JP2541070B2 - Method for producing high nickel alloy clad steel sheet with excellent brittle fracture propagation stopping properties of base material - Google Patents

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 high nickel alloy clad steel plate as a base material by rolling,
An object of the present invention is to provide a method capable of appropriately manufacturing a high nickel alloy clad steel sheet excellent in brittle fracture propagation stopping properties of a base material.

[0002]

2. Description of the Related Art Low temperature toughness, especially for brittle fracture propagation stopping properties, for pipelines, chemical tankers, marine structures, icebreakers, etc. that transport gas containing a large amount of hydrogen sulfide and carbon dioxide gas. Excellent clad steel is demanded, and in these applications, naturally, corrosion resistance of the composite material selected according to the application, joint strength between the composite material and the base metal, and strength and low temperature toughness for the base material , The propagation stopping property of brittle fracture is required.

Further, as a main manufacturing method for obtaining these clad steels, there are a joining method by rolling, an explosive welding method, a surfacing method and a casting method, but in view of productivity, cost and manufacturable dimensions. The method of joining by rolling is excellent and widely used.

The following several methods have been proposed as a method for producing a high nickel alloy clad steel sheet. C: A preliminary clad material formed by combining a base material made of a carbon steel or a low alloy steel of 0.3% or less with a composite material of an austenitic material is heated to a temperature of 1000 ° C. or more and hot worked to form a clad, 8 as it is after hot working
A method of performing quenching treatment from a temperature of 00 ° C. or higher, or tempering treatment after the quenching at a temperature of Ac ₁ point or less of the base material (Japanese Patent Laid-Open No. 6-58242)
1-144284).

C: An assembled composite composed of a base material made of carbon steel or a low alloy steel containing 0.2 wt% or less and a Ni-base alloy composite material is heated to 1050 ° C. or higher,
Rolling is completed so that the average temperature of the laminated material exceeds 900 ° C., and then the temperature range of 800 ° C. or more and 850 ° C. or less is cooled at a cooling rate of less than 2 ° C./sec.
4 at an average cooling rate of 2 to 20 ° C / sec from a temperature above ℃
A method of cooling to a temperature range of 50 ° C. or higher and 550 ° C. or lower and then air-cooling (JP-A-2-30712).

[0006]

However, Japanese Patent Laid-Open No. Sho 61-61
In No. 144284, when hot working is performed in the recrystallization temperature range of the base material, a fine austenite structure cannot be obtained, so that good toughness cannot be obtained even by rapid cooling. Further, after the rolling, a tempering treatment at an Ac ₁ point or less causes precipitation of Cr carbides at the crystal grain boundaries of the laminated material, resulting in sensitization.
It is unavoidable that the intergranular corrosion resistance deteriorates as compared with the material as it is cooled with water.

Further, in the method disclosed in JP-A-2-30712, the toughness is insufficient as described in the examples. From the viewpoint of maximizing the toughness of the base metal, the above method does not perform finish rolling under the optimum conditions,
The toughness of the base material is low because the base material cannot be made finer.
Drop Weight Tear Test, which is a test method for evaluating the brittle fracture propagation stopping property of steel sheet specified in the 5L standard
The temperature at which the ductile fracture surface ratio of (DWTT) shows 85% (85%
SATT) is higher than room temperature and cannot be used for the applications requiring the above-mentioned low temperature toughness and brittle fracture propagation stopping property.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised through repeated studies in view of such a situation as described above, and has the same joining strength at the interface between the laminated material and the base material as that of clad steel finished at high temperature. While maintaining the same stable and high level,
To provide a manufacturing method of a high nickel alloy clad steel sheet excellent in brittle fracture propagation stopping property of a base material by a corrosion condition of a laminated material, a low temperature toughness of a base material, and a rolling condition that maximizes the propagation stopping property of brittle fracture. Is a successful one.

