JPH1172293A - Tube with fin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tube with a fin which improves performance and durability as heat exchanger tube by preventing the generation of ash erosion near a weld part between the fin and the tube to upgrade wear resistance in the tube with the fin which has a high temperature gas flowing outside it. SOLUTION: In a tube with a fin in which the fin 2 comprising a sheet is wound on the outer circumference of the tube 1 to let a gas flow outside it, the tube 1 and the fine 2 are welded only within a specified range on the circumference on the side opposite to the side facing the flow of the gas and the welding of other parts is eliminated. The materials of the tube 1 and the fin 3 are composed of materials with at least the thermal expansion coefficient thereof almost equal to each other thereby preventing a drop in the wear resistance of the weld part 3 as caused by contact with a high temperature gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finned tube welding structure used for a heating section of a boiler, various heat exchangers, and the like.

[0002]

The heat transfer tube used for the heating section of the boiler is a tube with a fin formed by spirally winding a thin fin around the tube through which water or steam flows. Have been. Due to its shape, the boiler finned tube has low abrasion resistance particularly at the root of the fin, and is used for heating combustion gas or the like flowing outside the tube with the fin at the root, that is, the welded portion between the fin and the tube. Ash (ash) due to the gas is apt to deposit, which causes ash erosion, and the ash root causes thinning at the root of the fin.

[0003] In order to prevent the above-mentioned ash erosion at the root of the fin, the means for improving the wear resistance by hardening the material of the tube by heat treatment at the time of component design or production has been proposed. ing. However, in such means, when the fin is bonded to the outer periphery of the tube, a joint (weld) between the fin and the tube is formed.
Due to the heat input in the vicinity, there is a problem that the metal structure of this portion changes, and it is difficult to obtain sufficient performance and durability as a heat transfer tube.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a finned tube through which a high-temperature gas flows, to prevent the occurrence of ash erosion in the vicinity of a joint between the fin and the tube, to improve abrasion resistance, to improve performance as a heat transfer tube, An object of the present invention is to provide a finned tube having improved durability.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the gist of the invention is to form a thin fin around the outer periphery of a tube and allow gas to pass through the outside. In the finned tube that flows, the tube and the fin are welded only within a predetermined range on the circumference on the side opposite to the side facing the gas flow, and the welding of other parts is omitted. The material of the fin and the material of the fin are at least composed of materials having substantially equal thermal expansion coefficients.

According to the above means, the tube and the fin are not welded at a portion which comes into contact with a high-temperature gas, but are welded and joined only at a portion which is not in contact with the gas. Even if high-strength steel having heat resistance is used as the tube material, the welded portion is not softened by the high-temperature gas and the wear resistance does not decrease, and the high wear resistance can be maintained even under the flow of the high-temperature gas. . As a result, the occurrence of thinning of the welded portion due to ash erosion can be suppressed.

Further, since the material of the fin is made of a material having a thermal expansion coefficient substantially equal to that of the tube, there is almost no difference in thermal expansion between the fin and the tube, and the non-welded portion is peeled off due to the difference in thermal expansion. Is prevented from occurring.

It is preferable that the material of the fin has substantially the same thermal expansion coefficient as the material of the tube, and has substantially the same thermal conductivity.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 is an external perspective view of a boiler finned tube according to an embodiment of the present invention,
FIG. 2 is a side view of the finned tube, and FIG. 3 is a view taken in the direction of arrow A in FIG. FIG. 4 is a cross-sectional view of a main part of a welded joint of the tube with a fin, and FIG.

1 to 4, reference numeral 1 denotes a tube through which water or steam flows. Reference numeral 2 denotes a fin made of a thin plate, which is spirally wound around the outer periphery of the tube 1 by means described later.

In the embodiment of the present invention, as shown in FIG. 3, the outside of the tube with the fin is substantially perpendicular to the axis of the tube 1 as shown in FIG. The welding of the portion facing the gas on the circumference, that is, the portion that comes into contact with the gas, is omitted from the flow of the gas flowing through the tube. 2
And welded joints. Reference numeral 3 denotes the welded portion. The above range: θ is preferably half the circumference, that is, about 180 °.

As a material for the tube 1, a non-tempered high-strength steel whose tempering and cooling rate during production are sufficiently controlled has high hardness and wear resistance, and is advantageous in terms of cost. This is one of the suitable materials. The material of the fin 2 is made of a material having substantially the same thermal expansion coefficient and thermal conductivity as that of the tube 1 in order to prevent the portion not welded to the tube 1 from being peeled off (at least the thermal expansion coefficient of the tube 1 is lower than that of the tube 1). It must be almost the same material).

When high-tensile steel is used as the material of the tube 1, the joint between the tube 1 and the fin 2 is softened at the weld 3 as shown in FIG. 4 when exposed to a high-temperature gas. The wear resistance is reduced, the required performance as a heat transfer tube cannot be exhibited, and the durability is easily reduced.

Therefore, in the embodiment of the present invention, the welding at the portion that does not come into contact with the high-temperature gas is omitted, and the welding is performed only at the portion that does not come into contact with the gas, that is, in the range of θ described above. Abrasion resistance is prevented. The material of the fin 2 is a tube 1
Since the thermal expansion coefficient and thermal conductivity of the material are almost the same,
There is no difference in thermal expansion between the tubes 1 and the fins 2 in the portions that are not welded, so that separation of the tubes 1 and the fins 2 due to the difference in thermal expansion is also avoided.

FIG. 5 shows a case where the welding of the tube 1 and the fin 2 according to the embodiment of the present invention is performed only for a half circumference (the above θ = 180 °) not in contact with the gas (FIG. FIG. 7 is a comparison diagram of the amount of wear reduction due to ash erosion with that obtained by performing the welding over the entire circumference (FIG. 5B). As is clear from the figure, the welded type (A) as in the embodiment of the present invention has a smaller amount of the above-mentioned wall thickness reduction and higher wear resistance than the conventional type (B).

[0016]

The present invention is configured as described above.
According to the present invention, in joining the tube and the fin,
By omitting welding at the part that contacts the high-temperature gas and welding only at the non-contact part with the gas, the welded part is softened by the high-temperature gas and the wear resistance does not decrease,
It becomes possible to use a high-tensile steel having a high wear resistance at a relatively low temperature for a tube, and to maintain a high wear resistance even under the flow of a high-temperature gas. Thereby, the occurrence of wall thinning due to ash erosion in the welded portion is suppressed. In addition, since the fin is made of a material having a coefficient of thermal expansion substantially equal to that of the tube, there is almost no difference in thermal expansion between the fin and the tube, and separation between the fin and the tube due to the difference in thermal expansion is prevented. . Therefore, according to the present invention,
Abrasion resistance is large, performance and durability as a heat transfer tube are improved, and a low-cost finned tube can be obtained.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a boiler finned tube according to an embodiment of the present invention.

FIG. 2 is a side view of the finned tube.

FIG. 3 is a view taken in the direction of arrow A in FIG. 2;

FIG. 4 is a sectional view of a main portion of a welded joint of the finned tube.

FIG. 5 is a comparison diagram of a wear thinning amount of a joint.

[Explanation of symbols]

 1 Tube 2 Fin 3 Weld

Claims (1)

[Claims] 1. A finned tube formed by winding a fin made of a thin plate around an outer periphery of a tube and allowing gas to flow outside, wherein the tube and the fin are opposite to a side facing the gas flow. Welding is performed only within a predetermined range on the side circumference to omit welding at other parts, and the material of the tube and the material of the fin are made of a material having at least a substantially equal coefficient of thermal expansion. Tube with fins.