1. Bere a wɔreyɛ pressure vessels no, wɔde ɔhaw ahorow a edidi so yi bɛba: awɔw adwuma a ɛyɛ den a awɔw a ɛkɔ soro dodo, awɔw a wɔde teɛteɛ mu ne adwumayɛ afoforo a ɛyɛ nwini na ɛde ba. Nsakrae a ɛba wɔ nhyehyɛe ne agyapade a ɛwɔ weld beae a welding de ba no mu. Adwennwene a aka a welding ne awo ntoatoaso ne nkɔso a ɛba wɔ adwennwen mu mpaapaemu a ɛde ba no ba. Sɛ welding pressure vessels, sɛ ɔhyew gradient a ɛyɛ nnam a ɛwɔ ɔhyew nsonsonoe a ɛboro digrii 100 ba wɔ mmeae a ɛbɛn awofo nneɛma no a, plastic strain a ɛnyɛ pɛpɛɛpɛ no ba wɔ ferritic steel anaasɛ nneɛma afoforo a ɛne no sɛ, na wɔ cooling adeyɛ a edi hɔ no mu no, residual stress field a adwennwen a ɛsen biara no adu aba no ho. Bio nso, plastic a ɛnyɛ pɛpɛɛpɛ a ɛwɔ nhyɛso ntini a wɔyɛ mu no ma nneɛma a aka wɔ elastic-plastic nneɛma mu, na nea aka no betumi ayɛ mfiri (titiriw awɔw a ɛyɛ nwini, awɔw a ɛyɛ nwini ne adwumayɛ afoforo a ɛyɛ nwini) ɔhyew (titiriw a welding kwan no ma ɛba), anaasɛ abien no nyinaa, kyerɛ sɛ, thermomechanical ntease ahorow. Enti, wobegyaw residual elastic strain field wɔ ade a etwa to no mu bere a wɔayɛ nhyɛso anwenne no ho adwuma awie no, na wɔde bɛhyɛ elastic residual stress a ɛne no hyia no ase. Nhyɛso a aka a ɛwɔ hɔ no bɛka nhyɛso anwenne no adwumayɛ. Sɛnea ɛbɛyɛ a wobeyi nhyɛso a ɛsen biara a ɛwɔ welding beae no afi hɔ na wɔadu botae a ɛne sɛ wɔbɛkyekyɛ emu nhyɛso no pɛpɛɛpɛ no ho no, wobetumi afa akwan horow so, te sɛ mfiri a wɔde wosow, post-weld ɔhyew kwan, ne nea ɛkeka ho Nanso, esiane sɛ ɔhaw ahorow pii a ebetumi aba wɔ nhyɛso ntini mu no fi dade a wɔsɛe no wɔ weld beae no mu titiriw nti, mfiri akwan a wɔde di dwuma no betumi ama ɔhaw ahorow pii atumi asiw ɔhaw ahorow a ɛbɛba no ano bio no nyɛ nea ɛbɛma wɔasiw ɔhaw ahorow a ɛbɛba no ano bio. Nea ɛka ho no, dade ahorow a ɛyɛ hydrogen embrittlement phenomenon no atwetwe adwene kɛse. Sɛ hydrogen hyɛn dade mu wie a, mfiridwuma mu nneɛma no bɛsɛe kɛse. Ahoɔden ne plastic a ɛwɔ mu no so tew kɛse, na hydrogen a ɛwɔ dade lattice no mu no ma dade no di huammɔ bere a ɛreyɛ mmerɛw nkakrankakra no. Wobetumi atwe hydrogen a ɛwɔ dade ade no mu bere a wɔreyɛ dade ade no, te sɛ hydrogen a dade a ɛyɛ nsu no twetwe bere a wɔreyɛ welding no na wɔakora so wɔ weld no mu, anaasɛ ebetumi ayɛ hydrogen a ade a ɛwɔ hydrogen tebea no mu no twetwe. For the hydrogen absorbed in the weld, the more effective elimination method is to perform post-weld heat treatment, which can not only relax and alleviate the welding residual stress, improve the weld