JPS6349357A - Centrifugal casting tube having two layers and casting method thereof - Google Patents

Abstract

PURPOSE:To improve the wear resistance and seizure resistance for inner face of a tube by casting an inner layer material, such as high P-B cast iron, etc., by centrifugal casting method at the time of equalizing an inner face temp. of outer layer made of cast iron or cast steel, which has been cast by the centrifugal casting method, almost to be casting temp. for the inner layer. CONSTITUTION:The outer layer (a) uses the cast steel or the toughness cast iron and the inner layer (b) uses the cast iron having by wt% of 2.5-3.5% C, 1.0-2.5% Si, 0.5-1.0% Mn, 0.2-0.9% P, <=0.1% S, 0.02-0.1% B. The casting temp. of the molten metal for the inner layer is desirable to be higher by 50-150 deg.C then its solidified temp. at the time when the inner face temp. of outer layer drops down to the same temp. As the casting temp. for the inner layer. In this way, the product having excellent quality on the inner face is produced.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a two-layer cast pipe and a method for manufacturing the same, and is particularly applicable to pipes such as cylinder lychee, etc., which require wear resistance and seizure resistance on the inner surface and have toughness. This invention relates to a two-layer cast pipe such as a slurry transport pipe and its manufacturing method.

[Conventional technology]

Conventional pipes that meet the above requirements are made of a single-layer material, and wear resistance is imparted by carbonization, quench hardening, etc.

However, when the pipe mouth body is exposed to friction or a high temperature range (up to 400° C.), the quench hardening effect is lost, and carbide crystallization causes the material itself to have low toughness. Medium carbon steel and low alloy steel are used for internal hardening systems, and alloy cast iron is used for carbide crystallization systems.

[Problem that the invention seeks to solve]

As mentioned above, crystallizing carbide itself is effective in imparting wear resistance, but it has the disadvantages of lower toughness and lower heat resistance.

On the other hand, the internal quench hardening method has disadvantages in that it is not effective in terms of wear resistance at high temperatures and increases manufacturing costs.

Furthermore, the above-mentioned painting method had a drawback in terms of seizure resistance.

In addition, in the conventional two-layer centrifugal casting method in which the outer layer is made of low carbon steel and the inner layer is made of cast iron (i.e., the method in which the inner layer molten metal is poured at the beginning of solidification after the outer layer molten metal is poured), significant carbon diffusion occurs. It was said that it was impossible to create a two-layer pipe with the original characteristic of having two layers inside and outside.

[Means for solving problems]

The present invention has been proposed to solve the above problems, and an object of the present invention is to provide a two-layer pipe having toughness, wear resistance, and seizure resistance.

In order to provide the tube with toughness, tough cast iron or cast steel is used for the outer layer, and high P-B cast iron, which has excellent wear resistance and seizure resistance rather than toughness, is used for the inner layer, thereby reducing carbon as much as possible. The solution is to suppress diffusion and manufacture using two-layer centrifugal casting.

That is, the present invention provides: (1) After casting an outer layer made of strong cast iron or cast steel by centrifugal casting, when the inner surface temperature of the outer layer becomes almost the same as the casting temperature of the inner layer, the inner layer is cast by centrifugal casting. and (2) an outer layer made of tough cast iron or cast steel, the outer layer of which is cast by the centrifugal casting method, and a heavy metal part C:2. 5-55
, Si:1. O~2.5, Mn:Q, 5~1.0, P:
[12-0.9, S:Q, 1 or less, B:Q, 02-α1
This is a two-layer centrifugally cast pipe characterized by comprising an outer layer made of high P-B cast iron and an inner layer cast by a centrifugal casting method.

[Effect]

Toughness is determined by the material of the outer layer, and wear resistance and seizure resistance are determined by the material of the inner layer.The inner layer and outer layer are metallurgically joined, and the two-layer centrifugal casting method aims to create a multilayer effect that combines the advantages of both. The inner surface temperature of the outer layer (after hardening) and the molten metal casting temperature of the inner layer are made the same, with the aim of minimizing carbon diffusion and preventing cracking.

In addition, the inner layer is made of a specific P-B cast iron to suppress carbon diffusion as much as possible.

