Bimetal Casting Research Articles

A Novel Approach of Optimum Time Interval Estimation for Al-7.5Si/Al-18Si Liquid-Liquid Bimetal Casting in Sand and Metallic Moulds.

This work describes a novel approach for Al-7.5Si/Al-18Si liquid-liquid bimetal casting in sand and metallic moulds. The aim of the work is to facilitate and develop a simple procedure to produce an Al-7.5Si/Al-18Si bimetallic material with a smooth gradient interface structure. The procedure involves the theoretical calculation of total solidification time (TST) of the first liquid metal (M1), pouring the liquid metal (M1), and allowing it to solidify; then, before complete solidification, the second liquid metal (M2) is introduced into the mould. This novel approach has been proven to produce Al-7.5Si/Al-18Si bimetal materials using liquid-liquid casting. The optimum time interval of Al-7.5Si/Al-18Si bimetal casting with modulus of cast Mc ≤ 1 was estimated based on subtracting 5-15 s or 1-5 s from TST of M1 for sand and metallic moulds, respectively. Future work will involve determining the appropriate time interval range for castings having modulus ≥ 1 using the current approach.

Ultrasound-assisted cast-on method: Obtaining high-quality metallurgical bonds between a bare steel insert and A354 aluminum alloy within a composite casting

A bare steel insert is difficult to be bonded to an aluminum alloy using a cast-on method for manufacturing bimetal composite castings. This article describes an ultrasound-assisted cast-on (UACO) approach in obtaining high quality metallurgical bonds between bare steel inserts and A354 aluminum alloy. Hot dip tests were carried out to determine the reaction times required to obtain high quality metallurgical bonds with and without high-intensity ultrasonic vibrations. Ultrasonic vibrations were then applied through the bare steel insert to assist the cast-on method for making bimetal castings. Microstructural characterization revealed that oxide and porosity defects that covered the interface of the steel/melt in a bimetal casting made by conventional cast-on methods were totally removed in castings subjected to high-intensity ultrasonic vibrations. Push-out tests confirmed that the mean shear strength in such composite castings increased with increasing intensity of ultrasonic vibrations, from about 3.1 MPa at 0 µm amplitude to about 91.6 MPa at about 80 µm amplitude of ultrasonic vibrations. The mean shear strength associated with the UACO process was about 85 % and 39 % higher than that of the Al-Fin process and Cummins process, respectively. Theoretical analyses were performed to understand experimental results. It is believed that ultrasound induced phenomena that occur at or near the steel/melt interface play an important role in forming high quality metallurgical bonds between bare steel inserts and aluminum castings. Research results suggest that the UACO process can be a cost-effective replacement for various cast-on processes for manufacturing bimetal composite castings of high internal integrity.

Novel and simple technique for interfacial shear strength of liquid-solid compound casting specimen

A novel testing technique for the interfacial shear strength of the liquid-solid compound casting specimen was designed. Two different bimetallic materials specimens were fabricated and subsequent cut for interfacial shear testing. To ensure the easy cutting and testing of bimetallic specimen, two kinds of bearing materials were cast into metallic mold contain two different ferrous solid substrates. Direct tinning process using a mixture of tin powder and flux was applied on the solid substrates before pouring the liquid metal. In current novel testing technique, a minimum cutting and machining processing on the bimetal casting specimen were applied to minimize the internal stresses resulted from multi steps of cutting and machining processes that used in other interfacial shear strength testing techniques. Other previously used shear strength testing technique for bimetal materials was used for a comparison with the current technique. The present shear test technique offers simple and convenient approach for preparing and testing the bimetallic specimens.

