JP2003277902A - Method for producing high strength galvanized steel sheet excellent in plated adhesion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a high strength galvanized steel sheet excellent in the plated adhesion and the balance between the strength and the elongation even in the case of containing large amounts of Si and Mn. <P>SOLUTION: To the steel sheet having composition containing 0.05-0.25 mass% C, 0.50-2.0 mass% Si, 1.0-3.5 mass% Mn, 0.01-1.0 mass% Al and a ratio of Mn to Si is ≥0.5, a primary heating treatment is applied so that a ratio of an infrared absorbing spectrum intensity I(SiO<SB>2</SB>) of amorphous SiO<SB>2</SB>and an infrared absorbing spectrum intensity I((Fe,Mn)<SB>2</SB>)SiO<SB>4</SB>) of (Fe,Mn)<SB>2</SB>SiO<SB>4</SB>generated on the steel sheet surface after heating measured with a reflection type IR spectrum measuring instrument in an atmosphere at dew point -50°C to +40°C becomes ≤0.3, and successively, a secondary heating treatment is applied in the temperature range of not lower than Ac<SB>1</SB>transformation point and not higher than Ac<SB>3</SB>transformation point after pickling so that the reduced amount with the pickling becomes 0.05-5 g/m<SP>2</SP>Fe conversion and thereafter, the galvanizing treatment is applied and if necessary, an alloying treatment is applied. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to an excellent plating adhesion
Good and can withstand complicated press forming
Strength galvanized steel with excellent strength-ductility balance
The present invention relates to a method for manufacturing a plate. [0002] 2. Description of the Related Art In recent years, automobiles have been
The weight of the vehicle has been reduced for the purpose of improving the fuel ratio.
From the viewpoint of occupant protection, vehicle body safety is required.
You. Due to such demands, hot rolled steel sheets and
High strength and cold rolled steel sheets have been developed. Only
For high-strength steel sheets, to improve press formability
In addition, improvement of the strength-ductility balance is strongly desired. Sa
Furthermore, from the viewpoint of the rust prevention of the car body, it has excellent corrosion resistance.
It is also desired that the steel plate be a steel plate. [0003] In the case of increasing the strength of hot-rolled steel sheets and cold-rolled steel sheets,
In general, it is common to add solid solution strengthening elements such as Si and Mn.
You. On the other hand, these elements (Si, Mn, etc.)
It oxidizes during annealing, and the surface of steel, Mn, etc.
Concentrate (external oxide due to the so-called selective oxidation phenomenon) precipitates
It is known to issue. For this reason, Si, Mn, etc.
Hot-dip galvanizing after annealing
In the process, the wettability between the molten zinc and the steel sheet surface decreases,
There is a problem that the adhesiveness is deteriorated. [0004] SUMMARY OF THE INVENTION The workability of high strength steel sheets
Regarding the method of improving, for example, JP-A-5-179356
According to the report and JP-A-5-51647, rapid cooling during hot rolling
Composition before the hot dip galvanizing line (CGL)
Weaving and then two-phase annealing and plating by CGL
The art is disclosed. However, with these technologies, Si
If even a small amount is added, the plating adhesion deteriorates,
There is a problem that plating peeling is likely to occur. for that reason
Previously, molten zinc was used as a base material for steel sheets with high Si and Mn contents.
It is a fact that good plating adhesion is obtained with plated steel sheets
Was considered impossible. [0005] An object of the present invention is to provide a semiconductor device including a large amount of Si and Mn.
In addition to excellent plating adhesion, strength-ductile balun
Of high-strength (alloyed) hot-dip galvanized steel sheet
The idea is to propose a method. In addition, the molten zinc
The material of the steel sheet can be any type of hot rolled steel sheet or cold rolled steel sheet.
No. [0006] Means for Solving the Problems The present inventors have increased the content of Si and Mn.
Amount of steel sheet contained while maintaining the mechanical properties
Conditions for improving the adhesion between steel sheet and molten zinc
We studied diligently. As a result, the Mn / Si content in steel exceeds a certain level
Steel composition with a composition that reduces external oxidation of easily oxidizable elements.
And in a high oxygen potential atmosphere that promotes internal oxidation.
