art4 fazele imbinarilor sudate

8/6/2019 Art4 Fazele Imbinarilor Sudate

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FAZELE CONTROLULUI MBINARILOR SUDATE

PHASES CONTROL OF WELDED JOINTS

Ploscaru Ctlin, Popescu Rodica Mariana,

Marmandiu Alexandra, Moneag Mihaela

UNIVERSITATEA TRANSILVANIA DIN BRAOV

TRANSILVANIA UNIVERSITY OF BRASOV

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Rezumat: Controlul calitii este o operaieindependent de operaia de execuie, prin care,pe de o parte, se veric dac baza tehnico-material (materie prim, utilajele i mainile,standurile de prob etc.) au caracteristicile

calitative i precizia prevzute n documentatie,iar pe de alta parte, veric ncadrareacaracteristicilor de calitate ale reperelor,subansamblelor i produselor nite n limiteleprevzute de documentaie.

Cuvinte cheie: Controlul calitii, mbinrisudate

1. Stadiul actual al cercetrilor n

domeniu

n functie de metoda aplicat, controlul poate : activ sau pasiv; dinamic sau static; preventiv, economic.

A. Inspecia

Inspecia este tot o operaie de control ns cu o sfer de aciune mai larg. Eaurmrete dac metoda de control aleas

este corect, dac operatia de control a fostefectuat n mod corespunztor, dac deciziacontrolorului a fost respectat, dac maina,utilajul sau procesul de fabricaie au fost oprite ncazul instabilitii acestora etc. n plus inspeciase extinde i asupra documentaiei, vericnddac materiile prime i materialele au fost binealese, daca toleranele au fost corect stabilite,dac pregatirea fabricaiei asigur realizareaproduselor la nivelul prototipului omologat,dac au fost aduse modicrile constructiv-

tehnologice necesare, ca urmare a decienelordepistate n procesul de fabricaie, la probelenale sau n exploatare etc.

n concepia modern, rolul controluluicalitii este de a aciona i interveni operativ

Abstract: Quality control is an independentexecution operation through on one handtechnical and material base is checked (rawmaterials, equipment and machines, test standsetc.) accordingly to the quality features and

accuracy from specication les and on the otherhand is checking the link between parts qualityfeatures, subassemblies and nal productswithin limits from specication les.

Key words: Quality control, welding joints

1. The present state of research

in domain

Accordingly to the method the control can be: active or passive; dynamic or static; preventive, economical.

A. Inspection

inspection is also a control operation butwith a larger covering area. it follows whetherthe chosen control method is correct, is controloperation has been conducted in a propermanner, if the inspector decision was followed, ifthe machine or equipment has been shut downdue to its instability. Moreover, the inspectioncan be extended on technical les as well,searching if raw materials have been correctlyselected, if the allowance rate is within limits,if fabrication preparation process will enforcethe achievement of homologated prototypeas prescribed, if necessary modication hasbeen done as a result of spotted deciencies

during fabrication process, nal tests or duringoperation etc.As a modern conception, quality control part

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oriunde i de ori cte ori este nevoie pentru caprodusul nal s corespund condiiilor cerutei astfel s se obin o continu reducere arebuturilor i eliminarea acestora. Cu altecuvinte, n conceptia modern, controlul calitiiise atribuie un rol activ i creator i nu numai dedepistare i sortare a rebuturilor.

Aciunea controlului calitii ncepe dinmomentul alegerii procesului de productie,continu cu instalarea echipamentului deproducie sau cu pregatirea acestuia pentrurealizarea optim a uxului de fabricaie,cu calicarea forei de munc folosit i cuachiziionarea de materii prime i materialecorespunztoare. Acest control se desfoarpe tot parcursul fabricaiei i al expedieriiproduselor i se ncheie cu asistena tehnic(service) acordat de ntreprinderea respectiv

n perioada de garanie. Datorita progresuluitehnic ca i exigenei sporite exist tendina caperioada de garanie a produselor s creasc.

Concepia care st la baza acestuiprincipiu const n analizarea cheltuielilor totalenecesare pentru utilizarea produselor cu odurata de exploatare mai lung.

n concluzie, controlul calitii trebuies e prezent n toate etapele premergtoaredesfurrii de fabricaie, n timpul acestuia,pentru controlul produsului nit i livrarea lui.Ulterior prin asistena tehnic (service-ul asigurat)

se acord beneciarilor iar n cazul instalaiilorcomplexe continund n timpul montajului i nperioada efecturii probelor tehnologice.

