JPH02258181A - Manufacturing method of ERW pipe with few welding defects - Google Patents

Abstract

PURPOSE:To reduce the rate of incidence of weld defects by welding a blank steel plate containing specific weight % C, Mn, Si, Al, N, Cr, Mo, NI, Nb, V, Ti and B at the specific welding speed, butt angle, and feeding distance. CONSTITUTION:The blank steel plate consists of, % by weight, <=0.05% C, <=2.0% Mn, <=0.60% Si, <=0.10% P, <=0.03% S, 0.05-0.10% Al and <=0.0150% N as basic components and contains >=1 kind among <=1.00% Cr, Mo and Ni, <=0.50% Nb, V and Ti, <=0.0050% B and the balance Fe. This blank steel plate 1 is welded at 50m/min welding speed, >=3 deg. butt angle theta and <=140mm feeding distance L. By this method, toughness and workability of the subject resistance welded tube are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an electric resistance welded pipe with fewer weld defects.

(Prior Art) As is well known, in the production of electric resistance welded pipes, the edges of the steel strip to be welded are heated by electrical resistance or induction, and then pressure welded (welded) using squeeze rolls. The welded portions of electrical resistance welded pipes manufactured in this manner often have welding defects, which deteriorate toughness and workability.

Oxide-based inclusions are likely to occur in welded portions of electric resistance welded pipes, and these become weld defects. In order to reduce welding defects caused by these oxide-based inclusions, for example, as disclosed in Japanese Patent Application Laid-Open No. 50-39665, every time an oxidizing gas is injected into the welding area,
The heated end to be pressure welded is heated to a higher temperature to make it easier to discharge the liquid oxide at the end, the oxide is discharged by pressure welding, and the oxide is returned to the welded (pressure welded) part after welding. There are known methods that do not leave any residue.

(Problems to be Solved by the Invention) In the method described above in which oxygen gas is injected into the welding area, the amount of oxide generated increases due to the injection of oxygen gas, so welding defects due to oxide inclusions occur. There is a limit to the reduction of , and there is a disadvantage that a sufficient effect cannot be obtained. In addition, especially low carbon preparations and these Zn,
With Aff-plated steel, the softening caused by the welding heat is easily deformed, which reduces the force required to expel liquid oxide from the edges to be welded, resulting in less welding (pressure welding) after welding. ) had the disadvantage that oxides remained in the parts.

The present invention has been made to advantageously solve the above problems.

(First step to solve the problem) The gist of the present invention is as follows: C: 0.05% or less Mn: 2.0% or less Si: Q, 5Q% or less P: 0.100% S: 0.030% or less p, p: 0.005 to 0.100%N・0
．． The basic component is 0150 copies, Cr: 1.00% or less, Mail, QQ% or more]':, N
1: 100% or less, Nb: 0.500% or less, V
: 0.500% or less, Ti: 0.500% or less,
B: A bare +A steel plate containing one or more types of 0.0050% or less and the remainder [+e and unavoidable impurities] was welded at a welding speed of 50 m/min or more, and the butt angle was 3°.
There is a method for manufacturing an electric resistance welded pipe with few welding defects, which is characterized by welding the electric power feeding distance as wide as 140 mm or less and as short as 140 mm or less.

Therefore, the present invention reduces the softening effect caused by the influence of welding heat, prevents a decrease in the force necessary to discharge the liquid oxide in the welded part, and reduces the welding (pressure welding) after welding.
No oxides remain in the welded parts - (This significantly reduces welding defects caused by oxide inclusions, and at the same time improves the toughness of the ERW welded parts.
Improve processing 1-1. The aim is to manufacture ERW pipes of superior quality.

According to the means of the present invention, each time an inert gas is injected into the welding area, the oxygen concentration in the welding area is lowered, oxide-based inclusions are reduced, and the incidence of welding defects is reduced. Can be used together. In other words, a jet of inert gas! ]=1
' 4. While keeping the amount of oxide generated low, at the same time increasing the welding speed, widening the butt angle, shortening the power supply distance, and reducing the softening effect due to the effects of welding heat, welding Welding (pressure welding) after welding prevents the drop in force required to expel the liquid oxide at the end to be welded
This makes it possible to significantly reduce welding defects due to oxide-based inclusions without leaving any oxides in the welding area, and to significantly reduce the incidence of welding defects.

Next, we will discuss in detail the softening caused by the effects of welding heat.

The heat affected zone created by electric resistance welding has the highest temperature at the welding surface. Since the temperature of the welding surface rises to the melting temperature of the steel material, the phase immediately adjacent to the welding surface reaches a high temperature immediately above the melting temperature. Steel materials generally soften at high temperatures, but especially)
L and J softening is significant near the melting temperature. In other words, during electric resistance welding, softening occurs when the temperature rises close to the melting temperature of steel H, which occurs immediately near the welding surface 41. That's what I do.

In order to reduce the thickness of the softening layer that inevitably occurs, it is effective to prevent the expansion of the softening layer by achieving rapid heating.

Next, we will discuss ingredient limitations.

C is an effective element for ensuring the strength of the steel layer, but
In order to improve workability, it is desirable to have a smaller amount. C is 0.
When it is less than 0.5%, the softening caused by the welding heat is easily deformed, the force required to expel the liquid oxide at the end to be welded is reduced, and oxidation occurs in the welded (pressure welded) part after welding. The scope of application of the present invention was limited to less than this because the remaining particles would cause welding defects.

