N.

But for hot-rolled steel, when this value during less than the value in the formula (1), titanium content is for being not enough with combining of carbon and sulphur, and generation is improved the required Ti of punch process ₄C ₂S ₂Also be not enough.But when this value surpasses 3.0, and carbon content is when also excessive, and then the carbon content of solid solution increases, or when sulphur content is excessive, then produce MnS and big TiS, so that no matter under which kind of situation, ductility and unit elongation are very poor, and can not get being shaped fully and the processing of stretching-flanging.In cold-rolled steel when by the value of above-mentioned formula (1) less than 0.8 the time, titanium content is for being not enough with combining of carbon and sulphur, and to improving the required Ti of punch process ₄C ₂S ₂Also be insufficient.But when this value surpasses 4.0, and carbon content is when also excessive, and then the carbon of solid solution increases, or when sulphur is excessive, produces MnS, so that no matter under any circumstance, ductility and unit elongation are very poor, and can not get shaping and the processing of stretching-flanging fully.Under the situation of cold-rolled steel, when the value by above-mentioned formula (1) gained has certain permission limit, because, when the hot rolling of carrying out before cold rolling finishes, even produce some big (thick) TiS, and the follow-up cold rolling thinner particle that also it can be broken into, like this expection to the influence of surface accuracy without any big problem.

Al:0.1% or still less

Aluminium is a kind of like this element: it is basic with indispensable adopting it as reductor.Too high aluminium content is with nonmetal Al ₂O ₃Be the source of the inclusion of base, it brings harmful effect to mechanical characteristics and machining, thereby aluminium content is restricted to 0.1% or still less.

When the singularity ability precipitate of steel of the present invention to have the Ti of being mainly ₄C ₂S ₂Or (Ti ₄C ₂S ₂And TiS) composition, and when the size of 1000-10000 scope is contained in this steel, machining, punching press and draw and stretch flanging and obviously improve, and to the no harmful effect that is shaped.But in steel, produce this Ti that is mainly of optimum quantity ₄C ₂S ₂The steel plate of precipitate create conditions, and temperature and the condition of batching during hot rolling are basic.Verified, for finishing purpose of the present invention, will satisfy in the scope that steel billet that above-mentioned chemical ingredients requires is heated to 1100-1200 ℃, at (Ar ₃Transition temperature+80 ℃) to (Ar ₃Transition temperature-40 ℃) it is rolling to finish thermoforming in the scope, and it is enough batching in 600-700 ℃ temperature range then.

If the Heating temperature of this moment is lower than 1100 ℃, the amount of the MnS that is produced increases, the Ti in the steel ₄C ₂S ₂The amount of precipitate will reduce.If heating surpasses 1200 ℃, then precipitate all dissolves, thereby can not get the Ti of correct amount ₄C ₂S ₂Fold thing.Also have, when the thermoforming rolling temperature surpasses 700 ℃, with Ti ₄C ₂S ₂For the precipitate of base then becomes the precipitate of FeTiP for base, thereby can not obtain the present invention desired improved machinability and punch process.Do not establish special value for coiling temperature and make its lower limit, but as low excessively, then not producing with Ti is the precipitate of base, even or produced TiC and also can not get Ti ₄C ₂S ₂Precipitate, thus 500 ℃ or higher temperature suit.If the coiling temperature when making cold-rolled steel sheet is low excessively, then the TiC precipitate is incomplete, and the residual carbon amount of solid solution will make annealed γ value variation, thereby, preferably coiling temperature is fixed in 600-700 ℃ the scope.

As long as keep above-mentioned heating and coiling temperature, even hot finishing temperature a bit changes, to Ti ₄C ₂S ₂Generation is not influence almost.But,, preferably finishing temperature is fixed on (Ar for obtaining level and smooth hot rolling and the hot-rolled steel sheet of stable machinability and shape of product being arranged ₃Transition temperature+80 ℃) to (Ar ₃Transition temperature-40 ℃) in the temperature range.But cross when low when hot finishing temperature, produce FeTiP.The carbon of this FeTiP and solid solution makes compression moulding characteristic variation.On the contrary, when hot finishing temperature was too high, the amount of big (slightly) TiS of generation increased, and this becomes the origin of surface imperfection especially when using this hot-rolled steel sheet.But when through cold rolling and when using with cold-rolled steel sheet, above-mentioned big (slightly) TiS is broken into fritter in cold-rolled process, thereby does not become the origin of surface imperfection.When reality was used this cold-rolled steel sheet, these TiS precipitates were the effective constituent of improving punch process.

There is not particular restriction for the cold rolling and annealing conditions that carries out after the hot rolling, but the Ti for will when hot rolling, producing ₄C ₂S ₂The optimum size of precipitate and dispersion amount keep the ideal effect, 700 ℃ or higher and Ac when the overdraft of setting 60-85% and back annealing ₃Point or following temperature are more desirable and set 750-850 ℃ temperature range.If be used for the overdraft of above-mentioned setting cold rolling, even there is the precipitate of the TiS of (slightly) greatly for base inside after finishing hot rolling, these precipitates also will be broken into fritter in cold-rolled process, to not become the origin of surface imperfection like this, and this precipitate is proved to be the active principle of the punch process that is improved.

