CN1958830A - High-tension steel plate with excellent toughness for high heat energy welding heat influence part - Google Patents

Abstract

The steel plate of the present invention, by mass percent, contains: C of 0.02 to 0.05%, Si of 0.05 to 0.20%, Mn of 1.0 to 2.5%, P of less than 0.20% (0% is not included), S of less than 0.005% (0% is not included), Al of 0.01 to 0.05%, Ni of 0.2 to 2.0%, Cr of 0.5 to 2.0%, Ti of 0.005 to 0.025%, N of 0.004 to 0.010%, the following formula (1) and (2) is satisfied: 2.3 <= (Mn+0.7*Ni+Cr) <= 3.7 (1), [Cr/(Mn+0.7*Ni)] >= 0.3 (2), wherein Mn, Ni, Cr represent the content (by mass%) of each element. By this composing, the excellent tenacity of HAZ can be ensured when the plate is welded using high heat energy.

Description

The high-tensile steel of the tenacity excellent of high heat energy welding heat affected zone

Technical field

The present invention relates to the high-tensile steel of the tenacity excellent of high heat energy welding heat affected zone, even when particularly relating to the high heat energy welding that surpasses 500kJ/cm, the high-tensile steel of the tensile strength of the tenacity excellent of welding heat affected zone more than 590MPa.

Background technology

Among submerged arc welding (submerged arcwelding) that is applicable to for example box column assembling of building structure and electroslag welding (electroslag welding) etc., for the further high efficiency of realizing constructing, situation about implementing above the high heat energy welding of 500kJ/cm is arranged.But in general, big if welding input heat energy becomes, then as can be known welding heat affected zone (HAZ) organize thickization, toughness reduces easily, up to now, the viewpoint from the security of further raising building structure etc. has proposed for the various method of the flexible that improves above-mentioned HAZ.

As aforesaid method, proposition has and for example utilizes TiN and composite oxides (for example in No. 3256118 communique of Japan's patent documentation, by containing the complex body that Ti oxide compound and MnS constitute) pinning (pinning) effect brought of fine dispersion, suppress thickization of austenite grain, thereby improve the flexible method of HAZ.

But, in high heat energy welding procedure,,, can dissolve though then TiN is many if near the heat affected zone the welding metal exposes to the open air at high temperature for a long time, exist the pinning effect can't give full play to such problem.Composite oxides described later in addition, owing to be difficult to make it equably fine dispersion, so though big quantity research, the insufficient such problem of effect have been done in existence.

In addition, in order to improve the toughness of HAZ, also proposition has the technology of the miniaturization of the phase-change organization that realizes the γ intragranular, for example, proposes to have TiN and BN (with reference to No. 1824290 communique of Japan's patent) are examined the technology of utilizing as ferrite transformation.But in this case, still have a large amount of dissolvings of above-mentioned precipitate and can not get the problem of effect of sufficient at the heat affected zone that exposes to the open air for a long time at high temperature.In addition, also exploitation has the intragranular ferrite that the Ti oxide compound is disperseed to generate promotion technology (the special fair 05-017300 communique of reference example such as Japan), but identical with the situation of above-mentioned composite oxides, exists to be difficult to make it to disperse equably such problem.

In addition, from becoming the inhibition that the MA (Martensite-Austenite constituent) that destroys starting point takes place and the viewpoint of organizing miniaturization of γ intragranular, also propose to have after making C become extremely low C, add Mn, the Cr etc. that improve element as hardenability energetically, and add B, make the technology (for example No. 3602471 communique of Japan's patent) of bainite piece size (bainite block size) miniaturization thus.But in this technology, the miniaturization of piece size is sufficient hardly under high heat energy welding conditions.

Summary of the invention

The present invention carries out in view of such situation, its purpose is, a kind of 590MPa is provided above high-tensile steel, its require to maximize and the building structure of high security etc. among, when implement surpassing the submerged arc welding of high heat energy of 500kJ/cm and electroslag welding, can guarantee excellent HAZ toughness.

