JPH08127816A - Production of starting steel sheet for vessel, excellent in wrinkling resistance - Google Patents

Abstract

PURPOSE: To reduce the occurrence of wrinkle and flange cracking at the time of can manufacture by applying lubricating rolling to a steel of specific composition at a temp. in a specific region, specifying total draft and sheet thickness, respectively, performing.recrystallization annealing, and then subjecting the resulting sheet to specific cold rolling. CONSTITUTION: A steel, having a composition consisting of, by weight, <=0.01% C, <=0.01% N, 0.005-0.5% Al, Ti and/or Nb under the condition of C/12+N/14+S /32<1.2(Ti/48+Nb/93), and the balance Fe with inevitable impurities, is used. This steel is subjected to lubricating rolling at a temp. in the range between the Ar, transformation point and 500 deg.C at <=0.2 average friction coefficient, and total draft and sheet thickness are regulated to >=50% and 1.4-0.6mm, respectively, and then recrystallization annealing is performed in the course of cooling, coiling, or annealing. After acid pickling, cold rolling is executed at 60-80% to regulate sheet thickness to 0.24-0.1mm, and annealing is not applied. By this method, energy saving can be attained by omitting annealing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a low cost steel sheet for containers which is excellent in wrinkle resistance and flange formability.

[0002]

2. Description of the Related Art A conventional method for manufacturing a steel sheet for containers is hot rolling.
It is manufactured by finishing at r ₃ transformation point or higher, pickling, cold rolling about 90%, annealing, and skin pass.
The production of 2CR materials with a high skin pass ratio after annealing is also becoming established. The production of 2CR has begun to attract a lot of attention in connection with the thinning of container original plates. That is, in order to meet the demand for cost reduction and weight reduction as market needs, if the original plate for a container is thinned by a normal manufacturing method, the thickness of the cold-rolled sheet becomes thin, and heat buckles easily occur during continuous annealing. Manufacturing becomes difficult. Therefore, secure a certain thickness until annealing, and after annealing, 20%
2CR technology for achieving a high skin pass of 50% has been developed and is disclosed in Japanese Examined Patent Publication No. 1-52451. However, this method does not always meet the market needs for cost reduction.

On the other hand, as a method of manufacturing a low-priced container original plate, a cold rolled material manufacturing technique is disclosed. But,
Normal cold-rolled material has poor formability, and its range of use as a container base plate is extremely limited.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a problem in the above-mentioned prior art, that is, a method for improving the formability of an original plate for a container of a cold-rolled material.

[0005]

According to the present invention, the following findings have been obtained as a result of detailed experiments conducted on the formability of cold-rolled material. 1) The lower the cold rolling rate, the better the formability, but especially the cold rolling rate is 8
If it exceeds 5%, wrinkle resistance and flange formability are significantly deteriorated. 2) The wrinkle resistance and flange formability are worse as the plate thickness is thinner. 3) The workability is affected by the chemical constituents of the steel, and when the cold rolling rate is 85% or less, the decrease in the C content has an advantageous effect on the workability. In particular, Ti, Nb, etc. are added to reduce the solid solution C content. It is effective to do. 4) Wrinkle resistance and flange formability are improved by rolling at least 50% or more by rolling hot rolling in the ferrite region. In particular, the effect is large when the coefficient of friction between the roll and the steel sheet during rolling is 0.2 or less. 5) In order to obtain the effect of lubrication hot rolling in the ferrite region of 4), it is essential to combine with the components, such as ultra low carbon steel, Ti,
It is necessary to add Nb to reduce the solid solution C as much as possible.

Based on these findings, the basic principle for improving the formability of as-cold rolled material was examined. Since thinning of the container material deteriorates wrinkle resistance and flanging workability, the cold-rolled material produced by the technology disclosed thus far is currently being studied as a container base plate with a thickness of about 0.2 mm. Cannot be used as. Therefore, as a means for ensuring the formability required for forming a container, firstly, it is necessary to reduce the cold rolling rate as much as possible. If the thickness of the container base plate is 0.2 mm and the cold rolling ratio is 80%, the thickness of the hot rolled plate must be 1 mm.

The reason for the lubrication hot rolling in the ferrite region, which is the point of the present invention, is due to the physical reason of metal as will be described later, but it is also an advantageous technique in terms of manufacturing technology. That is, if a 1 mm hot-rolled sheet is to be finish-rolled at the Ar ₃ transformation point or higher, there are problems in operation such as a higher heating temperature and the use of an edge heater.
Rolling below the r ₃ transformation point eases the operation because temperature restrictions are relaxed. Moreover, by performing the lubrication rolling, it is possible to minimize an increase in rolling load and rolling torque due to a reduction in rolling temperature.