Hot rolling that obtains like this or cold-rolled steel sheet can use like this, or and then electro-galvanizing, or molten zinc plating is with antirust, or carries out chemical treatment, handles or chromate treating as acid-alkali.Therefore, organic plastics coating or similar processing will confirm certainly as surface treatment it is effective.

In fact have only a few cases steel plate base to use without certain surface-coated.This be because use like this heat or cold-rolled steel sheet externally in the atmosphere short period of time promptly produce red rust.This corrosion intrusion metal not only reduces its intensity but also drive element and circuit is produced harmful effect, and this is because the cause of the rust powder that comes off.Use surface treatment for preventing that producing corrosion is utmost point effective means.The present invention's Zinc alloy electroplating zinc, this demonstrates superior rust-proof effect and don't to being shaped and punch process generation harmful effect.

Multiple zinc-plate process is feasible, as steel plate being dipped in the molten zinc plating method of carrying out in the molten zinc plating solution, applying electric charge by the electrolytic solution that contains zine ion and make electro galvanizing at surface of steel plate metal refining zinc, and the steam that makes the zinc of evaporating state be attached to surface of steel plate adheres to zinc-plate process.Yet it is satisfactory adopting electro galvanizing in the present invention, even because adherent material is quite thin, exquisite outward appearance is arranged in the zinc coating, and distribution of material is even in the zinc coating, does not in fact have surface imperfection simultaneously.For making this electro-galvanized layer antirust effectively, zinc coating adheres to thickness and should be 3g/m ²Or it is more.If this adhesion layer deficiency then can not guarantee corrosion resistance or must form super thick plastic coating on this zinc coating, thereby lose property electrical ground.From the viewpoint of erosion resistance, do not have special restriction to adhering to galvanized layer thickness, but surpass 40g/m when it ²The time, even this layer done to such an extent that blocked uply can not obtain anti-corrosion effects.If the overlong time of galvanizing process, or the closure of zinc coating is low excessively, then peeling off of coating can occur, so its thickness should be limited to 40g/m ²

Except that pure zinc plating, electro-galvanized layer used herein also comprises the Zn-based plating layer that contains Ni, Co and Fe with zinc, maybe can be same pure zinc or the Zn-based plating layer of low plating, maybe may be dissimilar pre-zinc coatings, and zinc content can be 50% (weight) or more in zinc-plated type.

The electro-galvanized layer that forms is the antirust purpose that is enough to self to finish steel plate.For this steel plate is used as baseboard material, except that antirust, be preferably in this zinc coating and itself add anti-impression of the hand performance.Reaching this purpose utmost point effective means is to be coated with one deck plastic coating on electro-galvanized layer again.The preferable adhesion amount of plastic layer is at 0.1-2.5%g/m ²Scope in.When the plastic coating quantity not sufficient of adhering to, then can not get gratifying corrosion stability and anti-impression of the hand, otherwise, to measure when excessive when this, the electroconductibility of top layer descends, and ground connection property extreme difference.

Do not have special restriction for the resin Composition type that constitutes plastic layer, but the most frequently used resin is vinyl polymerization resin, vibrin, polyvinyl resin, acrylic resin, urethane resin, contains the polyamide resin of Resins, epoxy or ethylene unsaturated carboxylic acid's polymkeric substance.The resin of these types can be on demand separately or with two kinds or multiplely mix use.By changing the functional group in these resins with ordinary method, or strengthen them with crosslinker solution and be formed with the resin Composition of usefulness.In addition, improve anti-impression of the hand such as the silicon compound that can use organic or inorganic, the surface type that maybe the wax composition can be added to slightly when improving punch process in this resin scratches characteristic, maybe the wax component can be introduced in the reformer unit in the functional group in this resin.

Plastic coating is preferably as the surface protecting layer after the punch process, so that anticorrosive and anti-impression of the hand.For this reason, one or more blended resins in Resins, epoxy, vinyl polymerization resin, vibrin and the urethane resin are preferably as basic resin.

Preferably add the erosion resistance of further improving plastic coating such as silica granule, additional silica granule is such as the mineral compound that is silicon, its amount be about base resin weight 5% or more.But when silica granule content is excessive, it has played anti-slip material, the result has improved the coefficient of friction of coating, reduce its lubricating quality, deficiency in addition is to show after the machining to have reduced resistance to corrosion, so this content should be about 30% (weight) or still less, and be more preferably 10% (weight) or still less.

Can obtain the best effects of this silica granule with the particle size of 1～20 μ m.In other words, silica granule is more little, and then coating is meticulous more, thereby has improved stopping property.The result has improved the erosion resistance and the coating (coating deposition) of coating, if but particles usedly then can not obtain bigger effect less than 1 μ m, thereby it is enough to be limited to 1 μ m under the particle size.Otherwise when this size during greater than 20 μ m, the coatingsurface roughen can not form meticulous film, and erosion resistance is variation also.Therefore particle size is 4-6 μ m preferably.This silica granule is known as colloidal silica, and can buy such as trade name " Snow-Tex XS or Snow-Tex SS " (both make by NissanKagaku Kogyo, trade(brand)name).

