JPS58100621A - Surface hardening method for metal - Google Patents

Abstract

PURPOSE:To carry out stable and effective hardening without remelting the surface of a material to be treated by forming a layer of a metal having a low m.p. on the surface of the material to be treated and by applying heat energy with arc to evaporate the low m.p. metal. CONSTITUTION:A layer of a metal having a low m.p. such as solder is formed on the surface of a material to be treated such as cast iron by rubbing or other method, and by applying sufficient heat energy with arc, the low m.p. metal is evaporated. Thus, the surface of the material to be treated can be maintained at a temp. below the remelting temp., and since arc goes straight toward the vapor, the surface of the material to be treated is subjected to effective transformation hardening.

Description

[Detailed Description of the Invention] The present invention relates to a metal surface hardening method using an arc.
In particular, the present invention relates to a metal surface hardening method that can obtain a stable hardened structure without remelting the surface of the treated material.

Conventionally, for transformation hardening of the surface of metal materials such as steel or cast iron, surface hardening has been performed using an arc in TIG welding or plasma arc welding. However, in this method, the energy density due to the arc is very high, so there is a problem that the surface of the material to be treated may be remelted. In order to avoid remelting the surface of the material to be treated, if the energy density of the arc is lowered, the arc will become unstable such as wandering or breaking, so hardening cannot be performed at specific locations. Otherwise, the hardening effect will be insufficient.

An object of the present invention is to provide a metal quenching method that can perform effective 1: quenching by stable quenching treatment without causing remelting of the material to be treated.

The present invention provides a low contact point metal layer that evaporates at a temperature lower than the melting point of the processed material on the surface of the processed material, and applies sufficient thermal energy to evaporate the low contact point metal layer using an arc. However, when this low contact point metal is evaporated, the temperature of the surface of the material to be treated is maintained below the remelting temperature of the material to be treated, and 1-, the arc has the property of traveling straight toward the vapor. This was achieved as a result of the discovery that the surface of the material to be treated can be effectively (-transformed) hardened.

The present invention will be explained in more detail below.

In the present invention, the material to be treated is not particularly limited as long as it can be hardened, such as carbon steel, low alloy steel, and high alloy steel. The low contact point metal layer formed on the surface of the material to be treated is made of a metal that evaporates at a temperature much lower than the melting point of the material to be treated. Therefore, the low melting point metal is selected appropriately depending on the type of material to be treated, but specifically, metals with a low melting point are metals such as iron, zinc (''), and aluminum. Ni (mul), antimony (sb), sulfur (s), cadmium (Od), tin (
8n), selenium (S), bismuth (Bi), thallium (TI), tellurium (Tθ), sodium (N-), lead (
pb), neptunium (Ip), polonium (Po)
, lithium (Ll), phosphorus (P), and the like. ,) The low melting point metal layer can be formed by rubbing a low melting point metal onto the surface of the material to be treated, by brushing fine powder of a low melting point metal, by vapor deposition, by ion grating, by spraying a suspension of a low melting point metal, etc. formed by. Among these methods, the method of rubbing . First, the low melting point metal 1 does not need to be formed on the entire surface of the material to be treated, but may be formed at any location that requires hardening on both surfaces. Therefore, it is possible to improve the strength and wear resistance of the surface of parts, so it is particularly effective for surface treatment of automobile parts such as crankshaft pins, journal shoulders, or inner surfaces of cylinder bores.

Example 1 The surface of the material to be treated (gray cast iron, equivalent to Tr87C25) was moved by hand without rubbing (test piece B).

The treated materials (test pieces M, C) without solder applied to both sides of this test piece B were arranged in parallel, and test pieces M~Test pieces C:;
4, an extremely low current (average current 7.5 μm, peak current 10 μm, pace electric current) was applied at a torch speed (10 Cwh/min) using a Pulste G welding machine, and surface hardening was performed by arc. FIG. 1 is a photograph showing the surface condition of the test piece at this time.

According to Figure 1, the beats of specimens M and C are not linear but oscillate, indicating that the arc is in an unstable state. On the other hand, in specimen B, the beat is linear, thus indicating that the arc is extremely stable.

Next, FIGS. 2(B) and 2(B) respectively show an enlarged surface view (XiO) and a cross-sectional view (XIIQ) of the surface of the test piece where the beats were formed. According to FIG. 2, it can be seen that the area just below the surface of the test piece was completely remelted and carbide was generated.

FIGS. 3(B) and 3(B) are enlarged views of the surface of the test piece B (Example) where the beats were formed (X t
o) and the cross-sectional structure (X50) are shown.

According to FIG. 3, not only is the area affected by the heat of papermaking not remelted by the arc, but the structure is completely quenched (martensite) directly under the arc.

Example 2 Material to be treated (JIS Fe12 material with Cr and Mo), N1
Rub solder on the surface of a piece of low-alloy cast iron (containing low-alloy cast iron) (test piece), place test pieces without solder in parallel adjacent to one side of test piece E, and test these test pieces D~ A current was applied to the surface of each specimen D%1 with an average current of 20 μm (peak current 30 μm, base current 10 μm) by moving the torch at a speed of 10 C117 minutes depending on the machine. , the surface of the test piece was hardened.

FIG. 4 is a photograph showing the surface condition of the test piece at this time. In this example, a higher current is used than in Actual Example 1, so that the test piece is separated.II! In either case, there is no deviation in the beat due to arc deviation, and the beat is linear.

Figures 6 (M) and (B) are an enlarged surface view (X10) and a cross-sectional structure (X
50). According to Figure 5, the test piece consists of a remelted area and a transformed area (martensite) formed around this area.
It can be seen that it consists of 21 organizations.

Figures 6 (M) and (B) are an enlarged surface view (XI O) and a cross-sectional structure (
X50). In FIG. 6, in the test piece m (Example), no remelted parts as seen in the test piece were observed, and the structure immediately below the surface was a completely quenched structure (martenized).

Example 3 Using aluminum and tin as the low melting point metals, Yoshinoki performed surface quenching treatment in the same manner as Example 1, and the material to be treated was completely quenched without any re-melting. I was able to do that.

According to the present invention, a low melting point metal layer is provided on the surface of the material to be treated, and the surface of the material to be treated is hardened by applying heat energy sufficient to evaporate the layer to this layer using an arc. Since the heat energy generated by the arc is absorbed by the low-melting point metal, the temperature of the surface of the processed material can be easily maintained below the remelting temperature of the processed material, preventing deformation of the processed material, and Since the arc has straight-line propagation in the vapor of the low melting point metal, surface hardening can be performed stably even with an extremely low current arc.

[Brief explanation of the drawing]

Figure 1 is a photograph showing the surface condition of specimens M to C in Example 1 after surface hardening by arc;
B)! Micrographs showing the surface and cross-sectional structure of test piece A in FIG. 1, respectively; FIGS. 3(A) and CB) show microphotographs showing the surface and cross-sectional structure of test piece B in FIG. 1, respectively;
Figure 4 is a photograph showing the surface condition of the test piece in Example 2 after surface hardening by arcing, and Figures 2 (M) and CB) are the surface and cross-sectional structures of the test piece in Figure 4, respectively. 6A and 6B are microphotographs showing the surface and cross-sectional structure of the test piece E in FIG. 4, respectively. Representative Tatsuyuki Unuma (and 2 others)

Claims (1)

[Claims] (1) A low melting point metal layer that evaporates at a temperature lower than the melting point of the material to be treated is provided on the surface of the material to be treated, and the metal layer is heated while applying sufficient thermal energy to evaporate the low melting point metal layer using an arc. A metal surface hardening method characterized by hardening the surface of the treated material.