铸造生产现场质量保证体系

介绍铸造生产现场质量保证体系的基本知识，包括：生产现场质量保证体系的含义和构成，怎样建立“铸造生产现场质量保证体系”以及质量保证体系的管理方法。     

Hot tearing behaviour of binary Mg–1Al alloy using a contraction force measuring method

Abstract

Hot tearing (or hot cracking) is recognised in the foundry industry as a serious defect. Although it has been investigated for decades, understanding still stands at a qualitative level. In this work, investigations on hot tearing in the binary Mg–1Al (wt-%) alloy have been conducted, using a contraction stress measuring method which shows evidence of good repeatability. The results show that increasing mould temperature decreases hot tearing susceptibility for Mg–1Al due to a decreased cooling rate. The recorded contraction force curves also show that hot cracks initiate under all investigated mould temperatures; however, the crack propagation behaves differently. At lower mould temperatures, the crack propagates very fast, while at higher mould temperatures it propagates slowly. This indicates that a lower cooling rate allows a better chance for the retained liquid to refill the crack. Consequently this leads to partial or complete interruption of crack propagation.     

Hypereutectic Aluminium-Silicon Casting Alloys—A Review

Abstract

The structure, properties and uses of hypereutectic aluminium-silicon foundry alloys are reviewed. Emphasis is placed on the control of primary silicon morphology through phosphorus treatment. The effects of various process variables on the silicon structure are discussed. Experimental work related to the simultaneous refinement of primary silicon and modification of the eutectic is reviewed. It is concluded that beneficial effects can be obtained by simultaneous refinement and modification, although the primary silicon is never as finely distributed as when only phosphorus refined.     

Combustion and decomposition of VOCs from shell moulds by regenerative thermal oxidiser

Abstract

In the present work, the regenerative thermal oxidiser (RTO) with preheating and baking system was applied to treating volatile organic compounds (VOCs) discharged from the shell mould casting. As a result, it was found that the tar characterised by more than 523 K of high boiling point was formed by the shell mould casting. The Fourier transform infrared spectrometry analysis showed that the tar was composed of paraffin, zinc stearate and quartz. A part of the tar was deposited on the ceramic honeycombs in the heat exchanger. However, the tar can be almost completely removed by means of baking treatment at 623 K in the RTO. Regarding the decomposition of VOCs, it was found that the concentrations of all VOCs were reduced to less than 1 ppm. Further, 98% of offensive odour was removed by the treatment. Thus, it can be concluded that the RTO is suitable for decreasing VOCs from the shell mould casting in the foundry.     

Possibility of grain size prediction in AA5754 aluminium ingots using neural networks

Abstract

The approach to the grain size prediction in AA5754 Al alloy ingots based on artificial neural networks (ANN) has been used in the present study. The ANN has been trained on data that was measured in the real industrial conditions during the process of direct chill Al ingots casting. A very complex relation between the numerous casting parameters and the microstructure of the ingots justifies the application of neural networks, which are known for mapping complex and non-linear systems. A feed forward ANN model with the resilient back-propagation learning algorithm and weight decay regularisation has been developed to relate the grain size to casting rate, meniscus level, casting temperature, water flow for the metal mould cooling and speed of wire for master alloy addition. The results obtained from the ANN are found to be consistent with the theoretical researches and experience from the foundry.     

A Study of the Microstructure,Mechanical Properties and Weldability of Low-carbon Ductile Iron

Abstract

Low-carbon cast iron (1.7–1.8% C, 1.7–2.2% Si) test bars and castings were prepared in a production foundry for evaluation of their microstructures and mechanical properties. The experimental variables were (a) inoculant types and (b) heat treatment cycles. Results indicate that low-carbon ductile cast irons with graphite present in spheroidal/compacted form may be satisfactorily produced on an industrial scale, after appropriate inoculation. However, a short normalising cum tempering heat treatment is necessary for the development of optimum mechanical properties. Low carbon irons can be satisfactorily welded to similar grades of cast irons as well as to steel.     