After the next heat treatment, pickling the steel sheet surface,
Hot-dip galvanizing greatly improves plating adhesion
I found that it can be improved. That is, in the present invention, C: 0.05 to 0.25 mass
%, Si: 0.50 to 2.0 mass%, Mn: 1.0 to 3.5 mass%, Al:
Composition containing 0.01-1.0 mass% and Mn / Si is 0.5 or more
The steel sheet at the heating temperature (Ac_ThreeTransformation point -80 ° C)_TwoDark
Temperature in an atmosphere with a dew point of -50 ° C to + 40 ° C.
Amorphous SiO generated on the surface of steel sheet after heating_TwoInfrared absorption
Spectrum strength I (SiO_Two) And (Fe, Mn)_TwoSiO_FourInfrared absorption
Spectrum strength I ((Fe, Mn)_TwoSiO_Four)) Is 0.3 or less
Primary heat treatment, and then pickling loss is reduced to Fe
0.05-5g / m^TwoAfter pickling so that₁transformation
Above the point Ac_ThreePerform secondary heat treatment in the temperature range below the transformation point.
And then hot-dip galvanizing.
Manufacturing method of high strength hot-dip galvanized steel sheet with excellent adhesion
Is the law. [0008] In the present invention, the steel sheet is a steel sheet.
In addition, Cr: 1.0 mass% or less, Mo: 1.0 mass% or less,
B: 0.003 mass% or less, Ti: 0.1 mass% or less, Nb: 0.1 mas
s% or less, V: 0.1 mass% or less, Cu: 1.0 mass% or less, Ni:
Contains at least one selected from 1.0 mass% or less
Is preferred. In the present invention, the primary processing
During heat treatment, increase the oxidation weight of the steel sheet by 0.05 g / m^Two
It is preferable to have the features described above. further,
In the present invention, after the hot-dip galvanizing is performed,
Further, it is preferable to perform an alloying treatment. [0009] BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the component composition in the present invention will be described.
The reason for the limitation will be described. C: 0.05 to 0.25 mass% C is an essential element for increasing the strength of the steel sheet. Ma
In addition, it is impossible to secure the desired tissue and obtain a good material.
It is a missing component. However, if C is less than 0.05 mass%, it is desirable.
Strength cannot be obtained, and weldability of 0.25 mass% or more
In order to cause deterioration, the content is limited to 0.05 to 0.25 mass%. Preferred
More specifically, it is 0.07 to 0.18 mass%. Mn: 1.0 to 3.5 mass% Mn enhances strength by solid solution strengthening, improves hardenability and
Indispensable components to secure the desired tissue and obtain good materials
Minutes. However, if the content is less than 1.0 mass%
Insufficient effect described above, and welding at over 3.5 mass%
Deterioration of performance. Therefore, Mn is in the range of 1.0 to 3.5 mass%.
Add in box. Preferably, it is 1.5 to 3.0 mass%. Si: 0.50 to 2.0 mass% Si has the effect of increasing strength without impairing ductility by solid solution strengthening.
Element that secures the desired structure
It is an indispensable element for obtaining good materials. This addition amount
However, if it is less than 0.5 mass%, the above effect is insufficient. And
However, when added over 2.0 mass%, plating adhesion
It is difficult to ensure the performance. So, 0.50 ~ 2.0mas
Add in the range of s%. Preferably at 0.6-1.6 mass%
is there. Al: 0.01 to 1.0 mass% Al enhances the strength and secures the desired structure to obtain a good material.
Is an effective element for Al is easily oxidizable.
Is an element that does not deteriorate plating adhesion as much as Si
You. Therefore, the amount of Si can be reduced by adding Al,
Improved plating adhesion compared to steel with Si alone added
Can be good. To get the desired effect,
0.01 mass% is required, but plating exceeds 1.0 mass%
It becomes difficult to secure adhesion. For this reason, Al is 0.01 ~ 1.0m
Restrict to ass% range. Preferably, 0.02 to 0.5 mass%
It is. Mn / Si in steel ≧ 0.5 To improve plating adhesion, it is necessary to increase Mn / Si
It is advantageous. The reason for this is that it occurs during annealing immediately before plating.
Surface condensate is a Si-based acid with poor wettability with molten zinc
(SiO)_Two) Indicates that Si and Mn have good wettability with molten zinc.
