JPH05337608A - Production of ni base hot rolling steel material - Google Patents

Abstract

(57) [Summary] [Purpose] N with good scale releasability during hot rolling.
A method for manufacturing an i-based hot rolled steel material is provided. [Structure] In weight%, the inner layer portion has C: 0.03 to 0.20
%, Si: 0.05-0.60%, Mn: 0.10-
1.60%, Ni: 3.25 to 10.0%, Sol. A
l: 0.010 to 0.10%, with the balance being iron and unavoidable impurities as the base metal, and the surface layer being C: 0.0.
3 to 0.20%, Si: 0.35% or less, Mn: 0.1
0 to 1.60%, Ni: 1.0% or less, Sol. Al:
A multilayer slab, which is coated with a steel containing 0.010 to 0.10% of balance iron and unavoidable impurities as a composite material, is manufactured by continuous casting and subjected to hot rolling.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a low temperature steel for a low temperature storage tank for land, a low temperature steel for an LPG or LNG ship, a steel for a submarine,
The present invention relates to a method for producing a Ni-based hot rolled steel material that requires low-temperature toughness, such as steel for marine structures for cold regions and steel for pipelines for cold regions.

[0002]

2. Description of the Related Art Ni conventionally used for the above-mentioned applications
In the case of steel series steel, scale peeling is insufficient with a descaler of about 150 atm, and in order to compensate for this, strict quality requirements are taken into consideration. Is applied, low temperature heating, low oxygen concentration heating, and scale flaw maintenance of the steel material after rolling are carried out, but the actual situation has not reached the fundamental solution.

[0003]

The above-mentioned conventional technique has not yet established a perfect scale flaw prevention technique for Ni-based hot-rolled steel materials, and not only is the maintenance costly, but also the appearance inspection is extremely difficult. The standard was rejected, and the loss was enormous. The present inventor conducted a detailed investigation on the scale releasability of the Ni-based hot rolled steel material, and found that N in the steel material component under the conditions of a normal heating atmosphere.
Fe has a higher oxidation rank than i, and Fe is selectively oxidized at the surface layer during slab heating, and Ni is not oxidized and is concentrated in Fe ₂ O ₃ as metal particles to form wedges on the ground iron. As a result, it was found that a subscale structure with extremely poor scale releasability was formed. Therefore, in order to solve such a problem, in the prior art, it was necessary to install an oxidation-free heating furnace or to develop a perfect technology for applying an antioxidant on the upper and lower surfaces.

Incidentally, as the Ni-based steel material, JIS G31
27, ASTM A203 / A353 / A553, MI
Typical examples are steel materials such as L-SHY100 and NDS-NS110.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the gist of the present invention is that the surface layer portion is made of steel having a component having a good scale releasability and the inner layer portion is made of Ni.
A multi-layer slab made of steel having the necessary properties as a low-temperature system steel is produced by continuous casting, and this multi-layer slab is used as the starting material, thus providing good heat with good scale peelability during hot rolling. It is possible to provide a method for manufacturing a rolled steel material.

In the present invention, the reason for producing a multi-layer slab by continuous casting is that a metal radical bond between the base material (inner layer portion) and the laminated material (surface layer portion) can be obtained as it is solidified, which is a troublesome slab. It does not require large new equipment such as anti-oxidant coating work, slab reversing work and non-oxidizing heating furnace after the refining treatment of the steel, and it is extremely economical not only in non-price competitiveness such as short construction period. This is advantageous.

For continuous casting of multi-layer cast slabs, for example, the method described in JP-A-63-108947 is preferable. The gist of the present invention is as follows. (1) C: 0.03 to 0.20% by weight of the inner layer portion,
Si: 0.05-0.60%, Mn: 0.10-1.6
0%, P: 0.015% or less, S: 0.010% or less,
Ni: 3.25 to 10.0%, Sol. Al: 0.01
The base layer is steel containing 0 to 0.10% and the balance iron and unavoidable impurities, and the surface layer portion is C: 0.03% by weight.
0.20%, Si: 0.35% or less, Mn: 0.10
1.60%, P: 0.025% or less, S: 0.020%
Hereinafter, Ni: 1.0% or less, Sol. Al: 0.010
Ni-based heat, characterized by comprising: continuously casting a multi-layered slab containing 0.1 to 0.10% of steel with the balance being iron and unavoidable impurities as a composite material, and hot-rolling the slab. Manufacturing method of rolled steel.

