JPS59182923A - Manufacture of ti-added cold rolled steel sheet for enameling with superior deep drawability - Google Patents

Abstract

PURPOSE:To manufacture economically the titled steel sheet with superior press formability and fish scale resistance by continuously casting a molten dead soft steel contg. specified amounts of Ti, N and S, hot-rolling and cold-rolling the cast steel, and subjecting the cold rolled steel sheet to recrystallization annealing after carrying out Ni plating as required. CONSTITUTION:A molten steel contg. <=0.008wt% C and Ti, N and S each by an amount satisfying equations I , II or further contg. 0.01-0.10% Cu is continuously cast. The cast steel is hot-rolled and cold-rolled, and the cold-rolled steel sheet is subjected to recrystallization annealing at the recrystallization temp. -1,000 deg.C after plating the surfaces of the sheet with Ni by 0.1-2.0g/m<2> as required.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a continuous casting cold rolled steel sheet having excellent deep drawing workability and rolling properties.

Conventional high-grade steel sheets for rolling are made of capped steel, decarburized by cold rolling and then decarburized by open annealing.
It was manufactured by reducing the amount to less than Oppm. The reason for using capped steel is that the oxygen in the steel is high (,200
ppm or more) is indispensable to prevent scattering after firing. Scatter is a phenomenon in which hydrogen stored in the steel plate during firing of the enamel aggregates at the interface between the steel plate and the enamel during cooling after firing, destroying the enamel layer. Further, the reason for adopting decarburization annealing by open annealing is to ensure excellent formability and enameling properties.

In the above-mentioned general conventional manufacturing method for steel plates for rolling, deep drawability is often required in addition to rolling properties, so rimmed steel is used and then decarburized and annealed. Of course, since rimmed steel cannot be ingot-formed by continuous casting, open annealing is essential, which increases manufacturing costs. In addition, due to the inclusion defects and material non-uniformity due to segregation peculiar to agglomerated materials, when it is made into a product steel strip, it can be said that it is fate that lumps are likely to occur in the rim layer and near the boundary between the rim layer and the core layer. There were drawbacks.

The present invention overcomes the above-mentioned drawbacks of the conventional steel plate manufacturing technology for enameling, and economically produces a steel plate for enameling that has excellent press formability, resistance to tipping, and excellent adhesion to enamel from continuous cast steel. (3) The object of the present invention can be achieved by providing the method described in the claims.

The present inventors have found that in order to improve the slippage resistance of a steel plate for crawlers, there must be a large amount of TiC precipitates, but as TiC increases, the material quality deteriorates.
Not only is it highly effective in preventing the occurrence of TIN buttocks, but
It was also found that material deterioration was small.

Therefore, the present invention provides a raw material and a processing method in which the minimum content of TI is limited as a method for manufacturing a steel plate for use in soldering. That is, in the present invention, (a) In weight%, Cr o, oθ% or less, T1 contains an amount expressed by the following formula (1), x, 30r (N (ppm)) + (C (ppm)) ) 〉／
/7.7-...Steel with C and N content adjusted as shown on the right that satisfies the conditions of (z) and formula (2), or steel with the above-mentioned composition and C
u: o, θ/~('I) 0.70% added is melted, (middle) the above melted steel is continuously cast to make a continuous cast slab, (c)
After that, hot rolling and cold rolling are performed.
．． /~s, o9/m2 Ni plating, then at a temperature above the recrystallization temperature and below 1ooor:
This is a method for producing a steel plate for enameling, which has excellent press formability, chipping resistance, and wax adhesion, and is characterized by performing recrystallization annealing.

Next, the reason why the present invention is limited as described above will be explained in detail.

[B] Regarding the composition of molten steel: C: C needs to be an ultra-low carbon steel with o, oog% or less. The upper limit of the amount of C is determined from the viewpoint of enamel properties and material quality. That is, when the C content is more than 0.0θr%, the α-
The γ transformation point decreases, and sagging occurs during firing.
Scattering easily occurs, the amount of TiC precipitates increases, and mechanical properties such as r value and elongation properties deteriorate. For the above reasons, the amount of C needs to be 0.00 g% or less.

Ti: Tt is determined from two aspects: (1) improvement in chipping resistance and (2) improvement in material quality, and is a particularly important element for the present invention.

