JP2000312988A - Ht590 class refractory steel submerge arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a welding part with high temperature elongation and excellent toughness even with large heat input one layer welding by using a specific composition of wire and flux, restricting B volume shifted from the flux, the wire and a steel plate into the welding metal, and appropriating the wire component and the flux base level. SOLUTION: HT590 refractory steel including 0.6-1.2 wt.% Mo and 0.001-0.05 wt.% Nb is welded by combining the flux for satisfying formulae I-VIII and the wire which satisfies formulae III-VIII and includes 0.01-0.13 wt.% C, 0.005-0.15 wt.% Si, 1.2-2.2 wt.% Mn, 0.60 wt.% or less Mo, 0.05 wt.% or less Nb, 0.02 wt.% or less V, 0.03 wt.% or less Ti, 0.0005 wt.% or less B and the balance of Fe. In this case, in the formula II, each component means the content in the flux. In the formulae IV and VI, [MO]W, [MO]P, and [Mo]F mean Mo contents in the wire, the base material and the flux respectively, which can be applied similarly to B and B2O3. Also, aW, aP, aF mean shifted rates of Mo and B to the welding metal in the wire, the base material, and the flux respectively. In the formula VIII, each component means the content in the welding metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a submerged arc welding method for HT590 grade steel sheet (hereinafter referred to as HT590 grade fire resistant steel) having excellent fire resistance used for various structures in the field of construction and bridges. Heat input of 10 to 50 kJ / m in square joint welding of box columns
The present invention relates to a submerged arc welding method which is excellent in proof stress at 600 ° C. and high-temperature elongation and obtains good toughness when one layer is welded at m.

[0002]

2. Description of the Related Art Conventionally, as a refractory steel, a normal temperature strength of 400 is used.
HT400 class ~520N / mm ^2, HT490 grade, H
T520 class fire resistant steel and weather resistant fire resistant steel have been put to practical use, and various welding materials used for them have been put into practical use. As submerged arc welding, for example, Japanese Patent Publication No. 5-025598
Submerged arc welding wire and flux for refractory steel are proposed in No.2, and the weld metal has obtained high temperature proof strength, proper room temperature strength and good toughness. Further, JP-A-3-174978 discloses a refractory steel and a weather-resistant refractory steel having excellent toughness and high-temperature ductility without impairing properties such as high temperature proof stress at 600 ° C. and weather resistance at ordinary temperature, and having improved creep rupture life. A submerged arc welding method has been proposed.

Further, the present inventors have disclosed in Japanese Patent Application No. 8-58246.
Al-B refractory steel and Mo
-As a submerged arc welding method that can be used for Nb-based refractory steel, a flux with an appropriate basicity is used, and the amount of Mo, B transferred from the flux, wire and steel plate into the weld metal, the amount of carbon in the weld metal, and the like are optimized. A submerged arc welding method that secures proof stress and elongation and maintains tensile strength and toughness appropriately was proposed.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Publication No. 5-0
The submerged arc welding method using a submerged arc welding wire and a flux for refractory steel proposed in No. 25598 focuses on high-temperature strength as a high-temperature property, but does not sufficiently consider elongation at high temperature. .

Japanese Patent Application Laid-Open No. 3-174978 proposes a submerged arc welding method for fire-resistant steel and weather-resistant fire-resistant steel in which elongation is taken into consideration in addition to proof stress at high temperatures. In this case, the refractory steel was mixed with Mo or Nb.
It was a 0-520 N / mm ² class fire-resistant steel, and Ni and Cu were further added to the weather-resistant fire-resistant steel. The welding materials for this are those which have good performance by limiting B and Ti.

Further, in Japanese Patent Application No. 8-58246, the inventors of the present invention, as a welding material corresponding to a boron-treated steel sheet in which Mo and Nb are reduced, Al and B are increased, and the Mo amount of the welding material and the welding amount are determined. The Ceq of the metal and the basicity of the flux were specified to obtain good high-temperature elongation and toughness. This is for HT400 to HT520 class refractory steel, and the maximum strength at room temperature is about 660 N / mm ² . No further strength is considered. However, after that, HT590 N / mm ² refractory steel containing Mo or Mo and Nb was developed as a refractory steel having higher strength, and this large heat input single-layer submerged arc welding method is disclosed in JP-A-3-174978. In the welding material obtained, good high-temperature tensile properties cannot always be obtained in welding with a large base material dilution ratio, such as box column corner welding.

