JP2927190B2 - High carbon steel sheet with excellent punching and rust prevention properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-carbon thin steel sheet suitable for punching products such as washers and leaf springs, and more particularly to a high-carbon thin steel material requiring high strength and requiring high-speed punching properties for fine parts. Related to thin steel sheets.

[0002]

2. Description of the Related Art Among parts requiring strength, such as washers and leaf springs, particularly small parts are punched at high speed because of the large number of parts manufactured. There was recognition.

In order to improve the punchability, for example, Japanese Patent Publication No. 53-9170 proposes a method of changing the metal structure of a steel sheet by heat treatment. However, in this method, a ferrite structure is obtained in the surface layer by decarburizing only the surface layer, and as a result, the hardness of the surface layer is reduced and the punching property is improved. It has no effect on the deterioration of the pull-out property. Also, the improved punching performance is a punching life of at most 100,000 times.

[0004] On the other hand, a method of improving the life of a die by applying a surface coating such as TiN to a punching die has been used. However, the cost of the coating is high, and thus the cost of the product.

As described above, conventionally, in order to improve the punching performance, studies have been made from the viewpoint of the steel structure and the coating applied to the die surface. Materials are required. However, considering such a material having high strength and excellent punching properties, it is difficult to realize high strength because it is a property that is inconsistent with punching properties from the viewpoint of steel structure. is there. On the other hand, from the viewpoint of mold coating, a high-strength material causes a reduction in life.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high carbon thin steel sheet which improves strength and punchability at the same time. A specific object of the present invention is a strength of 300 N / mm ²
Accordingly, it is an object of the present invention to provide a high carbon thin steel sheet which simultaneously improves the strength and the punching property in which the punching property indicated by the number of punching is 500,000 times or more.

[0007]

As a result of repeated studies, the present inventors have rather conceived of providing a resin film as a kind of lubricating film on the high carbon thin steel sheet side. Punching is processed at a higher speed even compared to press molding, so it was doubtful that the resin film could follow such deformation well, but unexpectedly it was rather high speed and seizure disappeared. It has been found that unexpected effects can be obtained, such as the fact that the punching performance can be 500,000 to 2,500,000 times, far exceeding the conventional 50,000 to 100,000 times, and the present invention has been completed.

[0008] The lubricating effect of the resin film at the time of punching is due to the fact that the film extends around the cut surface side,
In particular, it works effectively in the area where shearing starts. Therefore, it is different from the lubrication action at the time of press working.

The gist of the present invention is as follows:
C: 0.2-1.5%, Si: 0.05-0.5%, Mn: 0.1-2.0
% Or less, Cr: 0 to 0.5%, B: 0 to 0.01%, a high carbon thin steel sheet having a steel composition consisting of the balance of Fe and unavoidable impurities, provided with a resin film having a thickness of 0.1 μm to 1.0 mm on the surface. This is a high carbon thin steel sheet having excellent punching properties and rust prevention properties.

The steel composition may contain B: 0.0005 to 0.01%. The resin film preferably has an inorganic binder having a weight ratio of inorganic binder / resin film of 2.0.
It may be contained as follows.

Specifically, the inorganic binder is at least one selected from the group consisting of chromic acid, silica sol, aluminum hydroxide, magnesium hydroxide, alumina, titania, borate compounds, and phosphate compounds. As described above, the present invention intends to improve the punching property by coating the surface of a high-carbon thin steel sheet with a resin so that the steel sheet itself has lubricity.

Usually, the resin applied to the surface wraps around to the shear surface side during punching, and becomes a lubricant. The high carbon steel sheet has a high hardness and is extremely poor in punchability when there is no lubrication. This is because resin coating is effective for improving the punching property of a high carbon steel sheet having poor punching properties. This resin coating also exhibited an effect on rust prevention, and solved the problem of rusting during storage compared to conventional steel plates without a coating.

[0013]

The object of the present invention is a high carbon thin steel sheet, which is usually 0.1 to 2.3 mm thick, but is not particularly limited. The strength level may be about 350 to 560 N / mm ² . However, the recent trend is that TS is over 450,
The invention is particularly preferred for punching such high strength level thin steel sheets.

In the high carbon thin steel sheet according to the present invention,
Is not less than 0.2% and not more than 1.5%. If the content is less than 0.2%, the hardness of the steel sheet itself is not low, and if it exceeds 1.5%, the hardness becomes high. Since it is difficult to manufacture thin steel sheets, the content is set to 1.5% or less. Preferably, it is 0.2-0.8%.

Although Si is effective as a deoxidizing material, it contributes to the improvement of the steel sheet strength by being present at 0.05% or more.
If it exceeds 5%, the punching property is deteriorated.
05 to 0.5%. Preferably it is 0.1-0.3%.

