Fundamentals of HARDFACING by Arc Welding Cracks
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Fundamentals of HARDFACING by arc welding cracks fretting cavitation abrasion erosion preheating adhesion thermal fatigue cracks abrasion cracks cavitation tribology buffer layer hardness rebuilding corrosion preheating abrasion hardness hardfacing erosion abrasion hardness cracks hardfacing wearhardness thermal fatigue erosion fretting corrosion cavitation abrasion tribology preheating rebuilding cracks buffer layer adhesion Fundamentals of hardfacing by fusion welding Founded in 1966, the WELDING ALLOYS Group has developed over the years as a manufacturer of cored wires for welding and hardfacing. Its know-how and the technology that it has created have allowed it to become a specialist in hardfacing solutions using semi- or fully automatic continuous arc welding processes. Regardless of the industry you work in, you are faced with wear. Its effect on your equipment and installations leads inevitably to loss of production and greatly affects the profitability of your business. With more than 50 years’ experience, WELDING ALLOYS’ mission is to provide you with solutions to overcome the adverse effects of wear. This document is designed to help you to choose the ideal hardfacing solution. Our technical ‘Spark’ solves your industrial challenges Written by: Bastien GERARD Welding Engineer, WELDING ALLOYS France With the participation of: Lauren CALVERT Marketing Executive, WELDING ALLOYS GROUP Mario CORDERO Manager R&D, WELDING ALLOYS GROUP Clive PEASE Development Engineer, WELDING ALLOYS France Matt REIFF Welding Engineer / Commercial Sales Manager, WELDING ALLOYS USA, Inc. welding-alloys.com 1 Contents 1. What is wear? 4 5. Characterisation tests for your hardfacing 26 1.1. Definition .................................................................................................................................................... 4 5.1. Characterising the base metal: sparking and magnetism..........................................26 1.2. Mechanisms ............................................................................................................................................. 4 5.2. Hardness tests ......................................................................................................................................28 5.3. Abrasion tests ........................................................................................................................................30 2. Different types of wear 5 5.4. Die penetrant testing .........................................................................................................................32 2.1. Low and moderate stress abrasion / low impact ............................................................... 5 2.2. High stress abrasion / under pressure ..................................................................................... 6 6. Chosing the right hardfacing consumable 33 2.3. Severe abrasion (gouging) / high impact ............................................................................... 6 6.1. Standard classifications according to EN 14700 .............................................................33 2.4. Adhesion / friction ................................................................................................................................. 7 6.2. Description of the elements ..........................................................................................................34 2.5. Erosion ........................................................................................................................................................ 7 6.3. Classification by product family ..................................................................................................36 2.6. Cavitation ................................................................................................................................................... 8 6.4. Choosing a buffer layer ...................................................................................................................44 2.7. Thermal fatigue ...................................................................................................................................... 9 6.5. Choosing the right consumable for hardfacing .................................................................46 2.8. Fretting ........................................................................................................................................................ 9 6.6. Product selection questionnaire ................................................................................................ 48 2.9. Corrosion.................................................................................................................................................... 9 7. Various micrographic structures 50 2.10. Combined wear .................................................................................................................................10 8. Examples of industrial applications 52 2.11. Summary table ...................................................................................................................................11 9. Our automated hardfacing machines 62 3. Hardfacing terminology 12 3.1. Rebuilding................................................................................................................................................12 3.2. Buffer layer ..............................................................................................................................................13 3.3. Hardfacing ...............................................................................................................................................13 4. Hardfacing by arc welding 14 4.1. Benefits of hardfacing ......................................................................................................................14 4.2. Hardfacing welding procedures .................................................................................................14 4.3. Dilution .......................................................................................................................................................18 4.4. Bead patterns ........................................................................................................................................19 4.5. Shrinkage cracks.................................................................................................................................22 4.6. Preheating temperature ..................................................................................................................22 2 welding-alloys.com welding-alloys.com 3 In the following section, we shall meet the various types of wear. For now it 1 What is wear? is useful to keep in mind that the main effect of wear is a visible deterioration of the part. 1.1. Definition There are three main modes of action: cutting (i.e. forming chips), Wear is defined as a progressive deterioration through loss of material due to deformation and gouging/chipping. prolonged or overly frequent use. It degrades the condition of a part, leading to a loss of performance. Pressure Pressure Pressure For the user, this entails: Speed l reduced lifetime and productivity l increased risks to personnel Speed Speed l higher energy consumption & lower yield Combined, these factors can reault in significant costs. It is therefore essential to factor in the effects of wear on the life of the product: Planning for wear in your maintenance and repair operations is one of the keys to the success of your business. Cutting Distortion Ripping This document will demonstrate the importance of hardfacing, used as a preventive or as a remedial measure. Illustration of the three main modes of wear action 1.2. Mechanisms The study of interacting surfaces in relative motion and its effect on friction and wear 2 Different types of wear is referred to as “Tribology”. To achieve the best possible characterisation of wear mechanisms in metals, three elements have to be understood: 2.1. Low and moderate stress abrasion / low impact l The base material, or substrate, is characterised by its chemical composition This type of wear is the result of particles rubbing/ and, its production method (rolled, forged, cast), i.e. its mechanical sliding on the substrate. As the pressure from these properties. Component geometry also plays a fundamental role. This abrasives is very low, they don’t change size and information allows us to understand its susceptibility to wear and the welding don’t break up. conditions required during repairing, rebuilding, and/or hardfacing. Since the angle of attack of these particles is very l The external element (abrasive) which causes wear of the substrate is low, the term “micromachining” is sometimes used. characterised by its dynamic and physical properties. Its hardness, shape, and texture determine the level of damage it will cause, depending on the The following terms are used in the field: pressure, speed, and angle of contact with the substrate. l “Low stress abrasion”, where two bodies are involved the abrasive and the substrate. l The environment in which the wear occurs is an essential factor in choosing the ideal welding solution. Operational conditions such as temperature, l “Moderate stress abrasion”, where three bodies are involved two surfaces pressure and humidity should be characterised as far as possible. moving against each other with an abrasive between them. 4 welding-alloys.com