Kaynaktaki boşluk ve yetersiz ergime hatalarının tespit edilmesi ve iyileştirilmesi /
Yazar: BERK ÇAKIR
Danışman: PROF. DR. MAHMUT ERCAN AÇMA
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Makine Mühendisliği Ana Bilim Dalı / Üretim Metalurjisi ve Teknolojileri Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2017
Konu: Metalurji Mühendisliği = Metallurgical Engineering

Özet:
Günümüzde şüphesiz 'Kaynak Teknolojisi' çok önemli bir yere sahip olmaktadır.
Kaynak, günlük yaşantımızda elimizi attığımız her şeyde karşımıza çıkmaktadır.
Üzerinden geçtiğimiz köprülerden, raylara, yemeğimizi pişirdiğimiz tencereye;
bindiğimiz otomobilden, otobüslere, uçaklara ve yaşam alanlarımızın inşaatlarına
kadar her alanda boy göstermektedir.
Kaynak teknolojileri alanında söz sahibi ülkeler arasına bakıldığında, Türkiye'nin de
adının bulunduğu görülmektedir. Türkiye'nin bu konumda bulunmasındaki büyük
pay sahipleri ise özel sektör firmaları ve üniversiteler olduğu belirlenmiştir. Bu ikili;
hem üretim kapasiteleri, hem teknoloji geliştirme faaliyetleri, hem de eğitim
çalışmalarıyla Türkiye'deki kaynak sektörünü her geçen gün daha da ileriye
taşımaktadırlar. Öyle ki, özel firmaların üniversiteler ile birlikte geliştirdikleri
teknolojik ürünlerin hızına yetişilememektedir.
Kaynaklı imalatın Türkiye'de giderek yaygınlaşması ve ilerlemesi, kaynakla entegre
çalışan diğer sektörlerinde önlerinin açılmasına yardımcı olmaktadır. Dolayısıyla
ülkemiz kaynak teknolojileri ile beraber bir gelişim süreci geçirmektedir. Yeni
ürünler, yeni çalışmalar ve yeni araştırmalar birbirini izlemektedir. Ayrıca kaynak
teknolojilerindeki gelişmelerin yanında; belgelendirme faaliyetleri, kontrol metotları
ve eğitim konularında da yenilikler gündeme gelmektedir. Bütün gelişmeler gerek
kaynaklı imalat sektöründe gerekse bağlantılı tüm sanayi kollarında ülke
kalkınmasını destekleyen öğeler olarak öne çıkmaktadır.
Fakat hayatta hiçbir şeyin mükemmel olmadığı gibi; bu kadar yaygın kullanım
alanına sahip ve ülkemizin söz sahibi olduğu bir teknolojinin de mükemmel olması
beklenememektedir. Kalite hataları bu sektörün ilerleyişini sekteye uğratmaktadır.
Bunun yanında insan yaşamı ile bu kadar iç içe olması; belli kalite standartlarının
sağlanmasını, üretim hatalarının ve bunların etkilerinin en aza indirilmesini
kaçınılmaz kılmaktadır.
Bu tez çalışmasında, kaynaklı imalat yapan özel bir firmada gözlemlenen; boşluk ve
yetersiz ergime hatalarının tespit edilmesi ve iyileştirilmesi incelenmiştir.
İlk olarak üretim hattından alınan parçaların, radyografik tahribasız muayene
yöntemi ile boşluk ve yetersiz ergime hataları tespit edilmiştir. Tespit edilen hatalar
için kaynak yöntemi sınıflandırılmasına gidilerek analiz çalışması tamamlanmıştır.
Yapılan analizler ışığında, farklı koşullarda deneme kaynakları gerçekleştirilmiştir.
Deneme kaynaklarının radyografik test yöntemi ile uygunlukları kontrol edilmiştir. 
Tüm bu işlem basamakları incelenmiş ve sonuçlar uygulamaya yönelik olarak
değerlendirilmiştir.

Abstract:
Welding is the most common way of permanently jointing metal parts. In this
process, heat is applied to metal pieces, melting and fusing them together to form a
permanent bond. The ideal weld is one in which there is complete continuity between
the parts joined and every part of the joint is indistinguishable from the metal in
which the joint is made. There are about 100 different types of welding and the most
common type is arc welding.
Welding is a kind of new manufacturing process that has only existed for about a
hundred and fifty years but nowadays, there is no doubt for; 'Welding Technology'
has inseparable part of our lives. Welding is confronting for us in everything from
bridges we cross over, rails, pots we cook meals, cars we travel with, buses, planes
even construction of our living spaces. Without welding technology, such structures
could have never been built.
