JPS61195918A - Method for locally alloying and chilling cast iron - Google Patents

Abstract

PURPOSE:To improve the wear resistance of cast iron by putting an alloy contg. Cr, Mo or Ni on part of the surface of the cast iron and by melting the alloy together with part of the base metal so as to form an alloyed and chilled layer on the part of the surface of the cast iron. CONSTITUTION:An alloy contg. one or more among Cr, Mo, Ni, Nb, V and Cu is put on part of the surface of cast iron and melted together with part of the base metal with high density energy as a heating source, and the resulting melts are rapidly cooled. An alloyed and chilled layer is formed at the remelted and solidified part of the base metal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for surface chilling cast iron, and more particularly to an alloying chill method in which surface chilling and surface alloying are carried out simultaneously.

BACKGROUND OF THE INVENTION Chilling treatment has traditionally been used as a surface hardening method for cast iron. For example, the contact surfaces of camshafts, valve lifters, rocker arms, etc. made of cast iron are subjected to chilling treatment. This chilling treatment has conventionally been carried out by applying a cold metal to a portion of the casting during solidification to rapidly solidify the casting. In addition, in recent years, in order to further improve performance such as fatigue strength and abrasion resistance obtained by chilling, and to reduce costs, TIG BACKGROUND OF THE INVENTION Increasingly, methods are being used to partially remelt the surface of materials using high density energy heating sources such as arcs and lasers.

Problems to be Solved by the Invention However, the above conventional chilling treatment methods have the following problems.

In other words, in the conventional chilling treatment method described above, whether a chilled metal is used or a high-density energy heating source is used, the performance such as wear resistance of the resulting chilled part depends on the material of the base cast iron. Specifically, when using various alloy cast irons, the performance value is high, but when using ordinary cast iron, the performance value is lower than when using alloy cast iron.Therefore, the required If the performance value is relatively low, ordinary cast iron can be used, but if the required performance value is high, expensive alloyed cast iron must be used as the base material cast iron, which raises the problem of high costs. .

This invention has been made in view of the above-mentioned conventional circumstances, and it is a cast iron that can obtain performance such as wear resistance equivalent to that when using alloy cast iron even when ordinary cast iron is used as the base material cast iron. The object of the present invention is to provide a local alloying chill method.

According to the means for solving the problem, that is, the method for locally alloying and chilling cast iron of the present invention, Qr.

A material containing one or more elements among Mo, Ni, V, Nb, and Cu is placed, and the material is melted together with a part of the base material using a high-density energy heating source, and the base material is rapidly cooled. It is characterized in that a chill layer is formed in a part of the remelted and solidified area.

The method for locally alloying and chilling cast iron according to the present invention will be explained in more detail below.

As the cast iron, normal cast iron such as Fe12 can be used. As the material containing one or more elements among Cr, Mo, Ni, V%Nb, and Cu, alloy cast iron powder, alloy iron/alloy steel powder, or plate material containing these elements can be used. The material can be applied to the desired surface of the cast iron by applying it as a slurry using a suitable binder, such as polyvinyl alcohol, or by thermal spraying to form a film.

High-density energy heating sources include TIG arcs, lasers, plasma arcs, electron beams, and the like.

In this invention, the above-described high-density energy heating source melts a part of the cast iron base metal as well as the alloy material placed on the base metal, so that at the same time as heating is stopped, the unmelted portion of the base metal is re-smered. Heat diffuses at an extremely high speed, and the remelted part rapidly solidifies and becomes chilled. The alloy material placed on the 1Iffi material is alloyed in the remelted and solidified portion, and the obtained chill layer has extremely good performance.

The above-mentioned Cr, Mo, Ni, V, Nb%Cu are added for the following reasons.

(1) Cr Generates carbide in the base of the resulting chilled layer to improve wear resistance. From this point of view, it is desirable that Qr be added to the resulting chilled layer in an amount of 0.2 to 5.5 wt%.

(2) M.

Generates carbide to improve wear resistance. It also has the effect of significantly improving creep properties and increasing shearing strength.

From that point of view, the amount of MO in the resulting chilled layer is 0.3~
It is desirable that it be added to an extent of 1.2 wt%.

(3) Ni is solid-dissolved in the base of the obtained chilled layer to strengthen the base. It also prevents low temperature brittleness. From that point of view, Ni is 0.1 to 3
It is preferable that it is added to a final content of 6.0 wt%.

(4) ■ Generates carbides to improve wear resistance. From this point of view, it is desirable to add it to the chill layer in an amount of 0.1 to 1.2 wt%.

(5) Nb Generates carbide to improve wear resistance and has the effect of making crystal grains finer. From that point of view, 0.1
It is desirable that it be added in an amount of ~1.2 wt%.