Formation method to plastic coating does not have any particular restriction.With ordinary method former state hot rolling that method makes or cold-rolled steel sheet one or both sides and form electro-galvanized layer after, available required method, as roller coat, dip-coating or spraying that plastic layer is exhausted on whole galvanizing surface.Finish chemical treatment at galvanized steel sheet surface, after chromic salt or acid-alkali processing, form plastic layer this moment and will confirm to be effective aspect the stopping property of strengthening zinc coating with plastic coating.This coating is included in the technical scope of the present invention certainly.

Embodiment

The listed embodiment explanation of this paper of the specific embodiment of formation of the present invention and effect, these embodiments hereinafter described do not have any restriction to the present invention and can do further change in the scopes of spirit applicatory of the present invention, and foregoing is included in the technical scope of the present invention.

The performance test at tensile property, machinability, pressworkability that is adopted in the embodiment identifies that the type of precipitate in the steel plate and the method for amount are described in down below.

The evaluation of precipitate type and quantity:

By observing with the method that duplicated film extracts with transmission electron microscope.With 10000 times ratio of enlargement, at 0.15mm ²The visual field in seek the quantity of precipitate, calculate 1mm then ²Interior precipitate quantity.

Tensile property:

To be used to tension test by the test block that JIS5 makes, each is assessed for yield-point (YP), tensile strength (TS), unit elongation (El) and work hardening coefficient (n value).Evaluate non-aging performance (A.I) with the ascending amount of yield-point at 100 ℃ after handling 60 minutes again.

The γ value:

Adopt the test block of 10mm * 110mm.When the tension strain that applies 0% and 15%, measure the wide and thick of this test block.

Punch process:

Punching press has about 12% the gap and the ring sample of 30mm diameter, and measures and burr height that evaluation occurs on the edge.

Machinability:

Make the pipe of external diameter 60mm with high-frequency induction heating welding process every block of test block plate of weldering.The cutting-out speed that the cutting speed 0.06m/ that divides with 125m/ changes is cut.Multiplicity (life tools) and smear metal (waste cut materials) shape (GOOD=is little, the shape smear metal of curling, the curling shape smear metal that DEPECT=is long) are cut off in evaluation.

The stretching flanging:

On each test block plate, go out the hole of diameter 20mm.The hole of going out (dia/mm) is widened with the tapered punch of 30 ° of drift angles, runs through steel plate thickness up to crackle.Obtain the spreading rate in hole with following formula with aperture this moment (df:mm), evaluate the stretching flanging then.

The bore expansion rate=[(df-di)/di] * 100 (%)

Embodiment 1

After the steel billet of chemical ingredients such as table 1 is heated to 1180 ℃, set about 920 ℃ hot finishing temperature and 630 ℃ coiling temperature, finish the hot-rolled steel sheet that hot rolling obtains thick 3.2mm then.Remove tensile property, outside machinability and the pressworkability, also detect the precipitate type and the quantity that produce by in the hot rolling acquisition steel, the results are shown in table 2.

Table 1

Steel grade	Chemical ingredients (weight %)									Ar 3The point	The precipitate several months *1(individual/mm 2)	Annotate
													C	Si	Mn	P	S	Al	Ti	N	(Ti */48) /(C/12 +S/32)
	A	0.0052	0.02	0.32	0.013	0.017	0.032	0.078	0.0007													1.2	892	2.1×10 4	*2
B										0.0031	0.02	0.46	0.035	0.014	0.033	0.048	0.0027	1.2	877	1.6×10 4	*2
	C	0.0033	0.01	0.63	0.015	0.022	0.033	0.070	0.0028													1.3	865	3.7×10 4	*2
D										0.0032	0.01	0.94	0.016	0.018	0.034	0.076	0.0036	1.6	857	4.2×10 4	*2
	E	0.0129	0.02	0.37	0.016	0.008	0.032	0.115	0.0059													1.5	883	3.9×10 3	*3
F										0.0017	0.44	0.44	0.091	0.007	0.031	0.085	0.0041	4.1	874	3.2×10 3	*3
	G	0.0044	0.02	0.17	0.016	0.009	0.028	0.076	0.0045													2.0	905	2.3×10 3	*3
H										0.0035	0.01	1.15	0.014	0.006	0.031	0.066	0.0037	2.3	825	2.7×10 3	*3
	I	0.0032	0.01	0.44	0.088	0.008	0.036	0.074	0.0108													1.5	881	4.1×10 4	*3
J										0.0028	0.02	0.46	0.013	0.005	0.036	0.039	0.0034	1.4	868	2.8×10 4	*3
	K	0.0045	0.01	0.44	0.018	0.031	0.029	0.106	0.0045													1.4	876	2.3×10 5	*3
L										0.0055	0.01	0.42	0.015	0.016	0.031	0.055	0.0056	0.8	875	2.4×10 4	*3
	M	0.0007	0.01	0.45	0.021	0.022	0.035	0.077	0.0032													1.8	879	3.1×10 3	*3

