Ingot Processing Research Articles

Optimizing cooling strategies in the Czochralski process for large-diameter silicon ingots

As the semiconductor industry shifts towards larger wafer sizes, such as 300 mm and 450 mm, controlling defects is crucial to ensure device performance and yield. Conversely, a high cooling rate is essential for achieving higher production rates. Therefore, finding the optimal cooling strategy is critical to maintaining high production rates while ensuring high-quality wafer production. This paper employs a simulation model to investigate the impact of various cooling strategies on point defect formation during the CZ process for 450 mm diameter silicon ingots. Using the 3D energy equation coupled with the Navier-Stokes equation and moving mesh theory, the transient CZ process is simulated, incorporating defect evaluation equations. Beside original CZ puller configuration, two cooling strategies are examined: one with a small gap and long cooling jacket (Case II) and another with a large gap and short cooling jacket (Case III), compared against a baseline setup (Case I). The simulations reveal that Case II, while enhancing the crystallization rate, increases non-uniformity. Conversely, Case III produces a flatter solid-liquid interface and lower defect concentrations, achieving a maximum Cv-Ci of 0.4 × 1014 cm−3, compared to 1.1 × 1014 cm−3 and -2.5 × 1014 cm−3 in Case I and II. These findings suggest that adjusting cooling strategies can significantly impact the quality and uniformity of large- diameter silicon ingots.

Influence of forging pretreatments on microstructure evolution and surface roughness of Al 6061 alloy

Achieving ultra-smooth surfaces is the goal of aluminum optical manufacturing. Under certain processing conditions, improving the microstructure of aluminum and understanding its relationship with surface roughness requires systematic study. The grain structure and various types of second-phase particles are of paramount importance. This study analyzed the microstructure of 6061 alloy after undergoing severe plastic deformation under various processing conditions followed by T6 homogenization heat treatment. Utilizing a white light interferometer, a comparative analysis of the surface roughness was conducted on specimens that underwent single-point diamond turning to achieve a mirror finish. The assessment of surface roughness on machined surfaces is solely based on white light interferometry. The analysis and discussion focus on the effects of phases (causing scratches and voids), the grains and grain boundaries. Experimental findings signify: the grain size, grain boundary and residual second phase can both influence the surface quality, the increase in deformation temperature and accumulated strain both facilitate the dissolution and fragmentation of the secondary phases. However, they also contribute to some extent to grain growth, resulting in a minimum secondary phase area fraction of 0.87% and grain sizes reaching 147.8 μm. Subsequent heat treatments, while effective in reducing the negative impact of the phases, reveal noticeable step-like structures affecting the quality of surface roughness, with the lowest obtained Ra value being 0.8 nm. A proposed pretreatment method in cleaner ingot processing with lower alloy element content addresses the trade-off between reducing phases and controlling grain growth, aiming to achieve improved surface roughness, promoting the application of polycrystalline aluminum alloys in the field of optics manufacturing.

Numerical simulation study on solidification proceoss of titanium slab ingot by electron beam cold hearth melting

Abstract Titanium and titanium alloys are key basic support materials in the field of engineering technology and high technology, and are widely used in the fields of natural gas transportation, chemical corrosion, and marine development. Titanium alloy ingots are often prepared with more solidification defects such as surface cracks and cold shuts, resulting in lower utilization of titanium metal and higher cost of titanium products. The root of this is the lack of in-depth knowledge of the ingot melting and casting process, and the failure to control the thermal conditions of the billet in the molding process within a reasonable range. In this study, based on the Lagrange Euler algorithm, combined with ProCAST finite element software to establish a numerical model, revealing the solid-liquid interface morphology, the length of the transition region, and the change rule of thermal stress under the influence of different process parameters in the solidification process of titanium slab ingot. The results show that with the increase in pulling speed, the depth of the solid-liquid phase line and the width of the mushy zone of slab ingot increase, and the length of the transition region grows. With the increase in casting temperature, the depth of the solid-liquid phase line of the slab ingot decreases, and the mushy zone gradually becomes narrower. The casting temperature and pulling speed are positively correlated with the value of the thermal stress equivalent stress in slab ingots, and the probability of cracks in the corners and ingot surface is higher. This study provides effective theoretical guidance for the realization of stable mass production of high-quality titanium slab ingot.

