BASIC THEORIES, Metallurgy, WELDING METALLURGY1 Comment

What is quenching?

September 17, 2023 Amarine Antonio

『𝐐𝐮𝐞𝐧𝐜𝐡𝐢𝐧𝐠 𝐚𝐬 𝐚 𝐇𝐞𝐚𝐭 𝐓𝐫𝐞𝐚𝐭𝐦𝐞𝐧𝐭』 ↳𝗤𝘂𝗲𝗻𝗰𝗵𝗶𝗻𝗴 is a vital heat treatment process used to rapidly cool a material, typically a metal alloy, from a high temperature to room temperature or below. ↳𝗠𝗲𝗰𝗵𝗮𝗻𝗶𝘀𝗺 𝗼𝗳 𝗤𝘂𝗲𝗻𝗰𝗵𝗶𝗻𝗴:1- 𝙃𝙚𝙖𝙩𝙞𝙣𝙜:The material is heated to a specific temperature, typically above its critical transformation temperature.2-𝙍𝙖𝙥𝙞𝙙 𝘾𝙤𝙤𝙡𝙞𝙣𝙜 & 𝙋𝙝𝙖𝙨𝙚 𝙏𝙧𝙖𝙣𝙨𝙛𝙤𝙧𝙢𝙖𝙩𝙞𝙤𝙣:Upon rapid cooling during quenching, the material undergoes a phase transformation depending on the composition of the material.The most common phase transformation associated with quenching is the formation of 𝙢𝙖𝙧𝙩𝙚𝙣𝙨𝙞𝙩𝙚, a hard and brittle phase characterized by a unique crystal structure (BCT). ↳𝗤𝘂𝗲𝗻𝗰𝗵𝗶𝗻𝗴 𝗠𝗲𝗱𝗶𝘂𝗺𝘀:Different quenching mediums have varying cooling … Continue reading What is quenching?

WELDING, Welding Engineer, WELDING METALLURGYLeave a comment

The project requires Killed Steel treatment on Pipe, Plate MTC.

November 8, 2019November 8, 2019 Amarine Antonio

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.

WELDING, Welding Engineer, WELDING METALLURGYLeave a comment

Stainless steel 347H and PWHT

November 4, 2019 Amarine Antonio

”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

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Hardness requirement in Sour service for (Duplex) Stainless steel

November 4, 2019 Amarine Antonio

Section 7, Table 7-11 of DNV Standard OS-F101 October 2010 – Submarine pipeline systems – provides HV10 limits for weldments in 22Cr and 25Cr duplex stainless steels for line pipes. For 22Cr and 25Cr duplex, the hardness in the weld and HAZ shall not exceed 350HV10 and the base material shall not exceed 290HV10 for 22Cr, and 330HV10 for 25Cr. Section 6, paragraph B201 of DNV Standard OS-F101 October 2010 states that materials shall be selected for compliance with ISO 15156. NORSOK Standard M-630 Rev.4 January 2004 – Material data sheets for piping – included material requirements in the form … Continue reading Hardness requirement in Sour service for (Duplex) Stainless steel

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Weld proximity, between two seams standard

November 3, 2019 Amarine Antonio

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

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Time delay before applying NDT in welding

November 3, 2019 Amarine Antonio

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

Metallurgy, WELDING METALLURGYLeave a comment

Austenite Stainless Steel at high-temperature (embrittlement)

November 3, 2019 Amarine Antonio

The phenomenon of embrittlement in austenitic stainless steel welds exposed to high temperature is accelerated by the presence of delta ferrite. To avoid solidification cracking in austenitic stainless steel welds, the composition of the filler material must be optimized to ensure that there is some delta ferrite present in the weld metal (typically >3%). However, delta ferrite transforms into intermetallic phases, notably the sigma phase, faster than austenite either during high-temperature service or during post-weld heat treatment (PWHT). Sigma phase is an intermetallic with an approximate chemical formula FeCr and, as with most intermetallics, it is very brittle and hence … Continue reading Austenite Stainless Steel at high-temperature (embrittlement)

Metallurgy, WELDING METALLURGY1 Comment

Duplex piping and seawater

November 3, 2019 Amarine Antonio

22%Cr duplex stainless steels are not suitable for elevated temperature unprotected seawater applications because they suffer from the crevice and pitting corrosion at even moderate temperatures. Super duplex stainless steels present superior corrosion resistance to duplex stainless steels in seawater applications, and provided weld quality is maintained, pitting should not occur in seawater up to about 40°C. The operational limit stipulated in the Norsok Standard (M-001, Rev.2, November 1997) is one of the most conservative for unprotected super duplex service and is more restrictive than most operators’ own requirements. The maximum operating temperature is set at 15°C and the maximum … Continue reading Duplex piping and seawater

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Stainless steel and PWHT – Post weld heat treatment

November 3, 2019 Amarine Antonio

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