JPS5961584A - Frictional press welding method of titanium alloy - Google Patents

Abstract

PURPOSE:To join efficiently a titanium alloy at a low cost without laborious atmosphere conditioning in a frictional press welding method of the titanium alloy by specifying a friction time and subjecting the alloy to a brake type frictional press welding under the conditions satisfying a specific equation. CONSTITUTION:A round bar or steel of an alpha+beta type titanium alloy is subjected to brake type frictional press welding for 3-7sec friction time under the conditions satisfying the following equation: P2>=660(ndP1)<-0.44> where n: a difference in revolving speed rpm, d: the diameter of the round bar or pipe mm., P1: friction pressure kgf/mm.<2>, P2: upset pressure kgf/mm.<2>. The joint part having a good mechanical property virtually equal to the mechanical property of the base material is thus obtd. stably and surely.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a friction welding method for α+β type titanium alloy round bars or tubes.

In recent years, friction welding, which uses the frictional heat between materials to connect two axially symmetrical objects, has become popular.

It has come to be used in a wide range of mechanical industry fields, including mechanical parts, various piping, electrical equipment parts, tools, etc. mainly for the motor vehicle industry.

Compared to other welding methods used for similar applications, this friction welding method has excellent operational economy, such as requiring less energy consumption and upsetting during connection, and requires post-processing such as deburring. In addition, it is easy to process, has extremely high work efficiency when processing large quantities of items of the same size, and can weld dissimilar metals and materials that are difficult to dissolve, so the fields of its application tend to increase.

On the other hand, with the rapid development of the aerospace industry and the seawater utilization industry, the demand for titanium and titanium alloy materials has increased dramatically.
Various proposals have also been made regarding high-efficiency bonding methods.

By the way, titanium and titanium alloys have extremely strong affinity with air and other gases at normal welding temperatures.
It is known that absorption of these gases, even in small amounts, significantly increases hardness and reduces toughness. Therefore, when welding these materials, it is important to completely block the intrusion of atmospheric oxygen, nitrogen, hydrogen, etc., which has been the case until now.

1) Welding in an inert gas box, +i) T, ” -x, a or MIG welding, 11
Currently, special welding methods such as 1) electron impact welding and iv) plasma welding are being used.

Since the working temperature is relatively low and the working time is short, several attempts have been made to join titanium and titanium alloys by performing friction welding in the atmosphere, and the working conditions have not been discussed. Fragmentary data have been reported, but it is not always possible to obtain joints with sufficiently satisfactory mechanical properties, and even for titanium and titanium alloy members of arbitrary dimensions, At present, the emergence of a friction welding method that can reliably obtain sufficiently satisfactory mechanical properties has been awaited.

From the above-mentioned viewpoint, the present inventors have developed an efficient method of joining α+β type titanium alloy materials, which are expected to have the greatest demand among titanium feeds in the future, at low cost and without the need for troublesome atmosphere adjustments. Recognizing that the friction welding method, especially the brake-type friction welding method, is the most suitable for performing We conducted research to find a feasible friction welding method and found that: a) For α+β type titanium alloys, if the impact value of the friction welded part satisfies the required value for various uses;
Other mechanical properties such as tensile strength and bending strength are also sufficiently satisfactory, b) and the impact value of the joint depends on the forge pressure during friction welding; Furthermore, the forge pressure at which a proper joint can be obtained is determined by the circumferential speed of the round bar or pipe material and the friction pressure between the materials within a predetermined friction time. For example, even if the circumferential speed of the material changes, this can be easily compensated for by adjusting the friction pressure and an appropriate upset pressure can be maintained. C) Therefore, no matter how the material dimensions change, good friction welding of α+β type titanium alloy can be performed stably and reliably based on the formula shown in item b) above. ~(I came to the knowledge shown in C1.

That is, Figure 1 shows a typical α+β type titanium alloy.
A friction welding joint made of 1-6A9-4V alloy round bars with a diameter of 32g joined by the brake friction welding method was subjected to a tensile test 2 bending test and a 2V Shapey impact test to determine the mechanical properties of the joint. This is a diagram showing the results of investigating the limit friction welding conditions that are equal to or higher than those of the base metal. From the results shown in Figure 1, the mechanical properties of the friction weld joint of α+β type titanium alloy are It can be seen that as long as the value satisfies the desired value, other values will inevitably also be satisfied.

