JPH10280116A - Surface-treated steel sheet excellent in rusting-resistance edge face, its production and cutting of surface-treated mother steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface-treated steel sheet excellent in rusting resistance in the cutting edge face by regulating the relation between the ratio of the shearing face occupies in the cutting face and the coating weight of Zn to a specified range. SOLUTION: The shape of the cutting edge face is allowed to satisfy the inequality of t<2> /(M.RS)<=0.2. In the inequality, (t) denotes the sheet thickness (mm), M denotes the coating weight (g/m<2> ) of Zn per side, and RS denotes the ratio of the shearing face (= the thickness of the shearing face/sheet thickness). Or, at the time of producing a surface-treated steel sheet applied with galvanizing, it is subjected to galvanizing in such a manner that the relations among the ratio of the shearing face to be occupied in the cutting edge face in the case of cut by a pair of upper and lower tools, the sheet thickness of the steel sheet and the coating weight of Zn satisfy the above inequality and is subjected to cutting. In this way, rust in the cutting face generated from a position in which the separating from mainly in the edge face is the broken face and free from the presence of galvanizing can universally be suppressed. Furthermore, the ratio of the shearing face is preferably regulated to 0.5 to 0.9 and the coating weight of Zn per side to >=5 g/m<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc-plated surface-treated steel sheet to be used as a member of household appliances, building materials, office equipment, etc., and more particularly to a surface having excellent rust resistance of a cut end face by a shearing machine. The present invention relates to a treated steel sheet, a method for producing the same, and a method for cutting a surface-treated mother steel sheet.

[0002]

2. Description of the Related Art Zinc-based plating, that is, in addition to Zn alone, Zn-Ni, Zn-Fe, Zn-Al, Zn-C
r, Zn-Ni-Co, Zn-Al-Cr and other surface-treated steel sheets that have been subjected to various types of plating including binary alloys and multi-element alloys have excellent corrosion resistance.
It is widely used as a component of products such as office equipment. In the production process, the components of these products are sheared and punched by a shearing machine equipped with a pair of upper and lower tools on a zinc-plated surface-treated mother steel sheet (the steel sheet before cutting is used as the mother steel sheet). It is manufactured by performing some kind of cutting processing such as (blanking), drilling (punching), and trimming (trimming), and forming the surface-treated steel sheet obtained by the cutting into a predetermined shape as necessary.

[0003] Conventionally, once these surface-treated steel sheets are used in products, they are generally discarded by users as oversized trash, or dismantled and scrapped. On the other hand, recently, due to the problem of waste disposal sites in local governments that have reached their limits,
From the standpoint of conserving resources and energy, and protecting the global environment, we not only recover and reuse product parts as iron resources, but also recover a part of them in their original form to increase added value. Motivation to use is increasing. Under such circumstances, in the near future, it is expected that manufacturers themselves will recover sold products as they are, or collect and reuse some of the components.

[0004]

However, in various products using conventional surface-treated steel sheets, red rust is gradually generated on the cut end surfaces during use, which not only deteriorates the appearance, but also causes the above-described re-use. It was not at all suitable for use. Furthermore, for example, in the case of household electrical appliances, if end faces are rusted during use or collected, electrical short-circuiting due to lack of rust or the like may be a concern.

[0005] The problem of rust generation on the cut end face is particularly caused by PCM (Precoated Meta) as a surface-treated steel sheet.
l) Frequently observed when steel plates were used. Where P
CM steel sheet is a coating that is usually applied by a processing maker and is pre-coated in the state of a mother plate. For example, a chemical conversion treatment such as a phosphate treatment or a chromate treatment is performed on zinc-based plating. , And those coated or laminated with vinyl chloride or polyester. Such a phenomenon of rust occurs because the PCM steel sheet is cut after coating, and the base iron is exposed at the processed end face, and most of the exposed portions are not coated.
Therefore, such a problem of rust generation on the cut end face is caused not only in a state of plating, but also in a case where a chemical conversion treatment such as chromic acid treatment is performed after plating or in a case where a coating is applied to a steel sheet surface like PCM. When the end face of the steel sheet is exposed, it is also concerned.

