You need to be more specific on the Grade of 514. What exactly are the steels you intend to weld and the type of welding?
Yes, I have had certain grades of ASTM A 514 welded to itself and to ASTM A 572 with no problems. The welding needs to be performed with caution on certain grades of steel to avoid harming the intended mechanical properties of the steel.
22west;
Why are you using such a mismatch in yield/tensile strengths between the vessel (A 572) and heads A 514 Grade Q)? What is the function of the tank? Is it pressure-containing?
These materials are not really suitable for pressure-containing applications. ASTM A 514 Grade Q is a high strength, quenched and tempered steel plate that requires extreme caution for welding. This material is sensitive to cracking during post weld heat treatment.
If you intend to build a pressure retaining tank, I would use pressure vessel quality steel plate that has improved weldability versus high strength structural steel.
It is not a pressure vessel. It is a structural design, I only used a tank analogy to better expain the geometry.
The "cap" or the high strength steel plate is stressed in the middle due mechanical loading - not pressure loading.
You mentioned A514 cracking sensitivity during post weld heat treatment, is this true for welding that steel in general or only when welded to a dis-similar material (sauch as A572)?
I would like to read up a little on this A514 cracking sensitivity can you recommend a book?
22west;
Ok, I thought otherwise when I saw the word tank and high strength steels in your OP. Well, the ASTM A 514 Grade Q steel plate can crack during a post weld heat treatment because this plate contains vanadium, regardless if welded to itself or to another material. Vanadium is added to increase (ambient and elevated temperature) strength and typically renders a steel more susceptible to cracking during post weld heat treatment (PWHT); the term is also called reheat cracking. This is the reason why I raised the red flag cautionary statement.
What happens is that during PWHT of the A 514 Grade Q plate to relieve residual stresses and to reduce the hardness of weld and of the base metal heat affected zone from welding, vanadium forms carbides that significantly strengthen the metal grains along the base metal heat affected zone of the weld. Upon exposure to elevated temperature for PWHT, the grain boundaries of the steel are weaker than the grains themselves because of the vanadium carbides, thus promoting cracking along the grain boundaries to relieve the residual stresses, instead of the material absorbing these stresses.
If you must use the higher strength A 514 Grade Q steel plate for the end caps, I would qualify a welding procedure using the combination of A 572 and A 514 with PWHT. The selection of PWHT should be 1100 deg F, which is about 50 deg F less than the original fabrication heat treatment (min 1150 deg F) for this material.
You need to use low hydrogen weld electrodes and keep the interpass temperature during welding at or below 450 deg F. Your preheat should only be 150 deg F if at or under 1.5” in plate thickness. Over this thickness, I would increase the preheat to 250 deg F. The ASTM A 572 Grade 50 is readily weldable.
You filler metal should be E10018-x for this weld procedure qualification.
metengr,you conclude by recommending that the "filler metal should be E10018-x for this weld procedure qualification." But what of the provisions of D1.1 Sec 3.3 for undermatching relationships, which permits use of fller metal for lower strength group? Does this not mean E7015,16 or 18 will be more appropriate per AWS D1.1 table 3.1?
henri2;
Agreed, that the lower strength filler metal is certainly appropriate. I don't have D1.1 handy. I believe the decision to use the lower strength filler metal is left up to the Design Engineer for the specific application. As long as the filler metal is of equal or greater strength in joining two dissimilar strength materials, E7018 would work. Some Design Engineers prefer to have the weld metal strength match the higher strength base material.
The lower strength is recommended because the higher-strength materials are more brittle, and considering that it doesn't do you any good to have your weld higher strength than adjacent material, you are sacrificing ductility for no good reason.
Would ASTM A 709 Gr. HPS 70W be suitable for your application? It's supposed to be more weldable than A 514.
Metengr,
I would like to take some exceptions to your welding procedures. Never have a temperature over 500° if you hope to maintain the 100ksi strength of A514. Yes controlling pre heat and post weld cool down is important, but not super critical. A514 is similar to 8620, without Q&T.
We weld a lot of high strength heat treated steels used in logging and construction. The best results are with an E80SD2 solid wire with 75-25 shield gas for most temperatures. Several smaller passes rather than one large one will work better. If you are using the materials below -20F you should contact a welding wire manufacture for another choice.
Why would you use A514 if you didn’t need the 100ksi strength? We have seen many places where welding high strength materials with lower strength fillers end up with fatigue cracks in the center of the weld.
Links:
Never have a temperature over 500° if you hope to maintain the 100ksi strength of A514. Yes controlling pre heat and post weld cool down is important, but not super critical.[/quote Danzer]
I believe I addressed this in an earlier post as interpass should NOT exceed 450 deg F. Preheat should not exceed 150 deg F. We are in agreement up to your last comment not being supercritical, there is no such variable. You have essential variables in welding, in my humble opinion interpass and preheat are essential variables for high strength materials.
Danzer said:
We weld a lot of high strength heat treated steels used in logging and construction. The best results are with an E80SD2 solid wire with 75-25 shield gas for most temperatures.[/quote Danzer]
I only dealt with the SMAW process as an example, your filler metal above is acceptable to me.
Danzer said:
Why would you use A514 if you didn’t need the 100ksi strength? We have seen many places where welding high strength materials with lower strength fillers end up with fatigue cracks in the center of the weld.[/quote Danzer]
I believe I had asked a similar question in an earlier post. Lower strength fillers metal or under matched filler metals serve their purpose, and must be considered in suitability for design.
