JPS5947637B2 - Manufacturing method of pipe clad steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing long pipe clad steel with high adhesive strength and good product yield using a rolling compression method.

Pipe clad steel, which has carbon steel or low alloy steel as the base material pipe and stainless steel, nickel or nickel alloy as the composite material pipe, is an industrially useful product due to its excellent corrosion resistance and mechanical properties. It is.

Therefore, in order to take advantage of these excellent characteristics, there has been a demand for the production of high quality and long pipe clad steel. The extrusion method is well known as a conventional method for manufacturing pipe clad steel, and it has also been used for manufacturing pipe clad steel, but this method requires machining the billet used into a special shape, and also It has drawbacks such as poor yield D due to a large amount of unpressed material.

Other known methods for manufacturing pipe clad steel include the casting method, centrifugal casting method, and explosive crimping method, but each method has advantages and disadvantages and many problems.

The method for manufacturing pipe clad steel using the rolling crimping method was devised as a method that is superior to the various manufacturing methods mentioned above in terms of mass productivity, quality, yield ratio, and manufacturable dimensions, and has not been implemented in the past. ing. There are two main methods for producing pipe clad steel using the rolling crimping method: The first method is, for example, as shown in JP-A No. 53-78966, which is a double base pipe in which carbon steel or low alloy steel is used as a base material pipe and stainless steel, nickel or nickel alloy is fitted as a composite material pipe. This is a method of producing pipe clad steel by strongly overlaying the ends of a double pipe and then hot rolling it.

The second method is, for example, as shown in JP-A No. 53-14155, which uses a double base tube in which carbon steel or low alloy steel is used as a base material tube and stainless steel, nickel or nickel alloy is fitted as a composite material tube. After that, pipe clad steel is produced by explosive crimping, explosion tube expansion, or gas explosion tube expansion to bring them into close contact, and then hot rolling a double base tube with both ends firmly overlaid welded. This is the way to do it.

However, all of these methods have drawbacks as shown below.

In the first method, the gap between the composite pipe and the base metal pipe after fitting is particularly important, and if this gap is large, the overlay weld may break around the entire circumference during heating and rolling. This easily occurs, and as a result, the bonded area is oxidized, causing non-bonding.

Although this weld fracture can be reduced to some extent by improving the amount of overlay welding and rolling conditions, it is difficult to completely prevent it. On the other hand, in the second method, since most of the double pipe is in close contact or in close contact, there is less risk of the full circumference rupture of the overlay weld that occurs in the first method. However, the explosion or gas explosion pipe expansion method used in this method has the disadvantage of poor tightness at both ends and openings, so partial weld breakage cannot be completely prevented, and there is a risk of non-bonding. It is the cause. Although the method of using double tubes that are partially explosively crimped improves the closeness of both ends slightly, good results cannot necessarily be expected.

The reason for this is that when hot-rolling a double blank pipe that has a partially crimped part, the deformation resistance during rolling is different between the crimped part and the non-crimped part. This is because the generation of slag causes a decrease in yield. The purpose of the present invention is to overcome the drawbacks of the conventional manufacturing method of pipe clad steel using the rolling crimping method, and to provide a pipe clad steel that is manufactured by hot rolling a double base pipe in which a composite pipe is inserted into a base pipe and both ends are welded. In manufacturing, the inner surface of the base material tube and the outer surface of the composite material tube are brought into close contact with each other at both ends of the double material tube, and the length s of the adhesive portion is set to be 1/2 or more of the outer diameter of the composite material tube, and the adhesive portion is It is characterized by using a double blank pipe in which the gap between the inner surface of the base material pipe and the outer surface of the composite pipe in the middle part of the double blank pipe is 1.4 inches or less of the outside diameter of the composite pipe in terms of diameter difference. The present invention provides a method for manufacturing pipe clad steel.

The present invention was created based on the results of research and study of conventional technology and original basic experimental research regarding the influence of the gap between the base material pipe and composite material pipe in the production of pipe clad steel by the rolling crimping method. .