So-called this steel plate of the present invention, contain in quality % (down with): C:0.02～0.05%, Si:0.05～0.20%, Mn:1.0～2.5%, P:0.02% following (not containing 0%), S:0.005% following (not containing 0%), Al:0.01～0.05%, Ni:0.2～2.0%, Cr:0.5～2.0%, Ti:0.005～0.025%, and N:0.004～0.010%, and satisfy following formula (1) and (2).

2.3≤(Mn+0.7×Ni+Cr)≤3.7…(1)

[Cr/(Mn+0.7×Ni)]≥0.3…(2)

{ in the formula, Mn, Ni, Cr represent the content (quality %) of each element }

Above-mentioned steel plate, can also contain:

(a) Mo:0.2% following (not containing 0%);

(b) below V:0.05%, below the Nb:0.01% and more than a kind of the group selection that constitutes below the B:0.0020% [wherein, being condition] to satisfy following formula (3),

(V+2Nb+10B)≤0.03…(3)

{ in the formula, V, Nb, B represent the content (quality %) of each element }

(c)Cu：0.1～1.0％；

(d)Ca：0.0005～0.0030％。

According to the present invention, even owing to when implement surpassing the submerged arc welding of high heat energy of 500kJ/cm and electroslag welding etc., also can guarantee excellent HAZ toughness, so can make safe building structure etc. with shorter time.

Description of drawings

Fig. 1 is expression (Mn+0.7 * Ni+Cr) and (GBF+FSP) graphic representation of the relation of amount or piece size.

Fig. 2 is the expression (graphic representation of Mn+0.7 * Ni+Cr) and the relation of HAZ toughness (vE0).

Fig. 3 is expression [Cr/ (Mn+0.7 * Ni)] and needle-like MA[aspect ratio (major diameter/minor axis) is MA more than 2.5] the graphic representation of relation of area occupation ratio.

Fig. 4 is expression [Cr/ (Mn+0.7 * Ni)] and the graphic representation of the relation of HAZ toughness (vE0).

Fig. 5 be Cr amount with (in the relation of Mn+0.7 * Ni), the figure of the scope of expression the present invention regulation.

Embodiment

The present inventor is that the excellent high-tensile steel of toughness (following " HAZ " toughness that only is called) of the HAZ when obtaining surpassing the high heat energy welding of 500kJ/cm is studied with keen determination.It found that as follows, thereby expects the present invention:

(i) for stable and guarantee the high tenacity of heat affected zone, according to following some can realize:

Not only utilize extremely low Cization to carry out MA and suppress, and the form (being exactly the generation that suppresses needle-like MA specifically) of control MA;

Be suppressed at the thick tissue [grain boundary ferrite (GBF)+ferrite side plate (FSP)] that the γ crystal boundary is grown up;

Need the piece size miniaturization of the phase-change organization of realization γ intragranular, in the present invention, suitably contain Mn, the Ni and the Cr that improve element as hardenability,

(ii) in addition, from the group that Nb, V and B constituted that improves element as hardenability, selecting when adding more than a kind, if synthetically limit the content of these elements, suppress the generation of MA and thick lath-shaped (lath) tissue, then can suppress HAZ flexible deterioration.

At first, above-mentioned (i) is described.The present inventor finds, (Mn+0.7 * Ni+Cr), with exist between the amount (area %) of the thick tissue [grain boundary ferrite (GBF)+ferrite side plate (FSP)] of growing up and the piece size at the γ of HAZ crystal boundary related, and the relation of having put them in order.Fig. 1 shows its result.

According to Fig. 1 as can be known, for above-mentioned (GBF+FSP) amount is suppressed at below the 50 area %, shown in (1), need make that (Mn+0.7 * Ni+Cr) is more than 2.3%.On the other hand, in order to realize making below piece size miniaturization to the 40 μ m, shown in (1), need make that (Mn+0.7 * Ni+Cr) is below 3.7%.For make piece size more miniaturization reach below the 20 μ m, allow (Mn+0.7 * Ni+Cr) is to get final product below 3.3%.

