JPS59110722A - Direct hot rolling of aluminum killed steel - Google Patents

Abstract

PURPOSE:To certainly enhance the deep drawing property of the edge part in a cold annealed steel plate in low cost, by a method wherein aluminum killed steel containing C, Mn, Sol, Al, P and N respectively in a predetermined ratio is continuously cast to obtain a steel piece which is then succeedingly heated to a specific temp. or more to be subjected to hot rolling. CONSTITUTION:Aluminum killed steel containing, on a wt. ratio, 0.10%- or less C, 0.50% or less Mn, 0.10% or less P, 0.010-0.100% Sol, Al and 0.0010-0.0100% N and comprising the remainder of Fe and inevitable impurities is continuously cast to prepare a steel piece. Suceedingly, the vicinity of this steel piece is heated to 1,150 deg.C or more for a short time to raise the temp. thereof and, after precipitated AlN is re-melted, the heated steel piece is hot rolled so that a finish temp. is brought to an Ar3-deformation temp. or more. That is, the latent heat possessed by the high temp. steel piece directly after continuous casting is effectively utilized to directly connect hot rolling to continuous casting and a cold annealed steel plate having aforementioned characteristics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for directly hot rolling aluminum killed steel, which enables continuous casting of aluminum killed steel to be simply and efficiently hot rolled, and improves the deep drawability of the edge portion of a cold rolled annealed plate. The purpose is to provide a method that can improve the performance accurately and at low cost.

Various studies have been made to obtain excellent deep drawability (γ value) in batch-annealed cold-rolled steel sheets using aluminum-killed steel, but the key points in manufacturing in this case are: 5oLA/amount from 0.030 to 0
．． 060 wt%, N amount 0.0030 to 0.0060
wt%, ■ Slab by hot rolling 1200-130
After heating to 0℃ for about 4 hours, 7 precipitated in the slab after casting.
After remelting 4/N, ■ Rolling is carried out at a finishing temperature equal to or higher than the Arc transformation point up to the edges of the strip, ■ The coiling temperature is set to 600°C or less to prevent precipitation of MN, and ■ During batch annealing after cold rolling. for example, by optimizing the heating rate of the

By the way, in the conventional method, which is carried out according to each of the points mentioned above, among the points, regarding the heating of the slab (2), the slab that has been cooled to room temperature after continuous casting is heated to 1200 to 13
This is because once the slab is cooled to room temperature, a large amount of N grows in the center, and heating at high temperatures is required to completely redissolve it. This is due to the fact that it takes a long time to raise the temperature to a high temperature in the central part of a large slab. However, heating at such a high temperature and over a long period of time increases the energy cost for heating, increases manufacturing costs, and has undesirable disadvantages in terms of operational efficiency and other aspects.

The present invention was devised after consideration to eliminate the disadvantages of the conventional methods as described above, and C: 0
．． 10 wt% (hereinafter simply referred to as Chi) or less, b: o, s
o% or less, P:O, 10% or less, soL A/: 0
．． 010-0.100%, N: 0.0010-0.
After continuously casting aluminum killed steel containing 0100% and the remainder consisting of h and unavoidable impurities into a steel billet,
The proposal is to continue hot rolling by heating the vicinity of the slab edge to 1150°C or higher, making effective use of the latent heat held by the high-temperature slab immediately after continuous casting, and directly linking hot rolling to continuous casting. It is something to do.

That is, to further explain the present invention, the present inventors have carefully considered hot rolling the slab without cooling it after continuous casting in order to avoid the disadvantages of the conventional method as described above. As a result of the continuously cast slab being cooled to form a solidified shell in the surface layer and edge portions at the initial stage of casting, 4/N was precipitated in those portions, and therefore hot rolling was performed as is. However, it was confirmed that those parts were finished at a low temperature, and the quality of the steel sheet deteriorated significantly even if batch annealing was performed after cold rolling. As an example regarding this matter, the AtN precipitation range and A immediately after casting when low C-, 4/killed steel is continuously cast at a casting speed of 1.2 mpm.
The results of measuring the IN precipitation size are as shown in Figure 1, and the diameter of 74/N is less than 01 μm in the range of 20 degrees in the 45-degree direction from the slab corner, but in the range of 3t'2 to
0.2 to 0.3 in the range of 50f211+I+
It is Aim. Further, a typical form of IN precipitation at this time is as shown in FIG. 2, but 4/N is not precipitated inside 50)'2+mn. However, if such a slab is directly hot-rolled as described above, AIN will precipitate in the hot rolling range within 50 mm from the edge, and the finishing temperature will be low, so it must be carefully batch-rolled after cold-rolling. Even if annealing is performed, the material quality of the steel sheet will inevitably deteriorate significantly.

Therefore, in the present invention, in order to solve the above problems,
The surface layer and edge portion of the slab after continuous casting are heated for a short time to raise the temperature of the slab, remelting the precipitated μN, and raising the finishing temperature in hot rolling to the Ar3 transformation point or higher, Figure 3 shows that in order to dissolve the AIN precipitated near the slab edges of low C-killed steel, the slab was heated to 110°C and 1250°C for 1 minute and 5 minutes, followed by normal hot rolling and then cold rolling. γ value (γ.) in the rolling direction at edge 25- of the box-annealed steel plate
However, from this result, in order to completely dissolve AtN and make the 7 value of the cold rolled annealed sheet equal to that of the normally heated material, 1200
℃ for more than 1 minute. In addition, regarding the heating temperature in this case, if the heating temperature is 1100°C or lower, the precipitated AtN cannot be sufficiently dissolved even by heating for 5 minutes or more, so the filtration value will not improve appropriately. It is clear that improvements can be made. Note that those heated at 1,200°C for 5 minutes and those heated for 5 minutes at 1,250°C are equivalent, and this means that the depth after cold rolling that is commensurate with the heating price is higher than that for heating at a higher temperature or for a longer time. This shows that the effect of improving drawing property cannot be brought about.