heat affected zone that is hardened and embrittled due to welding, and improve the ductility and fracture toughness of the weld metal, but also diffuse and escape harmful gases such as hydrogen in and near the Welding beae. Ɔhyew ayaresa akwan abien na ɛwɔ hɔ a wɔde di dwuma wɔ nhyɛso ntini mu: biako ne ɔhyew a wɔde yɛ adwuma de ma mfiridwuma mu nneɛma tu mpɔn, na biako nso yɛ post-weld ɔhyew ayaresa (PWHT). Wɔ ntease a ɛtrɛw mu no, post-WELD ɔhyew ayaresa yɛ ɔhyew ayaresa a wɔde yɛ welding beae anaasɛ welded components bere a wɔde weld ayɛ adwuma no awie no. Nneɛma a ɛwɔ mu no bi ne adwennwen ano aduru, annealing a edi mũ, ano aduru, normalising, normalising ne tempering, tempering, low-temperature stress relief, precipitation heat treatment, etc. Wɔ ntease ketewaa bi mu. na afã horow a ɛfa ho no yɛ hyew pɛpɛɛpɛ na ɛyɛ pɛpɛɛpɛ wɔ dade phase nsakrae ɔhyew beae no ase, na afei ɛyɛ nwini pɛpɛɛpɛ. Mpɛn pii no, post-WELD ɔhyew ayaresa a wɔaka ho asɛm no titiriw yɛ post-weld stress relief heat treatment.
. Ma plasticity a ɛwɔ weld metal no mu no nyɛ yiye. b. Tew ɔhyew a ɛwɔ ɔhyew mu-beae no so. c. Ma fracture toughness tu mpɔn. d. Ma ɔbrɛ ahoɔden tu mpɔn. e. Sane fa ba anaa ma aba a ɛso tew wɔ awɔw bere mu no yɛ kɛse. 4. ma tumi a ɛma adwennwen a ɛyɛ mmerɛw no tumi ko tia no tu mpɔn. 5. foforo gyae mframa a epira wɔ weld dade no mu, titiriw hydrogen, na amma mpaapaemu a ɛkyɛ no amma.
3. Atemmuo a ɛfa hia a PWHT hia ho: sɛ ebia nhyɛsoɔ anwenneɛ no hia post-WELD ɔhyew ayaresa no pefee wɔ nhyehyɛɛ no mu, na mprempren nhyɛsoɔ anwenneɛ nhyehyɛɛ no ho nkyerɛkyerɛmu no wɔ ahwehwɛdeɛ ma yei. Wɔ welded pressure vessels ho no, adwennwene kɛse bi wɔ welding beae no, na nsunsuanso bɔne a efi adwennwen a aka no mu ba no da adi wɔ tebea horow bi mu nkutoo. Sɛ adwennwene a aka no ne hydrogen a ɛwɔ weld no mu no bom a, ɛbɛma ɔhyew-beae no ayɛ den, na ɛde mpaapaemu a ɛyɛ nwini ne mpaapaemu a ɛkyɛ aba. Sɛ wɔde static stress a aka wɔ weld no mu anaasɛ dynamic load stress a ɛwɔ load operation no mu no ka corrosive effect a ɛwɔ medium no mu no bom a, ebetumi ama crack-te sɛ corrosion, a ɛyɛ SO-a wɔfrɛ no stress corrosion. Welding residual stress ne awofo nneɛma a ɛyɛ den a welding de ba no yɛ nneɛma a ɛho hia wɔ awo ntoatoaso a ɛyɛ adwennwen a ɛpaapae mu. Nhwehwɛmu no mu aba no kyerɛ sɛ nkɛntɛnso titiriw a deformation ne residual stress nya wɔ dade nneɛma so ne sɛ wɔbɛdan dade no afi corrosion a ɛyɛ pɛ so akɔ local corrosion, kyerɛ sɛ, intergranular anaa transgranular corrosion. Nokwarem