How to weld > Preheating and interpass temperature
Recommended interpass/preheating temperature
The single plate thickness (diameter) is defined according to the illustration below.
Schematic drawing showing single plate thickness (diameter).
The single plate thickness (diameter) is shown on the x-axis in the tables bewow. Minimum recommended preheat and interpass temperatures are given for different single plate thicknesses for different Hardox® steels. Note that every increase in temperature starts at 0.1 mm (0.004”) above the indicated thickness in the charts.
Additionally, the tables also apply to Hardox® Tubes, specifically:
The preheating temperature for Hardox® 400 also applies to Hardox® 400 Tubes, which are available in thickness of 3 - 6 mm (0.118”-0.236”).
The preheating temperature for Hardox® 500 also applies to Hardox® 500 Tubes, which are available in thickness of 3 - 6 mm (0.118”-0.236”).
The interpass temperature provided in the table below represents the maximum recommended temperature within the joint (on top of the weld metal) or immediately adjacent to the joint (start position), just before commencing the next weld pass.
Hardox® 400
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® 400
- 20.0 mm
- 0.787"
No preheating
225 °C (437 °F)
20.1 - 45.0 mm
0.788" - 1.772"
75 °C (167 °F)
225 °C (437 °F)
45.1 - 50.0 mm
1.773" - 1.969"
100 °C (212 °F)
225 °C (437 °F)
50.1 - 80.0 mm
1.97" - 3.15"
175 °C (347 °F)
225 °C (437 °F)
80.1 - 100.0 mm
3.151" - 3.937"
200 °C (392 °F)
225 °C (437 °F)
Hardox® 400 Sheet
2.0 - 8.0 mm
0.079" - 0.315"
No preheating
100 °C (212 °F)
Hardox® 400
Hardox® 450
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® 450
- 25.0 mm
- 0.984"
No preheating
225 °C (437 °F)
25.1 - 40.0 mm
0.985" - 1.575"
125 °C (257 °F)
225 °C (437 °F)
40.1 - 160.0 mm
1.576" - 6.299"
150 °C (302 °F)
225 °C (437 °F)
Hardox® 450 Sheet
2.0 - 8.0 mm
0.079" - 0.315"
No preheating
100 °C (212 °F)
Hardox® 450
Hardox® 450 CR
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® 450 CR
0.8 - 2.1 mm
0.031" - 0.083"
No preheating
100 °C (212 °F)
Hardox® 450 CR
Plate thickness (mm)
0.8 - 2.1 mm
Plate thickness (inch)
0.031" - 0.083"
Minimum preheating temperature
No preheating
Max interpass temperature
100 °C (212 °F)
Hardox® 500
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® 500
- 13.0 mm
- 0.512"
No preheating
225 °C (437 °F)
13.1 - 30.0 mm
0.513"-1.181"
175 °C (347 °F)
225 °C (437 °F)
30.1 - 103.0 mm
1.182" - 4.055"
200 °C (392 °F)
225 °C (437 °F)
Hardox® 500 Sheet
2.0 - 7.0 mm
0.079" - 0.276"
No preheating
100 °C (212 °F)
Hardox® 500
Hardox® 500 Tuf
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® 500 Tuf
- 16.0 mm
- 0.63"
No preheating
225 °C (437 °F)
16.1 - 25.4 mm
0.631" - 1"
75 °C (167 °F)
225 °C (437 °F)
25.5 - 35.0 mm
1.01" - 1.378"
125 °C (257 °F)
225 °C (437 °F)
35.1 - 38.1 mm
1.379" - 1.5"
150 °C (302 °F)
225 °C (437 °F)
Hardox® 500 Tuf Sheet
2.0 - 7.0 mm
0.079" - 0.276"
No preheating
100 °C (212 °F)
Hardox® 500 Tuf
Hardox® 550
Plate thickness
Plate thickness
Minimum preheating temperature
Max interpass temperature
Hardox® 550
8.0 - 11.0 mm
0.315" - 0.433"
125 °C (257 °F)
225 °C (437 °F)
11.1 - 30.0 mm
0.434" - 1.181"
175 °C (347 °F)
225 °C (437 °F)
30.1 - 65.0 mm
1.182" - 2.559"
200 °C (392 °F)
225 °C (437 °F)
Hardox® 550
Hardox® 600
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® 600
3.0 - 10.0 mm
0.118" - 0.394"
150 °C (302 °F)
225 °C (437 °F)
10.1 - 30.0 mm
0.395" - 1.181"
175 °C (347 °F)
225 °C (437 °F)
Hardox® 600 Sheet
2.0 - 6.0 mm
0.079" - 0.236"
150 °C (302 °F)
225 °C (437 °F)
Hardox® 600
Hardox® HiAce
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® HiAce
- 8.0 mm
- 0.315"
No preheating
225 °C (437 °F)
8.1 - 25.0 mm
0.316 - 0.984"
125 °C (257 °F)
225 °C (437 °F)
25.1 - 35.0 mm
0.985" - 0.378"
150 °C (302 °F)
225 °C (437 °F)
35.1 - 60.0 mm
0.379" - 2.362"
175 °C (347 °F)
225 °C (437 °F)
60.1 - 100.0 mm
2.363" - 3.937"
200 °C (392 °F)
225 °C (437 °F)
Hardox® HiAce Sheet
2.0 - 6.0 mm
0.079" - 0.236"
No preheating
100 °C (212 °F)
Hardox® HiAce
Hardox® HiTemp
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® HiTemp
