JP2002283057A - Sintered material weld joint, and welding method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize welding which makes good use of advantages of a sintered material weld joint that re-welding is unnecessary after welding because a weld zone is less heat-affected when fitting a joint such as a flange to connect a pipe to the pipe by welding, and any complicate shape can be manufactured at one stroke and which covers disadvantages of the sintered material weld joint that the fatigue strength of the weld zone is low, and cracks are propagated from a stress-concentrated part if cyclic stresses are exerted therein, and easily leading to the fatigue. SOLUTION: By using a sintered material weld joint in which a groove part is constituted of tapered surfaces, the angle of inclination (β) to the sectional surface is 20-60 deg., and the thickness (a) of a joint at the groove end is <=1.5 times the wall thickness (d) of the pipe, the penetration having the sectional shape in which the crack propagating direction is directed to the inside of the weld metal when cracks are caused due to stress concentration after welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered material welded joint made of a sintered material of metal powder and having a specific groove, a welding method performed by using the joint, and a method obtained by performing the method. It also relates to the welds that are made.

[0002]

2. Description of the Related Art When two pipes made of stainless steel are connected, for example, a joint material is welded to the pipe to form a flange, and the flange is further welded, bolted, or bonded. In most cases, first, a flange is formed by welding.

[0003] As a method of manufacturing a welded joint represented by this type of flange, stamping and forging is efficient, but the shape of a joint that can be manufactured by stamping and forging is limited. Therefore, joints are also manufactured by sintering metal powder, which gives a higher degree of freedom in the shape of the product and makes it easier to obtain a product having a complicated shape. Since the sintered material has a lower specific gravity than the ingot material, it contributes to weight reduction.

[0004] When a joint is welded to a metal product to be connected, there is a problem in that the dimensions and shape of the joint are disordered due to heat. In the case of a pipe flange, the flatness of the joint surface is reduced, and in many cases, it is necessary to cope with this by performing post-processing such as cutting. This problem can be substantially eliminated by lengthening the tubular portion of the flange so that the thermal effect of the weld is less likely to reach the flange. If a sintered material is used, such shaping can be easily performed, so that cutting can be omitted. On the other hand, when attempting to produce a flange by forging from an ingot, there is a limit to the length of the tubular portion, and it is not possible to avoid thermal effects. For this reason, sintered materials are favorably used in the production of welding joints such as flanges.

[0005] Sintered materials, however, have a weak point of low fatigue strength. When connecting a pipe by welding a sintered material flange to a pipe made of ingot material, if stress is repeatedly applied to the connection part, cracks will occur at the stress concentration part of the sintered material even if the load is not so large However, there is a danger that it will propagate inside the sintered material having low fatigue strength and eventually lead to a total breakage.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems associated with the use of a joint made of sintered material by welding, and to provide a welded part having a high fatigue strength. It is to provide a sintered material welded joint having a groove.
It is also an object of the present invention to provide a welding method using this joint and to provide a welded portion obtained by performing the method.

[0007]

A sintered material welded joint according to the present invention, which achieves the above object, is obtained by sintering a metal powder and using it by welding to ends of metal products connected to each other. The joint is characterized in that when a crack is generated due to stress concentration after welding, the joint has a shape that gives a welded portion such that the direction of propagation is directed toward the inside of the weld metal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is defined in terms of a groove to be subjected to a welding operation. The groove of the present invention is used by welding the ends of metal products to be connected to each other. In a groove formed from a sintered material welded joint, when a crack occurs due to stress concentration after welding, it has a groove shape that gives a welded part whose growth direction goes to the inside of the weld metal. And

According to the method for welding a joint of the present invention, the above-mentioned sintered material welded joint is combined with the end of a metal product which is also connected to each other with the above-mentioned groove shape, and an angle and a target position of a welding torch are selected. By doing so, when a crack is generated due to stress concentration after welding, penetration having a cross-sectional shape such that the direction of propagation is directed toward the inside of the weld metal is realized.

[0010] The welded portion of the joint of the present invention thus obtained is obtained by welding the above-mentioned sintered material welded joint to the end of a metal product which is also connected to each other with the above-mentioned groove shape. And having a cross-sectional shape such that when a crack is generated due to stress concentration after welding, the direction of growth is directed toward the inside of the weld metal.

