Analisis Kegagalan Pembentukan Ellipsoidal Head Pressure Vessel dari Dua Pelat Dilas ASME SA516 Grade 70N dengan menggunakan Metode Fabrikasi Cold Forming

Khairmen Suardi, Faris Fadli

Sari

Abstrak

Head pada pressure vessel yang berbentuk melengkung, seperti: hemispherical, torispherical, dan ellipsoidal dapat dibuat dari pelat dengan lebar 2.5 m yang mengalami proses metal forming. Namun, pelat yang tersedia di pasaran pada umumnya memiliki lebar 1,6 m. Kondisi ini menjadi batasan apabila ingin menggunakan satu material pelat secara integral sehingga dibutuhkan pelat untuk membuat head dengan lebar yang lebih besar. Oleh karena itu, untuk membuat head dengan lebar 2,5 m dilakukan proses cold forming pada dua pelat yang dilas. Namun setelah proses dilakukan, terjadi kegagalan berupa timbulnya retakan di sekitar area las. Pada paper ini akan dibahas analisis kegagalan proses cold forming yang terjadi pada dua pelat ASME SA516 grade 70N yang digunakan sebagai base metal. Untuk menganalisis penyebab kegagalan, maka dilakukan pengujian kekerasan, tarik, metalografi, dan komposisi kimia. Selain itu juga dilakukan perhitungan untuk mengetahui nilai crack consists of hot (UCS), cold cracking (Pcm), dan carbon equivalent (CE). Hasil perhitungan menunjukkan bahwa material tersebut memiliki nilai UCS di bawah 30, nilai Pcm berada di antara 0,23-0,35%, serta berada di zona II pada diagram Graville dimana nilai tersebut menunjukkan bahwa material memiliki kemampulasan  yang baik. Sementara dari hasil pengujian mekanis didapatkan nilai kekerasan dan kekuatan tarik yang lebih besar dari standar, yaitu masing-masing sebesar 300 HBW dan 621 Mpa dengan nilai elongasi yang masih tinggi, yaitu  sebesar 21,8%. Hasil pengamatan metalografi menunjukkan terbentuk fase martensit namun dalam jumlah yang sedikit pada area heat affected zone (HAZ) dengan bentuk butir seperti jarum. Fase martensit ini berperan sebagai stress concentration yang menjadi titik awal retak ketika proses cold forming dilakukan. Terbentuknya fasa martensit ini disebabkan oleh proses preheat yang tidak sesuai serta heat input yang terlalu besar.

 

Abstract

             The head on a pressure vessel with curved shapes such as hemispherical, torispherical, and ellipsoidal is derived from the formed plate. Generally the plates available in the market have a width of 1.6 m, this condition becomes a limitation if you want to use one plate material integrally so that a plate is needed to make a head with a larger width. Therefore, to make a head with a width of 2.5 m, a cold forming process is carried out on two welded plates. However, after the process is carried out, failure occurs in the form of cracks around the weld area. In this paper, we will discuss the failure analysis of the cold forming process that occurred on two ASME SA516 grade 70N plates used as base metal. In order to analyze the causes of failure, hardness, tensile, metallographic, and chemical composition tests were carried out. In addition, calculations were also carried out to determine the value of crack consists of hot (UCS), cold cracking (Pcm), and carbon equivalent (CE). From the calculation results it is evident that the material has a UCS value below 30, the PCm value is between 0.23-0.35%, and is in zone II on the Graville diagram where this value indicates that the material has good weldability. Meanwhile, from the results of mechanical testing, the hardness and tensile strength values are greater than the standard, which are 300 HBW and 621 Mpa, respectively, with a high elongation value, which is 21.8%. The results of metallographic observations showed that the martensite phase was formed but in small amounts in the heat affected zone (HAZ) area with needle-like grain shapes. This martensite phase acts as a stress concentration which is the starting point for cracks when the cold forming process is carried out. The formation of the martensite phase is caused by an inappropriate preheat process and the heat input is too large.

Kata Kunci

Ellipsoidal Head; Pressure Vessel; ASME SA516 grade 70N; Cold Forming

Teks Lengkap:

PDF

Referensi

Amanie, J, I N A Oguocha, dan S Yannacopoulos. 2012. "Effect Of Submerged Arc Welding Parameters On Microstructure Of SA516 Steel Weld Metal". Canadian Metallurgical Quarterly 51 (1): 48-57.

Amin, Samir A., Mohannad Y. Hanna, dan Abdulaziz S. Khider. 2020. "Study Of Mechanical Properties Of Carbon Steel Plates SA-516 Gr. 70 Welded By SAW Using V-Shape Joint Design". Engineering And Technology Journal 38 (2A): 152-165.

B4T report: “Failure Analyses Head V 5010”, 2008

Datta, R., Mukerjee, D., Jha, S., Narasimhan, K. dan Veeraraghavan, R., 2002. Weldability characteristics of shielded metal arc welded high strength quenched and tempered plates. Journal of Materials Engineering and Performance, 11(1), pp.5-10.

Grange, R. A. "Effect of microstructural banding in steel." Metallurgical Transactions 2, no. 2 (1971): 417-426.

Grange, R., Hribal, C. dan Porter, L., 1977. Hardness of tempered martensite in carbon and low-alloy steels. Metallurgical Transactions A, 8(11), pp.1775-1785.

Kumar, Pankaj, H. K. Arya, dan Sandeep Verma. "Effect of post weld heat treatment on impact toughness of SA 516 GR. 70 Low Carbon Steel Welded by Saw Process." International Journal for Research in Applied Science & Engineering Technology (IJRASET) ISSN: 2321-9653.

Lu, Y., Yu, H. dan Sisson Jr, R.D., 2017. The effect of carbon content on the c/a ratio of as-quenched martensite in Fe-C alloys. Materials Science and Engineering: A, 700, pp.592-597.

Moss, Dennis R., dan Michael Basic. Pressure Vessel Design Manual. 4th ed. Amsterdam: Elsevier/Gulf Professional, 2013.

Oyyaravelu, R., Kuppan, P. dan Arivazhagan, N., 2016. Metallurgical and mechanical properties of laser welded high strength low alloy steel. Journal of Advanced Research, 7(3), pp.463-472.

Raghavaiah, Nelaturi. (2020). BPVC Sec VIII div 1 and 2. 2. 525-526.

Suryo, S. H., dan Y. Umardani. "Calculation program for steel weldability by considering the heat affected zone (HAZ) width of welded joint." Metalurgija 59, no. 2 (2020): 153-15.

Refbacks

  • Saat ini tidak ada refbacks.