Lowest weight loss with a single layer is obtained, using sk 900 ni rtcg with the cmt process. Ferrite number control in austenitic stainless steel welding. Ferrite number is an arbitrary standardized value designating the ferrite content of an austenitic stainless steel weld metal. To prevent hotcracking, austenitic stainless steel welds generally contain a small percent of delta ferrite. This paper explains the various materials and welding processes that can be used. May 03, 2014 cooling rate of weld metal, is the major one that controls the ferrite number in austenitic stainless steel weld deposits. What are your thoughts on the required nde for alloy weld overlay deposit in a pressure vessel.
Introduction for over 50 years, the relationship be tween weld metal ferrite content and sus ceptibility to weld solidification cracking in austenitic stainless steels has been well recognized refs. Metallographic and chemical analyses of the fusion zones of the joints were conducted. For purposes of discussion, in welding there are three zones of principal concern. Effect of ce addition to filler metal on microcracking. So the selection of electrode diameters, arc length, amperages current and heat treatments are the controlling parameters that influence the ferrite number. Results indicate that weldments produced from e 30816. Oct 28, 2008 the main difference between cladding and weld overlay is that weld overlay by codes and standard definition is deposited by a fusion welding process, and not applied by mechanical methods. Welding austenitic stainless steel overlays on low alloy high carbon steel is especially difficult, because of the 22 multiplier for carbon. Our stateoftheart equipment and processes deliver a high deposition rate and outstanding weld chemistry. Fn has been adopted as a relative measure for quantifying ferritic content using standardized magnetic techniques.
Hydrogen cracking of ferriticaustenitic stainless steel weld. Metallographic analysis was made on the weld metal and the heataffected zone as well. This is generally only a problem with the use of the fully automated tig welding process, a manual welder being capable of coping with the variations in penetration. Microstructural evolution during solidification of austenitic. Avoiding cracking in austenitic ss weld overlays american.
Steel castings handbook supplement 7 welding of high alloy. The post weld thermal stabilization heat treatment would be the same heat treatment as previously discussed. Choosing processes and parameters that minimize dilution is critical for a successful overlay. Materials are type 304l stainless steel and mediumcarbonsteel. Manual metal arc welding method was used to produce the joints with the tungsten inert gas welding serving as the control. A method of producing a weld overlay on a ferrous base metal surface, by applying to the surface by electric arc welding a plurality of layers of an austenitic stainless steel filler of specific composition, and providing a flux which produces a substantially fully austenitic overlay at least in the uppermost layer. For austenitic stainless steel weld overlay, the composition of the finished weld overlay deposit from the surface to the specified minimum overlay depth should conform to asme specification sfa5. Tappi produced the first guideline for stainless steel weld overlay of digesters in 1962. The weld pool in a low sulphur steel weld pool in a low sulphur steel weld bead. The process also is highly customizable, allowing manufacturers to choose from a broad selection of materials to layer and alloy multiple surfaces together. The ductilitydip cracking susceptibility in the reheated weld metal could be greatly improved by adding 0. Epa was used to identify the defect that occurs in the weld metal.
This is normally done to improve the material by adding either a corrosion resistant or hardfacing layer to it. Three different electrode compositions were used to overlay weld austenitic manganese steel cast in the form of rail heads. Stainless steel cladding and weld overlays 109 clapding metal. Hardfacing materials generally consist of carbide, nickel, cobalt or ironbased alloys supplied in a rod, wire or powder form to suit the process being used. Dec 12, 2008 a successful procedure for the surfacing weld on the dissimilar filler metal does not mean the surfacing material is compatible with the base metal or vice versa. The stressstrain analysis in multipass welds was conducted using the thermo elastoplastic finite element method. The test results show a similar yield strength, and a small difference on tensile strength for fissured and fissurefree 316l weld deposits. Welding variables and microfissuring in austenitic.
The ferrite contents in the weld deposits will be on the order of 5 10% ferrite depending on the alloy. The occurrence of microcracks, especially ductilitydip crack in multipass weld metal during gtaw and laser overlay welding processes of nibase alloy 690 was predicted by the mechanical approach. Test pads and butt welds were made with changes in the welding variables of principal concern in manual weld ing, i. After welding, clean the weld area to remove slag and heat tint to examine the weld integrity and also to allow the metal to be painted. A slight decrease in arc voltage will cause the weld. In opposition to thermal spraying, which provides a mechanical bond with the substrate, the hardfaced weld overlay forms a metallurgical bond with the substrate.