Interfacial microstructures and properties of hyper-eutectic Al–21Si / hypo-eutectic Al–7.5Si bimetallic material fabricated by liquid–liquid casting route

Abstract. The bimetal casting process using the liquid–liquid technique was developed to produce a high-quality hyper-eutectic Al–21Si / hypo-eutectic Al–7.5Si alloy bimetal material. Microstructure and microhardness were investigated as a function of the time interval between pouring hypo-eutectic and hyper-eutectic alloys. A bimetal material was successfully fabricated using a liquid–liquid casting technique with a 10 s time interval in a permanent mould casting. A unique structure comprised of hyper-eutectic Al–21Si, hypo-eutectic Al–7.5Si and a eutectic interface of 70 µm thickness was obtained. This structure totally differs from that obtained using a higher time interval above 10 s that showed an imperfect interface bond due to the shrinkage cavity and formation of oxides. The hardness variation from the upper zone of 117.5 HV to the lower zone of 76 HV corresponded to the variation in Si and the content of other alloying elements. The proposed total solidification time control method is a promising approach for the successful fabrication of liquid–liquid bimetal material.

Atomic diffusion behavior and diffusion mechanism in Fe–Cu bimetal casting process studied by molecular dynamics simulation and experiment

A molecular dynamics (MD) method with an embedded atomic method (EAM) was proposed to study the atomic diffusion behavior and diffusion mechanism in the Fe–Cu bimetal casting process. The results indicated that the diffusion coefficient of the Cu atoms was larger than that of the Fe atoms at the same temperature, but the Fe atoms predominantly diffused into the Cu side in the process of diffusion bonding. Moreover, the relationship between diffusion distance and temperature was predicted by the established model, and the optimal temperature for interface diffusion bonding of Fe–Cu bimetal ranged from 1473K to 1753 K. The diffusion behavior was mainly due to vacancies, which played a key role in the formation of the Cu cluster, and the accumulation of Cu atoms decreased the system energy. Finally, FeAcknowledgmentsCu bimetal casting was prepared to validate the simulated results of the diffusion behavior and diffusion distance, and the simulated results were consistent with the experimental ones.

Mechanical and microstructure characteristics of heat-treated of high-Cr WI and AISI4140 steel bimetal beams

Heat treatments are considered as one of the most important methods used to make significant changes in the microstructure of the metallic materials and their alloys, which makes it possible to change the external behavior and properties of these materials. The effect of heat treatment at 900°C on the microstructure, hardness and flexural behavior of bimetal beams has been studied in the present work. The bimetal beams composed of a high-Cr WCI as a wear-resistant part and an AISI4140 steel as a ductile part were fabricated. The two parts of bimetal castings are joined together by means of dovetail joint and/or connector pins. The present experimental and numerical results revealed that all bimetal beams exhibited flexural strength, toughness and maximum deflection higher than those of high-Cr WI specimen and lower than those of AISI4140 specimen in heat treated conditions. Heat treatment of the bimetal casting beams produced significant improvements in both hardness and flexural strength of high-Cr WI and AISI4140 steel. This is due to the formation of secondary carbides in the martensitic matrix surrounded by a network of M7C3 carbides in high-Cr WI, and formation of fine pearlite with proeutectoid α at grain boundaries for AISI4140 steel as revealed by SEM and an optical metallography. Bimetal beam with 12-connector pins (BI12CONN) as a mechanical joint exhibited the highest flexural strength and toughness compared with the other bimetal beams after heat treatment.

Casting methods for the production of rotationally symmetric copper bimetals

ABSTRACT Multiple-material products are characterised by a complex property profile which is achieved by combining the particular advantages of at least two different materials. Bimetal casting is an energy- and material-efficient technology for the production of multi-metallic objects. This paper describes the development of a semi-continuous casting process for the formation of a rotationally symmetric bimetal with a cohesive bonding character at the interface of a copper–tin alloy (CuSn6) and pure copper (Cu99.5). Initial experiments are conducted by static casting to evaluate the thermal process window. Based on the results of the initial experiments, a vertical semi-continuous compound casting process is developed. A stable cohesive bond between the joining partners is accomplished by forming a solid solution at the interface. This paper is part of a Thematic Issue on Copper and its Alloys.