The reason for limiting the steel components in the present invention is as follows. C
If the amount is 0.10% or more, the Mn amount is 0.50% or more, and the P amount is 0.101 or more, the strength of the material increases after cold rolling annealing and the ductility deteriorates. Sound must be limited to less than the above amount. Also, the amount of acid soluble
) 10 wf% or less or 0.100% or more, set the N amount to 0.
D010% or less? When it is 0100% or more, the deep drawability after cold rolling annealing deteriorates, so soL/1/ is 0.010 to 0.100%, and N is 0.0010 to 0.0.
It was set as 100%.

Examples of the present invention will be described below.

Example 1: Ladle components were C: 0.05%, SL: 0.
01%, Mn: 020%, P: 0.015%,
S: 0.020%X5oLA1: 0050%, N
: Immediately after casting a slab of 0.0050% low C-7 lumikilled steel cast at a casting speed of 1.21", a range of 50+m from the edge of the slab is heated to a temperature of 1100 to 1250°C for 1 minute, and then The finishing temperature was 870°C and the coiling temperature was 560°C.
% cold rolling, box annealing at 650°C, and measuring the γ0 value in the width direction of the plate after box annealing, the results are representative of those at heating temperatures of 1100°C, 1150°C, and 1200°C. This is shown in Figure 4. That is, 11
When heated at 50°C or lower, the b value near the edge is considerably lower than that in the center part, but in the case of heating at 1200°C, the value near the edge approaches that in the center part even after heating for 1 minute, and the width decreases. The material in the direction was uniform.

Example 2 The salt component is C: 0.02% 1.9j: 0.01
%, Mn=0.15%, P: 0.010%, S: 0
．． 010%, 801. /1/: 0.040%, N:
Casting speed 1 of 0.0030% medium-low C aluminum killed steel
．． Immediately after casting, the slabs cast in 5 towns were cast in a range of 1100 to 1 tRM from the edge.
It was heated to 250°C for 1 minute, then hot rolled in the usual manner, followed by 75% cold rolling and box annealing at 650°C. Figure 5 shows the thickness of the annealed plates in the width direction at 1100°C, 1150°C and 1200°C.
γ near the edge by heating above 0°C. By bringing the value closer to that near the center, the material quality in the width direction of the caulking plate is made uniform.

According to the present invention as explained above, aluminum killed steel for cold rolling is continuously cast and then directly hot rolled to obtain a desirable product. In other words, AtN precipitated on the slab edge and near the surface layer after casting is removed from the slab edge near the edge. It is possible to effectively improve deep drawability by heating the melt effectively and completing hot rolling above the Arc transformation point.Moreover, since the heating is only partial and for a relatively short time, It is an invention that has great advantages in terms of energy and efficiency, and has great industrial effects.

[Brief explanation of the drawing]

The drawings show the technical contents of the present invention, and Fig. 1 is an explanatory diagram showing the LeN precipitation situation in the cross section of the slab immediately after the continuation. Magnification 100 showing N precipitation form in slab
0x micrograph, Figure 3 is a chart showing changes in stone value for low-pressure annealed plates depending on the heating temperature of the slab edge, and Figure 4 is a chart showing changes in γθ value in the width direction of low C aluminum killed steel annealed plates. , FIG. 5 is a chart showing four-value changes in the width direction for medium-low C aluminum killed steel annealed plates. Special punch application submitted Nippon Kokan Co., Ltd. Inventor Takashi Shimomura Nagama
Kobayashi Hideo c vote 1■゛＼ 8 solid and 緘J mipugu condemned beak procedural amendment (fading) 121st, 1958 Kazu Wakasugi, Commissioner of the Japan Patent Office Failure 1, indication of the case 2. Related to the Invention 0 Name Case Patent Applicant Name (low name) Nippon Koukan Co., Ltd. 4, Contents of the amendment as shown in the agent's attachment 1, Inner box of the application, page 4, line 7, ``Therefore, it will remain as it is.''"Just like this again," I corrected. 2, same page 6] line 7 [the amount of 0.01. Owg%J
Correct the statement to ``The amount of is 08010%''. 3. On page 9, line 8, ``Desaru etc.'' should be corrected to ``Desaru etc.''. 4. On the 15th line of the gap, replace the text "Magnification 1. OOO cultivation" with "
The magnification is 1.00.00x”. 5. On the same page, line 17, ``Regarding low-pressure annealed plates'' is changed to ``
It is corrected to read "Regarding cold-pressure annealed plates." -10 no

Claims (1)

[Claims] C: 0.10wt% or less, Mn: 0.50wt%
Below, sol, A/: 0.010-0100 wt
%, P: (110wt% or less, N: -0,00
After continuously casting aluminum killed steel containing 10 to 0.0100 wt% and the remainder consisting of h and unavoidable impurities to form a steel billet, 115
A direct hot rolling method for aluminum killed steel, characterized by heating to 0° C. or higher and hot rolling.