JPH01289531A - Superplastic forging method - Google Patents

Abstract

PURPOSE:To superplastically forge a large product in a forging machine of small capacity by constraining part of forging material in a die, forging a residual part into the shape of a product, then, constraining a formed part in the die and forging a part not to be formed in the shape of the product. CONSTITUTION:The half in the longitudinal direction of a material 1 heated at a specified temperature is constrained by dies 2, 3 heated at the same temperature and the residual half is compressed by the die 2 and a punch 4. When forming is finished, a formed part is constrained by the dies 2, 5 and the residual part 1 is formed by a punch 6. As a result, the contact area becomes nearly half and the load also reduces nearly by half. Accordingly, a large product can be forged by a forging machine having a small capacity of forging load.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention utilizes the superplastic phenomenon of metal alloys such as titanium alloys, nickel alloys, and aluminum alloys to carry out compression forging under constant temperature. This paper relates to the improvement of the so-called superplastic forging method to obtain the desired product shape.

[Prior art] In recent years, superplasticity has been developed to process difficult-to-process materials such as titanium alloys into mH shapes at constant temperatures by utilizing their superplasticity phenomenon, as seen in JP-A-62-207526. Forging is being done. This method has the advantage of being able to form complex shapes that could only be processed by machining with a high yield, but has the following drawbacks.

That is, since the superplastic phenomenon occurs at a low strain rate, the forming speed is extremely low compared to normal forging, and the forming time is extremely long. Moreover, if there is a limit to the capacity of the forging machine used for compression, load limiting conditions are added from that perspective. At this time, basically, as described later,
By reducing the molding speed, the load can be reduced, but on the other hand, the molding time becomes longer, resulting in a decrease in production efficiency, or, as a result, it is not possible to mold products with large dimensions. Become.

[Problems to be Solved by the Invention] An object of the present invention is to forge a large product shape in a minimum forming time using a forging machine with a capacity as small as possible.

[Means and effects for solving the problem] The present invention provides that, in superplastic forging, a part of the material to be formed is restrained in a die, and the remaining part is forged into the target product shape. The superplastic forging method is characterized in that the formed part is then restrained with a die, and the unformed part is forged into a target product shape.

In principle, the area to be restrained is the entire surface other than the area that is being formed, but an area that does not cause any problem in the subsequent process or a part that is to be slightly formed as preforming may be left open.

The basis of the present invention will be explained below.

The forming load P in superplastic forging is roughly shown as follows.

P=σ·S−Q Here, σ is the yield stress of the material, S is the projected contact area between the punch and the material, and Q is a coefficient determined by the shape of the product to be molded, etc., and generally takes a value of about 2 to 5.

Among these, the yield stress σ is influenced by temperature, strain ε, and strain rate, and superplastic materials are characterized in that the effect of strain rate is particularly large, and is expressed as follows.

σ=A6° ε1 Here, A: coefficient, n: strain hardening index, m: strain rate index According to the above formula, if other coefficients are held constant and m = 0.4, the compression rate is 172 By setting the load to 1
It is calculated to be 71.3. However, it is understood that on the contrary, the forging time naturally doubles. Similarly,
In order to increase the load to 172, the compression speed must be reduced to 1/6, and the compression time will be six times as long. That is, by reducing the compression speed, it is basically possible to reduce the load, but on the other hand, this comes with the drawback that productivity is extremely reduced. Therefore, it can be said that if there is a measure to reduce the load other than the compression speed, such as halving the load, the effect will be very large.

On the other hand, as a measure to reduce the load, the inventors have experimentally found that the load can be reduced by focusing on Q and, for example, significantly changing the wall thickness of the shape to be formed.
Since the shape of the product is predetermined, when applying the final method, it is necessary to cut out the excess part by machining after the molding is completed, which increases manufacturing costs and is not always the preferred method. I can't say that.

The inventors focused on the contact area S in term 2, and found that the most effective measure to reduce the load was to reduce the contact area, and therefore devised to separate the forging process into multiple steps. did.

However, in superplastic forging, both the material and the die are kept at a constant temperature, and it is not possible to obtain a predetermined size and shape by simply forging the two parts. This is because the temperature of the entire material to be molded is maintained at a predetermined temperature, so the entire material has superplastic properties, so even parts that are not intended to be molded will deform if pressure is applied. In other words, parts that do not need to be formed during the initial forging are deformed, and ultimately the desired product shape cannot be obtained as a whole.