The pre-hot dipping effects on the bimetal casting of nitriding steel sleeve into the Al-Si matrix

Steel-aluminum composite material combine the excellent mechanical properties of steel such as high strength and good wear resistance with the advantages of lightweight aluminum for widely using in automobile engine block, gearbox and other car body structures. In this paper, a new process is used to cast the alloy steel sleeve into Al-Si alloy matrix for preparing aluminum engine block with steel cylinder liner. The process consists of three parts: the surface pre-treatment of steel, the hot-dipping melt and solid-liquid casting of steel with aluminum. Generally, the hot dipping melt should have lower melting point than the melting point of aluminum alloy, good temperature oxidation resistance and amount of solid solubility both with steel and aluminum. Giving consideration of such condition and cost, Zn´ Al and its alloys are used in present paper for learning the effect of hot dip coating melts on the interface properties of steel/aluminum at different times. After hot dipping, a coating formed on the surface of the steel bushing, which improves its wettability in the aluminum melt and the metallurgical bonding effect of the steel-aluminum interface. The microstructure, phase composition, growth kinetics and hardness distribution of the interface were analyzed by metallographic microscopy, scanning electron microscopy with EDS. The results show that the metallurgical bonding interface of steel/aluminum bimetal casting can be obtained by hot dipping. Hard-brittle diffusion layer produced by dipping pure Al is thicker than that produced by ZL101. Dipping pure zinc produces a dense intermetallic layer of 3-5 um and a large amount of dispersed phase of Al3FeZnx, and the bonding performance of such interface is better than the other two. The interface hardness of steel-aluminum bimetal casting obtained by hot dipping pure Al melt, ZL101 melt and pure Zn melt can reach 563.5HV, 528.3HV and 632.3HV, respectively.

Effect of liquid-solid volume ratios on the interfacial microstructure and mechanical properties of high chromium cast iron and low carbon steel bimetal

Bimetal casting made of high chromium cast iron (HCCI) and low carbon steel (LCS) was produced by liquid–solid casting technology. The influence of different liquid-solid volume ratios on microstructure and microhardness of the interface was studied. The interface microstructure and the elemental distribution from one side to the other side of the bimetal were analyzed using Energy Dispersive x-ray Spectroscopy (EDX). Wear behavior of the successfully produced bimetal was also investigated in order to emphasize the difference in the mechanical properties between the two bonded alloys. The results showed that a good metallurgical bonding area free of holes could be obtained with increasing the liquid to solid volume ratio to 10:1 and 12:1. By increasing this ratio, diffusion of the elements was accelerated resulting in expanded carbide-free zone and improved bonding of the bimetal. Accordingly, the microhardness decreased at the HCCI side and increased at the LCS part due to the elemental diffusion from the former to the later through the interface. Sliding wear test on both sides of the bimetal showed that the coefficient of friction was ∼0.79 for HCCI and 0.69 in case of LCS. The transition from the high wear resistant HCCI part to LCS was significantly observed on the worn surface of the interfacial area of the test sample. The wear mechanism involved in the two sides was delimitation and the size of the produced laminates was smaller in case of LCS than in HCCI.

New trends and advances in bi-metal casting technologies

New trends and advances in bi-metal casting technologies

Interface Structure and Elements Diffusion of As-Cast and Annealed Ductile Iron/Stainless Steel Bimetal Castings

