t1gLLrrt-D

LLrtl:|4

LErLrrrLLrrrrrrrgl-t-

l*rr14

l-rJl-rTLl-

l:14

nV4,,,-

GIIPFACenter for Material Processing and Failure Analysis

Universitas Indonesia

Technical Report

Document No : L-0 1 6 1 /SNCMPF AnU 5

Crack ldentification of ERW Steel Tube

Prepared for: PT. lndonesia Steel Tube Wotus (lSfW

Office addre€a:

Lab Uji Metalurgi (LUM)Departemen Teknik Metalurgi dan lvlaterialFakultas Teknik Universitas lndonesiaK?mpus Baru Ul DeDok 16424Telp: 021-786351 0, 78849045 Fax: 02'1 -78888'1 1 1e.mail: lum@metal.ui.ac.id

Center fol Materials ProcessinE and Failure Aralysi$Univ€rsilas lndone.sia

Technical Rcfort No. : L-016l /SA/CMPFA/2015 GITIPFA

L__rrrrrrt t )

L,-:

=rrFFPrrHb

FrrrrrrrrIJ

1-r14

R-gport Documenl ldeEtiligs

Document No"No. Dokumen

L-01 6'1 /SfuCMP FAJ2O,1 5

Report TitleJudulLaporan

Crack ldentification of ERW Steel Tube

Date of lssueTanggal Selesai

Apr i l21" r ,2015

Service UserPemakai Jasa

PT. Indonesia SteelTube Works (ISTW;

User AddressAlamat Pemakai Jasa

Pulo Gadung

MaterialBahan

Fe-Based

Material ldentitiesldentitas Bahan

Steel Tube

Testinq TvpesJenis Pengujian

MetallographicEnergy Dispersive X-Ray Spectroscopy (EDS)

Testinq ApparatusAlat Uji

sEtvlEDS EDAX Appollo X

Testinq StandardsStandard Uji

ASTM E3ASTM E4O7

Repod lssuance

Bintang Suryo Heidiansyah, S.T

Meta urgy and Mateial Depaftment nakes no representations or waffanties, either exprcssed or implied,and specificatly ptovicles the rcsults of this repoft "as is' based on the infoffiation provjded by client.

Phone: 021-7863510,78849045 Fax 021-76EE8'111 E-mail: lul(iloClaluilg jd PaEe2otT

Ccnter for Materials Pruc€ssinll and Failure AnalysisUnivensitas hdonesia n

\,/"_

FF7

Fr?rrrrEEFPELrr?rrrrrfrFr

Technical Report No. : L-0 1 6 I /SA,/CWFA,/201 5 SIP-EA

l. Background

PT. ISTW requested lab analysis for their product seen in figure '1. The client informedthat the crack is found on the surface of the product. The analysis is performed to identifythe possible cause of crack which occurred in the weld seam after the exoansion Drocess.

Figure l. As Received Sample

ll. Scope of Testing

The analysis is canied out at CMPFA lab, Universitas Indonesia. The scope of testing is as

follows:

. Microstructure Observation by Light Microscope

. Chemical composition by EDS

lll. Testing Result and Discussion

lll.l Microstructure Test by SEM

Microstructure testing is performed to observe the microstructure of the tube using SEM.Observation is done to the thlee samDles as illustrated in Table L SamDle 1 is taken atthe cross section of the crack, sample 2 is taken at the surface of the crack and sample 3is taken at the undeformed lield area. The microstructure of the test results by using SEMare as follows (see Table l).

Phone:021-7863510,78849045 Fa* 021-7888811'l E-mail: lum@metal.ui.ac. jd Page3ofT

Center for ilaterials Prucesdng and Failurc /lnalyslsUrdve|.sihs lndonosia

Teohnioal Report No. : L0 1 6 1 /S-4/CW FA./20 1 5

Table l. Microstructure Test Result by using SEMAs received Sample Tested Sample Microstructure Observation

Microstruc{ure of SamDle I

Microstruc{uF oi SamDle 2

M icrostructure of SamDle 3t

Phone: 021-7863510, 78849M5 Fax 02'1-78888'111 E-mail: lll!]@EqblUEqu Page4ofT

Center for Matsrials Pruc€ssing ard F&ilure AnalysisUnivorsitas hdolesia

Technical Rcport No. : L-016lEACWFU29I5

FEEFEEEFPFrrrIJ

Lt t

t-r-t_L-

L-Lrl:t-

l-t--

lll.2 Chemical Composition by EDS

Energy Dispersive Spectroscopy (EDS) isfound nearby the crack. The location testtable 2.

performed on the suspicious phase (inclusions)area and test results for EDS are presented in

Table 2. Elements found in the inclusions after EDS test.

