JPH1068019A - Production of steel sheet for crude oil tanker excellent in fatigue crack progressing characteristics in wet hydrogen slufide environment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a steel sheet having characteristics that fatigue cracks are hard to progress in the case of being used in a wet hydrogen sulfide environment in a crude oil tanker. SOLUTION: In a continuously cast slab or ingot having a compsn. contg., by weight, 0.01 to 0.2% C, 0.2 to 0.6% Si, 0.3 to 2.0% Mn, 0.01 to 0.1% sol.Al, >0.003 to 0.020% S, and the balance Fe with inevitable impurities, hot forging or hot rolling is finished in the temp. range of (the Ar3 point-30 deg.C) or above, without reheating, it is subjected to accelerated cooling from the temp. of (the Ar3 point-30 deg.C) or above to the temp. range of 400 to 600 deg.C at a cooling rate of 5 to 25 deg.C/s and is thereafter subjected to air cooling or slow cooling. The slab may contain one or more kinds of elements selected from either or both of the following elemental groups: the primary group: Nb, Ti and V respectively by 0.01 to 0.1% and the secondary group: 0.1 to 1.0% Cu and 0.1 to 2.0% Cr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a steel sheet having excellent fatigue crack growth characteristics in a wet hydrogen sulfide environment suitable as a steel sheet for a crude oil tanker containing hydrogen sulfide.

[0002]

2. Description of the Related Art Hydrogen-induced cracking (HIC) or sulfide stress cracking (SSC) in steel used in a wet hydrogen sulfide environment
It is already well known that this is a problem, and a number of studies have been made on its prevention, and a number of measures have been proposed.

[0003] HIC is a crack that occurs in steel without external stress, and SSC is a crack under static stress. HIC
And SSC are hydrogen embrittlement caused by the penetration of hydrogen generated when steel corrodes in a wet hydrogen sulfide environment into steel, and is one of the embrittlement phenomena of steel.

[0004] In order to suppress the above-mentioned HIC and SSC, it is said that it is effective to make the S extremely low and to perform Ca treatment. However, the extremely low S and the Ca treatment increase the refining cost, and the Ca treatment often has an adverse effect on the suppression of the growth of fatigue cracks described below.

[0005] On the other hand, fatigue fracture and corrosion fatigue fracture that occur under the condition of repeated stress are another major embrittlement phenomenon of steel. Ships or marine structures that are subject to repeated stress from waves, automobile wheels and crankshafts,
Further, there have been many studies on fatigue and corrosion fatigue of gear materials and the like.

Recently, high-strength steel has been widely used in crude oil tankers and the like from the viewpoint of increasing the size and cost. In such a case, a higher stress is applied to the steel material, and the problem of fatigue, and furthermore, fatigue in a wet hydrogen sulfide environment has become a concern. However, there is no example of investigating the fatigue behavior of a steel plate for a crude oil tanker exposed to a wet hydrogen sulfide environment as described above due to waves, and of course, there is no example of studying material factors.

Corrosion NACE, vol. 32, No. 12 (Decemb
er, 1976) by O.VOSHIKOVSKI on `` Fatigue Crack Gr
owth in an X65 Line-Pipe Steel in Sour Crude Oil ''
The report entitled "The higher the concentration of hydrogen sulfide, the faster the rate of fatigue crack growth accelerated.
The environmental effects on fatigue in a wet hydrogen sulfide environment are considered to be issues that cannot be ignored. The content of the above document is limited to fatigue in a wet hydrogen sulfide environment for line pipe steel. It is considered that the acceleration of the crack growth rate presumed to be caused by hydrogen sulfide is superimposed on hydrogen embrittlement. However, there are few examples of detailed studies on the material factors affecting fatigue in a wet hydrogen sulfide environment, and no specific countermeasures have been found.