Development of power assisted wire suspension system and its application to mould setting

Abstract

In this paper, a power assisted wire suspension system which supports the setting of a mould is presented. The purpose of this system is to eliminate a worker's burden and to assist the skill for unskilled workers. This system measures the swing angle of the rope and the fluctuation of the mould's weight caused by operator's force, and it moves the AC servomotors of both the horizontal and vertical axes work in accordance with the detected swing angle and the force respectively. The effectiveness of this power assisted system is confirmed by experiments for setting of the mould.     

Influence of compositional variations on microstructural evolution,mechanical properties and fluidity of secondary foundry alloy AlSi9Cu3

Abstract

The combined effect of the main alloying elements on the mechanical properties and fluidity of the secondary foundry alloy AlSi9Cu3 has been investigated. Systematic compositional variations within the alloy's tolerance limit illustrate the broad spectrum of attainable properties. The yield strength in the as cast condition can be adjusted from 100 to 200 MPa, while the elongation to fracture can be simultaneously varied between 0·35% and almost 4%. Additionally, variation in fluidity by more than 100% can be achieved. The microstructure–property relationship is interpreted in the light of thermodynamic calculations that reveal a significant mutual interaction of the alloying elements.     

Industrial treatment processes for recycling of green foundry sands

Abstract

Three treatment processes for the reclamation of green moulding sands coming out from a cast iron foundry located in Northern Italy are considered in this study. A wet mechanical treatment, a dry mechanical treatment and a dry mechanical plus heat treatment are compared to evaluate the efficiency of each process and to point out the best regeneration solution for the recycling of reclaimed sand in foundry operations. The inflow and the outflow samples of each process were characterised by means of particle size analysis and the determination of silica, loss on ignition, acid request, oolitic and some metals contents. A final evaluation of the three processes was performed taking into account the obtained quality of recovered silica sand and the economical aspects; the wet mechanical and the dry mechanical plus thermal treatments are most effective for the recovery of green moulding sands coming out from the considered foundry plant for cold box core production.     

Mechanism of Microsegregation in Iron-Carbon Alloys and New Possibilities in Foundry Technology

Abstract

In this paper, the authors attempt to establish the mechanism of dendritic segregation in iron-carbon alloys based on a study of electronic structure donor-acceptor properties and interparticle interaction. This mechanism is thought to play a very important role in the formation of the structure of such Fe-C alloys, and in the development of their properties. It is suggested that it is a misconception that a heat-treatment cycle involving heating Fe-C alloys to a temperature which promotes the existence of a single-phase system always reduces the degree of residual microsegregation and homogenises the structure. On the basis of a theoretical analysis, practical recommendations are advanced for the improvement of foundry technology so that the properties of iron and steel castings can be enhanced, with especial regard to obtaining homogeneous pearlite/ ferrite structures, higher levels of strength, and better performance characteristics—while at the same time conserving expensive ferroalloys.     

Evaluation of Corrosion Inhibitors for a Large Industrial Cooling System

Abstract

The cooling water of a large refinery chemical plant was shown to be corrosive, when measured at heat transfer surfaces, to the extent of about 40 mil per year (m.p.y.). A series of corrosion inhibitors was evaluated, again on heat transfer surfaces, using a pilot test rig operating with cooling system water containing the inhibitor.

The best results indicated that the corrosion rate could be reduced to below 3 m.p.y.

Practical experience showed that several factors in the system as a whole, prevented this figure from being achieved. Measures are being taken to eliminate or separate these factors.     