Mn is an effective element for increasing strength and toughness, but
If it exceeds 2.0%, weldability deteriorates, so it was limited to less than this.

Although Si is a solid solution hardening element, weldability deteriorates as its content increases, so the upper limit was set at 0.60%.

If P exceeds 0.100%, weldability will deteriorate, so it was limited to less than this.

When S exceeds 0.030%, MnS is formed near the electric resistance welding part.
is precipitated and deteriorates the material properties of the welded part, so it was set to less than this.

AI is an element that is necessary for deoxidizing steel and has the effect of forming nitrides and making the structure finer, but if it exceeds 0.100%, it causes embrittlement of the 7-joint part. Therefore, I have limited it to below. Moreover, if it is less than 0.005%, the amount of manganese-silicate-based oxide increases and internal defects are likely to occur, so it is set to be more than this.

If N exceeds 0.0150%, solid solution nitrogen will increase and the +A quality will harden significantly due to strain aging, so the content was limited to less than 0.0150%.

-1- is a necessary component of the present invention, but in order to supplement strength and toughness, Cr, Mo, Ni, Nb, V,
One or more of l゛i and B are added.

Cr is effective in strengthening the material through solid solution hardening, and M
o, Ni is an element effective in improving toughness. , - Since these elements exhibit their effects within 1.00%, they were set below this range.

Nb, V, and Ti are elements whose strength can be increased by precipitation hardening, but since all of them exhibit hardening within 0.500%, this was set as the upper limit.

B is an element that can increase the strength of grain boundaries, but since the effect is exhibited within 0.0050%, this was set as the upper limit.

When manufacturing electric resistance welded pipes using steel plates with the above-mentioned composition limitations, the welding speed during welding (pressure welding) is increased, the butt angle is widened, and the power feeding distance is shortened to reduce the effects of heat transfer. The present invention is characterized by reducing the degree of softening caused by ζ, and this point will be described below.

The presence of softening forces caused by welding heat effects reduces the force required to expel liquid oxide from the ends to be welded.
U. Oxides remain in the welded (pressure welded) part after welding, which reduces the possibility of welding defects (due to oxide inclusions). In order to prevent this, it is effective to reduce the degree of softening. In order to reduce the softening phase caused by the effects of welding heat, it is effective to prevent the softening phase from expanding whenever rapid heating is achieved.

To achieve rapid heating, it is effective to increase the welding speed, widen the butt angle, and shorten the power supply distance.

) The welding speed is 50 m/min or more, the butt angle is 3° or more,
By limiting the power feeding distance to 140 mm or less, two-speed heating of the electric resistance welding part can be achieved, and the degree of softening can be reduced.
This prevents a drop in the force required to expel liquid oxide from the ends to be welded, prevents oxide from remaining in the welded (pressure welded) area after welding, and significantly reduces welding defects caused by oxide-based inclusions. It is a feature of the present invention that it has been found that the welding defect occurrence rate can be extremely low.

Next, to explain the present invention using FIG. 1, the welding speed is set to 5.
The angle θ (butt angle) formed by the high-frequency heated work 7 (welded part) 4 should be 3° or more, and the distance between the contact 1 - tip or work coil 2 and squeeze roll 3 should be 0 m/min or more. It is manufactured by electric resistance stitching with L (power feeding distance) of 140 mm or less.

Next, Tables 1 and 2 show examples of the present invention.

Table 1 shows an example of the composition of the steel used to manufacture the electric resistance welded pipe using the present invention.

In Example 1 of Table 2, when manufactured using sample N01 of Table 1 under the conditions of welding speed 60 m/min, butt angle 4°, and power feeding distance 120 mm, which satisfy the limiting conditions of the present invention. The incidence of welding defects is very low at 0.5%. On the other hand, in Comparative Example 1 in Table 2, when the welding conditions were the same as in Example 1 and the welding speed was 40 m/min, the incidence of welding defects was 2.1%. That's high.

O (Effects of the Invention) As is clear from the above examples, the present invention reduces oxide inclusions in the welded parts of electric resistance welded pipes of low-carbon, Zn, and IV plated steel materials, and reduces welding defects. Significantly reduces the occurrence rate, improves product yield, and improves toughness,
It has the excellent effect of improving workability as well.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a method of manufacturing an electric resistance welded tube according to the present invention. 1: Low-carbon steel ERW steel pipe 2: Contact tip or work coil 3 Ni-squeeze roll 4: Edge.

Claims (1)

[Claims] C: 0.05% or less Mn: 2.0% or less Si: 0.60% or less P: 0.100% or less S: 0.030% or less Al: 0.005 to The basic components are 0.100% N: 0.0150% or less, Cr: 1.00% or less, Mo: 1.00% or less, Ni:
1.00% or less, Nb: 0.500% or less, V: 0.5
00% or less, Ti: 0.500% or less, B: 0.005
A material steel plate containing 0% or less of one kind or two or more kinds, the balance being Fe and unavoidable impurities is welded at a welding speed of 50 m/min or more, with a wide butt angle of 3° or more, and a power feeding distance of 1
A method for manufacturing an electric resistance welded pipe with few welding defects, characterized by welding the pipe in a short length of 40 mm or less.