Preheating of Weld Joints

Normally we don´t Preheat P4 under 19mm. Over 19mm we use 120º to 150ºC (Torch). Try to use an RT random (5%) to verify the required GAP and make full hardness test. Maybe enough for your client. Cut and Re-welded can be Harmful. WP

Socket joints for 1" size pipe in SA335 P11 do not need pre-heat. Even radiography will not be of much help. It seems that you do not have approved WPS and ref. PQR, but you can reffer some PQR relevent to this material and this type of joint from some other project to convince your client. Cutting and re-welding is not the solution.

preheating is used to prevent stress fractures from sudden temperature changes. annealling by slowly cooling the weld with heat "a torch" would be approppriate on a small pipe.; block both ends of the pipe in order to maintain welding temperatures.

NO NEED FOR PREHEAT REFER PROCESS PIPING ASME B 31.3 TABLE 330.1.1 PREHEAT TEMPERATURES IT SAYS P11 MATERIAL MINIMUN AND MAXIMUM TEMPERATURE FOR ALL THICKNESS ONLY 10 DEGREE CEL.

you can spout all the specs you want too. will it pass the test is the question.

P11 type Cr-Mo steels are air hardening steels and undergo micro structural transformations that depend on the rate of cooling from above the upper critical temperatures.The mechanical properties are dependent on these transformations..

With faster cooling rate, strength,and hardness increase and ductility is reduced. However, because of lower carbon content (0.15 % maximum) carbides are present in limited amounts and the results in higher ductility at any given strength level than obtained from high-carbon steels.

When the steels with 2,25Cr - 1% Mo and above get heated above their transformation temperatures in operations like rolling, forging, hot forming, welding etc., with consequent loss in ductility and toughness due to their air hardening characteristics, they require further heat treatment, to restore these useful mechanical properties. Lack of Pre heat and post heat treatment may produce cracking in the weldment.

For 1/2 Cr-1/2 Mo. recommended pre heat temp. is 50⁰C up to 13.0 mm thickness. For 1 Cr-1/2 % Mo & 1.25Cr-1/2% Mo, it is 120⁰C for same thickness. Hence, if they are not pre heated, it may not create much problems. The temperature would have reached up to that level during welding. A NDT and hardness check may give you an indication to you towards its quality.

Still the joints can be post weld heat treated at 600-720⁰c if required (or) insisted up on. A post NDT may may be done if needed later.

sridhar.

What are the Project Speifications and Codes ?

In your post you have stated "SOME joints of ASME SA 335 P11 material were welded with out preheating", i think the question is what did the customer ask for what were the specifications you were given for the job. If you followed them no problem if you didnt well the customer should expect to get what they pay for.