Complex oxide ((Fe, Mn)_TwoSiO_Four). Sa
In addition, the steel sheet is passed through the continuous hot-dip galvanizing equipment (CGL).
Before heating, first heat and cool, then pickle the steel plate surface
Higher Mn / Si is more resistant to acid pickling
SiO_TwoGeneration is small and pickling is good (Fe, Mn)_TwoSi
O_FourThe generation of acid is increased, so that the pickling property is improved. Again
Sometimes, the pickling property is improved,
Because the concentration of Si on the surface of the annealed plate is reduced and alloying is promoted,
Productivity also increases. To obtain this effect, Mn / Si ≧ 2
It is preferable to use a primary heating atmosphere described later.
To control the_TwoSuppress the amount of formation, (Fe, Mn)_TwoSiO_FourWith
By adjusting the formation ratio, 2> Mn / Si ≧ 0.5 region
However, it is possible to ensure stable plating adhesion.
You. However, when Mn / Si is higher than 7, the content of Si is relatively high.
It is difficult to obtain the desired microstructure
Therefore, it is preferable that Mn / Si ≦ 7. In the present invention, in addition to the above components, various
The following, if necessary, to improve the mechanical properties of
One or more elements can be added. Cr: 1.0 mass% or less Cr is added to improve hardenability and obtain a desired structure.
Can be Preferably, it is at least 0.05 mass%.
However, if added over 1.0 mass%, the plating adhesion
to degrade. Mo: 1.0 mass% or less Mo, like Cr, improves hardenability and obtains the desired structure
Is added as needed. Preferably, 0.05 mass%
However, if it exceeds 1.0 mass%, the cost will increase.
You. B: B: 0.003 mass% or less B is necessary for improving hardenability and obtaining a desired structure
Add according to. However, if it exceeds 0.003mass%
Adhesion deteriorates. Ti: 0.1 mass% or less, Nb: 0.1 mass% or less,
V: 0.1 mass% or less Ti, Nb and V form carbonitrides and precipitate
Is added as needed to reinforce. Each element,
Each is preferably added in an amount of 0.01 mass% or more.
%, The strength becomes excessively high and ductility deteriorates. Cu: 1.0 mass% or less, Ni: 1.0 mass% or less Cu and Ni are both elements that segregate in austenite.
And effective for obtaining a desired tissue and strength. So
In addition, these components act to improve plating adhesion
May be added for this purpose if necessary
Can be. These components improve plating adhesion
The reason is not clear, but to get this effect,
In each case, it is preferable to add at least 0.01 mass%. However, 1.
Even if it exceeds 0 mass%, the effect is saturated and cost
There is no merit. In addition, other than the components described above
The balance is preferably Fe and inevitable impurities
No. Method for producing hot-dip galvanized steel sheet according to the present invention
The method uses a hot-rolled steel sheet or a cold-rolled steel sheet
Heat treatment, pickling treatment, secondary heat treatment and plating treatment
And additional alloying process if necessary
Is done. The reasons for limiting the conditions of each process are described below.
I will tell. (1) Primary heat treatment The primary heat treatment is performed by annealing immediately before hot-dip galvanizing (the present invention).
(Equivalent to secondary heat treatment).
External oxides such as Si and Mn precipitate out and wettability with molten zinc
Important to prevent plating adhesion from deteriorating
It is a process. Uses continuous annealing furnace for primary heat treatment
It is preferable that the atmosphere control described later can be performed.
However, the present invention is not limited to this. Add Si and Mn in complex
Steel sheet is heated in a reducing atmosphere.
The resulting oxide is an amorphous SiO that is difficult to pickle._Twoand
Good pickling (Fe, Mn)_TwoSiO_FourIs considered to be the main
You. For this reason, in order to ensure adhesion with molten zinc,
Is the SiO2 on the steel sheet surface_TwoGeneration as much as possible
Need to be Specifically, SiO_TwoAnd (Fe, Mn)_TwoSiO_Four
Is measured by a reflection type infrared spectrometer.
Line absorption spectrum intensity I (SiO_Two) And (Fe, Mn)_TwoSiO_FourRed
External absorption spectrum intensity I ((Fe, Mn)_TwoSiO_Four))
R value R (= I (SiO_Two) / I ((Fe, Mn)_TwoSiO_Four)) ≦ 0.3 It is necessary to control so that R value is greater than 0.3
When it becomes amorphous SiO_TwoIs too large to produce poor pickling
And the plating adhesion deteriorates. If the R value is less than 0.3
If so, deterioration of plating adhesion can be suppressed. [0018] SiO_TwoIs based on the composition of the ingredients described above.