The inventors of the present invention investigated the influence of rolling conditions when a high nickel alloy having various component compositions was used as a composite material and a base material having various component compositions was clad rolled, and as a result, the composite material was obtained. The amount of C is reduced, and the base material is used as the specific component composition, and the necessary minimum amount of reduction is obtained to obtain a sufficiently high and stable bonding strength at high temperature.
It is said that a high nickel alloy clad steel sheet excellent in joint strength as well as corrosion resistance and brittle fracture propagation arresting property can be obtained by water cooling to 450 ° C. or lower immediately after a large reduction of 850 ° C. or lower Ar ₃ points to −20 ° C. Gaining knowledge,
The present invention has been made based on such knowledge and is as follows.

(1) A high nickel alloy having a C content of 0.02% or less by weight is used as a composite material, and C: 0.02 is used as a base material.
~ 0.1%, Si: 0.05-0.5%, Mn: 0.5
~ 2.0%, Nb: 0.005 to 0.05%, Al: 0.01 to 0.
After heating the slab assembled with steel containing 06% and the balance iron and unavoidable impurities to 1100 ° C. or higher, the reduction ratio was 3.0 in the temperature range of 1000 ° C. or higher.
As described above, the base material is rolled at a temperature of 850 ° C. or lower at a rolling point of 50% or higher in a temperature range of Ar ₃ points to −20 ° C., and immediately after completion of the rolling, water-cooled to a temperature of 450 ° C. or lower. Of manufacturing a high nickel alloy clad steel sheet having excellent brittle fracture propagation stopping properties of.

(2) A high nickel alloy having a C content of 0.02% or less by weight is used as a composite material, and C: 0.02 is used as a base material.
~ 0.1%, Si: 0.05-0.5%, Mn: 0.5
~ 2.0%, Nb: 0.005 to 0.05%, Al: 0.01 to 0.
06% and Cu: 1.5% or less, N
i: 3.0% or less, Cr: 0.3% or less, Mo: 0.3% or less, V: 0.08% or less, Ti: 0.08% or less,
B: 1100 of a slab assembled using steel containing at least one of 0.0020% or less and Ca: 0.004% or less, with the balance being iron and inevitable impurities.
After heating to ℃ or more, in the temperature range of 1000 ℃ or more, the reduction ratio of 3.0 or more, 850 ℃ or less of the base material Ar ₃ points-2
A high-nickel alloy clad steel sheet excellent in brittle fracture propagation stopping properties of a base material, which is characterized by rolling at a rolling reduction of 50% or more in a temperature range up to 0 ° C. and immediately followed by water cooling to a temperature of 450 ° C. or less. Production method. Manufacturing method of gold clad steel sheet.

[0012]

The structure of the present invention is roughly divided into the following three points. In order to obtain a stable and high bonding strength, heating is performed to 1100 ° C. or higher, and a reduction ratio of 1000 ° C. or higher is set to a necessary minimum to secure a room for a reduction amount for improving the toughness of the base material. The base material has a composition of a low C-Nb system, and fine austenite grains are obtained by subjecting it to high pressure within a temperature range of 850 ° C or less Ar ₃ points -20 ° C or more, and water cooling to 450 ° C or less after rolling is completed. To obtain a fine structure. This ensures good toughness. Since finish rolling is performed at an Ar ₃ point of the base material −20 ° C. or higher and a temperature lower than the recrystallization temperature of the composite material, work hardening of the composite material is unavoidable, but the C content of the composite material is reduced, and By cooling with water after the completion of rolling, the sensitization of the composite material is suppressed and the corrosion resistance equivalent to that of the solution heat treatment is secured.

As described above, it is known that a stable and high bonding strength can be obtained by obtaining a large amount of reduction at the above high temperature. However, it is not known about the minimum necessary amount of reduction that can stably obtain a high bonding strength, and this is explained. FIG. 1 shows that the reduction ratio of 1000 ° C. or more in rolling of clad steel using 825 alloy as a composite material. It shows the joint strength when is changed. The heating temperature is 1180 ° C. In addition, the joint strength of the interface is JIS
It was evaluated by the shear test specified in G 0601.
As is clear from FIG. 1, when the rolling reduction ratio of 1000 ° C. or higher reaches a certain value or higher, stable high shear strength is obtained, and the minimum required rolling reduction ratio is that of a high nickel alloy typified by 825 alloy as a composite material. When I did it was 3.0.