The reason why the hot rolling lubrication in the ferrite region works favorably on the formability of the original plate for a container is not always clear, but it is considered that the r value of the hot rolled plate and the state of precipitates have an influence. That is, hot rolling in the ferrite region causes coarsening of precipitates containing Ti, Nb, etc., softens the steel, relaxes work hardening during cold rolling, and compares the yield point (YP) after cold rolling. It is considered that the wrinkle resistance and the flanging workability are improved by being able to suppress it to an extremely low level. In addition, the effect of lubrication is to improve the texture of hot-rolled sheet over the entire thickness by combining with solid solution C reduction of steel {111}.
The main texture can be formed, and a hot rolled steel sheet with a high r value can be manufactured. When this steel sheet is cold rolled, it rotates around <111> // ND and strong {111} is formed even after cold rolling. It is considered that necking such a steel sheet suppresses the change in strain in the sheet thickness direction and suppresses the occurrence of wrinkles.

From the above technical idea, the gist of the present invention is that C: 0.01% or less, N: 0.01% or less,
Al: 0.005% or more and 0.5% or less, and either or both of Ti and Nb are C / 12 + N / 14 +
Steel containing S / 32 <1.2 (Ti / 48 + Nb / 93) so as to satisfy the condition, balance Fe and unavoidable impurities is used as the average friction coefficient in the temperature range below the Ar ₃ transformation point and above 500 ° C. Is 0.2 or less, the total rolling reduction is 50% or more, the thickness of the hot rolled sheet is 1.4 mm or less and 0.6 mm or more, and then recrystallization is performed in the cooling, winding or annealing process, After normal pickling, 60% or more 85
% Cold-rolled with a thickness of 0.24mm or less 0.1mm
The above is the method for manufacturing a steel sheet for containers, which is characterized in that the subsequent annealing is not performed.

The present invention will be described in detail below. In the present invention, either one or both of Ti and Nb C /
12 + N / 14 + S / 32 <1.2 (Ti / 48 + Nb
/ 93) is added so as to satisfy the relationship of (93). The reason is that C and N in the steel are mostly fixed in the form of precipitates to reduce the solid solution C and N as much as possible, This is because the texture is mainly composed of {111}, work hardening is suppressed, and wrinkles are prevented from occurring during neck processing of can forming.

On the other hand, C: 0.01% or less, N: 0.01
%, The amount of Ti or Nb required to satisfy the above conditional expression is increased if C, N, and S are added in excess of these amounts, and not only the workability of the product is impaired, but the manufacturing cost is increased. This is because it is disadvantageous in terms of. The lower limit of the amount of Al added is set to 0.005% because if it is added below this amount, deoxidation is not sufficiently achieved, the amount of inclusions increases, and the frequency of breakage during can forming increases. Further, the upper limit is set to 0.5% because workability deteriorates.
Incidentally, in the present invention, as other components, components usually contained for improving strength, that is, Si: 1.0% or less, Mn:
You may make it contain 1.5% or less and P: 0.15% or less. Further, addition of 0.0050% or less of B does not impair the gist of the present invention.

Next, the hot rolling conditions are limited for the following reasons.
When the hot rolling finishing temperature is equal to or higher than the Ar ₃ transformation point, the crystal orientation distribution is randomized during the γ → α transformation, so that it is difficult to form a texture having a specific orientation preferentially. When hot-rolling below the transformation point, it is possible to form a texture preferentially with a specific orientation, but in order to manufacture a hot-rolled steel sheet with {111} in the main orientation, the prescribed conditions must be satisfied. . One of them is a limiting condition for the above components, and the other is a hot rolling condition. Hot rolling finish temperature is Ar ₃ transformation point (Ar
₃ [° C] = 916-509C (wt%) + 27Si (w
t%)-64 Mn (wt%)) or less, and if the total rolling reduction below the Ar ₃ transformation point is 50% or less, {111} is difficult to develop even when rolled in a lubricated state. When rolled without lubrication, {111} does not develop in the vicinity of the surface layer even if the total rolling reduction below the Ar ₃ transformation point is 50%. When the coefficient of friction between the roll and the steel sheet during rolling becomes 0.2 or less, {111} develops over the entire thickness of the sheet, and the r value remarkably improves. Along with this, the frequency of wrinkles decreases and the flange formability also improves.