no, dade a ɛyɛ corrosion cracking ne intergranular corrosion nyinaa ba wɔ media a ɛwɔ su ahorow bi ma saa dade yi. Sɛ adwennwene a aka wɔ hɔ a, sɛnea corrosion sɛe no teɛ no betumi asesa a egyina sɛnea nneɛma a ɛyɛ corrosive medium no te, ne dodow ne ne hyew so, ne sɛnea wɔahyehyɛ, sɛnea ɛte, sɛnea ɛwɔ soro, adwennwen tebea, ne nea ɛkeka ho a ɛwɔ ɔwofo ade ne weld beae no. Sɛ ebia welded pressure vessel no hia post-WELD ɔhyew ayaresa no gyina atirimpɔw, kɛse (titiriw ɔfasu no mu duru), nneɛma a wɔde di dwuma no adwumayɛ, ne adwumayɛ tebea horow so. Ɛsɛ sɛ wosusuw post-WELD ɔhyew ayaresa ho wɔ tebea horow a edidi so yi mu biara mu: 1. Tebea a emu yɛ den a wɔde di dwuma, te sɛ nsu a ɛyɛ den-nkuruwa a ɛwɔ asiane mu a asiane wom sɛ ɛbɛpaapae wɔ ɔhyew a ɛba fam mu, ne nsukorade a ɛso adesoa akɛse ne adesoa a ɛsesa. 2. wellded pressure vessels a ɛboro anohyeto bi so. Nea ɛka ho ne boilers, petrochemical pressure vessels, ne nea ɛkeka ho, a ɛwɔ mmara titiriw ne specifications. 3. nhyɛso anwenne a ɛwɔ dimensional stability. 4. nsukorade a wɔde dade ayɛ a ɛwɔ su a ɛkorɔn a ɛma ɛyɛ den. 5. nhyɛso ntini a asiane wom sɛ adwennwen bɛpaapae. 6. nhyɛso ntini afoforo a ɛwɔ mmara titiriw, nsɛm a wɔde kyerɛw nsɛm ne mfonini ahorow. Wɔ steel welded pressure vessels mu no, residual stress a ɛdu aba no ho no ba wɔ beae a ɛbɛn weld no. Awo ntoatoaso a ɛwɔ saa adwennwen yi mu no fa nsakrae a ɛba wɔ nhyehyɛe a wɔde austenite afra mu no ho. Nhwehwɛmufo pii akyerɛ sɛ sɛnea ɛbɛyɛ a wobeyi adwennwen a aka no afi hɔ bere a wɔayɛ welding awie no, sɛ ɛyɛ hyew wɔ digrii 650 mu a, ebetumi anya nkɛntɛnso pa wɔ dade a wɔde hyɛ nsu mu a wɔde hyɛ nsu mu no so. Bere koro no ara mu no, wogye di sɛ sɛ wɔanyɛ ɔhyew ayaresa a ɛfata wɔ welding akyi a, wɔrentumi nnya corrosion-a ɛko tia welded nkwaa no da. Wɔgye di mpɛn pii sɛ adwennwene ano aduru ɔhyew ayaresa yɛ adeyɛ a ɛma welded adwuma no yɛ hyew kodu 500-650 digrii na afei ɛma ɛyɛ nwini nkakrankakra. Adwennwen a ɛso tew no fi creep a ɛwɔ ɔhyew a ɛkɔ soro mu, a efi ase fi digrii 450 wɔ carbon dade mu ne digrii 550 wɔ molybdenum-a dade wom mu. Dodow a ɔhyew no kɔ soro no, dodow no ara na ɛyɛ mmerɛw sɛ wobeyi adwennwen afi hɔ. Nanso, sɛ wɔboro dade no mu ɔhyew a ɛyɛ hyew no so pɛ a, dade no ahoɔden so bɛtew. Enti, ɛsɛ sɛ ɔhyew a wɔde sa adwennwen so tew no tumi yɛ ɔhyew ne bere mu nneɛma abien no yiye, na emu biara nyɛ nea ɛho hia. Nanso, wɔ adwennwen a ɛwɔ weldment no mu no, adwennwen a ɛtwetwe ade ne nhyɛso a ɛma nhyɛso ba no ka ho bere