Dissimilar welding: unalloyed & low alloyed steels
In this blog we discus the most common combinations of dissimilar welding. Use the list below to navigate to the specific joint type you're interested in. The most common dissimilar joints are:
- Unalloyed to unalloyed (different strengths)
- Unalloyed to high strength (different strengths)
- High-strength steel with High-strength steels (different strength)
- Unalloyed with high-temperature strength
- Heat-resistant - Heat-resistant (different strengths)
- Unalloyed with Low temperature unalloyed steels
- Cold tough with colg tough (different low temperatures and strengths)
- Unalloyed with quenched and tempered steels
- Quenched and tempered - Quenched and tempered (different strengths)
- Hard manganese steel to unalloyed (special case)
dissimilar welding: Unalloyed with unalloyed steels (different in strength)
It must be ensured that the strength of the weld metal only has to correspond to the strength of the weaker material; i.e. in the case of a combination of S235 with S355 or 460, 235 MPa yield strength is sufficient.
In practice, however, there are virtually no filler materials with a yield strength of less than 355 MPa. The situation is different for notched bar impact values. Here, the requirements placed on the design should be used as a second selection criteria.
dissimilar welding: Unalloyed with high-strength steels (often add-on parts)
A constellation that should be considered with gradations in the difference in strength. For example, when combining S235 with S460, the filler metal should be matched to the S235. However, as previously mentioned, in practice this will result in a filler material with a yield strength of 355 MPa. In this case, the impact temperature is ultimately the decisive factor for the selection of the filler material.
dissimilar welding: High-strength steel with High-strength steels (different strength)
The same procedure should be followed when selecting the filler metal for two high-strength steels. However, if there is a very large difference between the strengths, such as S460 and S890, the strength of the filler metal should be selected in the middle range. This prevents the weld seam from becoming a weak point in the construction due to a high strength jump. The welding parameters should be matched to the higher-strength part.
dissimilar welding: Unalloyed with high-temperature strength
A joint that is usually welded with the similar filler metal of the lower alloyed material. If post-weld heat treatment is required, the annealing temperature must be matched to the two base materials and the filler metal. Mo-alloyed or CrMo-alloyed filler metals are usually used here. It should be noted that CrMo-alloyed filler metals almost always require heat treatment to achieve their properties.
dissimilar welding: Heat-resistant - Heat-resistant (different strengths)
When combining two different heat-resistant materials, the orientation for the selection of the filler material is the low-alloy side, e.g. 16Mo3 with 13CrMo4-5.
However, a heat treatment should be selected that is suitable for all materials involved. Reference values for the temperature control and heat treatment of the welding filler material can be found in the table. These are also listed in the corresponding standards for the filler materials.
| Filler metal | Preheating and interpass temperature (°C) | PWHT | |
| Temp. (°C) | min. time (h) | ||
| Mo, MoL | < 250 | 570 - 620 | >0,5 |
| CrMo1, CrMo1L | 200 - 300 | 660 - 700 | >0,5 |
| CrMo2, CrMo2L | 200 - 350 | 690 - 750 | >0,5 |
| CrMo5 | 300 - 350 | 730 - 760 | > 1 |
| CrMo9 | 200 - 300 | 750 - 770 | > 2 |
dissimilar welding: Unalloyed with Low temperature unalloyed steels
Low temperature unalloyed steels, in addition to their strength, have sufficient plastic deformation capacity at low temperatures.
Ni in particular improves cold toughness. Low-temperature steels have up to 3.5 % Ni. Both sides of the mixed joint can be welded to both unalloyed and Ni-containing materials with welding consumables of the same or similar type. These grades generally provide sufficient Av values down to -60°C, in exceptional cases also down to -80°C.
dissimilar welding: Cold tough with colg tough (different low temperatures and strengths)
Above this temperature, e.g. down to -120°C and above, the Ni content must be increased to 5 to 9 %. This increases the risk of hot cracking. For this reason, a welding filler of the same type is not recommended. Welding should be carried out with overalloyed austenitic or nickel-based filler metals.
dissimilar welding: Unalloyed with quenched and tempered steels
The question here is: What is quenching and tempering? Quenching and tempering is a process for the heat treatment of metals in which hardening (heating followed by rapid cooling) is combined with subsequent tempering. As a rule, the aim of hardening is to produce a hard structure consisting of martensite and bainite or a mixture of the two.
It may be necessary to prepare both sides of the material for welding using different preheating processes. This would be the case, for example, with a combination of S355 and 42CrMo 4. The S355 side should be heated without preheating or to approx. 80°C, depending on the material thickness, and the 42 CrMo 4 side to at least 300°C due to the high C content. The interpass temperature should be adjusted to the more critical partner. The welding parameters should be selected in such a way that mixing can be kept as low as possible. Ensure that the component cools down slowly. (Measures may have to be taken to make this possible).
In special cases, nickel-based welding consumables can also be used.
In general, heat-treatable steels are only suitable for welding to a limited extent. Their suitability for welding deteriorates further with increasing C content. For this reason, they require special heat treatment during welding and subsequent annealing. There are hardly any welding consumables of the same type. The selection is made according to the given strength properties, taking into account the necessary heat treatment.
Dissimilar welding: Quenched and tempered (different strengths)
The weldability of quenched and tempered steels is generally limited. Their weldability deteriorates with increasing carbon content.
They therefore require special heat treatment during welding and subsequent annealing.
Similar alloyed filler metals are rarely available. The selection is made according to the given strength properties, taking into account the required heat treatment.
CEWELD has types for almost all welding processes in its range.
In many cases the practical application conditions allow the use of softer filler metals.
The use of nickel based welding consumables is also possible. The use of superalloyed austenitic CrNi filler metals should only be considered if no subsequent heat treatment is required.
A very special case is hard manganese steel with unalloyed steel.
For these mixed joints, such as (e.g. X120Mn12 with S235JRG1), the use of austenitic Cr-Ni welding consumables with an increased Mn content is recommended.
In many cases, the practical application conditions allow the use of softer filler metals. The use of nickel-based filler metals is also possible. The use of superalloyed austenitic CrNi filler metals should only be considered if no subsequent heat treatment is carried out.
Certilas has a solution for almost all problems relating to the selection of filler metals.
we will be happy to help you select the right filler material.
Want to know more about welding mixed joints? Check out the blogs below about different metals.