(6) Cu Solid solution in the base strengthens the base and also has the effect of improving corrosion resistance. From that point of view, 0.2 to o, yw is applied to the chill layer.
It is desirable to add it to the extent that it is contained in an amount of t%.

Example Examples of this invention are described below.

Example 1 Chill treatment was applied to the camshaft sliding surface of a 4-stroke Recip O engine. Fe12 was used as the base material cast iron, and alloyed cast iron powder having a grain size of 150 to 250 mesh was applied to the part of the base material cast iron to be subjected to the chill treatment, using polyvinyl alcohol as a binder, at a coating thickness of 1 m2. The alloy cast iron containing 1.0% Qr and 0.6% MO was used. The relative movement speed is approximately 211/S with respect to the alloy powder coated part.
It was irradiated with a TIG arc as ec, and was melted and solidified together with a part of the base material cast iron to obtain an alloyed chill layer.

Example 2 Alloy cast iron containing 1.0% Cr and 0.6% MO,
A material containing approximately 0.3% V was used, and the other conditions were the same as in Example 1, so that the sliding surface of the camshaft of a 4-stroke reciprocating O engine was subjected to chill treatment.

Comparative Example 1 Fe12 was used as the base cast iron, and the camshaft sliding surface was subjected to chill treatment under the same conditions as Example 1, except that alloy cast iron was not placed on the part of the base cast iron to be chilled. did.

Comparative Example 2 A camshaft sliding surface was subjected to a chill treatment under the same conditions as in Example 1, using alloy cast iron containing 05% QrO and 0.3% Mo as the base cast iron.

The thickness and hardness of the chill layer of the camshafts obtained in each of the above Examples and Comparative Examples were measured. The measurement results are shown in Table 1 together with the processing conditions of each Example and Comparative Example.

Further, after the processed camshafts of each example and comparative example were machined and finished, they were assembled into a gasoline engine with a displacement of 2000 cc, and a motoring test was conducted to evaluate wear resistance. The opposing rocker arm pad surface on which the camshaft sliding surface slides was formed by carburizing and quenching a 5Cr430 material and then plating it with hard Cr. The engine speed of the motoring test was 2000 rpm, and the trial time was 400 hours.

After the motoring test, the maximum amount of wear on the camshaft sliding surface was measured. The measurement results are shown in Figure 1.

As can be seen from Table 1, the thickness of the chill layer was approximately 2 cm in all cases. On the other hand, the hardness of the chilled layer differs for each piece, and the chilled layer of Comparative Example 1, whose base material is Fe12, has a hardness of approximately H
V635, whereas Comparative Example 2, in which alloyed cast iron is the base material, has a high HV680. However, in Example 1 in which this invention was implemented using Fe12 as a base material, Comparative Example 2
The same level as Hv670! i! degree has been obtained,
Furthermore, in Example 2, a hardness of Hv695, which is higher than that in Comparative Example 2, was obtained.

Furthermore, as can be seen from Figure 1, the amount of wear l in the motoring test was the highest in Comparative Example 1, and the amount of wear in Comparative Example 2, which was made of alloyed cast iron base material, was significantly lower than that in Comparative Example 1. few. However, as in Comparative Example 1, in Examples 1 and 2 in which the present invention was implemented using Fe12 as a base material, the amount of wear was even smaller than in Comparative Example 2.

In each of the above examples, an alloy powder containing Cr, Mo, or V was used, but in addition, alloy powder containing Ni, Cu,
, Nb, etc. also function as elements that strengthen the lithium layer by strengthening the matrix and forming carbides, and alloy powders containing them can also be used.

Effects of the Invention As described above, in the method for locally alloying and chilling cast iron of the present invention, an alloy material is placed on the surface of the cast iron, and the material is melted together with a part of the base metal using a high-density energy heating source, and then rapidly cooled. By doing so, even if the alloying elements in the Tri material cast iron are reduced or eliminated, it is possible to form a chill layer that has wear resistance equivalent to or higher than that in the case of using alloyed cast iron.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a comparison of the amount of wear in a motoring test of camshafts processed according to an embodiment of the present invention and a comparative example. Applicant Toyota Motor Corporation Representative Patent Attorney Yutaka 1) Hisashi Take (and 1 other person)

Claims (1)

[Claims] Cr, Mo, Ni, V,
An alloy material containing one or more elements among Nb and Cu is arranged,
A local part of cast iron characterized in that the material is melted together with a part of the base metal using a high-density energy heating source and rapidly cooled to form an alloyed chill layer at the part of the base metal that remelts and solidifies. Alloying chill method.