In other words, we have found that what is truly important in manufacturing pipe clad steel by the rolling crimping method is the adhesion between the openings at both ends. The present invention will be explained below by way of examples with reference to the drawings.

That is, the double blank tube used in the present invention is as shown in FIG. 1, in which a composite material such as stainless steel, nickel, or nickel alloy is placed inside a base material tube 1 of carbon steel or low alloy steel. Pipe 2 is inserted. Both ends of this double raw pipe are axially connected by a length s between the outer periphery of the composite pipe 2 and the base material pipe 3.
The inner periphery of At this time, the relationship between the length s of the close contact portion and the outer diameter D of the composite pipe 2 is sゝ. Further, the difference e between the inner diameter d of the base material pipe 1 and the outer diameter D of the composite pipe 2 at the intermediate portion other than the close contact portions at both ends of the double raw pipe is 1.496 or less of the outer diameter D of the composite pipe 2; Preferably it is 0.796 or less. At the tube end, the base material tube 1 and the composite material tube 2 are firmly overlay-welded by a welding portion 3. The material specified in the present invention is carbon steel or low alloy steel as the base material, but this material has a body-centered cubic lattice structure below the transformation temperature (approximately 850°C),
The coefficient of thermal expansion is approximately constant W' (13×10° C. per liter) depending on the components. At the transformation point, the crystal structure changes from a body-centered cubic lattice to a face-centered cubic lattice, and the volume shrinks, but beyond that point, the coefficient of thermal expansion is almost the same as that of other metals with a face-centered cubic lattice (17~
20×10-σ/°C). On the other hand, stainless steel, nickel, and nickel alloys specified as composite materials all maintain a face-centered cubic lattice from room temperature to high temperature. The coefficient of thermal expansion varies depending on the material near room temperature, but at 300℃
All of the above have approximately the same coefficient of thermal expansion. A material with a large coefficient of thermal expansion at room temperature is stainless steel, and the upper limit of the gap difference stated in the claims was calculated based on this material, but for the above reasons, this gap difference is almost the same even with other materials. It does not change. When using nickel, which has a small coefficient of thermal expansion at room temperature, the coefficient of thermal expansion is approximately 1.2 inches.
These things have also been confirmed experimentally.

Suitable hot rolling methods for rolling this double blank pipe to produce pipe clad steel include inclined roll perforation mill, plug mill, mandrel mill, and Atsel rolling mill, and the rolling temperature is 850°C. Temperatures between 1300°C and 1300°C are preferred.

The rolling reduction has a very large effect on the crimp rate of pipe clad steel, and it is desirable to roll it to at least 1596 mm or more in one rolling, and preferably a rolling rate of 20 inches or more will result in a pipe clad with a very good crimp rate. You can get steel. The combined double pipe in the present invention is approximately 850
When heated above ℃ (the temperature of the austenite of the base material pipe), the base material pipe and the composite pipe are approximately 0.4% higher due to the difference in thermal expansion coefficient (i), and ( Ii) α of base material →
The r-transformation generates a thermal strain that is approximately 0.396 larger.

Furthermore, during rapid heating, the temperature rises quickly at both ends, so the deformation resistance at both ends is smaller than at the other ends, which causes deformation to concentrate at both ends, causing breakage of the weld. The effect of the present invention is that this weld breakage is completely prevented.

That is, the composite pipe undergoes a larger thermal strain than the base material pipe due to heating, but since the two pipes are in close contact with each other at both ends, deformation in the radial direction is restrained, so a large surface pressure F is generated. The vertical force μF due to this surface pressure F acts as a force to prevent deformation in the axial direction. The conditions under which this axial deformation is constrained are:
It is as follows.

Since the thermal coefficient μ during normal heating is considered to be about 1.0, the close-contact double pipe of the present invention, in which the length S of the close-fitting portion is D/2 or more, can prevent breakage of the welded portion.

Further, the above will be explained with reference to FIGS. 2 and 3.