Therefore, it is necessary to restrain parts that do not want to be molded with a mold so that they do not deform. At this time, if the pressure applied to the restraint part is held within the mold, no special pressure applying device is required.

For simplicity, FIG. 1 shows a procedure for compressing a rectangular plate 1 in two steps. First, a material 1 heated to a constant temperature is restrained in the longitudinal direction by the molds 2 and 3 heated to the same predetermined temperature, and the remaining half is held in the mold 2 and the punch 4. Compress. When the molding is completed, the already molded part is restrained with the molds 2 and 5, and the remaining part 1 is molded with the punch 6.

As a result, the contact area is approximately halved, and the load is also approximately halved.

Note that in the two-step molding, the part that corresponds to the boundary may not necessarily be molded into the desired product shape, but since some machining can be allowed later, it is not necessary to mold it to such exact dimensions. Rather, if the shape of the boundary between the first forging and the second forging is not smooth, the second forging will cause a sudden change in the flow of the metal, resulting in what is called folding. may occur, so it may be necessary to slightly change the dimensions of the mold. In other words, there are cases where the product is formed larger than a young product and then cut later.

Note that the present invention is not necessarily limited to two steps, but also includes cases where molding is performed three or more times.

[Example] A product with the shape and dimensions shown in Fig. 2 was manufactured using a material size of 200 m.
mLX 160nooWX 1Ou+IIIt Ti composite material Ti-10V-2Fe-3AQ),
Compression speed 0 in 1 step in argon atmosphere at constant temperature of 60℃
．． When molded to a bottom thickness of 6 m+++t at 211 II m/min, a load of ]000 tons was required, and the molding time was approximately 3
It was 0 minutes.

Next, when I lowered the compression speed to 176 and compressed it,
Although the load decreased to approximately 50θton, the molding time decreased to approximately 18
It took 0 minutes.

Therefore, as shown in FIG. 3, by applying the present invention, the molding was divided into two parts in the width direction, and molding was performed at the same compression speed in two steps. That is, Fig. 3 shows the forming procedure, Fig. 3 (a-1) to (a-4) are longitudinal sectional views showing the state during forming in the forging machine, and Fig. 3 (b-1) to 3. (b-3) is a perspective view of the molded material, and Figure 3 (C) is A of Figure 3 (a-2).
-A sectional view is shown. As shown in FIG. 3 (a-1), the peripheral surface of the material 12 is restrained in almost contact with the inner peripheral surface of the mold 7, and the material 12 is restrained by the bottom surface of the mold 7 and the restraining mold 8.
The right half of is restrained from above and below. In this state, the material 12 is punched with the punch 9 as shown in Figure 3 (a-2).
Compress the left half of . At this time, a part of the material of the molded part flows into the hole 13 formed between the restraining die 8 and the punch 9 and the hole 14 formed between the die 7 and the punch 9.

FIG. 3(b-2) shows the shape of the intermediate molded material 12' at this stage. Next, the molded part is restrained by a restraining mold lO, and the unformed part is compressed by a punch 11. Figure 3 (a-4
) indicates the stage when molding is completed, as shown in Figure 3 (b-3).
indicates the finished product 12'.

According to the method of the present invention shown in FIG. 3, the load is 500 to
It was n. Since the molding time is 2 steps, it is twice as long as 60
However, productivity has improved significantly.

[Effects of the Invention] According to the present invention, even if a forging machine with a small forging load capacity is used, a large product can be M1 plastic forged in a short forming time.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram explaining the present invention using an example of forming a plate, Fig. 2 is a perspective view showing the product shape in the embodiment, and Fig. 3 is an explanation of the procedure for forming the product shown in Fig. 2. In the drawings, Figures 3 (a-1) to (a-4) are longitudinal cross-sectional views showing the state during forming in a forging machine, and Figures 3 (b-1) to (b-3) are perspective views of the formed material. Figures and Figure 3 (C) are Figure 3 (a-2)
It is an AA sectional view of. 1, 12.12', +2"...Material, 2.7.
...Mold, 3.5, 8.10...Restriction mold, 4,6.
9.11... Punch.

Claims (1)

[Claims] 1. In superplastic forging, a part of the material to be formed is restrained in a die, the remaining part is forged into the target product shape, and then the formed part is restrained in the die, and the unformed part is A superplastic forging method characterized by forging into a target product shape.