(Mn / Si) as well as annealing atmosphere (hydrogen concentration, dew point)
Depends heavily. When Mn / Si is high, the normal dew point
Also amorphous SiO_TwoTends to be suppressed, but Mn
If the / Si is low, the dew point is increased
Amorphous by heating in oxygen potential atmosphere
SiO_TwoCan be suppressed. Therefore, the atmosphere
To control the concentration of hydrogen in the air and the dew point within appropriate ranges
Thus, plating adhesion can be improved. In the actual operation, the control of the R value is performed by a reflection type control.
Infrared spectroscopy of each oxide on-line
Monitor the amount of production constantly and feed
To control the hydrogen concentration and dew point within appropriate ranges.
It is possible. Peak with reflection-type infrared spectrometer
When measuring the strength, use amorphous SiO_TwoIs the wave number 1230cm
^-1The infrared absorption spectrum observed for (Fe, Mn)_TwoSiO_Four
Is the wave number 1000cm^-1Use infrared absorption spectrum observed in
It is appropriate that the strength is strong and can be clearly identified. However
And the accuracy of the measuring instrument, the surface condition of the steel sheet,
Of the absorption spectrum due to complex oxidation of
Since the peak position may be shifted,
Standard SiO_TwoHas a wave number of 1200 to 1260cm^-1, (Fe, Mn)_TwoSiO_FourIs a wave
The number is 970-030cm^-1Search for peaks in the range
Good to do. If multiple peaks are found within the range
If the maximum absorption intensity is
Is determined. The method of reading the peak intensity is as shown in FIG.
Then, draw the baseline from both ends of the peak and
Absorbance value difference from to baseline (usually as%
Is given as the absorption spectrum intensity. FIG.
Typical measured by a reflection type infrared spectrum measuring device
IR spectrum and R value (= I (SiO_Two) / I ((Fe, Mn)_TwoSi
O_Four3) shows the measurement results. ☆ in the figure is SiO_TwoCause, ◇ mark
Is (Fe, Mn)_TwoSiO_FourFIG. Improves wettability with molten zinc and improves plating density
In order to improve adhesion, selective oxidation of easily oxidizable elements
In addition to controlling external oxides, it can also control internal oxidation.
is important. That is, Mn / Si is low and relatively contains Si
For steel sheets with a large volume, increase the dew point and
Internal oxidation in the surface layer of the base material
Oxidizing elements are fixed as internal oxides in the surface layer of the base material
This prevents re-surface enrichment during secondary heating immediately before plating.
It is preferable to control. For that, the mother at the time of primary heating
0.05g / m per surface^TwoAbove
It is necessary to If it is less than this, the oxidation increase is insufficient
Therefore, re-surface enrichment due to annealing immediately before plating cannot be suppressed.
No. There is no upper limit, but 1g / m^TwoIf it exceeds, oxidation
Unfortunately, the appearance after plating deteriorates, which is not preferable. Here, the base material surface region is defined from the surface of the base material.
It refers to a depth of up to 100 μm. Also, internal oxidation
The formation of oxides at the grain boundaries or within the grains of the base metal
A so-called external acid that forms an oxide on the surface of the base material
Distinction. And, the oxidation increase of the base material surface layer
Is determined by measuring the oxygen content in the surface layer of the base metal.
It is. In other words, the surface of the steel sheet after the primary heat treatment is degreased well.
The sample was analyzed for the total oxygen content in the steel,
100 μm each of the front and back surface layers of the steel plate were mechanically polished.
And analyze the total oxygen content in the steel, and from these analysis values,
Calculate the increment of oxide on the surface layer of the steel sheet and calculate the
Amount (g / m^Two). Ensuring an increased amount of oxidation in the surface layer region of the base material
As a method, in the hot rolling step of the base material (heated material)
Supplied from the oxide scale during cooling after high-temperature winding.
The base metal is internally oxidized by oxygen
The atmosphere is reducing for Fe,
Slightly high exposure that is oxidizing for easily oxidizable elements
Internal oxidation can be achieved by setting the point conditions.