* 1: the precipitate quantity that is of a size of 1000-10000 .Steel grade F and I have FeTiP alloy precipitate,

And other steel grade is Ti ₄C ₂S ₂Type alloy precipitate * 2: embodiment of the invention * 3: Comparative Examples

Table 2

Steel grade	Tensile property				The punching press characteristic	Machinability		Annotate
									YS (N/mm 2)	TS (N/mm 2)	The π value	El (％)	Burr height (μ m)	Life tools (inferior)	Smear metal is handled
	A	163	315	0.247	53	34	56									○	*1
B								158	324	0.251	53	24	53	○	*1
	C	159	328	0.242	52	29	48									○	*1
D								190	385	0.236	45	25	46	○	*1
	E	184	342	0.222	45	44	37									×	*2
F								224	436	0.203	36	38	29	×	*2
	G	162	318	0.242	50	65	39									×	*2
H								214	355	0.222	45	54	41	×	*2
	I	221	359	0.219	44	46	26									×	*2
J								153	317	0.244	49	57	17	×	*2
	K	164	323	0.231	46	37	43									○	*2
L								190	314	0.196	45	40	45	○	*2
	M	143	297	0.250	51	63	21									×	*2

* 1: the embodiment of the invention

* 2: Comparative Examples

The result of table 1 and 2 can be explained as follows:

Steel grade A, B and C are mild steel, and steel grade D is the high-strength steel that meets prescribed condition of the present invention.All these steel grades except that having good tensile property, also all have good punching press and machinability.

Otherwise the steel grade of E-J is because sulphur content deficiency and pressworkability and machinability are very poor.In addition, the carbon content of steel grade E is too high, so make the tensile property variation because of having produced TiC.The manganese too high levels of steel grade H is so make the pressworkability variation because of producing MnS.The carbon quantity not sufficient of steel grade M so that tensile property is very poor, also has poor pressworkability, because the Ti that produces ₄C ₂S ₂The throw out quantity not sufficient.Following does not show in table 2, but because the silicone content among the steel grade F is excessive, so silicon oxide layer causes variation in the zinc coating in the process of electro-galvanizing, and the closure of zinc coating is poor.In steel grade K, be proved to be because sulphur content is excessive,, differentiate surface imperfection on this external surface of steel plate after rolling, as pore and crackle even pressworkability can be satisfactory but tensile property is very bad.In steel grade F and L, the balanced differences of the amount of Ti and carbon in the steel is so that can not satisfy condition in the above-mentioned formula (1).The result is except that the tensile property balanced differences, and pressworkability is poor, and the ageing resistance performance is unsatisfactory.

Embodiment 2:

Adopt the steel grade B (Ar shown in the table 1 ₃877 ℃ of points).Except that Heating temperature, finishing temperature and coiling temperature have been done change as shown in table 3, carry out hot rolling with the method identical with embodiment 1.The wide 3.2mm of hot-rolled steel sheet.Except that the precipitate type and quantity that detect each test block, stretching and pressworkability have also been checked as embodiment 1.The results are shown in table 4.Table 3

Steel grade	Hot-rolled condition (℃)			Precipitate number and type are (individual/mm 2)	Annotate
						Heating temperature	Finishing temperature	Coiling temperature
	B1 B2 B3 B4	1230 1180 1145 1070	935 920 915 930						610 630 620 605	3.4×10 3TiS type 1.6 * 10 4Ti 4C 2S 2Type 1.0 * 10 4Ti 4C 2S 2Type 4.7 * 10 3The MnS type	*1 *2 *2 *1
B5 B6 B7				1175 1170 1180	995 895 825	630 630 625	3.5×10 3MnS type 3.6 * 10 4Ti 4C 2S 2Type 2.7 * 10 3The FeTiP type	*1 *2 *1
	B8 B9 B10	1190 1175 1185	915 930 920						735 580 525	3.8×10 3FeTiP type 1.9 * 10 4Ti 4C 2S 2Type 4.4 * 10 4Ti 4C 2S 2Type	*1 *2 *2

* 1: Comparative Examples * 2: the embodiment of the invention

Table 4

Steel grade	Tensile property				The punching press characteristic	Machinability		Annotate
									YS (N/mm 2)	TS (N/mm 2)	The π value	El (％)	Burr height (μ m)	Life tools (inferior)	Smear metal is handled
	B1 B2 B3 B4	163 158 157 155	327 324 325 319	0.249 0.251 0.247 0.244	51 53 52 49	44 24 27 41	46 53 49 37									× ○ ○ ×	*1 *2 *2 *1
B5 B6 B7								149 159 154	324 322 317	0.213 0.254 0.196	47 53 43	43 26 32	38 55 46	× ○ △	*1 *2 *1
	B8 B9 B10	162 153 166	320 328 336	0.218 0.246 0.237	47 43 48	38 31 35	30 50 44									× ○ ○	*1 *2 *2

* 1: Comparative Examples

* 2: the embodiment of the invention

Symbol B in the table 3 and 4 ₁-B ₄Show the optimal temperature scope of hot finishing temperature and coiling temperature.Particularly, when detecting the effect of Heating temperature, at 1100-1200 ℃ of (B ₂, B ₃) in the steel grade of scope internal heating, find with Ti ₄C ₂S ₂The precipitate that is base produces with suitable size and quantity, and tensile property and pressworkability are all good in each case.Otherwise at control sample (B ₁) when middle Heating temperature surpasses 1200 ℃, form the precipitate that is mainly TiS, and work as at control sample (B ₄) in this temperature when being lower than 1100 ℃, form the precipitate that is mainly MnS, and punch process and machinability inequality under these two kinds of situations.