- 10.0 mm
- 0.394"
No preheating
300 °C (572 °F)
10.1 - 25.0 mm
0.395" - 0.984"
100 °C (212 °F)
300 °C (572 °F)
25.1 - 51.0 mm
0.985" - 2"
125 °C (257 °F)
300 °C (572 °F)
Hardox® HiTemp
Hardox® HiTuf
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® HiTuf
40.0 - 70.0 mm
1.575" - 2.756"
100 °C (212 °F)
300 °C (572 °F)
70.1 - 160.0 mm
2.757" - 6.299"
125 °C (257 °F)
300 °C (572 °F)
Hardox® HiTuf
Plate thickness (mm)
40.0 - 70.0 mm
Plate thickness (inch)
1.575" - 2.756"
Minimum preheating temperature
100 °C (212 °F)
Max interpass temperature
300 °C (572 °F)
Austenitic welding consumables
Plate thickness (mm)
Plate thickness (inch)
Minimum preheating temperature
Max interpass temperature
Hardox® Extreme
12.0 - 19.0 mm
0.472" - 0.748"
100 °C (212 °F)
100 °C (212 °F)
Hardox® HiAce
- 100.0 mm
- 3.937"
No preheating
225 °C (437 °F)
Hardox® 600
3.0 - 10.0 mm
0.118" - 0.394"
No preheating
225 °C (437 °F)
10.1 - 65.0 mm
0.395" - 2.559"
100 °C (212 °F)
225 °C (437 °F)
Hardox® 600 Sheet
2.0 - 6.0 mm
0.079" - 0.236"
No preheating
225 °C (437 °F)
Hardox® Extreme
Plate thickness (mm)
12.0 - 19.0 mm
Plate thickness (inch)
0.472" - 0.748"
Minimum preheating temperature
100 °C (212 °F)
Max interpass temperature
100 °C (212 °F)
Hardox® HiAce
Plate thickness (mm)
- 100.0 mm
Plate thickness (inch)
- 3.937"
Minimum preheating temperature
No preheating
Max interpass temperature
225 °C (437 °F)
Hardox® 600
Plate thickness (mm)
3.0 - 10.0 mm
Plate thickness (inch)
0.118" - 0.394"
Minimum preheating temperature
No preheating
Max interpass temperature
225 °C (437 °F)
Hardox® 600 Sheet
Plate thickness (mm)
2.0 - 6.0 mm
Plate thickness (inch)
0.079" - 0.236"
Minimum preheating temperature
No preheating
Max interpass temperature
225 °C (437 °F)
Interpass temperatures for Hardox® steel. **) Interpass temperatures of up to approx. 400 °C (752 °F) can be used in certain cases for Hardox® HiTemp and Hardox® HiTuf. In such cases, use the SSAB WeldCalc tool.
The minimum recommended preheating and maximum interpass temperatures listed in the tables above and below, remain unchanged even at higher heat inputs exceeding 1.7 kJ/mm (43.2 kJ/inch). This guidance is based on the assumption that the welded joint is allowed to cool naturally in ambient air to reach ambient temperature.
It's important to note that these recommendations also apply to tack welds and root runs. In general, it is recommended to use tack welds that are 50 mm (2 inches) in length. For joints with plate thicknesses of up to 8 mm (0.31 inches), shorter tack lengths may be employed. The spacing between tack welds can be varied as required.
Recommended preheat and interpass temperatures for Hardox® steels, plate thickness in mm.
Recommended preheat and interpass temperatures for Hardox® steels, plate thickness in inches.
The information in this report is only applicable to SSAB’s products and should not be applied to any other products than original SSAB products.
This report provides general results and recommendations for SSAB steel products. This report is subject to SSAB’s Terms of Use. It shall be the user's responsibility to verify that the information contained herein is correct and is suitable to be used for the particular purpose and application of the user. The report is intended to be used by professional users only who possess adequate expertise, qualification and knowledge for the safe and correct use of the results and recommendations in this report. This report is provided “as is”. The use of the report is at user’s own discretion and risk and that users will be solely responsible for any use of this report. SSAB disclaims any liability for the content or potential errors of this report, including but not limited to warranties and condition of merchantability or fitness for a particular purpose or suitability for individual applications. SSAB shall not be liable for any kind of direct or indirect damages and/or costs related to or arising therefrom, whether special, incidental, consequential or directly or indirectly related to the use of, or the inability to use, the report or the content, information or results included therein.