Mn is an important element for hardenability.
Add to high carbon steel. If it is less than 0.1%, the hardenability is poor, and if it exceeds 2.0%, the hardness becomes high and punching becomes difficult, so the content is made 0.1% or more and 2.0% or less. Preferably it is 0.2-1.0%.

Cr is an element effective for improving hardenability.
If added over 0.5%, embrittlement occurs due to precipitation of carbides, which is harmful. However, the strength is not particularly changed even when Cr is not added.

B is 0.01% when the hardenability is further improved.
% Or less. However, if the content is 0.0005% or less, there is no improvement effect, and if it exceeds 0.01%, brittleness occurs. Therefore, in the case of positive addition, the content is set to 0.0005% or more and 0.01% or less. Preferably 0.00
05-0.003%.

The type of resin film used in the present invention for improving the punching property and rust prevention property is, for example, acrylic resin, acrylic-styrene resin, polyethylene, polypropylene, vinyl acetate resin, epoxy resin, vinyl chloride resin, fluorine resin. , Phenolic resin, melamine resin and the like, these resins are applied in a normal coating method, for example,
The coating is performed by a method using a roll coater, a method using a sprayer, a method using a ringer roll, a method using a curtain flow, and then baking by a usual drying method, for example, drying with hot air or drying by induction heating.

Inorganic binders such as chromic acid, silica sol, aluminum hydroxide, magnesium hydroxide, etc., for improving the adhesion to these resins,
One or more inorganic substances such as oxides such as alumina and titania, boric acid compounds, and phosphoric acid compounds may be contained.

The thickness of the resin film to be formed is 0.1 μm or more and 1.0 mm or less. If it is less than 0.1 μm, the lubricating effect is not exhibited, and the punching property is not improved. On the other hand, if it exceeds 1.0 mm, the adhesion of the film becomes poor, and the powder peeled off from the resin at the time of punching accumulates in the mold to cause a punching trouble.

When an inorganic binder is added, the weight ratio of the inorganic binder / resin film is preferably 2.0 or less. The addition of this ratio exceeding 2.0 is to deteriorate the adhesion of the resin film. More preferably, this ratio is 0.
An inorganic binder is added so as to be 2 to 0.5.

[0023]

【Example】

(Example 1) A high carbon steel slab having the composition shown in Table 1 (227
(mm thickness x 1000 mm width) was finished into a 2.0 mm thick hot rolled coil by ordinary hot rolling. Subsequently, after one or two cold rollings and a finish annealing including a normal pickling intermediate annealing, a temper rolling and a flat correction or only a flat correction were performed to produce a 0.5 mm thick high carbon steel coil.

An acrylic-styrene resin emulsion (concentration: 40 g / l) was applied on the front and back surfaces of the coil by a roll coater and baked by hot air drying. The film thickness after baking
It was 0.4 μm.

The high carbon steel sheet provided with the resin film was subjected to a high-speed continuous punching test using a 25-ton press. As Comparative Example 1, the same coil without a resin film was also subjected to a punching test.

A rust test was also conducted in a thermo-hygrostat at 30 ° C. and a relative humidity of 80% to examine the rust prevention.

(Example 2) A high carbon steel slab (227 mm thick x 1000 mm wide) having the composition shown in Table 1 was subjected to ordinary hot rolling.
It was finished into a 2.0 mm thick hot rolled coil. Subsequently, after one or two cold rollings and a finish annealing including a normal pickling intermediate annealing, a temper rolling and a flat correction or only a flat correction were performed to produce a 0.5 mm thick high carbon steel coil.

A coating liquid obtained by mixing an acrylic resin emulsion liquid (concentration: 40 g / l), chromic acid (20 g / l), and colloidal silica (5 g / l) on the front and back surfaces of the coil is baked by hot air drying after coating with a roll coater. Was. The film thickness after baking was 3 μm.

The high carbon steel sheet provided with the resin film was subjected to a high-speed continuous punching test using a 25-ton press. As Comparative Example 2, the same coil without a resin film was subjected to a punching test. A rust test was also conducted in a thermo-hygrostat at 30 ° C. and a relative humidity of 80% to examine rust prevention.

Example 3 A high carbon steel slab (227 mm thick × 1000 mm wide) having the composition shown in Table 1 was subjected to ordinary hot rolling.
It was finished into a 2.0 mm thick hot rolled coil. Subsequently, after one or two cold rollings and a finish annealing including a normal pickling intermediate annealing, a temper rolling and a flat correction or only a flat correction were performed to produce a 0.5 mm thick high carbon steel coil. Acrylic resin emulsion liquid (concentration 40 g / l) on the front and back of such coil
A coating solution containing a mixture of chromic acid (20 g / l) and colloidal silica (5 g / l) was coated with a roll coater and baked by hot air drying. The film thickness after baking was 3 μm.

The high-carbon steel sheet provided with the resin film was subjected to a high-speed continuous punching test using a 25-ton press. As Comparative Example 3, the same coil without a resin film was subjected to a punching test. A rust test was conducted in a thermo-hygrostat at 30 ° C. and a relative humidity of 80% to examine rust prevention.