Next, in order to explain the above, the following experimental results were prepared. That is, FIG. 2 shows the test material 1 shown in Table 1 below.
Shows the effect of the water cooling stop temperature after rolling on the strength and toughness. The heating temperature is 1170 ° C,
In the temperature range of 850 ° C. or lower Ar ₃ points −20 ° C. or higher, the reduction rate was 50%. As is clear from FIG. 2, the strength increases with the decrease in the water cooling stop temperature, and the DWT
It can be seen that 85% SATT of T has shifted to the low temperature side.

[0015]

[Table 1]

Further, in FIG. 3, for the test material 2 in Table 1, Ar ₃ point-2 at 850 ° C. or lower which affects the strength and toughness after rolling.
The influence of the rolling reduction in the temperature range of 0 ° C. or higher is shown. The heating temperature was 1180 ° C., which was 45 immediately after rolling.
It was cooled to 0 ° C with water. As is clear from the figure, the toughness of the base material is improved with an increase in the rolling reduction in the temperature range of 850 ° C. or lower and Ar ₃ points −20 ° C. or higher. As mentioned above,
It can be seen that in order to improve the toughness of the base material, especially the propagation stopping property of brittle fracture, water cooling under high pressure in the low temperature range of austenite and immediately after rolling is effective.

The above will be further described. It is known that sensitization of a high nickel alloy used as a composite material can be suppressed by water cooling after rolling in a non-recrystallization temperature range.
Here, the experimental results on the effect of the amount of C on the corrosion resistance of the composite material subjected to high pressure in the non-recrystallization temperature range of the composite material will be described. FIG. 4 shows the influence of the rolling reduction in the temperature range of 850 ° C. or less Ar ₃ points −20 ° C. on the hardness of the cladding material of the clad steel using the 825 alloy shown in Table 2 below. The heating temperature is 1180 ° C and 400 ° C immediately after rolling.
It was performed under the condition that it was cooled with water.

[0018]

[Table 2]

As is apparent from FIG. 4 described above, the hardness increases as the rolling reduction increases. The following Table 3 shows
5 is a summary of the results of the intergranular corrosion test of the clad steel produced under various rolling conditions shown in FIG. The intergranular corrosion test is a sulfuric acid / ferric sulfate test based on JIS G 0572, a so-called striker test, and the solution treatment in the table is a condition of holding at 1100 ° C. for 10 minutes and then water cooling. The table also shows the test results of the test materials shown in Table 2 and the results of other laminated materials produced by the same rolling method. However, the C content of the laminated materials was reduced, and It can be seen that, by cooling with water immediately after rolling, the corrosion rate becomes a value equivalent to that of the solution treatment as it is, without performing the solution treatment.

[0020]

[Table 3]

As a result of the combination of the above-mentioned technologies (1) to (3), it is possible to obtain a high bonding material having excellent bonding strength, excellent toughness of the base material and excellent brittle fracture propagation stopping property, and equivalent corrosion resistance as the solution heat treatment. The nickel alloy clad steel can be manufactured appropriately.

A more specific reason for limitation in the present invention will be explained. First, as a reason for limiting the component composition of the composite material, the smaller the amount of C in the composite material, the more desirable it is from the viewpoint of corrosion resistance. That is, as the amount of C increases, in the cooling process after rolling
There is concern about deterioration of corrosion resistance due to precipitation of Cr carbide. Therefore, the corrosion resistance of the laminated material can be obtained at the same level as that of the solution heat-treated material by the rolling conditions specified in the present invention.
The amount of C was limited to an upper limit of 0.02%.

Next, the reasons for limiting the component composition of the base material are as follows. C is an important strengthening element, but if it is less than 0.02%, steel for line pipes, steel for shipbuilding,
Since sufficient strength as steel for offshore structures cannot be obtained,
The lower limit was 0.02%. On the other hand, when the content exceeds 0.1%, the weldability and the toughness of the welded portion are impaired, and the corrosion resistance is impaired as the C content of the overlay weld metal is increased by diluting the base metal, so the upper limit is 0.1. %.