2.3≤(Mn+0.7×Ni+Cr)≤3.7…(1)

{ in the formula, Mn, Ni, Cr represent the content (quality %) of each element }

Fig. 2 represents the (relation of Mn+0.7 * Ni+Cr) and HAZ toughness (vE0 that measures according to the method shown in the embodiment described later) in addition, (Mn+0.7 * Ni+Cr) is in 2.3～3.7% the scope if make as can be known, suppress (GBF+FSP) amount, and realize the miniaturization of piece size, even then when the high heat energy of enforcement welds, also can guarantee the HAZ toughness of the excellence that vE0:100J is above.

In addition, the present inventor finds, between the form of [Cr/ (Mn+0.7 * Ni)] and MA [be exactly specifically aspect ratio (major diameter/minor axis) be the area occupation ratio of the needle-like MA more than 2.5] existence related, and the relation of having put them in order.Fig. 3 shows its result.Here, the area occupation ratio of needle-like MA is the ratio with respect to the needle-like MA of the sightingpiston of microscopically.

According to Fig. 3 as can be known, for the area occupation ratio with needle-like MA is suppressed at below 4%, shown in (2), need [Cr/ (Mn+0.7 * Ni)] as more than 0.3.

[Cr/(Mn+0.7×Ni)]≥0.3…(2)

{ in the formula, Mn, Ni, Cr represent the content (quality %) of each element }

Also have, when trying to achieve Fig. 1,3 data, (GBF+FSP), the area occupation ratio of piece size and needle-like MA tries to achieve as follows.That is, organize photo,, measure its ratio with respect to the sightingpiston of this microscopically by image analysis by the tissue of range estimation selection differentiation object from this photo with the microscopic examination shooting.

Fig. 4 represents the relation of [Cr/ (Mn+0.7 * Ni)] and HAZ toughness (vE0 that measures according to the method shown in the embodiment described later) in addition, if incite somebody to action as can be known [Cr/ (Mn+0.7 * Ni)] as the generation that suppresses needle-like MA more than 0.3, even then when the high heat energy of enforcement welds, also can guarantee the HAZ toughness of the excellence that vE0:100J is above.

As mentioned above, in order to make Mn, Ni and Cr optimization positively improving HAZ toughness, and guarantee the intensity of mother metal and toughness etc., the content of Mn, Ni and Cr is in the following ranges respectively.

<Mn：1.0～2.5％>

Mn improves hardenability and the intensity and the flexible element that help to guarantee mother metal.In addition, also be the element that helps the piece size miniaturization of HAZ.Make it to contain more than 1.0% in order to make these effect performances.But if Mn becomes excessive, then MA increases, HAZ toughness deterioration.Therefore the Mn amount will be suppressed at below 2.5%.

<Ni：0.2～2.0％>

Thereby Ni improves hardenability guarantees the strength and toughness of mother metal, and is the element that prevents certain effect to thermal crack.In addition, also be the element that helps the piece size miniaturization of HAZ, contain more than 0.2% in order to bring into play these effects.On the other hand, if Ni becomes excessive, then the oxide skin flaw takes place easily, therefore it is suppressed at below 2.0%.

<Cr：0.5～2.0％>

Cr improves hardenability, is element useful on the intensity of guaranteeing mother metal and toughness.The useful element of piece size miniaturization that couple HAZ is also arranged in addition.Contain more than 0.5% in order to bring into play these effects.But if Cr becomes excessive, then MA increases, HAZ toughness deterioration.Therefore Cr will be suppressed at below 2.0%.