Further, in the large welding base material dilution rate, such as welding materials proposed in Japanese Patent Application No. 8-58246 is box columns corner weld, the weld metal of a high strength such as HT590N / mm ^2, Good characteristics are not always obtained.
That is, in the large heat input single-layer submerged arc welding method, the base metal dilution ratio is about 40 to 60% larger than that of the metal components which migrate from the base metal to the weld metal, such as Mo, Mn, and Si, high temperature proof stress, normal temperature strength, and high temperature. It was difficult to satisfy all the characteristics because elements affecting elongation and toughness deviated from appropriate values.

[0008] Therefore, the newly developed HT590
There has been an urgent need to develop a high heat input single-layer submerged arc welding material such as a box column joint used for N / mm ² refractory steel and a welding method.

[0009]

Means for Solving the Problems The present inventors have solved the above-mentioned problems, and have found that Mo: 0.6-1.2%, N
b: A submerged arc welding method for welding HT590 grade refractory steel containing 0.001 to 0.05%, which satisfies the following formulas (1), (2), (3) and (4). The flux for submerged arc welding satisfies the following formulas (2), (3) and (4), and C:
0.01-0.13%, Si: 0.005-0.15
%, Mn: 1.2 to 2.2%, Mo: 0.60% or less,
Nb: 0.05% or less, V: 0.02% or less, Ti:
A submerged arc welding method characterized in that it is performed in combination with a submerged arc welding wire containing 0.03% or less and B: 0.0005% or less, with the balance being Fe and unavoidable impurities.

0.55 ≦ Bn ≦ 1.40 (1) where Bn = (0.108CaO + 0.068MnO + 0.100MgO + 0.078CaF ₂ ) / (0.105SiO ₂ + 0.002Al ₂ O ₃ + 0.080TiO ₂ )

[Mo] _C ≧ 0.32 (2) where [Mo] _C = α _W [Mo] W + α _P [Mo] P + α _F (Mo) _F

[B] C ≦ 0.0010 (3) where [B] _C = α _W [B] W + α _P [B] P + α _F (B ₂ O ₃ ) _F ,

0.37 ≦ Ceq ≦ 0.49 (4) where Ceq = C + Si / 24 + Mn / 6 + (Mo + Nb) / 5 + 5B

However, in formula (1), CaO, MnO, Mg
O, CaF_Two, SiO_Two, Al_TwoO_Three, TiO_Two:It
CaO, MnO, MgO, Ca in each flux
F_Two, SiO_Two, Al_TwoO_Three, TiO_TwoContent (weight
%), [Mo] in equations (2) and (3)_W: Mo in the wire
Content (% by weight), [Mo] _P: Mo content in base metal
(% By weight), (Mo)_F: Mo content in flux
(% By weight), [B]_w: B content in wire (weight
%), [B]_p: B content (% by weight) in base material, (B_Two
O_Three)_F: B in flux_TwoO_ThreeContent (% by weight) α_w: Transfer of Mo and B in wire into weld metal
Rate, α_p: Transfer of Mo and B in base metal into weld metal
Rate, α_F: Mo and B in flux to weld metal
It is the transition rate._w= 0.37,
α_p= 0.43, α_F= 0.20, plate thickness more than 28 ~ 40m
m is α_w= 0.42, α_p= 0.48, α _F= 0.10,
Plate thickness of 40 to 55 mm is α_w= 0.45, α_p= 0.5
0, α_F= 0.05, C, Si, Mn, M in equation (4)
o, Nb and B are respectively C, Si, M in the weld metal.
Content of n, Mo, Nb and B (% by weight).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various studies in order to achieve the above-mentioned object, and have used a wire and a flux having an appropriate composition to regulate the amount of B transferred from the flux, the wire and the steel sheet into the weld metal, and We have found a welding method that ensures high-temperature elongation by optimizing the carbon equivalent of the weld metal and that maintains good tensile strength and toughness by optimizing wire components and flux basicity.