Symbol B ₅-B ₇Show the optimum range of Heating temperature and coiling temperature.Particularly, when detecting the finishing temperature effect, find at 1100-1200 ℃ of (B ₆) scope in the steel grade that heats, produce the Ti of suitable size and quantity ₄C ₂S ₂The base precipitate, and in each case, tensile property and pressworkability are all good.Otherwise, at control sample (B ₅) in finishing temperature form the precipitate that is mainly MnS when too high, and at control sample (B ₇) in, cross when low when finishing temperature, form the precipitate that is mainly FeTiP, and punching performance inequality under these two kinds of situations.

Symbol B ₈-B ₁₀The optimal temperature scope of expression heating and finish to gauge.Particularly, when detecting the effect of coiling temperature, find the steel grade (B of coiling temperature in correct scope ₁₀, B ₁₁), that generation size and quantity are suitable is Ti basically ₄C ₂S ₂Precipitate, and stretch in each case and pressworkability all good.Otherwise, when coiling temperature at control sample (B ₈) in when too high, the precipitate that is mainly FeTiP forms, and can not get satisfied machinability.

Embodiment 3:

After the steel billet of the chemical ingredients that will be shown in table 5 is heated to 1180 ℃, set the coiling temperature of about 920 ℃ finishing temperature and 630 ℃, carry out hot rolling then.After obtaining the thick hot-rolled steel sheet of 3.2mm, it is thick that every hot-rolled steel sheet is cold-rolled to 0.8mm.Carry out 800 ℃, after 1 minute the continuous annealing, it is rolling to carry out percent 1 tempering.Detect separately stretching and pressworkability, then gained be the results are shown in table 5.

The precipitate type and quantity that in the cold-rolled steel that detects above-mentioned gained, is produced, also detect stretching, punch process and stretching flanging performance, and gained the results are shown in table 6.

Table 5

Steel grade	Chemical ingredients (weight %)										Ar 3The point	The precipitate number *1(individual/mm 2)	Annotate
														C	Si	Mn	P	S	Al	Ti	N	B	(Ti */48) /(C/12 +S/32)
	A	0.0052	0.02	0.32	0.013	0.017	0.032	0.078	0.0067	-														1.2	892	4.4×10 4	*2
B											0.0031	0.02	0.46	0.035	0.014	0.033	0.048	0.0027	-	1.2	877	3.1×10 4	*2
	C	0.0033	0.01	0.63	0.015	0.022	0.033	0.070	0.0028	-														1.3	865	7.7×10 4	*2
D											0.0032	0.01	0.94	0.016	0.018	0.034	0.076	0.0036	-	1.6	857	8.7×10 4	*2
	E	0.0129	0.02	0.37	0.016	0.008	0.032	0.115	0.0059	-														1.5	883	7.8×10 3	*3
F											0.0017	0.44	0.44	0.091	0.007	0.031	0.085	0.0041	-	4.1	874	6.5×10 3	*3
	G	0.0044	0.02	0.17	0.016	0.009	0.028	0.076	0.0045	-														2.0	905	4.1×10 3	*3
H											0.0035	0.01	1.15	0.014	0.006	0.031	0.066	0.0037	-	2.3	825	4.6×10 3	*3
	I	0.0032	0.01	0.44	0.088	0.008	0.036	0.074	0.0108	-														1.5	881	8.2×10 3	*3
J											0.0028	0.02	0.46	0.013	0.005	0.036	0.039	0.0034	-	1.4	868	6.9×10 3	*3
	K	0.0045	0.01	0.44	0.018	0.031	0.029	0.106	0.0045	-														1.4	876	6.3×10 3	*3
L											0.0039	0.01	0.55	0.013	0.043	0.032	0.125	0.0036	-	1.4	872	9.8×10 5	*3
	M	0.0050	0.01	0.46	0.014	0.017	0.033	0.050	0.0058	-														0.7	881	4.3×10 3	*3
N											0.0007	0.01	0.45	0.021	0.022	0.035	0.077	0.0032	-	1.8	879	5.2×10 3	*3
	O	0.0038	0.01	0.36	0.011	0.019	0.037	0.081	0.031	0.005														1.6	891	2.9×10 4	*2

* 1: the precipitate quantity that is of a size of 1000-10000 .Steel grade F and I have the precipitate of FeTiP alloy,

Other steel grade is Ti ₄C ₂S ₂Type alloy precipitate * 2: embodiment of the invention * 3: Comparative Examples