Therefore, the component composition of the base material, the winding in the hot rolling process
Temperature, dew point of furnace atmosphere during primary heating, and base metal
The relationship with the oxidation increase in the surface layer was determined experimentally,
Predetermine the dew point range where the desired oxidation increase can be obtained.
It should be good. As described above, the R value, preferably the R value and
Good oxidation adhesion by ensuring proper plating adhesion
The dew point of the ambient gas in the primary heat treatment
It is necessary to control the hydrogen concentration. H in atmosphere gas_Two
The concentration is preferably 1 to 100%. H_TwoIs less than 1%
Insufficient surface consolidation could not improve plating adhesion
No. Further, the dew point is preferably in the range of −50 ° C. to + 40 ° C.
Below -50 ° C, H _TwoO is too small to supply
Insufficient selective oxidation of easily oxidizable elements
Selective oxidation during annealing increases. More than + 40 ℃
Then, the furnace body is damaged. Further, the primary heating temperature and the holding time are also heavy.
An important management item, the heating temperature is (Ac_Three(Transformation point -80 ℃)
The holding time is preferably 5 seconds or more. Heating temperature
Causes selective oxidation and internal oxidation to ensure plating adhesion
(Ac_Three(Transformation point -80 ° C) or higher.
In order to cause internal oxidation, heat at as high a temperature as possible.
This is preferable because the internal oxidation amount increases. In addition,
To control the R value, within the range satisfying the above conditions,
The primary heating temperature may be varied. (2) Pickling treatment Surface condensate generated in the primary heating process (oxides such as Si and Mn)
Hydrochloric acid or other acids (sulfuric acid, phosphoric acid,
Activate the surface by pickling with any type (such as nitric acid).
I do. The pickling weight loss at this time is 0.05 g / m^TwoIf less than, concentrate
Removal is insufficient. On the other hand, 5g / m^TwoExceeds the surface
Is rough and impairs the appearance after plating. Pickling conditions are particularly stipulated
No, but liquid temperature: 60 ° C ~ 90 ° C, pickling time: 1 ~ 20sec
preferable. (3) Secondary heat treatment Direct plating in continuous galvanizing line (CGL)
Before annealing (secondary heat treatment),₁Above the transformation point_ThreeStrange
Must be done below the attitude. Annealing temperature is Ac₁Below the transformation point
If the steel plate is washed with water after pickling and then dried,
Not enough to reduce Fe-based thin oxide film formed on
is there. Conversely, Ac_ThreeIf the temperature exceeds the transformation point, reappear immediately before plating
Intensification also occurs. The holding time is determined by reducing the surface oxide film.
5 seconds or less to balance
The upper time is preferably 120 seconds or less. Heating atmosphere is a return for iron
There is no problem if the atmosphere is original. (4) Hot-dip galvanizing Zinc in the plating bath is used to ensure the adhesion of the plating layer
It is preferable that Al contains 0.08 mass% or more. Only
However, if it exceeds 0.20 mass%, alloying becomes difficult.
The limit is preferably 0.20 mass%. The plating bath temperature is 440
Below ℃, the freezing point (420
(° C) may appear, and operation is stable
Lack of sex. On the other hand, when the temperature exceeds 480 ° C, cost
Take. For this reason, the plating bath temperature is preferably 440 to 480 ° C.
New (5) Alloying treatment The hot-dip galvanized steel sheet is then
Alloyed hot-dip galvanized steel (Galvannea
led Steel, hereafter abbreviated as GA)
You. When the alloying temperature is 450 ° C or less, a ζ phase is easily formed.
Not only may impair the slidability of the GA,
Since alloying takes a long time, productivity is reduced. Also, 60
If the temperature exceeds 0 ° C, the Γ phase is likely to be generated, and GA plating
There is a possibility that the adhesion may be reduced. Therefore, the alloying temperature
The temperature is preferably from 450 to 600 ° C. The alloying degree is 7 ~ 15%
Is suitable, and preferably 8 to 12%. 7
%, The appearance deteriorates due to uneven burning and the sliding property is low.
May fall. Conversely, if it exceeds 15%,
The adhesion deteriorates. [0029] The final structure of the steel sheet was tempered martensa.