Example 4 A high-carbon steel slab (227 mm thick × 1000 mm wide) having the composition shown in Table 1 was subjected to ordinary hot rolling.
It was finished into a 2.0 mm thick hot rolled coil. Subsequently, after one or two cold rollings and a finish annealing including a normal pickling intermediate annealing, a temper rolling and a flat correction or only a flat correction were performed to produce a 0.5 mm thick high carbon steel coil.

On the front and back surfaces of such a coil, a melamine resin paint dispersed with polyethylene wax (concentration 500 g / l)
And a titania (20 g / l) mixed solution was coated with a roll coater and baked by hot air drying. The film thickness after baking was 150 μm.

The high carbon steel sheet provided with the resin film was subjected to a high-speed continuous punching test using a 25-ton press. As Comparative Example 4, the same coil without a resin film was subjected to a punching test. A rust test was conducted in a thermo-hygrostat at 30 ° C. and a relative humidity of 80% to examine rust prevention.

Example 5 A high carbon steel slab (227 mm thick × 1000 mm wide) having the composition shown in Table 1 was subjected to ordinary hot rolling.
It was finished into a 2.0 mm thick hot rolled coil. Subsequently, after one or two cold rollings and a finish annealing including a normal pickling intermediate annealing, a temper rolling and a flat correction or only a flat correction were performed to produce a 0.5 mm thick high carbon steel coil.

A coating in which polyethylene wax is dispersed in a melamine resin coating on the front and back surfaces of such a coil (concentration 500 g / l)
And a titania (20 g / l) mixed solution was coated with a roll coater and baked by hot air drying. The film thickness after baking was 2 mm.

The high carbon steel sheet provided with the resin film was subjected to a high-speed continuous punching test using a 25-ton press. As Comparative Example 5, the same coil without a resin film was subjected to a punching test. A rust test was conducted in a thermo-hygrostat at 30 ° C. and a relative humidity of 80% to examine rust prevention.

Example 6 A high-carbon steel slab (227 mm thick × 1000 mm wide) having the composition shown in Table 1 was subjected to ordinary hot rolling.
It was finished into a 2.0 mm thick hot rolled coil. Subsequently, after one or two cold rollings and a finish annealing including a normal pickling intermediate annealing, a temper rolling and a flat correction or only a flat correction were performed to produce a 0.5 mm thick high carbon steel coil.

An acrylic-styrene resin emulsion (concentration: 40 g / l) and a roll coater were applied to the front and back surfaces of the coil, and then baked by hot air drying. The film thickness after baking was 0.05 μm.

The high carbon steel sheet provided with the resin film was subjected to a high-speed continuous punching test using a 25-ton press. As Comparative Example 6, the same coil without a resin film was subjected to a punching test. A rust test was conducted in a thermo-hygrostat at 30 ° C. and a relative humidity of 80% to examine rust prevention.

Comparative Example 7 A high-carbon steel slab (227 mm thick × 1000 mm wide) having the composition shown in Table 1 was subjected to ordinary hot rolling.
It was finished into a 2.0 mm thick hot rolled coil. Subsequently, cold rolling was performed once or twice including normal pickling intermediate annealing, but coil breakage occurred frequently and did not result in a product coil. The results of Examples 1 to 6 and Comparative Examples 1 to 7 are summarized in Table 1 below.

(Examples 7 to 9) Example 1 was repeated, and a resin film to which an inorganic binder was added as shown in Table 1 was used. Similarly, the results are shown in Table 1.

[0043]

[Table 1]

[0044]

As described above, according to the present invention, a punching property of 500,000 times or more can be ensured, and at the same time, a high strength such as a tensile strength of 450 N / mm ² or more can be obtained. It is possible to obtain a high carbon strip steel having excellent punching properties, and the mold life is improved to 5 times or more, generally 10 times or more as compared with conventional ones. The significance of the above is great.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C22C 38/00-38/60 B32B 15/08

Claims (3)

(57) [Claims] C .: 0.2 to 1.5%, Si: 0.05 to 0.5%, Mn: 0.1 to 2.0% by weight.
%, Cr: 0 to 0.5%, B: 0 to 0.01%, a high carbon thin steel sheet having a steel composition comprising the balance of Fe and unavoidable impurities, provided with a resin film having a thickness of 0.1 µm to 1.0 mm on the surface. High carbon thin steel sheet with excellent punching and rust prevention characteristics. 2. The high carbon thin steel sheet according to claim 1, wherein said resin film contains an inorganic binder. 3. The method according to claim 2, wherein the inorganic binder is at least one selected from the group consisting of chromic acid, silica sol, aluminum hydroxide, magnesium hydroxide, alumina, titania, borate compounds, and phosphate compounds. Carbon steel sheet.