All Ti in steel combines with N, S, and C to form TiNT
Ti 82. After removing TiC nitrides, sulfides, and carbides, the residue becomes solid solution Ti. The order of formation of these Ti precipitates is that TiNL is first formed at a high temperature of 73,000 or higher.
Ti82 is formed, the remaining 'ri combines with C to form a TiC precipitate, and the remaining Ti remains as solid solution Ti. T
If the amount of Ti is small and the total amount of C in the molten steel is not fixed as TiC precipitates and solid solution C remains, the r value will deteriorate, so the lower limit of the amount of Ti is TiN, Ti82. It is necessary to increase the amount of Ti that has become Tic. That is, the total amount of T1 must be added so as to satisfy equation (1).

Control of C and N: Conventionally, it was thought that in order to prevent the occurrence of lumpiness in T1-added ultra-low carbon grade steel, it was necessary to precipitate a large amount of fine TIC precipitates, which are hydrogen adsorption sources. Therefore, conventionally, in order to increase the amount of TIC precipitates, a melting method has been adopted in which S and N are kept as low as possible and the amount of C is increased to a certain extent or more. Furthermore, in order to form fine TIC precipitates, it was necessary to increase the slab heating temperature (hereinafter abbreviated as SR, T). For this reason, ■ it is necessary to increase the amount of C, resulting in deterioration of the material.

■ It is necessary to increase the SRT, which consumes a lot of energy, is not economical, and also deteriorates the material.

There was a drawback. The present invention is based on the fact that, as a result of repeated research to eliminate these drawbacks, it has been newly discovered that TiN precipitates have a greater hydrogen storage capacity than TIC.

Figure 7 shows C: 10~gOppm, N: 10~
AOppm.

Sl: θ, 00/~0. OJ%, Mn: O
, θri~0.09%.

P! 0.010~0.0/! r%, S:
0.00k ~ 0.0/co%.

(7) Red: θ, O-o-o, θAθ%, 0: o, θθ/
The amount of Tl in ultra-low carbon steel of θ ~ 0.003% is as follows (1)
Ultra-low carbon-TI added steel that satisfies the formula,
Hot rolled and cold rolled in the usual way, 110 CX11
．． It is a graph showing the relationship between the amount of C and N and the chipping resistance when continuous annealing is performed for seconds. The evaluation of chipping resistance was performed under the most severe enameling pretreatment conditions as shown in Table 1.
Evaluation was made based on the presence or absence of skipping when the test piece was wandered for 1 time.

Table 1 As a result, it was discovered that very good splintering resistance could be obtained by adjusting C and N within the range shown by the following formula (2).

2.30g (N (pPm)) + (C (ppm))〉//
7. (2) That is, TiN has T
It is expected to be 2.301 times more effective than iC. Since TiN precipitates are used to prevent the occurrence of skipping, ① Improvement in material quality due to extremely low carbon content: Since the amount of C can be reduced without the occurrence of skipping, the quality of the material is significantly improved.

■ Lower manufacturing costs and improved material quality due to lower SRT...
・Low SR because the influence of the distribution state of TIC precipitates is small
It is possible to use T, which is effective in saving energy in heating furnaces and improving material quality.

■ Stable jump resistance: TiN has more stable jump resistance than TIC.

For the first time, it has become possible to manufacture steel sheets for enameling with excellent waxing properties and material quality.

Addition of Cu t Cu improves enamel adhesion. If the content is less than 0.01%, there is no effect of improving adhesion, and if it exceeds 0.10%, the enamel adhesion will decrease. Therefore, Cu needs to be controlled to o, oi to θ, io%.

[Mouth] Molten steel having the above-mentioned composition is continuously cast to create a continuous cast slab.

Conventional steel sheets for enameling have a low c (co, oII%) because they have adopted a method of preventing the occurrence of porosity by occluding hydrogen in the oxide-based inclusions.
The temperature was high in oxygen (oxygen content approximately IItOppm).

Therefore, during casting, C90 in the molten steel reacts and CO gas is generated due to the rimming reaction, making it impossible to manufacture by continuous casting. In contrast, according to the method of the present invention, precipitates such as Tie and TiN are used as hydrogen storage sources, so the above-mentioned rimming reaction does not occur, making it possible to manufacture cis slabs by continuous casting. became.

[C] After that, hot rolling and cold rolling are performed sequentially.

[2] Next, the annealing conditions after cold rolling will be described.

Annealing must be performed at a temperature above the recrystallization temperature in order to obtain sufficient processing, and heating to the austenite region above 1000 C will deteriorate the T value, so a continuous annealing furnace must be used to reduce the temperature above the recrystallization temperature to below 10θoC. Hold for at least 73 seconds.