Bimetal casting is considered to a promising technique for the production of high performance function materials. Heat treatment process for bimetal castings became an essential tool for improving interface structure and metallurgical diffusion bond. Molten iron alloy with carbon equivalent of 4.40 is poured into sand mold cavities containing solid 304 stainless steel strips insert. Specimens are heated to 7200C in an electrical heating furnace and holded at 720 0C for 60min and 180min. For as-cast specimens, a good coherent interface structure of ductile cast iron/304 stainless bimetal with four layers interfacial microstructure are obtained. Low temperature annealing at 720oC has a significat effect on the interface layers structure, where, three layers of interface structure are obtained after 180min annealing time because of the complete dissolving of thin layer of ferrite and multi carbides (Layer 2). Low temperature annealing shows a significant effect on the diffusion of C and otherwise shows slightly effect on the diffusion of Cr and Ni. Plearlite phase of Layer 3 is trsformed to spheroidal shape instead of lamallar shape in as-cast bimetals by low tempeature annealing at 720oC. The percent of the performed spheroidal cementit increases by increasing anneaaling time. Hardness of interface layers is changed by low temperauture annealing due to the significant carbon deffussion.

Study on diagonal hammer of three kind metals composite casting with block protecting handle

Hammer crusher is widely used in cement, ceramic, mining and electricityother industries, hammer head is one of important parts in crusher, its abrasion performance directly affects the service life of hammer crusher and economic cost. According to bimetalcomposite hammer head is often appear “Hammer handle wear and tear”,“Composite difficult” and the set of casting alloy block hammer head set piece of “come off” phenomenon, which design a set piece type bimetal composite casting straight diagonal hammer, make full use of high chromium cast iron wear resistance and the toughness of low alloy steel. Design a protect block structure reasonably that solve the hammer when the actual production of composite interface is difficult to control and “the problem of hammer head wear” for use. Solve the problem of hammer head wear actively, achieve “energy saving, emission reduction and environmental protection”.

Fabrication of plain carbon steel/high chromium white cast iron bimetal by a liquid–solid composite casting process

High-chromium white cast iron (HCWCI) is one of the most widely used engineering materials in the mining and cement industries. However, in some components, such as the pulverizer plates of ash mills, the poor machinability of HCWCI creates difficulties. The bimetal casting technique is a suitable method for improving the machinability of HCWCI by joining an easily machined layer of plain carbon steel (PCS) to its hard part. In this study, the possibility of PCS/HCWCI bimetal casting was investigated using sand casting. The investigation was conducted by optical and electron microscopy and non-destructive, impact toughness, and tensile tests. The hardness and chemical composition profiles on both sides of the interface were plotted in this study. The results indicated that a conventional and low-cost casting technique could be a reliable method for producing PCS/HCWCI bimetal. The interfacial microstructure comprised two distinct layers: a very fine, partially spheroidized pearlite layer and a coarse full pearlite layer. Moreover, characterization of the microstructure revealed that the interface was free of defects.

Analysis of heat transport and thickness of bimetal composition layer between low-alloy steel and high-chromium white cast iron

Two-liquid bimetal casting technique was worthy of being widely used in wear-resistant materials. Research on the fusion mechanism at the bimetal composite layer can lay the theoretic foundation for the extension of the dissimilar ferroalloy composition material. Two-liquid bimetal between the low-alloy steel and high-chromium white cast was prepared by controlling the pouring temperature, and the composite layer microstructure and composition distribution were studied. In accordance with the detected results, two-liquid bimetal casting technique can be assured, and the various casting technique parameters have an obvious effect on the composite layer microstructure. To maintain the casting technique stability, the freezing time and element diffusion of the low-alloy steel were evaluated and analysed.

Simulation of the bimetal cast in the case of milling rolls

In the paper it is proposed, in main, to obtain of a model of numerical simulation, valid general and applicable the whole peculiars cases of bimetal casting, model with which help can be studied through the computer, the optimization possibility of flowing working condition of liquid alloy of the distribution of temperatures field, of the liquid phase and contraction during the solidification, with the minimum price (necessary reimbursement of the software and calculus equipment) in very short time etc.

