EDRO #3^™ is a vacuum-degassed, ladle refined, Cr-Ni-Mo- alloyed steel which is supplied in the hardened and tempered condition, offering the following benefits:

• No hardening risks
• No hardening costs
• Time saving, (e.g. no waiting for heat treatment)
• Lower tool cost (e.g. no distortion to rectify, only one polishing sequence)
• Modifications easily carried out
• Can be subsequently nitrided to increase surface wear resistance or locally flame-hardened to reduce surface damage.

EDRO #3^™ is manufactured to consistently high quality standards with a very low sulfur content, giving a steel with the following characteristics:

• Excellent polishing and photo-etching properties
• Good machinability
• High purity and good homogeneity
• Uniform hardness in all dimensions

Drilling

Chip removal is recommended when depth of hole is > 4 x D. Flush cooling should be used.

Injection molds for thermo-plastics

Extrusion dies for thermo-plastics

Blow molds

Forming tools, press-brake dies

(possibly flamehardened or nitrided)

Structural components, shafts

Physical data

After hard-chromium-plating, the tool should be tempered for approx. 4 hours at 350°F (180°C) in order to avoid hydrogen embrittlement.

EDRO #3™ is intended for use in the hardened and tempered condition, i.e. the delivery condition.

When the steel is to be heat treated to a higher hardness or case hardened, the following instructions may be helpful.

Soft annealing

Protect the steel and heat through to 1300°F (700°C) Then cool in the furnace at 50°F (10°C) per hour to 1110°F (600°C), then freely in air.

Stress-relieving

After rough machining the tool should be heated through to 1020°F (550°C), holding time 2 hours. Cool slowly to 930°F (500°C), then freely in air.

Hardening

The steel should be fully soft annealed before hardening.

Pre-heating temperature: 930-1110°F (850°C).

Austenitizing temperature: 1560°F (850°C).

The steel should be heated through to the austenitizing temperature and held at temperature for 30 minutes.

Protection against decarburization

Protect the tool against decarburization and oxidation during the hardening process.

Quenching media

• Oil
• Martempering bath 570°F (300°C), max. 4 minutes, then air.

Note: Temper immediately after tool reaches 120-160°F(50-70°C).

Tempering

Surface hardening

EDRO #3™ can be flame or induction hardened to a hardness of approx. 50 HRC. Cooling in air is preferable. Smaller pieces may require forced cooling. Hardening should be immediately followed by tempering.

Case hardening

Before case hardening is carried out, the steel should be soft annealed.

Carburizing

Temperature 1560-1720°F (850-940°C). Time and temperature are to be adjusted depending on the depth of case required. A mild carburizer should be used.

Normalizing

If the carburizing temperature has been above 1610°F (880°C) and the carburizing time more than 2 hours, normalizing should be performed in order to regain the fine-grained structure.

Hardening

Hardening is performed as previously described. The following surface hardness are normally obtained after tempering.

Note: If the carburizing temperature has been less than 1610°F (880°C) or in cases where a fine grained structure with good mechanical properties is not of paramount importance, direct hardening may be carried out. After carburizing, the tool is furnace-cooled to 1490°F (830°C), and when the tool has reached this temperature, quench in oil, then temper.

Nitriding

Nitriding gives a hard surface which is very resistant to wear and erosion. A nitrided surface also increases the corrosion resistance. The surface hardness after nitriding at a temperature of 980°F (525°C) in ammonia gas will be approx. 650HV.

Tufftriding

Tufftriding at 1025°F (570°C) will give a surface hardness of approx. 700 HV. After 2 hours' treatment, the hard layer will be approx. 0.0004 in (0.1 mm).

(EDM, "spark machining")

If spark-erosion is performed in the hardened and tempered condition, the tool should then be given an additional temper at 930°F (500°C).

Correct grinding technique will avoid grinding cracks and improove tool life. Toolls that have been tempered at low temperatures are especially sensitive during grinding. Only properly dressed, soft, open-grained grinding wheels should be used. Restrict the peripheral speed and use plenty of coolant. More detailed instructions can be obtained from the grinding wheel manufacturer.

EDRO #3™ has excellent polishability in the hardened and tempered condition. After grinding, polishing is undertaken with aluminum oxide or diamond paste. Typical procedure:

Grind to .002 in. (0.05 mm) from finished size.

Polish with diamond paste grade 45, to obtain a dull, even surface.

Polish with diamond paste grade 15.

Polish with diamod paste grade 3, or grade 1 for particularly high demands on surface finish.

Note: each steel grade has an iptimim polishing time which largely depends on hardness and polishing technique. Over-polishing can lead to poor surface finish (e.g., an "orange peel" effect).

EDRO #3™ is particularly suitable for texturing by the photo-etching process. Its very low sulphur content ensures extremely accurate and consistent pattern reproduction.

Welding of tool steel should generally be avoided, due to the risk of cracking. Where repair welding is necessary, however, it is essential to pre-heat the part concerned prior to welding. Immediately after the welding operation:

Stress-relieve material that has been welded in the soft annealed state.

Temper material twice that has been welded in the hardened and tempered condition.