JPS5915973B2 - High Si ferrite steel for petroleum and coal chemical plants - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ferritic steel used in petrochemical plants, coal liquefaction plants, etc., which exhibits resistance to particularly severe corrosive and erosional conditions.

Conventionally, as steel materials used in petrochemical plants and the like, austenitic stainless steel is used for high temperature applications (400°C or higher), and chrome steel (9Cr.IMo) is used for medium temperature applications (250 to 400°C).

However, coal liquefaction plant reactors, etc., which have recently been in the spotlight, are used to liquefy coal under high pressure of hydrogen gas. It is required to have high corrosion resistance in an atmosphere containing water, and it is also necessary to withstand erosion caused by coal particles or ash contained in the reaction liquid.

Under such severe conditions, conventionally used austenitic stainless steel or chromium steel are insufficient. Therefore, unlike petrochemical plants, steel is required that has corrosion resistance, erosion resistance, and erosion/corrosion resistance that can withstand more complex and harsh environments. The object of the present invention is to provide a steel that exhibits sufficient performance to withstand even such severe conditions.

This invention steel has: (1) Co, 15% or less, 5i2.0-6.0%, Mn
A high-Si ferrite steel with excellent corrosion resistance and erosion resistance, consisting of 29Oφ or less, 2.0 to 30.0% Cr, and the balance iron and impurities.

(2) In addition, Ni, V, W, Ti, Nb, Ta are added to the above steel.
A ferritic steel having excellent corrosion resistance and erosion resistance, containing one or more of Zr in a total amount of 380% or less.

It is.

The characteristics of this invented steel are that it is made of ferritic steel to prevent stress corrosion cracking, which is a weak point of conventional austenitic stainless steel, and that it contains a relatively large amount of Si compared to conventional chromium steel, and has a Cr-based protective coating. (chromium oxide, chromium sulfide) and also generates a SiO2 protective film to improve sulfide corrosion resistance and improve resistance to erosion corrosion caused by solid particles, as well as hydrogen attack at high temperatures. It is characterized by being designed to withstand even the most severe conditions.

Describe the range of each component.

C is an important component to increase the strength of steel, but 0.1
If it exceeds 5%, susceptibility to intergranular corrosion increases and corrosion resistance deteriorates.
Since it also deteriorates workability, the content was set at 0.15% or less.

Si is one of the characteristics of the steel of the present invention, and as mentioned earlier, it has the effect of stabilizing the formation of a Cr-based protective film, and Si itself forms an SiO2-based protective film below the Cr-based protective film. It also has effects.

Such an effect requires addition of 2.0% or more, but 6
．． If it exceeds 0%, workability and weldability will deteriorate.2
, θ~6.0. -Mn is added as a deoxidizing agent, but if it exceeds 2.0%, rough workability deteriorates, so it is regulated to 2.0% or less. Cr has the effect of improving sulfide corrosion resistance, and from this point of view, the more it is, the more effective it is.

However, if ξ exceeds 30.0%, the workability deteriorates, so the upper limit is set to 30.0%. The lower limit is 1 for conventional chrome steel.
Although it is necessary to add about 0% or more, the steel of the present invention exhibits the effect if it is 2.0% or more due to the synergistic effect of the addition of St, as described above, so it is 2.0 to 30.0%. And so.
With the following composition range, it has sufficient performance as a steel material exposed to harsh conditions such as coal liquefaction equipment, but it also requires high erosion resistance and hydrogen attack resistance at high pressure. If Ni and VtWtTitNbt
One or more types of TatZr are added in a total amount of 3.0 or less.

Ni is particularly effective in improving erosion resistance.

However, if the ratio exceeds 3.0, the effect becomes weak. Also V, W
, Ti, Nb, and TatZr are all carbide-stabilizing elements that combine with C in steel to improve the workability of the steel and have the effect of exhibiting high resistance to hydrogen attack under high-pressure hydrogen. Furthermore, it also has the effect of improving erosion resistance. A similar effect can be obtained by adding one type of each element or a combination of two or more types, but if the total amount exceeds 3.0 inches, workability deteriorates, so it should be regulated to 3.0 inches or less. EXAMPLES The 25 types of steel shown in Table 1 were cut into plate-shaped test pieces and subjected to corrosion tests and two-losion corrosion tests under the conditions shown in Table 2. The results are shown in Table 3.

In each table, A1-4 steel is usually commercially available steel 5-25.
All steels were manufactured by vacuum melting, hot-melted and hot-rolled into steel plates, and then heat treated.
A5-9 steels are comparative steels, and AIO-25 steels are inventive steels. As shown in Table 3, the first and second conditions of the corrosion test
The steel of the present invention exhibits significantly higher performance than commercially available steel and comparative steel both under these conditions and in the erosion test.

Claims (1)

[Claims] 1 C0.15% or less, Si2.0-6.0%, Mn2
．． High S with excellent corrosion resistance and erosion resistance, consisting of 0% or less, Cr2.0-30.0%, balance iron and impurities.
i-ferritic steel. 2 C0.15% or less, Si2.0-6.0%, Mn2
．． 0% or less, Cr2.0-30.0%, and further N
A high-Si ferritic steel containing one or more of i, V, W, Ti, Nb, Ta, and Zr in a total of 3.0% or less, with the balance being iron and impurities, and having excellent corrosion resistance and erosion resistance.