JPS63310922A - Manufacturing method of 2CR material for welded cans with excellent flange workability by continuous annealing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a ZCR material for bath welding cans that has excellent flanging properties by continuous annealing.

(Prior Art) Conventionally, three-piece can bodies have been joined by soldering, resin bonding, and welding.

Among these methods, welding has a better material yield than soldering or resin bonding because (1) the joining cost is smaller;

(2) Since the wrap portion is thin, airtightness and rollability are good.

(3) Strong side seams.

(4) Excellent printing effect because the printing clearance can be narrowed.

(5) Solder may not jump in.

Because of the numerous advantages such as these, three-piece can production has become mainstream in recent years, and its application has expanded from three-piece food cans to aerosol cans, miscellaneous cans, and the like. (Hereinafter referred to as a welded can) The manufacturing method for this welded can is to pass a high-frequency, high-voltage current through a copper wire from two electrode rolls, pressurize it at the same time, and the can material becomes a resistance and generates heat. Electric resistance welding is common, which involves welding with a lap thickness of about 100 mL.

The material for such welded cans is a plate with a thickness of 0.20 mm manufactured by the so-called 2CR method, in which an annealed plate is subjected to secondary cold rolling at a reduction rate of 15% or more for the purpose of increasing strength and making it extremely thin.
The front and rear parts are made of ultra-thin 20R steel plates, which are then plated and used.

However, when a welded can manufactured by the 2CR method is subjected to flange processing for attaching a can lid to the can body after the side seam, cracks may occur in the vicinity of the welded portion due to the flange processing.

(Problem to be solved by the invention) This is caused by poor welding, poor workability of the steel plate,
These include inclusions in the steel plate, hardening of the weld, and softening of the heat-affected zone, but among these, flange cracking is the most common cause due to softening of the heat-affected zone due to welding, and is the biggest problem in processing flanges of welded cans. It becomes.

It is thought that this softening of the heat-affected zone occurs when the processing strain of the secondary cold rolling, which gives the material high strength, disappears due to the heating during welding. It has been found that machining distortion occurs when it is concentrated.

Normally, this tendency for flange cracking to occur is 2CR due to box annealing.
2CR by continuous annealing, which tends to accumulate strain due to cold rolling after annealing because the grain size is smaller than that of the material and the amount of solid solute C is large.
Significant in wood.

For this reason, the scope of application of continuous annealing materials, which have superior quality uniformity and productivity, is severely restricted, and the appearance of continuously annealed 2CR materials for welded cans with excellent flangeability is currently eagerly awaited by related industries. be.

On the other hand, Japanese Patent Application Laid-Open No. 58-164 has developed a technique for improving flange workability in continuous annealing.
A method of coarsening the crystal grains of the material to improve flange workability is disclosed in Japanese Patent Application Laid-Open No. 61-3415.
No. 9 and other publications have already proposed a method of manufacturing a steel plate with excellent flange workability by making cementite finer.

However, among the above-mentioned technologies, the former manufacturing method involves coarsening the annealed plate before the secondary cold rolling, so there are difficulties in manufacturing control in ensuring uniformity of quality, which is a characteristic of continuously annealed materials. Furthermore, in order to harden the material, it is necessary to increase the secondary cold rolling rate after annealing, which lowers the recrystallization temperature of the material during welding, significantly softening the heat affected zone, and reducing the effect of improving flange cracking. have.

However, the latter manufacturing method involves increasing the amount of C, rapidly cooling after hot rolling,
By rolling at a low temperature of 400 to 600°C, cementite is finely dispersed to obtain a softening suppressing effect, but finely dispersing cementite also works to suppress crystal grain growth due to cementite particles, and furthermore, by increasing the amount of cementite during welding. scattering (
It has drawbacks such as less occurrence of sputtering and local softening of the weld heat-affected zone due to spatter, which reduces flange workability.

The object of the present invention is to overcome the above-mentioned difficulties and to provide a 2CR ultra-thin steel sheet for welded cans by continuous annealing, which has poor flange workability after cans are joined by bath welding.

(Means for solving problems) The gist of the present invention is the weight factor, c;

03-0.08%, Si; 0.03% or less, Mn;
0.05-0.6%, P; 0.06% or less, u;
O: 02-0.1%.

A steel containing N; o, ox% or less, with the balance consisting of iron and other unavoidable elements, is hot-rolled at a hot finish rolling temperature of A8 or higher, and then rolled at a temperature of 630 to 710' (: Alternatively, after soaking and holding, descaling, cold rolling, and continuous annealing are performed at 300 to 450°C.
The material is subjected to over-aging treatment for 30 seconds or more, and then subjected to secondary cold rolling to a rolling strength of 15 or more.The material is then used as a plating material to produce 2CR material for welded cans, which has excellent flange workability.

