JPH0366477A - Manufacture of hard facing material for surface hardening - Google Patents

Abstract

PURPOSE:To obtain satisfactory characteristics of weldability, hard facing property, tough wear resistance and workability by refining and dispersing hard particles in hard facing material. CONSTITUTION:A plasma arc formed on the inside of a torch 10 by applying a welding current is shifted to an elongator plug 54 and then, carried gas containing specified mixed powder is supplied to a path 20 from a carried gas feeder 34 and a powder feeder 36 and injected from a nozzle 38. This injected mixed power is molten by the plasma arc and subjected to hard facing by welding on the surface of the elongator plug 54. The hard facing material is then pulverized on a hard facing weld zone 58 and the, this is classified and the powder having particle size in a specified range is again supplied to the powder feeder 36. A molten liquid is again injected from the nozzle 38 by the same operation and hard facing by welding is performed on the surface of the elongator plug 54.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an overlay welding material for surface hardening in which carbides and the like in the overlay welding material used in plasma arc welding are atomized.

(Prior Art) A method of overlay welding alloy powder and carbide using a plasma arc is known. By this overlay welding, for example, by welding a predetermined overlay material to a workpiece such as a valve, pipe, or roll, the wear resistance and heat resistance of the workpiece surface can be improved.
Improves corrosion resistance, etc.

This plasma overlay welding method supplies alloy powder and carbide to be overlaid onto a workpiece during a plasma arc, melts this mixed powder and guides it to the surface of the workpiece, and performs a predetermined overlay. be.

(Problem to be Solved by the Invention) However, in such a conventional overlay welding method, when the weld overlay material is supplied as a powder into the plasma arc, carbides remain undissolved and are sufficiently fine particles. There is a problem that the weldability, toughness, and abrasion resistance of the weld overlay material are insufficient due to reasons such as the fact that it does not change.

The problem to be solved by the present invention is to improve the weldability, toughness, wear resistance, etc. of the build-up welding material by making the particles such as carbide in the build-up layer finer by the conventional method.

(Means for Solving the Problems) A method for manufacturing a surface hardening overlay welding material according to the first aspect of the present invention for solving the above problems includes supplying alloy powder and hard particles into a plasma arc. Overlaying the melted alloy,
After this overlay material is crushed, it is again fed into the plasma arc to overlay the melted alloy, and the hard particles in this overlay layer are finely dispersed.

The surface hardened product of the second invention of the present invention is the first surface hardened product described above.
The present invention is characterized in that a surface-hardening overlay welding material in which carbide particles are finely dispersed is overlaid using the manufacturing method of the invention.

As the alloy powder used in the present invention, Hastelloy C, Stellite, Nimonik, Ni powder, etc. can be applied.

Further, as the hard particles, NbC is used.

Carbide such as TaC, TiC, WC, VC, TiN.

Nitride such as BN, oxide such as Al2mOs, ZrO*, etc. can be applied.

In the manufacturing method of the present invention, after melting and pulverization using a plasma arc, plasma arc melting is repeated again, but the number of repetitions of plasma arc melting is not limited.

(Example) Embodiments of the present invention will be described based on the drawings.

First, a plasma overlay welding apparatus used in an example of the present invention will be explained. As shown in FIG. 3, the plasma device 1
0 has a tungsten electrode 12 in its center, and a torch inner cylinder 14 and a torch outer cylinder 16 outside this electrode 12.
are arranged coaxially at a predetermined distance from each other. and an annular passage 18.2 between the electrode 12 and the torch inner cylinder 14 and between the torch inner cylinder 14 and the torch outer cylinder 16.
0 is formed.

Plasma gas such as argon gas is supplied from the plasma gas supply device 24 to the passage 18 connected via the piping 22 . The plasma gas supplied into this passage 18 is ejected to the outside from a nozzle 30 provided at the tip of the torch inner cylinder 14.

The passage 20 is connected from the carrier gas supply device 34 via the pipe 32, and the powder supply device 36 is connected to the pipe 32 on the way.
is connected, and a predetermined mixed powder is supplied from the powder supply device 36. That is, a carrier gas containing a predetermined mixed powder is supplied from the pipe 32 to the passage 20 and is ejected from the nozzle 38 of the torch outer cylinder 16 to the outside. Further, as the carrier gas, an inert gas such as argon gas or helium gas is used.

