What is the best steel type that is both castable and weldable, that would be similar to A36 carbon steel? Either an alloy steel or carbon steel would be ok?
Bagman2524;
I am going to answer your question with the following question and advice;
Question; What is the application?
Advice;
Regarding welding, select a carbon or low alloy steel that has a CE (carbon equivalent) value at or below 0.35. Use the FAQ for advice on weldability;
faq330-1077
Bagman2524;
I concur with arunmrao's recommendation. Another option is ASTM A27 or A148 and select the Grade that is closest in mechanical properties to ASTM A36. One item (disregard if you already are aware), if this part is to be installed for public use, you should be a licensed PE or SE and have all your material well documented. Welding should be in accordance with AWS D1.1.
Most of the time, the A27 or A148 grades will be OK, but the chemistry is not specified, so it can result in reduced weldability if the foundry put in a high carbon equivalent. A216 WCA/WCB/WCC have a specified chemistry range that ensures welability. In fact, the title of A216 says the castings are suitable for fusion welding.