KR930007208B1 - Inertia weld improvements through the use of staggered wall geometry - Google Patents

Abstract

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Description

Inertia welding method of high strength hollow superalloy material

1 is a schematic view showing a welded shape of a conventional hollow material.

2 is an optical micrograph of a welded material having the shape shown in FIG.

3 shows the shape of a welded joint according to the invention.

4 is an optical micrograph of a welded joint having the shape of FIG.

5 shows the shape of an optional weld zone according to the invention.

6 is an optical micrograph of a weld zone having the shape of FIG.

* Explanation of symbols for main parts of the drawings

A, B: hollow material OR _a , OR _b : outer radius

IR _a , IR _b : Inner radius S _I , S _o :

The present invention relates to an inertial welding method of a hollow material. The present invention also relates to an inertial welding method of a high strength superalloy material and an inertial welding method of a high strength superalloy material produced by powder metallurgy.

The inertial welding method is a method used to join metal materials that are symmetric about an axis of rotation. The materials may be solid or hollow materials. Thus, for example, an inertial welding method can be used to join parts together to form a product such as a crankshaft or a welded hollow tube assembly. Inertial welding methods are described, for example, in US Pat. Nos. 3, 234, 644, 3, 235, 162, 3, 462, 826, 3, 591, 068, and 4, 365, 136. The contents are incorporated herein by reference.

In brief, in inertial welding, the materials to be joined are arranged so that their axes of symmetry coincide and the surfaces to be joined are in parallel. One of the materials remains fixed and the other is attached to the rotatable flywheel. The rotatable material-flywheel combination is accelerated at a predetermined rotational speed and the material being rotated is pressed against the fixed material. The kinetic energy is determined by the shape of the flywheel, the weight and the rotational speed, and the kinetic energy is converted into thermal energy by the friction between the materials to be joined. The materials are compressed together and the kinetic energy converted is sufficient to soften the locals.

When the rotation of the flywheel is stopped, the forces between the materials remain or increase to allow the softened portions of the materials to join together. The forces between the materials cause plastics or superplastic deformation in the weld zone. Cooling of the weld zone is achieved very quickly by the thermal conduction of the material.

The inertial welding method is carried out in a manner that essentially eliminates the problem of surface contamination by releasing (pushing) a significant amount of material from the weld zone. Weld zones have more forging characteristics than casting. Welding zones produced by welding such as lasers, electron beams, and electric fusion welding are melted and remodeled, and therefore have less desirable casting properties than the forging properties approximated by inertial welding zones. .

Inertial welding is a form of friction welding. Another type of friction welding is achieved by continuous motor drive to provide frictional heat rather than energy stored in the flywheel. The term 'inertial welding' as used herein is intended to include other forms of rotary friction welding.

Inertial welding methods have been widely used in the heavy equipment industry to join iron materials such as iron and steel. Recently, the inertial welding method has been used to bond superalloy. Since the superalloys have a higher softening point and exhibit greater resistance to high temperature deformation, the bonding of superalloy materials becomes much more difficult than the bonding of ferrous materials. Inertia welding of "powdered" superalloys is considered the most difficult. The welding process limits the welding zone of the material to be softened, and the extent of upset or deformation in the welding zone is likewise limited. Thus, in inertial welding of superalloys (particularly powdered superalloys), there is a residual notch in the weld zone. Such residual notches often do not occur in the case of inertial welding of ferrous materials.

Unfortunately, in the case of powdered nickel superalloys, the weld zone notch is always inward (fine) beyond the original diameter of the weld material. Therefore, even after the upset of the weld is removed by machining, the notch is present and machining must be performed while reducing the original diameter of the material to be joined to remove such notch. If the notch is not completely removed, the notch will act as a stress concentration source and break initiation compartment during use of the welded material or during heat treatment after welding. This problem of notches is particularly detrimental for high strength superalloys (i.e., superalloys with yield strengths in excess of 100 ksi at 1000 ° F) and superalloy materials produced by powder metallurgy techniques.

In the initial production of superalloy material by inertial welding, the notch problem can be overcome at a certain economic cost by making the original material large and machining the welded assembly to a size sufficient to remove the notch. have. Unfortunately, however, such a method becomes undesirable when it is necessary to repair damaged material by inertial welding. This is because the undamaged part of the material is already machined to a certain diameter, the minimum design diameter that can be reduced without affecting the part. Therefore, in the case of removing the damaged part of the superalloy material and replacing it with a new one, there is a weakness in the finished material because there is a weld zone notch that acts as a material weakening element or requires the material to be processed to an excessively small size. It exists.

Even in the initial fabrication, the use of oversize materials may exceed the capacity of the inertial welder used.

In addition, there are also welded bodies that have been difficult to weld inertia. These shapes are encountered when producing tapered materials such as hollow cones. This situation occurs when the shaft is coupled to the disk in the gas turbine engine.

It is therefore an object of the present invention to provide a method for inertia welding a material and controlling the depth and position of the weld zone notch.

Another object of the present invention is to provide a method for inertial welding a high strength (and / or powder metallurgical treated) superalloy while minimizing the deleterious effects of weld zone notches.

It is a further object of the present invention to provide a shape used for inertial welding the materials to form a conical hub.

Superalloys are nickel-based alloys that are reinforced by precipitates based on Ni ₃ Al. High strength superalloys refer to superalloys with a yield strength above 100 ksi at 1000 ° F.