In addition, the present invention heats a steel slab whose composition is limited to a relatively low C in a temperature range of 950 to 1150°C prior to hot rolling.
We aim to improve the ductility of the material by setting the hot finishing hot rolling temperature to A8 point or higher, and by regulating the winding temperature to 630°C or higher and 710°C, we promote appropriate grain growth of hot-rolled sheet crystal grains. It also suppresses non-uniform cold rolling accumulated strain due to uniform dispersion of carbides in the hot rolled sheet, and enlarges crystal grains after annealing to prevent softening during welding.

Furthermore, by performing overaging treatment at 300-450℃ for 30 seconds or more after annealing, solute carbon is reduced, cold rolling accumulated strain due to secondary cold rolling is reduced, softening during welding is suppressed, and flange workability is improved. The aim is to obtain an ultra-thin steel sheet with excellent properties.

(effect) The present invention will be explained in detail below.

First, the lower limit of the C content is set to o, o3% because below this, there is a region where solid solution C in the steel increases, and furthermore, the strength of an ultra-thin steel plate cannot be obtained.

In addition, the upper limit of the C content was set at 0.08% because if it exceeds this value, the suppressing effect of grain growth by cementite particles becomes large, and the crystal grains of the material (steel plate) do not become large, and cracks may occur during flange processing. This is because sputtering can easily occur and sputtering during welding is likely to occur due to an increase in the amount of C.

The upper limit of the S1 content was set at 0.03% because as the S1 content increases, flange workability deteriorates due to hardening of the material due to solid solution strengthening, and the plating adhesion as a plating original plate deteriorates due to surface enrichment of Si. It's for a reason.

The reason why the amount of Mn is limited to 0.05 to 6% is because if the amount of Mn is reduced, it will become softer and the flange workability will be improved, but the strength as a material for cans will not be obtained, and conversely, if the amount of Mn is increased, the cost will increase. This is because it is disadvantageous in terms of performance and also causes cracks during flange processing.

The reason why the amount of P was set to 0.06% or less is because P is a solid solution strengthening element and is added in the required amount according to the degree of hardening, but adding more than necessary will have a negative effect on flange workability and will also reduce the corrosion resistance of the material. Since this causes deterioration, the upper limit was set at 0.06%.

The amount of M is limited to 0.02 to 0.1%, and the lower limit is set to 0.02, which is the amount necessary to fix N, and the upper limit is set to 0.02%.
．． The reason why it is set at 1% is because adding more than that will lead to excess M.
Furthermore, the excess M with fixed N deteriorates the flange workability, and the surface enrichment of M still causes deterioration of the corrosion resistance of the material, so the upper limit was set at 0.1%.

N is necessary to precipitate as AgN and add the effect of increasing the strength by precipitation strengthening, but if too much is contained, the flange workability will be deteriorated, so the content should be 0.01 inch or less.

Prior to hot rolling, the steel billet is heated to a reheating temperature in the range of 950 to 1150°C, if necessary. This is to suppress the re-melting of AIN precipitated during the manufacturing process of steel slabs, and to maintain AAN in a relatively large form so as not to inhibit grain growth during the hot rolling process or subsequent processes. The upper limit for achieving this is 1150°C. On the other hand, if the temperature is too low, hot rolling cannot be performed smoothly, so the lower limit is set at 950°C. When this steel billet is heated, it becomes softer due to grain growth, which increases the degree of freedom in the secondary cold rolling rate, making it possible to efficiently ensure the strength of a 2CR material. Furthermore, by precipitating and fixing M in the form of AIN, it is expected that surface enrichment of M during the manufacturing process will be suppressed and the corrosion resistance of the material will be improved.

The purpose of limiting the hot finishing rolling temperature to the A3 point or higher is to improve the ductility of the material, but if the finishing temperature is set to the A3 point or lower, rolling will occur in the α+γ region or α region and the structure of the hot rolled steel sheet will change. This is done in consideration of the fact that the grains become coarse and the material softens significantly, so the secondary cold rolling rate must be set high, which lowers the softening temperature during welding and deteriorates flange workability.

Next, the hot rolling temperature was limited to 630 to 710'C, because moderate grain growth is preferable for the flange workability of the material, so the purpose is to promote the growth of crystal grains in the hot rolled sheet and to promote the precipitation of AIN. It's for a reason.

The lower limit of the winding temperature is set to 630° C. in order to precipitate the solid solution N remaining in the steel slab and to promote grain growth to coarsen the grains.

In addition, the upper limit was set at 710°C because when the temperature exceeds 710°C, crystal grains become coarser, but at the same time, carbides aggregate and form into lumps, which deteriorates the corrosion resistance and flange workability of the material and also reduces the longitudinal strength of the steel sheet. This is done in consideration of the fact that the variation in the material in the direction and width direction is large, which is undesirable in practice as a material for welded cans, which requires uniformity of the product.

After hot rolling, descaling, cold rolling, and continuous annealing are performed.

Although the continuous annealing temperature does not need to be specified, it is preferable that the temperature is higher because the crystal grains become larger. Further, the longer the annealing time, the larger the crystal grains become, which is preferable.

By performing overaging treatment after continuous annealing, solid solution C in the steel is reduced and flange workability is significantly improved.

