JPS5970726A - Clad steel pipe and its production - Google Patents

Abstract

PURPOSE:To provide a clad steel pipe consisting of an external pipe having high strength and an internal pipe having corrosion resistance by irradiating a laser beam to a double pipe which is slowly cooled after cladding and of which the external pipe is heat treated so as to maintain strength, thereby subjecting the surface of the internal pipe to a soln. heat treatment. CONSTITUTION:A tainless steel inside pipe 2 is superposed relatively on an external carbon steel pipe 1 and hot drawn to obtain a clad steel pipe 3 which is then heat treated by hardening and tempering to maintain the strength. The external pipe 1 is imparted with strength by such treatment. The pipe 3 is set on support rolls 6 and a motor 7 is started to rotate and advance the pipe. At the same time, a laser beam irradiation device 12 is started to radiate a laser beam 14 from a gun 13. The beam is reflected by a reflection mirror 11 to irradiate the inside surface of the internal pipe 2 of the pipe 3, thereby the inside surface is melted to undergo solution treatment. The chromium carbide deposited on the pipe 2 is eliminated and the corrosion resistance is restored and maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION The disclosed technology belongs to the field of structural technology for corrosion-resistant double pipes in which the outer pipe is clad with a resistant pipe to be used as oil country tubular goods or the like.

Therefore, the invention of this application is a double steel tube in which an outer tube made of carbon steel or the like is clad with a corrosion-resistant inner tube made of stainless steel, etc. The outer tube is hardened and tempered to ensure strength, and the inner tube is solution-treated. This invention relates to a product that is treated to ensure corrosion resistance and a method for manufacturing the same, and in particular, the double pipe is quenched and tempered after cladding to maintain the strength of the outer pipe. This invention relates to a clad @ tube in which at least the inner surface of the inner tube is solution-treated and rapidly cooled by irradiating a laser beam to ensure corrosion resistance, and a method for manufacturing the same.

As is well known, so-called corrosion-resistant double pipes, in which a corrosion-resistant inner pipe is provided within a pressure- and heat-resistant outer pipe, are widely used as corrosive fluid transport pipes such as oil country tubular goods.

However, if the nuclide double tube is simply an inner and outer tube, there is a gap at the boundary, which may cause misalignment, and thermal expansion requires a large-scale device, and it is difficult to obtain tightness. Therefore, there is a point that the cost is high.

On the other hand, clad steel pipes are widely used because they are hot-treated, have a reliable metallurgical connection between the inner and outer pipes, and are advantageous in terms of facilities.

For example, as shown in FIG. 1, a clad double-pipe steel pipe 3 in which a carbon steel outer pipe 1 is clad with a stainless steel inner pipe 2 is manufactured by hot working such as punching.

By the way, as shown in Fig. 2, when time t is plotted on the horizontal axis and temperature θ is plotted on the vertical axis, the stainless steel inner tube 2 follows a slow cooling characteristic curve B in which the chromium carbide precipitation zone Ae) rubberizes.
There is a problem that chromium carbide precipitates and corrosion resistance deteriorates.

Therefore, when a solution treatment is performed to redissolve the precipitated chromium carbide, it is rapidly cooled as shown in characteristic C, and the precipitated carbide disappears and the corrosion resistance is restored.

However, there is a drawback in that the carbon steel outer tube 1 shown in the characteristics table cannot be subjected to heat treatment such as quenching and tempering, and it is not possible to impart strength functions to the outer tube.

If you apply heat treatment to maintain strength according to the characteristics,
Although the outer tube 1 is given a strength function, the inner tube 2 is attached to the inner tube 2 in order to traverse the chromium carbide precipitation zone A as shown in the figure.
However, there is the disadvantage that chromium carbide precipitates and deterioration of corrosion resistance is unavoidable.

Therefore, the clad double tube cannot satisfy both the corrosion resistance of the inner tube and the strength of the outer tube, and has the disadvantage that one of the functions has to be sacrificed.

The purpose of the invention of this application is to solve the problems of the clad double pipes based on the above-mentioned prior art as a technical problem, to take advantage of the advantages of the clad end pipes, and to maintain the strength function of the outer pipe and ensure the corrosion resistance function of the inner pipe. The purpose of the present invention is to provide an excellent clad steel pipe and a method for manufacturing the same, which can be compatible with the above, and which will benefit the field of corrosion-resistant piping used in various industries.

In order to solve the above-mentioned problems, the invention of this application, which is based on the above-mentioned claims in accordance with the above-mentioned object, is made by laminating a corrosion-resistant inner pipe on a pressure-resistant outer pipe and extruding them by hot working. Both tubes are clad, then subjected to strength preservation heat treatment such as quenching and tempering to give strength to the outer tube.After that, a reflector is set in the inner tube, and the tube body and reflector are rotated and moved in the axial direction relative to each other. A laser beam is applied to the surface of the inner tube and solution treatment is performed through rapid cooling to impart corrosion resistance to the inner tube, thereby fulfilling the strength function of the outer tube and the corrosion resistance function of the inner tube, improving operational reliability. It is a technological measure that has become increasingly popular.

Next, an embodiment of the invention of this application will be described below based on the third drawing. Note that the same parts as shown in FIG. 1.2 will be explained using the same reference numerals.

Support stands 5.5... are set on the base 4 at predetermined intervals, and support rollers 6.6... are provided tilting forward, one of which is connected to a drive motor 7. The heavy steel pipe 3 is supported, rotated, and fed forward at a set speed.

