Silver Graphite

Materials

Type	Fine	Medium	Large
Graphite content in %	3 – 4 – 5	3 – 4	3
Grain size	1 to 5 μm	5 – 40 μm	20 – 160 μm
Metalor' designation	F	M	G

N.B. : in certain cases, a TGG (extra coarse) grain size might be needed, available on demand

Manufacturing processes

Technique	EXTRUSION		DIE COMPACTING
C – Grain alignment*	PERPENDICULAR	PARALLEL	RANDOM
Metalor's designation	ET	ED	U
Contact surface	10 to 200 mm²	10 to 400 mm²	no limit
Contact thickness	0.35 ≤ h	0.40 ≤ h ≤ 1.5	0.50 ≤ h ≤ 2.5
Available forms	Tip – Wire	Tip – Profile	Tip

N.B. : in certain cases, tips obtained through die compacting are pressed a second time
* In relation to the contact surface

Physical characteristics

Grain size		Fine			Medium		Large
Graphite content in %		3	4	5	3	4	3
Theorical density g/cm³		9.46	9.16	8.88	9.46	9.16	9.16
IACS conductibility Measured by eddy Current method %	ET	78	64	59	83.5	75.5	82.5
	ED	88	80.5	78	87	81	90.5
	U	67	57	49.5	82	76	81.5
HV hardness	ET	45 to 55	40 to 50	40 to 50	30 to 40	30 to 40	30 to 40
	ED	35 to 45	35 to 50	25 to 35	33 to 40	30 to 40	30 to 40
	U	30 to 40	30 to 40	25 to 35	25 to 35	25 to 35	25 to 35

Underlayer characteristics

Silver face	1 FACE	2 FACES	0 FACE
Underlayer thickness e	10 to 150 μm		0
Underlayer with solder plating	yes	yes	no

Other characteristics :

• The underlayer in the case of random structure my be fine silver, or there may be no underlayer at all.
• Solder material : any type which is adapted to the assembly
• Identification of the solderable face through marking to be defined in cooperation with the customer

Designation

Metalor's wide range of material necessitates an accurate description : structure, number of silver faces, grain size, graphite content.

• FET 1-5 : Tip with fine grain, perpendicular structure, 1 silver face, 5 % graphite
• MED1-3 : Tip with medium grain, parallel structure, 1 silver face, 3 % graphite

Electrical characteristics

Because of its properties, AgC is the ideal material for protection switchgears : high breaking capacity, low resistivity.
The properties of AgC depend upon the amount of graphite added, the manufacturing process and grain size.

Example, as a rough estimate, for a 5 000 A breaking test :

Graphite content in %		3	4	5
Erosion (mg)	FET	31	45	62
	FED	100	122	143

Applications

Switchgears

• Any protection swichgear requiring breaking capacity at 16 to 1 000 A rated current :
  • Circuit Breaker for home
  • Residual Current Circuit Breaker for home
  • Industrial Circuit Breaker for industry
  • Contactor Breaker for industry
• Any switchgear utilizing sliding contacts
• Any contactor incuring risks of micro-welding