JP4248058B2 - Abrasion resistant metal tube and method of manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal tube excellent in wear resistance and a method for manufacturing the metal tube.
[0002]
[Prior art]
Steel pipes may require excellent wear resistance on the inner and outer surfaces depending on the application. To improve wear resistance, conventional steel pipes are hardened, thermally sprayed, or rotationally lined to provide metal-based wear resistance. Metallurgical processes such as forming a coating have been adopted.
[0003]
[Problems to be solved by the invention]
However, if the steel pipe is hardened, the wear resistance is improved, but there is a risk of cracking during welding joining. For this reason, a flange is welded to the pipe end, or the pipe ends are joined together by welding. There was a problem that it was difficult to work. In addition, even when a metal wear-resistant coating such as a self-fluxing alloy is formed, there is a possibility that the wear-resistant coating may break during welding joining, and there is a problem that welding work becomes difficult.
[0004]
In addition, when manufacturing a steel pipe with a flange, the flange is welded and joined to the steel pipe in advance, and the steel pipe with the flange is hardened or formed with a wear-resistant coating, thereby providing excellent wear resistance. It is possible to produce a flanged steel pipe. However, the quenching operation for the flanged steel pipe and the operation for forming the wear-resistant coating are difficult to achieve high efficiency, resulting in high costs.
[0005]
The present invention has been made in view of such problems, and is a wear-resistant metal tube that can be welded to the pipe end and has the necessary wear resistance on the inner surface of the tube or the outer surface or the inner and outer surfaces of the tube. And it aims at providing the manufacturing method.
[0006]
[Means for Solving the Problems]
Wear-resistant metal tube of the present invention is to allow the weld joint at the pipe end, the metallurgical process for improving the wear resistance, such as the formation of metallic-based wear-resistant coating, thermal effects of welding of the tube end This is applied to the central part of the tube, excluding the area where it receives a large amount, and a thin section with a larger wall thickness than the central part of the tube is provided in the small section including the pipe end to compensate for the thickness reduction due to wear. It is what.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The wear-resistant metal tube according to the present invention is a tube center portion sandwiched between the small sections by subjecting the pipe body to a thickening process in the small sections including the pipe ends of both ends of the metal tube. A region excluding a region that is provided with a thickened portion having a larger thickness than the central portion of the tubular body and having a large thermal effect during welding at the end of the tube, and includes at least the tubular central portion The inner surface of the tube or the outer surface of the tube or the inner and outer surfaces of the tube are subjected to a wear-resistant coating treatment . Here, the thick portions provided at both end portions of the tube may have a shape that protrudes inside or outside the tube, or may have a shape that protrudes only on one of the inside and outside of the tube. The pipe used for the wear-resistant metal pipe is usually a steel pipe, but other metal pipes that can be welded may be used. The form of the tube is arbitrary, such as a cylindrical shape or a rectangular tube shape, and may be either a straight tube or a bent tube. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0008]
FIG. 1 is a schematic cross-sectional view showing a wear-resistant metal tube (hereinafter abbreviated as a metal tube) 1 according to an embodiment of the present invention, which is used for fluid transportation that easily wears the inner surface of a tube body such as slurry. FIG. 2 is an enlarged schematic sectional view showing the vicinity of the pipe end of the metal pipe 1. The metal pipe 1 has a pipe body 2 made of a steel pipe. The pipe body 2 includes a pipe center portion 2a having a constant thickness, and a small section (long) including pipe ends at both end portions of the pipe body 2. A thick section 2b having a thickness larger than that of the tube central portion 2a sandwiched between the small sections is provided in the small section indicated by the length L. A metal-based wear resistant coating 5 is applied to the inner surface of the tube center portion 2a of the tube body 2 as a metallurgical treatment for improving wear resistance. Depending on the use of the metal pipe 1, when the outer surface is required to have wear resistance (for example, when the metal pipe is laid in a desert or the like and the outer surface is exposed to sandstorms or the like and is easily worn, the metal pipe is subjected to heat exchange. In such a case, a wear-resistant coating is provided on the outer surface of the tube central portion 2a. When the inner and outer surfaces of the metal tube are required to have wear resistance, the wear resistant coating is naturally provided on both the inner and outer surfaces of the tube central portion 2a.
