a. Pengujian Kekerasan

• Alat uji yang digunakan adalah Hardness Tester Merk AFFRI buatan Italy dengan status terkalibrasi, dengan metode uji SNI 19-0407-1998 : Cara Uji Keras Rockwell (Skala A-B-C-D-E-F-G-H-K)

• Persyaratan sampel uji untuk pengujian perlu dipersiapkan :

- Sampel uji harus rata untuk menjaga akurasi hasil yang didapat

- Pengujian dilakukan minimal pada 5 titik uji

b. Pengujian Komposisi Kimia

Alat uji yang digunakan adalah :

1. Spektrometer Merk Hilger,

2. Spektrometer Merk Metal Scan buatan Inggris

3. Spektrometer Merk Was dari Jerman

(semua status alat terkalibrasi)

• Untuk pengujian besi cor sampel di persiapkan dalam bentuk cill test.

• Untuk pengujin Baja , Alumunium, Kuningan, Tembaga baik dari casting ataupun profil bisa langsung dari bahan

c. Pengujian Struktur Mikro

• Untuk mengetahui struktur logam

• Alat uji yang digunakan adalah seperangkat alat uji metalografi (Miskroskop, kamera Nikon buatan Jepang dengan status kalibrasi

• Metode uji yang dipakai adalah I.K. 5.4.1.4 (Instruksi Kerja Metalografi dan SNI 07-3622-1994 tentang Evaluasi mikrostruktur grafit di dalam besi cor)

• Sampel uji diambil dari potongan bahan/produk yang diujikan atau sengaja dibuat tersendiri

d. Pengujian Kuat Tarik (Tensile Strength)

• Untuk mengetahui kekuatan tarik dari bahan logam

• Alat uji yang digunakan adalah Universal Tensile Strength kapasitas 30 ton buatan Jerman dengan status terkalibrasi

• Sampel uji dibentuk standart sesuai dengan jenis benda uji (ada panduannya)

Bentuk batang uji kuat tarik Sesuai SNI 07-0371-1989

(Batang Uji Tarik untuk Bahan logam)

1.Batang Uji No.4

· Untuk bahan dari : Baja Cor, Baja Tempa, Baja Canai, Besi Cor Meleabel dan Besi Cor Nodular (FCD), juga untuk Logam Bukan Besi dalam bentuk batangan serta paduannya.

· Bentuk benda uji :

Keterangan :

Panjang ukur ( L ) : 50 mm

Panjang bagian pararel ( P ) : Sekitar 60 mm

Diameter ( D ) : 14 mm

Jari-jari bahu ( R ) : 15 mm atau lebih

Panjang total sampel ( PT ) : Min 250 mm

D	Panjang Ukur (GL/L)	Panjang bagian parallel (P)	Radius (R)
14	50	Mendekati ( L + 2D )	15 in

2. Batang Uji No. 8

· Untuk uji bahan dari : Besi Cor

· Ukuran batang uji, diameter bagian pararel dibuat berdasarkan pada tabel

· Bentuk benda uji :

Satuan : mm

panjang total sampel minimal 250mm

Nomor Batang Uji	Diameter Ukuran Contoh Hasil Cor	Panjang Bagian Pararel (P)	Diameter Hasil Akhir (D)	Jari-jari Bahu (R)
8 A 8 B 8 C 8 D	Sekitar 13 Sekitar 20 Sekitar 30 Sekitar 45	Sekitar 8 Sekitar 12,5 Sekitar 20 Sekitar 35	8 12,5 20 32	Min 16 Min 25 Min 40 Min 64

3.Batang Uji No. 6

· Batang uji digunakan untuk uji tarik baja lembaran tipis dan baja profil dengan tebal tidak lebih dari 6 mm.

· Bentuk benda uji :

Panjang ukur L = 8 VA

(A adalah luas penampang bagian paralel)

Panjang bagian paralel P = L sekitar 10 mm

Lebar W = 15 mm

Jari-jari bahu R = 15 mm atau lebih

Tebal Sesuai dengan tebal asli

Panjang minimal sampel 250 mm

4.Batang Uji No. 1

· Batang uji digunakan untuk uji tarik Baja Plat, Baja lembaran (Plat) dan Baja Profil

· Bentuk benda uji :

Panjang ukur L = 200 mm

Panjang paralel P = 220 mm

Tebal Sesuai dengan tebal bahan

Lebar W Seperti Tabel

No. Batang Uji	Lebar W
1A 1B	40 (Atau38)mm 25mm

5.Batang Uji No. 13

· Batang uji digunakan untuk uji tarik Pelat

· Bentuk benda uji :

