JP2953288B2 - Stainless steel plate with excellent TIG weldability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel sheet having excellent TIG weldability, and more particularly, to a sheet thickness of 3 mm.
When performing the so-called non-filler fillet welding without using a welding wire and additive wire on the following stainless steel sheets, the proper bead shape is maintained, undercut, and perforated or scale-shaped on the weld bead surface. The present invention relates to a stainless steel plate excellent in TIG weldability, in which defects such as swelling do not occur.

[0002]

2. Description of the Related Art For example, when a shell structure of a container made of a stainless steel sheet is manufactured by welding, ends of the stainless steel sheet to be welded are overlapped with each other, and a welding wire and a welding wire are attached to the overlapped portion. A so-called non-filler fillet welding without using an additive wire has been performed. By welding in this manner, the liquid-tightness of the weld is ensured, and the welding material is saved,
Economical efficiency can be improved in terms of materials and equipment.

[0003] When performing non-filler fillet welding on a stainless steel sheet, it is required to secure a bead shape of a lap welded part and prevent occurrence of welding defects as welding characteristics. Affects directly.

The following items are required as bead shapes of lap welds. In order to maintain the minimum strength characteristics as a joint when welding the overlapped ends of the two stainless steel sheets 1 and 2 shown in FIG. The distance from the surface is 70% of the thickness of each of steel plates 1 and 2.
That is all. When the overlapped ends of the two stainless steel sheets 1 and 2 are welded by fillet welding, the toe angle θ, that is, the lower steel sheet, so as not to be regarded as a suspicious defect in the color check for maintaining the fatigue characteristics and inspecting the defects. The angle θ between the surface of No. 2 and the weld bead 3 is 40 ° or less.

[0005] In order to prevent the occurrence of welding defects in a lap weld, the following items are required. No undercut occurs. No defects such as perforations or scale-like swells occur on the surface of the weld bead.

[0006] If the bead shape of the lap weld does not satisfy the above-mentioned conditions, or if the above-mentioned welding defect occurs in the lap weld, the joint strength of the container structure is degraded, and as a container, A problem arises that the liquid tightness of the liquid is impaired.

As a technique for preventing high-temperature cracking of a stainless steel plate, for example, a steel having the following chemical composition has been disclosed (hereinafter referred to as Prior Art 1). JP-A-49-126513 Si ≦ 0.25wt.%, Si / C ≦ 4.0, 0.02 ≦ N ≦ 0.25wt.% JP-A-59-153870, C ≦ 0.08wt.%, Si ≦ 1.00wt.%, Mn ≦ 2.00wt.%, P ≦ 0.045
wt.%, S ≦ 0.030wt.%, 18.00 ≦ Cr ≦ 20.00wt.%, 8.00
≤Ni≤13.00wt.%, Cu ≤0.08wt.%, -0.7≤Ni balance ≤-2.5,

As a technique for suppressing undercut and burn-through during butt welding of stainless steel thin steel plates, a steel having the following chemical composition has been disclosed (hereinafter referred to as prior art 2). JP-A-63-60260 0.03 ≦ C ≦ 0.08wt.%, 0.40 ≦ Si ≦ 0.60wt.%, 1.10 ≦ Mn
≤1.50wt.%, P ≤0.040wt.%, S ≤0.010wt.%, 0.08≤
Cu ≦ 0.20wt.%, 8.00 ≦ Ni ≦ 10.00wt.%, 18.00 ≦ Cr ≦ 1
9.00wt.%, Al ≦ 0.020wt.%, N ≦ 0.065wt.%, O ≦ 0.0
60 wt.%, Mn / Si <3.0, 1.670 ≦ 1.5 × Si + 0.5 × Mn + 10
√S ≤2.160

As a stainless steel for high-speed welding that suppresses the occurrence of undercut, a steel having the following chemical composition has been disclosed (hereinafter referred to as Prior Art 3). JP-A-61-288053 1.C ≦ 0.08wt.%, Si ≦ 0.6wt.%, 1 ≦ Mn ≦ 6wt.%, 6 ≦
Ni ≦ 15wt.%, 16 ≦ Cr ≦ 20wt.%, Mn / Si ≧ 3 2.In claim 1, S ≦ 0.003wt.% 3.C ≦ 0.08wt.%, Si ≦ 0.6wt.%, 1 ≦ Mn ≦ 6wt.%, 6 ≦
Ni ≦ 15wt.%, 16 ≦ Cr ≦ 20wt.%, Mo ≦ 3wt.%, Mn / Si ≧ 3 4.In claim 3, S ≦ 0.003wt.%

[0010]

In prior art 1, when non-filler fillet welding is performed on a lap portion, the bead shape of the lap weld portion is ensured, and undercuts and surface defects of the bead portion are caused. There is a problem that cannot be prevented.

