KR20010062109A - Steel sheet with sulfuric acid dew-point corrosion resistance excellent in workability and weldability - Google Patents

Abstract

PURPOSE: To provide a sulfuric acid dew point corrosion resistant steel sheet remarkably improved in workability, weld zone toughness and weld zone grinder maintainance and used for equipments using heavy oil as fuel, e.g. boilers of waste incineration equipments and electric power plants. CONSTITUTION: This sulfuric acid dew point corrosion resistant steel sheet contains, by mass, > 0.07% (desirably, > 0.0030%), > 1.0% Si, 0.2 to 1.5% Mn, > 0.03% P, > 0.03% S, > 0.6% Cu, 0.01 to 0.15% Sb, > 1.0% Ni, and the balance Fe with impurities.

Description

STEEL SHEET WITH SULFURIC ACID DEW-POINT CORROSION RESISTANCE EXCELLENT IN WORKABILITY AND WELDABILITY}

The present invention is an oil-resistant dew point corrosion resistant steel sheet used in a waste incineration facility, a boiler of a power plant facility, and the like with heavy oil as a fuel, and greatly improves workability, weld toughness, and weld polishing polishability. It is about a steel plate.

Heavy oil-based equipment such as waste incineration plants and boilers of power plant facilities are converted into sulfuric acid gas as the sulfur content contained in heavy oil is combusted, and the sulfuric acid gas is converted into SO ₃ by catalytic oxidation or direct compounding. It is combined with and becomes a legacy.

Corrosion that is a problem in boilers is known to be effective in the addition of Cu and Sb in the form described in Japanese Patent Application Laid-Open No. 43-14585, since the corrosion is severe at 40 to 50% of the lactic acid concentration. In the C content in the range of 0.08 to 0.15%, the yield point and strength of the material increases due to the addition of the alloy in order to obtain the oil acid dew point corrosion resistance, the stretching is not sufficient, the current high press There is a problem in advancing the shortening of the press forming process of the workpiece. Moreover, in the steel plate of C content of the conventional level, there exists a problem that the workability of the weld part is low, and since a weld part is easy to harden | cure, polishing polishability deteriorates.

The present invention is to obtain a steel sheet capable of processing complex shaped parts which cannot be obtained by the above-described conventional method and having good corrosion resistance, and thus changing from a conventional medium carbon component to a less than one, preferably ultra low carbon system. As a result, a material having greatly improved workability and weldability (welding property) was provided.

That is, the main subject matter of the present invention is described below.

(1) in mass%,

C ≤ 0.07%, Si ≤ 1.0%

Mn: 0.2-1.5%, P ≤ 0.03%

S ≤ 0.03% Cu ≤ 0.6%

Sb: 0.01 to 0.15% Ni ≤ 1.0%

The oil-resistant dew point corrosion-resistant steel plate containing these, The remainder consists of Fe and an impurity.

(2) in mass%,

C ≤ 0.0030%, Si ≤ 1.0%

Mn: 0.2-1.5%, P ≤ 0.03%

S ≤ 0.03% Cu ≤ 0.6%

Sb: 0.01 to 0.15% Ni ≤ 1.0%

The oil-resistant dew point corrosion-resistant steel plate containing these, The remainder consists of Fe and an impurity.

1 is a view showing the relationship between the amount of C, tensile strength, yield strength,

2 is a view showing the relationship between the amount of C and elongation,

3 is a view showing the results of lactic acid deposition test in the gas-liquid parallel state of the lactic acid-water system.

The invention is described in detail below.

In the present invention, high processability, good weldability acid resistance dew point corrosion resistance steel is excellent in acid resistance dew point corrosion resistance, and also excellent in workability to formability and weldability toughness in the processing of members related to waste incineration facilities, boilers of power plants, etc. It is a steel plate that greatly improves workability when greatly improving and cleaning welds.

As described above, the limiting requirement of the present invention is to soften the steel to reduce C, and to achieve high ductility due to low yield point and low strength. In the form shown in FIG. 1, FIG. 2, the effect of low C becomes remarkable, and the remarkable effect was acquired especially by making it extremely low at 0.0030% or less.

In addition, by reducing the C, the weld zone toughness and the hardening of the weld zone were reduced to obtain the dew point corrosion resistance of the welded portion, thereby obtaining the excellent weldability and the weld zone toughness and the low acid resistance dew point corrosion resistant steel.

This invention demonstrates the reason which limited the alloying element content to the said range.

C is an inexpensive element that obtains the required strength as a steel. Mass processing was limited to 0.07% or less in order to make processing required for waste incineration facilities, boilers of power plant equipment, etc. larger by the press working process than the conventional method. In order to obtain the said effect more remarkably, 0.0030% or less is most preferable. However, considering the decarburization ability in steelmaking, it is preferable to be 0.0005% or more.

Si increased the corrosion resistance, but adding more than 1.0% deteriorated the workability and made it 1.0% or less.

Mn has a deoxidation effect and at the same time increases the strength to improve the workability, the effect is insufficient at less than 0.2%, the lower limit was 0.2%, the upper limit was 1.5% by affecting the corrosion resistance.

P coexisted with Cu to increase weather resistance and improve strength, but the addition of a large amount was made 0.03% or less since it affects embrittlement and acid resistance.

Cu is an element that coexists with Sb to improve the dew point corrosion resistance of the acid. However, even when added at 0.6% or more, Cu does not improve the dew point corrosion resistance of the acid and deteriorates the hot workability.