FIG. 1 shows the results of a fatigue test of a conventional steel tested in Examples described later in the atmosphere and in a wet hydrogen sulfide environment. Da / dN on the vertical axis is a crack growth rate, which is expressed as a growth distance (mm) per one stress cycle.
ΔK on the horizontal axis is the difference between the maximum stress intensity factor (Kmax) and the minimum stress intensity factor (Kmin). That is, ΔK = Kmax−Kmin
It is. In general, the abscissa represents ΔK on the crack growth rate (da / dN) because the relationship of da / dN = C (ΔK) m is widely recognized between ΔK and ΔK. The stress intensity factor is defined as the size of a crack when a crack (defect or crack) exists.
It is treated as stress in fracture mechanics, which standardizes mechanical boundary conditions such as shape, dimensions and shape of materials, and load conditions. It is also useful in standardizing and handling fatigue cracks in corrosion fatigue phenomena.

As apparent from FIG. 1, the crack growth rate is higher in a wet hydrogen sulfide environment than in the atmosphere. In particular, ΔK
The crack growth is accelerated in the region with large (approximately 20 ksi (in) 1/2 or more).

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to cope with fatigue fracture in a wet hydrogen sulfide environment, which is expected to frequently occur with increasing tensile strength of a steel material.

A specific object of the present invention is to provide a YS (yield stress) used for crude oil tankers without increasing refining costs.
) 20-45kgf / mm2, TS (tensile strength) 35-60kgf / mm2 grade steel material that has the property that fatigue cracks do not easily propagate when used in a wet hydrogen sulfide environment. To provide. More specifically, the use of conventional ordinary steel or high-strength steel does not cause HIC or SSC, but the use of conventional high-strength steel is resistant to wet hydrogen sulfide environments where the fatigue crack growth rate is accelerated. Another object of the present invention is to provide a method for manufacturing a steel sheet having excellent fatigue crack growth characteristics.

[0012]

The gist of the present invention resides in the following manufacturing method.

(1) By weight%, C: 0.01-0.2%, Si: 0.2
~ 0.6%, Mn: 0.3 ~ 2.0%, sol.Al:0.01~0.1%, balance is S: more than 0.003% and less than 0.020% and continuous casting slab or ingot made of Fe and unavoidable impurities and hot forged or hot Cold rolling is completed in the temperature range of (Ar3 point -30 ° C) or higher, and the temperature range of (Ar3 point -30 ° C) or higher and the cooling range of 5 to 25 ° C / s in the temperature range of 400 to 600 ° C without reheating. A method for producing a steel plate for a crude oil tanker having excellent fatigue crack growth characteristics in a wet hydrogen sulfide environment, wherein the steel plate is accelerated and cooled and then cooled or slowly cooled.

(2) In addition to the alloy components described in (1) above, one or more of Nb: 0.01-0.1%, Ti: 0.01-0.1% and V: 0.01-0.1% by weight. The remaining balance is S: more than 0.003% and less than 0.020%, and a continuous cast slab or ingot composed of unavoidable impurities and Fe is treated in the same process as in (1), and is excellent in fatigue crack growth characteristics in a wet hydrogen sulfide environment. Manufacturing method.

(3) In addition to the alloy components described in the above (1), one or more of Cu: 0.1-1.0% and Cr: 0.1-2.0% by weight are further contained, and the balance is S: A method for producing a steel plate for a crude oil tanker having excellent fatigue crack growth characteristics in a wet hydrogen sulfide environment in which a continuous cast slab or ingot comprising Fe and 0.0020% or less and unavoidable impurities and Fe is treated in the same process as (1).

(4) In addition to the alloy components described in (1) above, one or two types of Cu: 0.1-1.0% and Cr: 0.1-2.0% by weight, and Nb: 0.01-0.1%. %, Ti: 0.01-0.1
% And V: one or more of 0.01 to 0.1%, and the balance is S: more than 0.003% and not more than 0.020% and unavoidable impurities.
A method for producing a steel plate for a crude oil tanker having excellent fatigue crack growth characteristics in a wet hydrogen sulfide environment in which a continuously cast slab or ingot made of Fe is treated in the same process as in (1).

