JPS60223650A - Flux for two-layer centrifugal casting - Google Patents

Abstract

PURPOSE:To provide the titled flux which improves floatability to the inside surface of an inside layer and permits thorough welding of the boundary between the inside and outside layers by compounding SiO2+B2O3, CaO+BaO+ Na2O and CaF2+NaF within a specific mol% range and applicably. CONSTITUTION:The flux for two-layer centrifugal casting is composed of 30- 70mol% SiO2+B2O3 (>20at% SiO2, <30% B2O3), 50-80% CaO+BaO+2Na2O (>15% Na2O) and <=30% 2.CaF+NaF and is so formulated that the value of the formula indicating the ratio between the basic flux and fluoride as well as acidic flux satisfies 1.0-2.0. This flux has small surface tension and low viscosity even if the temp. of the inside surface of the outside layer is decreased in the stage of pouring the inside layer and therefore the flux has excellent floatability on the inside surface of the inside layer. The flux is applicable advantageously for casting of a two-layered hollow centrifugal roll which has a uniform thickness of the inside and outside layers and has the thoroughly welded boundary thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a fluff used in a two-layer centrifugal casting process, particularly in a process for manufacturing a two-layer centrifugal casting roll.

(Summary of conventional technology) K manufactures a 92-layer roll using the centrifugal casting method. After pouring the molten metal that forms the outer shell layer, pouring the molten metal that forms the inner shell layer to fuse the inner and outer layers. However, before the inner layer molten metal is poured, the inner surface of the outer layer molten metal comes into contact with the atmosphere and forms an oxide film. If this oxide film is formed firmly, it becomes difficult to completely fuse the inner and outer layers even if high-temperature molten metal is poured into the inner layer.

In order to prevent the formation of this oxide film, flux is conventionally added before and after pouring the outer layer. This flux includes a mixture of soda ash and limestone, a mixture of crushed sand and borax,
A mixture of glass powder and soda ash has been proposed. These 72x can also prevent the formation of an oxide film to some extent, but in order to manufacture hollow rolls with uniform thicknesses of the inner and outer layers, the temperature of the inner surface of the outer layer is kept below the freezing point when pouring the inner layer, so that the flux is uniformly distributed and the inner layer is coated from the inner surface of the outer layer to the inner layer. The floating separation to the inner surface is not sufficient, and changing the casting conditions often results in either contradictory phenomena such as poor welding or uneven thickness of the inner and outer layers due to partial excessive melting loss, which often leads to a decrease in yield etc. I was imitating it.

(Objective of the present invention) In order to obtain a two-layer roll with a uniform thickness of the inner and outer layers as described above, the melting time during flux injection is shortened under casting conditions in which the inner layer is poured after the outer layer is poured and solidified. It is necessary to select a flux composition that improves the buoyancy of the flux to the inner surface of the inner layer. Therefore, the present invention aims to provide a flux that has a low surface tension and low viscosity and has excellent floating properties to the inner surface of the inner layer even if the inner surface temperature of the outer layer is lowered during pouring of the inner layer.

(Products to which the present invention can be applied) The present invention can be advantageously applied to a method for casting a two-layer hollow centrifugal roll in which the thickness of the inner and outer layers is uniform and the boundaries between the inner and outer layers are completely fused.

(Structure of the present invention) The present invention is 5i02+B2O3; 50-70c in %le%.
s (5in2) 20 at%, B2O5<
s o qb ), OaO+BaO+ 2・Na2O;
50-80% (However.

Na2O) 15%) 2-CaF2+ NaF;
This is a two-layer centrifugal casting flux having a composition of 50% or less and 2.0.

The melting point for 7 lux with the above component range is 650-900.
It has a low pour point of 700 to 1000 C, low melting point, low viscosity, and good flotation and wettability in molten metal, as well as good peelability from the metal after solidification.

The reasons for limiting the components of the flux of the present invention will be explained below. In the following explanation, all ``excellent'' means ``morchi''.

