JPS61194166A - Treatment for remelting and hardening - Google Patents

Abstract

PURPOSE:To make a treatment for remelting and hardening without generating the unevenness of an additive alloy by superposing impulsive current to DC arc current to be supplied to a plasma torch and oscillating a molten base material layer thereby stirring the additive alloy components. CONSTITUTION:A plasma torch 1 is so disposed that the nozzle part 1a thereof faces the base material 2 apart at a prescribed space therefrom. A W electrode is contained in the nozzle part 1a and a shielding gas such as inert gas, additive alloy powder and working gas such as gaseous Ar are ejected from an ejection port provided at the suitable point thereof. An arc is further generated between the torch electrode and the base material 2 in the above-mentioned shielding gas by a DC arc power source 5, by which the working gas is made to plasma. A plasma arc of a high temp. and high flow rate is blown to form a molten pool 4. The pulse current from a pulse current generator 6 is superposed on the above-mentioned arc current by a superposer 7 to oscillate the pool 4, thereby stirring the additive alloy powder. The additive alloy components are thereby uniformly dispersed and the treatment layer solutionized by remelting and hardening is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for remelting and hardening camshafts and the like.

(Prior art) Parts of the surface layer of cast iron parts, such as the surface of the cam part of a camshaft and the tip part of a rocker arm, come into sliding contact with other parts, so these parts have better wear resistance than other parts. It is required to have excellent properties such as hardness and pitting resistance. For this reason, the surfaces of these cast iron members are subjected to remelting hardening treatment (remelting treatment).

This remelting hardening process involves placing a plasma torch at a predetermined distance from the workpiece (base material), which is usually a cast iron member.
This plasma torch is used to re-melt the surface of the workpiece, and then the melted portion is rapidly cooled to form a chilled layer.

(Problems to be Solved by the Invention) Conventionally, DC current has been used as the arc current supplied to this plasma torch. For this reason, the energy of the plasma arc supplied to the surface of the base material remains constant over time, and as a result, the molten layer (molten pool) that forms on the surface of the base material becomes gentle with little fluctuation, causing a flow phenomenon. Therefore, the added alloy particles accelerated by the plasma gas and entered are not sufficiently captured in this molten pool, and the resulting remelted layer contains no added alloy particles in both the depth direction and the planar direction. Unevenness occurs in the alloy.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a remelting hardening treatment method in which an additive alloy is uniformly dispersed and solid-solved in a remelting treatment layer, and no unevenness of the additive alloy occurs.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a plasma torch (1
By superimposing a pulsed current on the DC arc current supplied to the base metal molten layer (0), the added alloy components added during the remelting and hardening process are stirred and the added alloy components are remelted. Treated layer (uniformly dispersed and solid-dissolved in 0).

(Function) The molten pool (molten layer) that is generated in the base material (2) by superimposing a pulsed current on a DC arc current changes its shape at the peak of the pulsed current and at the base current, causing oscillations. A dynamic phenomenon occurs, and the added alloy is stirred while being oscillated accordingly, and the added alloy can be uniformly dispersed and dissolved in the remelted layer (4).

(Embodiment) A preferred embodiment of the present invention will be described below based on the accompanying drawings.

51 is a diagram schematically showing the configuration for implementing the method according to the present invention. In FIG. 1, reference numeral (1) is a plasma torch that is disposed with its nozzle part (la) facing the base material (2) with a predetermined gap therebetween, and this plasma torch (+) is driven by a drive device (not shown). It is movable vertically and horizontally. The nozzle part (la) of this plasma torch (1) has a built-in electrode made of tungsten or the like, and in the appropriate places there is a shield gas such as an inert gas, a working gas such as argon gas, and an ejection port for the additive metal powder. Equipped with etc.

In such a configuration, the base material (2) is used as the other electrode, and when an arc is generated between the torch electrode and the base material (2) in the shielding gas and the working gas and additive metal powder are ejected, the working gas turns into plasma and reaches a high temperature. It becomes a high-speed plasma arc (3) and is blown onto the surface layer of the base material (2), forming a molten pool (0) in this area.Additional metal powder penetrates into this molten pool and is chilled. The surface of the base material (2) will be subjected to remelting and hardening treatment.

By the way, reference numeral (5) is an arc current supply source for supplying a DC arc current to the electrode of this plasma torch (1) to generate an arc between the electrode and the base metal. FIG. 2 is a diagram showing the DC arc current supplied from this arc current supply source with time on the horizontal axis and magnitude on the vertical axis. On the other hand, reference numeral (8) is a pulse current generator, and FIG. 3 shows this pulse current in the same way as FIG. 2, and this pulse has a pulse width TI and a period (TI + T2). This pulse current is then superimposed on the DC arc current by a superimposer (7) and supplied to the electrode of the plasma torch (1).

Figure 4 shows the arc current in which a pulse current is superimposed on this DC arc current, similar to Figures 2 and 3, and the arc current (8) is shown at the peak of the pulse current (8a) and at the base current. In (8b), we have two detectives of different sizes.

FIG. 5 is a diagram showing a molten pool formed by the arc current obtained in this manner. The molten pool (9) indicated by the dotted line in Fig. 5 is obtained at the peak of the pulse current (8a), and since the energy of the plasma arc is large at this time, the central part (9a) of the molten pool (8) is deep,
The peripheral portion (8b) is greatly raised. On the other hand, the molten pool (!O) shown by the solid line is obtained at the base current (8b), and at this time the plasma arc energy is smaller than the former, so the central part of the molten pool (1G) ( '
10a) is shallow, and the swell around it (10b) is small. Therefore, a flow phenomenon occurs due to the difference in the shape of the molten pools (9) and (10), and the added alloy that is accelerated by the plasma arc and enters the molten pool is stirred by this flow phenomenon and is uniformly dispersed in the molten layer. , solid solution.

According to experiments, the frequency of pulses in this method is 2~
It is possible to use 30Hz, and good results are obtained especially at 5 to 20H2, and the pulse width TI is equal to the period (TI +72
) can be used, and particularly good results are obtained when this value is 20 to 80%.Furthermore, the ratio of the current at the peak of the pulse to the current at the base current is 1.5 to 80%. Good results can be obtained in 15, especially in 2 to 10.

(Effects of the Invention) As is clear from the above description, according to the present invention, the additive alloy can be uniformly dispersed and solid-dissolved in the remelting treatment layer, and the additive alloy can be uniformly remelted and hardened. can be provided.

[Brief explanation of the drawing]

Fig. 1 is a diagram schematically showing the configuration of an embodiment of the present invention, Fig. 2 is a diagram showing DC arc current, Fig. 3 is a diagram showing pulse current, and Fig. 4 is a diagram showing DC arc current. FIG. 5 is a diagram in which a pulse current is superimposed on the molten pool. In the drawing, (1) is a plasma torch, (0° (9)
, (10) is a molten pool (base material molten layer).

Claims (1)

[Claims] In a method of remelting and hardening using a plasma arc as a heat source, a pulsed current is superimposed on a DC arc current,
A remelting hardening treatment method characterized by shaking the base material molten layer to stir the additive alloy added during the remelting hardening treatment, thereby uniformly dispersing and solid-dissolving the additive alloy in the remelting treatment layer. .