(2) C: 0.03% by weight of the inner layer portion
0.20%, Si: 0.05-0.60%, Mn: 0.
10 to 1.60%, P: 0.015% or less, S: 0.0
10% or less, Ni: 3.25 to 10.0%, Sol. A
L: 0.010 to 0.10%, with the balance being iron and unavoidable impurities as a base material, and the surface layer portion being wt% C: 0.20 to 0.40%, Si: 0.15% Below, M
n: 0.10 to 1.60%, P: 0.025% or less,
S: 0.020% or less, Ni: 1.0% or less, Sol.
A multi-layered slab containing Al: 0.010 to 0.10% and coated with steel consisting of balance iron and unavoidable impurities as a composite material is manufactured by continuous casting, and the slab is hot-rolled. And a method for manufacturing a Ni-based hot rolled steel material.

(3) In the base material, Cu: 1.0% or less, Cr: 2.% or less depending on strength, toughness or other requirements.
0% or less, Mo: 1.0% or less, Nb: 0.05% or less, V: 0.10% or less, Ti: 0.05% or less, B:
0.0050% or less, Ca: 0.0080% or less, RE
M: 0.0050% or less, 1 type or 2 types or more, and Cu: 0.30% or less, Cr: 0.50% or less, Mo: 0.50% or less, Nb: 0.025% in the composite material. Less than,
V: 0.050% or less, Ti: 0.05% or less, B:
0.0010% or less, Ca: 0.0080% or less, RE
M: 0.0050% or less of 1 type (s) or 2 or more types are contained, The manufacturing method of Ni type hot rolled steel material of the preceding clause 1 or 2 characterized by the above-mentioned.

[0010]

The present invention will be described in detail below. (1) Ni-based base material (inner layer portion) It is usual that various heat treatments are applied to the Ni-based hot rolled steel material targeted by the present invention, but heat treatment subsequent to heating / rolling (including controlled rolling) Processing heat treatment (TMC
P), quenching (Q, DQ), normalizing (N), and tempering (T) are available on the standard or in any combination. Controlled rolling may be applied to steel for line pipes.

If C exceeds 0.20%, the low temperature toughness and weldability are significantly impaired, and if it is less than 0.03%, the required strength cannot be ensured, so it is limited to 0.03 to 0.20%. Recently, from the viewpoint of SCC resistance in seawater, there is a tendency to lower the carbon content and supplement the strength with other elements. Si needs to be 0.05% or more in terms of deoxidation and strength, but addition of more than 0.60% deteriorates both low temperature toughness and weldability, so 0.05 to 0.6 is required.
Limited to 0%.

Mn must be 0.10% in terms of strength,
Since the addition of more than 1.60% deteriorates both the low temperature toughness and the weldability, it is limited to 0.10 to 1.60%. In addition, Japanese Patent Publication Sho 5
As disclosed in JP-A No. 8-39909, Si and Mn are N
(Si + Mn)% of temper embrittlement and hydrogen embrittlement in i type steel
Since it deteriorates in proportion to, 0.30% or less,
0.90% or less is preferable, but (Si + Mn) ≦ 1.0% is more preferable from the viewpoint of temper embrittlement and hydrogen embrittlement prevention, if allowed by specifications and strength.

P is 0.01 from the viewpoint of weldability and low temperature toughness.
Although it is limited to 5% or less, the lower the better. Although S is limited to 0.010% or less from the viewpoint of low temperature toughness, the lower the better, the more preferable.
It becomes more advantageous to add a and REM.

Ni is an essential main element for improving the low temperature toughness and is required to be 3.25% or more in order to exert the effect as a 3.5% to 9% Ni steel, but more than 10%. Even if added, neither strength nor low temperature toughness has an improving effect, so the content was limited to 3.25 to 10.0%. So
l. Although Al is required to be 0.010% or more for deoxidation and particle size adjustment, it is required to be 0.10% or less from the viewpoint of weldability, and it is limited to 0.010 to 0.10%. When B is added, Sol. It is preferable to add 0.03% or more of Al.

Needless to say, the C, Si, Mn, and Ni contents are appropriately designed based on the required characteristics (strength, low temperature toughness, etc.) in a predetermined heat treatment. Other alloy elements (Cu, Cr, Mo, Nb, V, T
(i, B, Ca, REM) may be contained in one kind or in combination of two or more kinds in order to further improve the required characteristics (strength, low temperature toughness, etc.), and the effect of the present invention is not impaired to some extent.

