JPH01199715A - Method for shearing steel plate - Google Patents

Abstract

PURPOSE:To prevent the generation of saw edge even if cold rolling is performed in the post process by carrying out shearing after cooling a shearing portion down to below the fracture transition temperature of a steel plate and making a shear fracture in a favorable condition. CONSTITUTION:A steel plate 10 is conveyed from the arrow direction by means of a plurality of rolls 11 and trimmed by a side trimmer 12. That is, a cooling gas is previously blown against the steel plate 10 from nozzles 13 to cool same to below the fracture transition temperature thereof and then, the steel plate 10 is sheared by the trimmer 12. Whether the steel plate has reached the transition temperature is confirmed by a radiation thermometer 14 and when the temperature is not reached yet, the cooling gas is increased to obtain the prescribed temperature. Since the steel plate 10 thus sheared has a temperature below the fracture transition temperature, i.e., a temperature with approx. 50% ductile fracture ratio, the sheared form is favorable and further, as it is not necessary to make the clearance in a process too small, a tool life can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for shearing a steel plate, and more particularly, to a method for shearing a steel plate that can form a normal shear plane even when the material is a soft material.

(Prior art and its problems) Shearing methods for steel plates include punching, drilling, shearing, edging, etc., and although they differ depending on the processing purpose, they are all performed using a pair of tools placed at an appropriate distance. , is a processing method that mainly generates shear stress in the raw steel plate and separates it into desired dimensions or shapes. In this shearing method, the most important thing is the shape of the sheared surface.
Whether it is good or bad has a great influence on the commercial value of the steel sheet or the shape of the end of the product in the subsequent process.

Now, as a factor that affects the shape of the shear plane, (1
) Mechanical properties of the material, (2) Material and product shape, (3
) Tool cutting edge shape, (4) Tool surface lubrication, (5) Material support conditions, (6) Tool spacing, (7) Machining speed, (8
) There are many factors such as machining temperature, but the one that has the greatest influence is the tool spacing (hereinafter referred to as clearance).

-i, the standard spacing suitable for the material is determined for the clearance as shown in Table 1.

Table 1 (The values are percentages of the plate thickness) Depending on whether this clearance is appropriate, the shear plane shape will be thick (changes 0). For example, as shown in Figure 1 (a), (b), and When shearing the material 2 to be sheared with the tool 1, if the clearance d is appropriate, the cracks 3 will meet well, as shown in FIG.

However, if the clearance d is too small, the cracks 3 will cross each other and then meet again, as shown in FIG. Moreover, if the clearance d is too large, the sheared surface shape will deteriorate because they will not meet well, as shown in FIG. 2(C). As described above, since clearance adjustment is extremely important, various adjustment methods and devices have been proposed. For example, Special Public Interest Publication No. 56-46929
The device disclosed in the above publication is one of them. This device is equipped with a clearance adjustment device for the upper and lower cutters in a slitter device that cuts the transferred plate material, and a thickness measuring device that measures the thickness of the plate material is arranged at a distance in the slitter device to adjust the clearance and the plate material. The clearance device is operated based on the comparison output to maintain an appropriate clearance.

However, with this device, the clearance adjustment is determined only by the thickness of the plate material to be sheared, and the mechanical properties of the plate material are not taken into account, and in the case of soft steel, it may not be possible to obtain a good shear surface. there were.

Especially in the case of shearing soft steel sheets, which has recently seen an increase in demand,
It is necessary to reduce the clearance, but if the clearance is too small, there are problems such as premature wear of the tool.

(Means for Solving the Problems) The inventors of the present invention have continued their research into ways to form a good shearing surface even with soft steel plates and to extend tool life. We confirmed the following facts: (1) the shear plane of the material is made up of ductile and brittle fracture surfaces, and (2) the shear plane has a large proportion of brittle fracture surfaces. ■We learned that the smaller the ductile fracture surface, the longer the tool life.
The present invention has now been completed.

That is, the gist of the present invention is ``a method for shearing a steel plate, which comprises cooling the sheared portion to below the fracture surface transition temperature of the steel plate before shearing the steel plate''.

Here, the fracture surface transition temperature refers to the temperature at which 50% of the total fracture surface area becomes a ductile fracture surface.

As shown in Figure 2, a soft steel plate exhibits ductility at room temperature, but as the temperature drops and reaches the transition temperature region, the absorbed energy rapidly decreases and it becomes brittle. . The transition temperature varies greatly depending on the chemical composition. For example, in the case of steel with 0.003% C, it is -50°C, and in the case of steel with 0.15% C, it is -20°C,
When C is 0.2%, it is 0°C.

Now, as mentioned above, steel sheets have a specific transition temperature. Therefore, since the ductility and brittle strength of the steel sheet vary greatly depending on whether the temperature is higher or lower than that, the shear plane also changes depending on the temperature of the steel sheet during shearing.

Figure 3 specifically explains the above,
Figure (a) shows the relationship between temperature during shearing and ductile fracture,
FIG. 5B is a diagram showing the state of the fracture surface corresponding to the symbols in FIG. As can be seen from the figure, when shearing at a high temperature (point A in the figure), the ductile fracture surface is 100%, but when the temperature is lower (point B in the figure), the ductile fracture rate is 50%.
When the temperature becomes even lower (point C in the figure), the ductile fracture ratio becomes 0%.

The temperature at point B in the figure (al) is the fracture surface transition temperature in the present invention, and when sheared below this temperature, the shear fracture surface has a good shape. Even during rolling, sawing does not occur.

