JPS58116967A - Casting method of shaftlike casting - Google Patents

Abstract

PURPOSE:To improve the melt sticking to an inside layer material by coating a low m.p. flux on the inside surface of an outside shell layer, then injecting and introducing an early combustion type high exothermic flux plural times with an inert gas onto said surface thereby insulating the heat on the inside surface of the outside shell layer. CONSTITUTION:First a flux of a low m.p. for preventing oxidation is injected onto the inside surface of an outside shell layer obtained by centrifugal casting, whereby the flux is coated thereon. Immediately after said injection, an exothermic flux of early combustion type within about 3min until peak temp. is attained and having about >=1,800Kcal total calorific value per ton of molten letal is introduced and injected, with an inert gas as a carrier gas, onto the inside surface of the outside shell layer to insulate the heat on said surface by the heat evolved by said flux. Since the calorific value of the flux decreases in about 6-10min, it is necessary to use the same repeatedly a number of times. The amt. of the flux to be charged in each time is about 2.0-5.0kg/m<2> per area of the inside surface of the outside shell layer. Thus, an inside layer material is melt-stuck satisfactorily to the inside surface of the outside shell layer.

Description

[Detailed Description of the Invention] This invention relates to a method for casting shaft-shaped castings, and is particularly characterized in that heat is maintained by introducing a highly exothermic flux into the inner surface immediately after the step of casting the outer shell layer. This method is suitably used for casting composite rolls for hot rolling rolls.

General K, rolling rolls used in steel mills have an inner layer (
The core part) is made of a highly tough material that is strong against impact and stress, while the outer layer part (body shell) is made of a material with excellent shore abrasion resistance.51P#l! It is usually manufactured by a composite casting method based on For example, for a cylindrical shell-shaped outer shell layer manufactured by centrifugal casting, its internal Km! II metal inner layer #! The method is to pour hot water into them and let them coalesce.

What is important in the above casting method is to prevent oxidation of the previously cast outer shell layer, especially the inner surface, until the injection of the inner layer f6fjh, and to prevent the diffusion of the 1 m molten metal that precedes and follows. The objective is to minimize the temperature drop as much as possible. In contrast, conventional methods have only injected flux to prevent oxidation. This resulted in the following problems.

■ Because the temperature drop is large and a solidified layer is generated from the inner surface of the outer shell layer, poor welding with the inner layer material is likely to occur.

■ Since the inner surface temperature of the outer shell layer has fallen, the temperature of the inner layer material that is poured later must be raised considerably. (+70 to 100"C higher than the casting temperature of the outer shell layer) ■ Since solidification also proceeds from the inner surface of the outer shell layer, defects such as segregation zones and rough spots tend to concentrate near the center of the outer shell layer.

The present invention aims to overcome the problems of the conventional casting techniques described above, and an effective method for this purpose is to generate a solidified shell on the inner surface of the outer shell layer.

In order to suppress growth as much as possible, this technology uses a fast-burning, highly exothermic flux. Therefore, a decrease in the inner surface temperature of the outer shell layer and oxidation are prevented, thereby achieving the desired outer shell layer-inner layer welding. The details of the configuration of this invention will be explained below.

The casting method of the present invention is characterized by the fact that the inner shell layer 1ii obtained by centrifugal force casting is
First, a low-melting-point oxidation-preventing flux is injected in a conventional manner to form a coating. And, following the operation, it is an early combustion type that reaches the peak temperature immediately within 3 minutes, and the total calorific value per ton of molten metal is /1ail)KceL1
The above exothermic flux is introduced and injected using an inert gas as a carrier gas, and the heat generated by the flux keeps the inner surface of the outer shell layer warm. /lI! 10℃, cast steel type 〇〇 -
The temperature is 1110°C. In the case of cast steel, the flux used in response to these is kl: Jj%-kl, 03
: /! %-FeO2j%-Bo: 3o%-8102
' : A flux with the properties as shown in 8a in Figure 1, which has a composition of /%, is used, and for cast iron, a flux with properties as shown in b in the figure is used.
: /j%-FeO: 7%-B, O,: 3j%-
51o□: Composition K of body % If such a composition is used, the necessary amount of heat can be obtained.

However, since the heat value of the above flux decreases after about 4 to 10 minutes, it is necessary to use it repeatedly. Generally speaking, the average time until the molten inner layer material is injected after casting the outer shell layer is approximately /j minutes, so in general, introduction only once is insufficient. The amount of flux thrown each time is 1.0~z,okl'2(
(per inner surface area of the outer shell layer).

Next, embodiments of this invention will be described.

Outer shell layer material Adamite material (C=8 to 3%, Si0.10%
, N1=0.9j%, Cr=/,0! r%1M0
= 0.30%)! After pouring the metal into a centrifugal casting mold at θ℃ to form an outer shell layer, normal oxidation-preventing flux is injected within 40 seconds, and immediately after that, exothermic flux (
*I = , yr%, Aj20. = /j%, F
eO: 3%, BO=30%, 8i0=/7%
) to koej atuni 223
2 m of sweet potatoes were added at intervals as shown in Figure 1. In this example, the waiting time before pouring the inner layer material is /41 minutes (outer shell layer amount = coj
ton), but in order to adapt it to the present invention, the waiting time was set to 30 minutes, but the welding of the outer shell layer and inner layer was sufficient because the temperature was maintained high enough for casting. Ta.

Furthermore, after casting the outer shell layer when pouring the inner layer material, it was found that Aj @ electric (outer shell layer thickness: tOvan ) K was different, and the outer shell layer was directional solidified.

As explained above, according to the present invention, it is possible to lengthen the time until the inner layer material is poured, so that the casting work can be carried out without difficulty. Moreover, since directional solidification of the outer shell layer is achieved, a ring-shaped casting can be obtained which is effective in preventing segregation near the boundary with the inner layer, has excellent bonding properties, and has sound internal properties.

[Brief explanation of the drawing]

FIG. 1 is a diagram of heat generation temperature characteristics of exothermic flux, and FIG. 1 is a graph of changes in temperature inside the outer shell layer when flux is repeatedly injected. Patent Applicant: Kawasaki Steel Corporation Figure 1: Mine Time (Now)'' Figure 2: #kMLgItl!1JIIC Now

Claims (1)

[Claims] t After casting a cylindrical shell-shaped outer shell layer by centrifugal force casting, an inner layer material of a heterogeneous metal is poured into the shell layer and combined to produce a ring-shaped casting. If a low melting point flux is applied to the inner surface of the nuclear shell layer and then an early combustion type high exothermic 7 lux is injected into the inner surface of the nuclear shell layer via an inert gas, the inner surface of the nuclear outer shell layer will be A method of casting ring-shaped castings characterized by keeping them warm.