Referring to the drawings, the present invention will be described in comparison with the prior art, taking as an example a typical example of welding a sintered material joint to a pipe. Conventionally, a flange (1A) having a cross-sectional shape as shown in FIG. Was held at about 45 degrees to perform welding. In this case, the formed weld metal (3A) has a cross section as shown by the hatched portion in FIG. When stress acts between the pipe and the flange, the stress concentrates at the point (S1) in FIG.
The fatigue crack propagates from this point in the direction of the arrow in the sintered body.

In the welding of the present invention, a flange (1B) having a sectional shape as shown in FIG. 3 is formed so that the torch angle α of the welding torch (4) with respect to the pipe (2) is 60 to 70 degrees. Hold and weld. Flange (1B)
As shown in FIG. 3, the groove portion has a tapered surface. The inclination angle (β) of the tapered surface with respect to the cross section of the pipe is set to 20 to 60 degrees, preferably 50 degrees, and the thickness (a) of the open end is 1.5 times the wall thickness (d) of the pipe. Within the range, preferably 0.3 to 1.0 times.

The weld metal (3B) formed at this time is
It has a cross section as shown by the hatched portion in FIG. In the case of such penetration, the stress concentrates at the welded portion at the point indicated by the symbol (S2), and the fatigue crack starting from this point should grow in the direction of the arrow, but the fatigue strength in that direction is Cracks do not develop because of the weld metal rather than the low sinter. This is the mechanism by which the fatigue strength of the welded portion can be increased in the present invention.

When the joint of the present invention is a flange, the cross-sectional shape thereof is not limited to the shape shown in FIG.
It may be something like The point is to provide a groove shape suitable for realizing the penetration of the cross section as shown in FIG. In order to achieve this object, it is possible to adopt a method of performing "tanning" in advance on a groove portion of the joint to provide a fusion part before welding the joint to the metal product.

The metal to be subjected to welding of the present invention is arbitrary, but a typical example of stainless steel is as follows.
SUS304, 430, and 419. The metal product to which the joint is welded is not limited to the ingot material but may be a sintered material. There is no particular limitation on the welding means, but MIG welding commonly used for this type of welding is optimal.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In carrying out the present invention, the physical properties related to welding necessary to realize the shape of a "welded portion in which a crack is generated by stress concentration after welding and the direction of propagation is directed toward the inside of the weld metal" are realized. How to select the torch angle (α) and the target position of the torch, that is, the position of the welding torch tip, apart from the taper angle (β) of the groove, which has already described the appropriate range, among various conditions. The guidelines for mushrooms will be described with reference to the following examples. "Target position of torch"
Is determined by the position of the tip of the torch in the axial direction of the pipe and the distance (x) from the outer surface of the pipe. In most cases, it is sufficient to place the tip of the flange cylindrical portion on a surface extending in the cross direction of the pipe. Since it is known that there is little room for selection, the target position of the torch referred to below exclusively refers to the distance (x) from the outer surface of the pipe.

SUS304 having an outer diameter of 35 mm and a thickness of 1.0 mm
A flange having the following shape and dimensions was manufactured by sintering the same SUS304 powder as a joint for a pipe made of: Cylindrical part: length 15 mm, tip part thickness 0.6 mm, thick part thickness 4 mm, tape 50 ° collar: 35.5 mm inside diameter, 10 mm wall thickness.

The target position of the torch is fixed to a point at a distance x = 1.5 mm from the outer surface of the pipe on the cross section of the tip of the flange cylindrical portion, and the torch angle (α) is set to 52 ⁰ , 60 ⁰ , 6.
5 ^0, 70 ⁰ and 75 ⁰ to be varied, and MIG welding the sintered material made by welding flanges of the the end of the SUS304 pipes. The distance (y) in FIG. 6, that is, the distance (y) between the position of the shallowest (or deepest) penetration into the sintered material and the position of the crack initiation point estimated in the fatigue test (which can be easily determined by simulation) is shown in FIG. Measured.
If the value of y is positive, there is a weld metal in the direction of crack propagation, and therefore, the crack is prevented when it does not progress. On the other hand, if the value of y is negative, the crack advances into the sintered body. The results are as shown in FIG. 7, where the torch angle α =
In 60 ^{0-75 0} range, to obtain a penetration of the cross-sectional shape of interest.

[0019] Next, the torch angle α ⁼ 60 0, ⁶⁵ 0,
In 70 ⁰ and 75 in each case ^0, the target position, the distance from the pipe outer surface (x) is welded varied so that 1.0 mm, was obtained in the same manner as data in FIG. That is, the target position is on the same plane, and the distance from the pipe is x = 1.
Also in the case of 0 mm, it was confirmed that favorable penetration was obtained. 7 and 8, "Start, 9
“0 ⁰ , 180 ⁰ and 270 ⁰ ” means plotting the value of (y) at the starting point where the welding torch was made to make a round along the circumferential groove and at the points where the welding torch was turned at each angle.