[0009]
As shown in FIG. 3, the thick portion 2 b provided at the pipe end of the pipe body 2 is welded to the flange 7 with the weld metal 8, or the pipe ends are abutted with each other as shown in FIG. 4 and welded with the weld metal 9. It is used for joining, and hardening treatment such as quenching is not performed so as not to cause troubles such as cracks during welding. For this reason, although this thick part 2b is easy to wear, the required service life is ensured by enlarging the thickness. In other words, the thickness t of the thick portion 2b in FIG. 2 is that the metal tube 1 is used over a preset service life (for example, 3 years), and the inner surface of the tube is worn by the fluid flowing inside. In addition, the thickness is set such that a necessary strength can be secured (usually equal to the thickness t ₀ of the tube central portion 2a). Although this wall thickness t varies depending on the set service life, in general, from the balance between the life extension merit and the cost of the wall thickness increasing process, the wall thickness t ₀ of the tube body central portion 2a is 1.2 to It is preferable to set to about 3 times. The section length L of the thick-walled portion 2b is determined so that the heat effect during the welding operation on the pipe end does not greatly affect the wear-resistant coating 5 and the wear-resistant coating 5 does not cause troubles such as cracks. It is preferable to select about 25 to 150 mm.
[0010]
The wear-resistant coating 5 is provided in order to improve the wear resistance of the tube body 2, and naturally, a material having higher wear resistance than the tube body 2 is selected. Specifically, examples of the wear-resistant coating 5 include a self-fluxing alloy coating such as a Ni base or a Co base, or a coating obtained by mixing the self-fluxing alloy with a ceramic such as tungsten carbide. The formation position of the wear-resistant coating 5 is at least a thin tube central portion 2a. However, if necessary, the thick portion 2b is not subjected to a crack or the like under the influence of the welded joint of the tube end. You may form in the range of thickness. The thickness t ₁ of the wear-resistant coating 5 is such that the desired service life of the metal tube 1 can be ensured (for example, the wear-resistant coating 5 is worn out by use of the desired number of years and the tube central portion 2a It is determined to be slightly larger than the expected wear amount so that the wear of the pipe body does not start. Specifically, although it depends on the inner diameter, thickness, etc. of the pipe body 2, both the service life and workability are combined. It is preferable to set it to about 0.5 to 5 mm from the beginning, and in relation to the wear resistance of the tube, the ratio to the wall thickness of the tube center portion 2a should be selected to be about 0.1 to 0.5. preferable.
[0011]
As described above, since those determined in consideration of the service life even thickness t of the thick portion 2b is set to the thickness t ₁ is also both a metal tube 1 of wear-resistant coating 5, the thickness of both respectively It can also be determined from the wear rate of the following. That is, the wear rate of the wear-resistant coating 5 made of a self-fluxing alloy is assumed to be about 1/4 of the wear rate when the thick portion 2b is not quenched with normal steel. The increase in thickness (= t−t ₀ ) may be about four times the thickness t ₁ of the wear-resistant coating 5. For example, when the thickness t ₀ of the tube central portion 2a is 4 mm and the thickness t ₁ of the wear resistant coating 5 is 1 mm, the increase in thickness of the thick portion 2b is the thickness of the wear resistant coating 5. The thickness t ₁ may be four times, that is, about 4 mm. Therefore, the thickness t of the thick portion 2b may be 8 mm (twice the original thickness). More generally, assuming that the wear rate of the wear resistant coating 5 is 1 / n of the wear rate of the thick portion 2b, the thickness t of the thick portion 2b is equal to the thickness t ₁ of the wear resistant coating 5. On the other hand, the following equation may be determined as a guide.