The steel pipe 3 is made by fitting the stainless steel inner pipe 2 into the carbon steel outer pipe 1 as described above, and then hot-working the steel pipe 3 to a predetermined clad length by extrusion forming, as shown in FIG. Since the hot working characteristic B traverses into the chromium carbide precipitation zone A, chromium carbide is precipitated and the corrosion resistance of the stainless steel inner tube 2 is deteriorated.

Therefore, as described above, this is also a material tube which has been heat treated by quenching and tempering as shown in the characteristics table, and has been slowly cooled to give a predetermined strength to the outer tube 1.

After the raw steel pipe 3 is supported by each support roller 6, 6, .

Then, in the set described above, a fully loaded reflector 11 is set on the bracket of the beam 8 near one end of the condenser tube 3.

Father, the gun 13 of the laser beam irradiation device 12, which has been set in advance in the axial position of the beam 8, is directed toward the reflecting mirror 11, and the reflected beam of the beam 14 is directed to the surface of the inner tube 2 of the steel tube 3. It is designed to irradiate the area.

After setting in this manner, when the drive motor 7 is activated and the start switch of the laser beam irradiation device 12 is pressed, a laser beam 14 is emitted from the gun 12, reflected by the reflector 11, and the rotating support rollers 6, 6, . . . - The inner surface of the inner tube 2 of the clad steel tube 3 that is supported and rotates is irradiated, melted, and subjected to solid solution treatment to erase the chromium carbide that precipitated on the stainless steel inner tube 2 during punching hot working, quenching, and tempering strengthening processing. do.

Since the treatment by the laser beam 14 results in traces of fine spot melting, the melted portions at each location must be rapidly cooled as shown in characteristic C in Figure 2, and do not enter the chromium carbide precipitation zone A, so that the above-mentioned The precipitated chromium carbide is dissolved as a solid solution,
Therefore, the corrosion resistance of the stainless steel inner tube 2 is restored and maintained.

In this way, the steel pipe 3 is rotated and moved forward, and the laser beam is applied.The solid solution treatment on the inner surface of the stainless steel inner pipe 2 does not affect the outer pipe 1 because rapid heating and rapid cooling are performed in each part in an extremely short time. , Enhancement of merit: No ability is lost in any way.

When the clad steel surface 3 thus obtained is used, for example, in an oil country pipe, the outer ril will exhibit pressure and heat resistance functions, and the stainless steel inner pipe 2 will be able to sufficiently exhibit corrosion resistance. , it becomes possible to satisfy all the original demands.

It should be noted that the embodiment of the invention of this application is of course not limited to the above-described embodiment, and various embodiments can be adopted, such as rotating the reflecting mirror via a ball screw or the like.

According to the above-mentioned invention of this application, in the method for manufacturing a clad corrosion-resistant double-pipe steel pipe, the strength preservation heat treatment of quenching and tempering is performed on the clad steel pipe material after hot stamping, thereby improving the strength of the outer pipe. It is possible to impart all the strength functions, and then by performing solution treatment using laser beam tracing on the entire inner surface of the inner tube, the precipitation of X chromium carbide is eliminated through rapid cooling while imparting and maintaining the strength functions of the outer tube. However, it is possible to add a corrosion-resistant function, which eliminates the disadvantages of clad steel that had to sacrifice one of its functions, and makes it possible to provide both functions while fully utilizing the inherent advantages of clad steel pipe. Excellent effects that can be used in

Furthermore, all the quenching and tempering operations for the outer tube can be performed using conventional methods.

The solid solution treatment for the inner tube is performed by a laser beam, resulting in rapid heating and rapid cooling, which provides an excellent effect of imparting corrosion resistance to the outer tube without any thermal influence.

In the corrosion-resistant clad steel pipe obtained in this way, the inner and outer pipes are completely metallurgically bonded, so there is no interfacial delamination, no interfacial corrosion, no shearing, etc., which is unique to clad steel pipes. In addition to its high quality, the pressure and heat resistance of the outer tube is reliably guaranteed, while the inner tube has sufficient corrosion resistance against flowing corrosive fluids, making it an excellent product that can fully utilize its function as a corrosion-resistant tube. The effect is diminished.

[Brief explanation of the drawing]

Figure 1 is a partial cross-sectional view of a clad corrosion-resistant double-pipe steel pipe, Figure 2 is a graph explaining the heat treatment time and temperature characteristics of the clad steel pipe,
FIG. 3 is a partially cutaway perspective view illustrating the solution treatment of one embodiment of the invention of this application. 1...Outer tube, 2...Inner tube, 14...
・Laser beam, 3... Clad steel pipe

Claims (2)

[Claims] (1) In a steel pipe in which the outer pipe is clad with a corrosion-resistant inner pipe, the outer pipe is heat treated to maintain its strength, while at least the inner surface of the corrosion-resistant inner pipe is solution-treated. clad at. (2) In a manufacturing method for obtaining a corrosion-resistant clad inner tube by cladding the outer tube with a corrosion-resistant inner tube by hot treatment, then subjecting the outer tube to strength preservation heat treatment and solution treatment to the inner tube, A double tube whose cooled outer tube is heat treated to maintain its strength, and a laser beam is irradiated all over the surface of the inner tube to apply solution treatment to at least the surface of the inner tube. Method of manufacturing steel pipes.