Crystallization processes for photovoltaic silicon ingots: Status and perspectives

The choice of the crystallization process plays a crucial role in determining the quality and performance of the photovoltaic (PV) silicon ingots, which are subsequently used to manufacture solar cells. Silicon ingots are typically grown using either the Czochralski (Cz) process or the direction solidification (DS) method, with each technique influencing the microstructure and defects density as well as the final solar cells’ performance. In this work, we describe these two processes with a brief overview of the main challenges. For monocrystalline silicon ingots, we discuss the role of crucible and bubble development as well as structure loss. For multicrystalline silicon ingots, we briefly review some of the methods that have been developed in the past years and present results of high-performance multicrystalline (HPMC) ingots.

Development of a technique for simplified simulation of the thermomechanical processing of large ingots

Development of a technique for simplified simulation of the thermomechanical processing of large ingots

Digital-Twin-Based Monitoring System for Slab Production Process

The growing demand for high-quality steel across various industries has led to an increasing need for superior-grade steel. The quality of slab ingots is a pivotal factor influencing the final quality of steel production. However, the current level of intelligence in the steelmaking industry’s processes is relatively insufficient. Consequently, slab ingot quality inspection is characterized by high-temperature risks and imprecision. The positional accuracy of quality detection is inadequate, and the precise quantification of slab ingot production and quality remains challenging. This paper proposes a digital twin (DT)-based monitoring system for the slab ingot production process that integrates DT technology with slab ingot process detection. A neural network is introduced for defect identification to ensure precise defect localization and efficient recognition. Concurrently, environmental production factors are considered, leading to the introduction of a defect prediction module. The effectiveness of this system is validated through experimental verification.

Force calculation and new design of the grip unit pliers metallurgical crane

In the rolling shops of metallurgical enterprises connected with the processing of steel ingots in the preparation (slabbing, blooming) well taps with pincer grabbers are used. Such cranes work in the sections of heating wells, where they are used, first of all, for planting ingots in the well and issuing them for rolling after heating. In addition, cranes can be used to perform auxiliary operations for well maintenance and equipment repair. During the design processing of tong grippers of such cranes, there is a need to determine the ingot clamping forces, which in this gripping device are related to the weight of the ingot itself and the weight of the tongs of the crane. In addition, the design features of the clamping zone itself are of great importance, that is, the design of the parts that transfer the clamping forces to the ingot. These parts are called cores. It is clear that the clamping force and the design of the cores must guarantee reliable retention and safe movement of the ingot. During the operation of the crane, the cores are subjected to a wide range of loads: shock, compressive, crushing loads from impact. At the same time, being in contact with the heated ingot, they themselves heat up to the same temperature. And because they are periodically cooled in tanks with water, they work even in conditions of cyclic heat changes. The design and physical condition of the cores are of great importance for the reliability of the tick gripper. Untimely replacement of cores can lead to negative consequences during ingot retention, cause it to break off with the destruction of the circle, damage to floor equipment and danger to service personnel. Several options for new, more effective designs are proposed in the work based on the force calculation of the pincer gripper and the analysis of the advantages and disadvantages of modern core designs. The authors created a mathematical model of the interaction between the core and the ingot to check the depth of penetration of the core into the body of the ingot and compared it with the indicators of known cores. It was found that at the ingot release temperatures, the depth of penetration into the body of the ingot for cores of the new design is 4 times less than for conventional conical cores. The use of these designs will ensure the reliability of the gripping device while simultaneously improving the quality of the workpiece by reducing the number of cracks and dips associated with damage to the faces of the ingot from deep indentation of the cores

Using the Radial Shear Rolling Method for Fast and Deep Processing Technology of a Steel Ingot Cast Structure.

In advancing special materials, seamless integration into existing production chains is paramount. Beyond creating improved alloy compositions, precision in processing methods is crucial to preserve desired properties without drawbacks. The synergy between alloy formulation and processing techniques is pivotal for maximizing the benefits of innovative materials. By focusing on advanced deep processing technology for small ingots of modified 12% Cr stainless steel, this paper delves into the transformation of cast ingot steel structures using radial shear rolling (RSR) processing. Through a series of nine passes, rolling ingots from a 32 mm to a 13 mm diameter with a total elongation factor of 6.02, a notable shift occurred. This single-operation process effectuated a substantial change in sample structure, transitioning from a coarse-grained cast structure (0.5-1.5 mm) to an equiaxed fine-grained structure with peripheral grain sizes of 1-4 μm and an elongated rolling texture in the axial part of the bar. The complete transformation of the initial cast dendritic structure validates the implementation of the RSR method for the deep processing of ingots.