t = t ₀ + nt ₁ (1)
[0012]
In FIG. 2, the thick portion 2b formed at the tube end of the tube body 2 has a shape that protrudes into and out of the tube, but the present invention is not limited to this, and may have a shape that protrudes only to one inside or outside the tube. In the case where the thick part 2b is projected on the side where the wear-resistant coating 5 is formed, the protruding height of the tubular body accompanying the increase in thickness is set to the film of the wear-resistant coating 5 with respect to the surface on which the coating is applied. It is preferable that the thickness be greater than or equal to the thickness increase of the thick portion 2b. With this configuration, the protruding height of the inner surface of the thick part 2b at the start of use is prevented from becoming extremely large, or the dent on the inner surface of the thick part 2b due to wear after long-term use is prevented from becoming extremely large. And has the advantage that adverse effects on the flow in the tube are avoided. Moreover, it is preferable to provide the taper part 2c which thickness increases gradually from the tube center part side at the side which touches the tube center part 2a of the thick part 2b. Providing such a tapered portion 2c makes it difficult for the flow in the tube to be disturbed, and there is no region in which the strength and rigidity of the tube changes suddenly, thereby providing the advantage of preventing stress concentration in the tube.
[0013]
Next, a method for manufacturing the metal tube 1 having the above configuration will be described. First, a steel pipe having a constant thickness t ₀ is prepared, and thickening processing is performed on both ends thereof to form the thick portion 2b. This thickening process may be performed either hot or cold, but adopting a hot upset thickening process can reduce the compression force for the process, and thus the size of the compression device can be reduced. This is preferable because the residual stress can be reduced. Here, the hot upsetting process is to heat the region to be processed to a temperature at which plastic deformation is easy (usually above the red hot temperature, for example, about 900 to 1300 ° C. is preferable for a steel pipe). This is a method of increasing the thickness by applying a compressive force in the tube axis direction. As specific methods of this hot upsetting process, the following three methods can be mentioned, and any of them may be adopted.
[0014]
(1) Continuous hot upsetting process method As shown in FIG. 5, this method supports one end of a tubular body 2, which is a steel pipe to be increased in thickness, with a support member 10, and presses a pressing device ( In a state in which a compressive force in the tube axis direction indicated by arrow F is applied to the tube body 2 by the induction coil 12, the narrow width section 11 of the tube body 2 is heated by the induction coil 12 to a temperature at which plastic deformation is easy. The induction coil 12 is continuously moved relative to the tube body 2 in the direction of the arrow A, and the cooling medium 13 is sprayed on the portion immediately after the rear wall thickness increase to cool and solidify the tube body 2 continuously. In this method, the thickness is increased to form a thick portion 2b having a desired length. In this continuous type, stable wall-thickening processing is possible even in a free state where the inner and outer surfaces of the tube body 2 are not restricted by a mold tool, and a thick portion protruding substantially in the same manner can be formed on the inner and outer surfaces. In addition, what is necessary is just to regulate either the inner or outer surface with a tool, when it is desired to regulate the protruding amount to the inner and outer surfaces of the tubular body.
[0015]
(2) Sequential hot upsetting thickening method This method heats a narrow-width section in the region to be processed of the tube to be thickened to a temperature at which plastic deformation is easy, and compresses in the tube axis direction. Applying force to increase the thickness of the section to form a thick section, and after the thick section cools and solidifies, the adjacent section is heated to a temperature at which plastic deformation is easy and compressive force is applied to the section. This is a method of forming a thick part having a desired length by repeating the action of increasing the thickness by acting. Even with this sequential type, stable wall-thickening processing is possible even in a free state where the inner and outer surfaces of the tube are not regulated by a mold, and when it is desired to regulate the amount of protrusion to the inner and outer surfaces of the tube, the inner and outer surfaces Any of these may be regulated by a tool.
