Skip to main content

Structural fillet weld cracks - FCAW process, High Carbon Equivalent (CEq)

By Materials & Welding




  • presence of crack at weld root towards the beam side / section. This crack was observed along the weld toe area (beam side) as seen from the outer surface

  • CE for beam material was found to be higher than maximum permissible value as per ASTM A992
  • The beam side HAZ crack was observed to be initiated from weld root side. Crack was not observed to propagate in the parent metal instead it remained inside the HAZ area.
  • HV10 hardness at the HAZ area (beam side) was observed to be more (334-436) in both the examined cross sectional samples. Higher beam side hardness could be due to presence of needle shape widmanstatten ferrite and pockets of untempered martensite in the HAZ structure. High Carbon Equivalent (0.47) of beam section combined with insufficient pre-heat temperature during welding can increase the critical cooling rate and cause un-desirable high hardness microstructure in the HAZ area. Further if any diffusible hydrogen is present in the weld joint, it may increase the high hardness HAZ cracking propensity.
  • Further this high HAZ hardness (susceptible to cracking) combined with possible hydrogen level in the weld joint might have caused this HAZ crack starting from the weakest zone of incomplete weld root fusion in the fillet weld.
Recommendations:
Re qualify the welding procedure using high heat input, higher preheat (200 °C), and post heat at 200 °C for 2-4 hrs


Comments

Post a Comment

Popular posts from this blog

Materails FAQs

By Materials & Welding
Q: What are equivalents for standard Q 235 B (and Q 235 A) for U-channels? (asked by: boris.vielhaber@vait.com) A: DIN Nr. = 2393 T.2, 2394 T.2, EN 10025 W. Nr. DIN 17007 = 1.0038 Design DIN 17006 = RSt 37-2, S235JRG2 (Fe 360 B) Q: What is St DIN 2391 BK material? (asked by: dmcandrews@automaticstamp.com) A: Precision steel tubes, cold-finished/hard. Q: What is C.D.W. Boiler Tube? (asked by: montydude123@yahoo.com) A: Cold Drawn Welded Boiler Tube. Q: WHAT IS W.Nr. 1.4301? PLS TELL US IN EASY LANGUAGUE (asked...
21 comments
Read more

Heat tint (temper) colours on stainless steel surfaces heated in air // Heat tint

By Materials & Welding
Introduction The colour formed when stainless steel is heated, either in a furnace application or in the heat affected zone of welds, is dependent on several factors that are related to the oxidation resistance of the steel. The heat tint or temper colour formed is caused by the progressive thickening of the surface oxide layer and so, as temperature is increased, the colours change.   Oxidation resistance of stainless steels However, there are several factors that affect the degree of colour change and so there is no a single table of colour and temperature that represents all cases. The colours formed can only be used as an indication of the temperature to which the steel has been heated. Factors affecting the heat tint colours formed Steel composition The chromium content is the most important single factor affecting oxidation resistance. The higher the chromium, the more heat resistant the steel and so the development of the heat tint colou...
Post a Comment
Read more

Re: [MW:10788] ON PLOT PIPING & OFF PLOT PIPING

By Materials & Welding
Piping systems involved for the flow lines and gathering lines from the well head isolation valve to the production facility or processing plant isolation valve are determined as OFF PLOT. ON PLOT defines piping system in the processing plant and production platform. ANSI/ASME B31.4 applies for off plot piping system. B31.4 allows the use of either API 1104 or ASME section IX (as appropriate). However, occasionally, a very small system such as piping within 500 feet of a processing plant (some client also said 400 feet) may be declared B31.3 rather than B31.4. When B31.3 is invoked, only ASME Section IX is used. before you decide which code to use for welding procedure and/or welder qualification for pipe welding, you have to know the design and construction code applicable to the system. Please read far enough into scope and diagram illustrating the application of either B31.3 and B31.4 hope this helps rgds 2011/4/21 pradip kumar sil < pradipsil@gmail.com > Dear all, ...
Post a Comment
Read more