Table 6

Steel grade	Tensile property				The punching press characteristic	Stretching flanging performance	Annotate
								YS (N/mm 2)	TS (N/mm 2)	El (％)	γ (value)	Burr height (μ m)	Reaming limit (%)
	A	165	316	52	2.12	23								203	*1
B							158	327	51	2.03	17	216	*1
	C	157	331	51	1.97	20								198	*1
D							188	382	45	1.95	17	206	*1
	E	186	344	43	1.62	32								175	*2
F							221	430	33	1.74	28	151	*2
	G	158	318	47	1.80	45								197	*2
H							222	359	43	1.66	39	189	*2
	I	224	356	42	1.72	33								174	*2
J							155	321	47	1.84	42	205	*2
	K	164	327	44	1.85	36								162	*2
L							168	322	42	1.77	35	133	*2
	M	193	213	43	1.43	39								158	*2
N							143	298	50	1.99	51	194	*2
	O	183	322	49	1.94	16								203	*1

* 1: the embodiment of the invention

* 2: Comparative Examples

His-and-hers watches 5 and 6 result make description below.

In this embodiment, steel grade A, B and C are mild steel, and steel grade D is the high-strength steel that meets prescribed condition of the present invention.Steel grade O is an embodiment that contains element boron.All these steel grades also have good stampability and machinability except that good tensile property is arranged.

Otherwise the steel grade of E-J all makes pressworkability poor because of sulphur content is not enough.In addition, the carbon content of steel grade E is too high, so tensile property is bad owing to produced TiC.Steel grade H manganese too high levels, thus make tensile property and stretching flanging performance not good because of producing MnS.The carbon content deficiency of steel grade M, so tensile property is bad, and punch process and stretching flanging performance are also bad, and this is because the Ti that produces ₄C ₂S ₂The cause of the quantity not sufficient of precipitate.Under be listed in the table 2 not shown, but since steel grade F in silicone content too high, the silicon oxide layer that forms during electro-galvanizing causes the variation of zinc coating, thereby the stopping property of zinc coating is bad.Confirmed that in steel grade K because sulphur content is excessive, even pressworkability is satisfactory, but tensile property is also bad, and then, also be found on the surface of steel plate after rolling as the surface imperfection of pore and crackle and so on.In steel grade F and M, the balance of the amount of Ti and C is not good, thereby can not satisfy the condition of above-mentioned formula (1), and therefore, except that the tensile property balance was bad, pressworkability and stretching flanging performance were also poor, and the ageing resistance performance is unsatisfactory.

Embodiment 4:

Adopt the steel grade B (Ar shown in the table 5 ₃Point is 877 ℃).Remove Heating temperature, hot finishing temperature and coiling temperature are done outside the change as shown in table 7, carry out hot rolling with the method identical with embodiment 3.Hot-rolled steel thickness of slab 3.2mm, and then be cold-rolled to thickness of slab 0.8mm.Carried out 1 minute, after 800 ℃ the continuous annealing, it is rolling to carry out percent 1 tempering, and the result obtains cold-rolled steel.Detect tensile property separately, stretching flanging performance and pressworkability, gained the results are shown in table 8.

Table 7

Steel grade	Hot-rolled condition (℃)			Precipitate number and type are (individual/mm 2)	Annotate
						Heating temperature	Finishing temperature	Coiling temperature
	B1 B2 B3 B4	1230 1180 1145 1070	935 920 915 930						610 630 620 605	6.4×10 5TiS type 3.1 * 10 4Ti 4C 2S 2Type 6.3 * 10 4Ti 4C 2S 2Type 8.7 * 10 3The MnS type	*1 *2 *2 *1
B5 B6 B7				1175 1170 1180	995 895 850	630 630 625	5.5×10 5MnS type 5.2 * 10 4Ti 4C 2S 2Type 5.1 * 10 3The FeTiP type	*1 *2 *1
	B8 B9 B10	1190 1180 1175	915 925 930						735 680 580	3.8×10 3FeTiP type 3.6 * 10 4Ti 4C 2S 2Type 8.8 * 10 3Ti 4C 2S 2Type	*1 *2 *1

* 1: Comparative Examples * 2: the embodiment of the invention

Table 8

Steel grade	Tensile property				The punching press characteristic	Stretching flanging performance	Annotate
								YS (N/mm 2)	TS (N/mm 2)	El (％)	γ (value)	Burr height (μ m)	Reaming limit (%)
	B1 B2 B3 B4	164 156 155 161	326 327 322 323	49 51 50 47	1.81 2.03 2.11 1.88	32 13 19 36								179 216 196 181	*1 *2 *2 *1
B5 B6 B7							157 156 152	321 319 315	45 52 42	1.79 2.06 1.65	34 18 26	186 223 177	*1 *2 *1
	B8 B9 B10	160 150 178	328 323 335	45 50 42	1.61 1.94 1.60	30 21 30								175 194 173	*1 *2 *1

* 1: Comparative Examples * 2: the utility model embodiment

Symbol B in the table 7 and 8 ₁-B ₄Show the suitable temp scope of finishing temperature and coiling temperature.Particularly, when detecting the influencing of Heating temperature, at the steel grade (B of 1100-1200 ℃ scope internal heating ₂, B ₃) the middle discovery, generated the suitable Ti of size and quantity ₄C ₂S ₂Be the precipitate of base, and in all cases, tensile property, stretching flanging performance and pressworkability are all good.Otherwise, as comparative sample B ₁In Heating temperature when surpassing 1200 ℃, form the precipitate that is mainly MnS, and when at control sample (B ₄) in this temperature when being lower than 1100 ℃, form the precipitate that is mainly TiS, pressworkability inequality under these two kinds of situations.