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made based on the results of a study on material factors affecting the fatigue behavior in a wet hydrogen sulfide environment, which has hardly been studied hitherto.

As will be clarified in the examples below, when the fatigue behavior in a wet hydrogen sulfide environment is observed, crack growth is remarkably accelerated under a stress state where ΔK is large, that is, the plastic deformation region is widened. In fatigue in a wet hydrogen sulfide environment, the crack growth increases as the hydrogen sulfide concentration increases. It is considered that the higher the concentration of hydrogen sulfide, the greater the amount of hydrogen atoms generated due to corrosion that enter the steel and form a solid solution. Further, since crack growth is accelerated in a stress state in which the plastic deformation region is widened, it is presumed that hydrogen embrittlement is greatly involved in this fatigue fracture behavior.

Further, noting that the fatigue fracture mainly propagates in the ferrite grains and that the crack growth rate is large in a region where the plastic deformation is large, the plastic deformation behavior of the ferrite grains is closely related to the fatigue fracture behavior. it seems to do.

According to the present invention, by appropriately selecting the chemical composition of steel and the manufacturing conditions, it is possible to increase the strength of ferrite grains themselves or to form a mixed structure of fine ferrite and fine bainite (prevention of formation of block-like bainite and martensite). ) Based on the mechanism of suppressing the fatigue crack growth rate. That is, based on the new finding that in the above metal structure, plastic deformation received by ferrite grains under repeated stress can be reduced as compared with conventional steel, and the growth rate of fatigue crack can be reduced. Things.

In terms of chemical composition, Nb, Ti and V
By adding one or more of the above, the ferrite crystal grains can be refined, and thus the bainite can be refined, and the ferrite itself can be strengthened by the formation of carbides, and the crack growth rate can be further reduced. .
In addition, the addition of one or both of Cu and Cr improves the corrosion resistance of the steel in an atmosphere containing hydrogen sulfide, reduces the corrosion rate, and consequently reduces the amount of solute hydrogen in the steel to increase the crack growth rate. Can be smaller.

Hereinafter, the reasons for selecting the chemical composition of the steel used as the material of the production method of the present invention and the reasons for selecting the production conditions will be described in detail.

1) Chemical composition of steel C is a component that increases the strength of steel. In the present invention, in order to maintain the above-mentioned strength level, the content of C is set to 0.01% or more (hereinafter,% relating to the alloy component means wt%). If less than this, the steel produced by the method of the present invention (hereinafter, referred to as
It is difficult to secure the strength of the steel necessary for the use of the steel of the present invention for convenience). On the other hand, in order to maintain good weldability of steel, the upper limit of the C content is set to 0.2%. The crude oil tanker targeted by the steel of the present invention undergoes welding. When the C content exceeds 0.2%, so-called weld cracking is liable to occur, that is, cracks occur a short time after welding in the hardened portion of the weld heat-affected zone due to hydrogen dissolved in the steel during welding. Welding cracks are greatly affected by the hardness of the heat affected zone, and the harder they are, the more likely they are to crack. Since a material having a higher C is easily cured, a lower C is better to prevent this. Desirable C content is 0.
03-0.18%.

[0024] Si is useful as a deoxidizing agent for steel, and is also actively used in the present invention for improving fatigue crack growth characteristics in a wet hydrogen sulfide environment. 0.2% Si content
Below, these effects cannot be expected. On the other hand, Si
If it exceeds 0.6%, the toughness of the steel is impaired. The desirable content of Si is 0.25 to 0.5%.

Mn is also a component that improves the strength of steel.
If it is less than 0.3%, it is difficult to secure the strength required for the intended use of the steel of the present invention. However, like Mn, Mn is a component that hardens the heat affected zone and induces welding cracks.
Its content has an upper limit. That is, if it exceeds 2.0%, welding cracks are likely to occur. Desirable Mn content is 0.5
~ 1.8%.