First, the steel material to be welded to which the present invention is applied is as follows: Mo: 0.6 to 1.2%, Nb: 0.001.
HT590 grade refractory steel which has been improved in strength from refractory steel generally used conventionally by containing up to 0.05%. The overall components of this steel material were converted to the above Mo, Nb
In addition, C: 0.05-0.0% by weight.
9%, Si: 0.25 to 0.35%, Mn: 1.2 to
1.7%, Mo: 0.6 to 1.2%, Nb: 0.001
-0.05%, V: 0.05% or less, Ti: 0.02%
Hereinafter, it is common to contain B: 0.0010% or less, with the balance being Fe and unavoidable impurities.

In the previous welding of HT490 to HT520 grade refractory steel, in order to obtain the proof stress of the weld metal at 600 ° C., it was proposed that the value be specified by a specific formula representing a scale of the amount of Mo in the weld metal. If the present invention is considered in the HT590 refractory steel of interest, if 70% of the standard value 440 N / mm ² of the normal strength guaranteeing at 600 ° C., specifications of strength becomes 308N / mm ² or more. In order to obtain this proof stress, as shown in the graph of FIG. 1, the specific formula of the steel sheet, wire and flux indicating the scale of the amount of Mo in the weld metal [M
o] The _c value needs to be 0.33 or more.

Next, it was proposed that in the previous welding of HT490 to HT520 refractory steel, an appropriate amount of proeutectoid ferrite was left in the microstructure of the weld metal. That is, the proeutectoid ferrite must be left in order to secure an elongation of 18% or more in a tensile test at 600 ° C., while it is necessary to suppress as much as possible in order to ensure good toughness. Therefore, in order to achieve both, a specific expression for the amount of B transferred from the flux, wire, and steel plate to the weld metal was specified, and an appropriate range was specified by an expression related to Ceq. Since the room temperature strength of the weld metal is 490-660 N / mm ² , it is relatively easy to leave proeutectoid ferrite in the weld metal.

However, the HT5 targeted by the present invention
In 90 refractory steel, 0.6 to 1.2% of Mo is added to the steel sheet, and if this steel sheet is subjected to high heat input single-layer welding such as box column welding, the base metal dilution ratio is about 45%. It becomes 0.27-0.57 only at the dilution from the base material and a maximum of 0.5.
About 6% of Mo transfers to the weld metal. Mo of weld metal
When the content increases, the amount of pro-eutectoid ferrite at the grain boundaries decreases in the microstructure. In such welding where a large amount of Mo is transferred from the base metal into the weld metal and the proeutectoid ferrite is liable to decrease, the amount of B is strictly controlled, or the transformation temperature is increased by increasing the weld metal to high oxygen and the proeutectoid ferrite is increased. However, the composition must be easy to grow.

In welding HT590 steel, the B content of the weld metal is not added except that it is inevitable from impurities in the flux, wire and steel plate, and the flux has a low basicity. Further, it is necessary to regulate Ceq within an appropriate range so that the strength is not excessive.

B is 0.0006% for steel plate and wire
In the bond flux, the flux inevitably contains about 0.03% or less as B ₂ O ₃ from the normally used magnesia clinker. B is not intentionally added to the weld metal, and is defined as 0.0010 or less using a specific formula [B] _c value as a measure of the amount of B transferred to the weld metal.

Further, Bn = (0.108 CaO + 0.068 MnO + 0.08) is a measure for supplying oxygen to the weld metal.
100MgO + 0.078CaF ₂ ) / (0.105S
The basicity represented by (iO ₂ + 0.002Al ₂ O ₃ + 0.080TiO ₂ ) is set to 0.55 ≦ Bn ≦ 1.40. In addition, the Ceq is restricted to 0.37% or more in order to secure the strength at room temperature of 590 N / mm ² or more.

Further, the present invention will be described in detail. The present inventors first found that the [Mo] _C content and the 6
The relationship with the proof stress at 00 ° C. (hereinafter referred to as YP600) was determined. It can be seen that YP600 increases as the [Mo] _c amount increases. [Mo] _c is M in the weld metal
o indicates a measure of the amount of HT400 to HT52
In the case of 0-grade refractory steel, the present inventors have [Mo] _c as [Mo] _c .
It was proposed that [Mo] _c ≧ 8.5 to ensure YP600 ≧ 235 N / mm ² using a calculated value of _c = 43 [Mo] _w +55 [Mo] _p +18 (Mo) _F.