Phone:021-7863510,78849045 Fax 021-78888111 E-mait: IUI@EetaLqEe.ilL Page5ofT

C€nter for Materials Processing and Faihre AnalysisUniv€rsitas Indonesia

t - .l-D)

L|-'Jt-" t 't:-rltl

L7l-D)

LLl-D.

LLl-D)

LLJJ

LL_t)

Ll-t)

LL7

FI

PB)Ib

LrL

LLLLLF'

Technical Report No. : L-01 61/SA./CWFA/2015

lV. Discussion

In the ERW process, strip is fed into a forming mill, shaped into a cylinder and passedthrough an induction coil or under contacts (figure '1a). The magnetic field aroundinduction coil causes current to flow on the edges of the strip. The edges, in turn, heat updue to resistance to the flow of current. The hot edges are forged together in the weld rollsand a weld is achieved. The weld is a true forge weld in that no filler metal is added and, ifdone properly, no molten or oxidized metal is left on the bond plane. Figur€ 1b shows thatall of the liquidus and metal oxides are squeezed out of the weld as the edges passbetvveen the weld rolls.

It is found that the possible occurrence of certain kinds of weld defects is determined bythe types of phenomena encountered during welding: A possible weld defect is a cold weldand a penetrator. The cold weld is composed of a colony of oxides which are formed onthe edge surfaces and remain because they are not squeezed out from between them.The penetrator by nature is a slag inclusion produced when molten slag is drawn into agapped zone by the action of surface tension and capillary effects in a returning process ofthe molten bead.

A cold weld occurs uniformly over a wide range along the weld line, and any accidentalohenomena are not considered to account for the cold weld. A number of extrusions areobserved to be formed on both the edge surfaces approaching to the V-convergency point.These extrusions were sandwiched between the edges when they were welded. lt isconsidered that the extrusions consist mostly of oxides. The reason for this is that it shouldnot be possible to form such extrusions against strong electromagnetic pressure if theextrusions consist of metal. Thus, the cold weld is a colony of oxides formed on the edgesurfaces that remain because they were not squeezed out from between them; this hasbeen conceived to be a mechanism of producing all weld defects in ERW.

SEM observation resull at the sample 1 and sample 2 shows that inclusions were foundnearby the crack (table 1). The inclusion was then checked using EDS, the test result

Phone:021-7863510,78849045 Fax: 021-78888111 E-mail: um@meta ul.acid Page6ofT

Center for aterials ProcessinE and Failuro AnalysisUnivensitas lndonesiaF

FBLrH

H*

BH*

HBBF

Teohnical Report No. : L-01 6l /SACMPFA/2o I 5

shows dominant element of Carbon, Oxygen, Manganese and lron. Carbon may comefrom dirt or organic matter. lron and Manganese together with Oxygen may form Oxides.The metal oxide may have been trapped on the bond plane instead of being squeezed outwith the molten metal. These oxides are formed on the surface of lhe molten metal edgesin the vee. In the vee, if the approach velocity of the strip edges is less that the melt rate,i.e., the edges are melting faster than they are being squeezed, a pocket forms (figure 3a)behind the vee apex will contain both molten metal and metal oxides. The normal squeezeout does not completely remove the larger than normal liquid volume and an entrapmentresults (figure 3b).

V. Conclusion

Visually, crack is found at one area of the expanded tube. No crack is found on other area.After cutting, the crack is analysed with SEM and inclusions are found around the crack.These inclusions are not found at the good weld line on other area. The inclusion iscomposed of manganese and oxygen in dominant quantity, lt ls confimed that the crackwas found after expansion and was caused by lhe presence of manganese oxidesinclusion in the weld line.

CIUPFA

Pockel behind apex

Oxides andL'quid

Centerline ofweld rolls. Entrapments (Penetrators)Figure 3, Schemaljc Oxjdes

Phone: 021-7863510,7A8/9045 Fax 021-7888811 1 E-mail: lurn@meta.! aci.l paeeT otj