JPH0673495A - Steel sheet for porcelain enameling excellent in deep drawability, adhesion and weldability - Google Patents

Abstract

PURPOSE:To obtain a steel sheet for porcelain enameling excellent in press formability, adhesion of porcelain enameling and weldability by specifying a compsn. constituted of C, Mn, S, Al, N, Cu, O, Nb, B and iron. CONSTITUTION:This steel sheet is the one having a compsn. contg., by weight, <=0.0050% C, 0.20 to 1.0% Mn, >0.020 to 0.100% S, <=0.010% Al, <=0.0050% N, 0.010 to 0.100% Cu, >0.020 to 0.100% O, >=0.10% Nb and >0.0030 to 0.0200% B as well as satisfying Mn/S>=10, Nb/C>=7 and B/N>=1, and the balance iron with inevitable impurities, and in which 0.001 to 0.050% Si is substituted for the same quantity of the balance iron at need. In this way, the steel sheet for porcelain enameling satisfying the minimum characteristics as those of the steel sheet for porcelain enameling such as fishscale resistance and firing strain resistance and excellent in deep drawabilty, adhesion and weldability can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention satisfies the minimum characteristics of a steel sheet for enamel, such as knurling resistance and firing strain,
In addition, the present invention relates to a steel sheet for enamel which is excellent in press formability, enamel adhesion and weldability.

[0002]

2. Description of the Related Art Enamel is a nonflammable material made by baking glass on the surface of a steel sheet and has various characteristics such as heat resistance, weather resistance, chemical resistance, water resistance and stain resistance. There is a feature that The base materials for enamels involved in this are mainly cold-rolled steel sheets, and the required properties include firing strain resistance, slab resistance, adhesion, bubble resistance, and black spot resistance. In addition, it must have press formability and weldability. Conventionally, rimmed steel has been mainly used, but with the labor saving and cost reduction of steel makers, continuous cast steel has come to be used.

Among these continuously cast steels, steel sheets for enamel having excellent weldability are disclosed in JP-A-59-229436, JP-A-2-235550, and JP-A-2-236254, which are high oxygen steels. Is disclosed. However, the r value of each of the steel sheets is 1.6 or less, and the press formability is poor. On the other hand, a typical example of a continuous cast enamel steel plate having excellent press formability is a Ti-added Al-killed steel as disclosed in Japanese Patent Publication No. 4-16539. However, this type of steel plate has a concave welded part or a blow hole when joint welding is performed by plasma welding or TIG welding, resulting in streak defects and bubble defects on the surface after enamel processing. I was doing it.

Conventionally, as a means for preventing this defect,
Enamel makers used slow welding speed or set welding current to a relatively high value, but this is not always an appropriate method, and it reduces productivity and causes defects with a considerable defect rate. The current situation is that products are being generated. Further, compared with rimmed steel, continuous cast steel tends to have significantly deteriorated adhesion when subjected to special enamel processing without pretreatment (sulfuric acid pickling and Ni treatment).

Therefore, a enamel maker has long sought a steel plate having excellent press formability such as Ti-added Al-killed steel and having weldability and adhesion such as conventionally used rimmed steel.

[0006]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a enamel steel sheet having press formability equal to or higher than that of a Ti-added Al killed steel, and having extremely excellent adhesion and weldability. To do.

[0007]

Means for Solving the Problems That is, according to the present invention, in terms of weight ratio, C: 0.0050% or less, Mn: 0.20 to 1.0%, S: more than 0.020% to 0.100% Al: 0.010% or less, N: 0.0050% The following are included: Cu: 0.010 to 0.100%, O: more than 0.020% to 0.100%, Nb: 0.10% or less, B: more than 0.0030% to 0.0200%, and Mn / S ≧ 10, Nb / C ≧ 7, B / N ≧ 1 and the balance is iron and unavoidable impurities. It is a steel sheet for enamel and has excellent deep drawability, adhesiveness and weldability, and if necessary, Se: 0.001 to 0.050% is the balance. It is a steel plate for enamel which is replaced with the same amount of iron and the balance consists of iron and unavoidable impurities and has excellent drawability, adhesion and weldability.