In the HT590 class refractory steel to which the present invention is applied, the standard YP ≧ 440 N / mm ² of SM590 steel is used, whereas the YP600 ≧ 308 (= 440 × 0.
7) N / mm ² is required. Here, instead of the above formula, the base material dilution ratio having a difference depending on the plate thickness is considered as the scale [Mo] _c , that is, the specific formula [Mo] _c = α _w [Mo] _w +
α _p [Mo] _p + α _F (Mo) _F was obtained. To achieve the target value, [Mo] _c needs to be 0.33 or more. Here, [Mo] _W : Mo content (% by weight) in the wire,
[Mo] _P : Mo content (% by weight) in base material, (Mo)
_F : Mo content (% by weight) in the flux
α _w : Transfer rate of Mo in the wire into the weld metal, α _p :
Transfer rate of Mo in the base metal into the weld metal, α _F : Transfer rate of Mo in the flux to the weld metal, plate thickness 19 to 2
For 8 mm, α _w = 0.37, α _p = 0.43, α _F = 0.
20, when the plate thickness exceeds 28 to 40 mm, α _w = 0.42, α _p =
0.48, α _F = 0.10, plate thickness more than 40 to 55 mm is α
_w = 0.45, α _p = 0.50, α _F = 0.05.

Next, the elongation of the tensile test at 600 ° C. is secured.
HT400 to HT520 grade refractory steel
First, the present inventors used a measure of the B content in the weld metal.
[B] c = 4300 [B]_w+5500 [B]_p +12
0 (B_TwoO_Three)_FWas proposed for HT590 steel.
Base material dilution ratio that varies depending on
[B] _c That is, [B]_c = Α_w [B]_w + Α_p[B]_p
 + Α_F(B_TwoO_Three)_F Using [B]_c ≦ 0.001
0 was required. [B]_w : In the wire
B content (% by weight), [B]_p : B content in base material (weight
%), (B_TwoO_Three)_F: B in flux_TwoO_ThreeContained
Amount (% by weight), α_w : B in the wire into the weld metal
Transition rate, α_p : Transfer rate of B in the base metal into the weld metal, α
_F: Transfer rate of B in the flux to the weld metal
19-28mm thickness is α_w = 0.37, α_p= 0.43,
α_F= 0.20, plate thickness 28 to 40 mm is α_w = 0.4
2, α_p = 0.48, α_F= 0.10, plate thickness more than 40 ~ 5
5mm is α_w = 0.45, α_p = 0.50, α_F= 0.
05.

Furthermore, in order to secure elongation in a tensile test at 600 ° C., it is necessary to reduce the basicity of the flux in order to generate pro-eutectoid ferrite at grain boundaries. Flux basicity is a measure of the amount of oxygen in the weld metal. That is, as the basicity decreases, the amount of oxygen in the weld metal increases, and pro-eutectoid ferrite at the grain boundaries is generated, thereby improving the elongation in the tensile test at 600 ° C. Now, as basicity, Bn = (0.1
08CaO + 0.068MnO + 0.10MgO + 0.08
078CaF ₂ ) / (0.105SiO ₂ + 0.002A)
l ₂ O ₃ +0.080 TiO ₂ )
In order to ensure good elongation in a 0 ° C. tensile test, Bn ≦
1.40 is required. On the other hand, if Bn is less than 0.55, the toughness deteriorates. That is, 0.55 ≦ Bn ≦ 1.40.

[0027] In addition, in order to keep the tensile strength at room temperature (hereinafter referred to as TS _RT) in an appropriate range it is necessary to limit the scale of hardening. That is, it is necessary that Ceq ≦ 0.49%. In addition, in order to obtain 590 N / mm ² or more, Ceq ≧
0.37%. That is, 0.37 ≦ Ceq ≦ 0.49%
It is.