〔Example〕

FIG. 1 is a sectional view showing the structure of the bibrow tube of the present invention, in which the outer layer (a) is made of cast tA (or tough cast iron), and the inner layer (
b) is made of high P-B cast iron.

As an example, Table 1 shows the chemical composition and mechanical properties.

The casting conditions for the actual row are as follows.

(1) Casting dimensions near 00φX4500t (2) Casting method: After the outer layer solidifies, the inner layer molten metal casting temperature is the same as the outer layer inner surface preparation.

(1,150 to 1,250℃) (3) Core rotation speed: 90G with GNO (4, I casting thickness: outer layer 605m, inner layer 30cm (5) Material and melting point: outer layer @ (1,430℃) ), inner layer height P-B
Cast iron (1,100°C) (6) Heat treatment: 550°C x 3 hours By the above method, strength and wear resistance as a pipe could be imparted. The reasons for limiting the composition of the inner layer material and the range of the inner layer molten metal casting temperature are as follows.

0:2.5~&5 Excellent C needs to be balanced with B and P in order to set the crystallization ffi of steadite type carbide and flaky graphite. 02
．． If it is less than C55, the amount of flaky graphite will be small and the lubricity will be poor, and if it exceeds C55, the amount of steadite carbide and flaky graphite will be large and the cracking resistance will be reduced.

81: 1.0-2.5% Sl is necessary to crystallize flake graphite in addition to steadite-type carbide, and 1. If it is less than 0%, the effect is small;
If it exceeds 2.54i, it will have an adverse effect on the formation of steadite-type carbides.

Mn; α5 to 1.0 To suppress the damage caused by S, KMn must have a coefficient of α5 or more, and if it exceeds 1.0%, toughness decreases.

P: Q, 2 to 1lL9% Necessary for forming steadite type carbides; less than 12% has little effect; (more than 19%, the amount of carbides is 1%)
It exceeds 0 scratch and has poor cracking resistance.

S: (11% or less It is necessary to suppress the value to 1111 or less because it unnecessarily embrittles the material.

B; 0. a2~α1 壬B is an element necessary to form a steadite type carbide, and the effect is small below a02%02%, (119
If it exceeds 1, the material will deteriorate.

Regarding the inner layer molten metal casting temperature, if the inner layer temperature of the outer layer is higher than the solidification temperature of the inner layer molten metal but less than 50°C, problems will occur in the fluidity of molten metal pouring, and if the inner layer temperature of the outer layer is 150°C lower than the solidification temperature of the inner layer molten metal.
When the temperature rises, carbon diffusion increases, resulting in lower toughness of the outer layer and lower carbon content of the inner layer. Therefore, the inner layer molten metal casting temperature V is such that the inner surface temperature of the outer layer is 5 to 150 degrees higher than the solidification temperature of the inner layer molten metal.
It is necessary to have a high temperature.

〔Effect of the invention〕

As mentioned above, is it a combination of low carbon and high carbon? By using the centrifugal casting method proposed this time, cast iron or cast steel with toughness is used for the outer layer, and high P-B cast iron with wear resistance and seizure resistance is used for the inner layer. The layered structure improves the wear resistance and seizure resistance of the inner surface of the tube, and also improves the toughness of the entire tube.

Brief Explanation of the East Plane FIG. 1 is a cross-sectional view showing the structure of a two-layer tube (vibrator, tube) according to the present invention.

Sub-agent: 1) Akira Sub-agent Ryo Hagi Hara - Sub-agent Atsuo Yasunishi

Claims (2)

[Claims] (1) After casting the outer layer made of strong cast iron or cast steel using the centrifugal casting method, when the inner surface temperature of the outer layer becomes almost the same as the casting temperature of the inner layer, the inner layer is cast using the centrifugal casting method. A centrifugal casting method for two-layer tubes characterized by: (2) The outer layer is made of strong cast iron or cast steel, and the outer layer is cast by centrifugal casting, and the weight percentage is C; 2.5 to 3.
5, Si; 1.0-2.5, Mn; 0.5-1.0, P
; 0.2-0.9, S; 0.1 or less, B; 0.02-0
．． A two-layer centrifugally cast pipe characterized by comprising an inner layer made of high P-B cast iron of No. 14 and an inner layer cast by a centrifugal casting method inside the outer layer.