JPS601393B2 - High temperature iodine gas corrosion resistant stainless steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention exhibits good corrosion resistance against high temperature iodine gas25
This relates to Cr-20Ni stainless steel.

Various energy sources are being considered in response to the worsening energy situation, and among these, hydrogen gas is attracting particular attention as a clean energy source. We are achieving certain results in each field.

However, as we encounter environments that we have never experienced before, new challenges are arising one after another in the field of materials.The purpose of the present invention is to provide a material that exhibits good corrosion resistance, especially in a hydrogen gas production environment. It is something to do. Among the means for producing hydrogen gas, a thermochemical method using a 12-Mg cycle can be expressed by the following chemical formula. (1st stage) (2nd stage) (3rd stage) (4th stage) When looking at the material balance by rearranging both the left and right sides of the reactions in the above four stages, it is expressed as Since there is theoretically no loss of Mg, it is attracting attention as an extremely economical method.

All of the above reactions proceed in a high-temperature atmosphere, but the second stage reaction in particular is a high-temperature thermal decomposition reaction of Mg(103)2, and moreover, 12 gases are generated in the atmosphere, something that has not been experienced in the past. No corrosive environment is formed. Therefore, we specifically selected the above second-stage reaction and began searching for a metal material that can be used satisfactorily even in such a corrosive environment. As the experimental conditions, a high temperature (600-700 qo) 12-02 mixed gas atmosphere was created, and various metal materials were exposed to this atmosphere to conduct corrosion experiments. It was found that the corrosion caused by the 02 gas and the high temperature oxidation caused by the 02 gas caused the corrosion to be quite severe. In addition, Co-based alloys and 50Ni-5
Although the eaves r-based alloys have shown good corrosion resistance, they are all extremely expensive, and the latter in particular has material problems such as poor hot workability and acid dissolution properties. Therefore, although it is slightly inferior in corrosion resistance, it is superior in terms of cost and other handling characteristics.
We took up the &r-2 side i-stainless steel and began investigating its alloy composition in order to improve its corrosion resistance. That is, the present invention provides corrosion resistance to high-temperature iodine gas without losing the characteristics of r-20Ni stainless steel, especially in the above-mentioned thermochemical method No. 2.
The reaction environment of the mounting layer used for the step reaction, that is, Mg(103)2
Various alloys were prototyped and researched with the aim of improving corrosion resistance in adverse environments such as the coexistence of high-temperature oxygen and repeated temperature changes. As a result, the above 2 and r-20N
An alloy containing 0.01 to 0.5% by weight of Y in I-series stainless steel exhibits corrosion resistance comparable to the above-mentioned Co-based alloys. 25Cr-20Ni stainless steel is an austenitic stainless steel given the symbol SUS31 in JIS, and generally has a CS of 0.0.
8% (weight%, same below), Si≦1.50%, MnS
2.00%, Pmi 0.040%, S≦0.030%, 1
9.00% SNiS 22.00%, 24.00% triCr
It is defined as 26.00%, and in the present invention, it is further 0.0%.
01-0.5% Y is blended.

If the blending amount of Y is less than 0.01%, the improvement in corrosion resistance is insufficient, and therefore it is not suitable for use as a reaction vessel for the second stage reaction. On the other hand, those containing more than 0.5% Y have the disadvantage that hot workability is significantly inhibited, making processing such as forging virtually impossible, and the economical burden becomes heavy. Table 1 shows the corrosion resistance and hot workability of 2Wr-20N stainless steels with various addition amounts of Y.
It is expressed as the average corrosion rate (side/year) during a continuous test of 65,000 x 9 hours in a mixed gas atmosphere [12:02 = 2:5 (molar ratio)].

Table 1 Sample No. Sample No. 1 had a high average corrosion rate because it did not contain Y, whereas sample No. 2 had a small amount of Y, so no improvement in corrosion resistance was observed.

On the other hand, sample No. Samples Nos. 3 to 7 contain a sufficient amount of Y, so the corrosion resistance improvement effect is remarkable, but sample Nos. The amount of Y compounded in No. 7 was slightly excessive, and a decrease in hot workability was observed. The figure shows the average corrosion rate when a thermal cycle of 65,000 x 8 hours of heat retention followed by 1 hour of furnace cooling was repeated 12 times, and the total heating time was 9 hours. In samples 9 and 10, the average corrosion rate was significantly lower than that of sample No. 8, which did not contain Y.

Table 2 Since the stainless steel of the present invention is constructed as described above, it is possible to significantly improve corrosion resistance without adversely affecting the properties of two-skinned R-20NJ stainless steel, such as hot workability and weldability. did it.

Claims (1)

[Claims] 1 C: 0.08% or less (weight %, same hereinafter) Si: 1
．． 50% or less Mn: 2.00% or less P: 0.040% or less S: 0.030% or less Ni: 19.00-22.00% Cr: 24.00-26.00% Y: 0.01- A high-temperature iodine gas corrosive stainless steel characterized by comprising 0.5% to Fe and inevitable impurities: the balance.