JPS5944953B2 - Welding method for impeller blades and face plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of welding a rotor blade and a face plate of an impeller by TIG welding or MIG welding, and particularly relates to the above-mentioned welding method which requires extremely few welding man-hours and the number of backing holes.

Conventionally, TIG welding or M
IG welding method is used.

In addition, Fig. 1A is a plan view of the impeller, Fig. 1A is a plan view of the impeller, and Fig. 1B is a plan view of the impeller.
This is an A-AWI side view of No. 1.1'
is a face plate, 2 is a rotor blade cut from the face plate 1, 3 is a welded portion between the rotor blade 2 and the face plate 1', and W is the port width. The above TIG welding method or MIG welding method has the following problems.

(1) Workability is poor because the port width W is narrow.

(2) C, Mn, Ni, and C as impeller materials. M
Since a high-strength material with increased components such as o is used, weld cracks are likely to occur. Note that carbon equivalents obtained by replacing the above components with carbon amounts [for example, csq, (to) = C + Mn
/6+51/24+Ni/ 40+ Cr/ 5 +
The relationship between Mo/14] and cracking susceptibility tends to be as shown in FIG.

High-strength materials such as those described above have low ductility, and especially in the weld heat-affected zone, if the cooling rate is fast, they harden significantly, reducing elongation and causing cold cracking. In order to prevent this cold cracking, it is necessary to slow down the power of preheating and postheating at 100 to 300° C. before and after welding, and the cooling rate (this also leads to a decrease in workability). Furthermore, a high-strength material is also used as the weld metal, but in this case, contrary to the above, if the welding heat input is high and the BL cooling rate is slow, hot cracking of the weld metal occurs.

In order to prevent this hot cracking, it is necessary to lower the welding heat input and increase the cooling rate, contrary to the above measures against cold cracking. Therefore, the welding conditions that combine measures against cold cracking and hot cracking are extremely narrow.

Specifically, when TIG welding a moving blade with a plate thickness of
Welding current 180~220A) Welding speed 30~4011/
It takes about a minute. (3) In the case of the TIG welding method under the above conditions, if horizontal fillet welding (not shown) in which the face plate 1' is horizontal using a groove as shown in Fig. 3A, the rotor blade 2 The groove root 2' is difficult to melt, and in order to increase the amount of melting, the workpiece to be welded is positioned so that the X-X axis (where the face plate 1' is at approximately 45 degrees) is aligned as shown in Figure 3B. Even if vertical downward fillet welding is performed, it is difficult to completely melt the groove root 21 of the rotor blade 2.

This is the difference between plates with different thicknesses (in this case, the root length t
When welding the groove root 2' and the face plate 1' of plate thickness T, the cooling rate on the thick plate side (in this case, the face plate 1' side) is faster (i.e., the heat balance of the welded objects is different). , the heat from the welding torch 4 escapes from the thick plate side and the groove route 2
This is due to the fact that ' is not completely melted. In order to completely melt the groove root 2' of the rotor blade 2, it is necessary to increase the current density to above 180 to 220 A or reduce the amount of welding wire added to below 30 to 40 W11/min. 2) A certain force (in the former case, the root width L portion of the groove root 2' melts first, forming a back wave I at the root width portion as shown in Fig. 3B). This has an adverse effect on welding from the back side, and in the latter case, the surface of the weld bead 3' becomes concave as shown in FIG.
Therefore, in the past, the groove root 2' of the rotor blade 2 was not completely melted, and as shown in FIG. 3C, the back side was drilled before welding from the back side. This results in an increase in welding man-hours.

(4) The above (3) can be said almost similarly to horizontal fillet welding in TIG welding and MIG welding. The present invention has been made in view of the above points, and is intended to provide an efficient welding method that requires extremely few welding steps even when the port width is narrow and the welding conditions are very narrow.

That is, in the present invention, when welding a rotor blade and a face plate of an impeller by TIG welding or MIG welding, the rotor blade is subjected to groove root processing, and the rotor blade is in contact with the rotor blade groove root portion of the face plate. The gist of the present invention is a welding method for welding the rotor blade and face plate of an impeller, which is characterized by forming grooves on both sides or one side.

FIG. 4A is an explanatory diagram showing an example of an embodiment of the method of the present invention,
This is a case in which a groove root 2' is formed on the rotor blade 2 of the impeller, and grooves 5 are formed on both sides of the face plate 1' that are in contact with the groove root 2'.

If the material shown in Fig. 4A is welded by TIG or MIG welding, the plate thickness at the groove part (in this case, the thickness of the groove root 2') as shown in the model diagram of Fig. 4B. Since the length t and the interval T◯ between both grooves 5 are the same, and the welding heat is concentrated in a narrow range, the heat balance between the groove root 2' and the portion sandwiched between both grooves 5 is almost the same.

Therefore, it is difficult for the welding heat to escape, and the groove root 2' is almost completely melted as shown in Figure 4C, and the shape of the welding pipe 3' is also shown in the same figure (here, downward fillet welding is performed). As shown in the figure (shown in the figure), it is possible to obtain a good result without the formation of an underwave bead or a concave surface. Furthermore, even if a Uranami bead is formed, for example, since the groove 5 is machined on the back side as shown in FIG. (In other words, according to the conventional method described above, it was necessary to remove the back of a large part as shown in FIG. It only takes a short time because the back side only requires b.) FIG. 5 is an explanatory diagram showing another embodiment of the method of the present invention, in which a groove 5 is formed on one side of the face plate 1'. In the case of Figure 5,
It is desirable that the first welding be performed from the side without the groove 5. This is because if welding is performed for the first time from the side without the groove 5, it is easy to form a urana wave groove, but as explained in Fig. 4D above, if there is a welding force groove 5 on the back side, it will be easier and shorter. This is because the first welding can be performed from the side without the groove 5, and the shape of the weld beam will be better, although the reason is not clear. Furthermore, in the method of the present invention, regardless of whether the groove is formed on both sides or one side, it is permissible to form a groove C that extends to the inside of the groove root 2' as shown in FIG.

In addition, the number of plate thicknesses? An example of the groove dimensions for a rotor blade of approximately
Illustrated with diagrams.

In Figure 6, a=3~6, b=0.5~2, C=0~0
．． 3? M. r=2~10m d=0~31! 1, and these dimensions are the same in the case of groove processing on both sides.

As explained above, according to the method of the present invention, when welding the rotor blade and face plate of an impeller with a narrow port width and narrow welding conditions, (1) the groove root of the rotor blade can be almost completely melted and welded. The shape of the bead can be made good.

(2) It is possible to achieve high welding efficiency because it is possible to achieve effects such as eliminating the need for back punching b or even when back punching is required, it can be carried out easily and in a short time. can.

[Brief explanation of the drawing]

FIGS. 1A and 1B are explanatory diagrams showing the structure of the impeller, FIG. 2 is a chart showing the tendency of the relationship between carbon equivalent [Ceqω] and cracking sensitivity, and FIGS. C is a diagram showing an example of welding the rotor blade and the face plate of the impeller by the conventional TIG welding method;
Figure A. B, C, and D are explanatory diagrams showing one embodiment of the method of the present invention, and FIG. 5.6 is an explanatory diagram showing another embodiment of the present invention.

Claims (1)

[Claims] 1. TIG or MI welding the rotor blades and face plate of the impeller.
A rotor blade of an impeller characterized in that when welding by the G welding method, a groove root is formed on the rotor blade, and a groove is formed on both sides or one side of the face plate in contact with the rotor blade groove root. Welding method for and face plate.