Preheating temperature of commonly used steel

Thickness

mm

preheating temperature

℃

Thickness

mm

preheating temperature

℃

Carbon steel and its castings with carbon content less than or equal to 0.35%

≥26

100～200

≥30

≥28

100～150

C-Mn(16Mn、16MAR)

≥15

150～200

Mn-V(15MnV、15MnVNR、18MnMoNbR)

0.5Cr-0.5Mo(12CrMo)

—

—

≥15

150～200

1Cr0.5Mo(15CrMoZG20CrMo)

≥10

150～250

1.5Mn-0.5Mo-V(14MnMoV 18MnMoNbg)

—

—

1Cr-0.5Mc-V(12Cr1MoV)

—

200～300

—

—

1.5Cr-Mo-V(15Cr1Mo1V)

2Cr-0.5Mo-VW(12Cr2MoWVB)

1.75Cr 0.5MoV

2.25Cr-1Mo(12Cr2Mo  10CrM0910)

3Cr-IMo-VTi(12Cr3MoVSiTiB)

≥6

250～350

9Cr-1Mc-V

—

250～300

—

—

12Cr-1Mo，9Cr-1Mo

350～400

1Cr5Mo

—

≥250℃

ZGl5CrlMolV

60～100℃(When the cold welding)，

100～150℃(When the hot welding)

ZG15Cr2Mol

60～100℃(When the cold welding)，

150～200℃(When the hot welding)

ZG20CrMoV

250～300℃(When the hot welding)

注1：

(1)The temperature in the table is the minimum preheating temperature determined according to the wall thickness.

When tungsten argon arc welding backing is used, can reduce according to the lower temperature 50 ℃ preheat.

(2) the wall thickness is greater than or equal to 6 mm steel pipe or tube, big thickness under negative temperature, when welding the panel should be higher than falling in to the lowest preheating degrees 20 ℃ to 50 ℃.

Low alloy steel pipe with wall thickness less than 6mm and carbon steel pipe with wall thickness more than 15mm shall be properly preheated when welding at negative temperature.

(3) when the pressure pieces and non-pressure pieces are welded, they should be preheated according to the pressure pieces.

When welding the nozzles with the main pipe, preheat according to the main pipe.

Note 2: the diameter is less than 60 mm, tube wall thickness less than 6 mm, using argon arc welding, preheating temperature of 50 ℃ ~ 100 ℃.

≤12.5

>12.5

～25

>25

～37.5

>37.5

～50

>50

～75

>75

～100

>100

～125

Constant temperature timeh

C≤0.35(20、ZG25)

C-Mn(16Mn)

600～650

1.5

2

2.25

2.5

2.75

0.5Cr-0.5Mo(12GrMo)

650～700

0.5

1

1.5

2

2.25

2.5

2.75

1Ct-0.5Mo

(15GrMo、ZC20CrMo)

670～700

0.5

1

1.5

2

2.25

2.5

2.75

1Cr-O.5Mo-V

(12CrlMoV、ZG20CrMoV)

1.5Cr4Mo~V

(ZGl5CrlMolV)

1.75Ct-0.5Mo-V

720～750

0.5

1

1.5

2

3

4

5

2.25Ct-1Mo

720～750

0.5

1

1.5

2

3

4

5

2Cr-O.5Mo-VW

(12Cr2～90WVTiB)

3Cr-IMc-VTi

(12Cr3MoVSiTiB)

750～780

0.75

1.25

1.75

2.25

3.25

4.25

5.25

9Cr-IMc-V

12Ct-1Mo

0.5

1

1.5

2

3

4

5

Note: the constant temperature time of welding parts (pipe base) or repair welding parts in connection with the main pipe can be determined according to the nominal thickness of the welding parts, instead of the welding part thickness, but should not be less than 30min.

The nominal thickness of the welding ', can be calculated as follows:

When h<5mm，δ′=3h+5

When h=5mm～10mm，δ′=2h+10

When h>lOmm，δ′=h+20

式中：

h--Weld height or repair weld thickness，mm。