Fig. 5 is illustrated in to show Cr amount and (aforementioned formula (1) and formula (2) in the graphic representation of the relation of Mn+0.7 * Ni), with the upper limit of above-mentioned Cr amount and the (scope that lower limit surrounded (oblique line part) of Mn+0.7 * Ni), but as shown in Figure 5, if the relation of Cr, Mn and Ni is in the scope of oblique line part, then compared with prior art, the HAZ toughness in the time of the high heat energy of enforcement can being welded more positively improves.

In order positively to improve HAZ toughness, and other characteristic of the intensity of steel plate (mother metal) and toughness etc. is possessed equally as above-mentioned, the content of the composition beyond above-mentioned is in the following ranges.

<C：0.02～0.05％>

C be guaranteeing of strength of parent and thickization that suppresses the γ grain to guarantee the needed element of HAZ toughness, need contain more than 0.02% in order to make this effect performance.On the other hand, excessive if the C quantitative change gets, then except MA increased, the high-temperature stability of the TiN that forms when casting also reduced, so HAZ toughness deterioration on the contrary.In addition, it also becomes the reason of low temperature crackle deterioration.Therefore, the C amount will be suppressed at below 0.05%.

<Si：0.05～0.20％>

The needed element of deoxidation when Si is the system steel need contain more than 0.05%.But if Si becomes excessive, the HAZ toughness deterioration because MA increases then is so be suppressed at it below 0.20%.

＜P:0.02% following (not containing 0%) 〉

Because P can cause the deterioration of base metal tenacity and because of the segregation of P causes the destruction of γ crystal boundary, so it is suppressed at below 0.02%.

＜S:0.005% following (not containing 0%) 〉

S is the same with above-mentioned P, because the destruction that also can cause the deterioration of base metal tenacity and cause the γ crystal boundary because of the segregation of MnS is suppressed at it below 0.005%.

<Al：0.01～0.05％>

The needed element of deoxidation when Al is the system steel need contain more than 0.01%.But if Al becomes excessive, then the thick inclusion of aluminum oxide etc. increases and the base metal tenacity deterioration.Add that MA increases, HAZ toughness is deterioration also, so it is suppressed at below 0.05%.

<Ti：0.005～0.025％>

Ti combines the element that forms TiN with N, this TiN improves high-temperature stability in the steel of the present invention that low C has changed, and makes the γ grain miniaturization of HAZ, helps the HAZ flexible to improve effectively.In order to make such effect performance Ti being contained more than 0.005% (is preferably more than 0.010%).On the other hand, if Ti becomes excessive, thickization of TiN then, base metal tenacity, HAZ toughness is deterioration together, therefore it is suppressed at below 0.025%.

<N：0.004～0.010％>

N combines with above-mentioned Ti and forms TiN, makes the γ grain miniaturization of HAZ by this TiN, is the element that helps flexible to improve.Making the N amount in order to bring into play this effect is more than 0.004%.On the other hand, if N excessively exists, then solid solution N increases, and base metal tenacity and HAZ toughness is deterioration together.Therefore the N amount will be suppressed at below 0.010%.

What the present invention stipulated contains element as mentioned above, and surplus is iron and unavoidable impurities, as this unavoidable impurities, can allow doping elements sneak into according to the state of raw material, goods and materials, producing apparatus etc.In addition, can also contain following element more energetically.

＜Mo:0.2% following (not containing 0%) 〉

Mo improves hardenability temper softening drag, is to guarantee effective elements on the strength and toughness of mother metal, in order to bring into play this effect, Mo is contained more than 0.05%.But if Mo becomes excessive, then owing to the recrystallize restraining effect, in rolling thickization of back γ grain meeting, the piece size of phase-change organization is thickization also.Therefore, in the present invention the Mo amount is suppressed at below 0.2%.