The lower limit of the rolling finish temperature is set to 500 ° C., because hot rolling at a temperature lower than this temperature increases deformation resistance and economical rolling cannot be performed. Even if it is finish rolled, it cannot be replaced. Further, the hot-rolled sheet needs to be in a recrystallized state and must be recrystallized by a winding process or a separate annealing during cooling after hot rolling.

The cold rolling rate is limited to 60% or more and 85% or less because excellent moldability cannot be obtained when the cold rolling rate is 85% or more. Further, the lower limit is set to 60% because if the cold rolling rate becomes too small, it is necessary to reduce the thickness of the hot rolled sheet, which hinders the hot rolling operation.
In addition, the reason why the final plate thickness is 0.24 mm or less and 0.1 mm or more is that there is no merit of weight reduction when the plate thickness exceeds 0.24 mm. This is because it is difficult to meet the needs of cost reduction because of poor performance and possibility of deterioration of shape. Further, the reason why the thickness of the hot-rolled sheet is limited to 1.4 mm or less and 0.6 mm or more is that if the hot-rolled sheet becomes thicker than this, a predetermined final sheet thickness cannot be obtained at an appropriate cold rolling rate. On the other hand, if the thickness of the hot-rolled sheet becomes thinner than this, the hot-rolling operation will be hindered.

[0015]

EXAMPLES Examples of the present invention will be described together with comparative examples.
Steels having the chemical compositions shown in Table 1 were hot rolled under various conditions. Here, Ar ₃ was obtained by measuring the starting temperature of the γ → α transformation when cooled at a cooling rate of 10 ° C./sec using a Formaster. Table 2 shows the manufacturing conditions when a container original plate was manufactured using these steel types and the workability when a can was manufactured using the same. Hot rolling was performed by heating a slab having a thickness of 250 mm at a temperature between 1100 ° C and 1250 ° C except for Experiment No. 6,
After rolling in the zone, hot rolling in the α zone is performed. Experiment No. 6 is all hot rolled in the γ region.

DI (Dra
Wing & Ironing) Welded cans and welded cans are arranged according to neck processability and subsequent flange processability. As a quantitative evaluation, 100 cans were manufactured with a can manufacturing machine in the lab, and the rate of defective cans at that time was%.
Indicated by. The amount of tin plating is 2.8 g per 1 square meter for DI cans and 1 g per square meter for welded cans. Neck processing was performed using a spin necker. A spin flanger was used for flanging.

Experiment numbers 1, 2, within the scope of the present invention
3, 4, 5, 11, 12, 13, and 14 have good neck workability and flange workability. On the other hand,
Experiment No. 6 completed in the area had a high frequency of defects.
In addition, in the experiment number 8 which is 43% in the temperature range below the Ar ₃ transformation point and in the temperature range of 500 ° C. or more, which is outside the range of the present invention, and the experiment number 7 in which the average coefficient of friction was as high as 0.226, the defect occurrence frequency Was high. In the case of Experiment Nos. 9 and 10 in which the cold rolling rate was 90%, which was above the range of the present invention, the occurrence rate of defects was extremely high. In particular, in Experiment No. 10 in which the final plate thickness is thin, defects are significantly generated. In Experiment No. 9 using steel in which the amount of C added was more than the range of the present invention, defects were significantly generated during can making. The amount of Ti and Nb added is C / 12 + N / 14 + S / 3
In experiments Nos. 16 and 17 using steels that did not satisfy the condition of 2 <1.2 (Ti / 48 + Nb / 93), solid solution C,
Defects occurred probably because there was a large amount of N.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

EFFECTS OF THE INVENTION According to the present invention, it is possible to reduce the occurrence of wrinkles and flange cracks at the time of can manufacturing that have become apparent with the thinning of container original plates, and energy saving can be achieved by omitting annealing, which is industrially possible. It is a valuable invention.

Claims (1)

[Claims] 1. By weight%, C: 0.01% or less, N:
0.01% or less, Al: 0.005% or more and 0.5% or less, and either or both of Ti and Nb,
C / 12 + N / 14 + S / 32 <1.2 (Ti / 48 +
Nb / 93) so as to satisfy the condition
Steel consisting of e and unavoidable impurities is lubricated and rolled with an average friction coefficient of 0.2 or less in a temperature range of 500 ° C. or higher below the Ar ₃ transformation point, and the total rolling reduction is 50% or higher. Of 1.4 mm or more and 0.6 mm or more, and then recrystallized in a cooling, winding or annealing process, and after ordinary pickling, cold rolling of 60% or more and 85% or less is performed to obtain a plate thickness of 0.
A method for producing a steel sheet for containers, which is characterized by having a thickness of 24 mm or less and 0.1 mm or more and not performing annealing thereafter.