(Function) Hereinafter, a case where the present invention is applied to a side trimmer for a steel plate will be described.

Generally, side trimming of a steel plate is performed after pickling or cold rolling of a hot rolled steel plate, so not only dimensional accuracy but also the shape of the sheared surface is important.

If the cutting method is not accurate, tolerance deviations may occur, and if the shape of the sheared surface is poor, saw edges may occur at the edges of the steel plate during cold rolling.
Sometimes there are problems such as edge breakage, so it is necessary to pay close attention to the shearing condition. Figure 4(a) [
]) shows a state in which trimming is performed with the side trimmer, in which figure (a) is a side view, and figure (b) is a sectional view in the axial direction of the roll.

In the figure, 10 is a steel plate, 11 is a roll, 12 is a side trimmer, 13 is a cooling gas nose, and 14 is a radiation thermometer. In such a configuration, the steel plate lO is conveyed by a plurality of rolls 11 in the direction shown by the arrow in the figure and trimmed by a side trimmer 12. However, in advance, a cooling gas such as liquid nitrogen, etc. is supplied from a cooling gas nozzle 13. A low temperature liquefied gas of
It is sheared. It is confirmed by the radiation thermometer 14 whether 14+Ii, 10 has reached the transition temperature, and if it has not reached the transition temperature, the cooling gas is increased to reach a predetermined temperature. Alternatively, a method of blowing cooling gas as described above is good for cooling the steel plate 10, but as shown in FIG. It may be possible to blow in nitrogen or the like, or it may be possible to use both in combination.

Since the steel plate 10 sheared in this way has a temperature below the fracture transition temperature, that is, the ductile fracture ratio is below 50%, the sheared shape is good and the tool clearance needs to be small. Tool life can be extended because there are no holes.

In the present invention, it is more preferable to shear at a temperature at which the ductile fracture ratio below the fracture surface transition temperature is 30% or less in order to improve the sheared surface shape. Further, the present invention is effective for soft steel materials, particularly steel plates containing 0.01% or less of C. If the C content is 0.01% or more, the shear surface shape can be improved to a certain extent by adjusting the clearance.
This is because if C becomes 0.01% or less, it cannot be improved only by adjusting the clearance.

(Example) Hereinafter, this will be explained in detail with reference to Examples.

(Invention Example 1) Using the apparatus shown in FIG. 4(a), the C content was 0.003%.
, a pickled hot-rolled steel plate with a thickness of 3m+m and a radius of 1212+uw was trimmed to 12001111. During trimming, liquefied nitrogen gas (boiling point -196°C) was sprayed from a cooling gas nozzle located 7 mm from the edge of the steel plate.

Then, when we measured the steel plate edge temperature with a radiation thermometer, we found that
The steel plate temperature reached -50°C from the edge to 30m5 inside. Therefore, the clearance of the side trimmer was set to 0.
．． When shearing was performed at a setting of 3 m+m, the sheared surface had a ductile fracture ratio of 22% and a brittle fracture ratio of 78%, and a good sheared surface without droop or burrs. Further, when this steel plate was cold-rolled to a thickness of 0.5 am, a cold-rolled steel plate with good end shape was produced without any sawing. And since the clearance was the same as for normal C, I was able to use it for 2 days without changing tools.

(Invention Example 2) C content is 0.003%, thickness 2.8 am, width 1205
A ++m hot rolled steel plate was trimmed to 1200mm.

Other shearing conditions were the same as in Invention Example 1. Although the trimming in this case was very small at 2.51, a good shear surface was obtained. Conventionally, trimming approximately twice the board thickness would be required, but the present invention has made it possible to perform minute trimming.

(Conventional example) CO, 01
%, thickness 3. OLIlm, a hot rolled steel plate with a width of 1215 mm was trimmed to 1200 mm. As a result, the ductile fracture ratio was 70%, and the sheared surface was rough. Since the clearance in this case was set to 0.1no+, cracks and seizures occurred in the tool, and the tool had to be replaced after 5 hours.

(Effects of the Invention) As explained above, when shearing a steel plate, by cooling the processed part to a certain temperature or lower, a good sheared surface without droop or burrs can be obtained, so it is possible to avoid deviations from dimensional tolerances. (Also, there is no adverse effect on the end shape of the product in the subsequent process.

Furthermore, since minute trimming is possible, the yield is also improved, which is an excellent effect.

[Brief explanation of the drawing]

Figures 1 (a), (g), and (c) are diagrams explaining the tool clearance and fracture surface condition. Figure 2 is a diagram showing the relationship between material temperature and absorbed energy. Figure 3 (a) is the material A diagram showing the relationship between temperature and ductile fracture ratio, Figure 3 (1)) is a diagram showing the fracture surface state of the material at points A, B, and C in Figure 3 (a), Figure 4 (al ( b) is a diagram of an apparatus for carrying out the present invention. l is a tool, 2 is a material to be sheared, 3 is a crack, 10 is a fence board, 11
is a roll, 12 is a side trimmer, 13 is a cooling gas norz, 14 is a radiation thermometer, 15 is a cavity applicant Sumitomo Metal Industries, Ltd. (and 1 other person) agent Patent attorney Terutada Hogami (1 idiot) No. 1121 ( a) (b) (c) Figure 2 Figure 3

Claims (1)

[Claims] A method for shearing a steel plate, which comprises cooling the sheared portion to a temperature below the fracture surface transition temperature of the steel plate before shearing the steel plate.