Nomor Batang Uji	Lebar (W)	Panjang Ukur	Panj Bag. Paralel (P)	Jari-jari Bahu (R)	Lebar Bagi
13 A 13 B	20 12.5	80 50	Sekitar 120 Sekitar 60	20-30 20-30	- 20 atau lebih

Satuan mm

Ukuran tebal sesuai benda

e. Pengujian CE Meter

• Untuk mengetahui suhu cairan logam dalam tungku

• Untuk mengetahui kandungan unsur C dan Si masih dalam kondisi cair

• Alat uji yang digunakan adalah CE Meter MULTI LAB buatan Inggris

• Metode pengujian langsung pada cairan logam saat proses peleburan

f. Pengujian Termokopel

• Untuk mengetahui suhu cairan logam dalam tungku atau ladle secara akurat

• Metode pengujian langsung pada cairan logam saat proses peleburan

g. Pengujian Pyrometer

• Untuk mengetahui suhu cairan logam dalam tungku pada jarak tertentu

• Metode pengujian langsung pada cairan logam saat proses peleburan

• Nilai uji dapat dikonversikan ke metode yang diingkinkan

Surface blow holes

Characteristic features Individual or groups of cavities. Mostly large with smooth walls.Incidence of the defect Gases entrapped by solidifying metal on the surface of the casting which result in a rounded or oval blow hole as a cavity. Frequently associated with slag or oxides. The defects are nearly always located in the cope part of the mould in poorly vented pockets and undercuts. The formation of blow holes is more intense with grey iron castings than with SG iron. Possible causes Resin-bonded sand  Core venting not good enough  Release of gas from core too great  Moisture absorption by the cores too great  Too low gas permeability of the core sand Clay-bonded sand  Moisture content of sand too high, or water released too quickly  Gas permeability of the sand too low  Sand temperature too high  Bentonite content too high  Too much gas released from lustrous carbon producer Moulding plant  Compaction of the mould too high Gating and pouring practice  Casting temperature too low  Metallostatic pressure too low when pouring Remedies Resin-bonded sand  Improve core venting, provide venting channels, ensure core prints are free of dressing  Reduce amounts of gas. Use slow reacting binder. Reduce quantity of binder. Use a coarser sand if necessary.  Apply dressing to cores, thus slowing down the rate of heating and reducing gas pressure.  Dry out cores and store dry, thus reducing absorption of water and reducing gas pressure. Clay-bonded sand  Reduce moisture content of sand. Improve conditioning of the sand. Reduce inert dust content.  Improve gas permeability. Endeavour to use coarser sand. Reduce bentonite and carbon carrier content.  Reduce sand temperature. Install a sand cooler if necessary. Increase sand quantity.  Reduce bentonite content. Use bentonite with a high montmorillonite content, high specific binding capacity and good thermal stability.  Use slow-reacting lustrous carbon producer or carbon carrier with higher capacity for producing  lustrous carbon. In the last instance, the content of carbon carriers in the moulding sand can be reduced. Moulding plant  Reduce compaction of the moulds. Ensure more uniform mould compaction through better sand   distribution. Gating and pouring practice  Increase pouring temperature, if necessary increase pouring speed.  Increase metallostatic pressure by changing the gating systems. If possible raise the cope flask. Background information The occurence of gas bubbles is dependent on the gas volumes present and their pressure. If it is not possible to discharge the gases from the mould cavity they can be trapped in the liquid metal. There is a great danger af surface pitting an cores because they are surrounded by liquid metal and the gaseous reaction products are primarily removed through core prints. Gas bubbles are more frequently observed with smaller cores. It is recommended to use coarser sands and a corresponding application of mould dresssings [1]. Cores with an unfavourable shape should contain waste gas channels. The necessary cross-sections of gas discharges from cores in relationship to core binders and geometry are thoroughly investigated in [2]. Obstruction of gas discharge results in bubbles being trapped in the metal. This fault also accurs with large gas discharge cross-sections when using phenolic resins. Hygroscopic binders like waterglass require large cross-sectians for gas discharge. Contrary to