The addition of Ni has the effect of improving the mechanical properties of the steel. The weather resistance was improved and the hot workability was improved. However, adding more than 1.0% became expensive and lowered the acidic dew point corrosion resistance to 1.0% or less.

Sb coexists with Cu and improves the acidic dew point corrosion resistance with the addition amount. However, when Sb is added in an amount of 0.15% or more, the effect becomes saturated and is defined as 0.01 to 0.15%.

Example 1

The effects of the present invention are shown in detail below based on the examples.

The continuous casting slab having the chemical composition (steels 1 to 7) of Table 1 was hot rolled to produce a steel plate having a sheet thickness of 4.5 mm to investigate workability, weldability and corrosion resistance. Workability measured yield strength, tensile strength, and elongation with the JIS No. 5 tensile test piece. In addition, the weld toughness made the welded portion according to the coated arc welding, and measured the hardness of the HAZ portion to determine the toughness and weldability (according to the grading degree). Corrosion resistance was determined by making corrosion test pieces after 600 emery polishing, immersing in 40% lactic acid at 60 ° C for 4 hours, and immersing in 20% hydrochloric acid at 30 ° C for 25 hours, and then measuring the corrosion resistance. The results are shown in Table 2.

In the form shown clearly in Table 2, in the ultra low carbon steel of the present invention, the yield point strength and tensile strength were low and the elongation was better than that of SS400.

In addition, in the ultra low carbon steel, the hardness value, which is an index of weld toughness and weldability, significantly decreased.

(mass %) Sample Ryo C Si Mn P S Cu Ni Sb Remarks 1234 0.08 0.74 0.87 0.011 0.006 0.32 0.20 0.130.10 0.04 0.48 0.009 0.008 0.58 0.21 0.120.12 0.56 0.54 0.022 0.011 0.15 0.18 0.120.21 0.03 0.80 0.012 0.015 0.03-- Comparative Example Comparative Example Comparative Example SS400 567 0.07 0.35 0.39 0.016 0.005 0.28 0.20 0.090.03 0.30 0.48 0.009 0.008 0.58 0.21 0.120.002 0.33 0.54 0.022 0.011 0.15 0.22 0.12 Invention invention invention invention invention invention invention

Sample Number Yield strength Tensile strength Elongation Weld hardness Corrosion loss * 1 Corrosion loss * 2 (N / mm ² ) (N / mm ² ) (%) (Hv) (mg / cm ² / hr) (mg / cm ² / hr) 1 * 2 * 3 * 4 * 317 437 36 236 12.1 12.8320 438 35 236 10.5 13.5321 438 37 236 11.2 12.2288 429 41 230 45.0 72.2 5 ** 6 ** 7 ** 295 395 41 210 10.1 11.1277 391 42 203 10.5 11.5 256 283 43 188 11.0 11.7

* 1: 6 hours of deposition in 40% H ₂ SO ₄ at 60 ° C

* 2: 25 hours of deposition in 20% H ₂ SO ₄ at 30 ° C

**: Inventive Example *: Comparative Example

Example 2

Comparison of SS400, SUS316, SUS304 and SUS430 shown in Table 3 of hot rolled steel sheets of Examples 5 to 7 shown in Table 3 and hot rolled continuous casting slabs made of steel plate having a sheet thickness of 4.5 mm and commercially available sheet thicknesses. As a result, corrosion test pieces were prepared after polishing the surface by 600 emery, and the amount of corrosion was measured by the deposition test in the lactic acid at each temperature and concentration from the relationship between the lactic acid temperature and the concentration calculated from the lactic-water-based gas-liquid parallel. . The results are shown in FIG.

In the form specified from Fig. 3, the effect of the material of the present invention was remarkable, and the corrosion resistance was good even in the most severe range of 40%, 60 ° C to 50%, and 80 ° C.

(mass %) Sample Ryo C Si Mn P S Cu Ni Cr Sb Remarks 567 0.07 0.35 0.39 0.016 0.005 0.28 0.20-0.130.03 0.30 0.48 0.009 0.008 0.58 0.21-0.120.002 0.33 0.54 0.022 0.011 0.15 0.22-0.12 Invention invention invention invention invention invention invention 891012 0.07 0.50 0.33 0.030 0.006 0.10 0.25 17.35 -0.06 0.50 1.71 0.030 0.011 0.11 9.80 18.20 -0.08 0.68 1.65 0.030 0.007 0.25 11.80 17.11 -0.08 0.01 0.35 0.010 0.011---- Invention invention invention invention invention invention invention

As described above, the steel of the present invention was excellent in the acid resistance dew point corrosion performance and processability, and greatly improved the formability and weldability in the processing of the members related to the waste incineration facility, the boiler of the power plant, etc. It can be greatly improved, and it is possible to greatly reduce the manufacturing cost based on the simplified manufacturing process of the manufacturing equipment and the improved workability of the welded parts.

Claims (2)

By mass%, C ≤ 0.07%, Si ≤ 1.0% Mn: 0.2-1.5%, P ≤ 0.03% S ≤ 0.03% Cu ≤ 0.6% Sb: 0.01 to 0.15% Ni ≤ 1.0% The oil-resistant dew point corrosion-resistant steel plate containing these, The remainder consists of Fe and an impurity. By mass%, C ≤ 0.0030%, Si ≤ 1.0% Mn: 0.2-1.5%, P ≤ 0.03% S ≤ 0.03% Cu ≤ 0.6% Sb: 0.01 to 0.15% Ni ≤ 1.0% The oil-resistant dew point corrosion-resistant steel plate containing these, The remainder consists of Fe and an impurity.