Si is an element necessary for deoxidation in the steelmaking process and is also a solid solution strengthening element. If it is less than 0.05%, the deoxidizing effect is not sufficient, while if it exceeds 0.5%, the toughness and workability are adversely affected, so it was limited to the range of 0.05 to 0.5%.

Mn is an important element after C. Mn
Since it lowers the Ar ₃ point, it is an element that facilitates rolling in the low temperature range of austenite, and that works effectively for improving strength and toughness. However, if it is less than 0.5%, the strength and toughness required for the above-mentioned applications cannot be secured. On the other hand, excessive addition adversely affects toughness and weldability, so 0.5 to 2.
Limited to 0%.

Nb suppresses recrystallization of austenite,
It has the effect of expanding the recrystallization temperature range. Therefore, elongation of austenite grains and introduction of deformation zones become easy,
Significant grain refinement is achieved and toughness is improved. It is also effective as a precipitation strengthening element. In order to exert these effects, it is necessary to add 0.005% or more, but excessive addition adversely affects the weldability and the toughness of the welded part.
0.005 to 0.05%.

Al is an important element for deoxidation in the steelmaking process and has an effect on improving the toughness of the heat affected zone of welding. However, if it is less than 0.01%, the deoxidizing effect is not sufficient. On the other hand, if it is added in an amount exceeding 0.06%, the toughness improving effect of the weld heat affected zone is saturated, so 0.01 to 0.06% is required. Limited to.

The object steel in the present invention has the above-mentioned composition as a basic component, but one kind of Cu, Ni, Cr, Mo, V, Ti, B and Ca is used for adjusting required toughness and the like. Or 2
More than one species may be included. That is, the reasons for limiting the above-mentioned elements that are further contained in the above-mentioned basic components will be described below.

Cu has the effect of refining the microstructure by improving the hardenability of the low C steel and thus contributes to the improvement of the toughness. Further, by aging treatment, precipitation in the ε-Cu phase is achieved and a remarkable improvement in strength is achieved. However, 1.5%
If added in excess of 0.5%, surface cracking due to Cu tends to occur during heating, so the content was limited to 1.5% or less.

Ni is an element effective for improving the toughness and also has an effect of preventing the generation of Cu defects. However, addition of a large amount impairs weldability and is economically disadvantageous. The upper limit was set.

Cr, Mo, and V all have the effect of refining the microstructure by improving the hardenability of the low C content steel, and thereby contribute to the improvement of the toughness. However, excessive addition adversely affects toughness and weldability, so Cr is 0.3% and Mo is 0.3%.
% And V is limited to 0.08% or less.

Like Nb, Ti is an element effective in improving the toughness by suppressing the recrystallization of austenite and refining the structure. It is also effective in improving the toughness of the weld heat affected zone.
However, excessive addition adversely affects toughness and weldability, so the content was made 0.08% or less.

B can improve the hardenability remarkably even if added in a small amount. In the low C content steel, it has an effect of refining the structure by improving the hardenability, which contributes to the improvement of the toughness. However, if the content exceeds 0.0020%, the toughness of the welded portion is significantly impaired, so the content is limited to 0.0020% or less.

Ca has the effect of controlling the morphology of sulfides, which contributes to the improvement of toughness. However, excessive addition causes deterioration of weldability as well as toughness, so 0.004%
Below.

Next, the reason for limiting the manufacturing conditions in the present invention will be explained. First, the heating temperature is, but as described above, in order to increase the bonding strength at the interface, it is necessary to reduce the necessary amount at 1000 ° C. or higher. . Below 1100 ° C, 1000
It becomes difficult to apply a predetermined reduction amount up to ° C. Further, it is desirable to heat to a high temperature in order to form a solid solution of the Cr carbide of the composite material in the matrix. Considering the above, the heating temperature was limited to 1100 ° C or higher.

