Gemi İnşasında Kaynaklı Birleştirmeler, Kaynak Sıraları Ve Uygulamaları

Abstract

Bu çalışmanın ilk kısmında her türlü kaynaklı bağlantılar da karşılaşılan kalon gerilme ve deformasyon problemlerinin oluşum nedenlerine ve önlemlerine değinilmiş, ayrıca kaynak kabiliyetini ve seçilecek dolgu metallerinin tespitinde etkili olan gemi inşa çeliklerinin mekanik ve kimyasal özellikleri üzerinde durulmuştur, İlerleyen kısımlarında ise sırasıyla toleranslar dahilinde ve verimli kaynaklı üretim için günümüzde uygulanmakta olan montaj, çektirme ve alıştırma sistemlerine değinilmiş ayrıca Lloyd kurallarına ve genel kaynaklı tasarım esaslarına göre malzemelere uygulanacak kaynak ağzı standartları açıklanmıştır. Tüm bu kriterlerin paralelinde en az gerilmeyle, mümkün oldukça deformasyonsuz bağıntılar elde etmek, sonuçta tekneye daha uzun bir yorulma ömrü kazandıracak şekilde kaynaklı imalat için tekne inşasında uygulanması gereken kaynak sıralarından geniş biçimde pratik uygulamalardan örnek verilerek bahsedilmiştir. Bu tezin son kısmı ise, bir çelik tekne inşasının başlangıcından kızak'dan indiriliş aşamasına kadar geçen süreçte uygulanan kaynaklı imalatı ve önemli konstrüksiyonlardaki uygulanmış ve başarılı sonuç vermiş kaynak planlarını kapsamaktadır.

This study involves informations and practices concerning probable matters, during welding operation, detected in the manufacturing. The first chapter 's subject is rules of hull structural stells determined by Amerikan Burneau of Shipping ( ABS) and Germanischer Lloyd. This rules include the chemical and the mechanical properties of ordinary strength steels, high strength steels and quenched and tempered steels. Using this knowledge, it'll be very easy to select the correct filler metal, ensuring the mechanical requirement. Meanwhile if preheating is needed, for high strength steels or stells over 20 mm thickness, the preheating temperature can determined calculating the carbon equalent using the chemical composition of the metal. In addition the weldability of steels are also explained in this chapter. The main two factor to classification steel,such as A grade, AH32 grade, DH32 grade and EH32 grade are, are yielding point of the metal and the absorbed energy at low temperatures. The high strength steels absorbed energy are higer than ordinary steels at the same temperature. The chemical composition of the metal effects the weldability. Adding some alloy elements, such as Mn, Si, Mo, Ni and V, to the steel makes the steel strength higher. The third chapter involves residual stresses, which occurs during welding operations and causes deformation. The strength of the residual stresses changes with some factors such as correct prepared joints, welding pass, welding methods and welding sequence in great xx construction. Preparing too wide welding Joints, too big root gaps and preparing the second side of butt joints too deep by arc gauging causes extra stresses. In detail in this chapter the formation of residual stresses the reasons and the results are explained by giving examples. In addition the calculation of an axial, longitudinal and transverse shrinkage of an fillet weld joint are explained as well. The main two factors to reduce the residual stresses and their results deformations, explained in this chapter, are constructions factor and technolojical factors, The constructions factor involves; welding Length, welding pass, thickness of the material, weld throat thickness, design factors and balancing the weld near the neutral axis. The tehnolojical factor involves; decreasing the welding time, to control the heat input, to notice and take precautions for residual stresses before welding operation, preparing welding plans and applying, using back step welding method and making peening to releasing the residual stresses. All this factors which effects the residual stresses could prevent the stress increase by taking precautions. Stresses result in causes deformations are not acceptable in manufacturing and must corrected. This causes time, workmanship and many consuming. So it's not desirable. In the fourth chapter the subject is assembly methods of the ship on the slipway, fittings-up methods using strong back arrangements and various fittings and welding adge preparations. Because of the effect of the welding result the preparation of assemblies are very important. Due to the technological opportunity, the most common and the best method is blok method. So, adding each bloks on the slipway each other using this kind of arrangement coult prevent the accumulation of the residual stresses in the joint. The main reasons of using this XXI arrangements and fittings is releasing the stresses and preventing the deformation. Whereas using tack welding between the edges causes accumulation of stresses and deformation in the joints. So, the edge preparations for welding have to be done proper to weld. In that reasons in this chapter there are given various welding joint type depending on the thickness of the material, welding method, the weld quality requirement ( required full penetration or not. ), for one side welding joint, repair of wide root gaps at welding and welding materials in different thicknesses. Using the correct joint type and the suitable one could facilitate the welder to obtain the required weld quality. Furthermore there are some restricts for distance between two butt welds, afillet weld and butt welds, to dimensioning the scallops and doublings. The restricts depends on the Lloyd's rules. Moreover to make welding over the tack welded assenbly without problems, rules about tackwelding are explained as well. Too big and too wide spaced and uncorrext made tack welds causes welding faults, such as overlap weld bead in fillet welds. The fifth chapter involves preparation welding plans for the welded structures. Welding plans have been preparing for all joints in the construction. They are consist of the constructions plan, welding sketch, welding method, joint type, welding throat thickness, welding position, proper designed welding sequence,.. filler metal type, time extension and pay group. Welding plans are prepared according to general welding rules and welding sequence rules. The first factor of general welding rules are design factor. If a joint doesnt designed proper to welding, it could make the welding operation difficult. The second factor is material type. High strength steel and steels over 20 mm thickness have to pre-heated at elevated temperature before welding. The third factor is tack welding effects and the welding xxu sequence of tack welds. Another factor is the effect of the welt joint and weld throat thickness. If the welding thickness are not given in the project, than it coult be calculated by the formula given in the Lloyd rules. In ship manufacturing it's advised to prepare a seperate filler metal welding pains and welding throat thickness list for sections. Preparing, a welding plan like that could prevent the use of expensive filler metal. In addition it will be very easy to decide in whichsection which filler metal should be used. The other factors are preparing the joint before welding ( cleaning the rast, dirt and oily surface against porosity ), making the welding in proper position, otherwise welding will be take very long time. The last factor is preheating in required. The second main factor to prepare welding plans and to control the residual stresses and decrease the deformation is welding sequence rules. This involves the main welding sequence rules for welded structures and some special rules used in the ship construction. This welding sequence rules involves welding the bloks and adding each bloks together on the slipway as well. This welding sequences have been using in a shipyard and resul in very good. Examples and photos about this are added at the last chapter and supplements. The last chapters subject is expalaining the welding and manufacturing ranks step by step from begginning to landing the sea. This steps include, pre- manufacturing in the workshop, manufacturing outside the workshop and on the slipway. This steps are explained by giving examples which are used in the manufacturing and result in satisfactory. In the second part of this chapter welding plans of some special and important construction of a container ship are explained. These are stern tube,... pintel bearings, welding the crane pedestral and welding the crane on the ship deck. This works are very important XXIII constructions and have limited deformation tolerances so they have to weld carefully. Because of this importance for this kind of constuctions it is important to prepare welding plans and controlling the shrinkage in each steps from time to time during welding. Making this kind of work and saving the data and the results can give a view for the similar constructions.