JPH01202389A - Manufacture of steam turbine long blade - Google Patents

Abstract

PURPOSE:To have a high tensile strength and to improve toughness and fatigue strength as well by forcibly cooling a (alpha+beta) type titanium alloy after heating and holding it in (alpha+beta) zone after executing a hot treatment thereon and executing an aging treatment at specified temp. CONSTITUTION:The Ti-6A-6V-2Sn alloy of (alpha+beta) type is forcibly cooled after holding it by heating at the temp. of 10-60 deg.C lower than a beta transformation temp. after executing rough forging/stamp forging thereon. It is then subjected to machining in specified wing shape, a beta type Ti alloy plate is welded to the tip of the blade and the deformation caused by welding is subjected to a primary straightening at the temp. of 150-350 deg.C. Moreover secondary straightening, aging treatment and welding residual stress removing treatment are simultaneously executed at 500-650 deg.C by forcibly bundling it on the jig having specified wing profile shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a steam turbine long blade, and in particular, to a method for manufacturing a steam turbine long blade.
The present invention relates to a method for manufacturing long wings of 8 inches or more.

[Conventional technology]

12Crtil is used for 33.5" long blades, but 12Cr steel has reached its limit as centrifugal force increases as the blade becomes longer. Therefore, lightweight and high strength long blade material is used. Titanium alloys are considered the most promising material for long wings.

Up to 40-inch long wings can be manufactured using titanium alloy with a tensile strength of 95 kg/mnz class, but for 48-inch long wings, a titanium alloy with a tensile strength of 115 kg/+nm" class is required. Tensile strength 115 Materials with k, H/+n2 or higher include age-hardening β-type titanium alloys.However, this β-type titanium alloy has the disadvantage of low toughness, so
There are problems with manufacturing the entire wing from this alloy. This class of (α+β) type titanium alloy materials is disclosed in Japanese Patent Application Laid-Open No. 61
Although it is disclosed in Japanese Patent No. 284560, it is desired to develop a material with even higher toughness for the 48-inch long blade, and improvement is necessary.

Furthermore, conventionally, 12Cr stainless steel has been mainly used for steam turbine blades. In this case, the stellite plate is welded to prevent the tip of the blade from getting wet due to water droplets in the steam. Although deformed by this welding, 12Cr
In the case of steel, it has been possible to correct the deformation by simply bending or twisting it in the direction that reverses the deformation.

On the other hand, in the case of titanium alloy blades, it has been considered impossible to straighten the blade by bending or twisting as in 12Crll because the blade will break.

[Problem to be solved by the invention]

If you try to increase the wing span to 48 inches, the centrifugal force acting on the wing will increase significantly, so the tensile strength will be 115 kg.
/ nuz or higher wing material is required.

In addition to high tensile strength, it is also important to have high toughness and fatigue strength. In terms of toughness, the V-notch Charpy impact value is 1.4 kgm or more, and the -10 million cycle fatigue strength is 55 kg.
/rrtnz or higher is required.

Means for solving Section C] The above purpose is to hot work an (α+β) type titanium alloy, heat it to the (α+β) region, hold it, forcefully cool it, and then heat it to a temperature of 500 to 650°C. This is achieved by subjecting it to an aging treatment. The aging treatment is also performed as stress relief annealing after welding the erosion shield plate to the blade base material.

In addition, the deformation caused by welding is 150℃~350℃
After primary straightening at a temperature of
It can be corrected by performing secondary correction.

This secondary correction is also performed as the above-mentioned aging treatment.

[Effect]

After hot forging, by heating and holding in the (α+β) region and forced cooling, the two-phase structure of α crystals and α′ fumarunsite becomes finer and more homogeneous, improving ductility.

Subsequent heating at 500°C to 650°C results in age hardening and high tensile strength.

The solution temperature in the (α+β) region is 10 to 50° below the β transformation point.
A lower temperature is better. If this temperature is lowered too much, α
This results in a structure with many crystals, resulting in low fatigue strength.

Next, primary correction before aging treatment (secondary correction) will be explained.

If the temperature of the primary straightening is lower than 150°C, the deformation resistance of the material will be large and the ductility will be small, so β
Cracks easily form in the mold alloy erosion shield material.

In addition, at temperatures higher than 350°C, the ω phase precipitates in the β-type alloy two-lotion shield material, resulting in lower ductility.
Cracks tend to occur in the erosion shield material during the loading of the next secondary correction. Therefore, -order correction is 150 to 350℃
Must be carried out in a temperature range of 200℃~300℃
It is preferable to do so.

〔Example〕

<Example 1> A Ti-6Al-6V-2Sn alloy material having a composition shown in Table 1 was hot forged and then subjected to heat treatment shown in Table 2.

Table 1 The β-transformation temperature of this material was 950°C. Comparative material (
1) is annealed according to the AMS standard, but its tensile strength is low and the strength (T, S) required for a long wing material is low.
> 115 kg/mm2).

Even if solution treatment and aging treatment is performed, if the solution temperature and aging temperature are low, the toughness required for a long wing material (V-notch shock value > 1, 4 kg-m) cannot be obtained.

As with the present invention materials (1) and (2), by applying solution and aging treatment at appropriate solution temperature and aging temperature, the tensile strength, impact value and Materials with fatigue strength (55 kg/mm2 or more) can be manufactured.

As shown in FIG. 1, at heat treatment temperatures other than those of the present invention, 4
It is not possible to obtain the mechanical properties required for an 8-inch long wing.

<Example 2> Next, an example of manufacturing a titanium blade according to the present invention will be described.

As shown in Figure 1, first, after rough forging the round bar material,
Shade forging at 0 to 850℃ (α-β temperature range), then 9
After water quenching at 20°C, it was machined into a predetermined shape.

The tips of the blades are made of β-type titanium alloy (Ti-15V-3) to prevent water droplets from forming in the water vapor.
Cr-3A Q-38n alloy) was electron beam welded.

Since deformation occurs due to welding, primary straightening was performed at 300°C to roughly correct the deformation. Next, 56 blades were forcibly restrained in a jig having a predetermined blade profile shape.
Heating was performed at 0° C. for 4 hours (secondary correction).

This two lotion shield material is Ti-15V-3Cr
-3Afl-38n alloy plate, 80″ in advance
This is a material that has been oil quenched for cX20 minutes.

〔Effect of the invention〕

According to the present invention, the power generation efficiency of a thermal power plant can be increased, and energy savings and power generation costs can be reduced.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. In the method of manufacturing a titanium alloy long blade, (α
+β) type Ti-6Al-6V-2Sn alloy with rough forging and
After die forging, the blade is heated and maintained at a temperature 10 to 60 degrees Celsius lower than the β-transformation temperature, then forcedly cooled, then machined into a predetermined blade shape, and a β-type Ti alloy plate is placed at the tip of the blade. Weld and deformation caused by welding at 150℃ to 350℃
Primary straightening is carried out at a temperature of
A method for manufacturing a long steam turbine blade, characterized in that secondary straightening, aging treatment, and welding residual stress removal treatment are performed simultaneously at 0°C.