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Metal Casting Technologies : March 2006
MAJOR ASSET DISPOSAL ALLOY WHEEL MANUFACTURING PLANT • 3 Melting Furnaces • 14 Double Cavity Low Pressure Casting Machines • 2 Single Cavity Low Pressure Casting Machines • 2 Large Twin Stoke LP Casting Machines • 3 Paint Lines • Heat Treatment Furnace Facility • Crossmember Machining Unit • Chip Remelt System • 10 Machining Cells • Xray Machines • Leak Testing System Major Assets Offered for Sale Under Instruction from OFFERS ACCEPTED ON THE ENTIRE PLANT OR MAJOR ASSETS ION AUTOMOTIVE (NEW ZEALAND) LIMITED Successful offers will be subject to a 10% (GST Exclusive) buyers premium calculated on the purchase price. The highest or any offer may not necessarily be accepted. Offers accepted up until Friday, 21st April, 2006 PAYMENT: 25% Deposit Required on Purchases. All Purchases must be paid for by Cash, Bank Cheque, Credit Card or Direct Deposit Unless Prior Arrangements are made with the Auctioneers. This sale is GST Exclusive LOCATION: Manukau City, Auckland, New Zealand For inspection or further information contact the Project Managers: Denis Matthews, Ph +61 3 8552 4444, or +61 407 742 913, or email firstname.lastname@example.org Mark Pollard, ph: +61 407 549 646 More information visit our website: www.graysonline.com.au Sale #2163 M89121 ADDENDUM UNDERSTANDING THE S-CURVE The S-curve (a.k.a. IT Diagram or Isothermal Transformation Diagram, and TTT, Triple T or Time-Temperature-Transformation Diagram) is shown in Figure 7 below. The diagram represents the beginning and the end of transformation in a given steel's microstructure at certain given temperatures. Alloys and their amounts have distinct effects on the points where transformation begins and ends. Also, alloys have the effect of moving these points to the right of the observer of the diagram. Note that the abscissa, or the time scale, is in log scale, meaning that the time increases logarithmically -- every millimeter is ten times in magnitude as the previous one -- as the point moves per millimeter to the right. The ordinate represents the temperature scale in equal units. The resulting microstructure depends at what temperature the steel under treatment meets the "end of transformation" line -- it could be pearlitic, bainitic (upper or lower bainite), or martensitic. From the above, it is apparent that there is one distinct S-curve for each composition of steel. The heat treater needs these S- curves in order to guide him in the process, especially in steel alloys unfamiliar to him. United States Steel has compiled and published two books of S-curves for many standard and popular steel compositions, and every heat treater should have a set of these to eliminate the guesswork in doing his job. The S-curves could really facilitate better heat treatment of steels; even make possible the "hitting" of the desired hardness to within plus-or-minus one point on the Rockwell Hardness scale! Fig. 7. The S-Curve REFERENCES: (1) United States Steel. USS Carilloy Steels -- Alloy Steels for Special Jobs of Industry. Pittsburgh, PA (2) D. K. Bullens. Steel and Its Heat Treatment, 5th ed. John Wiley and Sons, Inc. New York. (3) M. A. Grossman, Principles of Heat Treatment, American Society for Metals, Cleveland, OH Graphically, martempering is shown in Figure 6. The method is generally limited to small sections due to the slower cooling rate of the salt in which they are cooled past the "nose" of the S-curve. Agitation of the medium can increase the quenching rate of the molten salt, so that many alloy steels can be quenched to 100 percent martensite in larger sections than in an unagitated salt bath. ● METAL Casting Technologies March 2006 49