A333 Gred 6 Keluli karbon rendah di Talian Paip – Pencirian mikrostruktur dan kekerasan Properties

Tube ASTM A269 316L Stainless Laporan Pemeriksaan
disember 15, 2018
Spesifikasi API 5L Gred-B ERW talian paip teknikal , 20″DN (508.0 mm)× WT 7.9 mm
disember 29, 2018

A333 Gred 6 Keluli karbon rendah di Talian Paip – Pencirian mikrostruktur dan kekerasan Properties

M. N. Ervina Efzan *, S. Kesahvanveraragu, J. Emerson

1.0 PENGENALAN

1.1 Luar pesisir Pipeline Bahan

Saluran paip di pelantar luar pantai terdiri daripada pelbagai jenis bahan. Selection of material relies upon certain considerations such as cost, keperluan berfungsi, operating conditions of pressure and temperature, kakisan rate and so forth [1-2]. Since there are varieties of pipelines in offshore platform, material selection and those considerations are highly required. Dalam industri luar pesisir, metal is the highly used material that can be assorted into ferrous and non-ferrous metals [1-3]. Logam yang mengandungi besi (Fe) as their premier composition are known as ferrous metals, whereas metals containing other elements are termed as non-ferrous metals [4-5]. besi tuang dan keluli tergolong dalam kategori logam ferus, sedangkan bukan ferus logam adalah termasuk aluminium (Al), Tembaga (Cu), percaya (sn) dan silikon (dan) [3-5]. Menurut Mamdouh [6], ferrous metals are the mostly used metals to build offshore platform pipelines due to the cost effectiveness and capability of withstanding the
keadaan operasi.

1.2 Plain Carbon Steel

keluli karbon adalah bahan yang terdiri daripada karbon sebagai unsur pengaloian utama. Carbon steel is made up of iron (Fe), karbon (C), fosfor (P), deposit (Mn), sulfur (S) dan silikon (dan) [7]. Pada masa ini di pasaran di seluruh dunia, carbon steel is being manufactured and used in large quantities for heavy industries, sistem pengangkutan terutamanya luar pesisir dan perahan minyak [8]. Ini kerana karbon keluli mempunyai kekuatan yang tinggi, kebolehkimpalan yang baik, ketahanan suhu yang tinggi, good surface protection to the external environment and cheaper than other alloy steels such as low alloy steel and stainless steel [3-4].

keluli karbon boleh dikelaskan kepada rendah, medium and high carbon steels based on its carbon content (Institut India Teknologi, 2010). Low carbon steel is also termed as mild steel and usually contains less than 0.3% karbon. Sementara itu, medium and high carbon steels have a carbon content of 0.3 – 0.45% dan 0.45 – 0.75% masing-masing [4][9]. Pipeline industry especially offshore pipelines may not use medium and high carbon steel due to their poor resistance of brittleness and reduction of weldability [10]. Oleh yang demikian, low carbon steel is preferable in offshore pipelines among designers, fabrikasi dan pengawal selia. It covers the pipeline network of high temperature vessels, Penukar Haba, compressors and transmission pipelines [9][10]. Detailed information on the utilization of low carbon steels in offshore processing platform pipelines is tabulated in Table 1. daripada Jadual 1, low carbon steel Type API 5L Grade X52 has the highest tensile strength of 455 MPa, whereas Type API 5L Grade B possesses the lowest tensile strength of 413 MPa.

 

Jadual 1: Jenis keluli karbon rendah di platform pemprosesan luar pesisir mengikut kod dan standard, kekuatan tegangan, komposisi bahan dan aplikasi:

 

 

Tiada.

Codes and Standard

(ASTM/API)

Tegangan

Kekuatan

(MPa)

Komposisi

of Materials

Applications in

Offshore Platform

 

rujukan

 

1

 

A106 Grade B

(Paip Lancar)

 

415

C <= 0.30

Mn <= 1.06

P <= 0.035

S <= 0.035

 

1. Seawater system

2. Water injection

sistem

3. Produced water

sistem

4. Portable water

sistem

5. Dry fuel and gas

sistem

6. Fire water system

7. Glycol and

methanol injection

sistem

8. Inert gas/plant air

piping

 

[2] [11]

[12]

 

2

 

API 5L Grade B

(dikimpal paip)

 

413

C <= 0.28

Mn <= 1.20

P <= 0.030

S <= 0.030

 

[2] [11]

[13]

 

3

 

A671 Grade CC60

(dikimpal paip)