The axial stress generated in the composite pipe is 0t1, and the circumferential stress is 0θ.
Therefore, under the conditions considered in the present invention, it is thought that the yield stress reaches 0Y at both 0t10 and this was confirmed in experiments. Therefore, the force generated in the axial direction due to thermal stress in the composite pipe Ft is expressed as follows.

On the other hand, the surface pressure F generated by the expansion of the composite pipe is expressed as follows.

Since the force due to surface pressure is expressed in μF, the conditions under which axial deformation is restricted can be considered as follows.

Substituting equations (2) and (8) into equation (4), If we set σt=σθ=0Y S\D/2μ (5Y is derived.

When the axial deformation of the composite pipe is restrained, the radial strain of the composite pipe becomes correspondingly large.In the end, the thermal strain causes approximately 1.4
%, a larger diameter expansion occurs than the base material pipe, but in the present invention, the gap between the base material pipe and the composite material pipe is set to 1.4% or less in terms of diameter difference, so the base material pipe and the composite material pipe are in close contact. reach.

When heated in this state for a certain period of time, diffusion bonding at the bonding surfaces progresses, and a bonding strength that can withstand some degree of severe processing is obtained. However, this bonding strength is low compared to that of explosive bonded clad steel, and is close to pseudo-bonding.
There is little risk of wrinkling of the composite material due to partial crimping, which occurs when explosion-bonded pipe clad steel is rolled, and it is possible to obtain crimped clad steel that is uniform over the entire surface by hot rolling. Next, examples will be described.

[Example 1] Outer diameter 2101111, wall thickness 30m1! , length 2200m1
! The inner surface of the L carbon steel pipe was hub-polished to a roughness of 5 μm and used as a base material pipe.

On the other hand, outer diameter 140mm1 wall thickness 10m11 length 2260m
m(7) SUS3l6L stainless steel pipe was solution treated, the outer surface was hub polished to a roughness of 5μ, and nickel plated to a thickness of 50μ to make a composite pipe. Next, the composite material pipe is inserted into the base material pipe and combined, and the length of the close contact part at both ends of the composite material pipe is S = 1001
After expanding the pipe to a diameter of 1.5 m and bringing it into close contact with the base material pipe, the base material pipe and the composite material pipe were firmly overlay-welded using a stainless steel welding rod over the entire circumference of the end. Further, internal pressure was applied to the composite pipe to expand the pipe so that the gap between the base material pipe and the composite pipe was 1.4% or less of the outside diameter of the composite pipe in terms of diameter difference, thereby creating a double base pipe. Thereafter, two holes with a diameter of 5 m1 were drilled in one of the welded parts to serve as air exhaust holes. After heating this at 1250℃ for 1 hour, it was rolled at once using a piercing rolling machine from the side without air holes to a wall thickness of 15111 and an outer diameter of 22.
It was rolled to 0ml. After cutting both ends of the obtained pipe clad steel, the crimping condition was investigated using ultrasonic flaw detection, and it was confirmed that 100% of the area was crimped. [Example 2] Outer diameter 210m1! L1 wall thickness 30'! 1Em1 length 2.2
The inner surface of a 00mm carbon steel pipe was hub-polished to a roughness of 5μ to obtain a base material pipe.

On the other hand, outer diameter 140Jm11 wall thickness 1011m11 length 2.
A 260 mm nickel tube was hub-polished to a roughness of 5 μm on the outer surface to make a composite tube. Next, insert the composite material pipe into the base material pipe and combine, the length of the close contact part at both ends of the composite material pipe S = 1001t11L
After expanding the tube and bringing it into close contact with the base material tube, the base material tube and composite material tube were firmly overlaid welded using a stainless steel welding rod around the entire circumference of the end. Further, internal pressure was applied to the composite pipe to expand the pipe so that the gap between the base material pipe and the composite pipe was 1.4% or less of the outside diameter of the composite pipe in terms of diameter difference, thereby creating a double base pipe. Thereafter, two holes were made in one of the welded parts using a 5n diameter drill to serve as air exhaust holes.