＜below V:0.05%,

Nb:0.01% following and

Select more than a kind in the following group that is constituted of B:0.0020%

[but in scope of following formula (3)] 〉

(V+2Nb+10B)≤0.03…(3)

{ in the formula, V, Nb, B represent the content (quality %) of each element }

This V, Nb, B are effective elements on the guaranteeing of the strength and toughness of mother metal.V improves hardenability temper softening drag, is to guarantee effective elements on the strength and toughness of mother metal.But if V is excessive to be contained, then HAZ toughness deterioration, so V amount preferably is suppressed at below 0.05%.

Nb makes the miniaturization of γ grain, is effective elements on the guaranteeing of the strength and toughness of mother metal.But if Nb is excessive to be contained, then therefore HAZ toughness deterioration preferably is suppressed at below 0.01%.

B improves hardenability, is effective elements on the guaranteeing of the strength and toughness of mother metal.But if B is excessive to be contained, then the iron carbon boride is separated out the base metal tenacity deterioration, therefore preferably is suppressed at below 0.0020%.

In addition, from the group that above-mentioned V, Nb and B constituted, select to contain sometimes more than a kind, also need to make it to satisfy following formula (3).By (V+2Nb+10B) is suppressed at below 0.03%, as described (ii) shown in, can suppress the generation of MA and thick lath-shaped tissue, can suppress HAZ flexible deterioration.

<Cu：0.1～1.0％>

Cu makes effective elements in the hardenability raising, in order to make this effect performance, preferably contains more than 0.1%.But if Cu becomes excessive, then when rolling, cause thermal crack easily, therefore preferably it is suppressed at below 1.0%.

<Ca：0.0005～0.0030％>

Ca is granular with the morphology Control of non-metallic inclusion, is make effective elements aspect the raising of HAZ toughness.For this effect is given full play to, Ca is contained more than 0.0005%, but if make it excessively to contain, then thickization of Ca inclusion make the toughness deterioration of mother metal.Therefore the Ca amount is preferably below 0.0030%.

For obtain tensile strength be 590MPa with upper steel plate, generally carry out known thermal treatment and get final product.Wherein an example is recorded in the embodiment of back.

Below, exemplify embodiment and be described more specifically the present invention, but the present invention is not subjected to the qualification of following embodiment certainly, also suitable change and implementing in addition in the scope of aim described later before can being suitable for, this all is contained in technical scope of the present invention.

[embodiment]

After the steel melting that one-tenth shown in the table 1 is grouped into becomes slab (slab), be heated to 1100 ℃, carry out hot rolling up to thickness of slab 50mm.Afterwards, reheat to 930 ℃ quenches, and carries out tempering and makes at 500 ℃.Also have, also can after hot rolling, quench immediately, tempering.

Use the steel plate that obtains then, as following, carry out the mensuration and the evaluation of HAZ flexible of strength of parent.

[mensuration of strength of parent]

From the t/4 (t is a thickness of slab) of each steel plate, on right angle orientation, extract No. 4 test films of JISZ2201 with respect to rolling direction, carry out tension test by the main points of JISZ 2241, measure tensile strength (TS).Then, tensile strength is the high tensile that is evaluated as more than the 590MPa.

[evaluation of HAZ flexible]

Near the weld seam (bond) that heat energy is welded in simulation when being the electroslag welding of 800kJ/cm heat affected zone be subjected to thermal process, to the 12.5mm that extracts from t/4 thick * 32mm is wide * the long test film of 55mm, by heating: kept 30 seconds at 1400 ℃, 800～500 ℃ cooling time (Tc): 700 seconds circulation, implement the thermal treatment [test film after the thermal treatment with high-frequency induction heating apparatus, be equivalent to combinatorial surface sheet material (skin plate) (50mm is thick) and every matrix (diaphragm) (50mm is thick), the heat affected zone the during electroslag welding of welding heat energy and be 800kJ/cm].

Then, extract the V nick-break test sheet of JIS Z 2202, carry out pendulum impact test by the main points of JISZ 2242,0 ℃ of absorption energy (vE0) down of determination test temperature, this absorption can be the tenacity excellent that is evaluated as HAZ more than the 100J.

These results represent in table 2.