Therefore, the basic elements C, Si, Mn, etc. are reduced from the viewpoint of weldability, low temperature toughness, temper embrittlement, hydrogen embrittlement, etc., and Cu: 1.0% each for the purpose of weldability.
Below, Cr: 2.0% or less, Mo: 1.0% or less, N
b: 0.05% or less, V: 0.10% or less, Ti: 0.
05% or less, B: 0.0050% or less, Ca: 0.0080% or less, REM: 0.0050 from the viewpoint of low temperature toughness.
% Or less, and one or more of them may be selected and added in combination so as to achieve predetermined quality characteristics (strength, low temperature toughness, etc.).

(2) Laminated material (surface layer portion) C is 0.03 to 0.
It is limited to 20%, but from the viewpoint of scale releasability, it is 0.
A high C of 20% or more is preferable. However, 0.40%
If it exceeds the range, carburization of the inner layer becomes large. Therefore, when giving priority to scale releasability, it was limited to 0.20 to 0.40%.

As described in Japanese Patent Publication No. 57-52926, Si is preferably as low as possible from the viewpoint of preventing the formation of a low melting point eutectic substance which adversely affects the scale releasability. %, But if priority is given to scale releasability, it is limited to 0.15% or less. Mn is 0.10 to 1.60 in the same composition range as the inner layer portion.
Limited to%.

Since P and S are not required to be as strict as required characteristics as in the inner layer portion, 0.025% or less, 0.
It was limited to 020% or less. Ni is a main element that forms a subscale structure having poor scale releasability by being concentrated as metal particles in the oxide scale during slab heating, and is limited to 1.0% or less in order to prevent the formation of the above structure.
This is the most important technical idea when manufacturing a Ni-based multi-layer cast slab having a surface layer portion with good scale releasability that constitutes the present invention.

Sol. Al was limited to 0.010 to 0.10% in the same composition range as the inner layer portion. In addition, in view of the required characteristics of the inner layer portion, other alloy elements (Cu, Cr, Mo, N
When one or more of b, V, and B) are added in combination, it is preferable in terms of material that the surface layer portion and the inner layer portion have basically the same components. From the viewpoint of surface flaws, all of them are harmful components, and it is important to add as little as possible, and Cu: 0.30% or less,
Cr: 0.50% or less, Mo: 0.50% or less, Nb:
0.025% or less, V: 0.050% or less, B: 0.0
It was limited to 010% or less.

On the other hand, alloy elements other than the above (Ti, Ca,
REM) is a useful element from the viewpoint of fixing N in steel and preventing segregation of P and S in the solidification region near the mold during casting, and when added, it has the same composition range as the inner layer portion. Ti: 0.05% or less, Ca: 0.0080
% And REM: 0.0050% or less, respectively.

The lower limit of the slab thickness of the surface layer portion is preferably the slab thickness (scale loss) consumed by scale formation in heating and hot rolling, that is, 3 mm or more, and the upper limit is (minus product thickness (Tolerance x Reduction ratio + Scale loss thickness) Limited to less than or equal to, and in the case of a reduction ratio of 20, it is approximately 33
mm or less is preferable.

[0023]

EXAMPLES Examples of the present invention are shown in Tables 1 to 6 in comparison with conventional materials. Table 1 and Table 2 (continued from Table 1) are 3.5% N
Steel A3-J3 is a steel of the present invention and steels K3 and L3 are comparative examples. Steel J of the invention steels
3 is a surface layer high C-low Si material.

Tables 3 and 4 (continued from Table 3) are test materials of 9% Ni steel, steels A9 to G9 are steels of the present invention and steels H9 to
J9 is a comparative example. Among the steels of the present invention, Steels B9 and F9 are surface high C-low Si materials. Table 5 shows the production results of 3.5% Ni steel. Heat treatment is standard 900 ° C normalization (N) and 7
This is a general thermomechanical treatment (TMCP) in which accelerated cooling is performed after 60 ° C. × 30% CR. All materials are JIS G
3127 SL3N28 (equivalent to ASTM A203E)
However, the TMCP steel recently developed for shipbuilding materials is superior in low temperature toughness. Regarding the scale releasability, which is a characteristic of the steel of the present invention, in Table 5, the steel according to the present invention has extremely good results in terms of the maintenance rate due to scale and the rejection rate as compared with the comparative examples. Above all, measures against not only Ni-based scales but also Si-based scales (surface layer high C-low S
It can be seen that the scale peelability of the invention steel J3 in consideration of i) is particularly excellent. It should be noted that the low temperature heating material and the thin material tend to have slightly better scale releasability in both the steel of the present invention and the comparative example.

