JP2003136287A - Cutting method of steel pipe inner surface bead - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting method of steel pipe inner surface bead which is capable of suppressing the wear of a bite as compared with a conventional one. SOLUTION: When the bite 4 for cutting is pressed against the inner surface of a welded part of electric resistance welded tube and the bead formed on its inner surface is cut and removed, a lubricant 13 using an inactive gas as conveying gas is sprayed to the tip of the bite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of cutting a bead on the inner surface of a steel pipe, and in particular, even if the steel type is an electric resistance welded steel pipe containing a high Cr content, the bead formed on the inner surface of the joint is stably cut and removed. The present invention relates to a technique capable of extending the life of a bite to be used as compared with the conventional technique.

[0002]

2. Description of the Related Art An electric resistance welded steel pipe is manufactured by forming a steel strip or a steel plate into a cylindrical shape, and welding the edges of the longitudinally butted ends. At that time, as shown in FIG. 3 (b), a protrusion made of weld metal (mainly steel) called an inner surface bead 1 is formed on the inner surface of the pipe. The presence of this inner surface bead 1 impairs the appearance of the inner surface of the tube, which is not preferable as a product. Therefore, the electric resistance welded steel pipe 2 is generally shipped after cutting the inner bead with an inner bead cutting device equipped with a blade (hereinafter referred to as a bite). The inner surface cutting device is, as shown in FIG. 2, a rod-shaped bar 3 which can be inserted into the inside of a pipe 2 and a cutting tool 4 which is provided at the tip of the bar 3.
And a supporting member 5 to which is attached. Therefore,
When the tip of the cutting tool 4 is pressed against the inner surface of the pipe in the vicinity of the welding point 6 of the running pipe 2, the inner bead 1 is continuously cut. Further, the cutting tool 4 is made of expensive high-speed steel or tool steel, and conventionally, the cutting by it is performed without water and without lubrication in order to avoid complication of the cutting device.

By the way, in such conventional cutting, there has been a problem that the cutting tool 4 is quickly worn and the life of the cutting tool 4 is short. In particular, this problem is remarkable in the electric resistance welded steel pipe of a steel type having a large content of Cr. for that reason,
Not only the cost of the cutting tool 4 is increased, but also the operation of the manufacturing line needs to be stopped for the replacement of the cutting tool, which causes a decrease in the productivity of the electric resistance welded steel pipe. Further, there is another problem that the skill of the operator is required to adjust the setting position of the cutting tool (adjustment of the cutting width and the depth), and only a skilled person can perform the cutting work.

[0004]

SUMMARY OF THE INVENTION In view of such circumstances, it is an object of the present invention to provide a method of cutting a bead on the inner surface of a steel pipe, which is capable of suppressing wear of a cutting tool.

[0005]

Means for Solving the Problems The inventor has conducted extensive studies in order to achieve the above-mentioned object, and the result is the present invention. A method for cutting a bead formed on the inner surface of a steel pipe, characterized in that, when cutting and removing the bead formed on the inner surface, a lubricating oil using an inert gas as a carrier gas is injected to the tip of the cutting tool. .

In this case, it is preferable that the pressure of the carrier gas for the lubricating oil is 50 to 200 KPa. Moreover, it is preferable that the steel type of the electric resistance welded steel pipe is a high Cr content steel.

According to the present invention, even when it is used for cutting a stainless steel electric resistance welded pipe in which the cleanliness of the inner surface of the welded portion is strongly required,
Wear of the cutting tool can be extended much more than before.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below, including the background of the invention.

First, the inventor is
I thought that the lubrication between the cutting tool and the work had to be improved. In addition, since the tip of the cutting tool becomes hot, it is effective to cool the cutting tool.
We thought it better to reduce the cutting resistance of the inner bead. And as a means to embody these ideas,
As is well known for cutting steel materials, we decided to supply lubricating oil (also called cutting oil) to the tip of the cutting tool.