8i02+ B20. ; 50-70% (however, %5
102〉20 person, B2O3〈50 buns)...5102
is the most fundamentally necessary substance as a slag forming material (if it is less than 20%, the viscosity decreases suddenly just above the melting point of the flux), and the uniformity of the slag will be impaired. In addition, B20314 has a low melting point but high viscosity, so regardless of the low melting point, the '5050 range has a high viscosity and OB migration into the metal occurs, so it is desirable that it is lower than this.

Note that +9102 and 8205 represent acidic components in the slag, which have a strong network structure and are factors that increase viscosity. Therefore, 5102+B2O3
When the flux is over 70%, no matter how much low-viscosity fluoride such as Ca F 2 is mixed, the viscosity does not decrease, and when it is below 50%, the viscosity decreases too much, making it difficult to obtain a uniform flux distribution in centrifugal casting. It becomes difficult.

OaO+ 2・Na2O+Bad; 50~809&
(However, Na2O >' %)...When these compounds are turned into slag, ions are easily separated, and 5i02
It is a substance that facilitates uniform slag formation by disrupting the network structure of acidic components such as carbon dioxide, etc.), and has the ability to reduce free oxygen (such as free rII elements and ionized oxygen). These compounds contain metal element ions (Ca2+
Since it is proportional to the bonding force between oxygen and A (corresponding to Ha'Ic), Na20 has twice the effect for 1 mole of (ao).If Na2O is less than 15%, the network of acidic components will be disrupted. Even though it is effective, CaO alone cannot lower the melting point.On the other hand, CaO+2・Na2O+ Ba
If O is less than 50%, it will impair the stability of the slag.8
If the coefficient exceeds 0, the reducing property will be strong and the composition of the metal in contact will change, and the viscosity for centrifugal casting will be too low.

2.CaF2+ HaFe 50% or less...These fluorides can reduce the viscosity of slag regardless of whether it is acidic or basic, but if it exceeds 50%, the viscosity decrease is significant and it reacts with unstable 5102. Since fluoride vapor is likely to be generated, it is desirable to adjust the amount below this value.

In addition, MnO, A/20. Oxides of TiO2 and TiO2 have the effect of facilitating metallurgical wettability and vitrification, so they can be added in small amounts, or they tend to exist as impurities, but if they are present in large amounts, they will break down into basic components of sushi. It is appropriate that the total number is 1096 or less because it adversely affects the low melting point and low viscosity.

Furthermore, the flux that can be used for hollow two-layer centrifugal casting has a ratio of basic flux and fluoride, which reduce viscosity, to acidic flux, which increases viscosity, from 1.0 to 2.0.
The following is optimal. If it is less than 1.0, the viscosity will be too high and flux separation will not be good, and if it is more than 2.0, the viscosity of the molten flux will be too low and a uniform flux distribution will not be obtained.

(Example) This will be explained using the example shown in Table 1. Conventional product (a) and the present invention product (
As a result of casting a long two-layer centrifugally cast product (length more than 5 times the outer diameter) using bJ, conventional 7 sixes (a) resulted in poor welding on the side opposite to the inner layer casting, and poor welding near the casting side. A residual 7 lux and non-uniform outer layer thickness were observed at the boundary between the inner and outer layers near the center of the axis. However, with the flux of the present invention (bJ), a two-layer centrifugally cast product with a good welding state and uniform thickness of the inner and outer layers was obtained, and no residual flux was observed. Since it can be set to 100 ΩC and can be easily vitrified, the range of application of the inner surface temperature of the outer layer in centrifugal casting becomes wider, making it easier to set the timing of pouring the inner layer.

Claims (1)

[Claims] 5 in2 + B2O3 in morchi; 50 to 70 in (however,
5in2) 20 at %'B2O3< 5096
), CaO + 2・NaO; 50-80%
(However, Na2o > 15%) 2.CaF2+ N
aF: A double-layer centrifugal casting flux having a composition of 50% or less and 5102+8205 2.0.