A Study on the Volume Reduction Ingot Process for Flame Resistant Expanded Polystyrene Recycling

A Study on the Volume Reduction Ingot Process for Flame Resistant Expanded Polystyrene Recycling

Improving quality of cast monocrystalline Si ingot with seed crystal strips and graphite soft felt

A combination of the two techniques, one that employs seed crystal strips and the other that makes use of graphite soft felts have been proposed and studied to improve the casting process of monocrystalline Si (mono-Si) ingots. The evolution of the melting process of Si seed crystals and the growth of edge Si muliticrystals during the cast of mono-Si ingot has been investigated in detail. The results of the study indicated that these two changes increased the proportion of full mono-Si wafers substantially and led to a considerable reduction in the average dislocation ratio of edge Si bricks based on cast mono-Si ingot. Solar cell devices fabricated based on cast mono-Si ingot with the above two improvement measures exhibited enhancement in their overall photoelectric conversion efficiency (η) by 0.29% and 0.64% (absolute value), in comparison to the solar cells based on mono-Si ingot that was cast using only the seed crystal strips and the conventional ingot, respectively. Therefore, the study provides sufficient evidence that utilization of seed crystal strips and graphite soft felts in combination with each other as supplementary measures to the casting process of mono-Si ingot can be scaled up to be used in the photovoltaic production line for the development of solar cells with higher performance.

Influence of technological parameters during multiwire cutting of GaAs ingots on the surface characteristics of the plates

Mechanical processing of semiconductor monocrystalline ingots is one of the key stages in the production of GaAs wafers. The main issue for obtaining high-quality plates is to determine the optimal parameters of machining and is to identify the dependencies of the surface quality of the substrates after cutting on the parameters set in this technological process. Technology for the production of polished semiconductor wafers (substrates) almost all semiconductor materials have a similar and has in its difference only a number of distinctive features related to the mechanical and structural features of individual materials. Mechanical processing is the first stage after crystal growth, in which it is necessary to observe and improve many technological parameters to obtain high-quality finished products. In the technological process of semiconductor processing, it is necessary first of all to divide the crystal into plates with similar surface characteristics. The quality of this separation determines which plates will eventually turn out and how suitable they will be as substrates for the production of devices in mass production. The study of the influence of cutting parameters on the structure of the disturbed layer and the basic geometric parameters of the plates allows us to identify the optimal parameters of mechanical cutting and to identify the range of deviations possible to obtain plates of similar quality for further processing.

Elimination Mechanism of Shrinkage Porosity During Pressurized Solidification Process of 19Cr14Mn4Mo1N High-Nitrogen Steel Ingot

Elimination Mechanism of Shrinkage Porosity During Pressurized Solidification Process of 19Cr14Mn4Mo1N High-Nitrogen Steel Ingot

Numerical simulation of cellular automaton in vacuum arc remelting during the solidification process

In this paper, the finite element and cellular automaton coupling (CAFE) model is used to simulate the solidification process of a large ingot during vacuum consumable arc melting (VAR). The effects of melting temperature, melting rate, and mold cooling coefficient on temperature field distribution and solidification structure were studied by simulation. The results show that the microstructure predicted by the numerical method is consistent with the experimental results. As the melting temperature increases from 1500 °C to 1800 °C, the depth of the molten pool increases from 14 mm to 24 mm, the width of the mushy zone decreases from 10 mm to 9 mm, and the average radius of the grains increases from 584.3 μm to 679 μm. With the increase in melting rate from 6 kg min−1 to 12 kg min−1, the maximum depth of the molten pool increases from 4 mm to 32 mm, the width of the mushy zone increases from 8 mm to 13 mm, and the average grain radius decreases from 943 μm to 497 μm. As the cooling coefficient of the mold increases from 1000 W m−2·K−1 to 5000 W m−2·K−1, the depth of the molten pool decreases from 16.7 mm to 12 mm, the width of the mushy zone decreases from 7.3 mm to 5.9 mm, and the average radius of the grains increases from 630 μm to 1303.5 μm.

