Any feedback or suggestions on preheat for 1" or greater plate?
I am looking for methodes, means, general thoughts and ideas for structual steels of various compostions and grades with the goal of avoiding high hardness (cracking) while reducing the cost of preheating and maintaining good toughness properties.
Any thoughts?
Check AWS D1.1/D1.1M:2000 - 3.5, 3.5.1, 3.5.2 and table 3.2
Mike Sherman
Shermans Welding
I agree with Mike,
There are preheat and interpass temp charts (Table 3.2)for all groups of materials for structural application. Temp sticks are available to check preheat and interpass temps, simply mark the steel within 3" of the joint with the temp stick and if it melts, you have enough heat in it.
John Wright
Use the recommendations in the code you are working.
If not working to any particular code, carbon content is a good guide. We have had good luck with a preheat that is "1000 x carbon content" as a minimum. An example would be 4150 steel with a .5 carbon content.
1000 x .5 would give a minimum preheat of 500 deg F. Add more preheat for complex or highly restained joints. Remember, preheat is usually measured 3" from the weld area to ensure the metal is "soaked" or completely up to temperature.Lincoln Electric also has a good slide rule type calculator that is relatively cheap. You might want to give that a try.
brande
Hydrogen cracking has been a topic since the 30´s. It has been extensively covered in many, many books and reports. However, the physical mechanism for hydrogen cracking is still under debate.
The weld metal or heat affected zone (HAZ) hardness and the carbon equivalent are only two components in complex problem. You've also got to take stuff like hydrogen input, diffusion, oxygen ito consideration.
A very good book on the subject is "Welding steels without hydrogen cracking". I've included a link to ASM´s bookstore in the end of this post.
The book decribes the problem and several ways to combat hydrogen cracking for a varerity of steel-types. Hence, the book can be used for attaining a deeper understandment of the problem as well as combating
cracking on the factory floor.
I'm not familiar with your standards, but I think standards alone won´t help You to really UNDERSTAND hydrogen cracking
Best Regards
Happywelder
EWE
http://www.asminternational.org/Template.cfm?Section=BrowsebyTopic&template=Ecommerce/ProductDisplay.cfm&ProductID=11464
Are you asking about various alternatives to get the heat energy into the plate? I'm not sure if you want to discuss torches, fuels, and similar alternatives or if the question is a metalurgical one, or both.
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