Table 6 shows the production results of 9% Ni steel. Heat treatment is performed after normalizing twice at 900 ° C, 790 ° C, and 590 ° C, followed by tempering (NNT), 900 ° C quenching (Q), 590 ° C tempering (T), and quenching (DQ) following rolling 590
C. Tempering (T). All materials are JIS G 3
127 SL9N53 and 60 (ASTM A353
And 553), but the DQT material is also slightly superior in low temperature toughness. Regarding the scale releasability, which is a characteristic of the steel of the present invention, in Table 6, the steel according to the present invention has extremely good results in terms of both the maintenance rate due to scale and the rejection rate as compared with the comparative example. Among them, it can be seen that the scale releasability of the steels B9 and F9 of the present invention is particularly excellent in consideration of measures against not only the Ni-based scale but also the Si-based scale (surface layer high C-low Si). It should be noted that the low temperature heating material and the thin material tend to have slightly better scale releasability in both the steel of the present invention and the comparative example.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

As described above, according to the present invention, a Ni-based hot rolled steel material having poor scale releasability is used as an inner layer, and a multi-layer cast product having a steel material having excellent scale releasability as a surface layer is produced by continuous casting, By hot rolling the slab, it is possible to produce a Ni-based hot-rolled steel material having extremely good scale releasability, so not only improving the non-price competitiveness by shortening the construction period,
Since the maintenance rate and rejection rate due to the scale of the hot-rolled steel material can be significantly reduced and the cost competitiveness can be improved, the industrial effect of the present invention is extremely remarkable.

Claims (3)

[Claims] 1. The inner layer portion in% by weight is C: 0.03 to 0.2.
0%, Si: 0.05 to 0.60%, Mn: 0.10
1.60%, P: 0.015% or less, S: 0.010%
Hereinafter, Ni: 3.25 to 10.0%, Sol. Al:
Steel containing 0.010 to 0.10% and the balance iron and unavoidable impurities is used as a base material, and the surface layer portion is C: 0.03 to 0.20% by weight% and Si:
0.35% or less, Mn: 0.10 to 1.60%, P:
0.025% or less, S: 0.020% or less, Ni: 1.
0% or less, Sol. Al: 0.010 to 0.10%, characterized in that a multi-layer cast slab coated with steel consisting of balance iron and unavoidable impurities as a composite material is manufactured by continuous casting, and the slab is hot rolled. And a method for manufacturing a Ni-based hot rolled steel material. 2. The inner layer portion in% by weight is C: 0.03 to 0.2.
0%, Si: 0.05 to 0.60%, Mn: 0.10
1.60%, P: 0.015% or less, S: 0.010%
Hereinafter, Ni: 3.25 to 10.0%, Sol. Al:
Steel containing 0.010 to 0.10% and the balance iron and unavoidable impurities is used as a base material, and the surface layer portion is C: 0.20 to 0.40% by weight, Si:
0.15% or less, Mn: 0.10 to 1.60%, P:
0.025% or less, S: 0.020% or less, Ni: 1.
0% or less, Sol. A multi-layered slab containing Al: 0.010 to 0.10% and coated with steel consisting of balance iron and unavoidable impurities as a composite material is manufactured by continuous casting, and the slab is hot-rolled. And a method for manufacturing a Ni-based hot rolled steel material. 3. The base material further has Cu: 1.0% or less, Cr: 2.0% or less, Mo: 1.0% or less, Nb: 0.05%, depending on strength, toughness, or other requirements. Below, V:
0.10% or less, Ti: 0.05% or less, B: 0.00
50% or less, Ca: 0.0080% or less, REM: 0.
One or two or more of 0050% or less are contained, and Cu: 0.30% or less, Cr: 0.50% or less, Mo:
0.50% or less, Nb: 0.025% or less, V: 0.0
50% or less, Ti: 0.05% or less, B: 0.0010
% Or less, Ca: 0.0080% or less, REM: 0.00
The method for producing a Ni-based hot-rolled steel material according to claim 1 or 2, wherein 50% or less is contained in one kind or two or more kinds.