Graphite nucleation control in grey cast iron

Abstract

A research programme has been undertaken to achieve a more detailed understanding of graphite nucleation control in grey cast irons, at different sulphur (0˙02–0˙1%), residual aluminium (0˙001–0˙010%) and zirconium (0˙001–0˙015%) levels in iron melts. It was found that three groups of elements are important to sustain a three stage model for the nucleation of graphite in grey irons:

(i) strong deoxidising elements (Al, Zr) to promote early formed very small microinclusions, oxide based, which will act as nucleation sites for later formed complex (Mn,X)S compounds

(ii) Mn and S to sustain MnS type sulphide formation

(iii) inoculating elements (Ca, Sr, etc.) which act in the first stage or/and in the second one of graphite formation, to improve the capability of (Mn,X)S compounds to nucleate graphite.

It was confirmed that 0˙07%S level is beneficial for graphite nucleation in grey irons with a lower incidence of carbides and undercooled graphite, compared to 0˙023%S cast irons. Low residual Al level (0˙001–0˙003%) results in higher chill and more undercooled graphite and lower eutectic cell count, in inoculated irons. A 0˙007–0˙010%Al content in the melt is important to sustain type A graphite nucleation and reduced chill. Not only inoculation but also the preconditioning (Al or/and Zr) of the base iron has a strong beneficial effect on the solidification pattern of cast irons. Both Al and Zr sustain the type A graphite formation with a lower degree of undercooling and free carbides. These elements were associated in a complex alloy (FeSi based), very efficient in preconditioning of grey irons for thin wall castings, at a low addition rate.     

Contactless inspection of castings: analysis of alignment procedures

Abstract

In foundry industries as well as in many other sectors, inspection practice has been facing a gradual revolution through the introduction and development of optical scanners in recent years. The main advantage of contactless quality control is that the external geometry of the cast tool or cast part can be completely inspected in short times by retrieving the coordinates of hundreds of thousands of points. The role and importance of the alignment operation in part inspection is undeniable since any error leads to an unreliable inspection of the part. Therefore, the definition of part reference systems on scan data for computer aided inspection is a crucial operation. The aims of this paper are to highlight this issue and to point out how an improper procedure for part alignment can lead to an incorrect evaluation of real part deviations, especially when the accuracy of the scan data is low.     

Metal–metal bonding process using copper oxide nanoparticles

Abstract

This work performs metal–metal bonding using CuO nanoparticles prepared with salt base reaction in aqueous solution. A colloid solution of CuO nanoparticles was prepared by mixing Cu(NO₃)₂ aqueous solution and NaOH aqueous solution. Submicrometre sized leaf-like aggregates composed of CuO nanoparticles were produced at a Na/Cu ratio of 1·7 and at 20°C, though Cu₂(OH)₃NO₃ was also obtained. An aging process, which is a process composed of preparation of the particles at 20°C and then aging them at 80°C, provided transformation from Cu₂(OH)₃NO₃ to CuO with no damage of the leaf structure. The shear strength, which was required for separating discs bonded using the particles as a filler at 400°C in H₂ gas, was 32·5 MPa at the maximum for the particles prepared at the Na/Cu ratio of 1·7 with the aging process. These results indicated that the formation of leaf-like aggregates of CuO particles with high purity led to efficient metal–metal bonding.     

Electric field of cathodically protected pipeline

Abstract

The electric field caused by the cathodic protection of a buried pipeline, both on the surface and in the soil surrounding the pipeline is considered; at every point the value of the electric potential function U _(x,y,z) is computed from which the electric field intensity E caused by the cathodic protection system is established. To obtain these results, both the pipeline and the anodes are represented by spherical elements. The precision of this computational approach is validated experimentally. The results are presented as curves and lines of electric field.     

Columnar to equiaxed transition during growth of a univariant eutectic

Abstract

In this work the transition from columnar to equiaxed growth is studied during the solidification of the univariant eutectic L→ α(Al) + θ-Al₂Cu in the ternary Al–Cu–Ag system. The experimental technique used is upwards solidification with a controlled cooling rate. In the lower part of the sample where the temperature gradient is high, a cellular eutectic is observed. When the temperature gradient decreases, the morphology first changes into two-phase dendrites and finally into an equiaxed eutectic. When the amount of Ag is increased, the formation of eutectic colonies becomes easier. Also, a higher cooling rate facilitates the formation of eutectic colonies. The addition of TiB₂ does not influence the nucleation of eutectic colonies. Although the composition is on the eutectic groove, primary α(Al)-dendrites are found in the samples with TiB₂. This leads to segregation effects due to the density difference between α(Al) and the liquid.     