this, the occurrence of gas bubbles can assist drying af the cores. Use of cold cores in hot moulds can lead ta water adsorp­tian with hygroscopic binders. These can explosively vapo­rize during pouring and lead to defects. With bentonite sands, gas bubbles also primarily occur through the formation of water vapour [3]. This can be countered by reduction of the pouring rate and avoidance of impingement of the metal flow an the mould wall. When this defect occurs tbe gas permeobility of the sands should be high but the water content as bw as possible. All water absorbing materials like inert dust, bentonite and carbon carriers should be as bw as possible. Under certain circumstances this necessitates the use of clays containing large percentages of montmorillonite as well highly active carbon carriers. lt is also recommended ta develop the moulding sand as weil as possible. Well developed  sands require less water and release this slower during heating up. The occurrence of condensed water should be avoided. There should be no temperature differences between cores and moulds. Water can also precipitate on chaplets or chills and lead to gas defects on account of the absence of gas permeability. Frequently used chills can exhibit hairline cracks, in which capilbary condensation of water vapour  can occur and lead ta gas defects during pouring. It is important to avoid too high compaction in the moulding plant. With high compactian it should be checked whether the compacting pressure has to be reduced. References [1] Walter, Ch.; Gärtner, W.; Siefer, W. Analyse der Putzkosten bei Stahlguß Gießerei 73, 1986, S. 612-620 [2] Schlesiger, W.; Winterhalter, J.; Siefer, W. Zur Gasabführung aus Kernen Gießerei 74, 1987, S. 76-84 [3] Levelink, H. G.; van den Berg, H. Gußfehler aufgrund zu harter Formen Disamatic Tagung 1973, Vortrag 4, Kopenhagen Further references [4] Levelink, H. G.; Julien, T. P. M. A.; De Man, H. C. J. Gasentwicklung in Form und Kernen als Ursache von Gußfehlern Gießerei 67, 1980, S. 109-115 [5] Bauer, W. Einfluß der chemischen Zusammensetzung und des Formstoffes auf Gasblasenfehler im Gußeisen Gießerei-Rundschau 31, 1984, S. 7-13 Giess.-Prax. 1984, S. 198-205 [6] Kulkarni, A. R. Einfluß von Hinterfüllsand auf die Gußstückqualität Indian Foundry J. 26, 1980, S. 36-38 (engl.) [7] Hofmann, F. Einflüsse der Zusammensetzung und des Aufbereitungsgrades von Form- und Kernsanden auf Eisen-Formstoff-Reaktionen und andere Fehler bei Gußeisen mit Kugelgraphit 4. Int. Tagung der Lizenznehmer für das GF-Konverterverfahren, Schaffhausen 1981 Vortrag Nr. 8, 19 S. [8] von Nesselrode, J. B. Gußfehler in Gußeisen mit Vermiculargraphit, die beim Furanharzformen mit Phosphorsäure entstehen können Giess.-Prax. 1984, S. 37-39 [9] Tot, L.; Nandori, G. Verringerung gasbedingter Fehler in Gußstücken Sov. Cast Technol. 1988, S. 4-7 (engl.) Litejnoe proizvodstvo 1988, S. 6-7 (russ.) [10] Nikitin, V. G. Gasporenbildung in Gußstücken unter Einwirkung des hydraulischen Schlages in der Gießform Litejnoe proizvodstvo 1976, S. 28-29 (russ.) [11] Ramachandra, S.; Datta, G. L. Gasentwicklung aus Form- und Kernsanden Indian Foundry J. 21, 1975, S. 17-21 (engl.) [12] Orths, K.; Weis, W.; Lampic, M. Einflüsse von Formstoff und Form, Schmelzführung und Desoxidation auf die Entstehung verdeckter Fehler bei Gußeisen II Giess. Forschung 27, 1975, S. 113-128 [13] Kolotilo, D. M. Gasbildungsfähigkeit und Bildung verkokten Rückstandes der organischen Formkoponenten beim Gießen Litejnoe proizvodstvo 1976, S. 27-29 (russ.) [14] Probst, H.; Wernekinck, J. Zur Gasabgabe und Blasenbildung beim Erstarren gashaltiger Metallschmelzen Giess.-Forsch. 29, 1977, S. 73-81 [16] Perevyazko, A. T.; Nikitin, B. M.; Lozutov, V. N.; Yamshchik, I. I. Untersuchung der Ursachen für Gasblasen in Gußstücken Litejnoe proizvodstvo 1986, S. 6-7 (russ.) [17] Pant, E.; El Gammal, T.; Neumann, F. Einfluß der Schmelzweise und des Formstoffes auf die Gasblasenbildung bei Stahlgußstücken Gießerei 75, 1988, S. 238-245 Fig.24 Formation of a large gas bubble in the top of a grey cast iron radiator. Fig.25 Low alloyed grey iron casting. Formation of surface bubbles in the top part. Abb.26 Grey iron casting. Section through a surface bubble. The cut out segment is on top of the rest of the casting. Hardly any bubbles on the surface.