Ceramics. For smart and productive machining of super alloys

Transcription

1 Ceramics For smart and productive machining of super alloys

2 Ceramic machining Applications Ceramic grades can be applied in a broad range of applications and materials; most often in high speed turning operations but also in grooving and milling operations. The specific properties of each ceramic grade enable high productivity, when applied correctly. Knowledge of when and how to use ceramic grades is important for success. All ceramic cutting tools have excellent heat and wear resistance at high cutting speeds. Below you can find the most common types of ceramics used in hard and/or difficult to machine materials. Super alloy materials Sialon (SiAlON) grades combine the strength of a self-reinforced silicon nitride network with enhanced chemical stability. Sialon grades are ideal for machining heat resistant super alloys (HRSA). CC6060, CC6065 Whisker-reinforced ceramics use silicon carbide whiskers (SiCw) to dramatically increase toughness and enable the use of coolant. Whisker-reinforced ceramics are ideal for machining Ni-based alloys. CC670 Other materials Mixed ceramics are particle reinforced through the addition of cubic carbides or carbonitrides (TiC, Ti(C,N)). This improves toughness and thermal conductivity. CC6050 Silicon nitride ceramics (Si3N4) represent another group of ceramic materials. Their elongated crystals form a self-reinforced material with high toughness. Silicon nitride grades are successful in grey cast iron, but a lack of chemical stability limits their use in other workpiece materials. CC6190, CC6090 Oxide ceramics are aluminium oxide based (Al2O3), with added zirconia (ZrO2) for crack inhibition. This generates a material that is chemically very stable, but which lacks thermal shock resistance. CC620 General limitations of ceramics include their thermal shock resistance and fracture toughness. Ceramic grades 2

3 Ceramic turning Application areas for HRSA grades Notch wear resistance Bulk toughness CC6060 CC6065 CC670 Programming consideration Programmed with roll-in, roll-out of corner Programmed direct into corner/plunging Material consideration Pre-machined material Forging High quality forging Skin, scale, ovality Intermediate stage machining 46 HRC First stage machining 26 HRC Cutting parameters v c The speed should be balanced to create enough heat in the cutting zone to plasticise the chip but not too high to unbalance the ceramic. The feed should be selected to give a chip thickness which is high enough to not work-harden the material but not be too high to cause edge frittering. Higher feeds and depths of cut require a reduction of the cutting speed. These boundaries will change depending upon the component material hardness and grain size Work hardening of workpiece material Short tool life too high cutting temperature CC6060 CC6065 CC670 Edge line frittering too low cutting temperature Top slice high cutting pressure h ex Cutting data for turning Start cutting data recommendations (RNGN 12, RCG 12) Inconel 718 (38 to 46 HRC) Grade Cutting speed, v c Cutting depth, a p Feed, f n CC to 300 m/min 2 mm 0.1 to 0.15 mm/r CC to 250 m/min 2 mm 0.15 to 0.2 mm/r CC to 300 m/min 2 to 3 mm 0.15 to 0.2 mm/r Stable conditions and correctly applied application methods and coolant supply are important for best results. 3

4 Ceramic milling Ceramic inserts cutter for roughing super alloys Ceramic milling typically runs at 20 to 30 times the speed of carbide, although at lower feed rates (~0.1 mm/tooth), which results in high productivity gains. Due to intermittent cutting, it is a much cooler operation than turning. For this reason, speeds of m/min when milling are adapted, compared with m/min for turning. Ceramics have a high tendency for notching, which is why round inserts are primarily used to ensure a low entering angle. Never use coolant. Ceramics have a negative effect on the surface integrity and topography, and are therefore not used when machining close to the finished component shape. The primary application for grade CC6060 (sialon) is milling Inconel 718 engine castings and oil drilling equipment, in both cases due to the high metal removal rates. Maximum flank wear when using ceramic inserts in HRSA is 1 mm. Negative inserts require up-milling Please observe that negative inserts require up-milling while positive inserts prefer down-milling Programming considerations when using turn milling technique the center line of the insert must be on the centre line of the component. Grade CC6060 best - no coolant Conventional milling - zero chip thickness on entry into component Radial immersion, ae - >70% to give smoothest exit from component Shor t to cuttin ol life to g tem peratu o high re applica tion Edge li ne low cutt frittering to ing tem o perature Top slice high cutting pressure 1200 Work hardening of workpiece material vc Cutting data for milling hex Grade Cutting speed, vc Cutting depth, ap Feed, fn to 1000 m/min 2 mm 0.07 to 0.11 mm/r

