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  • Silvery-white high-strength copper alloy

    WNS7

    C76800

    Main applications

    Automobile / Household key material／Western Tableware／Construction materials

    • plate
    • strip
    • bar
    • wire
    • ball

    WNS7 has gained popularity from users as well as achieved high market share especially in keys of cars and houses, thank to its white color tone and excellent characteristics.

    Main features

    1. A beautiful color tone of glossy silver white. It represents the softness characteristic of copper alloys compared with stainless steel.
    2. Excellent mechanical properties, high strength and high ductility, and high fatigue strength.
    3. Excellent resistance to corrosion and discoloration.
    4. Good resistance to stress corrosion cracking
    5. Good machinability
    6. Good hot workability
    7. Good wear resistance
    Key for automotive and house

    Chemical composition

    The chemical composition of WNS7 is as follows.

    Nominal Composition (Weight %)
    Cu Ni Mn Zn
    49 9 6 Rem.
    * Including inevitable impurities and trace additive elements
    Technical Data

    Physical properties

    The physical properties of WNS7 are as follows.

    Comparison with Nickel Silver
    Property  
    Property WNS7 C7941
    Free-cutting nickel silver    		 C6782
    High strength brass    		 C3771
    Forging brass
    Specific Gravity (293K) 8.3 8.8 8.3 8.45
    Coefficient of Thermal Expansion
    (×10-6/K：293～573K)    		 17 17 19 21
    Electrical Conductivity
    (%IACS:293K)    		 4.4 5.5 25 27
    Modulus of Elasticity
    (kN/mm²: 293K)    		 114 125 98 98

    Mechanical Properties

    It shows the mechanical properties of WNS7.
    WNS7 has strength comparable to nickel silver for spring.

    Mechanical properties of WNS7 (representative value)
    Temper Tensile Strength
    （N/mm²）    		 Elongation
    （％）    		 Yield strength
    （N/mm²）    		 Hardness
    (HV)    		 Fatigue Strength
    N=107
    N/mm²
    O 470 63 220 103 190
    1/4H 510 47 340 140 220
    1/2H 570 33 440 165 230
    H 630 20 540 190 240
    EH 740 9 650 215 250

    Corrosion resisitance

    WNS7 shows corrosion resistance equivalent to that of two types of nickel silver.

    Comparison of corrosion weight losses of WNS7 and two types of the nickel silver when being immersed in various solutions

    Immersion at 25 °C for 10 days (unit mg /dm2/day）
    Item HCl※ H2SO4※ Artificial sweat※ Soy sauce Vinegar Detergent Gasoline
    WNS7 230 79 71 8 152 7 0.5
    C7521 570 78 86 9 300 3 0.5

    * Hydrochloric acid is HCl (1 + 19), sulfuric acid is H2SO4(1 + 19), artificial sweat is 19.9 g of NaCl + 1.7 g of urea + 1.7 g of lactic acid + 0.8 g of Na2S + 0.2 g/l of NH4Cl.
    Use commercially available soy sauce and the like.

    Stress relaxation resistance

    Generally, it is said that it has small stress corrosion cracking susceptibility, is superior to C2200(Brass) in stress corrosion cracking resistance with proven performance, and is slightly inferior to C7521 (two types of the nickel silver).

    Stress corrosion crack test result

    Wear resistance

    A load of 50 kgf was applied to the test piece by using the Amsler type wear test as shown in the figure below, and then wear tests for rolling and sliding were conducted. The results are shown in the figure below. WNS7 exhibits better wear resistance than that of C6782, C7941, and C3771, and does not adversely affect the wear amount of SUS 304 which is the mating material.

    Abrasion test result
    test procedure
    result

Leaflet download

ALLOY GUIDE（Plate/Strip）PDF