CPT International 02/2019

More documents

Recommendations

Info

COATINGS Multitasking: Coatings for centrifugal casting As the range of centrifugal casting applications increases, so does the importance of coatings. In the past, coatings were mainly used as a separating layer between the mold and the casting part, whereas today they are designed to meet very specific requirements: Innovative coatings formulated for centrifugal casting help to avoid casting defects, influence mechanical parameters and even serve as a forming medium to allow the creation of special surface structures. Klaus Seeger, Ekaterina Potaturina, Düsseldorf The centrifugal casting process Centrifugal casting was first used in the middle of the 19th century by the British engineer and inventor Sir Henry Bessemer to produce rotationally symmetrical parts. In centrifugal casting, the melt is poured into a metal mold which rotates around its central axis at high speed. The centrifugal forces acting on it press the melt against the mold wall and produce a very pure and highly densified composite. The metal solidifies as the mold rotates – with the advantage that a cavity-free casting in the form of a cylindrical (hollow) body is produced without the use of feeders. The inner geometry of the mold determines the outer contour of the casting, 62
act the casting and extends the life of the mold. Avoiding casting defects Casting defects such as inclusions, gas or reaction defects, which cannot be completely eliminated simply by changing the process parameters, are a significant problem in the centrifugal casting process. As the metallic permanent mold is impermeable to gas during centrifugal casting, the mold coating plays an important “gas management” role. In order to avoid gas defects such as pinholes, the coating must have a certain porosity and be able to absorb the decomposition gases produced. By targeted optimisation of the composition and structure of the coating, casting defects can be effectively avoided. If, for example, organic components are replaced with inorganic ones, or calcined raw materials are used, the loss on ignition and thus the risk of gas defects is reduced. Selecting raw materials with low reactivity also helps reduce the risk of reaction errors (Figure 3). In centrifugal casting castings can be manufactured without voids, where you can dispense with the use of feeders. Photo: ?? Figure 1: The mold is coated using a spray lance. coatings for centrifugal casting make it possible to achieve clearly defined properties and advantages. The various functions that a centrifugal casting coating can perform are described below and illustrated using practical application examples (Figure 2). Coatings as separating agents The coating can be applied by sprinkling a dry powder into the rotating mold. An alternative frequently used process involves applying the coating by spraying a coating dispersion into the mold.. The coating’s primary task is to achieve a separating effect between mold and melt. Powder coatings can, for example, consist of a mixture of ferrosilicon, graphite, quartz dust, bentonite or diatomaceous earth . The addition of water and a dispersion agent makes it possible to paint or spray the coating. The uniform coating of the mold wall makes it easier to ext- Insulating effect The insulating effect of the coating is an important factor in the composition formation and the hardness profile. It regulates the heat transfer from the molten metal to the mold, thus contributing to the control of solidification and the casting structure. The insulating properties depend on the one hand on the composition of the coating, and on the other hand, on the layer thickness on the mold. Both para- the quantity of metal supplied determines the wall thickness. In horizontal casting, the melt is poured into a lying mold. In the case of particularly long castings or during continuous centrifugal casting, the runner can be moved during the casting process (Figure 1). In vertical casting, the casting takes place in a mold with a vertically rotating axis. Vertical casting can be used to produce conical or spherical outer contours. The rotational speed is often significantly slower than with horizontal casting. In centrifugal casting, the mold is usually lined with a ceramic protective layer, the so-called coating. Since the development of the centrifugal casting process, the demands placed on the casting parts and, at the same time, the functions to be met by the coating have continuously increased. Today, modern Figure 2: Several molds can be arranged in a casting carousel to produce large numbers of castings. CASTING PLANT & TECHNOLOGY 2/<strong>2019</strong> 63
Page 3 and 4:
EDITORIAL It’s Showtime! The quad
Page 5 and 6:
CONTENTS CLEANING, FETT LING & FINI
Page 7 and 8:
“Innovations are crucial for succ
Page 9 and 10:
YXLON - QUALITY ASSURANCE AND PROCE
Page 11 and 12: the first cores would take place as
Page 13 and 14: After removal, a robot deburrs the
Page 15 and 16: FOUNDRY - A PASSION FROM OUR HEART.
Page 17 and 18: Photos: Klaus Vollrath carried out
Page 19 and 20: Left: Fully automatic plant for hea
Page 21 and 22: ut also the design, joining and pro
Page 23 and 24: Potential solutions in foundry plan
Page 25 and 26: foundry is busy working with eight
Page 27 and 28: the mass finishing system can debur
Page 29 and 30: State of the art Exothermic feeder
Page 31 and 32: Figure 6: GTP Schäfer feeder datab
Page 33 and 34: CASTING Special GIFA 2019 Part 2: O
Page 35 and 36: “Germany is a trade fair country
Page 37 and 38: ment - which will continue to produ
Page 39 and 40: selves about what the exhibitors ar
Page 41 and 42: HÜTTENTAG 2019 Get-Together of the
Page 43 and 44: The Bright World of Metals With the
Page 45 and 46: FOSECO Non ferrous melt shop Insura
Page 47 and 48: IMERYS Kersand and Durandal - the r
Page 49 and 50: dehyde potential. Furthermore, the
Page 51 and 52: BÜRKERT Modular platform for heati
Page 53 and 54: Photo: Foseco Foseco’s new, paten
Page 55 and 56: IDECO Hydrogen Analysis in Aluminum
Page 57 and 58: FOSECO Filtration for iron and stee
Page 59 and 60: WHEELABRATOR A new wheel, advanced
Page 61: GIFA 2019 hall 16 / C11 Torque moto
Page 65 and 66: MASTER EVERY MELT Speed up the prod
Page 67 and 68: Figure 9: A continuous layer of coa
Page 69 and 70: The Kinetic Assembly Structure refl
Page 71 and 72: Production of a 3-D pattern and its
Page 73 and 74: Order Form - NEWSLETTER 2019 NEWSLE
show all

CPT International 02/2019

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?