5 Cases Ceramic milling Tool: Competitor, Sandvik Coromant high-feed cutter S-R120R-051C6-124 Insert: Competitor, Sandvik Coromant carbide RNGN E Cutting speed v c (m/min): Feed per tooth f z (mm): Table feed v f (mm/min): Cutting depth a p (mm): Cutting width a e (mm): Metal removal rate Q (cm3/min): Results: A total of 42 hours of cutting time was saved per year, and the productivity increased by 469%. Sandvik Coromant s Sialon grades CC6060 and CC6065 and the whisker ceramic CC670 complement a strong ceramic insert programme both for turning and milling. Ceramic turning Tool: Competitor, Sandvik Coromant Solid holder Adaptor: C8-SL70-LF-051 Holder: SL70-CRDCL Insert: RC RCG E Coated carbide Ceramic grade CC6060 Cutting speed v c (m/min): Feed per tooth f z (mm): Cutting depth a p (mm): Metal removal rate Q (cm3/min): Tool life per insert edge (min): 10 5 Results: By using the ceramic insert grade CC6060 in combination with trochoidal turning the machining time for the pocketing operation was reduced from 63 hours down to 13 hours i.e. a saving of 50 hours machining time per component! Additional the No of insert edges used is reduced from 380 to 160 per component. 5

6 Product offer for super alloys Turning Applications External turning Coromant Capto Shank tools SL70 Damped blade for turning/ grooving Internal turning T-Max boring bars For T-Max P ceramic and CBN inserts with negative basicshape, without hole. Holders for inserts with hole For round T-Max P ceramic inserts with positive or negative basicshape and without hole. Gauge inserts CNGN DNGN SNGN TNGN RNGN CNGN DNGN SNGN TNGN RCGN RNGN CSG RCG RPGN RNGN General inserts turning/ milling ISO ANSI CNGN 12 4 DNGN 15 4 RNGN 9, 12, 15, 19, 25 3, 4, 5, 6, 8 SNGN 9, 12, 15, 19 3, 4, 5, 6 TNGN 16, 22 3, 4 RPGN 6, 9, 12 2, 3, 4 RCG 6, 9, 12 2, 3, 4 RPG 6, 9, 12 2, 3, 4 TPGN 11, 16 2, 3 Grooving ISO ANSI CSG 6, 9, 12 2, 3,

7 Milling Applications Cylindrical shank Coromant Capto Arbor RNGN 12 RPGN 06 RPGN 09 RPGN 12 Dia mm Dia mm Dia mm Dia mm Dia mm Dia mm Dia 40 mm Dia 50 mm 7

8 Sandvik Coromant Total ceramic grade offer CC6060 Sialon grade for optimized performance when turning pre-machined HRSA in stable conditions. Predictable wear due to good notch wear resistance. CC6065 Particle reinforced Sialon for turning operations in HRSA that demand tough inserts. CC670 Whisker ceramic with excellent toughness for turning, grooving and milling of Ni-based alloys. Can also be used for hard part turning in unfavourable conditions. CC650 Mixed ceramic for high speed finishing of grey cast irons and hardened materials, and for semi-finishing operations in HRSA with low toughness demands. CC6050 Mixed ceramic for light, continuous finishing in hardened materials. GC1690 Coated silicon nitride grade for light roughing to finish turning of cast iron. CC6190 CC6090 Silicon nitride grade for rough to finish turning and high speed dry milling of cast iron, perlitic nodular cast irons and hardened cast irons. CC620 Oxide ceramic for high speed finishing of grey cast iron in stable and dry conditions. Head office: AB Sandvik Coromant SE Sandviken, Sweden C-2929:61 ENG/01 AB Sandvik Coromant