Therefore, when the cutting process is performed after the plating, after the chemical conversion treatment on the plating layer, or after the coating treatment on the chemical conversion treatment layer, even when the cutting process is performed, that is, after the cutting process, a special treatment such as painting is performed. If a material that does not generate rust on the cut end surface is developed even without performing
It is expected that product members can be reused and product cost can be reduced as described above.

Accordingly, an object of the present invention is to provide a surface-treated steel sheet having excellent rust resistance at the cut end face in view of the above-mentioned problems of the prior art in a zinc-plated surface-treated steel sheet. And a method of manufacturing the same and a method of cutting a surface-treated mother steel sheet.

[0008]

As a result of repeated experiments and studies to achieve the above-mentioned object, the inventors of the present invention have found that the generation of rust on the cut end surface is caused by the ratio of the shear surface occupied by the cut surface, and the Zn basis weight. It was found that the amount was greatly affected by the amount. Then, by controlling the relationship between them within a certain range, it was concluded that rust resistance at the end face could be significantly improved as compared with the conventional surface-treated steel sheet, and the present invention was completed. Was. The summary structure is as follows.

(1) The shape of the cut end surface is as follows: t ² / (M · R _s ) ≦ 0.2, where t: plate thickness (mm), M: weight per unit area of Zn (g / m ² ), R _s : a surface-treated steel sheet excellent in rust resistance of end faces, characterized by satisfying a shear surface ratio (= shear surface thickness / sheet thickness).

(2) In the production of a zinc-plated surface-treated steel sheet, the ratio of the shearing surface to be cut to the cut end face when cutting with a pair of upper and lower tools, the thickness of the steel sheet, and the Z
n basis weight relationship, the following ^{formula; t 2 / (M · R} S) ≦ 0.2 , however, t: plate thickness (mm), M: Zn basis weight per surface ^{(g / m 2), R} S : A method for producing a surface-treated steel sheet having excellent rust resistance at the end face, wherein the steel sheet is galvanized so as to satisfy a shear surface ratio (= shear surface thickness / sheet thickness) and cut.

(3) When cutting a zinc-plated surface-treated mother steel sheet with a pair of upper and lower tools, the ratio of the shearing surface to be cut to the cut end face is determined by the following formula according to the thickness of the steel sheet and the basis weight of Zn: t ² / (M · R _s ) ≦ 0.2, where t: plate thickness (mm), M: weight per area of Zn (g / m ² ), R _s : shear surface ratio (= shear surface thickness / A method of cutting a surface-treated mother steel sheet having excellent rust resistance at an end face, wherein a clearance between the tools is adjusted so as to satisfy a sheet thickness).

(4) In the above (1), the shear surface ratio is 0.5
0.9, at least one condition is satisfied surface treated steel sheet of Zn basis weight 5 g / m ² or more per side.

(5) In the above (2), the shear surface ratio is 0.5
0.9 The method of at least one condition is satisfied surface treated steel sheet of Zn basis weight 5 g / m ² or more per side.

(6) In the above (3), the shear surface ratio is 0.5
0.9, at least one condition is satisfied surface treatment base steel cutting method of the Zn basis weight 5 g / m ² or more per side. The surface-treated steel sheet in each of the above inventions includes:
It also includes those that have been subjected to bending or the like.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors carried out experiments in which the plate thickness, cutting conditions, plating conditions, etc. were changed in various ranges, and the state of rust generation on the cut end face and the separation mode (fracture surface or shear surface) And FIG. 1), and the relationship with the basis weight of Zn and the like were investigated in detail. As a result, it was found that the rust on the cut end face mainly occurred from the position where the separation style of the end face was the fractured surface, and that the rust on the end face decreased as the plate thickness became smaller. It was also found that the rust on the cut end surface was less likely to occur as the zinc basis weight increased, even with the same plate thickness and the same separation mode.
Further, the relationship between these factors is expressed by the following formula: t ² / (M · R _S ) ≦ 0.2, where t: plate thickness (mm), M: weight per area of Zn (g / m ² ), R _S : It has been confirmed that this rust can be universally suppressed by controlling so as to be within a certain range represented by a shear surface ratio (= shear surface thickness / plate thickness). Here, the Zn basis weight is a value converted into metallic Zn, and therefore, in the case of alloy plating, it means a basis weight of only Zn in the alloy. The definition of the shear surface ratio is shown in FIG.