 

415

C <= 0.21

Mn <= 0.98

P <= 0.035

S <= 0.035

 

[2] [11]

[14]

 

4

 

API 5L Grade X52

(Paip Lancar)

 

455

C <= 0.28

Mn <= 1.40

P <= 0.030

S <= 0.030

 

[2] [11]

[13]

 

5

 

A333 Gred 6

(Paip Lancar)

 

415

C <= 0.30

Mn <= 1.06

P <= 0.025

S <= 0.025

1. Flare system

2. Seawater system

3. Fire water system

4. Drain and sewage

sistem

 

[2] [11]

[15]

 

1.3 A333 Gred 6 Low Carbon Steel Pipe

Based on the comprehensive data in Table 1, material type A333 Grade 6 was chosen to analyse the microstructure characterization

and mechanical properties of the material. Secara umum, A333 Gred 6 pipe is called as a low temperature pipe since it may withstand

impact toughness at temperature as low as -45°C [15].

Rajah 1 shows the samples of A333 Grade 6 low carbon steel pipes.

 

2.0 METODOLOGI

2.1 Pencirian mikrostruktur

Menurut Sharmila [17], imej yang dibesarkan adalah penting untuk menyiasat morfologi, mikrostruktur, dan bentuk pelbagai ciri termasuk bijirin, phases and embedded particles. Pada masa ini, there are various microscopy methods widely used in research field such as optical microscopy (ABOUT), imbasan mikroskop elektron (SEM) and transmission electron microscopy (HAS). Menurut Grubb [18], there are various advantages of using an optical microscope such as captures images with high resolution, fast data acquisition and provides more quantitative results. Oleh yang demikian, light microscopy method was used to characterize the microstructure of A333 Grade 6 bahan.

mikroskop optik memerlukan permukaan spesimen untuk menjadi rata, licin dan calar percuma.
Walau bagaimanapun, ia tidak perlu untuk tidak berada dalam apa-apa bentuk tertentu seperti segi empat tepat, circular or other geometries. Seperti, a proper sample preparation was done before conducting the microstructure characterization through optical microscopy. A333 Gred 6 low carbon steel pipe sample was cut into 1 panjang cm, and the scrap metal sheet attached to the sample was removed through grinding process. Selepas memotong sampel, the surface was grinded to remove the rough surface and scratches on the sample. tambahan pula, two different polishing solutions such as polycrystalline diamond (3 mikron dan 1 µm) and non-crystalline colloidal silica were poured evenly on the test pans to ensure an effective polishing process. A reflective surface was attained after completion of polishing process.

Etching is the final step of sample preparation prior to observation of microstructure via optical microscope. Etching is used to mean the physical and chemical peeling of atomic layers of a material [17]. Menurut Niaz [19], nital is the best etching solution for low carbon steels [20]. Lebih-lebih lagi, etching time is an important factor to be considered in order to ensure the sample surface etched up to the exact level. umumnya, low carbon steels need to be etched using nital in time frame from seconds to minutes [21]. A333 Gred 6 low carbon steel sample was etched for 3 min untuk memastikan paparan tepat mikrostruktur. Rajah 2 memaparkan proses punaran daripada A333 Gred 6 karbon rendah permukaan sampel keluli.

Rajah 2: (1) Proses punaran; (2) Selepas punaran dan Cucian Proses

Selepas penyediaan sampel telah siap dengan tepat, microstructure of the material surface was observed through optical microscope under three different optical magnifications, iaitu 10X, 20X dan 50x.

2.2 Vickers kekerasan ujian

The prepared specimen was mounted on the anvil of Vickers tester device under microscopic view. 10 kgf load was then applied and followed by pressing of diamond pyramid into the flat surface of the specimen for a duration of 15 s. Setelah selesai masa kediaman, the dent was observed through microscopic view. The size of the dent needs to be calculated by measuring the two diagonals [22].

3.0 KEPUTUSAN DAN PERBINCANGAN

3.1 Pencirian mikrostruktur

Rajah 3: Mikrostruktur A333 Gred 6 Keluli karbon rendah di bawah pembesaran 10x. Pearlit dan ferit lapisan dilabel untuk membezakan struktur fasa.

Dari hasil mikroskop cahaya, microstructures of the sample surface under magnification of 10X, 20X dan 50x digambarkan dalam Rajah 3, 4 dan 5 masing-masing.