Al is used for deoxidizing steel, and must be added so that the content of sol.Al is 0.01%. However, if the sol.Al content exceeds 0.1%, the cleanliness and toughness of the steel are impaired. Desirable sol.Al
The content range is 0.01-0.05%.

One of the steels used as the raw material of the method of the present invention comprises the above components and the balance consisting of Fe and inevitable impurities. Of the impurities, P and S are 0.025% or less, respectively.
It is desirable to keep it below 020%.

However, it is not necessary to reduce S to 0.003% or less at the expense of refining costs. S for crude oil tankers
This is because HIC and SSC do not occur even if the content is not kept below 0.003%. This is clear from the fact that HIC and SSC were not generated at all even when ordinary steel or high-tensile steel was used for crude oil tankers. Therefore, it is not necessary to include Ca for controlling the shape of the sulfide. That is, it is not necessary to use an expensive steel plate taking measures against HIC resistance or SSC resistance in a portion where the steel plate manufactured by the method of the present invention is used. When the Ca treatment is performed, a coarse compound compound of Ca sulfide and oxide is generated depending on the treatment condition, and the fatigue strength may be lowered instead. On the other hand, S is 0.
If it exceeds 020%, lamella cracking will occur during welding, so the content should be 0.020% or less.

The steel used as the material of the method of the present invention may further contain one or more of the following two elements in addition to the above components.

First group: 0.01 to 0.1% of Nb, Ti and V respectively Second group: 0.1 to 1.0% of Cu and 0.1 to 2.0% of Cr The first group elements are fine ferrite grains. It has the effect of improving the crack growth properties by graining and thus the refinement of bainite and its strengthening.

If any of Nb, Ti, and V is less than 0.01%, the effect of improving the fatigue crack growth characteristics in a wet hydrogen sulfide environment is poor. On the other hand, if the content of each exceeds 0.1%, not only the effect is saturated, but also the strength of the steel is excessively increased and the toughness is impaired. In each case, the desirable content is 0.02 to 0.05%.

The elements of the second group improve the corrosion resistance of the steel as described above. However, if Cu is less than 0.1%, the effect of addition is small. On the other hand, Cu induces welding cracks and also melts at high temperatures, lowering the grain boundary strength of the steel and making cracks and scratches more likely to occur during hot rolling.
Should be up to%. Desirable Cu content is 0.
2 to 0.5%.

[0033] Cr at a content of 0.1% or more is effective for further improving the fatigue crack growth characteristics in a wet hydrogen sulfide environment.
However, like Cr and Mn, Cr is a component that hardens the weld heat affected zone and causes weld cracking. Therefore, when Cr is added, the upper limit of the content should be 2.0%. The desirable content of Cr is 0.5-1.5%.

One or more elements can be selected from one or both of the first and second groups and added.

2) Manufacturing Method Steel having the above-mentioned chemical composition is prepared by ordinary smelting and casting (continuous casting or ingot casting), followed by hot forging or hot rolling (hereinafter collectively referred to as hot working). Being a board product.

There is no particular limitation on the heating temperature when hot working a continuously cast slab or ingot. What is necessary is just to heat to the temperature range in which the next hot working and accelerated cooling are possible.

What is important is the cooling condition after hot working.
This cooling must be accelerated cooling from a temperature of (Ar3 point-30 ° C) or higher. If the cooling start temperature is lower than (Ar3-30 ° C), a large amount of coarse pro-eutectoid ferrite is formed, and the ferrite is not strengthened even by accelerated cooling and has no effect of improving the fatigue crack growth characteristics, but also has a block-like shape. The formation of bainite and martensite is accelerated rather than accelerated. A desirable cooling start temperature is a temperature not lower than the Ar3 point.

The cooling rate is in the range from 5 ° C./s to 25 ° C./s. At a cooling rate lower than 5 ° C./s, there is no effect of accelerated cooling, and there is no effect of improving fatigue crack growth characteristics in a wet hydrogen sulfide environment, which is the object of the present invention. On the other hand, if the cooling rate exceeds 25 ° C./s, not only does the strength of the steel become too high, but also the above-mentioned block-like bainite and martensite are formed and the crack growth is accelerated.

