Posted by: novembri yusuf | January 4, 2010

DOWNHILL PROGRESSION DALAM VERTICAL WELDING

Dari pengalaman dilapangan banyak para inspector atau contractor dilapangan kurang sreg dengan downhill progression karena anggapan penetrasi yang kurang.


Anggapan tersebut memang beralasan, namun harus dipahami juga dari design calculation tidak semua member fillet weld vertical menghendaki deep penentration, sehinnga pada kondisi tertentu downhill progression bisa membantu produktifitas tanpa mengurangi requirement yang diperlukan.


Article di bawah ini bisa memberikan sedikit gambaran tentang technik downhill progression.

We use either downhill or uphill welding in the vertical position. Downhill welding is carried out with a downward progression, conversely, uphill moves in an upward progression. Downhill welding is often used for fillet welding of steel sheets due to the following advantages over uphill welding.


(1) Faster welding speed

(2) Easier to obtain small-leg fillet weld

(3) Shallower penetration

(4) Lower heat input due to faster welding speed

(5) Less welding distortion


However, downhill welding can inhibit penetration and generate slag inclusions unless a welder can control the arc to track correctly on the welding line at fast speeds (e.g. 60 cm/min or higher with a 1.2-mmφwire). The following measures can prevent defects in vertical fillet downhill welding.


(1) Use the straight run technique without weaving.

(2) Control the welding torch so that the work angle is 45 degrees and the drag angle, 5-15 degrees as

shown below.




Another difficulty with downhill welding is that it tends to cause a concave bead having an insufficient throat (concavity) in vertical fillet welding. To overcome this problem, two-layer welding is recommended as shown in the following figure. Even in the second layer, again, use the straight run technique without weaving.


With respect to welding wires suitable for downhill welding, the following choices are recommended in conjunction with suitable droplet transfer mode and application.


(1) Solid wires for welding sheet metals by using a short-circuiting arc at the low current range (e.g. 50- 160A for 1.2mmφ wire), such as MG-51T (ER70S-6)

(2) Flux-cored wires for welding sheet metals by using a short-circuiting arc at the low current range (e.g. 50- 180A for 1.2mmφ wire), such as MX-100T (E71T-1, E71T-1M)

(3) Flux-cored wires for welding thin plates by using a globular arc at the middle to high current range (e.g.200-300A for 1.2mmφ wire), such as DWA-50 (E71T-1M), DW-100 (E71T-1), DW-110 (E71T-1),and MX-Z210 (E70T-1)


Before employing downhill welding, weldpenetration, joint alignment tolerance and the welders skill should thoroughly be examined to ensure that the weld satisfies the requirements. For your information, AWS D1.1 (Structural Welding Code Steel), for example, specifies that a change from uphill to downhill or vice versa is the essential variable requiring requalification of the welding procedure specification.

Source : Cobelco News



Responses

  1. Excellent Blog Here. I found about Shellmax. They supply extensive range of welding equipment, plasma welding machines, helmets, mig tig welders, stick & spot welders.

  2. wah bagus banget articelnya pak.
    dari pengalaman saya juga kebanyakan di site lebih suka uphill progression .

  3. Curriculum Vitae

    Name : Agus pajar yanto
    Place/date birth : Bekasi, 14 Agustus 1986
    Jenis Kelamin : Pria
    Religion : Islam
    Martial : Singgel
    Adderess : Kp. Kemang Jl. Masjid Rt.01 Rw.12 No. 22
    Jaticempaka Pd.Gede Bekasi 17411
    Phone Home : (021) 8499 6850
    Phone Mobile : +62 813 8967 3789

    Classification
    Welder :SMAW,GMAW,GTAW,FCAW
    Course
    1. Pengelasan pipa 5G SMAW (Down Hill) yang diselenggarakan oleh BLK Pengembangan las Condet pada tanggal 22 April 2008 sampai dengan 07 Agustus 2008 (Bersertifikat).
    2.Pengelasan pipa dengan posisi 6G peroses GTAW-SMAW yang di selenggarakaan oleh BLK pengembangan las condet pada 12 Mei 2009 sampai dengan 27 Agustus 2009(Bersertifikat).
    Pengalaman Pekerjaan/working experience
    .PT.ADI GUNA S&E from (06 March 2005 to 28 Mei 2005)
    Beginning & final classification :Welder
    Location :JL.Sindang laut 100.TANJUNG PRIOK,
    JAKARTA
    .PT.HAMER ENGINERING(09 Mei 2006 to 29 February 2008)
    Beginning & final classification : Maintenance
    Location :JL.Raya Jatimakmur,BEKASI
    .PT.WARNA WARNI MEDIA (16 february 2009 to 25 juli 2009)
    Beginning & final classification :Welder
    Location :JL.Blora No.8 Jakarta 10310
    .PT.SS Danisa Nusantara(01 April 2010 to 02 Oktober 2010)
    Beginning & final classification :Welder
    Location :JL.Jenderal Sudirman NO.1 Kayuringin,Bekasi
    Location Projek :Unilever Walls&Rinso,JABABEK Cikarang
    .PT.Sigma Mutiara(01 Desember2010-1 Maret 2011)
    Beginning & final classification :Welder Location :JL.Pantai Indah Kapuk Utara 2,Galeri Niaga
    Mediterania 1 Blok f No 8f.Jakarta Utara
    Location Projek :Kutai Barat,KALTIM
    .PT.Nani Wahyuni Industries(01 April 2011 to 5 September 2011)
    Beginning & final classification :Boiler Maker
    Location Komplek SenteraNiaga kav.No 12&15,Bulevar
    . Hijau,Pejuang Medan Satria,BEKASI 17131
    Location Projek :PT.MISP Pontianak,KALBAR


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