[0016]
(3) One-shot hot upset processing method This method heats the entire region of the tube to be processed to a temperature where plastic deformation is easy, and applies a compressive force in the direction of the tube axis to increase the whole at the same time. It is a method of forming a thick part by making it thick. In the one-shot type, in order to perform stable wall-thickening processing without causing buckling or the like, a mold that normally regulates one or both of the inner and outer surfaces of the tube is used.
[0017]
As described above, the tube body 2 is thickened to form the thick portions 2b at both ends, and then the vicinity of the end of the thick portion 2b is cut to shape the tube end (this operation) May be performed after the coating formation described later). Next, the wear-resistant coating 5 is formed on the tube center portion 2a sandwiched between the thick portions 2b at both ends. A known technique can be used as appropriate for forming the wear-resistant coating 5, and a method suitable for the material forming the wear-resistant coating 5 may be employed. For example, in order to form the wear-resistant coating 5 made of a self-fluxing alloy or a self-fluxing alloy containing ceramic, a thermal spraying method, a rotational lining method, or the like can be used. Here, the rotational lining method refers to supplying powder metal for forming an abrasion-resistant coating on the inner peripheral surface of the tube body 2 while rotating the tube body 2 and heating the tube body 2 so that the powder metal is applied to the inner surface of the tube body. It is a method of attaching and forming a coating. For the coating with a self-fluxing alloy formed by a thermal spraying method, a rotational lining method, or the like, it is preferable to remelt the self-fluxing alloy so as to eliminate the pores and to ensure the bonding to the base material. In the case of adopting the rotational lining method, adopting the methods described in Japanese Patent Publication No. 5-471, Japanese Patent Publication No. 5-33307, and Japanese Patent No. 2727450 Formation and subsequent remelting treatment are preferably performed in one step, and a dense wear-resistant coating 5 without pores can be formed with good productivity.
[0018]
The metal tube 1 shown in FIG. 1 is manufactured as described above. As shown in FIG. 3, the metal tube 1 having this configuration is used as a flanged metal tube with a flange 7 welded to the end thereof. Further, as shown in FIG. 4, the pipe ends can be directly butted and welded together. In any use, it is possible to weld and join the thick-walled portion 2b at the end of the pipe that has not been subjected to the quenching or the like without causing any trouble, and the piping work is facilitated. Moreover, if the thick part 2b is lengthened, a part of the thick part 2b at the pipe end can be cut off at the piping construction site, and the total length of the metal pipe 1 can be adjusted according to a desired mounting length. Workability is further improved.
[0019]
During the use of the metal tube 1, wear occurs on the inner surface of the metal tube due to the fluid flowing inside, and since the treatment for improving the wear resistance is not performed in the thick portion 2 b, the wear amount increases. Since the thickness of the portion 2b is increased, the necessary thickness can be ensured even if the wear is large. For this reason, the thick part 2b can also ensure the service life similar to the tube center part 2a which forms the abrasion-resistant coating | cover 5, and can be used without trouble over the desired years.
[0022]
FIG. 6 shows an embodiment in which the present invention is applied to a bending tube, and the metal tube 1B has a tubular body 2 having a straight tube portion at both ends and a bent portion at the central portion. The tubular body 2 in this embodiment is also formed with a thick portion 2b in a portion that is excessively affected by heat when welding the pipe end, and the tubular central portion 2a between the thick portions 2b and 2b at both ends is a wall portion. The thickness remains thin. Then, the inner surface of the tube the central portion 2a, that form a wear-resistant coating 5 as metallurgical process for improving the wear resistance. Also metal tube 1B of this configuration in the same manner as the metal tube 1 shown in FIGS. 1 to 4, Toka used as a metal tube flanged by welding the flange to the end portion, abutting the tube end comrades, and welding used.