Symbol B ₅-B ₇Show the optimum range of heating and coiling temperature.Particularly, when detecting the influencing of finishing temperature, be to have carried out in 1100-1200 ℃ the scope (B in the steel grade of heating ₆), find to have formed size and quantity suitable be mainly Ti ₄C ₂S ₂Precipitate, and tensile property, stretching flanging performance and pressworkability are all good in all cases.Otherwise, when at control sample (B ₅) in finishing temperature when too high, only form the MnS precipitate, and when at control sample (B ₇) in hot finishing temperature cross when low, then forming mainly is the precipitate of FeTiP, and under these two kinds of situations, pressworkability is all bad.

Symbol B ₈-B ₁₀Show the optimum range of heating and hot finishing temperature.Especially when detecting the influencing of coiling temperature, at the steel grade (B of coiling temperature in correct scope ₉) in, find to have produced size and the suitable Ti of quantity ₄C ₂S ₂With TiS be main precipitate, and tensile property, stretching flanging performance and pressworkability are all good in all cases.Otherwise, as control sample (B ₈) in coiling temperature when too high, form and be mainly the precipitate of FeTiP, and can not get gratifying stretching flanging performance.As control sample (B ₁₀) in coiling temperature cross when low, can not be mainly Ti with enough volume production lifes ₄C ₂S ₂With the precipitate of TiS, thereby punch process and a bit decline of stretching flanging performance.

Embodiment 5:

Steel grade A, the B that will adopt from the cold-rolled steel sheet of embodiment 3 and the cold-rolled steel sheet of C gained with ordinary method, at its surface galvanizing, thereby form 1-50g/m ²Zinc coating.Carry out chromate treating then, so that the chromium throw out that forms changes into 10mg/m on zinc coating ²Chromium metal.

The resin of vinyl, ester or urethane resin are used to be of a size of the colloid silicon grain that 4-6 μ m solid forms and mix with being transformed into, and it is for 10% part of proportioning in this resin, then with 0.05-3g/m ²Amount apply so that obtain surface-treated steel plate.Evaluate anticorrosively, anti-impression of the hand and ground connection performance the results are shown in table 9:

Erosion resistance:

Carry out the salt spray experiment by method listed among the JIS Z 2371, evaluation produces the time of 1% white corrosion then.

Zero=240 hour or more, *=less than 240 hours.

Anti-impression of the hand ability:

Test block is immersed in 40 ℃ the 50% white Vaseline solution, takes out then, measure and evaluation being coated with the Vaseline part and not being coated with fading of Vaseline part.The aberration (△ E) that is coated with and is not coated with between all dried woods parts is then represented good anti-impression of the hand for " 3 or still less ".

Zero=△ E is 3 or still less *=greater than △ E

Ground connection property:

Measure the surface conductivity of test block, evaluation result then with the surface resistivity that the experiment thing is separated by between the joint that 100mm settles.

Zero=surface resistivity is 200 Europe or littler

*=surface resistivity is 200 Europe or bigger

Comprehensive evaluation:

Zero=satisfied

*=dissatisfied

Table 9

№	Steel grade	The zinc adhesion amount	The resin kind *	Resin adhesion amount (g/m 2)	Erosion resistance	Anti-impression of the hand	Ground connection property	Comprehensive evaluation	Annotate
										1 2 3 4 5	A A B B C	15 10 20 40 30	Ethene ethene ethene urethane ester	0.5 0.5 0.1 0.3 2.5	○ ○ ○ ○ ○	○ ○ ○ ○ ○	○ ○ ○ ○ ○	○ ○ ○ ○ ○	Embodiment
6 7 8 9	B B B C	2 20 20 20	The ethene urethane does not have polyester	0.05 3.0 - 0.05	× ○ × ×	× ○ × ×	○ × ○ ○	× × × ×	Comparative Examples

* 1: the resinous type details

Ethene: contain the acrylic acid vinyl polymerization resin of 20% (weight) by what the ethylene unsaturated carboxylic acid constituted.

Fat: vibrin, the product of the commodity of making by Toye Bomeki Co " BYRON 20SS " by name.

Urethane: gather urethane resin, be called the product of " SUPERFLEX " by the commodity of Datichi Kogyk Chemical Co manufacturing.

The result of table 9 can be explained in following.

The electro-galvanized layer of embodiment № 1-5 and plastic coat chemical composition of steel and amount meet defined terms of the present invention.Also obtained the good erosion resistance of plate, the effect of anti-impression of the hand and ground connection property.

