SIHARD S471 Steel



Designation by Standards

Brand Name Ravne Mat. No. DIN EN AISI/SAE
SIHARD S471 OCR8W - - - -

Chemical Composition (in weight %)

C Si Mn Cr Mo V W Others
1.10 1.0 0.35 7.90 1.50 2.20 1.20 -

Description
The OCR8W cold-work tool steel produced by SIJ Metal Ravne is a medium-chromium, air-hardening tool steel providing a very good combination of wear resistance and toughness. It is available primarily in round bars for cold-work tooling applications. The OCR8W steel excels itself through the following properties:
A very good combination of wear resistance and toughness, high hardness, nitridability and high dimensional stability.

Applications
Typical applications for OCR8W cold-work tool steel:
Blanking dies, thread roll dies, punches, coining dies, drawing dies, upsetting dies, cutting tools, cutting rolls and cutting knives.

Comparison to 1.2379 (D2)
The OCR8W is a premium tool steel with high wear resistance and toughness. Compared to the conventional 1.2379 (AISI D2) steel, the OCR8W steel has a higher wear resistance, better hardenability and it is capable of achieving higher hardness and toughness. Toughness is important to prevent cracking and chipping resulting in a catastrophic failure of tools. Toughness is better than in the conventional 1.2379 (AISI D2) type of cold-work tool steel.





Comparison of microstructure

Microstructure of OCR8W steel. Scale bar: 200 µm.

Microstructure of 1.2379 steel. Scale bar: 200 µm.

Continuous Cooling Transformation (CCT) Diagram


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Coefficient of Linear Thermal Expansion 10-6 m/(mK)

100oC 200oC 300oC 400oC 500oC 600oC 700oC
10.8 11.0 11.5 11.7 12.1 12.0 12.0


Soft Annealing
All material is delivered in spheroidized annealed condition with max. 240 HB hardness. When used after reforging, spheroidized annealing has to precede hardening. Annealing must be performed after hot working and before rehardening. Heat at a rate not exceeding 50 C per hour to reach 820-860 C, and hold at that temperature for 1 hour per 25 mm thickness; 2 hours minimum. Then cool down slowly in the furnace to 600 C at a rate not exceeding 20 C per hour. Continue cooling to ambient temperature in the furnace or in air. The final hardness should be maximum 240 HB.

Hardening

Preheating
To minimize distortion and stresses in large or complex tools use double preheat. Heat at a rate not exceeding 50 C per hour to 620-680 C for equalization, and then continue heating to reach 820-840 C. For normal tools, use only the second temperature range as a single preheating treatment.

Austenitizing
Heat rapidly from the preheat.
Furnace or salt bath: 1040-1080 C. Equalize and soak at austenitizing temperature for 30 minutes for pieces up to 25 mm in thickness, plus 15 minutes for each additional 25 mm of thickness. For maximum toughness, austenitize from the lower recommended range of austenitization temperatures. For maximum wear resistance, austenitize from the upper recommended range of austenitization temperatures.

Quenching
1040 to 1080 C / air, oil or inert gas. To increase hardness by 1 to 2 HRC and dimensional stability after quenching, a sub-zero treatment may be used.

Tempering
Temper immediately after quenching (when material after quenching reaches 90-70 C). At least two tempering treatments are recommended to achieve a uniform tempered microstructure. Slowly heat to reach tempering temperature. Holding time in the furnace: 1 hour for every 25 mm of workpiece thickness, but 2 hours minimum. This is followed by cooling in air. Typical tempering temperatures are 150 to 550 C.

Tempering Diagram


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Surface treatments

To reduce friction and to increase wear resistance, surface treatment can be used. The recommended treatments are nitriding and surface coating with wear-resistant layers, for example via PVD.

Nitriding
Nitriding results in a hard surface layer which is highly resistant to wear and galling. The surface hardness after nitriding is approx. 1300 HV0.2.

PVD
Physical vapour deposition (PVD) is a method that applies wear-resistant coating at temperatures between 200 C and 500 C. PVD is a coating process for producing high-quality surface finishes. The coating produces an extremely hard surface, which is characterised by its resistance. It is particularly wear resistant. PVD TiN/(Ti,Al)N, CrN and TiN coatings have become important for several industrial applications at elevated temperature. It has been documented in the literature that TiN, CrN and TiN(Ti, Al)N PVD coatings can reduce friction in tribological contacts and increase the abrasive wear resistance.

Forging
Hot forming temperature: 1050-850 oC.

Machinability
50-60% of a 1% carbon steel.

Forms manufactured: Please see the Dimensional Sales Program.

Disclaimer
The information and data presented herein are typical or average values and are not a guarantee of the maximum or minimum values. Applications specifically suggested for material described herein are made solely for the purpose of illustration to enable the reader to make his own evaluation and are not intended as warranties, either express or implied, of fitness for these or other purposes. There is no representation that the recipient of this literature will receive updated editions as they become available.

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