Control of the growth quality by optimizing the crucible structure for growth of large-sized SiC single crystal

Silicon carbide (SiC), as the wide bandgap semiconductor, has gradually attracted attention from investigators due to the excellent integrated performance, widely recognized as a revolution in the electronic devices. For these applications, it is crucial to prepare the high-quality SiC crystal ingot by optimizing growth parameters and crucible structures. In this study, the effect of TaC coating and graphite paper on the growth process of SiC ingot were investigated compared to the growth in conventional graphite crucible through modeling and experiment. We demonstrated that the grown crystal using TaC-coated graphite relay ring and graphite paper surrounded the inner wall of powder container shows the superior characteristics in terms of the crystalline perfection and interface shape. In addition, the new crucible structure can provide a low-cost solution to prepare SiC crystal ingot using PVT method.

A Quasi In-Situ Study on the Microstructural Evolution of 2195 Al-Cu-Li Alloy during Homogenization.

An optimized homogenization process for Al alloy ingots is key to subsequent material manufacturing, as it largely reduces metallurgical defects, such as segregation and secondary phases. However, studies on their exact microstructural evolution at different homogenization temperatures are scarce, especially for complex systems, such as the 2195 Al-Cu-Li alloy. The present work aims to elucidate the microstructural evolution of the 2195 Al-Cu-Li alloy during homogenization, including the dissolution and precipitation behavior of the TB (Al7Cu4Li) phase and S (Al2CuMg) phase at different homogenization temperatures. The results show that there are Cu segregation zones (Cu-SZ) at the dendrite boundaries with θ (Al2Cu) and S eutectic phases. When the temperature rises from 300 °C to 400 °C, fine TB phases precipitate at the Cu-SZ, and the Mg and Ag in the S phases gradually diffuse into the matrix. Upon further increasing the temperature to 450 °C, TB and θ phases at the grain boundaries are coarsened, and an S-θ phase transition is observed. Finally, at 500 °C, all TB and S phases are dissolved, leaving only θ phases at triangular grain boundaries. This work provides guidance for optimizing the homogenization procedure in 2195 alloys.

Numerical Investigation on Solidification Shrinkage Behavior of P900 Hollow Ingot during Electroslag Remelting Process

A numerical model coupled with a multiphysical field based on a simple density‐based shrinkage model is established. After validation by comparing the experimental and simulation results, it is utilized to clarify solidification shrinkage behavior of electroslag remelting hollow ingot (ESR‐HI) process and investigate the effect of the inner mould taper angle and ingot withdrawing rate on air gap width and interfacial heat transfer coefficient (HTC). The interface between the hollow ingot and the inner mold can be divided into three regions, according to the change in heat transfer mechanisms. In region I, the inner wall and the inner mould are in complete contact, and effective HTC is maximum. In region II and region III, effective HTC decreases with increment in the air gap width. With increasing the inner mould taper angle and ingot withdrawing rate, solidification shrinkage at a given height of hollow ingot decreases. Moreover, it is reasonable that the inner mould taper angle is set to 1.5°, the distance from the slag‐metal interface to the bottom of the cylindrical section (Hcyl) is set to 20 mm, and the withdrawing rate is set to 5 mm min−1 for P900 during ESR‐HI process with a cross‐sectional size of Φ300 mm/Φ100 mm.

Obtaining tube blanks from copper-nickel alloy МНЖ 5-1 when using a tool made of die steel adjustable austenitic transformation during operation

