JPS63260716A - Method for reducing burrs generated in shearing of steel sheet - Google Patents

Abstract

PURPOSE:To suppress production of burrs at the time of shearing and improve the surface quality of products by irradiating laser beam to a narrow zone of the shearing deformation part of a steel band whereon burrs are generated, followed by heat treatment, and by hardening only surface of the steel plate. CONSTITUTION:Shearing deformation is generated in the part situated between two tools, wherein burrs will be generated in normal operating condition. Laser is irradiated along the shearing line and that surface of steel plate where burrs are generated. Hardened layer is produced on the surface of the steel plate by heating and cooling, and ductility of this part is lowered through hardening of this layer so as to prevent generation of burrs. The depth of the hardened layer shall be approx. 10-35% of the plate thickness. This can resolve problems likely to occur with generation of burrs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for reducing burrs generated during shearing of a steel plate by laser heat treatment.

[Prior Art] Steel sheets are usually supplied to the user in the form of a copper strip (coil) having a constant width. Therefore, after rolling, the manufacturer cuts (trims) both ends of the coil using a blade. At this time, there are burrs (
(also called Paris) is generated. In addition, burrs usually occur at the cut end of the steel plate during blanking during the pressing process and when cutting with a shearing machine. All of these processing methods have in common that the material undergoes shearing deformation between tools, resulting in cutting, and is collectively referred to as shear processing. The shape of the burr is irregular, and part of it may come off from the steel plate when the steel plate is handled. These burrs often deteriorate product performance and cause problems in the production process.

For example, in the process of producing exterior panels for automobiles, if the generated burrs come off the edge of a steel plate and fall onto the surface of that steel plate or another steel plate, and remain attached thereto, the burrs may Even if the size is as small as 30#Lm, the appearance after pressing and painting will be seriously damaged.

In addition, if there is a burr on the edge of a steel plate, the surface is activated by shearing, and the paint is difficult to adhere to, making it prone to rust. This progresses and significantly reduces the life of the product.

Burrs generated during shearing of steel plates are removed by barrel polishing, belt polishing, grinder polishing, etc. for example,
In the manufacturing process of automobile exterior panels, it is necessary to touch up and remove particles using a grinder before painting. This increases costs.

Since burrs are produced by unnecessary substances and cause harm, their removal naturally requires an additional production process, leading to an increase in production costs.

As a shearing method that does not produce burrs, it is possible to reduce the burrs by reducing the clearance when shearing steel plates, but this method applies large shearing stress to the blades, shortening the lifespan of the blades and increasing costs. This will lead to an increase in

JP-A-511-224090 discloses a method of irradiating a laser beam and cutting a steel plate using the generated heat. In this method, a low-energy laser beam is irradiated from the top surface of the steel plate to form a groove, and then a high-energy laser beam is irradiated along the groove from the opposite side to cut the steel plate. is not generated. In this method of using a laser beam for fusing, the energy efficiency of the laser is low, so cutting costs increase and it is not economical. Therefore, it is used in processes that involve very expensive materials such as electrical steel sheets, and in small-scale production such as prototyping, but it is also used in cutting ordinary steel sheets in the automobile and home appliance industries where mass production is carried out. is not used.

[Problems to be Solved by the Invention] The present invention overcomes these drawbacks of the prior art, improves the energy efficiency of the laser beam, suppresses the formation of burrs during shearing, and improves the production process. The purpose is to eliminate problems and improve the surface quality of products.

[Means for Solving the Problems] The present invention heat-treats only a narrow range of the shear deformation part of the steel strip where burrs occur in the conventional process, hardening only the surface of the steel sheet, and This prevents burrs from forming when a section is cut.It consists of a laser beam that is applied to the surface of the steel plate on the side where burrs will occur along the processing line when shearing the steel plate to reduce the surface structure. This is a method for reducing burrs that occur during shearing of a steel plate, which is characterized by performing shearing along the processing line after hardening.

The reasons for the limitations of the present invention will be explained below.

First, in the present invention, the material undergoes shear deformation at the portion sandwiched between the two tools, and burrs occur under normal working conditions. This is because when the clearance is reduced to prevent burrs from occurring, the tool wear increases.
This is because it cannot be adopted from the viewpoint of performing the work economically. Under such shearing conditions, the laser is irradiated along the shearing line on the surface of the steel plate on the side where burrs occur in the present invention, because heating and cooling by laser irradiation generates a hardened layer on the surface of the steel plate, and this layer This is to reduce the ductility of this part by hardening and prevent the occurrence of burrs.

In the present invention, the reason why the laser is irradiated along the shearing line as described above is that the heat treatment effect of the laser is sufficient as long as it extends to the sheared area. It is sufficient that the irradiation range has a width equivalent to the thickness of the plate along the shearing line. Further, it is appropriate that the depth of the hardened layer is approximately 10% to 35% of the board thickness.

The occurrence of burrs is not limited to only one side, but burrs on the side that is being scrapped are less of a problem, and in most cases laser irradiation on only one side is sufficient. However, if burrs appear on both sides and become a problem, or if the burrs are severe even on just one side, irradiating both sides with a laser will make burrs more difficult to occur as the rigidity of the steel plate improves. In this case as well, it is appropriate that the depth of the hardened layer on each surface be approximately 10% to 35% of the board thickness.

The reason why a laser is used in the present invention is that it is suitable for rapid heating, has excellent controllability, and is most suitable for local heating and cooling.

[Example] The effects of the present invention will be explained below using examples.

Table 1 shows the chemical composition of the test steel.

All test materials are the above test steels that are continuously cast, hot rolled, and pickled.
Continuously annealed. Laser irradiation was performed using a YAG laser with a maximum output of 300 W in a continuous manner. Heating rate is 10' to 105 °C/S% Cooling rate is 10
3°C/S.

Table 2 shows the results obtained by carrying out the method of the present invention on each sample steel.
4.5 and Comparative Example 1.3 are shown in comparison. Here, the pari occurrence rate indicates the ratio of the burr length to the processed wire length. It is clear from this that the effect of laser irradiation on preventing the occurrence of burrs is significantly greater than that of the comparative example.

Table 2 [Effects of the Invention] The present invention is a low-cost method for preventing burrs that occur during shearing of steel plates, which can be a problem, by irradiating a laser along the processing line. It is an economically and industrially valuable invention that can solve problems.

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Claims (1)

[Claims] When shearing a steel plate, the surface of the steel plate on the side where burrs occur along the shearing line is irradiated with a laser to harden the surface structure, and then shearing is performed along the shearing line. A method to reduce burrs that occur during shearing of steel plates.