Reducing Shrinkage Porosity in High-Performance Steel Castings: Case of an ASME B16.34 Gate Valve Body: Part 2—Simulation and Experimental Verification

Mahomed, Nawaz; Kleynhans, Hendrik Andries

doi:10.1007/s40962-018-0275-7

Cited by 10 publications

(4 citation statements)

References 11 publications

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“…This approach attempts the elimination of impurities and entrapped gases within molten metal [13]. Sound castings are dependent upon the considerations such as neglection of steep temperature or stress variations [22], controlled quality of surface [23], appropriate design of air vent, flow stability [24], proper modelling of runner and riser [25] etc. Poor degassing of molten metal leads to residual impurities, mainly entrapment of gaseous form of elements like phosphorous, sulphur, hydrogen, oxygen and nitrogen.…”

Section: Casting Of Uns N06003mentioning

confidence: 99%

Study on Defect Reduction in Casting of Ni-Cr alloy (UNS N06003)

Samvatsar

Dave

2022

IOP Conf. Ser.: Mater. Sci. Eng.

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In modern times, selection criteria of materials are solely based on its utilization. The characteristics of materials like high temperature sustainability with regard to its strength and corrosion resistance is the primary requirement to satisfy its operations. Industries categorised in sectors like energy, manufacturing, electronics etc. greatly rely on input materials and their purity decides their performance. Amongst many developed alloys, nickel-based alloys find their position in applications having temperatures from cryo to nuclear ranges. One of such unique materials, being used from minute components of semiconductor industry to huge components of marine industry is UNS N06003. It is basically Ni-Cr based alloy having greater than three-fourth fraction of nickel. For major applications wrought material is widely used, but cast material marks their positions in selected applications. This paper deals with casting of UNS N06003 and improving its quality. The reasons associated with cast defects and drawbacks of defects in terms of performance have been discussed. To minimize casting defects and produce a sound casting, this research adopts a novel approach of removal of unwanted gaseous elements. In degassing stage, molten metal is introduced with the combination of calcium-based fluxes which mainly remove the entrapped gases and lighter impurities in the form of slag. It has been found that the addition of quicklime (CaO) in combination with calcium carbide (CaC2) resulted in reduction of gaseous elements like nitrogen, phosphorus and sulphur. Up to 33% reduction of gaseous elements has been detected.

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Section: Casting Of Uns N06003mentioning

confidence: 99%

Study on Defect Reduction in Casting of Ni-Cr alloy (UNS N06003)

Samvatsar

Dave

2022

IOP Conf. Ser.: Mater. Sci. Eng.

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“…Multiple considerations are required for getting uniformity and soundness in the casting. These considerations are good sprue and vent design, avoidance of large stress and temperature gradients [15], surface finish control [16], casting process design optimization [17] etc. Metallographic studies have shown that casting defects exist either in the form of minor isolated defects or in the form of clusters that are interconnected to each other in all the three dimensions [18].…”

Section: Importance Of Casting Qualitymentioning

confidence: 99%

A Brief Study on Defect Reduction of Cast Fe-Ni-Cr Alloy (UNS N08120) for Petrochemical Industry

Samvatsar

Dave

2022

Advances in Science and Technology

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In the current advancing world, operability and ease in processability of a material define its selection criteria for the intended applications. Hence, the industrial applications requiring high temperature sustenance, strength and corrosion resistance desperately demand the materials which employ simple processing in an economical way. Contemplating last few decades, it has been discovered that industries like petrochemical, power generation, nuclear energy, etc. greatly relied on nickel-based alloys till Fe-Ni-Cr based alloys were not introduced. The usable components are obtained either in cast or wrought form as per requirements. Fully killed alloy, developed under controlled conditions with some precautions during the casting process can lead to sound casting. The current study adopts a novel preliminary approach to control the quality of cast UNS N08120 material and minimize the possibility of defect generation. The possible reasons behind cast defects and how they transform into intrinsic defects have also been discussed. Calcium-based fluxes are introduced to molten metal as a degassing agent for the elimination of lighter impurities and entrapped gases. By the addition of quicklime (CaO) as a flux material during the sand casting process, an attempt has been made to reduce the presence of gases and impurities by more than 80%.

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“…Knowing the liquidus temperature (T l ) allows a better choice of T p . It is known that higher values of T p increases the amount of porosity in castings [10], and increases hot tear susceptibility (HTS). The former is due to the increased possibility of hotspots, and the latter due to high thermally-induced stresses in the solidifying melt.…”

Section: Interdendritic Feeding 31 Solidification Characterisation Of Steelsmentioning

confidence: 99%

“…This can also improve material homogeneity (due to backdiffusion of solute); however, it will result in reduced ductility of the material (due to the coarser grain structure). Hence, the optimisation of casting and process parameters for reducing shrinkage porosity may need to be balanced with desired microstructural qualities, leading to multiple (and often conflicting) objectives during the optimisation process [10].…”

Section: Classification Of Shrinkage Porosity Typesmentioning

confidence: 99%

Shrinkage Porosity in Steel Sand Castings: Formation, Classification and Inspection

Mahomed¹

2021

Casting Processes and Modelling of Metallic Materials

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In this Chapter, shrinkage porosity defects in steel castings are analysed, particularly for low carbon, high alloyed steels, which have applications in critical engineering components. It begins with the mechanisms for porosity formation within the solidification contraction phase of the casting cycle, highlighting the importance of feeder design. This is followed by characterisation of the solidification phase of steel alloys, including the evolution of phases, which is important in distinguishing between microstructure and porosity in microscopy analysis. A more detailed discussion of interdendritic feeding and mechanisms for shrinkage micro-porosity is then provided. This leads to the well-established interdendritic flow model and commonly-used thermal criteria for shrinkage porosity prediction. The discussions are then consolidated through the classification of shrinkage porosity in terms of formation mechanisms and morphology, and its causes relating to composition, design and process conditions. Finally, engineering standards for classification and inspection of porosity types and severity levels in steel castings are discussed. Throughout, basic design and process improvement approaches for improving melt feeding during solidification contraction is given, with emphasis on providing practical solutions for prediction and evaluation of shrinkage porosity defects in castings.

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Reducing Shrinkage Porosity in High-Performance Steel Castings: Case of an ASME B16.34 Gate Valve Body: Part 2—Simulation and Experimental Verification

Cited by 10 publications

References 11 publications

Study on Defect Reduction in Casting of Ni-Cr alloy (UNS N06003)

Study on Defect Reduction in Casting of Ni-Cr alloy (UNS N06003)

A Brief Study on Defect Reduction of Cast Fe-Ni-Cr Alloy (UNS N08120) for Petrochemical Industry

Shrinkage Porosity in Steel Sand Castings: Formation, Classification and Inspection

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