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D-M-E #7

The New. D-M-E #7. A Unique Stainless Holder Steel from D-M-E. U.S. Patent # 6,045,633. During the last 25 years, modified 420F stainless steels have become a standard for mold bases worldwide.

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D-M-E #7

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  1. The New D-M-E #7 A Unique Stainless Holder Steel from D-M-E. U.S. Patent # 6,045,633

  2. During the last 25 years, modified 420F stainless steels have become a standard for mold bases worldwide. • However, 420F grades possess certain characteristics that are not ideal for mold base applications.

  3. These characteristics are: • brittleness • inconsistent hardness • crack sensitivity • inhomogeneous microstructure • unsafe weldability

  4. In 1992, an intensive research and development program was started. The goal was to: Develop a Superior Stainless Mold Base Steel

  5. Experimental stainless steel chemistries, were produced as laboratory melts and evaluated metallurgically, and from a machining standpoint. Several analyses were produced in 8,000 lb. pilot ingots.

  6. These pilot heats were further modified and extensively tested. • The final product, a new and improved • D-M-E #7, was successfully introduced in 1996.

  7. D-M-E #7 is a pre - hardened free machining 400 series martensitic stainless steel, designed and developed specifically for improved plastics mold base tooling. • D-M-E #7 is patented under U.S.patent # 6,045,633

  8. Features of D-M-E #7: • Improved Machinability • Improved Stability • Improved Ductility • Elimination of Brittle Failures • Consistent Hardness • Superior Weldability • Improved Plate Surfaceand Appearance

  9. IMPROVED MACHINABILITY • Enhanced surface finishes and threads when milling, drilling and tapping compared with 420F. • Increased tool life with faster machining feeds and speeds. • Elimination of breakout problems when drilling with carbide indexable drills.

  10. IMPROVED STABILITY • D-M-E #7 plates provide improved dimensional stability after machining and during molding. • Special thermal treatments during manufacture provide improved uniformity and reduced residual stresses. 420F plates have a tendency to distort • D-M-E #7 plates remain flat and parallel after extensive machining.

  11. IMPROVED DUCTILITY • D-M-E #7 shows improved ductility, a measure of a steel’s ability to be deformed prior to fracture. • Bend samples were tested to illustrate the improved ductility of D-M-E #7 compared to 420F steels.

  12. BEND TEST RESULTS 420F 35HRC D-M-E #7 35HRC Samples of 420F cracked and broke into two pieces after bending 30 degrees. D-M-E #7 samples cracked after bending 70 degrees, but did not break.

  13. MECHANICAL PROPERTIES D-M-E #7 displays superior ductility and notch toughness compared to 420F at the same strength and hardness levels. Results of room temperature tensile and Charpy V-notch impact tests using samples from rolled and heat treated 3” gauge plates.

  14. ELIMINATION OF BRITTLE FAILURES • D-M-E #7’s increased toughness reduces the risk of plates cracking during the life of the mold, and also reduces the risk of breakage caused by machining pressures and stresses.

  15. HARDNESS • D-M-E #7 exhibits a more uniform and consistent hardness than 420F. • D-M-E #7 is supplied heat treated to a standard hardness of 32-36 HRC (BHN 301-340). • (Maximum hardness attainable: 40 HRC)

  16. SUPERIOR WELDABILITY • D-M-E #7 is safe and easy to weld. • D-M-E #7 filler metal produces virtually invisible welds, with consistent properties throughout the welded area. • The following two slides illustrate the differences between the microstructures and properties of welded 420F and welded D-M-E #7.

  17. 420F WELD SAMPLE Weld Heat Affected Zone Base Metal 20HRC 54HRC 50HRC 48HRC 35HRC 35HRC 40X Photomicrograph showing undesirable high hardness in heat affected zone near test weld on 420F sample. A 300 series non - hardenable stainless filler metal is typically used when repair welding 420F to minimize risk of cracking.

  18. D-M-E #7 WELD SAMPLE Weld Heat Affected Zone Base Metal 35HRC 35HRC 35HRC 35HRC 40X Photomicrograph showing uniform desirable hardness throughout weld, heat affected zone and base metal of DME #7 sample, using DME #7 filler metal.

  19. IMPROVED PLATE SURFACE AND APPEARANCE • D-M-E #7 possesses increased hot ductility resulting in smoother as rolled plate surfaces, free of tears and cracks. Better as rolled surfaces reduce the risk of surface cracks remaining after machining. • Flat smooth surfaces also mean less stock removal to produce finished sizes, requiring less machining and lower material costs.

  20. QUALITY CONTROL • D-M-E #7 is manufactured in accordance with detailed specifications covering melting, rolling and heat treating. • All production operations are controlled and supervised, providing uniformity and quality in every plate produced. • Standard metallurgical and production testing is also performed on all D-M-E #7 plates produced, ensuring a consistent product with unmatched quality.

  21. The New D-M-E #7 For improved stainless mold bases. U.S. Patent # 6,045,633

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