JPH06248332A - Production of steel sheet for vessel - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for manufacturing an energy-saving original plate for a container that enables a further reduction in the thickness of a can, a reduction in the weight of the can, and a saving of resources. [Structure] A hot rolled sheet is cold-rolled at a rolling reduction of 60% or more to form a strong rolling texture, and the elastic modulus is increased to increase the rigidity of the steel sheet and enable thinning of the container base sheet. It enables a method of manufacturing a steel sheet without annealing. At that time, the deterioration of the workability due to the increase of the cold rolling rate is compensated by refining the steel to secure the necessary flange workability. [Effect] A thin container original plate can be manufactured without annealing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a steel sheet for containers having excellent rigidity.

[0002]

2. Description of the Related Art The properties required of materials for containers are mainly corrosion resistance and workability, but in recent years, from the viewpoint of resource saving, there has been an increasing trend toward thinning steel sheets. Along with this, deterioration of the rigidity of the container has become apparent, and demands for dealing with these have become stronger year by year.

As a method of increasing the rigidity of the container, a method of optimizing the size and shape of the container can be considered, but it is conceivable to increase the elastic modulus of the steel plate as a material. As a method of obtaining a cold rolled steel sheet having a high elastic modulus (that is, high strength), a method of adding an alloy and utilizing its solution strengthening or precipitation strengthening, a method of utilizing a quenching structure by rapid cooling after annealing, However, in addition to these methods, the texture is improved to increase the maximum elastic modulus. There is a method.

As a technique for increasing the maximum elastic coefficient of the container material by this technique, the present inventors have proposed "C: 0.
02% or less, P: 0.05% or less, S: 0.008% or less, Al: 0.05 to 0.1%, N: 0.004% or less of steel is hot-rolled and cold-rolled. In the method for producing a container material that is annealed and subjected to secondary cold rolling, the reduction ratio of secondary cold rolling is set to 50% or more and the maximum elastic modulus is 230,000MP.
We have invented and filed a technology to obtain the above materials for containers. However, this technique has a problem that the number of steps is increased and the manufacturing cost is increased because the cold rolling is performed twice with the annealing interposed.

Japanese Patent Publication No. 54-1244 discloses a process-saving technique for container materials. This is "C:
0.03% or less, Mn: 0.10 to 1.00%, Si:
Cold-rolling steel with 0.3% or less and S: 0.05% or less at a rolling reduction of 80% or more provides a steel plate for can-making with excellent workability that can be used as it is in cold rolling. " It is a thing. However, this technology does not disclose anything about the technology in the extremely low C range of C: 0.002% or less, and also regarding the rigidity, only a method of increasing the yield strength is described, and the texture is There is no disclosure of a method for improving the elastic modulus and increasing the elastic modulus.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-cost manufacturing method of a steel sheet for a container, which enhances the rigidity of the steel sheet and makes it thin.

[0007]

The gist of the present invention is as follows. C by weight%: 0.0020%
Hereinafter, Mn: 0.5% or less, P: 0.02
% Or less, S: 0.008% or less, A
1: 0.005% to 0.1%, N: 0.004
% Or less, if necessary, Ti, Zr, Nb, V, B
Steel containing 0.1% or less of one or a total of two or more of the above, with the balance being Fe and unavoidable impurities, is usually hot-rolled,
A method for producing a steel sheet for containers, which comprises pickling, followed by cold rolling for 60% or more and no annealing at all.

The present invention will be described in detail below. As a result of repeated studies on the relationship between elastic modulus and texture formation, the present inventors have revealed that the formation of rolling texture in accordance with an increase in cold rolling rate increases the maximum in-plane modulus of elasticity. . In particular, it has been found that the effect is great in a material in which a hot rolled sheet is cold rolled at a high pressure reduction rate. An increase in the elastic modulus means an increase in rigidity, which compensates for the deterioration in rigidity that accompanies thinner container materials, and has enabled the development of thinner container materials, which is a market need. However, in the case of ordinary steel sheets for containers, when the cold rolling rate exceeds 50%, work hardening becomes remarkable, and cracks are likely to occur during flange processing that is usually performed in the processing of container materials, which makes practical application difficult. Therefore, the present inventors drastically reviewed the component system of the container material, researched a method for producing a steel sheet that exhibits good flange formability even with a high cold rolling rate material, and has excellent rigidity, and the components and the cold rolling rate. By regulating the above, it has succeeded in producing a steel plate having excellent rigidity without cracking in the working process required in the general can manufacturing process.

Next, the reasons for limitation of the present invention based on the above findings will be described. When a normal hot-rolled sheet is cold-rolled, the maximum elastic modulus in the plate surface with respect to the cold-rolling rate increases when the cold-rolling rate exceeds 60%. This corresponds to the strong development of a texture in which the <110> orientation is parallel to the rolling direction and a texture in which the <111> orientation is perpendicular to the steel sheet surface in the cold rolling ratio of this region. Therefore, the cold rolling rate is set to 60% or more. In the present invention, the cold rolling rate is limited to 60% or more because the thickness of the currently required container material is 0.25 mm or less from the viewpoint of weight reduction. In order to obtain the sheet thickness, it is disadvantageous if the sheet thickness of the hot-rolled sheet becomes too thin considering productivity,
The lower limit of the cold rolling rate is preferably 60% or more.