Carbon diffusion mechanism of two-liquid bimetal bond interface on dissimilar carbon steel

Two-liquid bimetal composite casting technology was tremendously restricted by the indeterminate interface composite mechanism. Research on the carbon diffusion mechanism at the bimetal bond interface is to lay the theoretic foundation for the alloying element action on the dissimilar ferroalloy. So, the bimetal was prepared by controlling the pouring temperature, and then the bimetal bond interface microstructure and carbon diffusion action based on the low carbon steel and high carbon steel were studied. The results have shown that the bimetal bond interface was fully metallurgic combined by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The various pouring temperatures have obvious effects on the carbon distribution and microhardness, and overheated temperature will make the interface rush mixture and cause the bond interface confusion. The carbon diffusion analysis provided an extension of the theoretical basis of two-liquid bimetal bond interface.

Failure analysis and flexural behavior of high chromium white cast iron and AISI4140 Steel bimetal beams

Failure analysis and flexural behavior of high-Cr white cast iron (HCWCI) and AISI4140 Steel bimetal beams in the as-cast condition under 3PB test were experimentally and numerically investigated. The bimetal beams of HCWCI as a wear resistant part and AISI4140 Steel as a ductile part were fabricated using a new method. In this method, the two parts of bimetal castings are joined mechanically together by dovetail joint and/or connector pins. The experimental results showed that the flexural strengths of the bimetal beams were excellent and ranged from 650 to 790MPa. The bimetal beam with sufficient connector pins exhibited the highest flexural strength compared with the other bimetal casting specimens. The numerical results of the bimetal beams are in agreement with the experimental results. The failure of the bimetal beams occurred in three stages. In the first stage, a sliding crack (mode II) initiated at the interface between the wear resistant and ductile parts at the mid-span of specimens. In the second stage, mode I crack initiated in the wear resistant part at the mid span and propagated toward the point of loading. In the last stage, a third main crack initiated and propagated in the ductile part.

Microstructure and Formation Mechanism of Two-Liquid Bimetal Composite Interface

Two-liquid bimetal composite casting technology by double induction furnace fusion was utilized for preparing bimetal product in tradition. Single induction furnace fusion has been investigated between the high carbon steel and the low carbon steel, and varying casting thickness has an obvious effect on the bimetal bonding layer. The results have shown that the bimetal bonding layer can not been generated under over thinness or thickness. In the condition of the thicker low carbon steel, two kinds of metal liquid were easy to rush mixture without the distinct interface, whereas the thinner low carbon steel can also effectively form metallurgical bonding. While the low carbon steel owned the proper thickness, metallurgical bonding can been observed distinctly, confirming the feasibility of the single induction fusion for preparing the bimetal.

Research and Application of Dual Liquid Bimetal Composite Casting Hammer

According to the hammer crusher working condition, a kind of dual liquid bimetal composite casting hammer was developed. Its service life is three times than that of high manganese steel. It improves the wear resistance and increases production efficiency significantly, and is welcomed by user deeply.

Orthogonal tests of lead-clad tin bimetal continuous casting by air pressure core-filling

To provide theoretical basis and practical guidance for preparing composite rods of external diameter no larger than 12 mm by directly continuous casting, low melting point materials of lead and tin were selected to prepare composite rods of external diameter 12 mm and inner diameter 8 mm with air pressing core filled continuous casting process. The orthogonal tests consisting of three factors and three levels were designed to investigate the parameters of melting lead temperature, continuous casting speed and air pressure that affect the performance of the composite rods. The results show that melting lead temperature is the most important factor that influences the solid/liquid interface location; continuous casting speed is the most important factor that influences the surface quality and lead and tin inter-diffusion amount; air pressure can improve the surface quality obviously and make the rods easily drawn out, but the surface quality cannot get obvious improvement when the air pressure is above 0.03 MPa. The composite rods have excellent surface quality, obvious intermediate layer, even thick clad, and metallurgical bonding interface under the condition of melting lead temperature of 375 °C, continuous casting speed of 10 mm/min, and air pressure of 0.03 MPa.