The prior arts 2 and 3 deal with the occurrence of undercut and burn-through defects in a completely penetrated joint. Therefore, according to the prior arts 2 and 3, when performing non-filler fillet welding of the overlapped portion on a stainless steel sheet having a thickness of 3 mm or less,
Requirements for lap weld bead shape (throat thickness d:
It is not possible to prevent the occurrence of welding defects such as 70% or more of the thickness of the steel sheet and the toe angle θ: 40 ° or less), and undercuts or holes or scale-like swells generated on the bead surface.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and in particular, when performing non-filler fillet welding on a stainless steel sheet having a sheet thickness of 3 mm or less, an appropriate bead shape is maintained, and undercutting is performed. Another object of the present invention is to provide a stainless steel sheet excellent in TIG weldability, in which defects such as perforations and scale-like protrusions do not occur on the surface of a weld bead.

[0013]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems and to develop a stainless steel sheet excellent in TIG weldability. As a result, it has been found that there is an appropriate lower limit for the O and S contents in the steel with respect to the weldability, and sufficient weldability cannot be obtained unless the O and S contents are in the appropriate ranges.

The present invention has been made based on the above findings, and the stainless steel sheet of the present invention is characterized by having the following chemical composition. Carbon (C): 0.11 wt.% Or less, Silicon (Si): 0.2-1 wt.%, Manganese (Mn): 0.2-2 wt.%, Chromium (Cr): 11-30 wt.% Oxygen (O) : 0.009 wt.% Or less, sulfur (S): 0.008 wt.% Or less, and at least one element selected from the group consisting of: calcium (Ca): 0.0004 to 0.0065 wt.%, Magnesium (Mg): 0.0004 0.0065 wt.%, And if necessary, nickel (Ni): 6 to 22 wt.%, And the remainder: substantially iron (Fe), and 0.0045 wt.% ≤ 0+ (1/2 ) ×
S ≦ 0.012 wt.% Is satisfied.

[0015]

The chemical composition of the stainless steel sheet of the present invention is
The reason for limiting to the above range will be described below. (1) Carbon (C): When the C content exceeds 0.11 wt.%, It has an adverse effect on intergranular corrosion and workability of the stainless steel sheet.
Therefore, the C content should be limited to 0.11 wt.% Or less.

(2) Silicon (Si): Si is indispensable as a deoxidizing element during melting and refining. However, if the Si content is less than 0.2 wt.%, Desired effects cannot be obtained in the above-described operation. On the other hand, when the Si content exceeds 1 wt.%, The viscosity of the molten metal at the time of welding is drastically reduced. Therefore, the Si content should be limited to the range of 0.2-1 wt.%.

(3) Manganese (Mn): Like Si, Mn is indispensable as a deoxidizing element during refining. However, if the Mn content is less than 0.2 wt.%, Desired effects cannot be obtained for the above-described effects. On the other hand, when the Mn content exceeds 2 wt.%, A pattern is generated on the surface of the weld bead. Therefore, Mn
The content should be limited to the range of 0.2 to 2 wt.%.

(4) Chromium (Cr): Cr is an element indispensable for imparting corrosion resistance to a stainless steel sheet. However, if the Cr content is less than 11 wt.%, Desired effects cannot be obtained in the above-described operation. On the other hand, if the Cr content exceeds 30 wt.%, The effect is saturated and uneconomical. Therefore, Cr
The content should be limited to the range of 11-30 wt.%.

(5) Nickel (Ni): Ni is an element that limits the structure of stainless steel. Therefore, it is added as needed depending on the use of the steel sheet. If the Ni content is less than 6 wt.%, The austenite phase cannot be stabilized. on the other hand,
If the Ni content exceeds 22 wt.%, The effect will be saturated and
It becomes uneconomical. Therefore, the amount when Ni is contained is 6 to
It should be limited to the range of 22 wt.%.

