MITSUBISHI MATERIALSCopper & Copper Alloy Business

MITSUBISHI MATERIALSCopper & Copper Alloy Business


Products information

WNS7Silvery-white high-strength copper alloy

Standard No.

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

Main features

  1. A beautiful color tone of glossy silver white. Represent the softness peculiar to copper alloy as compared with stainless steel.
  2. Excellent mechanical properties, high strength and high ductility, and high fatigue strength.
  3. Excellent resistance to corrosion, difficult to discolor
  4. Good resistance to stress corrosion cracking
  5. Good machinability
  6. Good hot workability
  7. Good wear resistance

Main applications

  1. Automobile / Household key material
  2. Western Tableware
  3. Construction materials
Key for automotive and house

Chemical composition

The chemical components of WNS7 are as follows.

nominal components (Weight %)
Cu Ni Mn Zn
49 9 6 Rem.
* Including inevitable impurities and trace additive elements

Physical properties

The physical properties of WNS7 are as follows.

compares with nickel silver
Property WNS7 C7941
Free-cutting nickel silver
High strength brass
Forging brass
Specific Gravity (293K) 8.3 8.8 8.3 8.45
Coefficient of Thermal Expansion
17 17 19 21
Electrical Conductivity
4.4 5.5 25 27
Modulus of Elasticity
(kN/mm2: 293K)
114 125 98 98

Mechanical properties sampling

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
Yield strength
Hardness* Fatigue Strength
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
* referance value

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 HC 1 (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 stress corrosion cracking resistance than C2200 (trunk) with proven performance, and is slightly inferior to C7521 (two types of the nickel silver).

Stress corrosion crack test result by JIS A method

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


Rolled product Sales Dept.