JPH036331A - Manufacture of cold rolled steel sheet for porcelain enameling having excellent fishscale resistance - Google Patents

Abstract

PURPOSE:To improve the fishscale resistance of the steel sheet and to eliminate its dispersion in the steel sheet by subjecting a slab having specified contents of N, B, etc., to hot direct rolling, coiling it at a specified temp. and executing cold rolling and continuous annealing. CONSTITUTION:A steel constituted of 0.02 to 0.08% C, 0.08 to 0.50% Mn, 0.005 to 0.006% sol.Al., <=0.0050% N, -0.0010 to 0.0010% B as satisfying N--(14/11).B and the balance Fe with inevitable impurities is subjected to continuous casting. The slab is cut at >=900 deg.C, and, as it is or after subjected to auxiliary heating, within 40min, is subjected to hot direct rolling. The steel is subjected to finish rolling and is thereafter coiled at 600 to 750 deg.C. Next, it is cold-rolled and is subjected to continuous annealing. In this way, uniform porcelain enameling characteristics can be obtd. in a coil without adding expensive alloy elements.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a cold-rolled steel plate for enameling which has excellent resistance to chipping.

(Prior technology) Capped steel has traditionally been used as a cold-rolled steel plate for enamel with excellent tear resistance, but in order to reduce production costs, continuous casting has been studied instead of the ingot method. Several methods have been disclosed. 1st
For example, as disclosed in Japanese Unexamined Patent Publication No. 132-270727, the amount of oxygen in the steel is increased to a level greater than that of capped steel, but this method requires very strict control in the steelmaking process in order to eliminate surface defects. Therefore, it cannot be said that it is an easy manufacturing method. Furthermore, there are also difficulties in terms of processability. The second is
For example, as in Japanese Patent Application Laid-Open No. 60-110845, Ti
This is a method of adding carbide-forming elements such as and Nb.
In this method, in order to improve workability, it is necessary to reduce carbon to an extremely low level by a vacuum degassing treatment method, which significantly increases manufacturing costs. The third method is to lump the carbide by high-temperature winding during hot rolling, but this method does not improve the ends of the coil.

(Problems to be Solved by the Invention) The present invention solves these problems in view of the difficulty of steel manufacturing work, the necessity of vacuum degassing treatment, and the variation in quality within the coil, which are problems with conventional technology. It is an object of the present invention to provide a method for manufacturing a cold rolled steel plate for enameling which is inexpensive, has excellent resistance to sagging, and has no variation within the steel plate.

(Means for Solving the Problems) The present invention provides C: 0.02 to 0.08%, Mn: 0.0
8-0.50%, so! , AN: 0.005-0.0
6%, N: 0.0050% or more, 0.0010% or more,
Direct hot rolling of continuously cast slabs, the remainder of which is iron and unavoidable impurities, is started at 900°C or higher after cutting within 40 minutes, either as is or with auxiliary heating, and after finishing rolling, the slabs are heated to 600-750°C. This is a method for producing a cold-rolled steel sheet for enameling having excellent roll resistance, which is characterized in that it is wound up, cold-rolled, and then continuously annealed.

The present invention will be explained in detail below.

C is required to be 0.02% or more in order to use carbides in steel to improve chipping resistance. However, if it is too thin, workability will deteriorate, so it should be kept at 0.08% or less.

Mn is set to 0.08% or more in order to prevent hot embrittlement and improve flaking resistance. On the other hand, if the amount is too large, the effect of improving the chipping resistance will be weakened and the workability will also be reduced, so 0.5
0% or less.

Aρ becomes acid soluble for deoxidation 1! Bind 0.005%
However, if it is too large, it will reduce the workability, so 0
．． 0.6% or less.

Since N is an element harmful to workability, it is preferably as low as possible from the viewpoint of workability, and is preferably 0.0050% or more.

When it is less than 0.0030%, the effect of improving workability is great.

It is important for B to fix N to the container and to control the amount of tolerability, and the amount of B must be 0.0010% or less. However, since a large amount of B content reduces processability,-
0,0010% or more.

After continuous casting of the above-mentioned component steel, hot rolling is started either as it is or with auxiliary heating by the so-called direct rolling method, but direct hot rolling is started within 40 minutes after cutting the slab at 900°C or higher. do. This means that if the slab is cut at less than 900°C, or if it is cut at 900°C or more for more than 40 minutes, the surface temperature of the slab will drop significantly, and if it stays at 600°C or less for more than 30 minutes, it will not survive. This is because it becomes difficult to obtain the effect of improving the jumpability, and variation occurs in the jumpability resistance within the steel plate coil.

The finishing temperature of hot rolling is preferably at least the Ar 3-point transformation point in order to ensure workability. The winding temperature is set to 600° C. or higher from the viewpoint of resistance to slippage and processability, but if it is too high, the pickling property is significantly reduced, so the upper limit is set to 750° C. Preferably it is 650-700°C.

In cold rolling, the rolling reduction should be at least 60% to improve the resistance to tipping, but if it is too high it will have the opposite effect, so the rolling reduction should be 85%.
The following shall apply.

Next, recrystallization annealing is performed by continuous annealing. This is because continuous annealing results in more uniform tear resistance within the coil than in the conventional box annealing method. The annealing temperature is
A high temperature is preferable for improving the properties; however, if the temperature is too high, the flaking resistance decreases, so a temperature of 700 to 600°C is preferable. After annealing, temper rolling is usually performed at a rate of about 1%.

(Example) Steels with the components shown in Table 1 were continuously cast, and then hot rolled by direct rolling and normal reheating and then rolling (reheating temperature: 1150°C). In direct rolling, the thermal history up to the start of hot rolling was changed. The finishing temperature of hot rolling is 900℃ and the plate thickness is 2.8m.
After finishing to n+, the winding temperature was varied between 600 and 750°C. After pickling, it was cold rolled to 0.8+n+n, then continuously annealed at 750° C., and temper rolled to 1.0%. The jumpability of the obtained steel plate was evaluated at the tip, middle, and back of the coil, and its mechanical properties were also investigated.

The results are shown in Table 2 together with the manufacturing conditions.

The steel sheet manufactured by the method of the present invention has a longer hydrogen permeation time than the conventional steel sheet produced by reheating and rolling, and exhibits excellent stumbling resistance with less variation within the coil and excellent uniformity. Also, for boat fishing, continuous annealing of directly rolled material results in significantly inferior mechanical properties to conventional reheated rolled material. shows.

(Effects of the Invention) The cold-rolled steel sheet for enameling manufactured by the method of the present invention has uniform enameled properties within the coil without adding expensive alloying elements, and can be easily processed by direct rolling and continuous annealing. The fact that manufacturing costs can be significantly reduced by omitting i9+ is of great industrial significance.

sub-agent

Claims (1)

[Claims] (1) C: 0.02-0.08%, Mn: 0.08-0
．． 50%, sol. Al: 0.005-0.06%, N
: 0.0050% or less, B: N-(14/11)・B from 0.0010% or less to -0.0010% or more, the balance being iron and unavoidable impurities. Direct hot rolling is started within 40 minutes after cutting, either as it is or by applying auxiliary heating, and after finish rolling, winding is performed at 600 to 750°C, and continuous annealing is performed after cold rolling. A method for manufacturing cold-rolled steel sheets for enamel with excellent jumpability.