JPS60181254A - High tension steel having superior resistance to cracking due to hot dip galvanizing - Google Patents

Abstract

PURPOSE:To obtain a high tension steel having superior resistance to cracking due to hot dip galvanizing by adding specified percentages of C, Si, Mn, Zr, sol. Al, Nb and V to Fe. CONSTITUTION:A high tension steel consisting of, by weight, 0.02-0.15% C, 0.10-0.50% Si, 0.80-2.00% Mn, 0.005-0.050% Zr, 0.005-0.100% sol. Al, 0.01- 0.10% Nb and/or V and the balance Fe with inevitable impurities and satisfying an equation 265-293C-21Si-96Mn-370V-35Al+584Zr>=40 is manufactured. The GOS resistance of the high tension steel for a welded structure having >=60kgf/mm.<2> tensile strength is advantageously improved.

Description

[Detailed description of the invention] Technical Field Welded structures, particularly welding heat effects, in high-tensile steel, which are processed and assembled into welded structures and then immersed in a hot-dip galvanizing bath to be galvanized and put into service. Department (HA
The technical content described in this specification regarding the reduction of cracking susceptibility (referred to as GOS) due to hot-dip galvanizing, which tends to occur in steels with a tensile strength of a o kg f
4. The present invention relates to a new proposal for a development result that aims to significantly improve IGOS properties without hindering productivity for steel with a tensile strength of 1'' or more.

BACKGROUND ART Hot-dip galvanizing treatment is useful from the viewpoint of rust prevention or aesthetic appearance, particularly paintability, of steel structures, and has been widely used in the past. In recent years, due to the strong demand for larger and lighter steel structures, there has been a growing trend to increase the strength of steel materials for welded structures that should be subjected to the above-mentioned plating treatment. Actually, that is especially 60 kyf.
/m, when steel materials exceeding mk are subjected to galvanizing treatment by immersion in a molten zinc bath after welding assembly, so-called plating cracking in the HAZ or liquid metal embrittlement occurs. The tendency for frequent occurrence of grain boundary cracking, called so-called intergranular cracking, is especially remarkable.

This is because as welded structures become larger and more complex, the residual stress that accompanies welding becomes more significant for materials with higher tensile strength, which is one of the factors that promotes the above-mentioned cracking. Because it will be.

Therefore, in order to reduce the GO8Q resistance, consideration must be given to the welding conditions and immersion conditions in order to reduce the residual stress during welding and the thermal stress during immersion in the hot-dip galvanizing bath. Although annealing treatment is also carried out,
This cannot be said to be a fundamental solution, as it impairs economic efficiency or the properties of the base material, which is why it is necessary to improve the steel material itself.

Prior art and its problems Regarding considerations regarding the composition of welded structural steel that requires GO8 resistance, see JP-A-57-104656 and JP-A-57-104656.
In both publications No. 8-84959, 0.005' to 0
．． 05 wt % (hereinafter simply referred to as a section) of T1 alone or 0.005 to 0.08% Ti, 0.02 to 0.09
It has been disclosed that the Goa resistance can be improved by the combined inclusion of %V, but as is well known, such Ti-containing steels suffer from I"" on the casting surface when using the continuous casting method. Surface defects called so-called star cracks occur frequently, and not only is there a disadvantage in the process that requires surface treatment prior to hot rolling, but the problem remains that the yield rate inevitably decreases due to such treatment. .

Purpose of the Invention The present invention advantageously improves the GO8 resistance of high tensile strength welded structural steels having a tensile strength of 60 kgf/I 2nd or higher, especially in a component composition that does not have the disadvantages associated with the addition of T1. This is the purpose of ! (8) Structure of the invention The above object is advantageously achieved by adjusting the ingredients based on the following matters.

That is, O: 0.02 to 0.15 chi, si:
o, io~50.50%, Mn: 0.80~2.0
0%, Zr: 0.005-0.05%, sol
Ajt: 0.005 to 0.100% and one or two of ■ or Nb 0. It contains 2.10% of O2N in the relationship of the following formula 2% (1), and the remainder is the composition of T8 and impurity elements.