According to the invention, the notch of the inertial welding zone is controlled in size and position by having the materials to be joined have significantly different wall diameters. By varying the wall diameter of the joined hollow materials, a step is formed in the weld zone; This controls the flow of heat generated by the welding process, the shape of the weld zone and the release of material from the weld zone, and consequently the position and size of the weld zone notch. In particular, the weld shape of the present invention reduces the size of the notch and shifts the position of the notch, making the notch less harmful than in the case of inertial welding of the prior art.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The basic spirit of the present invention is that the shape of the weld joint is changed so as to control the heat flow and release of the material from the weld so that the released material does not form a notch in the final size of the part fabricated in the welding process. . The method of the present invention is employed to fabricate conical or other tapered hollow materials.

The invention can be understood with reference to FIG. 3; In FIG. 3, the diameters of the materials are shifted with respect to each other so that there is a deviation between the materials to be joined and a stage is formed in the interior and the exterior of the weldment in proximity to the welding zone. This will serve as an important factor in the heat flow and release of the softened material, as detailed below.

1 shows a conventional welded shape for hollow materials. The materials to be welded are symmetrical and have the same thickness in the centerline shown, and the parts to be joined are centered with respect to each other. Therefore, the welding zone is symmetrical across the plane of the welding zone, and the material discharge from the welding zone is also symmetrical if the material materials are assumed to be the same. This symmetry in FIG. 1 results in a flat weld zone.

FIG. 2 shows an enlarged photograph of a test joint performed with respect to the shape shown in FIG. 1, showing the weld notch and the released (pushed) material. It should be noted that in Figure 2 the weld notch extends inwardly of the original workpiece dimensions (inner and outer diameters), indicating that the weld zone has an area smaller than that of the original workpiece. Such joints or notches have a very detrimental effect on the strength and durability of the weld. In FIG. 2 the weld zone is flush with the original interface between the materials.

3 shows a weld shape according to the invention. As shown in FIG. 3, the radius of the hollow material A is smaller than the radius of the hollow material B. In particular, the outer radius OR _a is smaller than the outer radius OR _b and the inner radius IR _a is smaller than the inner radius IR _b . In addition, the average radius of the hollow material A is smaller than the average radius of the hollow material B and the average radius is calculated as (OR + IR) / 2. Due to the difference in shape, a stage is formed at an interface between the two materials, that is, stage S ₁ is formed at the inner diameter of the composite materials and stage S ₀ is formed at the outer diameter of the composite materials. The inner stage S ₁ is located on the opposite side of the joining plane from the outer stage S ₀ . This short phenomenon causes a change in heat flow during the welding process and a change in stress during heating and cooling of the weld zone.

An enlarged photograph of the final weld zone is shown in FIG. It can be seen that the deviated weld shape creates a weld zone with a unique curvature of the S shape. Due to the shape of the curved weld zone as described above, the material released from the weld zone at the inner and outer diameter portions is at a particular angle, rather than perpendicular to the material axis as in the case of inertial welding operations according to conventional shapes. It will protrude. This change in material release will affect the size and position of the residual weld zone notch. This means that machining the ends inside and outside the weld zone completely eliminates the weld notch while minimizing material cutting. For the superalloy material the stage sizes S ₁ and S ₀ are 10 to 50%, preferably 15 to 40% of the thickness of the hollow material A. The thickness of the hollow material A can be calculated as (OR _a -IR _a ).

The wall thicknesses of the hollow materials A and B do not necessarily need to be the same as long as the inner end and the outer end are kept in the aforementioned ranges. For example, if Material A has a wall thickness of 0.200 inches, the stage may be in the range of 0.020 to 0.100 inches. A 0.200 inch wall thickness with the outer diameter OD _A and the mean diameter of 10.2 inches of 10 inch inner diameter ID _A 10.4 inchi material is 0.32 inch wall having an average diameter of the outer diameter OD _B and 10.28 inches of 9.96 inches internal diameter ID _B 10.6 inchi It can be combined with other hollow materials of thickness to meet the criteria of the present invention by creating an outer end of 0.1 inch and an inner end of 0.02 inch.

5 shows another weld geometry useful for the production of certain gas turbine engine components while the present invention works. In FIG. 5, the materials are shifted with respect to each other, and each material is tapered with one wall rather than with parallel walls, with the inner wall tapered for material A and the outer wall taped for material B do. This shape can be used to form a conical material. Such a conical shape is commonly used in the case of a gas turbine engine where the shaft must be attached to the disk with minimal mass and high torque transmission performance. The dashed line shows how the hollow cone weight material is machined from the inertia welded material with minimal material cutting.

FIG. 6 shows an optical micrograph of a test sample inertia welded in the state having the original shape shown in FIG. It can be seen from FIG. 6 that the weld notch has been moved and thus only a minimum of metal needs to be removed to create a conical shape.

While the invention has been shown and described with respect to preferred embodiments thereof, it will be apparent to those skilled in the art that various changes may be made therein without departing from the spirit or scope of the invention as set forth in the claims below. Those with knowledge can easily know.

Claims (2)

A method of inertial welding of a hollow superalloy material having a high strength, the method comprising: providing a first material to be bonded having an inner diameter, an outer diameter, and a center line, and providing a second material to be bonded having an inner diameter, an outer diameter, and a center line; Equipped; When the inner diameter of the first material is smaller than the inner diameter of the second material and the outer diameter of the first material is smaller than the outer diameter of the second material, the first material and the second material are placed together with their respective centerlines aligned. Radial stages corresponding to 10 to 50% of the wall thickness of the first material are formed at the interface between the materials and a hollow zone having a high strength, characterized in that a welding zone is formed which is curved into an S-shape during welding Inertial welding method of super alloy material. 2. The method of inertial welding of a hollow superalloy material as claimed in claim 1, further comprising the step of machining the welded material into a hollow cone when used to form a conical material. .

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