Chromium carbides form in stainless steels along either side of a weld. These carbides form where the metal is in the temperature range of approximately 1100 – 1500 F. Since the weld pool is well above this temperature and the base metal is below it, there is always some part of the welded part which was in that temperature range. The quantity of carbides which form depends on several factors,
Welding Procedures are the guidelines used to perform a weld. They are designed to provide a record of the welding variables used and the inspection results obtained during the procedure qualification test. They can also provide the instructions for the welder to use in production in order to produce acceptable welds. Usually welding procedures are developed in accordance with a welding code or standard,
Induction Heating The most common methods for achieving a more controlled preheat temperature are induction heating and electrical resistance heating. “The equipment used for induction is considerably more expensive than that used for electrical resistance heating,” said Fong. “However it does get your steel hotter quicker. It still offers you much more control than what you
Overview of Hydrostatic Testing Hydrostatic (Hydro) Testingis a process where components such aspipingsystems, gas cylinders, boilers, andpressure vesselsare tested for strength and leaks. Hydro tests are often required after shutdowns and repairs in order to validate that equipment will operate under desired conditions once returned to service. Furthermore, hydrostatic
Hydrostatic testing of the pipeline including riser should follow the below procedures: The pressure should be raised to the test pressure and allowed to stabilize then held for 15 minutes. The rate of pressure increase should not exceed 100 kPa (15 psi) per minute during all operations. The pressure should be lowered to approximately 25 percent of test pressure, allowed to stabilize then
Ageing or Precipitation hardeningA low temperature heat treatment designed to produce the correct size and distribution of precipitates, thereby increasing the yield and tensile strength. It is generally preceded by a solution heat treatment. For steel, the temperature may be somewhere between 450-740 degree C, an aluminium alloy would be aged at between 100-200°C. Longer times and/or higher
Preheating involves heating the base metal, either in its entirety or just the region surrounding the joint, to a specific desired temperature, called the preheat temperature, prior to welding. Heating may be continued during the welding process, but frequently the heat from welding is sufficient to maintain the desired temperature without a continuation of the external heat source. The interpass temperature,
Once you have determined that the welding application requires preheating, consider the best method to use. Induction heating is one preheat option that provides consistent heat throughout the weldment. It offers fast time-to-temperature and is considered a very safe option for preheating. Photo courtesy of Miller Electric Mfg. Co. Preheating with an open flame from a torch is
One of the most common uses of nondestructive testing (NDT) is the examination of weld integrity. This is because welds are extraordinarily common in critical industrial applications across the world. The ability to inspect welds nondestructively is essential, as destroying one for testing necessitates replacing it with a new, untested weld. As such, there has been significant technological development
Construction Codes & Significance Postweld heat treatment on the weld of ASTM A335 P11 seamless pipes. The heat treatment is performed by a flexible ceramic pad heater. Seamless pipes made of low-alloy steel ASTM A335 Grade P11 can be used for power piping (ASME B31.1) or process piping (ASME B31.3) at elevated temperatures. After joining the two ASTM A335 P11 pipes together by a welding
Weldingis an essential part of operating and maintaining assets in the petroleum (upstream, midstream, downstream) and chemical processing industries. While it has many useful applications, the welding process can inadvertently weaken equipment by imparting residual stresses into a material, leading to reduced material properties. In order to ensure the material strength of a part is retained
Preheating Heat treatment of welds is a critical activity which needs to be carried out before and after the welding process. Heat treatment before welding (Preheating) is necessary to bring the base weld metal at proper temperature. No welding shall be performed without preheating the joint to 10°C (50°F) when the ambient temperature is below 10° C. Preheating requirements for
The descriptive term provides an important clue, so we're ready to take a guess at the role this test technique plays. Being engineers, however, there's no room for guessing, so let's get the explanations down in black-and-white right now. Hydrostatic testing, as utilized on a pressure vessel, uses water as a seal inspection medium. It is Technically a Non-Destructive Test Technique Pressurized
Hydrostatic test Ahydrostatic testis a way in whichpressure vesselssuch aspipelines,plumbing,gas cylinders,boilersand fuel tanks can be tested for strength and leaks. The test involves filling the vessel or pipe system with a liquid, usually water, which may be dyed to aid in visual leak detection, and pressurization of the vessel to the specified
Post-weld heat treatment or PWHT is a controlled process that involves reheating the metal below its lower critical transformation temperature, following a welding process. The material is then held at the elevated temperature for a predetermined period of time to alleviate residual stresses, increase the strength, increase or decrease the hardness, and reduce the risk of cracking by microstructural
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