welding of %1.2Cr %0.5 Mo to carbon stee

Date 05-13-2003 06:45

From a metallurgical point of view : welding low alloyed steel to mild (carbon) steel :

The welding parameters shall be chosen according to the low alloyed steel and the consumables according to the mild steel. The limited contribution of alloying elements coming from the the low alloyed steel during welding, will generally not increase the hardenabillity of the weld metal in any substantial manner. Consequently, low alloyed consumables (E8018) of a suitable composition can perfectly be used for this combination. However, they will have no positive influence on the strength of the joint !

Recommended consumables : E7018 !!!

By weber

Date 05-14-2003 05:45

Tim
If using an E7018 electrode, dilution in a v-groove joint (Specially with a thick material) is not high enough to have alloying elements of low alloy steel in the weld metal. In this case we have a Cr-Mo steel plate, approximately a carbon steel weld metal and a carbon steel plate.
However you’ve mentioned a good point and it made a question for me:
For welding a low alloy or alloy steel to carbon steel, considering the alloying elements, must the weld metal be near to alloy steel? Or carbon steel?

By Tim Buyle (**)

Date 05-15-2003 09:41

Dear Frank,

in case of welding (high) alloyed steel to mild carbon steel, the dillution and contribution of the alloying elements becomes very important. There are no general rules for this application ; one should consider to calculate the weld metal composition in the Schaeffler diagram or WRC diagram and then make the selection of the filler material.
In the case of stainless to carbon steel , E309 is often used (for applications lower than 200°C), or an inconel 600 type filler metal.

If you want a rule of thumb : in case of unknown composition of base materials (carbon steel, low alloyed steel, manganese steel) and joining one to another , consider the E307 filler material (very though, crack resistant). But, watch out, sometimes there are other things to be considered : corrosion properties of weld metal, strength etc. This can influence the choice of filler metal.

Referring to the CrMo steel to mild steel : customers often want matching strength with the low alloyed steel. From a metallurgical point of view, you will gain nothing ! Consumables for mild steel will also give good results as I mentioned in previous posting.

Do not forget talking and discussing with customers ! You might get a better solution for your welding problems and by eg. cheaper and better running electrodes to do the job !

By chall

Date 05-14-2003 10:29

Quite often the client will specify that the consumable must be suitable for the higher grade (alloy) material.

We encounter that requirement most of the time, and therefore we use ER80S-B2 or E8018-B2. However, I do believe Tim's response is technically accurate. I've never understood why the clients insist on matching the alloy. However, they are the client.

Charles Hall

By Tim Buyle (**)

Date 05-15-2003 09:47

Charles,

we are experiencing strange customer demands all the time.
Some things look very stupid, but you can never tell the client is not knowing what he's talking about.
However, some clients have special reasons for their demands, based on previous experience within their company. But he does not always want to share this information with others...

Tim.