In practical development of this invention, 0.05 to 1.0
Within the range of 0%, Ni, Ou, Or and MOli are used as steel toughening components, and 0,000%
5 to 0.0040% Bt" reinforcing component due to hardenability enhancement, and further 0.0005 to 0.00% Oe
It is more desirable to select 2... from the above groups and add them to the steel ingredients as injection improving ingredients by suppressing grain growth or controlling inclusion morphology. The influence of the ingredients on the GO8 resistance can be expressed by the following formula.

265-2980-218i-96Mn-870V-
410Nb-851-18Ni-1280u-940
r-90MO-2454B+584Zr+142906
≧40 (2) When O is contained in a relatively large amount within the above range, it is more desirable to combine it with Ni.

The key point of this invention is that in the component composition that can ensure a tensile strength level exceeding 60 kgZ-, ZrW in a range of 0.005 to 0.05% and GO8 resistance are particularly important.
This comes from the knowledge that its inclusion as a sex-improving ingredient is compatible with the intended purpose. 15 By the way, regarding Zr, in the former prior art, as an element that controls the form of inclusions, T1 is used at 0.15% t as long as it does not impair cleanliness.
However, there is no mention of the direct influence or contribution of Zr on the GO8 resistance mentioned above.

In this invention, the technical basis for limiting the composition of the AASG high tensile strength steel is as follows.

0: o, og ~ 0.15chi0bata It is a component that is most useful for increasing the strength of steel, and if it is less than 0.024, the effect is not expected -1
If the content exceeds 0.15%, weldability deteriorates and the content is not suitable for the purpose, so the content should be in the range of 0.02 to 0.15%.

Si: 0.10 to 0.50% Si is required for deoxidizing effect and contribution to strength, so 0.10% or more is required, but if 0.5%'ij is added, It has a negative effect on GO8 resistance, and low temperature dust! 1.
0.1θ to 0.50% as it tends to deteriorate
shall be.

Mn: 0.80-2.00 S Hn also requires a minimum of 0.8% to ensure strength, -
If it exceeds 2.00%, it will not only impair ttGO8 property but also basic performance such as weldability and workability, so 0.8 to 2.00%
limited to the range of

Zr: 0.005 to 0.05% Zr, according to the present invention, ensures GO8 resistance under a bow tension of 6okyf9 or higher without the disadvantages mentioned in the explanation of the prior art. It is an important component that is useful for improving GO8 resistance when the content is 0.005% or more.
．． If the content exceeds 0.05%, the cleanliness of the steel will be affected and the mechanical properties, especially the dust injection properties, will be deteriorated.

5olAJ: 0.005 to 0.100% AJ is required to be 9.005% or more to deoxidize and improve hardenability, but if it exceeds 0.100%, the face GO8 and weldability will deteriorate. It is set to 0.005 to 0.100%.

■ or Nb: 0.01-0.1O%■ or Hb requires 0.01% -1.0.1
If it exceeds 0%, GO8 resistance and weldability will deteriorate; O2N shall be 2.10%.

Hypertonic 2...(
7) Ni, which is useful as a toughening component, to more advantageously reduce deterioration without deteriorating GO8 resistance.
At least one of Ou, Or, and MO must be at least 0.051, but if lJi, Ou, and Or exceed 1.00%, weldability and hot workability will deteriorate. Moreover, it is disadvantageous in terms of economic efficiency.Moreover, the effect of MO, which helps improve the grain size and toughness of austenite grains during rolling, reaches saturation when added in excess of 1.00 yen, making it uneconomical. Since it is disadvantageous to , both are 1.00
It should be stopped at %. 1''' then B is 0.0005
Although it contributes to increasing hardenability in a small amount of about 0.00% or more,
If it exceeds 40%, the effect will be saturated and the HAZ will become severely hardened, so a range of 0.0005 to 0.004% is useful.

oe, oa are oxysulfides and grain growth inhibition I
0.0 which brings about the effect of controlling the shape of sulfide or controlling the form of sulfide.
The content is preferably 0.005% or more, but if it exceeds 0.0050%, the cleanliness may deteriorate and the mechanical properties may be impaired, so a range of 0.0005 to 0.0050% is preferable. 2 (・Next, regarding S and P as impurities in steel,
, ogo%, o, oao% or less is permissible, but especially for N, if it exceeds 0.012%, the toughness is markedly deteriorated, so it is preferably as low as 0.012% or less.

