JPH0244889B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to bright steel sheets, particularly bright steel sheets used as can materials, and a method for manufacturing the same. [Conventional technology] In general, cans are divided into food cans, general cans, and 18
Cans can be classified into cans, pails, drums, aerosol cans, etc., and can be classified into solder cans, adhesive cans, welded cans,
Divided into DI cans, squeezed cans, etc. On the other hand, structurally, they can be classified into two-piece cans and three-piece cans; broadly interpreted, the above-mentioned DI cans and squeezed cans correspond to two-piece cans, and solder cans, adhesive cans, and welded cans correspond to three-piece cans. By the way, the steel plates used for these cans include:
There are tin-plated steel sheets plated with tin and stain-free steel sheets plated with chromium, but these are cold-rolled steel sheets that are annealed, temper-rolled, and then plated with tin, chrome, etc. Manufactured by In addition, in the above-mentioned temper rolling, the roughness of the sheet surface (steel sheet surface) is adjusted, which can be roughly divided into glossy finish (hereinafter referred to as bright) and matte finish (hereinafter referred to as dull). There are two types. These are adjusted depending on whether a polished bright roll or a shot blasted or electrical discharge machined dull roll is used as the work roll for temper rolling. Generally, the surface roughness of the steel plate formed in this way is 0.05 to 0.30 μm Ra for bright and 0.8 to 2.0 μm for dull.
It is Ra. The bright steel sheet obtained as described above is plated with tin, chromium, etc. and is used as a bright plated steel sheet as a material for three-piece cans, while the dull steel sheet is plated in the same way and is used as a material for three-piece cans. It is intended for two-piece can materials as a steel plate. However, bright steel sheets and bright plated steel sheets are susceptible to scratches and crimping scratches during the above-mentioned steel sheet manufacturing process, shipping process, user's can manufacturing process, and the like. In other words, because a large number of rolls are used in the manufacturing process and can making process, and processes such as winding and unwinding are also carried out using winders and unwinders, steel sheets are subject to roll wear and tension in these machines. Scratches are likely to occur due to fluctuations, etc., and crimping scratches may occur in the winding and unwinding machines.Furthermore, the self-weight and vibration of the steel plate during transportation of wound tight coils and stacked sheets (steel plates) Crimping flaws are also likely to occur, and these flaws are particularly common in bright plated steel sheets. On the other hand, in the case of dull steel plates and dull plated steel plates, since their surface roughness is large, scratches and crimping scratches are less likely to occur, and even if they occur, they are less noticeable. Therefore, as a solution to the problems that conventional bright materials have had, there is a cold rolled steel sheet disclosed in, for example, Japanese Patent Application Laid-Open No. 55-42147.
This rolls a steel plate using a pair of dull rolls and smooth rolls (bright rolls) to finish the steel plate dull on one side and bright on many sides.This reduces the contact area between the steel plates, etc. It is said that this can prevent the occurrence of the above-mentioned flaws. [Problems to be Solved by the Invention] However, the above-mentioned cold-rolled steel sheet, which is intended to solve the drawbacks of bright materials, has several problems as described below. In other words, since there is a difference in roughness between one side and the other side, for example, in the case of a three-piece can, if the can surface is mirror-finished for printing, etc., the inside of the can becomes a matte surface, which is preferable from the viewpoint of corrosion resistance. Its use as a can material is limited. Further, when plating is applied to the cold-rolled steel sheet, the thickness of the plating film differs between the front and back surfaces due to the difference in surface area due to the difference in roughness, and the surface with the smaller thickness poses a problem in terms of corrosion resistance. Furthermore, since one side of this cold-rolled steel sheet is bright, the bright side still has the property of being prone to scratches, and therefore, in order to prevent the occurrence of scratches that are likely to occur, it is necessary to always touch the surface during the manufacturing process etc. mentioned above. This is accompanied by the complexity of having to perform process control while clearly distinguishing between the back side and the back side, and this becomes a significant impediment to productivity. The present invention was made in view of these conventional problems. After forming craters in a predetermined shape on a bright roll with a predetermined surface roughness using a high-density energy source, this invention The aim is to solve the above problems by performing temper rolling. [Means for Solving the Problems] The present invention has a smooth portion with a surface roughness Ra of 0.40 μm or less, a trapezoidal or arcuate cross-section, and a height.
It consists of many protrusions of 5 μm to 50 μm, the diameter of these protrusions is D (μm), and the interval between adjacent protrusions is Sm.