(6) Calcium (Ca), magnesium (M
g): Ca and Mg have the effect of fixing O and S in steel and removing the adverse effects of O and S at a high temperature such as a molten pool. Therefore, it is necessary to contain at least one of Ca and Mg. However, if the respective contents of Ca and / or Mg are less than 0.0004 wt.%, Desired effects cannot be obtained in the above-mentioned effects. On the other hand, if the respective contents of Ca and / or Mg exceed 0.0065 wt.%, A large amount of slag covers the bead surface during welding, causing a problem that the normal generation of a welding arc is hindered. Therefore,
Each content of at least one of Ca and Mg is 0.0004 to 0.00
It should be limited to 65 wt.%.

(7) Oxygen (0), sulfur (S): O content is 0.009 wt.% From the viewpoint of mechanical properties and corrosion resistance of the welded joint.
Hereinafter, the S content should be limited to 0.008 wt.% Or less.

However, when non-filler fillet welding is performed on the overlapped portion of two stainless steel sheets, the action of O and S in the steel causes the bead shape and welding defect to be reduced as described below. The occurrence is determined. The upper steel plate in the overlapped part is melted by the arc heat,
Hot water with a certain amount of heat is generated. The hot water flows toward the lower steel plate due to gravity and arc pressure.

When the fluidity of the hot water is good, the hot water flows far away on the lower steel plate side and solidifies, and the surface bead is determined. In this case, the toe angle becomes relatively small. At the same time, the fusion shape on the lower steel plate side is determined.
However, in the case of hot water having good fluidity, since the hot water spreads widely, the amount of heat is dispersed, so that the lower steel plate becomes shallow and the throat thickness becomes relatively small. Furthermore, when the fluidity of the hot water becomes large, the hot water flows too much, resulting in undercut. When the arc force is excessive, defects such as holes and scale-like swelling are generated in the weld bead.

On the other hand, if the fluidity of the hot water is poor, the hot water does not excessively flow on the lower steel plate side, and the molten water deepens. For this reason, the bead toe angle becomes excessively large and the throat thickness becomes relatively large. In this case, no undercut defect occurs, but if the fluidity becomes extremely poor, the lower steel sheet does not wet the hot water, and defects such as perforations and scale-like swelling occur.

The fluidity of the above hot water increases when the surface tension and viscosity are low, but the corrosion resistance, workability,
As long as the mechanical properties are maintained, O and S in the steel are the main elements that change the fluidity. That is, when the content of O and S in the steel is large, the fluidity of the hot water increases.

From many test results by the present inventors, the above action depends on “0+ (1/2) × S”, and “0+ (1/2) × S”
It was found that the most appropriate S value was in the range of 0.0045 to 0.012 wt.%. Therefore, in the present invention,
The 0 content is limited to 0.009 wt.% Or less, the S content is limited to 0.008 wt.% Or less, and the value of “0+ (1/2) × S” is set to 0.0045 to 0.
Limited to the range of 012 wt.%.

[0027]

Next, the present invention will be described with reference to examples and comparative examples. As shown in Table 1, having a chemical composition within the range of the present invention, a thickness of 2.0 mm and a surface finish No. 2B
No.1 stainless steel sheet (hereinafter referred to as the specimen of the present invention)
~ 14 were prepared.

[0028]

[Table 1]

TIG welding was performed on the overlapped end portions shown in FIG. 1 of each of the two test samples Nos. 1 to 14 under the following conditions. Welding current: 110 A, arc length: 1 mm, welding speed: 160 mm / min, target position: 1.5 mm from upper plate edge, tacking interval: 20 mm, welding length: 500 mm, shielding gas: Ar, 10 liters / min.

For comparison, a stainless steel sheet (hereinafter referred to as a comparative specimen) No. 1 having the same thickness as described above, in which at least one of the chemical components is out of the scope of the present invention, also shown in Table 1. To 8 were prepared, and TIG welding was performed on each of the two sheets under the same conditions as described above.