Molten steel whose composition has been adjusted according to formula (1) or (2) within the above composition range? 1. The high-strength steel of the present invention can be manufactured by applying necessary rolling to a slab, bloom, or billet obtained by a conventional steel-making method, using an ingot or continuous casting method, in accordance with a conventional method.

This structural steel can be bath-dipped galvanized after welding and assembly, and the following describes how to avoid cracking that is likely to occur in the HAZ.

Now, the breakability of the galvanized steel plate was evaluated as follows.

The test pieces were steel plates with various chemical compositions shown in Table 1.
A round bar of 0.0 mm is cut out and heated to 15 K, J by high frequency heating.
After applying a heat cycle equivalent to a welding heat input of /111L, a circumferential notch is processed.

Only the notch portion of each test piece was galvanized, various static load stresses were applied at 470° C., where the zinc is in a molten state, and the time required for the specimen to break under the stress was measured. FIG. 1 shows the relationship between the ratio Ro of the applied stress and the tensile strength at 470° C. (expressed in percent) of the unplated test piece, and the time to rupture at that time. Here R is 470″
C is a parameter that shows how many stress states the unplated test piece is maintained at before it breaks with respect to the tensile strength. R17 is at least 40%, and the higher the value, the higher the residual stress. This shows that it is resistant to cracking even when high thermal stress is applied.

Considering the plating bath immersion time in actual operation, R at 400 seconds
Using the value of 1, perform multiple regression with the chemical components to obtain (1).

The coefficients of each term on the left side of equation (2) were determined.

- In order to deal with the cracking caused by plating after welding, a restrained joint shown in Figure 2 was manufactured, and after being immersed in a hot-dip galvanizing bath, cracks in the heat-affected zone were examined.

1-1.1-2 in the figure are test beads, and 2-1,! 1
2-2 is a restraining bead, and 8 is a test plate. The test plate 8 was made by assembling plates with one side ground in a cross shape, with a fillet bead between the ground surfaces (1-1) and a fillet bead between the black skins (1-2).
) was assembled so that

The dimensions of the test plate are as follows: The thickness of the plate is 151 m, the length of the test bead L = 50 m 11%, and each overhang length of the cross L = 1.
-18 = l, = 50 fights, and the total length W of test plate 8
=150mm. The number of each of the restraining beads 2-1 and 2-2 is 20.

This restrained joint was immersed in a hot-dip galvanizing bath to check for cracks in test bead 1-1.1-2.
The results are also listed in Table 1. The component composition is within the scope of the claims, and (1), (2
If R, ≧40 is satisfied for the calculated value on the left side of Equation 1, it can be seen that no cracks have occurred in the constrained joint.

The comparative and inventive materials whose chemical compositions are shown in Table 2 of Examples were each melted into 10.0# steel ingots by vacuum melting, and hot-melted.
12) After rolling, it was air cooled, 817.18 was subjected to accelerated cooling after rolling, and 822 was quenched and tempered.

Table 2 also lists the tensile strength and toughness of the steel materials, the R value determined by the regression equation according to this invention, and the cracking inspection results in the above-mentioned restraint joint test.

The restraint joint was manufactured as already described in Fig. 2, and after degreasing, pickling, and flux treatment, it was immersed in a molten zinc bath at 455°C for 6 minutes to remove the resulting stain, and then placed in a heat shaded area. A crack inspection was conducted.

As is clear from this table, all invented steels with R values exceeding 40 based on the regression formula for the ingredients of this invention have a tensile strength of 60k.
17f/- or more, and no cracks were observed in the heat-affected zone in the restrained joint test.