(μm), the value of Sm/D is 1≦Sm/
A bright steel plate having a surface shape such that D≦5 is obtained.Furthermore, in order to obtain this cold rolled steel plate, a cold rolled steel plate that has been cold rolled and annealed is further subjected to temper rolling to make it brighter. In a bright steel sheet manufacturing method for manufacturing steel sheets, a high-density energy source is used to regularly form a large number of craters on the surface of a work roll that has been polished to a bright finish with a surface roughness Ra of 0.35 μm or less. In this case, when the depth of the crater is 5 μm to 50 μm, the interval between adjacent craters is Sm (μm), and the diameter of each crater is D (μm), the value of Sm/D is 1.
A method for producing a bright steel plate, in which a hole is punched so that ≦Sm/D≦5, and then the work roll is used to perform temper rolling on a cold rolled steel plate after cold rolling and annealing. It is. [Operation] A cold-rolled steel plate is rolled using a bright roll whose surface is regularly perforated with many craters using a high-density energy source such as a laser beam.
A bright steel plate is obtained which has projections corresponding to the craters that are regularly arranged and have a height within a predetermined range. Therefore, since the surface of this bright steel plate has many flat parts and the above-mentioned protrusions are regularly arranged, it is possible to obtain a gloss level equivalent to that of a conventional bright steel plate. Furthermore, as mentioned above, since projections are formed on both the front and back surfaces of the steel plate, it is possible to prevent scratches, crimping scratches, etc. from occurring during the manufacturing process. [Example] The present invention will be described below with reference to the drawings. 1 to 9 are drawings for explaining embodiments of the present invention. First, a method for forming the surface roughness of a temper rolling work roll for manufacturing a bright steel plate according to the present invention will be described. A high-density energy source such as a laser beam, plasma beam, or electron beam is irradiated onto the work roll surface, which has been polished to a smooth surface, in a pulsed manner while rotating the roll at a constant speed. The surface of the roll is perforated so that it appears to melt into regular, continuous dots. 1st, 2nd
The figures are an enlarged sectional view and an enlarged plan view of the roll surface melted into dots, respectively. In the figure 1
are craters formed by melting dots on the surface of the roll 3, and around the crater 1, the molten roll base metal rises above the roll surface to form a flange 2. Further, the portion between the flanges 2, 2 of adjacent craters 1, 1 is a smooth portion 4 that remains the polished surface of the original roll 3. Here, the distance between adjacent craters 1 can be determined by controlling the frequency of the laser pulse in relation to the rotational speed of the roll 3 in the rotational direction of the roll 3, and by controlling the frequency of the laser pulse in relation to the rotational speed of the roll 3 in the axial direction of the roll 3. The laser irradiation position can be adjusted by controlling the pitch of moving the laser irradiation position in the axial direction of the roll 3 every time the roll 3 rotates once. Furthermore, the size of the crater 1 can be controlled by changing the laser pulse irradiation time, laser output, etc. The operation when a pair of upper and lower work rolls thus formed are rolled into a temper rolling mill to perform temper rolling on a cold rolled steel sheet will be described below. Microscopically enlarging the behavior of the steel plate surface during this temper rolling process, as shown in FIG. This causes local plastic flow of the material near the surface of the steel plate 5, which is softer than the material of the roll 3, and the metal of the steel plate 5 flows into the crater 1 of the roll 3 as shown by the arrow. It flows in and forms a rough surface. That is, the metal that has flowed into the crater 1 becomes the peak 6 on the surface of the steel plate 5, and the smooth surface of the roll 3 directly becomes the smooth part 7 on the surface of the steel plate 5, so that the peak 6 becomes higher than this smooth part 7. Therefore, as shown in the cross section of FIG. 4, the microscopic shape on the surface of the steel plate 5 after temper rolling consists of a peak 8 having a peak 6 and a continuation formed to surround the peak 8. By a groove-shaped valley 9 and a smooth part 7 formed between adjacent peaks 8 and outside the valley 9, higher than the bottom of the valley 9 and lower than the peak 6. It will be configured. In the above description, the continuous groove-shaped valley portion 9 is annular, but the present invention is not limited to this annular shape.
It may be formed by two or more circular arcs. Furthermore, the flange 2, that is, the valley portion 9 of the steel plate 5 may be completely eliminated by increasing the irradiation energy of the pulse beam or increasing the flow rate of the assist gas to scatter the metal of the roll base material. Further, in the illustrated example, the cross-sectional shape of the peaks 8 of the steel plate 5 is trapezoidal, but the rolling load during temper rolling may be increased to make the peaks 8 even higher to form an arcuate shape. In any case, in the present invention, the peak portion 8 including the valley portion 9 is referred to as a protrusion, and the crater 1 including the flange 2 is referred to as a crater. Next, the reason for the numerical limitation regarding the surface roughness will be explained. As already mentioned in the section on means for solving problems, the reason why the surface roughness of the smooth part 4 of the roll 3 is set to 0.35 μmRa or less and that of the smooth part 7 of the steel plate 5 is set to 0.40 μmRa or less is because the plate surface (Steel plate surface) If the roughness exceeds 0.40μmRa, it will not be possible to obtain the gloss required for a bright steel plate when considering the protrusions 11 (Fig. 4) as described later, and The roll surface roughness that can obtain the upper limit is
This is because it is 0.35 μm Ra. On the other hand, there is no specific lower limit for the roll surface roughness, but the surface roughness Ra that can be achieved with current roll polishing technology is
0.02 μm, and the surface roughness of the smooth portion 7 of the steel plate 5 obtained by temper rolling is 0.02 μm.