The stop temperature of the above-mentioned accelerated cooling is 400 to 600
A range of ° C is appropriate. At temperatures below 400 ° C, the steel becomes too strong, just as if the cooling rate was too high.
The formation of block-like bainite and martensite accelerates crack growth. If the stop temperature of accelerated cooling exceeds 600 ° C., ferrite and bainite are not miniaturized, and ferrite is not strengthened and the effect of accelerated cooling is poor. After the completion of the accelerated cooling, cooling or slow cooling is performed.
The steel material (product) thus obtained can be used as it is.

[0040]

The present invention will be described below with reference to examples.

Table 1 shows the chemical composition of the test steel. These steels were melted and continuously cast into 240 mm thick slabs, which were heated to 1150 ° C and rolled into 15 mm thick plates. Tables 2 to 4 show the finishing temperatures. Next, cooling was performed from the accelerated cooling start temperature also shown in Tables 2 to 4. Tables 2 to 4 also show the cooling rate and accelerated cooling stop temperature.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

From the steel sheet obtained as described above, FIG.
A test piece shown in (b) was collected and subjected to a fatigue test in a wet hydrogen sulfide environment using the apparatus shown in FIG. That is, in FIG.
As shown in (a), the test piece 1 was repeatedly subjected to stress by the hydraulic cylinder 5 in the test solution tank 2. 3 is a solution circulation pump, 4 is a load cell, 6 is a hydraulic pressure source, 7 is a servo valve, 8 is a waveform generator, and 9 is a load controller. The fatigue test conditions are as follows.

F (repetition rate) = 30 Hz R (stress ratio) = 0.1 T (test temperature) = room temperature Tables 2 to 4 show that ΔK = 20 ksi (i) in a wet hydrogen sulfide environment.
n) 1/2 crack growth rate (da / dN) and its value and the crack growth rate at ΔK = 20 ksi (in) 1/2 in the atmosphere (da
/ dN). Note that the crack growth rate is ΔK = 2
The reason why the value at the time of 0 ksi (in) 1/2 was adopted is that, as shown in FIG. 1 described below, the crack growth rate in this region is significantly different from that in the atmosphere. Wet hydrogen sulphide environment is obtained by adding hydrogen sulfide concentration of 1 vo
A mixture of l.% (the rest is nitrogen) is constantly blown during the test.

FIG. 1 shows a comparison of the crack growth rate of the conventional steel (test number A-1 in Table 2) in the atmosphere and in a wet hydrogen sulfide environment. As is clear from FIG. 1, the crack growth rate is higher in a wet hydrogen sulfide environment than in the atmosphere. In particular, ΔK
Crack growth in a wet hydrogen sulfide environment is accelerated in a large region (more than about 20 ksi (in) 1/2).

FIG. 2 shows a conventional example (test number A-
The result of investigating the effect of the concentration of hydrogen dissolved in the steel on the fatigue crack growth rate using the steel of 1) is shown. In this experiment, the concentration of dissolved hydrogen was changed using a mixed gas having a hydrogen sulfide concentration of 1 vol.% And 10 vol.% And a pure hydrogen sulfide gas. The higher the concentration of hydrogen sulfide, the higher the concentration of hydrogen dissolved in steel. Therefore, as is clear from FIG. 2, the higher the concentration of hydrogen sulfide, that is, the higher the concentration of solid solution hydrogen, the higher the crack growth rate.

FIG. 3 shows the effect of the accelerated cooling stop temperature on the ratio of the crack growth rate of test samples E-1 to F-6 in a wet hydrogen sulfide environment to that in the atmosphere. At a temperature in the range of 600 to 400 ° C, the crack growth rate is suppressed to within three times that of the atmosphere.

Test numbers A-1, B-1, C-1 in Table 2
And D-1 are examples in which a steel to which neither the first group element nor the second group element was added was used as a raw material, and no accelerated cooling was performed. The crack growth rate in the wet hydrogen sulfide environment of the steel obtained in these examples is more than 5 times that in the atmosphere.