[0023]
Next, a method for manufacturing the metal tube 1B having a bent portion will be described. First, in the same manner as the production of the straight tubular metal tube 1, the thickened portion 2 b is formed by increasing the thickness at both ends of a straight steel tube having a constant thickness, and then the inner surface of the steel tube is coated with wear resistance. 5 is formed. Thereafter, the metal tube is bent. As a bending method, a known method may be used as appropriate, but among them, it is preferable to employ a continuous hot bending method using induction heating shown in FIG . In this continuous hot bending method, as shown in FIG. 7 , the bending tip side of the tube body 2 to be bent is gripped by a bending arm 23 that can pivot about a fulcrum O, and the longitudinal direction of the tube body 2 The small region 24 is induction-heated to an easily plastically deformable temperature (for example, red hot temperature) by the induction coil 25, and the tube 2 is continuously pushed in the direction of arrow B, thereby turning the bending arm 23 and heating the small region 24. This is a method in which a bending moment is applied to the region 24 to cause bending deformation, and at the same time, a cooling medium 26 such as cooling water is sprayed from the induction coil 25 to a portion immediately after the bending deformation to cool and solidify. There is an advantage that bending of a desired bending angle can be easily performed.
[0024]
Since the tube is heated to a high temperature during the continuous hot bending process, depending on the setting of the heating temperature, the wear resistant coating 5 of the self-fluxing alloy formed on the inner surface of the tube is remelted. It is also possible. Therefore, when manufacturing the metal tube 1B having the self-fluxing alloy wear-resistant coating 5 to be subjected to bending, the self-fluxing alloy wear-resistant coating 5 is formed on the inner surface of the straight tubular body. However, the remelting process may be completed, but the melting process is not performed, the coating in the sintered state is formed simply by thermal spraying or rotary lining, and the tube body is subjected to the continuous hot bending process simultaneously with the bending process. A method of remelting the coating to eliminate pores in the coating to obtain a dense wear-resistant coating 5 (see Japanese Patent No. 2607078) can also be employed. If this method is adopted, the process can be simplified and the cost can be reduced.
[0026]
In the metal tube 1B of the embodiment shown in FIG. 6 , the thick portions 2b at both ends are straight tube portions and the tube center portion 2a is a bent portion, but a part of the thick portion 2b is also a bent portion. Toka change in the up part of the subsequent thick portion 2b tube central portion 2a may be modified to a straight pipe portion such as a metal tube 1C shown in FIG. However, if the bending apparatus shown in FIG. 7 is used as a bending process for manufacturing the metal tube 1C having the configuration shown in FIG. 8 , and the remelting process of the inner coating 5 is performed simultaneously with the bending process, the apparatus shown in FIG. Then, it is not possible to perform the remelting process of the coating 5 on the portion that becomes the straight tube portion in the tube central portion 2a. Therefore, in this case, it may be employed a method shown in Figure 9 (a).
[0027]
That is, as shown in FIG. 9 , the induction coil 25 is made movable in the tube axis direction . First, as shown in FIG. 9A , the tubular body 2 is set on the bending arm 23 and is stationary. The induction coil 25 is moved from the inner end portion of the thick portion 2b along the tube center portion 2a constituting the straight tube portion as indicated by an arrow C, and re-melting treatment of the covering 5 of the portion is performed, When the induction coil 25 reaches the bending reference line OP, the induction coil 25 is stopped as shown in FIG. 9B, and at the same time, the tube body 2 is advanced in the direction of arrow B to start bending. Bending and remelting the coating. Then, as shown in FIG. 9 (c), when the bending of the predetermined range of the tube body 2 is completed, the movement of the tube body 2 is stopped, and the induction coil 25 is connected to the straight tube portion as indicated by an arrow C. Is moved along the tube central portion 2a, and the coating 5 of the portion is remelted. By the above operation, the coating 5 over the entire length of the central portion 2a of the tubular body extending to the bent portion and the straight pipe portions on both sides thereof can be remelted.
