JPH08281454A - Method for joining titanium-aluminide and low alloy steel or plain steel - Google Patents

Abstract

PURPOSE: To prevent crack and to obtain welding strength by using a metal which does not develop a phase transformation at the time of cooling, as an intermediate material, in a natural cooling process of a member joined by passing while heating with the friction. CONSTITUTION: A recessed part 4 is arrange on the joining surface of a low alloy steel member or a general steel member 1 and the intermediate material 3 which is small in vol. change by cooling after heating, is fitted to the recessed part 4 so as to project from the joining surface. A titanium-aluminide member 2 is pressed and both members 1, 2 are joined while being heated by the friction caused by relatively rotation. In such a way, the intermediate material 3 does not cause the phase transformation and rejects the vol. expansion caused by the phase transformation of the low alloy steel member or the plane steel member 1 or absorbs a part of the vol. expansion. Therefore, the generation of crack, etc., on the joining part is prevented and also, the sufficient strength can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining titanium aluminide and low alloy steel or ordinary steel, and particularly to a material having low ductility such as titanium aluminide and after heating such as low alloy steel or ordinary steel. The present invention relates to a method of joining with a material whose constitution changes greatly by cooling.

[0002]

2. Description of the Related Art Materials, which are generally called new materials such as ceramics and titanium aluminide, have excellent characteristics not found in conventional metals such as ordinary steel. However,
Some of these materials have low ductility, so that not only in welding, but also in friction welding, cracks may occur during welding or during subsequent cooling, and sufficient strength cannot be obtained. There is also. For example, because titanium aluminide is an intermetallic compound, such as in the case of titanium aluminide,
Welding with dissimilar metals is considered difficult, and silver brazing has been used until now. After that, a method was proposed in which ordinary aluminum was joined to titanium aluminum by a joining method such as electron beam welding using a heat-resistant alloy having good joining properties as an intermediary member, and then the intermediary member and titanium aluminum were friction-welded.

Such ordinary steel is joined by a joining method such as electron beam welding using a heat-resistant alloy such as Incoloy 903, which has a good joining property with titanium aluminum, as an intermediary member, and then the intermediary member and titanium aluminum are joined. As a method of frictionally pressure-contacting, there is, for example, a method disclosed in Japanese Patent Laid-Open No. 2-157403. In this example, a steel shaft and a heat-resistant alloy hollow insert material are joined, and then the insert material and a titanium-aluminum turbine wheel are friction-welded.

In the example of JP-A-2-157403, the ordinary steel and the heat resistant alloy insert material are joined by electron beam welding or the like, and the heat resistant alloy insert material is hollow in order to reduce the amount of heat transfer to the shaft. I am trying.

FIG. 2 shows a conventional method for joining titanium aluminum turbine wheels. a is a titanium aluminum turbine wheel of a turbocharger, and b is a steel shaft. Reference numeral c is a hollow insert material interposed between the titanium aluminum turbine wheel a and the steel shaft b. The insert material c and the shaft b are first joined (e) by a joining method such as an electron beam, and then the insert c and the turbine wheel a are joined (e ') by friction welding.

[0006]

However, in the above-mentioned silver brazing, the strength is low, and further, it becomes weak as the temperature rises, and the reliability is not sufficient.

Even in the case of friction welding, the ordinary steel and the heat resistant alloy insert material are bonded by electron beam welding or the like, and the heat resistant alloy insert material must be hollow in order to reduce the amount of heat transfer to the shaft. There were problems such as having to do it.

The present invention has been devised in view of the above problems, and joins a material having a small ductility such as titanium aluminide and a material having a large change in constitution due to cooling after heating such as low alloy steel or ordinary steel. It is intended to provide a method.

[0009]

In order to achieve the above object, the method for joining titanium aluminide and low alloy steel or ordinary steel according to the present invention uses a titanium aluminide member and a low alloy steel member or ordinary steel member as an intermediary material. In the joining method of friction welding through, a step of providing a recess on the joining surface of any one of the titanium aluminide member and the low alloy steel member or the ordinary steel member, and in the recess, an intermediate material thicker than the depth of the recess is provided. There is a step of fitting, a step of pressing the titanium aluminide member and the low alloy steel member or the ordinary steel member relative to each other while heating them by friction and joining them, and a step of naturally cooling these integrated members. The mediating material is a metal material that does not undergo phase transformation due to a change in crystal structure during natural cooling.

[0010]

According to the above-mentioned joining method, a recess is provided in the joining surface of either the titanium aluminide member and the low alloy steel member or the ordinary steel member, and the intermediary material is fitted into the recess.
Although they are pressed against each other while rotating relative to each other and heating by friction, the intermediary material does not undergo phase transformation during natural cooling,
Since the volume expansion due to the phase transformation of the low alloy steel member or the ordinary steel member is repelled or partially absorbed, it is possible to prevent the occurrence of cracks or the like at the joint.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side view in which a part of a joint portion according to an embodiment of the present invention is cut away. In the figure, 1 is a low alloy steel member or ordinary steel member which is one member to be joined, and 2
Is a titanium aluminide member which is the other member to be joined. Reference numeral 4 denotes a recess provided on the joining surface of the low alloy steel member or the ordinary steel member 1, and prevents the intermediary material 3 fitted in the recess 4 from scattering when rotating. Further, the intermediary material 3 is fitted so as to protrude from the joint surface of the recess.