Figure 2 also shows the influence of friction welding conditions, friction time, and the Charpy impact value of friction welded joints made of similar materials.
This is a diagram showing the influence of friction time t.
1 is within the range of 3 to 7 seconds, it is clear that there is no significant difference in joint performance even if the friction pressure P changes.

Figure 3 shows a similar material with a diameter of 20 mm + 32 mm.
mr1. As shown in Fig. 1, this is a diagram showing the limit values of friction welding conditions evaluated by Charpy impact value for round bars of length 40 m and 40 m. It can be seen that the pressure P2 increases.

Therefore, as the diameter of the round rod becomes smaller, the necessary upset pressure P2
Based on the hypothesis that the reason for this increase is that the average circumferential speed or maximum circumferential speed decreases, resulting in a decrease in the average calorific value, the diameter is reduced from this, based on a round bar with a diameter of 32 wings. When we organized the experimental results so that the amount of heat generated was the same by increasing the friction pressure P1 by the amount corresponding to was brought about. That is, as shown in FIG. 1, the limit line of a round bar with a diameter of 32 mm is expressed by the formula: P2 ≧ 4.8P.

For any diameter d, 1 formula 5%
It was discovered that the limit line can be expressed using the formula %(1). and,
Changes in circumferential speed can occur due to differences in material diameters, or even by directly changing the rotational speed itself, but in this case too, compensation for circumferential speed can be achieved by correcting frictional pressure. Since it is clear that the limit line is calculated by the formula, P2=4.8(□・−・Pl)-044240032 [However, n is the rotational speed difference (rpm)], and furthermore, this can be roughly expressed as p2=6BO(nd
Pl) o44. Therefore, based on this formula, we examined the brake type friction welding conditions for obtaining a sound joint in more detail for α+β type titanium alloy. , )-""It became clear that sufficiently good results could be obtained.

This invention was made based on the above findings, and
A round rod or tube made of α+β type titanium alloy has a friction time of 3 to 7
The feature is that a sound joint can be stably and reliably achieved by brake-type friction welding in seconds and under conditions that satisfy the formula, P2 ≧ 660 (ndPl) - "" .

Note that the α+β type titanium alloy targeted in the method of the present invention is Ti-6Ai! -4V alloy, T''-6Ae
-6V-2Sn alloy, Ti-3A1! -2,5V alloy.

Ti-2Alt-' 2Mn alloy, Ti-6AA
This term refers to all titanium alloys that have a structure in which α and β phases coexist at room temperature, such as -2Sn-4Zr-2Mo alloys, and is not limited to specific types. Of course that is true.

Brake-type friction welding, also known as constant rotation friction welding, is a long-known friction welding method that uses a simple mechanism that uses a brake to stop the relative movement between materials. Of course, it also refers to the friction welding means used.

Furthermore, according to the method of the present invention, satisfactorily friction welding can be performed whether the target part is a round bar or a pipe. Outer diameter;
45~55Hz, wall thickness: 4~'i' m7M,
Formula, P2 ≧ 660 ((3C) ~ 35) nPl
) - It is preferable to perform brake type friction welding under the following conditions.

Figure 4 shows a round bar with a diameter of 32 mm and a diameter of 45 mm.
This is a diagram showing the limit line of the Charpy impact value of a tube with a wall thickness of 4 mm and a diameter of 55 mm x a wall thickness of 7 mm, and the limit line of the tube in this case is the limit line of a round bar with a diameter of 30 to 35 g. ,
That is, it can be seen that it almost coincides with the limit line of a round bar with a diameter of 32 mm. That is, in the case of these tubes, the diameter: 3
The circumferential speed is higher than that of a 2g round bar, but because the wall thickness is thinner, heat is released by radiation to the inside of the tube, so the thermal state almost matches that of a 32 mm diameter round bar. It is assumed that.