[0028]
【The invention's effect】
As described above, the wear-resistant metal tube of the present invention, the metallurgical process for improving the wear resistance, such as the formation of metallic-based wear-resistant coating, excluding the larger receiving area influence of heat during welding of the pipe end By applying to the inner surface of the tube or the outer surface of the tube or the inner and outer surfaces of the tube at the center portion of the tube body, a small section including the tube end is provided with a thick portion that is thicker than the tube center portion. Can be welded to the pipe end without hindrance, and can be used as a flanged metal pipe by welding the flange or by joining the pipe ends together and welding. Even when the thick wall is worn during use, the wall thickness is large, so the necessary wall thickness can be secured over the same period as the central part of the pipe subjected to wear resistance treatment, and the service life is extended. Has the effect of being able to . Metal pipes that have been subjected to wear resistance treatment on the inner surface side of the pipe body are excellent in wear resistance against fluid flowing inside, so that a slurry containing solid particles (for example, a slurry containing concrete, water granulated powder, coke, ceramic, etc.) Suitable for transportation.
[0029]
In the manufacturing method of the present invention, a thick wall portion is formed by performing hot upsetting and thickening processing at both ends of a pipe body such as a steel tube having a constant thickness, so that a pipe having thick wall portions at both ends at low cost. Since the body can be manufactured and the thick wall part and the central part of the tube sandwiched between the parts are completely integrated, there is no reduction in strength due to the seam, uneven quality, etc. A stable tubular body can be manufactured, and eventually, there is an effect that a wear-resistant metal tube having stable strength and quality can be manufactured at low cost.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a wear-resistant metal tube according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an enlarged vicinity of a tube end of the metal tube of FIG. FIG. 4 is a schematic cross-sectional view showing a state in which a flange is joined to the end of a pipe. FIG. 4 is a schematic cross-sectional view showing a state in which the end of the metal pipe in FIG. FIG. 6 is a schematic cross-sectional view showing a wear-resistant metal tube according to another embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing a state in which continuous hot bending is applied to the pipe body . 8 is a schematic cross-sectional view showing a wear-resistant metal tube according to still another embodiment of the present invention . FIG. 9 (a), (b), and (c) manufacture the metal tube shown in FIG. Schematic cross-sectional view explaining the continuous hot bending process [Description of symbols]
1, 1B, 1C Abrasion resistant metal tube (metal tube)
2 Tubing 2a Tubing central part 2b Thick part 5 Wear-resistant coating 7 Flange 8, 9 Weld metal 10 Support member 12 Induction coil 13 Cooling medium 23 Bending arm 25 Induction coil 26 Cooling medium

Claims (6)

Thick parts that are thicker than the central part of the tubular body sandwiched between the small sections by subjecting the tubular body to thickening processing in the small sections including the pipe ends of both ends of the metal tubular body Is provided in an integral structure with the tube center portion, and is a region excluding a region that is greatly affected by heat at the time of welding of the tube end and at least the region including the tube center portion, the tube inner surface, the tube outer surface, or the inner tube A wear-resistant metal tube characterized in that the outer surface is subjected to a wear-resistant coating treatment .   The wear-resistant metal tube according to claim 1, wherein the thickness of the thick portion is 1.2 to 3 times the thickness of the central portion of the tubular body.   The wear-resistant metal tube according to claim 1 or 2, wherein a section length of the thick part is 25 to 150 mm. Previous KiAtsu meat portion, the protruding height of the thickening in the accompanying tube, said coating alms side than the thickness of the coating with respect to the surface, and the less the thickness increase of the thick portion, claim The wear-resistant metal tube according to any one of 1 to 3.   The wear-resistant metal according to any one of claims 1 to 4, wherein a taper portion in which the wall thickness gradually increases from the tube central portion side is provided on a side of the thick portion that contacts the tube central portion. tube.   The method for manufacturing a wear-resistant metal tube according to any one of claims 1 to 5, wherein the thick part is formed by hot upsetting and thickening.

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