DME 7 A Unique Stainless Holder Steel from

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 420 F stainless steels have become a standard for mold bases worldwide. • However, 420 F grades possess certain characteristics that are not ideal for mold base applications.

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

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

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.

• 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.

• 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

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

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

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. D-M-E #7 plates remain flat and parallel after extensive machining.

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 420 F steels.

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

MECHANICAL PROPERTIES D-M-E #7 displays superior ductility and notch toughness compared to 420 F 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.

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.

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

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 420 F and welded D-M-E #7.

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

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

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.

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.

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