In addition, prior to the above continuous annealing, metal Ni was applied to the surface of the cold-rolled sheet in advance at a temperature of 0, /9/ML2~:1, θ9/T.
When plated to a thickness of n2, an enameled product with good adhesion can be obtained without any pre-enameling treatment such as pickling or N1 dipping. In this regard, conventional steel sheets for enameling require pretreatment such as degreasing, pickling, water washing, and N1 flushing before being enameled. In short, pickling is carried out to activate the steel plate surface and improve the adhesion between the wax layer and the steel plate, and Ni flashing is carried out to improve adhesion and prevent H2 from entering during enamel firing. be.

However, if N1 plating is applied to the surface of the steel plate in advance during smoking as in the present invention, good adhesion can be achieved with just dry firing at the waxing stage without such pretreatment. We found that it is possible to obtain In particular, for the purpose of degreasing, a cold-rolled plate is heated to a temperature of daθθ~3θOC,
Extremely excellent adhesion can be achieved by burning off the fats and oils adhering to the surface of the steel plate and generating a thin scale.

If the amount of N1 plating is less than 0.tq/m, the effect cannot be obtained, and if the amount of plating is more than 09/m2, it is necessary to install large plating equipment on the entrance side of the continuous annealing furnace. For the above reasons, the amount of N1 plating to be applied in advance during annealing was set to 0./~s, o9/m2.

Next, the present invention will be explained with reference to examples.

Example I Continuously cast slabs were made of molten steel having a composition outside the scope of the present invention as shown in Table 2 and as a comparison material having a composition outside the scope of the present invention.3. It was hot rolled to a thick thickness and wound at a winding temperature of 3°C. After that, it was cold-rolled to O0 and then continuously annealed for 10 (::' te θ°(L).

JIS s for the three directions of 1' (D) and 90° (C)
A No. 1 test piece was prepared and a tensile test was performed, and the yield strength, tensile strength, and elongation T value were all the same, and the values in the C and D directions were 3rd.
Shown in the table. In addition, in the chipping test, each sample was enameled under the conditions shown in Table 1, and samples with chipping were marked with an X mark, and samples with no chipping were marked with an ◎ mark.

(/lI) Example ■ A cold-rolled coil of the invention steel A shown in Table 1 was cold-rolled at θ, 7 degrees, and then 0.4197 m was applied to the surface of the steel plate before continuous annealing.
A coil was made with Ni plating of 2 and recrystallization annealing for geo Cx 41 seconds, and a coil without N1 plating was made, and both coils were heated at ttoo c - too c for 1 minute without enameling pretreatment. After dry melting, baking was performed for g3o CX Il, r minutes after directly wading, and then the adhesion index (P, E, I) was examined using a PEI soap tester. The results are shown in Table 7.

Table 9 As explained above, according to the present invention, a continuously cast slab having the composition of the present invention can be improved in trench-jumping resistance.

It is possible to economically provide a steel plate for enameling that has excellent wax adhesion and deep drawability.

[Brief explanation of the drawing]

The figure is a graph showing the relationship between C and N contents and chipping resistance of ultra-low carbon T1-added steel. Patent applicant Kawasaki Steel Co., Ltd. agent Patent attorney Mura 1) Politics

Claims (1)

[Claims] 1. In weight%, co, ootr or less, and Tt+C0
After continuously casting molten steel containing N and 8 within a range that satisfies the conditions shown in the following formulas (1) and (2), respectively,
Hot rolling and cold rolling are performed sequentially, and then, if necessary, the surface of the cold rolled steel sheet is plated with Ni at θ, /~, Ogr/m2, and then the temperature range from recrystallization temperature to ioθOC is applied. T1 with excellent deep drawability characterized by recrystallization annealing inside
Addition is a manufacturing method for cold-rolled steel sheets for wafers. x, 30r (N (ppm)) + (C (ppm)) 〉
//l,'l −” (2) λ 0% by weight, Co,
Molten steel containing θOt or less and Tt+C+I'L8 within a range that satisfies the conditions shown in the following formulas (1) and (2), respectively, and with Cu o,ot~0.10% added is continuously After casting, hot rolling and cold rolling are performed sequentially, and then, if necessary, the surface of the cold rolled steel sheet is coated with θ, l-co, Og
After applying Ni plating of r/m'', the recrystallization temperature to /θ
A method for manufacturing a cold rolled steel sheet for use in T1 addition with excellent deep drawability, characterized by performing recrystallization annealing within a temperature range of θoc. TI〉−C+−N+−8・・・・・・・・・(1
)1.2 7g 32×ko2.3og(
N(ppm))+(C(PI)m))> //? ,ri・(2)