After heating this at 1250° C. for 1 hour, it was rolled at once using a piercing mill from the side without air holes to a thickness of 151E) and an outer diameter of 220N. After cutting 200 l of both ends of the obtained pipe clad steel, we investigated the crimping condition using ultrasonic flaw detection, and found that 10
It was confirmed that 0% of the area was in a crimped state. [Example 3] The inner surface of a carbon steel pipe with a length of 2,200 U (outer diameter 210 U, wall thickness 30 n) was hub-polished to a roughness of 5 μm to obtain a base material pipe.

On the other hand, a nickel alloy (Cupronickel) tube having an outer diameter of 140 nm, a wall thickness of 10 nm, and a length of 2,260 nm was hub-polished to a roughness of 5 μm on the outer surface to obtain a composite pipe. Next, insert the composite material pipe into the base material pipe and combine, and the length of the close contact part at both ends of the composite material pipe is S = 100
After expanding the tube as n and bringing it into close contact with the base material tube, the base material tube and the composite material tube were firmly overlay welded using a stainless steel welding rod over the entire circumference of the end. Further, internal pressure was applied to the composite pipe to expand the pipe so that the gap between the base material pipe and the composite pipe was 1.4% or less of the outside diameter of the composite pipe in terms of diameter difference, thereby creating a double base pipe. Thereafter, two holes were made in one of the welded parts using a 5U diameter drill to serve as air exhaust holes. After heating this at 1250℃ for 1 hour, it was rolled at once using a piercing rolling machine starting from the side without air holes (thickness 15n) and outer diameter 220n.
Rolled to . Both ends of the obtained pipe clad steel were
As a result of investigating the crimping condition using ultrasonic flaw detection after cutting,
It was confirmed that an area of 100 inches was in a crimped state. On the other hand, for comparison, two sets of raw tubes with the same dimensions as above were prepared and subjected to the same surface treatment as above.

For the first set of pipes, the length of the joint at both ends of the composite material is S = 3
After expanding the tube as 0ER and bringing it into close contact with the base metal tube, both ends were firmly welded around the entire circumference with a stainless steel welding rod.

Thereafter, a double blank tube was produced in the same manner as in the above example and hot rolled. The obtained pipe clad steel has 200U on both ends.
After cutting, the crimped state was inspected using ultrasonic flaw detection, and as a result, non-bonded areas were found at both ends, and the bonded area was about 8,596.
For the second set of pipes, the stainless steel pipes were simply inserted and the pipes were overlay-welded at both ends, air holes were provided, and hot rolled under the same conditions as above. Both ends of the obtained pipe clad steel were cut by 200 U, and the crimping condition was investigated using the ultrasonic deep damage method. As a result, a non-bonded part of 6001 mm length was observed on the rolling start side and 200 nm long on the rolling end side. It has been confirmed that the method of the present invention described above is extremely excellent.

[Brief explanation of the drawing]

FIG. 1 is an explanatory longitudinal sectional view of a double pipe used in the present invention. FIG. 2 and FIG. 3 are a longitudinal cross-sectional view and a cross-sectional view, respectively, for explaining the surface pressure at both ends in the present invention. 1
...Base material pipe, 2-...Mixture material pipe, 3...
···welded part.

Claims (1)

[Claims] 1 Carbon steel or low-alloy steel is used as the base material pipe, and a composite material pipe such as stainless steel, nickel, or nickel alloy is inserted inside to form a double base pipe, and both ends of this double base pipe are connected to the base material pipe. In a method of manufacturing pipe clad steel by hot rolling after welding a composite pipe, the inner surface of the base material pipe and the outer surface of the composite pipe are brought into close contact with each other at both ends of the double base pipe, and the axis of this contact part is The length in the direction is 1/2 or more of the outer diameter of the composite pipe, and the gap between the inner surface of the base material pipe and the outer surface of the composite pipe at the middle part of the double blank pipe other than the close contact part is determined by the diameter difference. 1 of the outer diameter
．． A method for manufacturing pipe clad steel, characterized by using a double base pipe with a content of 4% or less.