In the present invention, the friction time is limited to 3 to 7 seconds because
If the friction time is less than 3 seconds, it will not be possible to obtain the necessary amount of heat for friction welding, regardless of the diameter of the materials, the difference in rotational speed, or the friction pressure, and therefore it will not be possible to obtain sufficiently satisfactory joint characteristics. This is because even if the friction time exceeds 7 seconds, no further effect of improving joint properties can be obtained.

In addition, the reason why the upset pressure P2 is limited to the value obtained by the formula (%) is that if the upset pressure is less than that value, the mechanical properties of the joint become comparable to those of the base material, as described above. This is because the result will not be good.

Next, the present invention will be specifically explained using Examples and in comparison with Comparative Examples.

Example 1 First, it had a component composition consisting of AA: 5.94% by weight, V: 4.055% by weight, 0:O12% by weight, and the remainder: Ti and other unavoidable impurities, and had a diameter of 32 m.

Titanium alloy round bars were prepared, and brake-type friction welding was performed between the round bars under the friction welding conditions shown in Table 1.

When the mechanical properties of the joint portion of the obtained pressure contact member were measured, the same results as shown in Table 1 were obtained. In addition, when the mechanical properties of the base material of the same member were also measured, the Charpy impact value was 4. ' 3 kg・
m/crl, bending strength is 380 k at nominal maximum bending stress
g7ma + tensile strength showed a value of 98.0 kg/-.

From the results shown in Table 1, test number 1, in which the friction welding conditions satisfied the range of the present invention, showed excellent mechanical properties of the joint that were almost the same as those of the base material. On the other hand, in test No. 2 where the forge pressure was lower than the value of the formula, 6 6 0 (ndPl), the bending strength was equivalent to that of the base material, It can be seen that the Charpy impact value of the joint is extremely low.

Example 2 Ae: 5: 79% by weight, V: 5.35% by weight,
Sn2: 1.76% by weight, Cu: 0.45% by weight,
It has a component composition consisting of O: 0.15% by weight, Ti and other impurities: the remainder, the outer diameter is 46mm, and the wall thickness is 4.
mm titanium alloy tubes were prepared, and the tube materials were subjected to brake-type friction welding under the friction welding conditions shown in Table 2.

Regarding the obtained pressure-welding member, the mechanical 14 [
When the quality was measured, the same results as shown in Table 2 were obtained. In addition, when we measured the mechanical properties and quality of the base material of a similar member, the Charpy impact value was 28 kg・m1
crl, nominal maximum bending strength is 410kg/mm +
Tensile strength is 113 kg7m1? The value of L is shown.

From the results shown in Table 2, test number 3, in which the friction welding conditions satisfied the range of the present invention, showed excellent mechanical properties of the joint that were almost the same as the base material. On the other hand, it can be seen that in Test No. 4 where the forge pressure is lower than the value of the formula, 660(ndPx -044), the Charpy impact value of the joint part in particular is extremely low.

As described above, according to the present invention, it is possible to efficiently join α+β type titanium alloy materials at low cost without having to perform troublesome atmosphere adjustment, and moreover, using a good machine that is almost the same as the base material. Industrially useful effects can be brought about, such as the ability to stably and reliably create joints with excellent properties.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between friction welding conditions and various joint performances for T1-6AQ-4V, and Figure 2 is a diagram showing the relationship between friction welding conditions and various joint performances for T1-6AQ-4V.
Figure 5 is a diagram showing the relationship between friction welding conditions and Charpy impact value for P, -4V; Figure 5 is a diagram showing the influence of round bar dimensions on the best joint performance of round bars for Ti-6AA-4V; Diameter for Ti, -6AIL-4V: 32
FIG. 3 is a diagram showing the relationship between the best joint performance and friction welding conditions for mm round bars and pipes of various diameters. Applicant Sumitomo Metal Industries Co., Ltd. Agent Tomi 1) Kazuo and 1 other person 1st layer friction, pressure fi rPtJ (kgf/mm2
) 禦2R

Claims (1)

[Claims] A round rod or tube made of α+β type titanium alloy has a friction time of 3 to 7
A friction welding method for α+β type titanium alloy, characterized by performing brake-type friction welding in seconds and under conditions that satisfy the following formula.