It is believed that the basis for the above relational expression is qualitatively explained as follows. If the separation mode at the time of cutting is a fractured surface, zinc plating does not exist, and if water due to condensation or the like adheres to the cut end surface, a corrosion reaction starts and red rust is generated. On the other hand, Zn which is in the plating phase is brought to the shearing surface, and zinc is present on this surface to bring about a sacrificial anticorrosion action, so that red rust does not occur. However, in this case, the effect of sacrificial corrosion protection on the fractured surface differs depending on the amount of Zn present in the sheared surface, and the greater the amount, the greater the sacrificial corrosion protection effect. In addition, when the plate thickness is increased, the proportion of the fractured surface increases, the distance from the tip position of the zinc attachment portion in the sheared surface increases, and the sacrificial corrosion prevention effect is hardly achieved.

As described above, according to the present invention, by controlling the basis weight of zinc-based plating and the mode of separation at the time of cutting so that the value calculated by the above equation becomes 0.2 or less, the cut end face A surface-treated steel sheet having excellent rust resistance can be provided. In addition, as a suitable condition of the basis weight and the shear surface ratio, the above expression is satisfied, and the shear surface ratio is in the range of 0.5 to 0.9, more preferably 0.5 to 0.9, per one surface. Z
The n basis weight is preferably 5 g / m ² or more. By satisfying at least one of these conditions, rust resistance is further improved.

The above-mentioned control of the shearing surface ratio is most easily performed by the clearance between the upper and lower tools in the shearing machine. It is also possible to change the processing method such as shaving. FIG. 2 shows an example in which the shear area ratio is adjusted by the clearance. FIG.
Is a low carbon steel sheet (C: 0.03 wt%, Si: 0.02 wt%, Mn: 0.
2 wt%, P: 0.02 wt%, S: 0.01 wt%) and 20 g / m
^{2 This} is an investigation of the effect on the shear surface ratio of a (single-sided) pure zinc-plated double-sided electroplated surface treated base steel plate with varying clearances between the upper and lower tools. As shown in this figure, the shear surface ratio can be controlled by the clearance between the upper and lower tools. FIG. 2 also shows that the shear surface ratio is greatly affected by the plate thickness.

The zinc-based plating of the mother plate applied to the present invention may be performed by any method such as hot-dip plating, electroplating, and vapor deposition plating. Of course, there is no particular limitation as long as it is a Zn-based material such as a binary alloy plating or a multi-component alloy plating.

Further, the plating original plate to be plated is also:
The present invention can be applied without any particular limitation, but from the viewpoint of reducing burrs during shearing, a low-carbon steel sheet is desirable, and the component composition is C: 0.
04 wt% or less, Si: 0.02 wt% or less, Mn: 0.3 wt% or less,
P: 0.03 wt% or less is preferable.

[0021]

[Example] With a thickness of 1.0 to 2.0 mm, C: 0.02 to 0.05
wt%, Si: 0.01 to 0.02 wt%, Mn: 0.15 to 0.30 wt%, P:
A low carbon steel sheet of 0.01 to 0.03 wt% has a basis weight of 10 to 60 g /
m ^Two(One side) electrogalvanized. Next,
Mate treatment to a chromate solution with a Cr reduction ratio of 40%
Phase silica with SiO_Two/ Cr = 4 added
Is 40 mg / m in terms of metal Cr^TwoApply and bake at 250 ° C
It was done in a crisp manner. The surface treatment obtained in this way
Using a shearing machine that can change the clearance,
By changing the shear ratio, the equation t^Two/ (MR_S) Value
Was changed within a certain range.