[0008]

That is, the present invention improves the press formability by adding Nb and B to fix the solid solution C and N as NbC and BN, which cause deterioration of the material, and further improve the press formability. It is a steel sheet for enamel whose adhesion and weldability are remarkably improved by increasing the amount.

Next, the reasons for limiting the components of the steel plate for enamel of the present invention will be explained. C: 0.0050% or less C is an interstitial solid solution element, and the content of more than 0.0050% significantly deteriorates the press formability, so it is necessary to reduce it as much as possible. Therefore, the upper limit of the amount of C in the present invention is set to 0.0050%.

Mn: 0.20 to 1.0% Mn fixes S that causes red hot embrittlement as MnS, and forms MnO in the component system in which a large amount of oxygen is added as in the present invention. It is an effective element in the present invention because it can trap hydrogen, which causes a jump defect. In order to bring out these effects, a content of at least 0.20% or more is necessary. However, the addition of more than 1.0% increases the cost of molten steel, so the upper limit was made 1.0%.

S: more than 0.020% to 0.100% By setting the content of S to more than 0.020%, it becomes possible to improve adhesion and weldability. On the other hand, when the content is 0.100% or more, not only the pickling rate at the time of pretreatment of enamel is significantly increased, but also generation of smut which causes bubbles and black spot defects is promoted. For material, Mn /
If S <10, cracks will occur during hot rolling,
In the present invention, 0.02% to 0.100% and Mn / S ≧ 10.

Al: 0.010% or less Al is usually used as a deoxidizing agent in the steelmaking stage, but in the present invention, oxygen is controlled within a specific range for the purpose of improving the rust resistance. . Therefore, Al is sufficient as long as it is necessary. But 0.010%
Oxygen content, which is an important element in the present invention, exceeds the Al content.
_{In the} present invention, 0.010% because it is removed as ₂ O _3.
It is limited to the following range.

O: more than 0.020% to 0.100% O is an element mainly improving wing resistance, and in the present invention, it is an element significantly improving weldability, so its content is very heavy. . However, if the content is 0.020% or less, the weldability cannot be significantly improved. On the other hand, if the content exceeds 0.100%, there are many blowholes in the continuous cast slab, and the cost of slab surface maintenance is high, and the product yield deteriorates. Therefore, the content range is 0.020%.
It was over ~ 0.100%.

N: 0.0050% or less N is an interstitial solid solution element like C, and if it exceeds 0.0050%, there is a risk of material deterioration. In the present invention, B is added
0.0050 although BN is formed and its adverse effects are suppressed
The content of more than 100% inevitably increases the amount of B added and must be avoided. Therefore, in the present invention, the upper limit is set to 0.0050%.

B: more than 0.0030% to 0.0200% In the present invention, B is added to fix the solid solution N, which is the main cause of the material, as BN. In addition, B is an effective element because it forms a B-based oxide to ensure dent resistance and prevents aging deterioration due to solid solution N. At least 0 to bring out the effect.
It is necessary to add B / N ≧ 1 in excess of 0030%. However, since the content of more than 0.0200% is likely to cause cracks during hot rolling, in the present invention, the amount of B is more than 0.0030% to 0.
It was 0200% and B / N ≧ 1.

Cu: 0.010 to 0.100% Cu is an element added for the purpose of controlling the pickling rate at the pretreatment of enamel, and a content of 0.010 or more is preferable to bring out these effects. However,
Addition of more than 0.100% makes it difficult for the steel plate surface to be pickled during enameling pretreatment, and fine irregularities effective for adhesion will not be formed on the steel plate surface, so the addition amount is 0.010 to 0.
It was 100%.

Nb: 0.10% or less Nb is an element effective in forming NbC in the hot rolling stage and reducing the amount of solute C to improve the formation of (111) texture during annealing after cold rolling. , At least Nb / C ≧ 7 is required. However, if the content exceeds 0.10%, the effect is saturated and the cost increases, so the range was made 0.10% or less and Nb / C ≧ 7.

