Fully killed is the term to describe de-oxidized steel. After the steel is made, it is then poured into the continuous caster to make a long slab of steel. Think of a sausage maker – molten steel goes in at the top and rectangular slab comes out the bottom. This is called casting. During casting, small carbon monoxide bubbles can form between the steel grains if the oxygen is not removed. If you’ve ever painted a door and seen bubbles in the paint once you apply it you’ll recognize the similarities. To stop these bubbles appearing you paint slower, but … Continue reading The project requires Killed Steel treatment on Pipe, Plate MTC.
”In the welded condition many stainless steels are susceptible to rapid intergranular corrosion or stress corrosion cracking. This is because the heat from welding sensitizes the base metal heat affected zone (HAZ) and the weld. Sensitization is the condition where chromium carbide precipitation at the grain boundaries (from a heating process, e.g., welding, hot forming, hot bending, service temperature, etc.) reduces the amount of chromium in solution in the stainless steel. The temperature range for sensitization to occur for austenitic stainless steels is approximately 700 °F to 1500 °F. Since the carbides precipitate in the HAZ or weld deposit at … Continue reading Stainless steel 347H and PWHT
If welding is to be performed according to a welding procedure specification, it is possible that changing the electrode manufacturer will invalidate the approval of the procedure to the code/standard on which it was based. The manufacturer or ‘trade name’ of the electrode can be classed as an essential variable in a given weld procedure. The extent to which re-qualification is necessary will vary from code to code. For example, in EN ISO 15614-1 and in the UK standard BS 4515:2004, approval is only restricted to the specific make of electrode if impact testing is required as part of the procedure qualification. On the … Continue reading Change electrode manufacture, vendor in welding WPS.
There are tests for plastic welds, below is a selection of relevant tests. EN 12814-1:1999: ‘Testing of welded joints of thermoplastics semi-finished products – Part 1: Bend test’ EN 12814-2:2000: ‘Testing of welded joints of thermoplastics semi-finished products – Part 2: Tensile test’ EN 12814-3:2000: ‘Testing of welded joints of thermoplastics semi-finished products – Part 3: Tensile creep test’ EN 12814-4:2001: ‘Testing of welded joints of thermoplastics semi-finished products – Part 4: Peel test’ EN 12814-5:2000: ‘Testing of welded joints of thermoplastics semi-finished products – Part 5: Macroscopic examination’ EN 12814-6:2000: ‘Testing of welded joints of thermoplastics semi-finished products – … Continue reading Plastic (PPE, HDPE) welding standards
Weld proximity is covered by a number of international standards. Extracts from these standards are shown below and summarised in the following table: Standard Applies to Minimum distance between weld toes Notes BS 2633:1987 Ferritic steel pipework 4t t= nominal thickness of the pipe See below for notes on attachment welds. BS 4515:2009 C-Mn pipelines 4t t= pipe thickness BS 2971:1991 Carbon steel pipework Agreed by parties – PD 5500:2012 Pressure vessels 4e or 100mm whichever is greater e= design thickness Refers to the staggering of longitudinal welds ASME B&PV Boilers and pressure vessels Not specified – BS 2633 ‘Class I … Continue reading Weld proximity, between two seams standard
The following standards stipulate delay time before inspection: BS EN 1011-2:2001 Welding – Recommendations for welding of metallic materials – Part 2: Arc welding of ferritic steels (with amendment AMD 14926 Feb 2004) Paragraph 18 states: ‘Due to the risk of delayed cracking, a period of at least 16 hours is generally required before the final inspection is made of as-welded fabrications. The minimum time may be reduced for thin materials below 500N/mm2 yield strength or increased for materials of a thickness greater than 50mm or of yield strength over 500 N/mm2 … Welds that have been heat-treated to reduce hydrogen content … Continue reading Time delay before applying NDT in welding
Most austenitic stainless steel weldments do not require post-weld heat treatment. For those that do, the heat treatment temperature should reflect the particular concern that is being addressed. The necessity for any type of heat treatment of austenitic chromium-nickel steel weldments depends largely on the service conditions encountered. For some applications, heat treatment is used to impart the greatest degree of corrosion resistance possible, eg by solution treating to homogenize the composition or stabilizing, to minimize the risk of sensitization during subsequent elevated temperature exposure. In other applications, heat treatment may be used for stress relieving. This may give more … Continue reading Stainless steel and PWHT – Post weld heat treatment
Oxidation of the root bead and adjacent HAZ during welding of stainless steels is commonly called heat-tint. A chromium-rich scale is formed, which is typically not very protective, and the stainless steel surface becomes chromium-depleted: these effects may impair the corrosion resistance of stainless steel welds. Tests performed in various corrosive environments have shown that susceptibility to pitting and crevice corrosion is greater when the surface is heat-tinted, and the colour of the heat-tint is an indicator of the degree of susceptibility to corrosion. For example, purple-blue oxides are generally the most susceptible to corrosion attack. The critical pitting temperature, … Continue reading Blue colour when welding Stainless steel
Austenitic stainless steels with around 10-12% nickel (e.g. grades 304, 316, 321 and 347) are predominantly non-magnetic due to the face centered cubic (fcc) crystal structure of the austenite phase, which imparts so-called ‘paramagnetic’ (i.e. non-magnetic) behavior. Although a number of second phases, e.g. inclusions or ferrite stringers, may exist in wrought austenitic stainless steel products, the structure is almost exclusively made up of the austenite phase and hence they are essentially non-magnetic. However, weld metals made with filler metal compositions matching the 300 series austenitic steels (e.g. 308, 309, 316 and 347 types) are designed to have a small … Continue reading Stainless steel become Magnetic (304, 316, 321, 347 series)