Dar aralık kaynağında dikiş formuna kaynak parametrelerinin etkisi ve bilgisayar yardımı ile tayini
Computer aided determination of the welding parameters in narrow GAP welding and their effects on the weld
- Tez No: 39258
- Danışmanlar: PROF.DR. SELAHADDİN ANIK
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1994
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 126
Özet
ÖZET Dar aralık kaynağı, 1960'lardan itibaren, özellikle kalın parçalar için uygulanan bir tekniktir, ve nükleer reaktörler, basınçlı kaplar, petrokimya endüstrisi, açık deniz konstrüksiyonları gibi alanlarda gittikçe daha yaygın olarak uygulanmaktadır. Yapılan çalışmada, 7 dar aralık kaynak yöntemi için, bir program yazılmıştır. Bu dar aralık kaynak yöntemleri: 2 tane tozaltı dar aralık kaynak yöntemi, 3 tane gazaltı dar aralık MAG yöntemi, 1 tane gazaltı dar aralık TIG yöntemi ve 1 tane sarılı elektrotlu gazaltı dar aralık MIG yöntemidir. Birinci bölümde, dar aralık kaynağı hakkında genel bir bilgi, ikinci bölümde ise, dar aralık kaynak teknikleri ve özellikleri hakkında ayrıntılı bilgiler verilmiştir. üçüncü bölümde, uzman sistemler tanıtılmış, özellikleri ve kaynak tekniğinde uygulanma alanları hakkında bilgiler verilmiştir. Dördüncü bölümde, konunun önemi ve çalışmanın planlanması ele alınmıştır. Beşinci bölümde, programda ele alman 7 dar aralık kaynak yöntemi tanıtılmış ve özellikleri anlatılmıştır. Altıncı bölümde ise, yazılan program hakkında bilgiler verilmiştir. Programlama dili olarak, C dili kullanılmıştır. Yazı lan programın“exe”dosyaları toplam 7 Mb'dır. Program uzman sistem şeklinde yazılmış olup 222 ayrı program dosyasından oluşmaktadır. Program konu olarak dört kısımdan meydana gelmektedir: - Ana menü ve alt menüler, - Bilgi veren kısımlar, - Hesap yapan ve grafik olarak gösteren kısımlar, - öğüt veren kısımlar (uzman sistem). Uzman sistem kısmında, dar aralık kaynağında yeterince deneyimli olmayan kullanıcılar için, seçilen bazı parametrelere göre, diğer kaynak parametreleri bilgisayar programı tarafından seçilmektedir.
Özet (Çeviri)
COMPUTER AIDED DETERMINATION OF THE WELDING PARAMETERS IN NARROW GAP WELDING AND THEIR EFFECTS ON THE WELD SHAPE SUMMARY In recent years, structures have been getting bigger, leading to a greater amount of high quality thick steel plates being used. In welding this category of steel, it is important to secure the quality of weld zone on the one hand and, to reduce the welding cost on the other. Conventional methods (e.g., electroslag welding and electrogas welding) proved to be inadequate for this application. In this respect, narrow gap welding (NGW) has long been viewed as a very promising technique. Distinguishing features of NGW are the following: 1-Narrow gap welding is actually a special technique, not a process (in contrast to conventional GMAW, SAW, etc.). NGW is utilized in many coventional arc welding processes, especially GMAW (unlike ESW, which is not an arc process). In this respect, it would be true to speak of the narrow gap GMAW (GMAW-NG) process, the narrow gap SAW (SAW-NG) process, or simply NGW (if applied to any welding process), but the term“narrow gap welding process”is not logically justified. 2-NGW requires for the most part a square-groove joint, but a V or double V groove is also acceptable, provided that the groove angle (usually very small) is selected on the basis of distortion compensation. In contrast, for SAW, GMAW, etc., the groove angle (sometimes small also) is chosen for better access to the joint. 3-NGW is a multiple-pass technique, unlike ESW, electrogas or high density SAW. 4-NGW fills the groove with a constant number of weld beads per layer (usually one or two) that are deposited one on top of the other, unlike conventional welding processes with V or double-V grooves. vix5-NGW operates with low or medium heat input, in contrast to ESW or SAW. 6-NGW has all-position capabilities, while ESW and SAW operate only in the flat position. Economy is one of the most attractive features of narrow gap welding and, obviously, the thicker the plate is, more attractive is narrow gap welding. This fact is recognized by all of the authors, but due to the differences between manufactures it is difficult to make exact comparisions between narrow gap welding and other conventional welding methods. There are several basic reasons which make narrow gap welding highly economical; -Joint preparation is both very simple and economical. -Joint finishing rates of narrow gap welding are quite high. -Reduction in consumables is an important factor in reducing overall fabrication costs. -Electric energy consumption is also lower in narrow gap welding because of a smaller number of weld passes and lower heat input. -The all-position capability of narrow gap welding is an adventage in comparison with submerged arc welding and electroslag welding processes, which are usually associated with welding in flat and vertical positions, respectively. This reduces the necessity for cranes and other handling facilities for large heavy components, and can cut the fabrication costs dramatically when critical assembly welds must be made under on-site conditions. -Postweld heat treatment can be avoided in some applications of narrow gap welding, because of the favorable fine dendritic microstructureof the weld and the narrow heat effected zone which promotes minimal coarse grain growth. This can save a great deal of energy and reduce the total cost if fabrication. -The one-side welding capability of narrow gap welding contributes to cost reduction because it considerably simplifies welding, gouging and weld root cleaning procedures and makes it easier to automate the welding process. NGW has certain advantages over conventional welding processes, including: 1-High productivity, which is a result of a much simpler shape and smaller cross-section of the square narrow groove, consuming less labor for joint preparation and welding operations, less filler materials, and less energy. All-position and one-side welding capabilities of NGW and potential for elimination of the necessity for vi 11postweld heat treatment are favorable contributions to the overall cost reduction of NGW. 2-High quality of weld, which is a result of low heat input and multipass retempering of beads, by subsequent overlaying passes in the deep narrow groove. This leads to an extremly narrow heat-affected zone, and fine grained weld metal structures which are smaller and more uniformly dispersed. The mechanical properties of the welded joint, particularly fracture thoughness and fatigue strength characteristics, are improved, making NGW an excellent means for joining not only mild steel but also low alloy high strength and high alloy steels, and aluminium and titanium alloys. 