Acest control poart denumirea decontrol total al calitii. [1]

B. Controlul total al calitii

Controlul total al calitii are la bazurmtoarele principii:

Calitatea trebuie condus i coordonat

de ctre un organ specializat, ncepnd de laproiectare i pn la service; Activitate de control s se desfoare

concomitent pe trei planuri: Participarea activ la fazele de

pregtire a fabricaiei, alegerea i promovareamainilor i instalaiilor tehnologice, dotarea cuscule, dispozitive i vericatoare, aparate demsura i control, instruirea personalului asupracerinelor calitative;

Vericarea realizrii calitii produselor ncepnd de la recepia materiilor prime i a

materialelor aprovizionate, n timpul uxuluide fabricaie pn la produsul nit i controlulambalrii i expedierii;

is to act and intervene decisively any timeas long as required in order to have a nalproduct in compliance with technical les andto eliminate, if possible any waste. With otherwords, in a modern conception, quality controlhas an active and creative part and not only tond and sort scrap.

Quality control action begins withthe production process selection, and thenfollows with production equipment installationor preparation in order to realize fabricationprogram, labor qualication, purchasing rawmaterials and appropiate. Quality control ispresent on the entire fabrication program, duringshipping and it ends with technical assistance(service) provided by the manufacturer duringwarranty period. Due to the technologicalprocess and increased demanding from the

customers the trend is to extend warranty period.Basic idea of this concept consists inanalyzing overall expenses in order to use theproducts a longer period of time.

As a conclusion, quality control has tobe present during all stages of pre-fabrication,during fabrication, nal check and delivering.Next, through technical assistance department(service) nal user (the customer) has apermanent support and even more for complexinstallation is provided during assembly as wellduring nal technological tests.

This type of control is named total qualitycontrol. [1]

B. Total quality control

Total quality control is based on nextprinciples:

Quality has to be managed andcoordinated by a specialized unit starting fromdesign until service;

Control activity has to be focused onthree directions: Active participation during fabrication

preparing process, machines and technologicalinstallations selection, tools, devices and testers,instrumentation, training the personnel;

Quality checks starting from rawmaterial reception and supplied inventory, duringfabrication process until nal product packagingand shipping;

Following product operation behavior,reliability and maintenance.

Based on the phase, the control can be:

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Urmrirea comportrii n exploatare aprodusului, probe de abilitate i mentenan.

n funcie de faza la care se efectueaz, controlulpoate :

Control de recepie: la faza derecepionare a materialelor i materiei prime;

Control de fabricaie: la faza defabricaie propriu-zis;

Control nal: pentru produsul nit.n functie de locul de execuie, controlul

de calitate este: Centralizat (n puncte xe); n ux, adica n diferite puncte ale

procesului de fabricaie; Volant, la diferite locuri de munc, dup

necesiti.[2]

Fazele controlului mbinrilorsudate

Procesul de execuie al mbinrilorsudate este superior fa de cel al altor tipuride mbinri deoarece se elimin toate celelalteoperatii tehnologice pregtitoare necesare altortipuri de imbinri. [3]

Imbinrile prin sudura ocupa un loc totmai mare n diferite domenii tehnice cum ar :

La utilajele chimice -imbinri de

etaneitate pentru cazane de presiune,recipiente, gazometre; La construciile de rezisten -poduri,

schelete metalice, schelete pentru cldiri; La construciile de maini -automobile,

maini-unelte, nave, avioane etc.n multe domenii, mbinarea prin sudare

este soluia cea mai potrivit, ajungnd chiaro soluie de nenlocuit, dar, pentru a-i atingescopul funcional, trebuie s e realizat corecti de o calitate corespunztoare.

De aceea, apare necesitatea organizrii

unui control corespunztor pentru evitarea idepistarea defectelor de sudare. Toate sudurilenecorespunztoare ce prezint defecte potprovoca pagube, accidente ireparabile i ofuncionare defectuoas a instalaiilor.

A. Controlul pieselor supuse sudrii

Se veric dac marginile pieselor ceurmeaz a se suda sunt curate de impuriti(zgur, vopsea, ulei, umezeal, etc);

Se veric dac marginile de mbinare au fost prelucrate la cotele indicate n documentaia tehnic. Distanele dintreelementele ce se vor mbina (rostul de sudura)se iau din ele tehnologice sau din desenul deexecuie al ansamblului sudat.

Acceptance control at raw materialsreceiving;

Fabrication control: during fabricationtime;

Final control: for nal product.

Based on the execution place qualitycontrol can be:

Centralized (xed points); During fabrication process in different

stages; Random control at different working

places.[2]

Phases control of welded joints

Welded joints execution process is farmore superior to other joining types because alltechnological operations are no longer required.[3]

Welding joints are expanding their areaof utilization such as: Chemical installations: seal joints for

pressurized tanks, containers, and gas meters. Resistance construction: bridges,metallic structures as well construction frames; Machine construction: cars, tools andequipments, ships, aircrafts etc.In a lot of domains welded joint is the onlysolution but in order to be functional it has to becorrectly executed with an appropriate quality.

Therefore an appropriate control inorder to detect and avoid welding aws is anecessity. All welding joints with defects can

cause damages, accidents and faulty installationoperating.