Se: 0.001 to 0.050% Se similarly has the effect of reducing the viscosity of the liquid phase during welding and improving the shape of the welded portion, so S can be added if necessary. In addition, since Se waits for the effect of improving adhesion, at least in order to bring out the effect.
0.001% or more is required. However, addition of more than 0.050% causes preferential intergranular corrosion during enamel pretreatment and causes enamel surface defects such as black spots and bubbles, so it is necessary to add Se in an amount of 0.001 to 0.050%. is there.

In addition, although it is necessary to reduce unavoidable impurities as much as possible, the present invention does not limit the impurities.
Further, although the manufacturing method is not particularly limited in the present invention, the means effective for bringing out the effect of the present invention will be briefly described below. The hot rolling coiling temperature is preferably set to a temperature of 500 ° C. or higher in order to precipitate NbC at the stage of hot rolling mother plate and to improve press formability after cold rolling annealing. Recrystallization annealing can be applied to both the box annealing method and the continuous annealing method, but the annealing temperature range is from recrystallization temperature to 9
A temperature of 00 ° C is desirable. That is, at temperatures below the recrystallization temperature, the rolling structure remains and press cracking is likely to occur, while at temperatures above 900 ° C., the (111) texture becomes random and the press formability deteriorates significantly.

[0020]

[Example] A continuously cast slab having a chemical composition as shown in Table 1 was inserted into a heating furnace at 1200 ° C for 3 hours, and after rough rolling, a finishing rolling machine was performed so that the finishing temperature was 880 ° C and the plate thickness was 3.5 mm. Hot-rolled and coiled at temperatures in the range of 550-700 ° C. After pickling, cold rolling is performed to make a cold rolled sheet with a thickness of 0.7 mm
Short-time annealing was carried out at the following temperatures for maintaining the soaking temperature within 15 seconds. After temper rolling with a reduction rate of 0.5%, it is processed into JIS No. 5 tensile test pieces and 0 °, 45 °, 90 ° with respect to the rolling direction.
The mechanical properties in the ° direction were investigated. The results are shown as an average value in three directions. Further, the weldability is welding current 130A, speed
TIG welding was performed at 50 cm / min, and the welding distance from the start of welding to the occurrence of hole formation was evaluated. The results are shown in Table 2.

On the other hand, these steel plates were subjected to the enamel once and the enamel twice as shown in Table 3, and the various enamel properties shown below were investigated. The enamel adhesion was investigated according to the method of ASTM-C313-59, and the enamel resistance was tested twice by applying the enamel processed sample to a 160 ° C thermostat for 16 hours. It is the result of visual observation.

As a result, the steel sheet satisfying the chemical composition of the present invention had good press formability, enamel adhesion and weldability, and the finished shape was smooth. On the other hand, the steel sheets outside the present invention had problems in adhesion and weldability.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

The steel sheet produced according to the present invention has good deep drawability, adhesion and weldability. By using this steel sheet, it is not necessary to change the welding conditions at the enamel maker on a lot-by-lot basis. Not only disappeared,
It is also possible to further improve productivity.

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[Procedure amendment]

[Submission date] August 28, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

[0025]

[Table 3]

Claims (2)

[Claims] 1. By weight ratio, C: 0.0050% or less, Mn: 0.20 to 1.0%, S: 0.020% to 0.100% Al: 0.010% or less, N: 0.0050% or less, Cu: 0.010 to 0.100%, O: more than 0.020% to 0.100%, Nb: 0.10% or less, B: more than 0.0030% to 0.0200%, and satisfy Mn / S ≧ 10, Nb / C ≧ 7, B / N ≧ 1 and the balance Steel plate for enamel, which consists of iron and unavoidable impurities and has excellent deep drawability, adhesion and weldability. 2. A steel sheet for enameling having excellent deep drawability, adhesion and weldability according to claim 1, wherein Se: 0.001 to 0.050% by weight is replaced with the same amount of the balance iron.