Test Nos. E-1 to E-8 are made of steel to which neither the first group element nor the second group element is added, and accelerated cooling was performed to examine the effect of the cooling stop temperature. Things. E-1 is naturally cooled as in the conventional method, and the crack growth rate in a wet hydrogen sulfide environment is not improved at least five times that in the atmosphere.

On the other hand, in test numbers E-3 to E-7, the accelerated cooling stop temperature is in the range of 600 to 400 ° C. defined in the present invention, and the crack growth rate is improved within three times that in the atmosphere. .
However, the test number E-2 has an accelerated cooling stop temperature that is too high, and the E-8 has an accelerated cooling stop temperature that is too low.
The crack growth rate in a wet hydrogen sulfide environment is hardly improved as compared with the conventional example.

Test numbers F-1 to F-6 shown in Table 3 were obtained by examining the effect of the cooling stop temperature under accelerated cooling conditions using steel to which Nb was added in the first group elements. . F-1 is naturally cooled as in the conventional method, and the crack growth rate in a wet hydrogen sulfide environment reaches eight times that in the atmosphere. On the other hand, trial number F-
For samples 3 to F-5, the accelerated cooling stop temperature is in the range of 600 to 400 ° C., and the crack growth rate is improved to within twice that of the atmosphere. However, in test No. F-2, the accelerated cooling stop temperature was too high, and in F-6, the accelerated cooling stop temperature was too low, and the crack growth rate in the wet hydrogen sulfide environment was almost improved as compared with the conventional example. Not.

The test numbers G-1 to G-4 in Table 3 were obtained by examining the effects of the accelerated cooling start temperature and the accelerated cooling temperature under accelerated cooling conditions using steel to which Cu in the second group elements was added. It is a thing.
Test numbers G-1 to G-3 have an accelerated cooling stop temperature of 600 to 400 ° C.
And the crack growth rate is less than twice that in the atmosphere even when the cooling rate is 6 ° C./s. But G
In No. -4, the accelerated cooling start temperature was too low, and the crack growth rate in a wet hydrogen sulfide environment was not so small as compared with the conventional example.

Test numbers H-1 to H-5 shown in Tables 3 and 4
The results of examining the effects of the accelerated cooling start temperature and the cooling rate under accelerated cooling conditions using a steel to which all the elements of the first and second groups are added as a material. Test Nos. H-1 and H-4 have accelerated cooling stop temperatures in the range of 600 to 400 ° C. and cooling rates of 25 ° C./s and 12 ° C./s, respectively. And a big improvement is recognized. However, in Test No. H-2, since the accelerated cooling start temperature is too low, the crack growth rate in a wet hydrogen sulfide environment is hardly improved as compared with the conventional example. Sample No. H-3 has a low cooling rate, and H-5 has a too high cooling rate, and these have poor improvement effects. Similarly, in sample No. I-1, the cooling rate was too low, and the improvement in crack growth characteristics in a wet hydrogen sulfide environment was small.

Test numbers I-2, J-1, K-1, M-1, N
-1 and O-1 are examples satisfying all the conditions defined in the present invention. In any case, the crack growth rate in a wet hydrogen sulfide environment is greatly improved to within 2 to 3 times that in the atmosphere.

[0058]

As shown in the examples, the steel sheet produced by the method of the present invention has a remarkably low fatigue crack growth rate in a wet hydrogen sulfide environment, and is within 2-3 times the fatigue crack growth rate in the atmosphere. Subsides. That is, this steel sheet is remarkably excellent in crack propagation characteristics, and is extremely practical as a steel sheet for a crude oil tanker which is exposed to a wet hydrogen sulfide environment and subjected to repeated stress.

[Brief description of the drawings]

FIG. 1 shows the results of a fatigue test of a conventional steel in air and in a wet hydrogen sulfide environment.