It is 0.05μmRa. Further, the height of the protrusion 11 of the steel plate 5 and the depth of the crater 1 of the roll 3 are the height and depth from the smooth parts 7 and 4, respectively, and these are
It shall be within the range of 50μm. Now, as shown in Fig. 5, if the outer diameter of the flange 2 formed on the surface of the roll 3 is D (μm) and the depth of the crater 1 is H (μm), then the diameter D when drilling with the laser pulse beam is The relationship between depth H and depth H is shown in FIG. That is, if the diameter D is increased, the depth H also increases, but especially when the diameter D exceeds 300 μm, the depth H increases rapidly. Therefore, if the diameter D exceeds 300 μm, the height of the protrusions will become unnecessarily large even under normal roll rolling load, although this will depend on the transfer rate during skin pass rolling, and this will cause the protrusions to become unnecessarily large if the rolls wear out. This means that the roll consumption rate deteriorates because the polishing allowance increases during roll reprocessing. Further, as the ratio of the depth H to the diameter D increases, the shape of the protrusion becomes more acute, which means that scratches are more likely to occur due to contact between the steel plates. From the above, the upper limit of the protrusion height H is set to 50 μm, which corresponds to the diameter of 300 μm shown in FIG. On the other hand, to reduce the depth of the crater or the height of the protrusion, it is done by shortening the irradiation time of the laser pulse or lowering the laser output, but the drilling is performed with the depth H stable at around 5 μm. Processing is extremely difficult in terms of control accuracy of irradiation time or laser output, and at the same time, if the height of the protrusions is less than 5 μm, even if the number of protrusions per unit area is increased, scratches and crimping defects will not occur. Since it is not possible to completely prevent this, the lower limit has been set at 5 μm. In addition, in FIG. 4, the diameter D (μm) of the protrusion 11
and Sm, which is the average center distance between adjacent protrusions.
(μm), if Sm<D, the protrusions will interfere with each other and the surface of the steel plate will become uneven, which is not only unfavorable in terms of gloss but also problematic in terms of roll processing. As the roll is rotating during processing, it is necessary to irradiate the laser pulse beam at a pulse frequency that interferes with the crater 1 or flange 2 that was previously formed, resulting in a surface shape with stable and regular craters. It will be difficult to obtain. From the above, it is assumed that Sm≧D. Here, the gloss required for the bright steel plate largely depends on the smooth portion 7 in the bright steel plate according to the present invention. However, the protrusions 11 according to the present invention are not formed by shot blasting or electrical discharge machining, but by a roll processed by irradiating a high-density energy source as a pulsed beam, so that the peaks of the protrusions 11 The portions are substantially flat, and there is almost no difference in shape between the protrusions, and they are regularly arranged, so there is little adverse effect on gloss. Figure 7 shows Sm=D, which is the most disadvantageous in terms of glossiness.
This figure shows the results of an investigation into the relationship between the surface roughness Ra of the smooth part and the glossiness in the case of . In other words, the surface roughness Ra after polishing is
A steel plate obtained by performing perforation using laser pulses on four types of rolls of 0.05, 0.18, 0.35, and 0.40 μm so that the crater depth is 25 μm and Sm/D = 1, and then temper-rolling with these rolls. This figure shows the relationship between the roughness of the smooth part (μmRa) and the glossiness GS (20°) (JIS Z8741). This shows that if the surface roughness Ra of the smooth portion of the steel plate is 0.40 μm or less, a bright feeling is obtained, and if it is more than that, the glossiness cannot be measured and a bright feeling cannot be obtained.
Further, as the value of Sm/D increases, the gloss increases, but if it becomes too large, the surface shape approaches that of a conventional bright steel plate, and scratches and crimping scratches will occur. According to the knowledge obtained from such experiments by the present inventors, this upper limit was Sm/D=5. From the above, Sm/D
The value of Sm/D satisfies 1≦Sm/D≦5. Next, another embodiment carried out by the inventors will be described. [First Example] After cold rolling and continuous annealing, a low carbon steel plate was subsequently subjected to temper rolling using a two-stand temper rolling mill. Surface roughness of work roll for No. 1 stand
A shot dull roll with a diameter of 1.2 μm Ra was used, and the surface roughness of the work roll for the No. 2 stand after polishing was set to 0.07 μm Ra, and then perforation was performed using a laser pulse to reduce the depth of the crater.