In this embodiment, the recess is provided on the joining surface of the low alloy steel member or the ordinary steel member 1, but it may be provided on the joining surface of the titanium aluminide member 2.

The low alloy steel member or ordinary steel member 1 and the titanium aluminide member 2 are joined together by using a friction welding device (not shown). These members are rotated relative to each other and the shaft is heated by friction. Strongly pressed in the direction 3
To mediate and join.

A specific example of the joining method will be described in detail below as the operation of this embodiment. The joining test was conducted by using chromium molybdenum steel (SCM435 steel) for one member to be joined and a titanium aluminide compound for the other member, and measuring the dimensions of chromium molybdenum steel (low alloy steel member) 1 with an outer diameter of 20 mm and a length. The dimensions of the titanium aluminide compound 2 were 30 mm, and the outer diameter was 15 mm and the length was 25 mm. In addition, first, direct bonding was performed without using a mediating material, and then, bonding was performed using a mediating material.

In the first joining test, that is, the joining test using no intermediary material, the number of revolutions: 2000 rpm, the friction pressure and the time: 150 MPa, 1 sec, the upset pressure and the time: 250 MPa, 6 sec. After that, the tensile test of the joining test piece was performed at room temperature, and the results are as follows.

The joint test pieces were separated at the joint surface during machining, and it was confirmed that their strengths were all zero.
Further, during the bonding test, the sound of cracks was heard, and further, when the bonding test piece was cut and its structure was observed with a microscope, it was observed that many cracks were generated at the bonding interface. In the second joining test, that is, the joining test using the intermediary material, a low alloy steel member (SCM435 steel)
A shallow recess having a diameter of 15 mm and a depth of 1 mm was provided on the joint surface of No. 3, and a disk-shaped intermediate material 3 having a diameter of 15 mm and a thickness of 2 mm, which was made of nickel alloy material IN617, was fitted into the recess.

Rotational speed: 2000 rpm Friction pressure and time: 200 MPa, 40 sec Upset pressure and time: 300 MPa, 6 sec Under these conditions, after performing 4 times, the tensile test of the joining test piece was conducted at room temperature in the same manner as the first time. The results are as follows.

220MPa, 240MP out of 4 times
It was confirmed to have tensile strengths of a, 190 MPa, and 220 MPa, respectively. In addition, during the joining test, the sound of cracks was not heard, but this is because the nickel alloy material IN617 as the intermediary material is SCM435 after pressure welding.
The strain due to the volume expansion of about 4% due to the phase transformation during cooling of the steel was repelled and partially absorbed, so that almost no transformation strain was transmitted to the titanium aluminide compound material having a fracture elongation of 1% or less, In other words, it is because the steel itself absorbs the strain.

[0019]

As described above, the present invention provides a method for joining a material having small ductility such as titanium aluminide and a material having a large change in constitution by cooling after heating such as low alloy steel or ordinary steel. In addition, a concave portion is provided in one of the members to be joined, and a material having a small change in constitution due to cooling after heating is intervened in the concave portion, and they are joined by being pressed while heating by friction by relative rotation. It is possible to prevent the occurrence of cracks and the like at the joint portion and to obtain sufficient strength, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a side view in which a part of a joint portion according to an embodiment of the present invention is cut away.

FIG. 2 is a cross-sectional view showing a joint portion according to a conventional method.

[Explanation of symbols]

 1 Low alloy steel or ordinary steel member 2 Titanium aluminide member 3 Intermediary member 4 Recess

Claims (2)

[Claims] 1. A joining method in which a titanium aluminide member and a low alloy steel member or a normal steel member are friction-welded via an intermediary material, wherein either the titanium aluminide member and the low alloy steel member or a normal steel member is joined. A step of providing a concave portion on the joint surface of, a step of fitting an intermediate material thicker than the depth of the concave portion into the concave portion, and the titanium aluminide member and the low alloy steel member or the ordinary steel member are relatively rotated and heated by friction. While having the steps of pressing and joining together, and the step of naturally cooling these integrated members,
The method for joining titanium aluminide and low alloy steel or ordinary steel, wherein the intermediary material is a metal material that does not undergo phase transformation due to a change in crystal structure during natural cooling. 2. The method for joining titanium aluminide to low alloy steel or ordinary steel according to claim 1, wherein the intermediary material is one of a nickel base alloy, an austenitic iron base alloy, a titanium base alloy and a cobalt base alloy. .