nyinaa, na adwennwen ne elastic deformation wɔ hɔ bere koro mu. Sɛ dade no hyew kɔ soro a, ahoɔden a ɛma aba no so tew, na mfitiase elastic deformation no bɛyɛ plastic deformation, na ɛnam so ama adwennwen no ayɛ mmerɛw. Dodow a ɔhyew no kɔ soro no, dodow no ara na woyi nhyɛso a ɛwɔ mu no fi hɔ koraa. Nanso, sɛ ɔhyew no yɛ kɛse dodo a, dade no ani bɛyɛ oxidized kɛse. Bio nso, wɔ PWHT ɔhyew a ɛwɔ dade a wɔadum ne nea wɔahyɛ no hyew mu no, ɛnsɛ sɛ nnyinasosɛm no boro dade no mfiase ɔhyew a ɛyɛ hyew no so, a mpɛn pii no ɛba fam bɛyɛ digrii 30 sen dade no ɔhyew a ɛyɛ hyew mfiase no, anyɛ saa a, nneɛma no bɛhwere nea ɛma wodum ne nea ɛyɛ hyew no, na ahoɔden ne abubuw a ɛyɛ den no so bɛtew. Ɛsɛ sɛ wɔde adwene si saa asɛm yi so titiriw wɔ adwumayɛfo a wɔyɛ ɔhyew ho adwuma no so. Dodow a ɔhyew a wɔde sa ɔhyew a ɛwɔ WELD akyi no kɔ soro ma ɛma nhyɛso fi mu ba no, dodow no ara na dade no yɛ mmerɛw kɛse. Mpɛn pii no, wobetumi ayi nhyɛso a ɛwɔ mu no afi hɔ denam ɔhyew a wɔde bɛma dade no ayɛ hyew a ɛma ɛyɛ hyew no so. Recrystallization temperature no ne melting temperature no wɔ abusuabɔ kɛse. Mpɛn pii no, recrystallization ɔhyew K=0.4X melting temperature (K). Dodow a ɔhyew a wɔde yɛ adwuma no ho hyew no bɛn recrystallization ɔhyew no, dodow no ara na ɛyɛ adwuma yiye wɔ residual stress a woyi fi hɔ no mu.
4. Nkɛntɛnso a ɛkɔ akyiri a PWHT post-WELD ɔhyew ayaresa no nya no so mfaso nni so koraa. Mpɛn pii no, post-WELD ɔhyew ayaresa no boa ma residual stress no fi hɔ na ɛyɛ bere a ahwehwɛde ahorow a emu yɛ den wɔ hɔ ma adwennwen a ɛyɛ mmerɛw nkutoo. Nanso, nkɛntɛnsoɔ a ɛyɛ den sɔhwɛ a ɛwɔ nhwɛsoɔ no mu no kyerɛ sɛ post-WELD ɔhyew ayaresa no nyɛ papa sɛ ɛbɛma denden a ɛwɔ dadeɛ a wɔde ahyɛ mu no ne weld ɔhyew a ɛka no no ayɛ yie, na ɛtɔ da bi a intergranular cracking betumi aba wɔ grain coarsening range of the weld heat acted zone. Nea ɛka ho no, PWHT de ne ho to nneɛma ahoɔden a ɛso tew so wɔ ɔhyew a ɛkɔ soro mu na ama adwennwen so atew. Enti, wɔ PWHT mu no, nhyehyɛe no betumi ahwere kateeyɛ. Wɔ nhyehyɛe a ɛfa PWHT nyinaa anaa ne fã bi ho no, ɛsɛ sɛ wosusuw tumi a weldment no wɔ wɔ ɔhyew a ɛkɔ soro mu no ho ansa na wɔayɛ ɔhyew ho adwuma. Enti, sɛ woresusuw ho sɛ ebia wobɛyɛ post-WELD ɔhyew ayaresa a, ɛsɛ sɛ wɔde mfaso ne ɔhaw ahorow a ɛwɔ ɔhyew ayaresa mu no toto ho koraa. Sɛ yɛhwɛ nhyehyɛe no mu adwumayɛ a, ɔfã bi wɔ hɔ a ɛma adwumayɛ tu mpɔn ne ɔfã bi a ɛtew adwumayɛ so. Ɛsɛ sɛ wobu atɛn a ntease wom a egyina adwuma titiriw a ɛne sɛ wobesusuw afã abien no nyinaa ho koraa so.