Otherwise, so № 6 is because the not enough anticorrosive and anti-impression of the hand of the adhesion amount of electro-galvanized layer and plastic coating is poor.Too much ground connection property is poor so № 7 is owing to be coated with plastics.So № 8 is not owing to be coated with the plastic layer erosion resistance and anti-impression of the hand is poor.So № 9 can not provide satisfied erosion resistance and anti-impression of the hand owing to be coated with the plastics quantity not sufficient.The present invention finishes as mentioned above, and except that the component of steel, especially with the content of titanium, sulphur, manganese and nitrogen as adjustment, and the mutual relationship of sulphur, nitrogen and carbon amount and titanium amount is suitably controlled, so that produce Ti with appropriate vol and size ₄C ₂S ₂Precipitate.This makes has the steel sheet of splendid pressworkability to be produced and don't lose its moulding and machinability.Method of the present invention also makes has the steel sheet of these performances to be able to producing reliably by technical scale.

Claims (9)

1. steel plate that excellent mechanical properties is provided, it comprises mainly by Ti ₄C ₂S ₄The precipitate and the following element of representing content with weight % that constitute:

Carbon: 0.0010-0.010%

Silicon: 1.0% or still less

Manganese: 0.1-1.0%

Phosphorus: 0.1 or still less

Sulphur: 0.01-0.025%

Nitrogen: 0.01% or still less

Titanium: 0.2% or still less

Surplus: Fe and unavoidable impurities, described element satisfies the condition of following formula:

(Ti ^*/48)/(C/12+S/32)＝0.8-4.0

Ti ^*＝Ti-(48/14)N。

2. according to the steel plate of the excellent mechanical properties of claim 1, wherein, precipitate inside mainly comprises Ti ₄C ₂S ₂, it is of a size of 1000-10000 , and quantity is 5 * 10 ³Individual/mm ²Or it is more.

3. according to the steel plate of the excellent mechanical properties of claim 2, wherein this steel plate is hot-rolled steel sheet and satisfies following formula:

(Ti ^*/48)/(C/12+S/32)＝1.0-3.0

Ti ^*＝Ti-(48/14)N。

4. according to the steel plate of the excellent mechanical properties of claim 2, wherein, this steel plate is a cold-rolled steel sheet, and mainly contains T ₄C ₂S ₂Precipitate, also comprise TiS and Ti ₄C ₂S ₂, and described precipitate is of a size of 1000-10000 , its amount is 1 * 10 ⁴-5 * 10 ⁵Individual/mm ²

5. according to the steel plate of each excellent mechanical properties among the claim 1-4, wherein this steel plate comprises the following element of representing content with weight %.

Carbon: 0.0010-0.008%

Silicon: 0.25% or still less

Manganese: 0.20-1.0%

Phosphorus: 0.05% or still less

Titanium: 0.15% or still less

6. according to the steel plate of claim 1, wherein at least one side of this steel plate is 3-40g/m with the amount ²Zinc-plated or galvanized alloy.

7. according to the steel plate of claim 6, wherein on described zinc-plated or galvanized alloy layer, form plastic coating, adhesion amount is 0.1-2.5g/m ²

8. manufacture method that has excellent mechanical properties and contain the hot-rolled steel sheet of the following element of representing content with weight %,

Carbon: 0.0010-0.010%

Silicon: 1.0% or still less

Manganese: 0.1-1.0%

Phosphorus: 0.1 or still less

Sulphur: 0.01-0.025%

Nitrogen: 0.01% or still less

Titanium: 0.2% or still less

Surplus: Fe and unavoidable impurities, described element satisfies the condition of following formula:

(Ti ^*/48)/(C/12+S/32)＝1.0-3.0

Ti ^*=Ti-(48/14) N, described manufacture method comprises step: at 1100-1200 ℃ the described steel of temperature range internal heating, then at (Ar ₃Transition temperature+80 ℃) to (Ar ₃Transition temperature-40 ℃) finishes hot rolling in the temperature range, then batch, be mainly Ti so that produce inside in the temperature range that is not more than 700 ℃ ₄C ₂S ₂, being of a size of 1000-10000 , quantity is 5 * 10 ³Individual/mm ²Or more precipitate.

9. manufacture method that has excellent mechanical properties and contain the cold-rolled steel sheet of the following element of representing content with weight %,

Carbon: 0.0010-0.010%

Silicon: 1.0% or still less

Manganese: 0.1-1.0%

Phosphorus: 0.1 or still less

Sulphur: 0.01-0.025%

Nitrogen: 0.01% or still less

Titanium: 0.2% or still less

Surplus: Fe and unavoidable impurities, described steel satisfies the condition of following formula:

(Ti ^*/48)/(C/12+S/32)＝0.8-4.0

Ti ^*=Ti-(48/14) N, described manufacture method comprises step: at 1100-1200 ℃ the described steel of temperature range internal heating, at (Ar ₃Transition temperature+80 ℃) to (Ar ₃Transition temperature-40 ℃) finishes hot rolling in the temperature range, then batch, this steel is annealed after cold rolling, mainly contain Ti so that produce inside 600-700 ℃ temperature range ₄C ₂S ₂Or Ti ₄C ₂S ₂And TiS, being of a size of 1000-10000 , quantity is 1 * 10 ⁴-5 * 10 ⁵Individual/mm ²Precipitate.

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