EPRI’s work on nuclear piping materials had as its primary objective the evaluation of whether current requirements for postweld heat treatment (PWHT) exemption for carbon steel thicknesses could be relaxed based on industry experience rather than technical data or design calculations.<\/p>\n
PWHT is used to eliminate residual stresses in thick-walled components, improving their dimensional stability and performance. The carbon steel thickness requirement varies significantly across codes due to their inherent Charpy toughness criteria.<\/p>\n
Carbon steel’s high chromium content renders it highly corrosion resistant, making it the ideal material choice for structures in harsh environments. Unfortunately, its hardness reduces dynamic and static load ratings and requires larger dimensions and additional bearing blocks.<\/p>\n
Humidity, temperature, rain, wind and air impurities accelerate atmospheric corrosion. Furthermore, metal wet times should also be carefully considered when planning metal restoration work.<\/p>\n
Traditional outdoor exposure tests and corrosion big data evaluation method were employed to study the different corrosion behavior between Q235 carbon steel and Q420 weathering steel, as demonstrated in figure 4. It shows the cumulative electric quantity curves for both types of steel at Qingdao and Hangzhou; one can observe that carbon steel’s rust layer has many pits and bumps while that of weathering steel is denser, with an inner protective layer to block Cl- from penetrating its metal substrate, making this type more resistant to atmospheric corrosion.<\/p>\n
Many applications of carbon steel plate require it to withstand considerable amounts of stress, with material standards setting out minimum values for yield strength and ultimate minimum tensile strength. Steels that meet BS EN 1993-1-4’s specifications meet this criteria as well.<\/p>\n
Higher carbon levels increase strength and hardness of steel plates; however, higher levels of carbon also decrease ductility, making the steel less suited to stretching without cracking or breaking.<\/p>\n
Low carbon steel (sometimes known as mild steel) is the most ductile type of carbon steel and widely used in construction and manufacturing. High carbon steel offers excellent strength and hardness but is more difficult to machine or shape; copper-bearing high carbon steels on the other hand, can offer two to four times stronger plates while still offering good ductility.<\/p>\n
Carbon steels generally possess low temperature toughness due to the presence of manganese; however, by adding elements like boron, vanadium and niobium it is possible to increase toughness. This may reduce the risk of hydrotest fracture failures during operation of pressure components and hydrotest procedures; fracture mechanics analyses indicate that PWHT becomes necessary as strength increases alongside Charpy test energy requirements (for proportional flaw sizes).<\/p>\n
Pre-weld heat treatment (preheating), also known as preheating, involves raising the base metal temperature prior to welding to minimize thermal gradients and hydrogen-induced cracking. Postweld heating treatment (postheating) applies controlled heat after welding to relieve residual stresses, temper hardened zones, improve material properties, relieve residual stresses, temper hardened zones and improve material properties. PWHT should typically take place for 1 hour per 25 mm (1 inch of weld thickness with an evenly controlled cooling rate in order to avoid thermal shock while helping maintain weld quality for strong and durable welds.<\/p>\n
Carbon Steel welding techniques make it an attractive option for many fabrication projects, making it a popular choice. To produce high-quality weld bead and reduce distortion or shrinkage, proper weaving and root pass techniques must be utilized. They help distribute heat evenly while simultaneously guaranteeing weld and base metal bonding properly.<\/p>\n
To produce high-quality welds, welding carbon steel requires pre and postweld heat treatments. Preheat heat treatment, commonly referred to as preheating, applies controlled heat before welding to reduce thermal gradients and hydrogen-induced cracking in the weld arc zone (HAZ). Postweld heat treatment (or postheat treatment) is used after welding as an aftercare measure to relieve residual stresses, harden zones and increase mechanical strength.<\/p>\n
ASME Section VIII Div. 1 and its Tables UCS-56-1 through UCS-56-11 detail the requirements for preheating and postweld heat treating carbon steels according to ASME Section IX; specifically these tables provide heating cycle data necessary for PWHT depending on their P Number or Gr. Number category as listed by ASME; they also include notes regarding exemptions or possible substitute treatments.<\/p>","protected":false},"excerpt":{"rendered":"
\uc6d0\uc790\ub825 \ubc30\uad00 \uc7ac\ub8cc\uc5d0 \ub300\ud55c EPRI\uc758 \uc5f0\uad6c\ub294 \uae30\uc220 \ub370\uc774\ud130\ub098 \uc124\uacc4 \uacc4\uc0b0\uc774 \uc544\ub2cc \uc5c5\uacc4 \uacbd\ud5d8\uc744 \ubc14\ud0d5\uc73c\ub85c \ud0c4\uc18c\uac15 \ub450\uaed8\uc5d0 \ub300\ud55c \ud604\ud589 \uc6a9\uc811 \ud6c4 \uc5f4\ucc98\ub9ac(PWHT) \uba74\uc81c \uc694\uac74\uc744 \uc644\ud654\ud560 \uc218 \uc788\ub294\uc9c0 \ud3c9\uac00\ud558\ub294 \uac83\uc744 \uc8fc\uc694 \ubaa9\ud45c\ub85c \uc0bc\uc558\uc2b5\ub2c8\ub2e4. PWHT\ub294 \ub450\uaebc\uc6b4 \ubcbd\uc73c\ub85c \ub41c \ubd80\ud488\uc758 \uc794\ub958 \uc751\ub825\uc744 \uc81c\uac70\ud558\uc5ec \uce58\uc218 \uc548\uc815\uc131\uc744 \ud5a5\uc0c1\uc2dc\ud0a4\ub294 \ub370 \uc0ac\uc6a9\ub429\ub2c8\ub2e4 ... <\/p>\n