Further, the necessary reduction ratio of 1000 ° C. or higher should be limited to 3.0 or higher, which can stably obtain high shear strength when the alloy material is a high nickel alloy as shown in FIG. .

Further, for the toughness of the base material and the brittle fracture propagation stopping property, the temperature at which the reduction is applied is 850 ° C. or less, Ar ₃ point −20.
The reason for limiting the range to ℃ is 850
° C. The excess when austenite grains lengthening for austenite grains recrystallization, the introduction of deformation zones are difficult, that the tissue finer after rolling can not be obtained, in a two-phase range below Ar ₃ point -20 ° C. This is because island-like martensite is likely to appear in the structure of the base material that has been subjected to reduction and then water-cooled to 450 ° C. or less, resulting in deterioration of toughness. 850 ° C or less Ar ₃ points -20
As for the rolling reduction in the temperature range up to ℃, as shown in FIG. 3, it is generally required for carbon steel line pipe materials to be less than 50%, and the ductile fracture surface ratio of DWTT at −10 ° C. is 85%. 50% because the above goal cannot be secured
Limited to the above.

As for the stop temperature of the water cooling applied immediately after rolling, as shown in FIG. 2, the DWTT characteristics are affected together with the strength, and if the water cooling is stopped at a high temperature of 550 ° C., the DWTT characteristics cannot secure the above required value. . Further, in order to suppress the sensitization of the laminated material, it is desirable to perform water cooling to a low temperature of 550 ° C. or lower. Considering the above two points,
The water cooling stop temperature was limited to 450 ° C or lower. The cooling rate in water cooling is not particularly limited, but when considering the toughness of the base material and the corrosion resistance of the laminated material, it is 2 to 20 ° C / sec.
Is desirable.

[0039]

EXAMPLES Specific examples according to the present invention will be described. A base material and a composite material having the component compositions shown in Table 4 below are prepared.
It was manufactured in the combinations and conditions shown in Table 5 below.
A tensile test, a V-notch Charpy test, a DWTT, a shear test, and an intergranular corrosion test were performed on the obtained clad steel sheet. The tensile test piece and the DWTT test piece are base material full-thickness test pieces in which the laminated material is removed by machining. However, for the No. 20 thick DWTT test piece, API RP 5L3 Second Edition was used due to the limitation of tester capacity.
A test piece reduced in thickness to 19 mm according to (1978) was used. The V-notch Charpy test piece was taken from the center of the plate thickness of the base material. The shear test was performed according to JIS G 0601, and the intergranular corrosion test of the laminated material was according to JIS G 0507 (sulfuric acid / ferric sulfate test).

[0040]

[Table 4]

[0041]

[Table 5]

The results of each test as described above are shown in Table 6 below.

[0043]

[Table 6]

That is, according to the results of Table 6, the comparative clad steel plate No. 5 has a reduction rate of less than 50% in the temperature range of 850 ° C. or lower Ar ₃ points −20 ° C. or higher, and DW
The 85% SATT of TT is 0 ° C or higher, and the target value of -10 ° C cannot be used.
Comparative clad steel plate No. 6 was not water-cooled after rolling, had insufficient DWTT characteristics, and was inferior in corrosion resistance.

Further, the comparative clad steel plate No. 16 is 85
0 ° C or less Ar ₃ points, a reduction rate of 5 in the temperature range of -20 ° C
It is less than 0% and the water cooling stop temperature is 450 ° C.
Since it is higher, the DWTT characteristic is inferior.
Comparative clad steel No. 17 had a water cooling stop temperature of 4 after rolling.
The temperature is higher than 50 ° C, and the DWTT characteristics are inferior. Further, although the comparative clad steel sheet No. 19 has finish rolling conditions within the scope of the present invention, the reduction ratio at 1000 ° C. or higher is less than 3.0, and the toughness of the base material and the corrosion resistance of the laminated material are excellent. , The joint strength is not enough. The comparative clad steel sheet No. 20 is 1000
DWTT characteristics are inferior because they are subjected to high pressure at a temperature of ℃ or more, and further, corrosion resistance is inferior because they are not water-cooled after rolling.