The components of the submerged arc welding wire used in the present invention will be described below. C is necessary for ensuring the room temperature strength and for exhibiting the effect of adding Mo and Nb, and the lower limit is 0.01%. In addition, 0.13%
Exceeding the temperature increases the susceptibility to hot cracking and deteriorates toughness.

Si needs to be added in an amount of 0.005% or more as a deoxidizing element, but if it exceeds 0.15%, the toughness of the weld metal deteriorates. Mn is indispensable for securing strength and toughness and needs to be added in an amount of 1.2% or more.
If it exceeds 2.2%, the hot cracking susceptibility increases and the toughness deteriorates.

Mo and Nb are necessary to ensure a sufficient high-temperature proof stress, but the lower limits are not particularly defined since they can be added from the flux. On the other hand, when Mo and Nb become excessive, the room temperature strength becomes too high and the toughness is deteriorated. Therefore, the addition amounts of Mo are 0.60% or less and Nb is 0.05% or less.
It must be:

V is necessary for securing the strength at room temperature, but if the wire content exceeds 0.02%, the toughness deteriorates. Ti
Is a deoxidizing element and an important element for securing toughness, and it is desirable to add 0.001% or more. However, if added excessively, the high-temperature elongation of the weld metal is deteriorated. is there.

B is important for securing the elongation at a high temperature of 600 ° C., and it is necessary not to add B intentionally and to regulate it to 0.0005% or less, which is an unavoidable amount from impurities. Also,
In the wire of the present invention, other than the components specified above, Ni
1% or less, Cr is 0.5% or less, Cu is 0.5% or less including plating, P is 0.025% or less, and S is 0.015%.
The following are acceptable. The rest is Fe and inevitable impurities.

[0033]

EXAMPLES The effects of the present invention will be more specifically shown by the following examples. The steel plates used were four types of P1 to P4 shown in Table 1, and the wires used were three types of compositions W1 to W3 shown in Table 2. The flux prepared six types of bond flux of F1-F6 of Table 3. Among them, F1 to F4 are fluxes of the present invention, and F5 and F6 are fluxes of comparative examples for clarifying the effect of the present invention.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

The groove shape shown in FIG. 2A is a Y-shaped groove,
(B) is a bevel groove destination, theta ₁ is included angle 35 ° of the groove shape of (a), T ₁ is the thickness 40mm or 45 mm, r
₁ is a root face of 2 mm, and t ₁ is a backing metal of 25 mm. In addition, θ ₂ of the groove shape shown in FIG.
T ₂ is a plate thickness of 25 mm, r ₂ is a root face of 2 mm, t
₂ is a backing metal of 25 mm. Using the above three types of specimens, submerged arc welding using two electrodes was performed without performing preheating under the welding conditions C1 to C3 shown in Table 4.

[0038]

[Table 4]

After completion of welding, one JIS A1 tensile test piece, three JIS No. V notch Charpy test pieces, and a high-temperature tensile test piece (6 mm
(Diameter) One sample and an analysis sample were collected and tested. The results are shown in Tables 5, 6, and 7. In Table 6, symbols 1 to 12 are examples of the present invention, and symbols 13 to 21 are comparative examples for clarifying the effects of the present invention. As a result, Examples 1 to 12 of the present invention showed TS _RT , YP600, E
Both l600 and vE _-5 ° C showed good values and no problem.

[0040]

[Table 5]

[0041]

[Table 6]

[0042]

[Table 7]

Thirteen of the comparative examples had lower toughness because the lower limit of the value of equation (1) was broken. Further, among the comparative examples, El600 deteriorated because 14 exceeded the upper limit of the value of the expression (1). Further, among the comparative examples, 15 exceeded the upper limit of the value (3), and thus El
600 has deteriorated and the lower limit of the value of equation (2) has been broken, so YP600
Has deteriorated.

In 16 of the comparative examples, the strength was insufficient because the lower limit of the value of the equation (4) was divided, and Y was smaller than the lower limit of the value of the equation (2).
P600 has deteriorated. In addition, YP600 of 17 of the comparative examples was deteriorated because the value of equation (2) was below the lower limit. In the comparative example 18, YP600 was obtained because the value of the equation (2) was lower than the lower limit.
Has deteriorated.