[table 1]

The ※ impurity F e and the impurity in submersible generation not.

[table 2]

Experiment No.	The mother metal characteristic	HAZ toughness
			TS (Mpa)	vE 0 (J)
	1	675			108
2			691	105
	3	641			127
4			675	106
	5	649			110
6			614	102
	7	670			103
8			633	134
	9	654			121
10			662	112
	11	673			118
12			675	109
	13	671			48
14			618	72
	15	689			63
16			598	74
	17	680			81
18			665	89
	19	630			78
20			640	52
	21	654			59
22			622	65
	23	671			83
24			650	44
	25	678			45
26			640	88
	27	657			53
28			647	48

Can do following investigation (also having the experiment No. during following No. represents) by table 1, table 2.

Satisfying the prerequisite of the present invention regulation, be in the steel plate of No.1～12 of the oblique line scope (scope of the present invention) of described Fig. 1, is to demonstrate good HAZ flexible high-tensile steel as can be known.

With respect to this, No.13～28 of the regulation of discontented unabridged version invention have following problem respectively.That is, No.13 is because the C amount surpasses the upper limit, so HAZ toughness deterioration.

In addition, No.14 is because Mn measures and the Ni quantity not sufficient, so HAZ toughness deterioration.

No.15 and No.17 are because (Mn+0.7 * Ni+Cr) surpass the upper limit, No.16 is because (Mn+0.7 * Ni+Cr) be lower than lower limit, so the toughness of HAZ is all little in addition.

No.18 is because the Cr amount is excessive, and No.19 is because the Al amount is excessive, so HAZ toughness deterioration in addition.

No.20 is because of the N quantity not sufficient, so HAZ toughness deterioration.

In addition, No.21 is because Ti amount and N amount surpass the upper limit, so HAZ toughness deterioration.

No.22 is because [Cr/ (Mn+0.7 * Ni)] is lower than lower limit, so HAZ toughness deterioration.

No.23 is because of the excessive Mo that contains, so HAZ toughness deterioration.

Though No.24 V and B content separately is in the specialized range, because (V+2Nb+10B) surpass 0.03%, so HAZ toughness deterioration.

No.25 is because the Mn amount is excessive, and No.26 is because the Ni amount is excessive, and No.27 is because the Ti amount is excessive, and in addition, No.28 is because the N amount is excessive, so HAZ toughness inequality.

Claims (8)

1. steel plate is characterized in that % contains in quality:

C:0.02～0.05%, Si:0.05～0.20%, Mn:1.0～2.5%, P:0.02% following but do not contain 0%, S:0.005% is following but do not contain 0%, Al:0.01～0.05%, Ni:0.2～2.0%, Cr:0.5～2.0%, Ti:0.005～0.025%, and N:0.004～0.010%

And, satisfy following formula (1) and (2),

2.3≤(Mn+0.7×Ni+Cr)≤3.7…(1)

[Cr/(Mn+0.7×Ni)]≥0.3…(2)

In formula, Mn, Ni, Cr represent the mass percentage content of each element.

2. steel plate according to claim 1 is characterized in that, also contains below the Mo:0.2% in quality % but does not contain 0%.

3. steel plate according to claim 1 is characterized in that, also to satisfy the mode of following formula (3), also contains below V:0.05%, below the Nb:0.01% and more than a kind of the group selection that is constituted below the B:0.0020% in quality %,

(V+2Nb+10B)≤0.03…(3)

In formula, V, Nb, B represent the mass percentage content of each element.

4. steel plate according to claim 1 is characterized in that, also contains Cu:0.1～1.0% in quality %.

5. steel plate according to claim 1 is characterized in that, also contains Ca:0.0005～0.0030% in quality %.

6. steel plate according to claim 1 is characterized in that, tensile strength is more than the 590MPa.

7. steel plate according to claim 1 is characterized in that, in quality % (Mn+0.7 * Ni+Cr) below 3.3%.

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