The cut end face was visually observed to examine the separation mode, and the cut end face was examined for rust resistance. The rust resistance was evaluated by using a sample of the cut surface-treated steel sheet for 20 days.
While maintaining the temperature at 0 ° C., the sample was placed in a thermo-hygrostat at a temperature of 35 ° C. and a humidity of 80% to cause dew condensation, and stored for 1 day. With this treatment as one cycle, the number of cycles until the red rust occurrence rate (= red rust occurrence area on the end face / total test area on the end face) reaches 5% is measured. 10 to 19 cycles were evaluated as Δ, and less than 10 cycles were evaluated as x. Table 1 shows the results of these investigations.

[0023]

[Table 1]

As is evident from the results shown in Table 1, the surface-treated steel sheets produced by cutting the surface-treated mother steel sheet according to the present invention all have a cycle number of 20 or more and have good rust resistance. You can see that it is doing. On the other hand, in the case of the comparative example, the rust resistance is poor.

[0025]

As described above, according to the present invention,
It is possible to provide a surface-treated steel sheet having excellent rust resistance at the cut end face. Thus, according to the present invention,
Whether the surface-treated mother steel sheet is in a Zn-plated state, in a state of chemical conversion treatment after plating, or in a state of coating treatment after plating-chemical conversion treatment, the rust resistance at the cut end surface is good. As a surface-treated steel sheet is obtained, there is no need to perform special treatment such as painting after cutting, not only contributing to product cost reduction, but also enabling the reuse of product members that can be realized in the future, and protecting the global environment. It is a great place to contribute to.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a shear surface ratio at a cut end surface.

FIG. 2 is a graph showing a relationship between a clearance of a cutting tool and a shear surface ratio.

Claims (6)

[Claims] 1. The shape of the cut end face is as follows: t ² / (M · R _s ) ≦ 0.2, where t: plate thickness (mm), M: weight per unit area of Zn (g / m) ² ), R _S : a surface-treated steel sheet having excellent end surface rust resistance, which satisfies a shear surface ratio (= shear surface thickness / sheet thickness). 2. In the production of a zinc-plated surface-treated steel sheet, the relationship between the ratio of the shearing surface to be cut to the cut end face when cutting with a pair of upper and lower tools, the sheet thickness of the steel sheet, and the basis weight of Zn is as follows: T ² / (M · R _s ) ≦ 0.2, where t: plate thickness (mm), M: weight per area of Zn (g / m ² ), R _s : shear surface ratio (= shear surface thickness) / Sheet thickness), and a method for producing a surface-treated steel sheet having excellent rust resistance at the end face, which is characterized by performing galvanizing treatment and cutting. 3. When cutting a zinc-plated surface-treated mother steel sheet with a pair of upper and lower tools, the ratio of the shearing surface to be cut to the cut end face is determined by the following formula according to the thickness of the steel sheet and the basis weight of Zn; ² / (M · R _s ) ≦ 0.2, where t: plate thickness (mm), M: weight per unit area of Zn (g / m ² ), R _s : shear surface ratio (= shear surface thickness / plate) Thickness), wherein the clearance between the tools is adjusted so as to satisfy thickness). 4. The method according to claim 1, wherein the shear surface ratio is 0.5 to 0.5.
0.9, a surface-treated steel sheet which satisfies at least one of the following conditions: a basis weight of Zn per side of 5 g / m ² or more. 5. The method according to claim 2, wherein the shear surface ratio is 0.5 to 0.5.
0.9, a method for producing a surface-treated steel sheet that satisfies at least one of the following conditions: a basis weight of Zn per side of 5 g / m ² or more. 6. The method according to claim 3, wherein the shear surface ratio is 0.5 to 0.5.
0.9, a method of cutting a surface-treated mother steel sheet that satisfies at least one of the following conditions: a basis weight of Zn per side of 5 g / m ² or more.