The reason why the overaging treatment temperature was limited to 300 to 450°C was 3.
At temperatures below 00°C, it takes an extremely long time to extract enough supersaturated solid solution C, making it impractical in terms of efficiency. At temperatures above 450°C, it takes time to heat up and cool down, and furthermore, at that temperature, C This is because the solid solubility limit of C is large, and a large amount of solid solute C remains even after overaging treatment, which is undesirable in that flange workability deteriorates.

Within this temperature range, the treatment time required to precipitate solid solution C in the steel may be 30 seconds or more.

The reason why the lower limit of the secondary cold rolling ratio of the present invention is limited to 15% is as follows.
Continuously annealed materials with solid solution C at low rolling reductions of less than 15 inches will result in materials that retain some aging characteristics, and during high-speed flange forming processing after welding, aging will cause Lüders bands ( This is because there is a phenomenon in which only the heat-affected zone (and heat-affected zone) deforms significantly, resulting in flange cracking.

Using the 2CR high-strength ultra-thin steel plate thus obtained as a raw material, a 2CR material for welded cans with excellent flange workability can be manufactured by selecting surface plating according to the purpose.

Since the manufacturing method of the present invention exhibits similar effects in a wide variety of platings, the components and properties of the plating layer are not particularly limited.

Examples will be described below.

N11l-6 are examples of the present invention, and Nos. 7-12 are comparative examples.

After continuous casting with the ingredients shown in Table 1, hot rolling was performed at 23 to 3.
Hot rolling was carried out to 0fi, followed by ordinary pickling treatment and rolling to 0.207% - 0.243mm in a tandem cold rolling mill. After annealing this steel plate in a continuous annealing furnace,
Subsequently, over-aging treatment was performed (however, No. 10 to 12 were not over-aging treated), and tin plating was performed.

Table 1 shows the hardness and SBi value of the plated plate.

After slitting this plated steel plate, use a Sudronik welding machine (
ABM-270 machine) was used to form the can body, and a disc flancher was used to perform flange processing.

Table 1 shows the number of flange cracks in the total manufacturing number for each level as a percentage of the flange crack occurrence rate.

Legend, welding conditions Welding machine: ABM-270 Wire speed: 30 m/min Can making speed: 270 cans/min Overlap width 20, 5-way flange processing Disk square gear used This invention
Comparative material ○ (2G1 day 9 Steel plates of N11l~6 manufactured according to the method of the present invention in Table 1 had no flange cracks, and as compared to steel plates of No. 7~12 which were outside the scope of the present invention as in comparison) There is a clear difference.

Table 1 shows that the 2CR material (copper plate) for welded cans produced by the method of the present invention is extremely excellent in terms of flange workability, which not only improves the yield of steel plates but also
The ability to reduce the thickness of the steel plate greatly contributes to resource and energy conservation, and the economic value resulting from the present invention is extremely large.

(Effects of the Invention) According to the present invention, it is not only possible to manufacture a 2CR material for welded cans made of an ultra-thin steel plate with excellent flanging properties, but also to produce a high-strength ultra-thin steel plate that can reduce the thickness of the steel plate. By changing the contents of C, Mn, and H within the scope of the present invention, and by changing the secondary cold rolling rate, it is possible to flange steel sheets with different strength levels within the required strength range for can stock. It can be easily manufactured without impairing processability.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the secondary cold rolling rate of an ultra-thin steel plate of 0.17 to 0.18 m and the incidence of flange cracking caused by a disk flancher after forming the can body. Figure 1 2 Pig

Claims (2)

[Claims] (1) In weight%, [C]: 0.03 to 0.08% [Mn
]: 0.05-0.6% [Si]: 0.03% or less [P]: 0.06% or less [Al]: 0.02-0.1% [N]: 0.01% or less balance Steel consisting of iron and inevitable impurity elements is hot rolled, hot finish rolled at a temperature of A_3 or higher, then rolled or soaked at a temperature of 630 to 710°C, followed by descaling and cold rolling. The material is then annealed by continuous annealing, followed by over-aging treatment at 300-450°C for 30 seconds or more, and then subjected to secondary cold rolling of 15% or more to provide excellent flange formability through continuous annealing to make it into a plating material. Method for manufacturing 2CR material for welded cans. (2) In weight%, [C]: 0.03 to 0.08% [Mn
]: 0.05-0.6% [Si]: 0.03% or less [P]: 0.06% or less [Al]: 0.02-0.1% [N]: 0.01% or less balance Steel consisting of iron and unavoidable impurity elements from 950 to
Heating in the temperature range of 1150℃, hot finish rolling A_3
After rolling or soaking at a temperature of 630 to 710°C, descaling and cold rolling are performed and annealed by continuous annealing to 300 to 450°C.
Perform overaging treatment at ℃ for 30 seconds or more, and
A method for manufacturing a 2CR material for welded cans that has excellent flange workability by continuous annealing and subsequent cold rolling to produce a material for plating.