A. Control of the parts to be welded

To be checked if edges to be welded areclean free of slag, paint, oil, moist etc. To be checked if welding edges have

been machined to the dimensions from technicalles. The distances between elements are takenfrom technological specications or from theblue print.

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B. Controlul calitii materialelor

folosite

Se veric dac sunt respectateindicaiile date n desenul de execuie (asuprafolosirilor electrozilor, procedeul de sudareutilizat etc.).

C. Controlul efectuat n timpul executrii

sudrii

Se veric dac este respectat regimulde sudare (tensiunea, viteza de naintare,calitatea compoziiei elementelor utilizate);

Se controleaz dac zgura estenlturat pentru a se putea efectua un controlvizual, lundu-se msuri necesare dac seconstat apariia unui defect exterior.

D. Controlul mbinrilor sudate

Dup terminarea operaiei de sudarese efectueaz controlul propriu-zis al mbinriisudate care poate : control exterior prinobservare sau prin ncercri distructive saunedistructive, cu raze X sau .

E. Calitatea custurii

Este determinat de:-compoziia chimic a metalului depus;-structura, procentul de incluziuni

nemetalice;-defecte macrostructurale;-defecte datorate crpturilor.

F. Compoziia chimic

Compoziia chimic a custurii depindede:

- raportul dintre cantitile din metalul debaz i cel de adaos din custur;

- arderea elementelor aate n metalulde baz i n cel de adaos;- capacitatea de nglobare (absorbie) a

oxigenului i azotului din aer, din ux. Elementele componente ale custurii

se determin prin analiza chimic a probelor cevor luate din aschii metalice extrase special nacest scop.

Prin controlul nedistructiv pot depistatedefecte macrostucturale ale materialului depus,ca: incluziuni de zgur i oxizi, pori, crpturi.

Defectele macrostructurale inueneaz

direct rezistena custurii i celelalte condiiiimpuse ei.

Defectele interne: porii gazoi, incluziuni

B. Quality control of utilized materials

To be checked if indications fromblue print are followed (electrodes, weldingprocedure).

C. Quality control during welding

procedure

To be checked if edges welding regimeis accordingly to the specications (voltage,advance speed, elements quality composition).

Slag has to be removed in order toperform a visual check for external defects.

D. Welded joints quality control

After welding procedure a propercontrol is conducted such as an externalobservation one or using destructive or nondestructive procedures with X rays or rays.

E. Welded seam quality

Is determined by:-Chemical structure of deposited

material;

-Structure and percentage of metallicinclusions;

-Macro structural defects;-Crack defects.

F. Chemical composition

Chemical composition depends on:-Ratio between base metal and ller

metal within the seam;-Burned elements from base metal and

ller metal;-Absorption capacity of O2 and N fromthe air and from ux;

Welded seam components aredetermined by using chemical analysis of testsamples from metal chips collected for thisreason;

By using non destructive procedurecan be revealed macro structural defects suchas: slag and oxides inclusions, pores, cracks.

Macro structural defects are directlyresponsible for seam resistance and otherrelated aspects.

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de zgur, crpturi, lips de penetraie, sedetermin fr distrugerea custurii, folosindmetode radioscopice cu raze X si sau metodamagnetic i ultrasonic.

Ali factori care inueneaz calitateambinrilor sudate sunt:

- mrimea;- caracterul i repartiia tensiunilor

interne n custur.

Concluzii

Controlul total al calitii are ocaracteristic modern prin faptul c folosind unnumar mic de personal ct mai mic posibil sse obin o conducere a procesului de produciecare s garanteze o calitate superioar a

produselor. n concluzie, controlul de calitateeste un control de conformitate.

Bibliograe

[1] xxx SR ISO 9002 Sistemele calitii-modelpentru asigurarea caliii n productie, instalarei servicii asociate[2] xxx SR ISO 9003 Sistemele calitii-modelpentru asigurarea calitii n inspecie i cercetri

nale[3] xxx Construcii sudate n aeronautic, EdituraTehnic, 1986

Internal defects such as: gaseouspores, slag inclusions are determined withoutdamaging the seam by using X rays, rays ormagnetic and ultrasonic methods.

Other inuencing factors are:- Size;- Type of internal tensions within welded

seam.

Conclusions

Total quality control has a modern characteristicby using a limited number of personnel in orderto manage the production process which isthe guarantee of a high quality product. As anal conclusion, quality control is a conformitycontrol.

References

[1] xxx SR ISO 9002 Sistemele calitatii-modelpentru asigurarea calitatii in productie, instalaresi servicii asociate[2] xxx SR ISO 9003 Sistemele calitatii-modelpentru asigurarea calitatii in inspectie si cercetari

nale[3] xxx Constructii sudate in aeronautica, EdituraTehnica, 1986

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