JPS62196320A - Method for remelting and chilling cast iron - Google Patents

Abstract

PURPOSE:To obtain a chilled layer contg. no remaining bubbles by a simple method by forming a chilled structure at a part to be remelted and remelting the part with a high energy heat source. CONSTITUTION:When a cast iron product is manufactured, a chilling block is placed in a metallic mold at the part corresponding to the part of the product to be remelted so as to crystallize a free cementite-base chilled structure to a depth larger than the desired depth of remelting and chilling. The part of the product is then remelted to the prescribed depth with a high energy heat source and the remelted part is rapidly cooled. Thus, a chilled layer having a fine chilled structure of high hardness can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention H11,i relates to a method for remelting and chilling a desired portion of a cracked iron product.

[Conventional technology and its problems]

As a method to improve the wear resistance of a desired specific surface of a pig iron product, it is possible to apply energy rays such as laser f, TIG arc, plasma arc, and 'Kameko beam' in an inert gas atmosphere to the energy rays of the Kameko beam in a vacuum atmosphere. We partially re-melt only the surface of a specific desired part of a cast iron product, and use the product's self-cooling ability to rapidly cool the re-melted part to form a fine chilled structure with high hardness, resulting in wear resistance. It is known to improve overall health.

By the way, when this re-melting chilling method is applied to general gray cast iron, the graphite in the cast iron matrix exists as relatively coarse flake graphite, so it is melted by a high energy source. Because graphite does not quickly enter the bath and is highly activated, it is 1! Co and CO2 gases are generated by combining with F elements and oxygen in the atmosphere, and during the cooling process of the melt, the core gases remain in the chilled layer in the form of bubbles, worsening the surface roughness after grinding and acting as internal defects. Problems such as peeling occurred frequently.

In addition, in order to prevent this phenomenon, we have developed a method of preheating cast iron products to a temperature of 400C to 600 tl prior to remelting, delaying the cooling of the molten part, and releasing bubbles into the entire atmosphere, and using a high energy source. It is conceivable to heat pig iron products by slowing down the scanning speed and increasing the amount of heat input, but these methods reduce the self-cooling ability, and for this reason, P +
I! There are problems in that scales that cannot obtain a molten chilled structure require a preheating device or forced cooling means.

[Purpose of the invention]

The object of the present invention is to provide a simple process for remelting and chilling a chilled layer without residual K L v bubbles.

[Structure of the invention]

The present invention is characterized in that after the chilled structure of a predetermined depth is completely formed in the area to be subjected to remelting and chilling treatment, remelting is performed using a high energy source to completely form the LD fine chilled fibers. We have been thoroughly investigating the p+ bath melt-chilling method for cast iron in order to obtain all bubble-free re-melt chilling If II, and found that the parts to be subjected to the re-melt chilling treatment were pre-heated to the re-melt chiller. We have discovered that by forming a chilled structure with a deep depth in the generated chilled layer and performing remelting and chilling using a controlled energy source, it is possible to obtain a chilled layer metal free of all air bubbles. This led to the invention of this invention.

The present invention will be explained in detail below.

First, cast iron products? When manufacturing, a cooling metal is placed in the mold in a part corresponding to the part of the product to be remelted. Then, the entire surface of the area is heated to a predetermined depth of 1 by applying an energy heat source to the target area for re-melting and hardening treatment to fully crystallize the chilled structure mainly composed of free cementite. By rapidly cooling the material after remelting, a chilled layer consisting of a fine chilled structure F with high =9 hardness is formed.

In the present invention, by roughly finishing the entire chill layer formed in the remelting treatment area into a predetermined shape, the remelting chill hardening layer can be set to be thinner, which reduces the amount of heat input.
Not only does the quenching effect become large and a chilled layer with daytime hardness is obtained, but the surface roughness during remelting is also small, so the amount of polishing after remelting and chilling is reduced, and the chilled hardened layer disappears. Never.

Well, since the remelting part is pre-chilled, relatively coarse graphite is not present, thus suppressing the formation of blowholes (bubbles) and reducing the formation of cracks that normally form along the graphite. is also suppressed.

Hereinafter, the present invention will be explained in detail based on comparative examples and examples.

Comparative Example 1 A gray cast iron material was passed through a TIG arc remelting process to form a chill layer of 1 m++ in advance, and then remelted and surface hardened using the same method to a depth of approximately a and S■.

Processing conditions: fiifi 60 A, voltage 7.2 m'V
, 14 pole distance 1 short.

Torch moving speed 25 min/sec, shielding gas Ar, gas flow rate 717 min, preheating temperature 200 ℃ After the treatment, the entire tar surface of the chill layer was prepared, and macroscopic observations were made at the position where the remelted zone reached the base material graphite. The occurrence of blowholes was observed.

Example 1 During hook making, the entire chill layer was formed to a depth of 3 meters or more, and a flat tappet was subjected to TIG melt hardening treatment to a depth of about 2 meters.

Processing conditions S! 1100A, voltage t2mV, electrode distance 1■
, torch movement speed 25s/sec, shielding gas Ar,
Gas flow rate was 717 minutes, and preheating temperature was 500°C. After the treatment was completed, the cross section of the chilled layer was examined, and almost no cracks or blowholes were observed.

Claims (1)

[Claims] Remelting and chilling of cast iron, which is characterized by forming a chilled structure of a predetermined depth in advance in the area to be remelted, and then remelting using a high energy source to form a finer chilled structure. Method.