Purpose. Production of die tool from steel with regulation of austenitic transformation during operation to increase the level of service life during hot deformation of copper-nickel alloy.
 Research methods. Metallographic, high-temperature X-ray phase and dilatometric analyzes of research steel.
 Results. The mode of heat treatment (incomplete annealing) of steel 4Х3Н5М3Ф at a temperature of 750±20 °С, obtained by electroslag remelting, allowed to obtain a perlite-sorbitol structure at a hardness of33–34 HRC and allowed better machining by cutting the workpiece alloy. The proposed mode of final heat treatment (hardening 1030±10 °C and tempering 600±5 °C) of the investigated steel, makes it possible to heat the matrix during operation to a temperature of 600 °C.
 Scientific novelty. The thermal stability of the tool for hot deformation can be significantly increased when using steel with adjustable austenitic transformation during operation. Such steel in the initial state has a ferrite base, and when heated to operating temperatures occurs from α-Fe to γ-Fe conversion and, subsequently, the austenitic structure is preserved throughout the period of high-temperature operation of the stamping tool. It is confirmed that the stamping tool made of steel 4Kh3N5М3F when pressing a copper-nickel alloy works in the temperature range corresponding to the austenitization process.
 Practical value. Abbreviated technological operation, namely thermo-deformation processing (forging) of ingots obtained by electroslag remelting. Experimental-industrial tests of the die tool of steel 4Х3Н5М3Ф in the manufacture of tube blanks of Ø 67±0,1 mm from a copper-nickel alloy of the МНЖ 5-1 brand are carried out. As a result of research “Artemovsk plant for processing of non-ferrous metals and alloys” (Bakhmut, Donetsk region, Ukraine) at an operating temperature of 900–950 ° C, matrices made of steel 4Х3Н5М3Ф (without deformation-forging) showed stability in three times higher than the matrices from steel 3Х3М3Ф made at the enterprise.

THE INFLUENCE OF EXTERNAL FORCES ON THE CHARACTERISTICS OF HARDENING AND THE CHARACTER OF CONVECTIVE FLOWS DURING THE CURING OF INGOTS

The paper describes the influence of external influences on the features and nature of convective flows during the solidification of ingots. It is shown that topping up the profitable part of the ingot with hot portions of the melt changes the nature of the convective motion of the melt in the body of the model ingot. Laminar movement is observed before refilling, after turbulent. The change in the nature of the movement of the liquid in the body of the ingot contributes to an increase in the speed of the front of the solid phase, as evidenced by the results of calculating the rate of solidification throughout the solidification process of the model ingot. The analysis of the structural zones showed an increase in the zone of columnar crystals from 58.6% to 72.3% and the zone of the deposition cone, from 6.5% to 9.1% in refilled ingots compared to the classic ingot. There is also a decrease in the zone of differently oriented crystals from 26.8 to 13.7% and the crustal zone from 5.9% to 2.8%. The length of the axial zone increased from 36 to 54%, with a decrease in its diameter from 6.5 to 5.1%.

Influence of Riser Necking Ratio and Taper on the Solidification of Heavy Ingots by Numerical Simulation

The effect of riser necking ratio and taper on solidification process of 96T steel ingot have been studied numerically using the software package ProCAST. The results show that the solidification time decrease with the increase of riser necking ratio, and the position of shrinkage porosity moves up and the secondary porosity presents a tendency of increase, and the inclusions on the shoulder of body ingot decreases. The riser taper has little effect on the solidification process of heavy ingots.

Effect of Pressure on Inclusion Number Distribution During the Solidification Process of H13 Die Steel Ingot

In order to clarify the influence mechanism of high pressure on inclusion number distribution, the changes in phase transition sequences, key properties, and heat transfer boundary conditions with pressure have been investigated. Furthermore, the inclusion number distribution of H13 die steel ingot under different pressures (0.1, 1, and 2 MPa) has been numerically simulated by the mathematical model verified using the experimental results of cooling rate and the parameter ηn. The changes in key properties and phase transition sequences with pressure were investigated by Thermo-Calc software. With increasing pressure from 0.1 to 1000 MPa, the suppression of ferritic phase (δ) formation and improvement of liquidus/solidus temperature are obvious, but the density, thermal expansion coefficient, specific heat, and latent heat of solidification barely change. Meanwhile, the effect of pressure on heat transfer boundary conditions has been quantitatively revealed with formulas proposed by experimental measurement and numerical calculation: hf,0.1 = 1137.4t−0.23 (for 0.1 MPa), hf,1.0 = 1294.3t−0.23 (for 1 MPa), and hf,2.0 = 1501.6t−0.23 (for 2 MPa). During solidification process, gravity, buoyancy, and drag forces play the key roles in affecting the movement behavior of inclusions. Moreover, their net force drives inclusions to sink downward near the tip of columnar dendrite, and move counterclockwise. With increasing pressure from 0.1 to 2 MPa, the enrichment degrees of inclusions in ingot decrease, and the distribution of inclusion number becomes more uniform due to the stronger escaping ability of inclusions and the weaker inclusion trapping ability of the mushy zone.