Corrosion control by modern weld overlay technology. Two of the electrodes were obtained commercially and the third was of novel chemical composition and was produced in our laboratory. Hardfacing hardfacing welding weld overlays hfw industries. These numbers 1 have been assigned to base metals and filler metals alike. Jan 11, 2019 a weld overlay is a type of cladding that uses a welding process to melt a material onto the surface of another, different material. Table 4 mo segregation in weld metal weld metal bulk mo content, wt % dendrite core, wt% interdendritic region, wt% s31254 6. Weld overlay can be used to restore structural integrity, corrosion protection, hardfacing to deter wear and abrasion. Elsevier microstructural evolution during solidification of austenitic stainless steel weld metals. This welding process combined with automatic overlay welding involving fast oscillation results in fine cellular dendritic subgrain struture for austenitic alloys, showing no carbide precipitation. This does not change the need for pre and pot weld heat treatments, however, because the dilution of the base metal with nickel increases the probability of martensite formation. Cladding on alloys that have 30 points of carbon or higher, even slight increases in dilution can cause cracking.
Stabilization heat treatment of austenitic stainless steel. Conversely, when convex weld surfaces are created, the internal shrinkage forces will pull the surface into compression. The effect of electrode types on the solidification cracking susceptibility of austenitic stainless steel weld metal was studied. Weld overlay wol, also known as cladding, hardfacing, weld cladding, or weld overlay cladding, is a process where one or more metals are joined together via welding to the surface of a base metal as a layer. Facing the practical difficulties in reducing the diffusible hydrogen content of fluxcontaining welding consumables like fluxcored arc welding fcaw wires, the present study investigated the microstructural aspect to improve the hydrogeninduced cold crack hicc resistance of multipass weld metal of 600mpa strength. They are either 100% austenite or austenite with a small amount of ferrite see table 1. Deposits are 100% fused for greater reliability and a longer life. On those few occasions when heavy wall austenitic stainless steel piping needs to be stress relieved e. Austenitic stainless steels are metalurgically simple alloys.
If possible, blast the weld area with iron free grit but if that is not possible, grind along the weld line to avoid dragging carbon steel contamination onto the stainless steel. The predominant material selected for weld overlay of continuous digesters is type 309 stainless steel. Mechanical behavior of austenitic stainless steel weld metals. The effect of ce addition on microcracking susceptibility in the multipass weld metal of alloy 690 was investigated in order to improve the microcracking susceptibility in it. Microcracking susceptibility in reheated weld metal, microcracking in multipass weld metal of alloy 690 part 1, sci. Austenitic stainless steel is known for best welding properties and excellent corrosion resistance. Filler materials for 6%mo superaustenitic stainless steels. Charpy impact test was carried out and the composition of the weld metals was also analyzed.
Welding variables and microfissuring in austenitic stainless. Effect of electrode types on the solidification cracking. Cladding and weld overlay materials oerlikon metco. Pulse sprayed gas metal arc welding psgmaw has been selected for the weld overlay process. We use a continuously fused alloy weld metal overlay barrier to deliver superior results. The purpose of the asme weld number tables is to support a numbering system methodology that helps to make welding procedure creation and welding procedure management much easier as well as more affordable. A weld overlay is performed to protect the base material from wear or corrosive environments. The degree to which these changes occur, and their effect on the finished weldment in terms of resistance to corrosion and mechanical properties depends upon alloy content, thickness, filler metal, joint design, weld method, and welder skill. Kulkarni department of metallurgical engineering and materials science and tregional sophisticated instrumentation center, indian institute of technology, powai, bombay, 400. Mechanical approach for prediction of microcracking in.
Our portfolio includes materials for wear and corrosion resistance, and surface restoration. So you can proceed with a simple butt weld between 316 plates of 6mm or same as internal plate thickness. Plastic strain in the weld metal accumulated with applying the weld thermal cycle in multipass welding. Microcracking in multipass weld metal of alloy 690 part 3. It should be used in place of percent ferrite or volume percent ferrite on a direct replacement basis. Best regards al topic american welding society services certifications asme overlay inlay thickness. Solidification behavior and cracking susceptibility of pulsed. In general, the single layer solution provides substantial savings in overlay time and welding consumables. Ferrite content in austenitic stainless steels rolled.
Mechanical behavior of all weld metal specimens of 308l and 316l weld with and without microfissures was evaluated by standard and prestrain tensile testing. Cladding and weld overlay materials each of our cladding and weld overlay products have been designed for a specific weld process with tightly controlled particle size distribution and morphology. Consideration also must be given to difficulties that might arise from the. This is a precaution against solidification cracking during welding. Is it necessary to apply ut to check for disbonding as is applied to clad plate given that with weld overlaid plate fusion strength between the alloy material and the base carbon steel has to be proven in the pqr. Us4609577a method of producing weld overlay of austenitic. Welding variables and microfissuring in austenitic stainless steel weld metal microfissuring is best overcome by optimization of consumable composition since control of welding variables alone will not guarantee its avoidance and since cta remelting and pulsed smaw are of limited practical application by t. Stainless steel weld overlay is typically applied for pr otection of carbon steel digesters from corrosi on. This is not the ferrite to be found in carbon steel but a high temperature form known as delta. Microcracking could be completely prevented in the dissimilar multipass weld metal of alloy 690 to type 316l stainless steel by using two kinds of filler metals containing 0.
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