FIG. 2 is a graph showing the effect of hydrogen sulfide concentration on the fatigue crack growth rate of conventional steel.

Fig. 3 In a wet hydrogen sulfide environment (hydrogen sulfide concentration 1 vol.%)
FIG. 4 is a diagram showing the effect of the accelerated cooling stop temperature after hot rolling on the ratio of the crack growth rate to the crack growth rate in the atmosphere in Example 1.

FIG. 4A is a diagram showing an outline of a fatigue test apparatus, and FIG. 4B is a diagram showing the shape and dimensions of a test piece.

Claims (4)

[Claims] C .: 0.01 to 0.2% by weight, Si: 0.2 to 0.2% by weight.
0.6%, Mn: 0.3-2.0%, sol.Al: 0.01-0.1%, the balance is S: more than 0.003% and less than 0.020%, and continuous casting slab or ingot made of Fe and unavoidable impurities and hot forged or hot Rolling is completed in the temperature range of (Ar3 point -30 ° C) or higher, and without reheating from the temperature of (Ar3 point -30 ° C) or higher to the temperature range of 400 to 600 ° C at a cooling rate of 5 to 25 ° C / s. A method for producing a steel plate for a crude oil tanker having excellent fatigue crack growth characteristics in a wet hydrogen sulfide environment, wherein the steel plate is subjected to accelerated cooling and then cooled or gradually cooled. 2. C: 0.01 to 0.2% by weight, Si: 0.2 to 0.2% by weight
0.6%, Mn: 0.3-2.0%, sol. Al: 0.01-0.1%, and Nb: 0.01-0.1%, Ti: 0.01-0.1% and V: 0.01-0.1% Including the rest S:
Hot forging or hot rolling of continuous casting slabs or ingots containing 0.003% or more and 0.020% or less and inevitable impurities and Fe is completed in a temperature range of (Ar3 point -30 ° C) or more, and without reheating (Ar3 point Fatigue crack growth characteristics in a wet hydrogen sulfide environment characterized by accelerated cooling from the above temperature to a temperature range of 400 to 600 ° C at a cooling rate of 5 to 25 ° C / s, followed by cooling or slow cooling Method of manufacturing steel plate for crude oil tanker with excellent quality. (3) By weight%, C: 0.01 to 0.2%, Si: 0.2 to 0.2%
0.6%, Mn: 0.3-2.0%, sol. Al: 0.01-0.1%, further contains one or two of Cu: 0.1-1.0% and Cr: 0.1-2.0%, and the balance S: 0.003 % Or more and 0.020% or less and continually cast slabs or ingots composed of Fe and unavoidable impurities are subjected to hot forging or hot rolling at a temperature range of (Ar3 point −30 ° C.) or higher and without reheating (Ar3 point − 30
℃) 400-600 ℃ at a cooling rate of 5-25 ℃ / s from the above temperature
A method for producing a steel plate for a crude oil tanker, which has excellent fatigue crack growth characteristics in a wet hydrogen sulfide environment, wherein the steel plate is accelerated and cooled to a temperature range described above and then cooled or slowly cooled. 4. C .: 0.01 to 0.2% by weight, Si: 0.2 to 0.2% by weight
0.6%, Mn: 0.3-2.0%, sol. Al: 0.01-0.1%, and one or two of Cu: 0.1-1.0% and Cr: 0.1-2.0.%, And Nb: 0.01-0.1 %, Ti: 0.01-0.1
% And V: one or more of 0.01 to 0.1%, the balance being S: more than 0.003% and 0.020% or less and continuous casting slab or ingot made of unavoidable impurities and Fe is subjected to hot forging or hot rolling (Ar3 point- 30 ° C)
Wetting characterized by accelerated cooling from a temperature above (Ar3 point -30 ° C) to a temperature range of 400 to 600 ° C at a cooling rate of 5 to 25 ° C / s without reheating, and then allowing to cool or slowly cool A method for producing a steel plate for a crude oil tanker having excellent fatigue crack growth characteristics in a hydrogen sulfide environment.