JPS5855225B2 - Corrosion resistant alloy for molten zinc - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alloy having excellent corrosion resistance against molten zinc.

In the production line of galvanized steel sheets, corrosion-resistant materials for molten zinc used for zinc rolls, support rolls, roll frames, zinc baths, etc. that are immersed in or in contact with molten zinc have conventionally been made of high Cr-high Ni alloys or Very mild steel has been widely used, but in order to respond to various technical issues such as increasing the speed of the metal coating line, improving the quality of the surface of plated steel sheets, and extending the service life of equipment components,
There is a demand for the emergence of better corrosion-resistant materials.

For example, in the case of a conventional zinc roll made of a high Cr-high Ni alloy, it must be repaired after about 10 to 14 days of use due to corrosion caused by molten zinc and wear damage caused by contact with steel plates. Furthermore, in the case of conventional roll frames made of extremely mild steel, the reality is that they must be replaced after about 1 to 3 months of use.

In order to address these technical issues and problems, the present invention provides a new corrosion-resistant alloy for molten zinc that is particularly excellent in corrosion resistance against molten zinc, while also taking into consideration its properties such as wear resistance. Its characteristics are C:0.
4φ or less, Si: 2.5φ or less Mn: 1.5
% or less, Ni: 1.25-6.0%, Cr: 8
．． 0 to 14.0% by weight, with the remainder consisting of Fe and impurities; furthermore, Co: 4.0φ or less, Mo: 2.0% or less, Nb: 2.0% or less, (2) Each weight cake contains one or more types with a ratio of 0.5 or less.

Each component of the alloy of the present invention having the above chemical composition will be explained below.

C: 0.4% or less C combines with each element of Cr, Mo, Nb, and V to form a carbide, and the remainder is dissolved in the base material to strengthen it.

In this alloy, if C exceeds 0.4%, the susceptibility to casting becomes poor, so the upper limit is set to 0.4%.

Note that if the C content is small, the hardness will be low, and in order to obtain a high hardness, a desirable range is 0.2 to 0.4%.

Si: 2.5% or less, Mn: 1.5% or less Si increases hardness and improves wear resistance without having a negative effect on corrosion resistance, but if it exceeds 2.5%, it embrittles the substrate and Mn
Since these lower the corrosion resistance and also make the base material brittle, the upper limits are set at 2.5 and 1.5, respectively.

Note that both elements need to be contained to a certain extent in order to maintain castability.

Ni: 1.25 to 60Ni is an element that dissolves in solid solution in the base material and is effective in improving corrosion resistance, but if it is contained in a large amount, retained austenite increases and hardness decreases, and it is also economically undesirable. Therefore, the appropriate range for this alloy is 1.25 to 6.0%.

Cr: 8.0-14.0% Cr forms a solid solution in the base material, and some of it forms carbide, which has the effect of improving corrosion resistance and wear resistance.
If it is less than 8.0%, the intended effect cannot be obtained; on the other hand, 14.
If it exceeds 0.0, the corrosion resistance will be improved, but the wear resistance and toughness will tend to be lowered. Taking these effects into account, the appropriate range for this alloy is 8.0 to 14.0. shall be.

Co: 4.0% or less, Mo: 2.0% or less, Nb
: 2.0% or less, V: 0.5% or less Co is an element that has the same effect as Ni;
From the same point of view, the upper limit is set at 4.0.

M. Although Nb and Nb are elements that enhance the shape of carbides and improve corrosion resistance, the upper limit of each is set to 2.0 from a necessary and economic standpoint.

In addition, (2) is effective in improving hardness and refining crystal grains, and contributes to improving corrosion resistance, but if it exceeds 0.5%, it has the disadvantage of significantly lowering impact resistance. The upper limit is 5φ.

These additions of Co, Mo, Nb, and V are equivalent in improving corrosion resistance, and the present combined invention alloy selectively contains one or more of them to further enhance the effect. be.

The following examples of the alloy of the present invention will be described together with conventional examples and comparative materials.

Table 1 shows the chemical compositions of examples of the alloys of the present invention and other materials, and Table 2 shows the chemical compositions of each of these materials in molten zinc (45
Table 3 shows the results of the hardness test of the material.Table 3 shows the results of the hardness test of the material.

Looking at the table above, it can be seen that conventional materials Tsuta 8 to 10 have a corrosion loss of 5.0 to 15.7%, while the present invention alloy A
Nos. 1 to 7 showed 4.4% or less, which confirms that the corrosion resistance is particularly excellent.

In addition, while conventional materials cannot be hardened by heat treatment,
It has been found that the alloy of the present invention can be hardened by heat treatment, which allows it to maintain appropriate hardness and has excellent wear resistance.

Note that although the comparative materials AIO to 12 have a high content of Ni and Cr, they are inferior in corrosion resistance.

As described above, the alloy of the present invention has superior corrosion resistance compared to conventional materials known as corrosion-resistant materials for molten zinc, and when used in various molten zinc members as described above,
This is beneficial in terms of productivity and economy, as it can extend its service life, enable stable continuous operation of galvanized steel sheet manufacturing lines, and help improve the quality of the surface of galvanized steel sheets.

As mentioned above, the alloy of the present invention has quench hardenability, so in the case of zinc roll, for example,
By using the induction hardening method, it is possible to harden only the surface layer while retaining the internal toughness, and in this way, it is possible to improve the durability from the viewpoint of wear resistance.

Claims (1)

[Claims] IC: 0.4% or less, Si: 2.5% or less, Mn
: 1.5 or less, Ni: 1.25-6.0%, C
r: Contains 8.0 to 14.0% by weight, and the remainder is F.
A corrosion-resistant alloy for molten zinc, characterized by comprising e and impurities. 2 C: 0.4% or less, Si: 2.5% or less, Mn
: 1.5 or less, Ni: 1.25-6.0%, C
r: 8.0-14.0% and Co: 4.0
% or less, Mo: 2.0% or less, Nb: 2.0% or less, V: 0.5% or less, each by weight, and the remainder consists of Fe and impurities. Corrosion-resistant alloy for molten zinc.