High strength steel weld having improved resistance to cold cracking and a welding method

1. A weld formed by welding of steel and having a weld metal, the weld metal consisting essentially of, in mass %,

C: 0.01-0.15%,

Si: 0.02-0.6%,

Mn: 0.6-3.0%,

Al: 0.004-0.08%

Ti: 0.003-0.03%,

B: at most 0.005%

Cu: 0-1.2%

Ni: 0-3%,

Cr: 0-1.2%

Mo: 0-2%

V: 0-0.05%,

Nb: 0-0.05%

and a remainder of Fe and unavoidable impurities, the amounts of the impurities being P: at most 0.03%, S: at most 0.03%, N: at most 0.01%, Ca or Mg: at most 0.005%,

and the value of Pcm of the weld metal expressed by the following Equation (3) (in which the symbol of each element appearing in the equation indicates the content of the element in mass %) being in the range of from 0.23% to 0.35%, and the time T to cool the weld metal to 100° C. after welding satisfying the following Equation (1):

T (seconds)≧exp(7.0 ×Pw+ 4.66)  Equation (1)

where

Pw=Pcm+HD 60  Equation (2)

Pcm (mass %)=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B  Equation (3)

HD [ml/100 g]: amount of hydrogen in the weld metal immediately after welding.

2. A weld as set forth in claim 1 , wherein the weld metal contains at least one of:

Cu: at most 1.2%

Ni: at most 3%,

Cr: at most 1.2%

Mo: at most 2%

V: at most 0.05%,

Nb: at most 0.05%.

3. A weld as set forth in claim 1 wherein the weld metal contains B: 0.0002-0.0005%.

4. A welded steel structure having a weld as set forth in claim 1 .

5. A welded steel structure as set forth in claim 4 wherein the welded steel structure is selected from a steel pipe, an offshore structure, a pressure vessel, a tank, and a ship hull.

6. A welding method for steel, characterized by welding is performed to form a weld metal, the weld metal consisting essentially of, in mass %,

C: 0.01-0.15%

Si: 0.02-0.6%,

Mn: 0.6-3.0%

Al: 0.004-0.08%

Ti: 0.003-0.03%,

B: at most 0.005%

Cu: 0-1.2%

Ni: 0-3%,

Cr: 0-1.2%

Mo: 0-2%

V: 0-0.05%

Nb: 0-0.05%

and a remainder of Fe and unavoidable impurities, the amounts of the impurities being P: at most 0.03%, S: at most 0.03%, N: at most 0.01%, Ca or Mg: at most 0.005%,

and the value of Pcm of the weld metal expressed by the following Equation (3) (in which the symbol of each element appearing in the equation indicates the content of the element in mass %) being in the range of from 0.23% to 0.35%, and the time T to cool the weld metal to 100° C. after welding satisfying the following Equation (1):

T (seconds)≧exp(7.0 ×Pw+ 4.66)  Equation (1)

where

Pw=Pcm+HD 60  Equation (2)

Pcm (mass %)=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B  Equation (3)

HD [ml/100 g]: amount of hydrogen in the weld metal immediately after welding.

7. A welding method as set forth in claim 6 , wherein the weld metal includes at least one of

Cu: at most 1.2%

Ni: at most 3%,

Cr: at most 1.2%

Mo: at most 2%

V: at most 0.05%, and

Nb: at most 0.05%.

8. A welding method as set forth in claim 6 wherein the B content of the weld metal is B: 0.0002-0.005%.

9. A welding method as set forth in claim 6 wherein the welding is performed by the submerged arc method.

10. A welded steel structure having a weld as set forth in claim 2 .

11. A welded steel structure having a weld as set forth in claim 3 .

12. A welded steel structure having a weld as set forth in claim 4 .

13. A weld as set forth in claim 2 wherein the weld metal contains B: 0.0002-0.005%.

14. A welding method as set forth in claim 7 wherein the B content of the weld metal is B: 0.0002-0.005%.

15. A welding method as set forth in claim 7 wherein the welding is performed by the submerged arc method.

16. A welding method as set forth in claim 8 wherein the welding is performed by the submerged arc method.