To have a composite structure with aite and retained austenite
Is preferred. This is good if the steel sheet has a composite structure
This is for showing a good strength-ductility balance. Where tempering
Martensite is lath-like martensite before tempering.
Phase with a fine internal structure that inherits the morphology of
Softened by return and has sufficient plastic deformability
Therefore, it is an advantageous phase for improving the ductility of a high strength steel sheet. Most
The final structure contains at least 20vol% of tempered martensite
In this case, a marked improvement in ductility is observed.
Tensite should be contained at least 20vol%
No. In addition, the retained austenite is transformed during strain-induced transformation.
To produce martensite and locally applied processing
Has the effect of widely dispersing strain and improving the ductility of steel sheets
Phase. As final structure, retained austenite is 2vo
If the content is more than 1%, a remarkable improvement in ductility is observed.
The residual austenite should contain at least 2 vol%
Is preferred. The tempered martensite and residual
Ferrite and low-temperature transformation
Phase. Here, the low-temperature transformation phase refers to martensite and
And / or bainite. In order to obtain the above-mentioned composite structure, it is necessary to first explain
After the primary heat treatment step in the manufacturing process, the cooling rate is 10 ° C
/ Sec or more, and after secondary heat treatment, 5
Cool at a cooling rate of 5 ° C / sec or more to a temperature of 00 ° C or less.
Preferably. The cooling rate after the primary heat treatment
℃ / sec or more, the lath
Site can be generated. In addition, lath-shaped circle
The primary heating temperature for producing tensite is described above.
As in (Ac_Three(Transformation point -80 ° C) or higher. (Ac_Three
(Transformation point -80 ° C)
The amount of tenite is reduced and the amount of lath martensite is confirmed.
I can't keep it. Lath martensite at 20vol% or more
And the finally obtained tempered martensite is less than 20 vol%
To make it higher, the primary heating temperature should be (Ac_Three(Transformation point -50 ℃)
It is preferred to be above. Also, make sure that
Produce tenite and secure lath martensite
Therefore, it is preferable that the holding time is 5 seconds or more.
No. The secondary heat treatment is performed in accordance with the above-described Ac.₁transformation
Above the point Ac_ThreeBy performing in the temperature range below the transformation point,
With martensite becomes tempered martensite
Ultimately forms retained austenite and low-temperature transformation phases
Austenite required for the formation of Secondary heat treatment temperature
The degree is Ac₁If the temperature is below the transformation point, austenite is formed.
To obtain retained austenite and low-temperature transformation phase after cooling.
I can't do that. Conversely, Ac_ThreeIf the transformation point is exceeded,
Induces the re-austenite formation of tensite. Secondary heat treatment
The retention time in tempered martensite and
From the viewpoint of the formation of stainite, 5sec or more and 120sec or less
preferable. The heating atmosphere is a reducing atmosphere for Fe.
There is no problem if. Furthermore, cooling after the secondary heat treatment
Austenite formed in the ferrite and pearlite
To prevent transformation to
In addition, a low-temperature transformation phase is formed to secure
500 ° C at 5 ° C / sec or more to contribute to high strength
It is better to cool to below. [0032] EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples.
I do. A steel slab having the composition shown in Table 1 (300 mm
), Heated to 1250 ° C, hot rolled, wound at 560 ° C,
Pickling, and some, after that, cold rolling,
The material was used for hot-dip galvanizing. Plating hot rolled material
In this case, use a hot rolled material up to 1.4 mm
If the material is hot rolled to 2.8mm
A cold-rolled material was used. Table 2 and Table 2
And under the conditions shown in Table 3, primary heating, pickling, secondary heating and
Perform hot-dip galvanizing and, if necessary, alloying treatment
Was given. When performing primary heating, the steel plate surface after heating,
Using a reflection type IR spectrum measuring device, the wave number is 1200 to
1260cm^-1Range of 970 ~ 1030cm^-1Peak intensity in the range
Measure the R value (= I_Two) / I ((Fe, Mn)_TwoSiO_Four)) Is always 0.
Feedback control of hydrogen concentration and dew point to 3 or less
did. In addition, surface oxidation of steel sheets that have been subjected to primary heat treatment
The amount was measured. Then, it was pickled with 5 mass% HCl at 60 ° C.