Rolls with a diameter of 15 μm and three levels of Sm/D of 5, 2, and 1 were used, and as a comparative example, rolls with a surface roughness of
Three levels of bright rolls of 0.07, 0.16, and 0.35 μm Ra were used. As a result, three types of bright steel plates according to the present invention having a thickness of 0.22 mm and conventional bright steel plates as comparison materials were obtained by performing temper rolling with an elongation rate of 1.2%. The surface roughness Ra and glossiness GS (20°) of the bright steel plate thus obtained (JIS
Z 8741) is shown in Figure 8. In other words, although the bright steel sheet according to the present invention has a rougher surface including protrusions than the conventional bright steel sheet, the brightness is at the same level as the comparative material according to each level, and the gloss at each level is There was little variation in degree. In this example, a shot dull roll was used for the No. 1 stand, but a dull roll machined by other methods such as electric discharge machining may be used, or a polished bright roll may be used. [Second example] Each bright steel plate obtained in the first example was edge-cut on a coil preparation line, then tinned with #25 (2.8 g/m ² ) on an electric tinning line, and then passed through a shearing line. It was made into a cut plate. Cut plates with defects selected by the automatic flaw detection device of this shearing line were further visually inspected to distinguish the types of defects, and the incidence of scratches and crimp defects was investigated. The results are shown in FIG. As is clear from the figure, in the comparative materials, the smaller the surface roughness Ra, the higher the defect occurrence rate. on the other hand,
In this example, the same tendency as the comparative material was observed, but the defect occurrence rate was about 1/10 or less. [Third Example] Bright steel plates according to the present invention having protrusion heights of 3 μm, 5 μm, and 15 μm were manufactured by a method similar to the above-mentioned [First Example]. At this time, three types of Sm/D, 6, 5, and 2, were prepared for each protrusion height. Note that the protrusion height can also be lowered by reducing the rolling load on the No. 2 stand of the temper rolling mill.
Although the protrusion height can also be controlled by a method in which the No. 2 stand rolling load is kept constant and three types of rolls with different crater depths are used, the former method was used in this example. Furthermore, after passing through the same process as [2nd example],
The number of scratches and crimping scratches on each level of laser-brightened steel plate was investigated. The results are shown in the table below. From this table, if the protrusion height of the steel plate is 5 μm or more, S
It can be seen that when m/D is 5 or less, no scratches or crimping scratches occur.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a bright steel plate in which scratches and crimp defects are less likely to occur, and this can greatly contribute to improving the yield of products. Furthermore, the bright steel plate according to the present invention has less variation in gloss than conventional bright steel plates, and has advantages such as being advantageous in terms of quality assurance.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a roll according to the present invention, FIG. 2 is a top view of a portion corresponding to FIG. 5 is an enlarged sectional view of a crater, FIG. 6 is a graph showing the relationship between crater diameter and depth, and FIG. Figure 8 is a graph showing the relationship between brightness and glossiness. Figure 8 is a graph comparing the surface roughness and glossiness of the bright steel plate in another embodiment [Example 1] and the conventional example. It is a graph comparing the flaw occurrence rate of the Example and the conventional example of a bright steel plate in which tin plating was applied in [Example 2]. 1... Crater, 3... Work roll, 4,7
... Smooth part, 5 ... Cold rolled steel plate, 8, 11 ... Protrusion.

Claims (1)

[Claims] 1. Consists of a smooth portion with a surface roughness Ra of 0.40 μm or less and a large number of protrusions having a trapezoidal or arcuate cross-sectional shape and a height of 5 μm to 50 μm, and the diameter of these protrusions is defined as D. (μm), and the interval between adjacent protrusions is Sm (μm).
m), the value of Sm/D is 1≦Sm/D≦
5. A bright steel sheet characterized by having a surface shape as shown in FIG. 2. In the method for manufacturing bright steel sheets, in which a bright steel sheet is manufactured by further temper rolling a cold-rolled and annealed cold-rolled steel sheet, a bright finish with a surface roughness Ra of 0.35 μm or less is applied by polishing. When a large number of craters are regularly formed on the surface of a work roll using a high-density energy source, the depth of the craters is 5 μm to 50 μm, and the interval between adjacent craters is Sm (μm), and the distance between each crater is When the diameter is D (μm), the value of Sm/D is 1≦S
A method for producing a bright steel plate, which comprises performing a perforation process such that m/D≦5, and then using this work roll to subject the cold rolled steel plate after cold rolling and annealing to skin pass rolling.