When deep anaysis is performed about the welding technology; we will encounter
Turkey has also a influence on that field. Turkey is one of the most advanced country
in welding technology because of the private sector and the universities.
The widespread and progressive development of welded manufacturing in Turkey is
helping moving ahead of the other sectors that integrated with the welding. New
products have being manufactured, new studies and new researches have being
perfomed progressively. Therefore, welding technology together with the all related
manufacturing tecniques have being comprehensibly developed in our country. In
addition to the all these developments in welding technology field, innovations in
certification activities, control methods and education are on the agenda. All
developments stand out as the supporting items for the development of the country in
all industrial sectors connected to the manufacturing sector.
However as in life nothing is perfect and it is unrealistic to expect being perfect in a
technology that has such a widespread use and application method. Further
development in this field has been slowed down because of the quality mistakes.
Since, it is so intertwined with human life; it is inevitable that certain quality
standards must be ensured, production mistakes and their effects must be minimized.
In this thesis study, detection and elimination of porosity and lack of fusion weld
defects were investigated at a private company in business welded manufacturing.
The general sources of weld defects include improper design and joint preparation,
defects in parent material, improper welding technique and faulty solidification of
molten metal.
Porosity is when gas becomes trapped in the weld as it is being formed. That trapped
gas then develops into small holes. These small holes can be either cylindrical or
spherical in shape While some porosity in small amounts may be considered an
acceptable amount of discontinuity porosity, it is a defect that must be kept to a
minimum.
Lack of fusion is, as it sounds, the failure of the base metal and the filler melt to
combine properly. Even if the base metal does melt, a thin layer of oxide may form,
preventing the two from fusion. This failure of fusion can be caused by low or
inadequate heat, poor weld technique, insufficient gap, or improper edge setup.
First of all, mass production parts have been welded with ESAB Aristo Tig 4000 I
(SMAW & GTAW) and ESAB Mig 502cw (GMAW) welding machines. After that,
they have been inspected with the radiographic non-destructive examination methods
with GE ERESCO 32 MF4-C x-ray unit, to detect porosity and lack of fusion
defects. For the identified defects, the analysis has been completed by going through
the classification of the welding methods as SMAW, GMAW and GTAW.
SMAW is applied without pressure, incorporates the use of a metal arc which is
formed between a covered electrode and weld pool. The electrode consists of a wire
core around which a concentric mixture of silicate binders and powdered materials
such as fluorides, carbonates, oxides, metal alloys and cellulose is extruded. This
covering serves as a source of arc stabilizers and vapors to displace air as well as
metal and slag to protect, support and insulate the hot weld metal. Shielded metal arc
welding method is used for, carbon steel based; forged material and plate welding.
GMAW, involves the use of a metal arc and consumable electrode with externally
added shielding gas. With proper procedure, welding can be performed in all
positions. The shielding gas or gas mixture used in gas metal arc welding is often not
completely inert. Shielding gas may often consist of carbon dioxide alone, carbon
dioxide mixed with argon, or carbon dioxide mixed with several gases. Gas metal arc
welding employs either a solid electrode wire or an electrode with a core of
powdered metal. A variety of ferrous and nonferrous alloys are available. Gas metal
arc welding method is used for, again carbon steel based; flange and plate welding.
GTAW, incorporates the use of a nonconsumable tungsten electrode to sustain the
arc, which is shielded from the atmosphere by externally added gas. GTAW is the
most versatile of the arc processes. Welds can be made with or without filler metal
and very thin materials of just a few thousandths of an inch can be welded. Gas
tungsten arc welding can be used in all welding positions to join just about all
weldable ferrous and nonferrous alloys. The shielding gas utilized in gas tungsten arc
welding is usually inert. Argon is the predominant shielding gas used, though helium
and argon - helium mixtures are sometimes utilized to obtain greater weld
penetration. Gas tungsten arc welding method is used for, inconel based, plate and
plate welding.
After the analysis; these 15 mass production parts with weld defects have to be
repaired. First step of the repair operation is located welding defect on the working
piece according to radiographic film. Second step is cut (3M cubitron II cut-off
wheel) and ground (Karbonsan Zr grinding wheel) the weld seam for elimination of
the weld defect. Third step is welded the area with exactly the same welding method.
Final step of the repair operation is radiographic inspection.
As a consequence of the analyzes that performed, trial resources were realized under
different conditions. The suitability of test pieces with radiographic non-destructive
test method was checked. All these process steps were examined and the results were
evaluated for implementation.