Fig 11 - available via license: Creative Commons Attribution-NonCommercial 4.0 International
Content may be subject to copyright.
Source publication
Shrinkage cavities and large inclusions are serious internal defects of heavy steel ingot and influence the quality of subsequent forgings. In order to remove these two types of defects, a 70 t 12Cr2Mo1 heavy ingot fabricated by vacuum carbon de-oxidation process was sectioned and investigated by means of structure observation and EDS analysis. To...
Similar publications
The preparation process of complex thin-wall magnesium alloy castings based on numerical simulation and rapid prototyping core making method is presented in this paper. The filling and solidification processes were simulated using ProCAST to optimise the gating system. The simulation results showed that compared with bottom gating system, vertical...
The centrifugal casting process of 6082 Al alloy was simulated by ProCAST software. The effects of rotation speed and heat transfer coefficient on the filling and solidification behaviour were analysed. The porosity of the cast pipe increases with the increase of the rotation speed and decreases with the increase of heat transfer coefficient. The C...
The complex shape of the casting pump body has large complicated structure and uniform wall thickness, which easy give rise to casting defects. The numerical simulation software ProCAST is used to simulate the initial top gating process, after analysis of the material and structure characteristics of the high-pressure pump. The filling process was...
The high pressure die casting process is extensively used to manufacture light metal parts with high productivity. A major drawback of the process is the relatively high variability in mechanical properties and poor repeatability between casting cycles, limiting the achievement of weight reduction through lighter design. Although it has been establ...
An attempt is made to model the design of grain selection during single‐crystal solidification of an Ni‐based superalloy by the Bridgman method. Various geometrical designs of the starter block and spiral grain selector are chosen and their effects on crystal orientation of the single‐crystal part are studied. The competitive grain selection is sim...
Citations
... The liquid enrich in solute flows under the action of gravity and natural convection, resulting in the formation of macrosegregation [1][2][3][4][5] of the ingot. In addition, large ingot also has inclusions [6][7][8][9], shrinkage porosity [10][11][12] and other defects. In the subsequent processing, macrosegregation and inclusions and other defects are difficult to eliminate, reducing the performance of the product, and even leading to its direct scrap [13,14]. ...
A novel method by adding inorganic heat absorption material (IHAM) into the molten steel was proposed to improve the quality of large steel ingots. The IHAM was found to melt and float up after absorbing the heat of molten steel, stirring the melt and thus accelerating the cooling process. The molten steel was also purified as the inclusions were adsorbed during the floating of IHAM. The addition of IHAM rod was conducive to increase the equiaxed grain ratio (EGR) and alleviate the central carbon segregation, while the IHAM cored wire played a more important role in reducing the inclusion index. This method holds broad appeal to solidification of large steel ingot, as it can improve the microstructure of solidified ingot. ARTICLE HISTORY
... The solute-enriched liquid flows under the action of gravity and buoyancy, leading to the formation of macrosegregation in the ingot [1][2][3][4] . In addition, large ingots also have defects such as inclusions [5] and shrinkage porosity [6] . During the subsequent processing, such defects are difficult to be eliminated, reducing the performance of products and even leading to direct scrapping [7,8] . ...
It has been demonstrated that heat absorption method by using the inorganic material rod to cool the molten steel can significantly reduce the macrosegregation level of the large steel ingot. However, owing to the opacity of the molten steel, the physical mechanism of the heat absorption method is not clear. In this work, a transparent hydraulic physical model with water and paraffin wax was built to simulate the melting and floating processes of inorganic materials in the molten steel. A mathematical simulation was also carried out to analyze the connection between the actual ingot and the physical model. Results show that it is feasible to simulate the molten steel and inorganic materials with water and paraffin wax. With the help of the physical model, the process of the melting of paraffin wax and its floating to the surface of water were clearly observed, during which the temperature of water at some characteristic positions in the mold was recorded. The visualization findings demonstrate that the melting and floating processes of paraffin wax can help to bring the heat from the center of the mold to the top surface more quickly, which reduces the superheat and significantly accelerates the cooling rate of water. The experimental results show that for the water with a certain superheat, the use of a larger mass of paraffin wax can accelerate the cooling of the water, but there is a risk of incomplete melting of the paraffin wax. A higher superheat of water will lead to a quicker melting rate for a given mass of paraffin wax, while a lower superheat leads to the incomplete melting of paraffin wax as well.
... -physical heterogeneity (shrinkage cavities, V-shaped cracks, porosity); -chemical heterogeneity (macrosegregation, microsegregation, 'A'-segregation); -structural non-homogeneity. Currently, there are a number of works [1,[4][5][6] considering the problems of ingot solidification and the development of internal defects inside them. Computer modeling is the most advanced method which enables us to assess the effects of heating and pouring process parameters on solidification [7][8][9][10][11]. ...
The paper reports findings on mathematical modelling of ingots of different geometry. It is established that V-shaped cracks concentrated in the ingot bottom are gradually removed through upset, while arch-shaped cracks located around the sedimentation cone top open up. A computer simulation made it possible to calculate efficient deformations in the workpiece axial zone. An alteration of the ingot geometry leads to an increase in efficient deformation and, consequently, a better treatment of axial areas and elimination of the axial defects of the ingot metal.
The inhomogeneity in large ingots not only decides the final properties of the product, but also restricts downstream hot working processing severely. It is very important to improve the homogeneity of ingots for saving energy, improving material utilization ratio, increasing performance of component, and the construction of key equipment. In this paper, the general inhomogeneity problem in large ingots, such as macrosegregation, inclusion, shrinkage porosity, and large crystal have been introduced. The evolutions of this inhomogeneity in the subsequent hot working processing have also been discussed, based on which the concept of homogeneity window for large ingots has been proposed. The research progress of numerical simulation of macrosegregation in large ingots and some new methods for improving the homogeneity of large ingot have also been introduced and analyzed. Three fundamental reasons for the inhomogeneity of ingots were concluded, i.e. the uneven cooling rate, the uncontrollable multiphase flow, and the solute redistribution during solidification. Aiming at these three fundamental reasons, a novel casting method called layer casting (LC), which has been proposed by our team recently, was introduced to modify the serious inhomogeneity problem in large ingots. In this method, molten alloy was poured into the mold separately and layer upon layer. As soon as the poured molten alloy solidified to a critical volume fraction range, the next layer amount of molten alloy was poured into the mold. For each layer, the mass, composition, and pouring temperature of poured molten alloy could be artificially designed and controlled based on the target homogeneity window. Both experiment and numerical simulated results shown that, in comparison with conventional ingot fabrication method, the LC method can significantly decrease the uncontrollable multiphase flow, uniform the cooling rate, and improve the solute redistribution, subsequently, improve the homogeneity of ingots. For large ingots fabrication, the LC method has the potential to substantially decrease the energy consumption, materials consumption, and the investment of large equipment. Its wide application prospect for high quality large ingots is also expected.