Effects of the invention 60 ■For welded structural steel with a tensile strength of 4 or more,
The susceptibility of the HAZ to cracking due to the hot-dip galvanizing treatment applied after the welding process is advantageously reduced, rather than the accompanying surface defects in continuous casting applications.

[Brief explanation of the drawing]

Figure 1: Relationship graph between Ra value and rupture time, ! ...(1
6) Figure 2: Front and side views of the restrained joint crack test specimen. Patent Applicant Kawasaki Steel Co., Ltd. Representative Patent Attorney Akira Sugimura Hidete Continuation of Amendment ■, Case Description 1982 Patent Application No. 28715 2, Title of Invention High tensile steel with excellent resistance to hot-dip galvanizing cracking 3. Relationship with the case of the person making the amendment Patent applicant (125) Kawasaki Steel Corporation 4. Agent Address: 7th floor, Kasumi Building, 3-2-4 Kasumigaseki, Chiyoda-ku, Tokyo 100 Telephone: (581) 2241 (Representative) )6,
“Claims” and “Detailed Description of the Invention” of the specification to be amended
Column 7, Contents of the amendment (as shown in the attached sheet) 1. The scope of claims in the specification is corrected as per □. "2. Claim range 0.02-0-15 y Si: 0.10-0-50
* In: 0.80-2.00 j Zr: 0゜0
05~0.0501265-2980-218 Sat-96
Mn-870V-41ONb-85Al+584Zr≧
5olAl: 0°005 to 0.100 and 0.40 to 0.40, with the remainder being substantially F6 and unavoidable impurities. 01
~0.10' high-strength steel. +584Zr-2454B≧40 0.0050 Oa + 1 or 2 types of Oe as high tensile steel. & High tensile strength of ≧40 for composite steel consisting of steel base material and laminated material! i. InIO, 80~2-00 + Zr + 0.
005~0.05'0° Takashi 2 types ≧40 High tensile strength steel. ~0.0040 t O,0005~0.0050 o
a j ce high tensile steel. The two types are 265-2980-21Si-96Mn-870■-4
1ONb-85Al high tensile strength 1111M. ” 2. Table 2 on page 15 of the specification is corrected as shown in the attached sheet. 324- Procedural amendment 1. March 8, 1985 1. Indication of the case 1988 Patent Application No. 28715 2. Name of the invention High tensile strength steel with excellent hot-dip galvanizing cracking resistance (125) Kawasaki Steel Co., Ltd. Company telephone number (581) 2241 (representative) 5゜6. Subject of amendment The scope of claims in the specification in the "Claims" column of the specification is amended as follows1. 2. Claim 1 In weight%, C: 0°02 to 0.15, Si:
0.10 NO, 50, Mn: 0.80-2.00
,. Zr: 0.005-0.050, 80/i:
0.100% to 0.005 0.01~0.10N
b, one or two types of V 15-2980-21Si-9f1Mn-870V
-41ONb-1351+ 584Zr≧40 A high-strength steel having excellent resistance to hot-dip galvanizing cracking, characterized in that the remainder is substantially Fe and unavoidable impurities. i Weight N%, C: 0.02-0.15. , Si:0,
IOA-0.50, In = 0.80-2.00. Zr: 0.005~0. o 50 , 5olAl
: 0.005 to 0.100, one or two of 0.01 to 0.10 Nb and V, and further 0.05 to 1.
00. 7. Contents of correction (as shown in the attached sheet) One or more types of N soil, Ou, Or, MO, 265-2980-218i-96Mn-870V-4
1ONb-85A/+584Zr-18Ni-125a
A high-strength steel having excellent hot-dip galvanizing cracking resistance, characterized in that it contains u-o4cr-nono≧40, with the remainder being substantially Fe and unavoidable impurities. & wt%, 0:0°02 to 0.15, Si:
l・・Drop−1□−−i−■■−−−■■■−−−−10
．． 10-0.60, In: 0.80 P-LO
O. Zr: 0.005-0.050, BOIAI
: 0.005 to 0.100 and 0.01 to 0.10 of Nb, one or two types of V, rough B: 0°000
5~0.0040 265-2980-21Si-96Mn-870V
-41ONb-85A/ +584Zr -245
4B≧40, and the remainder is substantially Fe and unavoidable impurities.It has excellent hot-dip galvanizing cracking resistance. High tensile strength steel. Mori Weight%: o:o, og~0.15. Si:0.1
OA-0.50, Mn: 0.80-2.00. Zr: 0.005~o, n50, 5aint:
0.005~0.100,! =, 0.01~0.1
0 Nb, one or two types of V, 0.005 to 0
．． One or two of Oa and Oe of 0050 were added to 265-2980-21Si-961(n-870
'V −+1ONb-85Aj + 584Zr +
A high-strength steel having excellent hot-dip galvanizing cracking resistance, characterized in that it contains 14290e≧40, with the remainder being substantially Fe and unavoidable impurities. 4% by weight, 11O: 0.02-0°15. Si:0
．． 10-0.50, Mn: 0.80-2.00
. Zr + 0.005~0.050, BOIAI
:0.005~0.100t, 0.01~0.10(7
) Nb, one or two types of V, 0.0!1 to 1.0
0匈1,4...One or more of Ou, ar, No, 1B: 0.0005 to 0.0040 to 2
65-29130-BISi-96Mn-870
V-41ONb-851+584Zr-18Ni
-1280u -940r -90M0.2454B≧
A high-strength steel having excellent resistance to hot-dip galvanizing cracking, characterized in that it contains in the relationship of 40% and the remainder is substantially Fe and unavoidable impurities. a Weight %, O: 0.02-0.15, Si
: o, 10 n0.50, In + o, so ~
g,oo. Zr + 0.005~0.050, BOIAI
: 0.100 to 0.005, 0.01 to 0.1017
) Nb, one or two types of V, 0.05 to 1.0 Ni, .Ou, Or, MO+7) one or more types, 0.0005 to 0.0050 (7) O
a, 0601 type or 2 types 265-5!980-21Si-96Mn-870V-
41ONb-851+584Zr-18N Sat-1280
It is contained in the relationship of u-94Or-90Mo+142906≧40, and the remainder is substantially. A high-strength steel with excellent hot-dip galvanizing cracking resistance, characterized by containing Fe and unavoidable impurities. I weight%, C:0°02-0.15.81:0.1
0-0.50, Mn: 0. so N2. oo
. Zr: 0.005-0.050, 5ojA/:o
, oo5~0.100 g, 0.01~0.10 (7)
One or two types of Nb, V, B=0°000b0
．． 0040 tO, (1G(15~0.0050)G
a, one, 1° or two of Ge in 265-2980-218i-98Mn-8F
V-41ONb-85Aj + 584Zr-15
4B + 14290e≧40, with the remainder being substantially 1°Fe and unavoidable impurities. & Weight %, a: o, og ~ 0°15. Si:0
．． 10~0.5o, Mn: 0.80~LoO,
==Zr: 0.005 to 0.050, golA
4:0.005. ~0.100 and 0-01~0-10 (71) Nb
One or two types of tV, 0.05 to 1.00 Ni
. One or more of Ou, Or, MO, B
: 0.0005~0.0040 and 000005-
. ~0.0050 ノOa, Oe (Type 01 or 2
Seed 265-2980-1si -96Mn -870V-
41ONb -85Al + 584Zr -1sNi
-12sou -o4ar -90M0-21454
A high-strength steel having excellent resistance to hot-dip galvanizing cracking, characterized in that it contains B in the relationship of +142906≧40, with the remainder being substantially Fe and unavoidable impurities. ”

Claims (1)

[Claims] L, 0: 0.02 to 0.15 wt%, Si: 0
．． 10-0.50 wt%, In: 0.80-2.00 wt%, Zr: 0.0
05-0.05 wt%, 5olLl: 0.005
~0.100 wt % and ■ or 1 of Hb
species or two species 0. A high-strength steel having excellent resistance to hot-dip galvanizing cracking, containing 10 wt% of O1 to 111O in the following relationship as shown in the following formula %, and the remainder being substantially composed of Fe' and impurity elements.