Further, when the target position was changed to 0.5 mm and 2.5 mm from the pipe on the same plane, welding was performed. The results are combined with the data of FIGS. 7 and 8, and the graph of FIG. 9 is obtained with the torch angle (α) on the abscissa and the distance (x) of the target position on the ordinate. It is concluded that the conditions suitable for welding in this case are that the torch angle α = 60 to 70 ⁰ and the distance x of the target position are in the range of 1.0 to 1.5 mm, which are surrounded by wavy lines in FIG. can get.

[0021]

Conventionally, when a joint made of a sintered material is used as a joint for welding, the fatigue strength of the welded portion is low. This problem was solved by the present invention.

By using a joint made of sintered material,
It is possible to enjoy various advantages such that the thermal effect of the welded portion is small, rework after welding is not required, and a joint having a complicated shape can be manufactured at once, and the welding cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a welded portion when a joint made of a sintered material is welded to a pipe, in which a conventional joint is used.

FIG. 2 is a sectional view showing a shape of a weld metal formed by the welding of FIG. 1;

FIG. 3 is a sectional view corresponding to FIG. 1 and showing a welded portion when a joint made of a sintered material is welded to a pipe, in which the joint of the present invention is used.

FIG. 4 is a sectional view corresponding to FIG. 2, showing a shape of a weld metal formed by the welding of FIG. 3;

FIGS. 5A and 5B are cross-sectional views each showing another example of the sintered material welded joint of the present invention, which is different from the example shown in FIG. 2;

FIG. 6 is a sectional view of a welded portion after welding for explaining a method of measuring a welding result in the example of the present invention.

FIG. 7 is a graph showing a relationship between a distance y and a torch angle in FIG. 6;

FIG. 8 is a graph showing a relationship between a distance y and a torch target position in FIG. 6;

FIG. 9 is a diagram showing a range of appropriate welding conditions, which can be concluded from the data of FIGS. 7 and 8.

[Explanation of symbols]

1A Flange (Prior Art) 1B Flange (Invention) 2 Pipe 3A Weld Metal (Prior Art) 3B Weld Metal (Invention) 4 Welding Torch S1 Crack Origin (Prior Art) S2 Crack Origin (Invention) α Torch Angle β Taper angle a Thickness of joint at open end d Pipe thickness x Target position of torch (distance from pipe outer surface) y Distance between penetration depth and crack initiation position

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Takao Shimizu F-term (Reference) 4D001 AA03 BB08 CA03 CC03 4E081 AA08 BA32 CA08

Claims (6)

[Claims] In a welded joint made of a sintered body of a metal powder and welded to an end of a metal product to be connected to each other, when a crack is generated due to stress concentration after welding, the direction of growth is determined by welding. A sintered material welded joint having a shape that gives a welded portion toward the inside of a metal. 2. A crack formed due to stress concentration after welding at a groove formed from an end portion of a metal product connected to each other and a sintered material welded joint to be used by welding therewith. A groove of a sintered material welded joint having a groove shape that gives a welded portion such that a growth direction is directed toward the inside of a weld metal. 3. The welded joint of the sintered material according to claim 1 is combined with the end of a metal product connected to each other with the groove shape according to claim 2, and the angle and the target position of the welding torch are selected. A method for welding a joint, characterized in that when a crack is generated due to stress concentration after welding, penetration having a cross-sectional shape such that the direction of propagation is directed toward the inside of the weld metal is realized. 4. A stress concentration after welding obtained by welding the sintered material welded joint according to claim 1 to an end of a metal product connected to each other with the groove shape according to claim 2. A welded portion of a joint, having a cross-sectional shape such that when a crack occurs, the direction of growth is directed toward the inside of the weld metal. 5. A joint having a shape of a flange for connecting a pipe, wherein a groove portion is a tapered surface, an inclination angle (β) to a cross section of the tapered surface is 20 to 60 degrees, and The sintered material welded joint according to claim 1, wherein the thickness (a) of the joint at the distal end portion is within 1.5 times the wall thickness (d) of the pipe. 6. A welding portion having a cross-sectional shape according to claim 3 is secured by previously tanning a groove portion of the joint before welding the joint to the metal product to provide a fusion portion. The welding method according to claim 3, wherein the welding method is performed.