However, since the bar of the cutting device to be inserted into the electric resistance welded steel pipe has a length of at least 2.5 m to the tip of the bite, a stable supply cannot be achieved only by attaching an oil feed pipe to the bar. . Therefore, the inventor
The lubricating oil 13 is sent together with the pressurized air as a carrier gas into the inside of the oil feeding pipe 12 attached to the rod-shaped bar 3 of the cutting device shown in FIG. 2 as shown in FIG. Finally, the stable supply of the lubricating oil 13 was succeeded. In this case, in the present invention, the means for supplying the lubricating oil 13 and the air are not particularly limited, but the use of the mechanical pump 7 (for example, a plunger type) or the like was suitable. This is because it is necessary to pressurize air to at least about 50 KPa for carrying and jetting.

However, when such a cutting method was actually used for an electric resistance welded steel pipe, another problem that cracks or cracks occurred in the welded portion occurred. The inventor diligently investigated the cause of this cracking and the like, and the air heated to a high temperature at the cutting portion flows back to the welding position (welding point 6) in the pipe where oxides such as Cr, Al and Si are formed. And found that they were the starting point. Further, in order to prevent the formation of these oxides, the oxygen concentration in the tube atmosphere should be 0.1 v
It was also found that it was necessary to make it ol% or less. Therefore,
As a countermeasure, the present invention was completed by using an inert gas 8 (for example, nitrogen gas, argon gas, etc.) instead of air as the above-mentioned carrier gas.

In the present invention, the type of lubricating oil used is also not particularly limited. The cutting oil used when lathe cutting ordinary steel materials is sufficient. Further, in the present invention, the pressure of the inert gas of the carrier gas is 50 to 200K.
It is preferably Pa. This is because if it is less than 50 KPa, stable injection of the lubricant becomes difficult, and if it exceeds 200 KPa, the injection becomes excessive.

[0013]

Example: SUS steel containing 11 mass% of Cr has an outer diameter of 2
8.6 to 76.3 mmφ x wall thickness 0.8 to 2.5 mm and outer diameter of ordinary carbon steel 34.0 to 76.3 mmφ x wall thickness 2.
After producing a large number of 0 to 10.0 mm electric resistance welded steel pipes, the beads formed on the inner surfaces of these electric resistance welded steel pipes were cut. At that time, both the cutting method according to the present invention (see FIG. 1) and the conventional non-lubricating cutting method (see FIG. 2) are applied,
The results were compared. Cutting conditions and cutting results are summarized in Table 1
Shown in. The mechanical pump used was a plunger type, nitrogen gas was used as the inert gas, and commercially available refurbished oil was used as the lubricating oil. The tool life in Table 1 is a relative value when the conventional tool life is 1.

From Table 1, it is clear that the cutting method according to the present invention can extend the life of the cutting tool almost three times as long as the conventional one and has a high acceptance rate of the inner surface appearance.

[0015]

[Table 1]

[0016]

As described above, according to the present invention, even when it is used for cutting a stainless electric resistance welded steel pipe in which the cleanliness of the inner surface of the welded portion is strongly required, the wear of the cutting tool can be remarkably extended as compared with the prior art. In addition, the occurrence of internal cracks can be suppressed, and the pass rate as a product is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an implementation state of a method for grinding a bead on a steel pipe inner surface according to the present invention.

FIG. 2 is a diagram illustrating a conventional method of grinding a bead on the inner surface of a steel pipe.

FIG. 3 is a cross-sectional view illustrating a bead generated in a welded portion of an electric resistance welded steel pipe, in which (a) is a steel strip before being joined into a tubular shape,
(B) shows the situation after joining.

[Explanation of symbols]

1 inner bead 2 ERW steel pipe 3 bar-shaped bars 4 bytes 5 Support members 6 Welding points (welding position) 7 Mechanical pump 8 inert gas 9 External bead 10 cutting waste 11 Inner surface position 12 Oil pipe 13 Lubricating oil

Claims (3)

[Claims] 1. A cutting tool is pressed against an inner surface of a welded portion of an electric resistance welded steel pipe to cut a bead formed on the inner surface,
A method for cutting a bead on the inner surface of a steel pipe, characterized in that, at the time of removal, a lubricating oil using an inert gas as a carrier gas is sprayed onto the tip of the cutting tool. 2. The pressure of the carrier gas of the lubricating oil is 50 to 2
The method for cutting an inner bead of a steel pipe according to claim 1, wherein the bead is set to 00 KPa. 3. The method of cutting a bead on the inner surface of a steel pipe according to claim 1, wherein the steel type of the electric resistance welded steel pipe is a high Cr content steel.