FUTURE GRAIN DEVELOPMENTS

Research is accelerating both in existing alumina-based grain technology and in new ultra-hard materials. In the group of ceramic-processed alumina materials, Saint-Gobain released SG in 1986 [U. S. Patent 4,623,364] followed by extruded SG in 1991 [U. S. Patent 5,009,676]. More recently in 1993, Treibacher released an alumina material with hard filler additives [U. S. Patent 5,194,073]. Electrofused technology has also advanced. Pechiney produced an Al-O-N grain (Abral) produced by the cofusion of alumina and AlON followed by slow solidification. It offered much higher thermal corrosion resistance relative to regular alumina while also having constant self-sharpening characteristics akin to ceramic-processed materials but softer acting [Roquefeuil 2001].

New materials have also been announced with hardness approaching CBN and diamond. Iowa State University announced in 2000 an Al-Mg-B material with a hardness value comparable to CBN [U. S. Patent 6,099.605]. Dow Chemical patented in 2000 an Al-C-N material with a hardness value close to diamond [U. S. Patent 6,042,627]. In 1992, the University of California patented some — C3N4 and — C3N4 materials that may actually be harder than diamond [U. S. Patent 5,110,679]. Whether any of these materials eventually proves to have useful abrasive properties and can be produced in commercial quantities has yet to be seen. Nevertheless, there will undoubtedly be considerable advances in abrasive materials in the coming years.

5.8 postscript

In the short time since this chapter was first prepared the superabrasives market has seen dramatic change. GE Superabrasives is no longer owned by GE and has been renamed Diamond Innovations. De Beers has moved much of its European manufacturing to South Africa and renamed its Industrial

TABLE 5.3

Particle Size Comparisons

Japanese

FEPA

ISO R 5665—1990

ANSI

US Grit

(JIS)

Particles

Designation

Aperture Range (|rm)

Grit Size

Number

Size

Per Carat

Standard

1181

1,180/1,000

16/18

1001

1,000/850

18/20

851

850/710

20/25

711

710/600

25/30

601

600/500

30/35

501

500/425

35/40

35

426

425/355

40/45

356

355/300

45/50

301

300/250

50/60

50

50

2,000

251

250/212

60/70

60

213

212/180

70/80

80

181

180/150

80/100

100

80

10,000

151

150/125

100/120

120

100

17,000

126

125/106

120/140

150

120

21,000

107

106/90

140/170

180

140

49,000

91

90/75

170/200

220

170

88,000

76

75/63

200/230

240

200

140,000

64

63/53

230/270

280

230

250,000

54

53/45

270/325

320

270

280,000

46

45/38

325/400

400

325

660,000

Wide range

1182

1,180/850

16/20

33

892

850/600

20/30

20

602

600/425

30/40

30

282

502

500/355

35/45

427

425/300

40/50

40

770

252

250/180

60/80

60

3,000

Division, Element 6. Chinese manufacturers, as of 2005, have increased their superabrasive grain capacity to over 4 billion carats/annum creating a market excess and further driving down prices. It is expected that in the coming years this will accelerate the conversion of large production wheels from alox to CBN grain for high production applications such as through-feed centerless and plunge grinding. It will also ensure the continuance of the ongoing battle between the competing technol­ogies of hard turning and grinding.

Updated: 24.03.2016 — 12:02