Machinery's Handbook, 31st Edition
346 Spring Design Beryllium-copper shrinks and deforms when heated. Such springs usually are baked in fixtures or supported on arbors or rods during heating. Brass and phosphor bronze springs should be given a light heat only. Baking above 450°F will soften the material. Do not heat in salt pots. Torsion springs do not require baking because coiling causes residual stresses in a direction that is helpful, but such springs frequently are baked so that jarring or handling will not cause them to lose the position of their ends. Table 20. Moduli of Elasticity in Torsion and Tension of Spring Materials Ferrous Materials Nonferrous Materials Material (Commercial Name) Modulus of Elasticity a , psi Material (Commercial Name) Modulus of Elasticity a , psi In Torsion, G In Tension, E In Torsion, G In Tension, E Hard Drawn MB Spring Brass Up to 0.032 inch 11,700,000 28,800,000 Type 70-30 5,000,000 15,000,000 0.033 to 0.063 inch 11,600,000 28,700,000 Phosphor Bronze 0.064 to 0.125 inch 11,500,000 28,600,000 5 percent tin 6,000,000 15,000,000 0.126 to 0.625 inch 11,400,000 28,500,000 Beryllium-Copper Music Wire Cold Drawn 4 Nos. 7,000,000 17,000,000 Up to 0.032 inch 12,000,000 29,500,000 Pretempered, fully hard 7,250,000 19,000,000 0.033 to 0.063 inch 11,850,000 29,000,000 Inconel b 600 10,500,000 31,000,000 c 0.064 to 0.125 inch 11,750,000 28,500,000 Inconel b X 750 10,500,000 31,000,000 c 0.126 to 0.250 inch 11,600,000 28,000,000 Monel b 400 9,500,000 26,000,000 Oil-Tempered MB 11,200,000 28,500,000 Monel b K 500 9,500,000 26,000,000 Chrome-Vanadium 11,200,000 28,500,000 Duranickel b 300 11,000,000 30,000,000 Chrome-Silicon 11,200,000 29,500,000 Permanickel b 11,000,000 30,000,000 Silicon-Manganese 10,750,000 29,000,000 Ni Span b C 902 10,000,000 27,500,000 Stainless Steel Elgiloy d 12,000,000 29,500,000 Types 302, 304, 316 10,000,000 28,000,000 c Iso-Elastic e 9,200,000 26,000,000 Type 17-7 PH 10,500,000 29,500,000 Type 420 11,000,000 29,000,000 Type 431 11,400,000 29,500,000 a Note: Modulus G (shear modulus) is used for compression and extension springs; modulus E (Young’s modulus) is used for torsion, flat, and spiral springs. b Trade name of International Nickel Company. c May be 2,000,000 pounds per square inch less if material is not fully hard. d Trade name of Hamilton Watch Company. e Trade name of John Chatillon & Sons. Spring brass and phosphor bronze springs that are not very highly stressed and are not subject to severe operating use may be stress relieved after coiling by immersing them in boiling water for a period of 1 hour. Positions of loops will change with heat. Parallel hooks may change as much as 45 de- grees during baking. Torsion spring arms will alter position considerably. These changes should be allowed for during looping or forming. Quick heating after coiling either in a high-temperature salt pot or by passing a spring through a gas flame is not good practice. Samples heated in this way will not conform with production runs that are properly baked. A small, controlled-temperature oven should be used for samples and for small lot orders. Plated springs should always be baked before plating to relieve coiling stresses and again after plating to relieve hydrogen embrittlement. Hardness values fall with high heat—but music wire, hard drawn, and stainless steel will increase 2 to 4 points on the Rockwell C scale.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online