Designing molecular protection: new paradigm for developing corrosion resistant materials uniting high throughput studies,multiscale modelling and self-repair

Abstract

Over the past decade, three technologies, high throughput studies, multiscale modelling (MSM) and self-repair, have entered the field of corrosion science. MSM links processes from 10⁶ to 10^?7 m and allows an understanding of how metal protection systems interact with the environment and with surface electrochemical processes. Potentially MSM has the ability to accurately predict component life and so permit virtual design. In virtual design, a huge range of possible design (including molecular designs) can be assessed on a PC before selecting the best performing inhibitor for a specific application. High throughput experimentation permits many tests to be undertaken at one time. As well as allowing a huge range of inhibitors to be tested under a variety of conditions, it allows the inhibitors of the one family with subtly different molecular configurations to be tested. Self-repair is based on the principle that no matter how well we design and construct a material, it will always develop defects and thus the safest way to design is to build in agents that can cause the material to repair itself. These materials by themselves can hasten our material development and provide more reliable materials; however, if combined synergistically, they will permit radically new materials with tailored functionalities to be developed.     

Properties of silica sand and GBF slag moulds practiced by Nishiyama process

ABSTRACT

Investigations were carried out to use Granulated Blast furnace (GBF) slag as mould material for either full or partial replacement of existing silica sand in foundry industry. Nishiyama process was adopted for evaluating the same. A series of sand tests were carried out on sand and slag individually and also combinations of these two. Three types of moulds were made with sand, slag individually and combination of these two. Both laboratory and industrial castings of ferrous and non ferrous materials were performed. Results of mould permeability, compression and shear strength of GBF slag reveal that is a suitable candidate for either partial or full replacement of molding sand. During casting of both laboratory and industrial, neither fuse, dripping nor collapse of the mould walls was observed; this is true for both ferrous and non ferrous castings. Castings with good surface finish, no surface defects and porosity were made by slag moulds.     

Categorisation through evidence accumulation in an active vision system

In this paper, we present an artificial vision system that is trained with a genetic algorithm for categorising five different kinds of images (letters) of different sizes. The system, which has a limited field of view, can move its eye so as to explore the images visually. The analysis of the system at the end of the training process indicates that correct categorisation is achieved by (1) exploiting sensory-motor coordination so as to experience stimuli that facilitate discrimination, and (2) integrating perceptual and/or motor information over time through a process of accumulation of partially conflicting evidence. We discuss our results with respect to the possible different strategies for categorisation and to the possible roles that action can play in perception.     

Effect of ultrasonic melt treatment on microstructure of A356 aluminium cast alloys

Abstract

A systematic study of the effect of ultrasonic treatment on the structure of the A356 Al–Si–Mg alloy was carried out. Ultrasonic vibrations were applied to the melt at several temperatures (628 to 608°C) for different periods (0–180 s). The results showed that the ultrasonic treatment is effective in controlling the morphology and size of aluminium grains when applied between 619 to 626°C, and is very effective at 622–625°C, where fine non-dendritic grains are formed. Grain sizes smaller than 60 μm and roundness values of 0˙7 and higher were achieved by 15 s ultrasonic treatment at 623 and 620°C. At higher temperatures, the microstructures are dominantly rosette like and dendritic. At lower temperatures (below 617°C), the samples show inhomogeneous microstructures in terms of grain size and morphology. The current results are useful to set some process parameters for the ultrasonic treatment of liquid Al–Si–Mg foundry alloys prepared for semisolid processing.