In Comparative Examples 19, El600 deteriorated because the value of the equation (3) exceeded the upper limit. 20 of the comparative examples
The value of equation (3) exceeded the upper limit, so El600 deteriorated. Further, among the comparative examples, 21 exceeded the upper limit of the value of the expression (4), so that the _TSRT was excessively large.

[0046]

According to the present invention as described above,
As shown in the examples, in the submerged arc welding method for HT590 class refractory steel, the welding heat input is 10 to 40 kJ / m.
In the case of further welding at m, a welded portion having excellent proof stress at 600 ° C. and high-temperature elongation and good toughness can be obtained, which greatly contributes to welding of a large structure.

[Brief description of the drawings]

FIG. 1 [Mo] _{c of} weld metal and proof stress at 600 ° C. (YP6
00)

FIGS. 2A and 2B are cross-sectional views each showing a groove shape of a welding test plate used in Examples.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Noriyuki Ohama 20-1 Shintomi, Futtsu City, Chiba Prefecture Nippon Steel Corporation Technology Development Division (72) Inventor Naoaki Matsuya 20-1 Shintomi, Futtsu City, Chiba Prefecture New Japan F-term in the Technology Development Division of Steel Corporation (reference) 4E001 AA03 BB05 CA04 EA05 EA07 4E084 AA02 AA03 AA06 AA07 AA08 AA11 AA12 AA20 BA09 CA02 DA16 GA05 HA04

Claims (1)

[Claims] 1. Mo: 0.6 to 1.2%, Nb: 0.0
Welding HT590 class refractory steel containing 01-0.05%
Submerged arc welding method for performing
Sub-matrix that satisfies (1), (2), (3) and (4)
Flux for arc welding and the following formula
(2), (3) and (4) are satisfied, and C: 0.
01-0.13%, Si: 0.005-0.15%, M
n: 1.2 to 2.2%, Mo: 0.60% or less, Nb:
0.05% or less, V: 0.02% or less, Ti: 0.03
%, B: 0.0005% or less, with the balance being Fe
And submerged arc welding wire consisting of unavoidable impurities
Submerger that is performed in combination with
Welding method. 0.55 ≦ Bn ≦ 1.40 (1) where Bn = (0.108CaO + 0.068MnO + 0.100MgO + 0.078CaF)_Two) / (0.105SiO_Two + 0.002Al_TwoO_Three+ 0.080TiO_Two) [Mo]_C≧ 0.32 (2) where [Mo]_C= Α_W[Mo]_W + Α_P[Mo]_P+ Α_F(Mo)_F [B] C ≦ 0.0010 (3) where [B]_C= Α_W[B]_W+ Α_P[B]_P+ Α_F(B_TwoO_Three)_F0.37 ≦ Ceq ≦ 0.49 (4) Here, Ceq = C + Si / 24 + Mn / 6 + (Mo + Nb) / 5 + 5B where, in the formula (1), CaO, MnO, MgO, CaF_Two,
SiO_Two, Al_TwoO_Three, TiO_Two: Each flux
CaO, MnO, MgO, CaF in_Two, SiO_Two, A
l_TwoO_Three, TiO_Two(% By weight), [Mo] in formulas (2) and (3)_W: Mo content in wire
(% By weight), [Mo] _P: Mo content (weight) in base metal
%), (Mo)_F: Mo content in flux (weight
%), [B]_w: B content (% by weight) in wire,
[B]_p: B content (% by weight) in base material, (B_TwoO_Three)
_F: B in flux_TwoO_ThreeContent (% by weight) α_w: Transfer of Mo and B in wire into weld metal
Rate, α_p: Transfer of Mo and B in base metal into weld metal
Rate, α_F: Mo and B in flux to weld metal
It is the transition rate._w= 0.37,
α_p= 0.43, α_F= 0.20, plate thickness more than 28 ~ 40m
m is α_w= 0.42, α_p= 0.48, α _F= 0.10,
Plate thickness of 40 to 55 mm is α_w= 0.45, α_p= 0.5
0, α_F= 0.05, C, Si, Mn, Mo, Nb and B in the formula (4)
C, Si, Mn, Mo, Nb and B in the weld metal respectively
Content (% by weight).