Menurut Scott [23], keluli karbon rendah mempunyai dua komponen utama, which are pearlite and ferrite. Pearlit ditakrifkan sebagai kawasan gelap di mikrostruktur, and it consists of fine blend of ferrite and iron carbide particles. Sementara itu, mengikut Koo [24], pearlite grains are found lying along the ferrite grain boundaries. Sebaliknya, the brighter regions are known as ferrite, dan sempadan bijian antara zarah ferit yang jelas kelihatan. Secara umum, karbon rendah dengan 0.16% kandungan karbon terdiri daripada jumlah pecahan, 0.79% ferit proeutectoid dan 0.21% pearlit masing-masing [24]. Both pearlite and ferrite layers are labelled in Figures 3, 4 dan 5. Sebagai tambahan, microstructures under magnification of 10X and 20X display clear grain boundaries in between the ferrite grains. Rajah 6 shows a shape of ferrite in low carbon steel to justify the statement regarding grain boundaries in ferrite grain.

Rajah 6: sempadan bijian allotriomorphic dalam keluli karbon rendah [23]

Kepentingan menganalisis mikrostruktur bahan, terutamanya keluli atau aloi, is to determine the properties of the material by observing the particle size and amount in the material itself. Berdasarkan hubungan Hall-Petch, the reduction of grain size improvises the strength of steel [25]. Begitu juga, daripada keputusan yang diperolehi melalui mikroskop optik, low carbon steel Type A333 Grade 6 terdiri daripada saiz yang lebih kecil sempadan bijian ferit.

3.2 Vickers kekerasan ujian

Menurut data yang dihasilkan daripada Bahagian 2.2, Vickers hardness test results depend on the applied load, kediaman tempoh dan kasturi diameter. Oleh yang demikian, untuk ujian ini, 10 kgf was applied for 15 s untuk mengensot pada Gred A333 6 spesimen keluli karbon rendah. The test was repeated on 5 kawasan yang berbeza dari spesimen, yang termasuk 4 edges and a midpoint of the sample. Once the Vickers indenter made a pit on the specimen in a form of the diamond shape pyramid, garis pengisi telah diselaraskan ke tepi kedua-dua pepenjuru, and the values were recorded in the device. kemudian, keputusan telah dipaparkan dari segi HV, which shows the hardness level provided by Vickers hardness tester. The obtained results include diagonal diameters and hardness values for 5 mata, and the average HV for the sample is demonstrated in Table 2.

Jadual 2: Kekerasan Nilai yang Sample A333 Gred 6 Keluli karbon rendah

Keluli karbon rendah: A333 Gred 6

(20 mm x 10 mm x 2 mm)

Rectangular Specimen

Point

diameter 1 (µm)

diameter 2 (µm)

Vickers kekerasan (HV)

1

330.075

332.100

169.131

2

336.960

340.605

161.535

3

336.555

333.315

165.268

4

329.670

326.835

172.065

5

328.455

333.720

169.131

Average Vickers Hardness Value

166.826

 

The results obtained were verified by the microstructure of the indentation through optical microscopy. Rajah 7 depicts the microstructure sample of the diamond shaped indentation on Point 1, 3 dan 5 spesimen masing-masing.

Ia menunjukkan bahawa terdapat sedikit perbezaan antara keputusan Kekerasan Nilai (HV). Although the test was done on 5 mata yang berbeza, the hardness values obtained should be identical due to the same tested material. Menurut Tanaka dan Kamiya [22], surface roughness influences the measurement of hardness value. Although the specimen surface was grinded evenly, terdapat kemerosotan dalam ketepatan hasilnya. Walau bagaimanapun, mengikut Samuels [26], tahap kekerasan keluli karbon rendah (0.1% kandungan karbon) adalah 140HV. Sementara itu, the results obtained for A333 Grade 6 low carbon steel show that the hardness value is about 166.826HV.

4.0 KESIMPULAN

keseluruhan, dapat disimpulkan bahawa A333 Gred 6 low carbon steel possesses microstructure with smaller grain size and less pearlite content. This information has validated the high strength and ductility of the material. Sementara, hardness mean value of this material is 166.836HV, dan ia mematuhi julat nilai kekerasan untuk saluran paip minyak dan gas, yang maksimum 250HV. Sejak A333 Gred 6 low carbon steel has appropriate crystal structure and hardness level, ia adalah sesuai untuk digunakan sebagai platform bahan saluran paip luar pesisir.
Lebih-lebih lagi, the outcome of this paper could contribute to further research on offshore pipeline material.

 

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Komen ditutup.