Dear Rithvik,
In duplex stainless steel (DSS) or super duplex stainless steel (SDSS) welding, the terms "hot pass" and "cold pass" refer to specific stages of the welding process:
Hot Pass: The hot pass is the second pass in the welding sequence, following the root pass. It is typically performed using the same consumable as the root pass, and its purpose is to ensure proper fusion and penetration while maintaining the desired root profile. The hot pass is usually deposited at a higher heat input compared to subsequent passes, ensuring thorough mixing of the filler metal with the base metal and promoting good mechanical properties.
Cold Pass: The cold pass, on the other hand, is one of the subsequent filler passes deposited after the hot pass. It is called a "cold pass" because it is applied at a lower heat input compared to the hot pass. The cold pass helps to refine the weld profile, control the size and shape of the weld bead, and minimize the risk of excessive heat input that could lead to distortion or other welding defects.
When performing DSS pipeline welding, using SDSS consumables for the root pass and DSS consumables for the subsequent passes is a common practice. This approach is primarily employed to optimize the welding process for the following reasons:
Root Pass with SDSS Consumable: SDSS consumables are often used for the root pass because they offer better resistance to hot cracking and solidification cracking in the weld root, especially in high-heat input situations. SDSS filler materials are designed to provide adequate penetration and fusion while minimizing the formation of detrimental phases in the weld root, such as sigma phase. This helps ensure a sound and defect-free root weld.
Rest of the Passes with DSS Consumable: Once the root pass is completed successfully with SDSS consumables, switching to DSS consumables for the subsequent passes is done to maintain consistency in mechanical properties and corrosion resistance throughout the weld joint. DSS consumables are chosen for their compatibility with the base metal and their ability to provide the required mechanical strength, corrosion resistance, and weld quality in the completed weld joint.
By using SDSS consumables for the root pass and DSS consumables for the remaining passes, welders can achieve optimal results in terms of weld quality, mechanical properties, and corrosion resistance in DSS pipeline welding applications.
Best regards,
AB
When stringent like G48 Corrosion test -weight loss (< 1 gm )test is imposed by Client specification, then overalloyed TYP 2594 is deployed to meet stringent corrosion rate requirements--ThanksVishwasIWE9823472273Sent from my iPhoneOn 16 May 2024, at 3:28 PM, 'james gerald' via Materials & Welding <materials-welding@googlegroups.com> wrote:Hot pass to be welded immediately after welding Root pass at higher Heat Input as specified by API 1104 for pipelines where time between root and hot pass is an essential variable. for CS & LAS.IN DSS cold pass to be welded in single bead at 75% of the Root pass Heat Input to avoid over heating of root which may lead to formation of secondary austenite and intermetallic phases like Sigma phase etc.. which results in failure of ASTM G48 tests.<1715852094407blob.jpg>Thanks & Regards
J.Gerald Jayakumar
0091-8838619635
--On Thursday, 16 May, 2024 at 02:23:17 pm IST, RITHVIK Suresh <rithviksuresh98@gmail.com> wrote:Dear Experts,1.Can anyone tell me what is meant by Cold pass in Dss/Sdss welding. Also please tell me the difference between Hotpass and Cold pass.2.In DSS Pipeline welding Root pass is being performed with SDSS consumable and rest is performed with DSS consumable. Can anyone explain me why it is performed like thisThank youRithvik--
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