With respect to each of the specimen of the present invention and the comparative specimen subjected to TIG welding as described above, their bead shapes (throat thickness and toe angle), welding defects (undercut and perforated, scales). Occurrence) and arc stability were examined as follows. Throat thickness: Check whether the throat thickness is 70% or more of the specimen thickness (2mm).
And less than 70% were rejected (x). Toe angle: It was checked whether or not the toe angle was 40 ° or less. A case where the toe angle was 40 ° or less was regarded as pass (○ mark), and a case where it exceeded 40 ° was rejected (marked with ×). Undercut: The presence or absence of the occurrence of undercut was checked. If no undercut occurred, it was judged as pass (合格), and if it occurred, it was rejected (x). Perforated / scaled: The presence or absence of perforated and scale-shaped swelling was examined. If none of them was generated, it was regarded as pass (印), and if it was generated, it was rejected (×).

Table 2 shows the results of investigation on the bead shape, the presence or absence of welding defects, and the arc stability of each specimen.

[0033]

[Table 2]

As is clear from Tables 1 and 2, the comparative sample No. which does not contain Ca and / or Mg and has a small "0+ (1/2) × S" value outside the range of the present invention. .1, No.2 and No.4 had bad toe angles. Comparative specimens No. 3 and No. 5, which did not contain Ca and / or Mg, had poor throat thickness and generated undercuts and welding defects such as holes and scales.

It contains no Ca and / or Mg and contains “0+
Comparative Sample No. 6 having a value of (1/2) × S ”outside the range of the present invention was small in the throat thickness and the toe angle. The content of Ca is large outside the range of the present invention and "0+ (1/2) × S"
The comparative specimen No. 7 having a large value outside the range of the present invention had poor arc stability. Then, Comparative Sample No. 8 containing no Ca and / or Mg had a poor throat thickness and undercut occurred.

On the other hand, all of the test specimens Nos. 1 to 14 of the present invention had the throat thickness and the toe angle within the target values.
No undercut, perforation, scale, etc. were generated in the bead portion, the arc stability was good, the bead shape was excellent, and no welding defects were generated.

[0037]

As described above, according to the present invention,
When performing non-filler fillet welding on stainless steel sheets with a thickness of 3 mm or less, the proper bead shape is maintained,
No undercut and defects such as perforations and scale-like bumps on the surface of the weld bead.
An industrially superior effect of obtaining a stainless steel sheet having excellent IG weldability is provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a throat thickness and a toe angle when fillet welding is performed on a superposed end of a thin steel plate.

[Explanation of symbols]

 1 thin steel sheet, 2 thin steel sheet, 3 weld bead, d throat thickness, θ toe angle.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-162750 (JP, A) JP-A-63-60260 (JP, A) JP-A-54-71026 (JP, A) JP-A-4- 143255 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 302 C22C 38/18 C22C 38/40

Claims (2)

(57) [Claims] 1. Carbon (C): 0.11 wt.% Or less, silicon (Si): 0.2-1 wt.%, Manganese (Mn): 0.2-2 wt.%, Chromium (Cr): 11-30 wt.%. % Oxygen (O): 0.009 wt.% Or less, Sulfur (S): 0.008 wt.% Or less, and at least one element selected from the group consisting of: calcium (Ca): 0.0004 to 0.0065 wt.%, Magnesium (Mg): 0.0004 to 0.0065 wt.%, Remaining: substantially composed of iron (Fe), and satisfies the following formula: 0.0045 wt.% ≦ 0 + (1/2) × S ≦ 0.012 wt.% A stainless steel sheet excellent in TIG weldability, characterized in that: 2. Carbon (C): 0.11 wt.% Or less, silicon (Si): 0.2 to 1 wt.%, Manganese (Mn): 0.2 to 2 wt.%, Nickel (Ni): 6 to 22 wt. %, Chromium (Cr): 11-30 wt.% Oxygen (O): 0.009 wt.% Or less, Sulfur (S): 0.008 wt.% Or less, and at least one element selected from the group consisting of calcium (Ca): 0.0004 to 0.0065 wt.%, Magnesium (Mg): 0.0004 to 0.0065 wt.%, Remaining: substantially iron (Fe), and the following formula: 0.0045 wt.% ≦ 0 + (1 / 2) A stainless steel sheet excellent in TIG weldability, satisfying the condition of × S ≦ 0.012 wt.%.