WNS7 (Silvery-white high strength copper alloy)｜Copper & Copper Alloy Business Unit, MITSUBISHI MATERIALS

Standard No.

CDA: C76800

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

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

Main applications

Automobile / Household key material
Western Tableware
Construction materials

Chemical composition

The chemical components of WNS7 are as follows.

nominal components
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
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 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 （N/mm²）	Elongation （％）	Yield strength （N/mm²）	Hardness^*	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

* 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*	H₂SO_4*	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

result

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Copper & Copper Alloy Business

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