In contrast to the above-mentioned comparative materials, in the examples of the present invention, a high shear strength was stably obtained, and the corrosion resistance of the laminated materials was as shown by comparison with Table 3, It is equivalent to the as-solution treated material. Also, D
It was confirmed that WTT 8 was also excellent at −10 ° C. or lower.

[0047]

As described above in detail, according to the method of the present invention, a stable and high bonding strength is obtained, and in the composite material, the same corrosion resistance as that obtained by the solution heat treatment is obtained. It is possible to manufacture a clad steel sheet using a high nickel alloy having excellent low temperature toughness including brittle fracture propagation stopping properties of the material as a composite material, and is an invention having a great industrial effect.

[Brief description of drawings]

FIG. 1 is a chart showing the effect of a rolling reduction ratio of 1000 ° C. or higher on shear strength.

FIG. 2 is a chart showing the influence of the water cooling stop temperature after rolling on the mechanical properties of the base material.

FIG. 3 is a chart showing the influence of the reduction rate between 850 ° C. and below Ar ₃ points and −20 ° C. on the mechanical properties of the base material.

[Fig. 4] Ar ₃ points-2 at 850 ° C or lower that affects the hardness of the laminated material
It is a chart showing the influence of the rolling reduction between 0 ° C.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masahiro Katahira 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Co., Ltd. (72) Toru Izawa 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Pipe Incorporated (56) Reference JP 63-130283 (JP, A) JP 4-75791 (JP, A) JP 4-128314 (JP, A) JP 4-182080 (JP, A) JP 4-197588 (JP, A) JP 5-261567 (JP, A) JP 5-214446 (JP, A) JP 5-214499 (JP, A) JP S60 -43465 (JP, A) JP 61-235084 (JP, A) JP 62-179878 (JP, A) JP 62-214887 (JP, A) JP 64-40189 (JP, A) ) JP-A-4-263016 (JP, A)

Claims (2)

(57) [Claims] 1. A high nickel alloy having a C content of 0.02% or less by weight as a composite material, and as a base material, C: 0.02 to 0.1%, Si: 0.05 to 0.5. %,
Mn: 0.5-2.0%, Nb: 0.005-0.05%, Al: 0.01-0.06%, assembled with steel consisting of balance iron and inevitable impurities After heating the slab to over 1100 ° C, 10
In a temperature range of 00 ° C or higher, a reduction ratio of 3.0 or higher, 85
The brittleness of the base material, which is characterized in that the base material is rolled at a rolling reduction of 50% or more in a temperature range of up to Ar ₃ point −20 ° C. at a temperature of 0 ° C. or lower, and immediately water-cooled to a temperature of 450 ° C. or lower after completion of the rolling. A method for producing a high nickel alloy clad steel sheet having excellent fracture propagation stopping properties. 2. A high nickel alloy having a C content of 0.02% or less in weight% is used as a composite material, and as a base material, C: 0.02 to 0.1% and Si: 0.05 to 0.5. %,
Mn: 0.5-2.0%, Nb: 0.005-0.05%, Al: 0.01-0.06%, Cu: 1.5% or less, Ni: 3.0 % Or less, Cr: 0.
3% or less, Mo: 0.3% or less, V: 0.08% or less, Ti: 0.0.
1100 of a slab assembled from steel containing one or more of B: 0.0020% or less, B: 0.0020% or less, and Ca: 0.004% or less, with the balance being iron and unavoidable impurities.
After heating to ℃ or more, in the temperature range of 1000 ℃ or more, the reduction ratio of 3.0 or more, 850 ℃ or less of the base material Ar ₃ points-2
A high-nickel alloy clad steel sheet excellent in brittle fracture propagation stopping properties of a base material, which is characterized by rolling at a rolling reduction of 50% or more in a temperature range up to 0 ° C. and immediately followed by water cooling to a temperature of 450 ° C. or less. Production method.