JPS58181470A - Surface hardening build-up welding method - Google Patents

Abstract

PURPOSE:To perform build-up welding of a Co-Cr alloy having high hardness and smoothness on the surface of a metallic base material easily, by supplying mixed powders of an alloy consisting essentially of Co-Cr and NbC, etc. into the plasma arc which is shielded with an inert gas. CONSTITUTION:A W electrode 2 of a plasma arc welding torch and a copper electrode 3 which is cooled with cooling water 4 are connected to a DC power source 10 and gaseous Ar 9 foming a plasma arc is supplied to form a pilot arc between the forward ends of the two electrodes 2, 3. Gaseous Ar 8 for shielding is supplied from a shielding gas nozzle 7, and the electrode 2 and a carbon steel base material 1 are connected to a DC welding power source 11 to generate a plasma arc between both. Mixed powders 6 of alloy powder consisting essentially of Co-Cr and >=1 kind among NbC powder, VC powder and TiC powder are supplied from between the electrode 3 and an outside cylinder 5. The weld metal wherein the NbC powder, etc. is mixed in the deposited alloy is thus formed on the surface of the material 1.

Description

[Detailed description of the invention] The present invention relates to a method of forming an overlay weld of an alloy.

Co and Or alloys, commonly known as stellite alloys, are generally overlay welded to provide corrosion resistance or wear resistance to the surface of the metal base material, and TIG welding and gas welding are mainly used as welding methods. Stellite alloys having the following chemical components are generally used.

(N ni o ni r W Fc (w+%) Pinocurse Hard Zeta Stellite A 1.0 Remainder 280 40
: i0 or less 400 Stellite B135 remaining
291J ao 25 under 470 Stellite C25 remaining 3 (10 120 30 or less 6
00 However, when overlaying these alloys, preheating to 300℃ or higher is required to prevent 1-bath weld cracking, and in particular, when using Stellite C, high-temperature preheating of up to 600℃ is required. . As described above, overlay welding of stellite alloys requires high-temperature preheating, which makes welding extremely difficult, especially when the workpiece is large. Furthermore, gradual cooling is required after welding, and overlay welding of stellite alloys is expensive and economically problematic.

In addition, despite such problems, the hardness of the weld metal obtained is limited to pinocase hardness, Hv 600. However, as the performance and efficiency of various machines improve, there is a strong demand for improved performance of parts exposed to wear environments, and current overlay welding of stellite alloys is no longer able to meet this demand.

The present invention is proposed to improve the drawbacks of the above-mentioned conventional methods during the arc generated between the metal base material and the non-consumable electrode shielded with an inert gas.

Alloy powder mainly composed of Co-Cr '5c and Nb
Provided is a surface hardening welding method characterized by forming a weld metal on the surface of a metal base material by supplying a mixed powder with at least one of C powder, VC powder, and 'I''iC powder.

Therefore, in the method of the present invention, by applying an alloy overlay consisting of a CoOr alloy powder and a mixed powder of at least one of NbC powder, VC powder, and 'I'iC powder, Overlay welding has a smooth surface with no cracks and high Vickers hardness, which has the advantage of improving the performance of various mechanical parts, and also eliminates the need for preheating, slow cooling, etc. The economic impact is also significant.

The method of the present invention will be explained in detail with reference to Examples.

In FIG. 1, surface hardening welding is carried out by feeding a mixture of stellite alloy powder and metal carbide powder to a plasma arc.

In FIG. 1, 1 is a carbon steel base material, 2 is a Toughgesten electrode of a plasma arc welding torch, 3 is a copper electrode having a jacket structure cooled by cooling water 4, and 5 is an outer cylinder surrounding the copper electrode 3. There is a gap between the copper electrode 3 and the outer cylinder 5, into which the powder 6 can enter. 6 is NbC powder 8 in Stellite base metal A powder 20%
The particle size of each powder was 200 mesh/unit or less.

7 is a /-rudo gas nozzle that supplies the outside of the plasma arc, and 8 is /-rudo argon gas.

9 is an argon gas supplied around the electrode 2 to form a plasma arc; 10 is a DC power source that generates a pilot arc between the electrode 2 and the copper electrode 3; 11 is a gas between the electrode 2 and the carbon steel base material 1; This is a DC welding power source that generates a plasma arc.

When the circuit of the DC power source 10 is closed while supplying argon gas 9, a birobar arc is generated between the tip of the electrode &2 and the tip of the copper 1 pole 3. Subsequently, when the circuit of the DC welding power source II is closed while supplying the nodal gas 8, a plasma arc is generated between the electrode 2 and the base material 1. When the plasma arc voltage is 32 V, the plasma arc current is 11 OA, and the powder 6 is fed at a rate of 1597 m, the stellite alloy A powder in the powder 6 is melted and deposited on the surface of the base material 1, and therein Unmolten NbC powder is mixed in and forms weld metal. .

Figure 2 is a photograph of the cross-sectional microstructure of this weld metal, and the Vickers hardness of this part is I (v 800-900,
The surface of the welded part was smooth and 10% smooth.

Next, as a second example, stellite alloy A powder 3 is added to the 2 powders.
Weld metal was formed under the same conditions as in Example 1 using 0% NbC powder and 70% NbC powder.

In this case as well, the surface of the weld metal was smooth and there were no cracks. Further, the average Vickers hardness of the cross section of the bath-welded metal was Itv 700-800.

Furthermore, as a third example, stellite alloy A powder 3 is added to the powder.
0% Nb powder, 20% Nb powder, and 5° TiC powder were mixed, and the same welding conditions as in Example 1 were used.

A bath weld II4 was formed. The surface of the weld metal was smooth and sound with no cracks. Further, the Vickers hardness of the cross section of the weld metal was Hv 700 to 800.

Furthermore, from the measurement results of the hardness of weld metal obtained by varying the mixing ratio of carbide powder independently, it is found that when the mixing ratio of carbide powder is lower than 35% in volume fraction, there is little improvement in the hardness of weld metal. No contribution.

It turns out to be impractical. Further, when the carbide powder mixing ratio is 35 to 80%, the hardness of the bath-welded metal increases in proportion to the carbide powder mixing ratio.

If it exceeds 80 inches, the welding efficiency of the carbide powder will drop significantly and it will not significantly contribute to improving hardness, making it impractical. Therefore, the practical mixing ratio of carbide powder is 3 in terms of volume fraction.
It is 5-80%.

In addition to the stellite alloys shown in the examples, stellite B, stellite C, and the following stellite alloys and E can also be used as the Co--Cr alloy powder used in the method of the present invention.

W Vickers CCo Cr NI Mo Fe (,,%)
p Sastellite l) 0.28 remaining 280 30 5
4 1.4-380 Stellite E 1.15 remaining 258
227 27670 33 350

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the method of the present invention, and FIG. 2 is a photograph of the cross-sectional micro-structure of the weld metal in the same example. 1 carbon steel base material, 2. Plasma arc welding Tanogsteno electrode, 3 Copper electrode, 5. Outer cylinder, 6 mixed powders

Claims (1)

[Claims] During the arc generated between the metal base material heated with an inert gas and the non-consumable electrode, an alloy powder mainly composed of Co-Cr, and at least one of Nbc powder, VC powder, and T"iC powder are mixed. A surface hardening bath welding method characterized by supplying a mixed powder with one or more types of powder to form weld metal on the surface of a metal base material.