Copyright 2008 CRS Holdings, Inc. The Impact of New Aerospace Materials, Manufacturing Strategies and Production Schedules on Machining Techniques and Control SAE Webcast June 4, 2008 Carpenter Technology Corporation participated in a webinar delivered by SAE International’s Aerospace Engineering & Manufacturing magazine. Carpenter’s manager of the Forged Bar and Billet Business Group presented a comparison of three major iron- and nickel-base alloy systems used in aerospace applications: stainless steels, high strength-high toughness alloys, and high temperature alloys.  Tips were offered to help improve machining productivity of the non-stainless materials. Copyright 2008 CRS Holdings, Inc.

Carpenter Produces Vacuum Melted and/or Remelted Aerospace Alloys in Three Categories High strength/high toughness steels – found in turbine shafts and structural components Martensitic precipitation hardenable stainless steels - structural components and turbine compressor assemblies Nickel-base superalloys - engine compressor and turbine sections The information and data presented herein are typical or average values and are not a guarantee of 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/her own evaluation and are not intended as warranties, either express or implied, of fitness for these or other purposes.

Examples of Two Aerospace High Strength/High Toughness Steels AerMet® 100 Alloy Annealed Hardness RC38 Aged Hardness RC54 Toughness 110 ksi√in Maraging 250 Annealed Hardness RC32 Aged Hardness RC52 Toughness 75 ksi√in Increased hardness and toughness demand rigid machining setups and advanced tooling. Registered trademarks are property of CRS Holdings, Inc., a subsidiary of Carpenter Technology Corporation.

Examples of Aerospace Stainless Steels Relative strength and toughness of PH stainless steels

Examples of Nickel-Base Superalloys 720 718 31V Ni-30 TEMPERATURE TENSILE YIELD STRENGTH Wasp/901/ Thermo-Span X-750 80A/A-286 41 909 706 751 Ni-30/ 909/706 Wasp/901 751/X-750 80A A-286 Waspaloy 901 31V/751 901/31V 75°F (24°C) 1500°F (815°C) 1200°F (650°C) 1300°F (705°C) 1400°F (760°C) 1600°F (870°C) Age-Hardenable Superalloy Selectaloy Diagram (Yield Strength)

Characteristics of Machinability Productivity Tool life Chip size/removal Surface roughness Cycle time Consistency

Material Characteristics Affecting Machinability Metallurgical properties responsible for machinability characteristics: High tensile strengths Large spreads between yield and tensile strengths High ductility and toughness High work hardening rates Low thermal conductivity

Difficulties Associated With Modern Aerospace Materials Operating conditions in engines and aerospace structures demand higher strength, higher toughness and higher operating temperatures to improve aircraft efficiency. The higher alloy content required to achieve these properties and the properties themselves lead to lower machining productivity, shorter tool life and more difficult chip formation and removal.

Effect of Thermal Conductivity

Effect of Thermal Conductivity 15Cr-5Ni PH Speed 400 SFM Feed 0.005 IPR Project 70+® 15Cr-5Ni Speed 400 SFM Feed 0.005 IPR Temperature(F) Temperature(F) Although the coolant removes a fair amount of the heat generated at the tool material interface, a lot of the heat also is transmitted into the chip or through the work piece. Thermal conductivity plays a significant role in determining how much heat is moved away from the tool material interface. As the tool moves through the material, a thin work hardened layer is developed. The feed rate needs to be at least as great as the work hardened layer to preserve the tool. With sharp tooling, the work hardened layer can be ~0.001” or less. Free machining additives act as lubricating agents thereby reducing the forces required for machining which ultimately means less heat at the tool material interface. In this example, using an enhanced machining version of 15-5 (I.e. P70+) leads to an overall reduction of cutting forces by 15%.

Free Machining Additives in Stainless Steels Effect and Limitations of Sulfur Additions Free Machining Additives in Stainless Steels Sulfur additions improve machinability. Free machining additives show up as inclusions in the material. Act not only as chip breakers but also as lubricating agents. Type 303 - 200X Magnification

Tool Design Optimization Impact of Tool Design Angle - 4 degrees 8 degrees Tool Design Optimization 12 degrees 14 degrees Tooling design is also important in that it will determine the size and shape of the chips generated. Long stringy chips can cause problems in that 1. they can inhibit coolant flow 2. they can get caught up during subsequent machining operations causing defects in the parts 3. they increase chip management headaches Project 70+® Type 303 chips vs. back rake angle 0.062” wide cut-off 180 SFPM, 0.001 IPR

Data on Speeds, Feeds and Tool Materials Visit Carpenter’s Technical Information Database at www.cartech.com

Modern Iron and Nickel Base Aerospace Alloys and Their Impact on Machinability Summary: Materials are typically selected for their properties rather than their machinability. Sulfurized alloys machine more economically but are limited to specific grades such as 17-4 and 15-5 stainless. Wise tooling selection and setup, including tool angle and speed, are the keys to maximizing productivity. Refer to the searchable technical information database at www.cartech.com for suggested speeds and feeds on more than 100 stainless steels and specialty alloys.

Thank you for your interest in machinability of alloys in the aerospace industry. More information is available on this site, including product literature, alloy datasheets, and technical articles. To contact Carpenter, call 1-800-654-6543 in the U.S. or refer to the Contact Us page for the location nearest you.