On the other hand, it has been stated that work hardening accompanied with an increase in cold rolling rate deteriorates local ductility and causes a hindrance to the flange formability required for can forming. By examining the relationship between the flange formability and the composition, the composition of the steel in the present invention was limited for the following reasons. That is, C content is 0.002 wt% or less, Mn is 0.5 wt% or less, N content is 0.004 wt% or less, and S content is 0.008 wt%.
Below, the P amount is limited to 0.02 wt% or less and the Al amount is limited to 0.1 wt% or less, if the addition of these alloying elements is within these limiting conditions, the cold rolling rate is 60% or more. This is because, in the rolled material, the elastic modulus is remarkably improved in a state where no annealing is performed and the frequency of occurrence of cracks during flange processing during can forming is extremely low.

Further, if one or more of Ti, Zr, Nb, V and B are added so that the total amount thereof is 0.1 wt% or less, the frequency of cracking becomes smaller. This is considered to be due to the effect that these elements form carbonitrides and reduce the solute C and N. Also, addition of Ti and Zr is Mn
It becomes particularly effective when the addition amount of is relatively small. This is considered to be because these elements form sulfides and reduce solid solution S. When Mn is relatively large, S is MnS
Is considered to exist in the form of a precipitate. Due to the limitation of the components, the improvement of the elastic modulus was observed as in the present invention.By reducing the components, the crystal rotation smoothly occurred during cold rolling, and the preferable texture was formed for the improvement of the elastic modulus. it is conceivable that. Ti, Zr, Nb, V, B
The total addition amount of one or more of the above is limited to 0.1 wt% or less because the addition of more than that increases the occurrence frequency of flange cracks.

It is considered that the manifestation of flange cracks due to an increase in the amount of alloying elements added is due to the deterioration of ductility due to the increase of additional elements promoting the growth of dislocations due to working and promoting work hardening. On the other hand, in the case of the steel of the present invention in which the additive elements are reduced as much as possible and the steel is highly purified, the cell structure is formed in the region of the cold rolling rate of 60% or more, and even if the cold rolling rate is increased, the cell size is remarkable. No significant change is seen and the change in hardness is small.
This seems to be the reason why the flange formability of the steel of the present invention does not deteriorate so much due to the increase in cold rolling rate.

The lower limit of the amount of Al added is determined by the minimum amount necessary for the deoxidizing treatment, and is 0.005 wt%.

Since the present invention does not largely depend on the history before cold rolling, the hot rolling conditions such as the finishing temperature FT and the coiling temperature CT and the annealing conditions such as the heating rate and the annealing temperature are not particularly limited. Therefore, even if the material before cold rolling is a cast plate manufactured by the twin roll method or the like, it does not impair the gist of the present invention.

[0015]

EXAMPLES Table 1 shows the chemical composition of the steel of the present invention and the comparative steel.
Figure 1 shows hardness H when material A is used and the cold rolling ratio is changed.
_R30T , the maximum elastic modulus measured by the lateral vibration method, and the change in the value of elongation (referred to as local elongation here) measured at a gauge length of 6 mm, which is a measure of the flange workability, which is the most susceptible to cracking in can forming, Show. The plate thickness during the characteristic test was adjusted to 0.25 mm. As described above, the hardness and the local elongation change little at a cold rolling rate of 60% or more, and the maximum elastic modulus decreases at a small rate, but increases in the present experimental range as the cold rolling rate increases. It is considered that this is because, as described above, the cell structure of the material became steady and the changes in hardness and ductility became small in the range where the cold rolling rate was large. Also, the reason why the maximum elastic modulus continues to increase, although gradually, is considered to be that the texture continues to change due to crystal rotation.

[0016]

[Table 1]

[0017]

[Table 2]

Table 2 shows the values of the cold rolling ratio of 88%, the hardness without annealing, the maximum elastic modulus and the local elongation of the steels of Table 1. If the local elongation is 10% or less, cracking frequently occurs during flange processing which is usually performed in can forming. As shown in this table, in this component range, the change in the maximum elastic coefficient due to the component is relatively small, but the influence on the workability is significant. Thus, it is shown that if an element is added in an amount exceeding the range of the present invention, workability deteriorates, and can forming becomes difficult with a material having a high cold rolling rate.

[0019]

According to the present invention, the rigidity of the can is improved, the can material can be further thinned, and resource saving can be achieved. Also, the manufacturing process can be simplified, which is of great industrial significance.

[Brief description of drawings]

FIG. 1 is a drawing of a hot-rolled sheet of material A, which is cold-rolled by changing the reduction rate, and shows the maximum elastic modulus, hardness, and local elongation in the sheet plane at that time.
The horizontal axis represents the cold rolling rate.

Claims (2)

[Claims] 1. By weight%, C: 0.0020% or less, Mn: 0.5% or less, P: 0.02% or less, S: 0.008% or less, Al: 0.005% to 0.1. %, N: 0.004% or less, the balance of which is Fe and unavoidable impurities in the balance, which is normally hot-rolled, pickled, cold-rolled by 60% or more, and then not annealed at all. Method for manufacturing steel sheet. 2. By weight%, C: 0.0020% or less, Mn: 0.5% or less, P: 0.02% or less, S: 0.008% or less, Al: 0.005% to 0.1. %, N: 0.004% or less, a total of 0.1% or less of one or more of Ti, Zr, Nb, V, and B, and a balance of Fe and unavoidable impurities in the ordinary hot rolling. A method for producing a steel sheet for containers, which comprises pickling, cold rolling by 60% or more, and then performing no annealing.