3-Reduced residual streses, which result from smaller volumes of molten weld metal; this leads to reduction of the tensile residual stress zone (width and maximum value). Distorsion in narrow gap welds is smaller, making its control much easier in the weldment. 4-Capability of performing automatic welding in all positions due to the small volume of the molten weld pool and low heat input. This is very important for welding under field conditions. 5-The technical qality of narrow gap welding makes possible reversal of a basic design concept. That is, instead of designing heavy section parts for large thick wall components such as large castings, narrow gap welding may enable design engineers to substitute a welded structure. Drawbacks of the process are the following: 1-Reliabi 1 ity of the existing equipment is not very high, due to excessive complexity. 2-The equipment available on the market is quite expensive. 3-The process is sensitive to any disturbance of the arc, which has a detrimental effect on weld quality. 4-The repair procedure requires alternative welding methods. IXDespite the variety of modifications observed; equipment for narrow gap welding (GMAW-NG) consists of the following principal items: -Specially designed (or ordinary) welding torch (or torches) containing water-cooled, electrically insulated contact tubes (which can be inserted into the narrow groove) and gas shielding devices, electrically insulated and attached to the contact tubes. -Wire feeding system, containing: electrode wire feeder (usually standart), special wire (or torch) oscillation device, and control-cast device (for NGW-I) or wire straightener (for NGW-II). -Seam tracking system to follow the corner of the joint (standard or special) or optical arc monitoring device. -Proximity sensing system to maintain constant contact tube -to-workpiece distance (standard or special). -Standard (or special) welding power supply for each torch. -Water supply unit for cooling the torch. A typical system for submerged arc welding narrow groove may consist of the following components: -Welding power source (standard or special). -Welding wire feeding system (standard or special). -Welding head(s) of special design. Means of automation, including stabilization control (joint tracking and height control) and programming capabi 1 ities. -Suplemental equipment, including flux/slag processing equipment. Ther are four classes (nine levels) of automation in the classification established depending on a system's progressively incrased capability to perform the above- described operations: Class 1 (Levels 1 and 2)- mechanized systems. Class 2 (Level 3)- general purpose automation. Class 3 (Levels 4 - 6)- programming automation. Class 4 (Levels 7 - 9)-robotics. By the range of performance capabilities, submerged arc narrow gap systems are inferior to gas metal arc narrow gap ones and belong to Levels 3-5 in the above classification (versus Levels 2-6 in gas metal arc narrow gap welding). Main investigators and users of narrow gap welding are U.S.A., Japan, Russia, Germany.In this thesis, 7 methods of narrow gap welding has investigated and computer programs have been written. These methods are submerged arc narrow gap welding, gas shielded arc narrow gap welding (MAG, TIG) and narrow gap GMA welding with twist wire. In the first chapter, the importance of the subject is emphasized. In the second chapter, the principles and fundamentals of narrow gap welding are explained. Especially, submerged narrow gap welding and gas metal arc narrow gap welding are explained in detailed. Mechanical properties, welding characteristics, equipments, cost analyses of these methods are described. In the third chapter, metods used for programs are described and the chemical compositions of experiment materials, properties description of mechanical tests, properties of welds, defects are described. In the fourth chapter, computer program is introduced. Photographs of program are given, and parts of program are explained. In the fifth chapter, results and advices are discussed. And important of the program is emphasized. Program language is C. Main compuer program consist of 95 individual programs (exe files). Total length of the exe files are 7 Mbytes. Total length of 222 cpp and h files are 2.3 Mbytes. Computer program consist of 3 parts. These are; - Knowledge. - Calculations and graphics. - Expert system. Names of knowledge parts of the program are yöntemler, ağızlar, paso düzeni, ağız azalması, karakteristikler, hatalar, kimyasal, çekme, çentik darbe, sertlik. Names of calculation and graphic parts of the program are alanlar, seçim, hesap, grafik. Name of expert system part of the program is genel. xiExpert systems are systems that are designed to simulate the behaviour of a human expert as he or she attempts to solve complex problem in a particular domain. These systems differ quite significantly from conventional computer systems in the following ways: 1-The expert system can emulate a human expert in that it can give advice rather than handle data, e.g., the preferred course of action from the options available. 2-The line of reasoning can be explained, e.g., why that particular course of action is being recommended. 3-As the knowledge is held in rules, rather than as data, the system is adaptive, i.e., it can learn from experience, and the field of expertise can grow. 4-A conventional program consist of data plus an algorithm, but an expert system contains facts, rules and an inference engine. Thus, an expert system is essentially software which encapsulates the specialist knowledge of a human expert in a from in which it can be accessed by other users. In the same manner as talking to an expert, uncertain data (opinions) can be handled, the results of interrogating the program are usually expressed as judgmental knowledge or advice, and explanations of its reasoning can be supplied on request. Xll
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