Chromium in 0030 steel. How much is too much when welding?

[DaveCary]

We use SAEJ435 0030 steel in some of our cast components most of which are welded with an AWS E70xx spec. recently some of the steel has came in with Chromium values at 0.60. I cant find a set amount that is acceptable in weldable steel. All I have gone by is a Carbon Equivalency formula that uses Cr in this. What can you tell me regarding the Cr and it affect on the CE.
Thanks
Dave

 

[metengr]

You won't find any limitation because during welding preheat (and possibly post weld heat treatment) can be effectively used to compensate for the increase in chromium content of a steel.

The carbon equivalent (CE) formula's were derived to show weldability comparisons between various materials, taking into account the affects of alloying elements on hardenability, and the need for preheat to reduce susceptibility to hydrogen cracking.

Please refer to FAQ for some additional information on CE equations;
faq330-1077


The higher the CE number, the greater the hardenability of the steel, and susceptibility to forming an adverse microstructure in the base metal heat affected zone during welding.

A typical CE equation is shown below,

CIIw = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
(elements are expressed in weight percent amounts)

Other than carbon content (which obviously has the greatest impact on CE), the lower the number in the denominator, the greater the impact on the CE value, and the need for preheat. In this case, Cr is as effective as Mo and V in determining the need for preheat requirements. Thus, increasing chromium requires an increase in preheat to reduce susceptibility to cracking during and after welding.

If necessary, post weld heat treatments are used to assure post weld performance by reducing harmful residual stresses and to reduce the hardness of an adverse microstructure that could form in the weld heat affected zone of certain base metals.