After that, secondary heat treatment and hot dip galvanizing are performed by CGL.
Further, an alloying treatment was performed as necessary. Plating weight
Is 40g / m^Two(One side). In addition, the alloying treatment conditions are 5
00 ° C. × 20 sec. [0033] [Table 1] [0034] [Table 2][0035] [Table 3] The plating adhesion of the obtained steel sheet was
A cellophane tape on the plating surface and
After bending within 90 ° and bending back, peel off the tape and
The amount of zinc adhering to the tape was measured by X-ray fluorescence.
Judged against the criteria, ranks 1 and 2 are good, 3
The above were evaluated as defective. Also, by visual judgment
If there is no plating or uneven plating,
Poor in appearance (x), good appearance when not seen at all (○)
Was evaluated. Investigation of mechanical properties taken in the direction perpendicular to the rolling
The tensile strength (TS) and elongation
And (El) were measured. The strength-ductility balance is
(TS × El), 20000 MPa ·% or more is good ((), 2
Less than 0000 MPa ·% was evaluated as poor (×). Table 3 shows the measurement results.
It is shown together. The materials used in the examples contain Si and Mn.
The strength level varies from the so-called 590MPa class to 980M
Includes those equivalent to Pa class. However, within the scope of the present invention
In each case, TS × El is 20,000MPa ·% or more, strong
Excellent degree-ductility balance. Also, those within the scope of the present invention
Are excellent in plating adhesion and plating appearance
You. [0037] [Table 4] [0038] As described above, according to the present invention,
High strength (combined) with excellent plating adhesion and strength-ductility balance
It is possible to manufacture hot-dip galvanized steel sheets.
You. By adopting this steel plate, the light weight of the car body
And lower fuel consumption, and ultimately to improve the global environment
Also give a large page.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing how to read the absorption peak intensity of an infrared absorption spectrum. FIG. 2 is a diagram showing a typical infrared absorption spectrum.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 2/28 C23C 2/28 8/14 8/14 F term (Reference) 4K027 AA05 AA23 AB05 AB06 AB44 AC12 AC73 AE33 4K037 EA01 EA02 EA05 EA06 EA11 EA13 EA15 EA16 EA17 EA19 EA20 EA27 EA28 EA31 EA32 EB07 EB09 EB12 FH01 GA05

Claims (1)

[Claims 1] C: 0.05 to 0.25 mass%, Si: 0.50 to 2.0 m
A steel sheet containing ass%, Mn: 1.0 to 3.5 mass%, Al: 0.01 to 1.0 mass%, and having Mn / Si of 0.5 or more was heated to a heating temperature (Ac ₃ transformation point −80 ° C.) or higher and H _2. concentration 1~100vol%, in an atmosphere of a dew point of -50 ℃ ~ + 40 ℃, infrared absorption spectrum intensity of the generated surface of the steel sheet after heating amorphous SiO ₂ I (Si
O ₂ ) and (Fe, Mn) ₂ SiO ₄ infrared absorption spectrum intensity I
((Fe, Mn) ₂ SiO ₄ )) and a primary heat treatment is performed so that the ratio is 0.3 or less, then, the pickling loss is 0.05 to 5 g in terms of Fe.
/ M ² , followed by a secondary heat treatment in a temperature range from the Ac ₁ transformation point to the Ac ₃ transformation point, and then hot-dip galvanizing. Manufacturing method of excellent high strength galvanized steel sheet. 2. The steel sheet according to claim 1, further comprising:
r: 1.0 mass% or less, Mo: 1.0 mass% or less, B: 0.003 mass
%, Ti: 0.1 mass% or less, Nb: 0.1 mass% or less, V:
The high-strength hot-dip zinc excellent in plating adhesion according to claim 1, comprising one or more selected from 0.1 mass% or less, Cu: 1.0 mass% or less, and Ni: 1.0 mass% or less. Manufacturing method of plated steel sheet. 3. The high-strength molten steel having excellent plating adhesion according to claim 1, wherein the steel sheet has an oxidation increase of 0.05 g / m ² or more per side during the primary heat treatment. Manufacturing method of galvanized steel sheet. 4. A high-strength galvanized steel sheet having excellent plating adhesion according to claim 1, further comprising an alloying treatment after the galvanizing. Manufacturing method.