Nozzle 30.3 of torch inner cylinder 14 and torch outer cylinder 16
Cooling water passages 40, 42 are provided in each of the nozzles 30, 8 to cool both nozzles 30, 38. Further, a shield gas supply device 4 is provided at the tip of the torch outer cylinder 16.
A shielding gas such as argon gas or helium gas is supplied from the torch 10 through a pipe 46, and by blowing out the shielding gas in a substantially cylindrical shape in the axial direction of the torch 10, the welding part is shielded. Ru.

A predetermined pilot current is supplied from a pilot power source 48 between the electrode 12 and the torch inner cylinder 14 of the torch 10 configured as described above. A predetermined welding current is supplied from the main power source 5° between the electrode 12 and the workpiece to be overlay welded, in this case the elongator plug 54.

A high frequency oscillator 52 is inserted between the electrode 12 and the torch inner cylinder 14 in parallel with the pilot power source 48 .

During overlay welding, first a pilot current is supplied from the pilot power supply 48 to generate a pilot arc between the tip of the electrode 12 and the nozzle 30 of the torch inner cylinder 14, and at the same time,
A plasma gas supply device 24 supplies plasma gas into the annular passage 18 .

As a result, a plasma arc is formed at the tip of the electrode 12. This plasma arc is generated in synchronization with the high frequency current supplied from the high frequency oscillator 52.

After that, a main power supply 50 is connected between the electrode 12 and the pulp 54.
A welding current is supplied from the valve 54 to perform predetermined overlay welding on the welded portion 58 of the valve 54. The time chart in this case is as shown in FIG.

That is, first, a welding current is applied to the torch l.

The plasma arc formed inside the elongator plug 5
4, and after a time t has elapsed, a carrier gas containing a predetermined mixed powder is supplied to the passage 20 from the carrier gas supply device 34 and the powder supply device 36, and is ejected from the nozzle 38. This ejected mixed powder is melted by a plasma arc and overlay welded onto the surface of the elongator plug 54.

Reference numeral 58 indicates an overlay weld.

Next, after pulverizing the overlay material to the overlay welding part 58, it is classified and powder having a particle size within a predetermined range is re-supplied to the powder supply device 3.
Supply to 6. If the powder is too fine, it will cause clogging, so it is classified to prevent this from happening. Then, by performing the same operation again, the molten liquid is ejected from the nozzle 38 and overlay welding is performed on the surface of the elongator plug 54.

A hardness test was conducted on the weld material of the overlay welded portion 58 thus obtained. The results were as shown in Table 1.

In addition, the mixing ratio of powder is 5 each for alloy powder and hard particles.
It was 0 vof2%. Moreover, the comparative example shows the results when plasma arc welding was performed only once. Among the hardness tests, the Vickers hardness test was conducted on the entire build-up structure in the Examples, and on the metal matrix portion in the Comparative Examples.

(hereinafter referred to as margin) As shown in Table 1, Rockwell hardness (Hrc)
The values of Vickers hardness (Hmv) are lower in the examples than in the comparative examples, and the values of Vickers hardness (Hmv) are more uniformly improved at the microstructure level in the examples than in the comparative examples, and the weldability is improved. It's getting expensive. From this, it was found that the examples were superior in toughness and wear resistance compared to the comparative examples.

Welding materials using a mixed powder of Hastelloy C and NbC were observed using an optical microscope. The results were as shown in FIGS. 1 and 2.

In FIGS. 1 and 2, FIG. 1 is a photograph showing the metal structure of the overlay weld material according to the embodiment of the present invention, and FIG.
The figure is a photograph showing the metal structure of an overlay welded material according to a comparative example in which plasma arc welding was performed only once.

In FIGS. 1 and 2, (A) shows a magnification of 100 times, and (B) shows a magnification of 400 times.

Comparing FIG. 1 with FIG. 2, it can be seen that the carbide particles in the example are much finer than in the comparative example, and are in fractional proportion.

Here, in the case of FIG. 1, carbide particles are considered to have been finely dispersed due to a carbide crystallization reaction.

30.38... Nozzle, 58...Overlay welding part.

(Effects of the Invention) As explained above, according to the method for producing a surface hardening welding material for surface hardening of the present invention, the hard particles in the welding material can be finely dispersed. The decentralized overlay welding material has the effect of having good properties in weldability, overlay performance, toughness, wear resistance, and workability.

Claims (1)

[Claims] (1) Supply alloy powder and hard particles into a plasma arc to build up the molten alloy, pulverize this overlay material, then feed it into the plasma arc again to build up the molten alloy. , a method for producing a welding material for surface hardening, which comprises finely dispersing hard particles in the material layer. (2) A surface hardened product characterized by being overlaid using the manufacturing method according to claim 1.