Silver tin Oxide (AgSnO2) based contacts since their introduction are looked upon as potential replacement for AgCdO. The AgSnO2 contacts have seen continued improvisation, with respect to their applicability and performance, by enhancement in their fine microstructure.

AgSnO2 based contacts are increasingly dominating the market for medium and high current contact relays because of their low arc erosion. Besides the base oxide SnO2 embedded in the Ag matrix, these materials may or may- not contain additives like Bi2O3, CuO, In2O3, WO3 and MoO3 in a combination of varying amounts not exceeding 2%. The AgSnO2 based contacts are manufactured by powder metallurgy (powder blending, compaction and sintering) followed by extrusion/ drawing/ rolling to the final dimensions.

Modison offers a range of AgSnO2 products in various forms (profiles, wires, strips, etc.) manufactured by powder metallurgy. The profiles or strips can be provided with 10% - 20% fine silver layer for easy brazing. The material quality meets the prevailing standard international norms.

Are available

as per ISI specification or to Customer specification in the form of Wires, Strips and Foils in an excellent finish, homogeneous quality and free form detrimental defects to use for diversified engineering applications.

Name the Application, we have a ready Argent to give you strong ductile joints at Low working temperatures with rapid joint penetration almost for any combination of metals.

Available in packs of 5, 1 & 0.5 kgs.

Each pack is labelled to indicate Kind, Shape & Size, Nett weight and Manufacturing Batch No. & date An identification colour band is also affixed on each package.

Modison Metals Limited has developed high performance dispersion strengthened copper in order to provide high mechanical strength along with Copper’s high electrical conductivity.

Copper has been widely used in many industrial applications such as: contact supports, frictional break parts, electrode materials among others. Pure copper though having excellent electrical and thermal properties, has relatively low mechanical properties, like low hardness, low tensile and creep strength. Hence there is an increased demand for copper alloy having high electric conductivity and mechanical strength.

The development of Cu-based alloys having high tensile strength and hardness along with the electrical and thermal properties have picked up pace in the recent years. Such alloys find their applications in a coil material for generating high magnetic fields, spot welding electrodes, high performance switches etc. In a recent development such Cu alloys are also proposed to be used in the thermonuclear reactors. Due to their incompatibility it is difficult to obtain a copper alloy having both a high electrical conductivity and a high mechanical strength. Many conventional ingot metallurgy manufacturing methods of alloying, solution hardening and precipitation hardening have been attempted, but these have not yielded the required fruits. Moreover alloying results in the considerable loss in the electrical conductivity. Hence a need to identify a technique where one can increase copper strength without disturbing its electrical and thermal conductivities. In this respect Metal matrix composites are considered as important engineering materials with potential applications in a variety of fields.

Some metals may be strengthened by incorporating in them relatively small quantities of another material such that the added materials do not form a homogeneous solid solution phase, but are uniformly dispersed in fine particulate form throughout the metal. These small quantity material forms the dispersoid and the metal the parent matrix. Many ceramic oxides are utilized as the dispersoid due to their insolubility in the metal matrix, stability at high temperature and better mechanical properties. Such metal matrix composites combine both metallic properties and ceramic properties. Strengthening copper by means of a dispersed phase, in contrast with the conventional methods of solid solution hardening or precipitation hardening, renders a significant increase in strength while retaining a substantially pure metal matrix with very little or virtually no alloying element remaining in solid solution.

This has the advantage of giving markedly higher strength without significant loss in electrical or thermal conductivity or in corrosion resistance.

Micrograph of Alumina strengthened Copper Alumina is well dispersed in copper

Oxide dispersion strengthened copper has been identified as an effective method to increase copper strength without affecting its electrical and thermal properties. The advantages of such an alloy are:

• Resistance to softening at elevated temperatures and the electrical and thermal properties are retained,
• Reinforced matrix composites possess an increased wear resistance and better refractory properties than the non-reinforced ones. The dispersions are generally stable refractory metal oxides and amongst these metal oxides, alumina as dispersion has found more applicability because of its obvious mechanical properties (high toughness and hardness with low bulk density).
• Cost Competitive

Due to the presence of alumina, copper alloy with alumina cannot be produced by the conventional melting and casting process. Hence alumina reinforced copper alloy is manufactured by the powder metallurgy. The alumina is found to be uniformly dispersed in the copper matrix eventually giving better mechanical properties to the composite while retaining the physical properties.

In Modison the powder metallurgy technique is utilized to manufacture alumina strengthened copper. Fine individual powders of pure copper and alumina are blended in a mixer and then compacted, sintered and machined. The Modison alumina strengthened copper has competitive mechanical and physical properties with uniformly dispersed alumina in the copper matrix.

MODISON, the trusted name for electrical contacts since last three decades, also offers button contacts, most suitable for thermostats, thermal protectors, relays, sensors, circuit breakers, switches, motor protectors etc.

Modison Button Contact has facing of silver with base made up of steel or cupro-nickel. The contacts are specially processed to make the silver facing hard and wear resistant. The steel or cupro-nickel base makes it easier for welding of these contacts on different types of contact carrier.

The button contacts are provided with welding projection for easier welding which enables welding even on a thin base support.

Modison button contacts are available in various sizes, as per the requirement. Most common sizes are 4 mm and 4.75 mm diameter.

It’s cost effective – Silver is used only at the contact area with a minimum thickness.

2. It’s smaller in size, without compromising the electrical rating.

3. It’s minimizes the number of components in the assembly.

4. It’s long lasting due to greater electrical capacity.

Modison, an ISO 9001-2000 certified company, maintains highest level of quality checks and systematic approach at every stage to ensure conformance to specifications. Our customers are therefore assured of complete satisfaction while dealing with us.

A – dia., B – height of the head, C – dia.of the projection, E – height of the projection, G – thickness of the silver layer – spherical radius.

MML CLADCON ® Bimetal Contact Compares with solid contact except in price

CLADCON ®, a layer of silver alloy forms the contact surface. The rest of the head and the shank are made of copper.

PERFORMANCE

• Contact surface layer and backing metal are bonded metallurgically. This ensures the electrical and mechanical properties of CLADCON ® are as good as solid contacts.
• Electrolytic Copper provides better thermal and electrical conductivity than silver alloy and copper shank in CLADCON ® ensures longer life.
• With increasing silver prices, lower silver content of CLADCON ® allows choice of larger contact than with solid silver contact to get better performance.

Contact layer is normally half the thickness of the head. To suit specific requirements, variation on this ratio is possible within practical limits.

• Contact layer can be made of silver alloys like AgCu 3% , AgCu 8%, AgNi 10%, AgCd 10%, AgCdO 15%. Variations of this alloys can also be offered.

• Contacts can be silver plated if required.

MODISON offers a complete range of Silver Cadmium Oxide Contacts in diverse forms manufactured by Internal Oxidation as well as Powder Metallurgy to meet customer’s specific requirement. These contact materials have high resistance to contact welding and arc erosion with low contact resistance.

MODURIT ZH : Produced by Internal Oxidation of sliver and cadmium alloy from one side. Under high temperature & pressure, oxygen diffuses and oxidizes the cadmium. CdO particles precipitate in silver matrix. CdO particles at the surface are very fine and the particle size increases gradually and is coarse towards the end. This material has excellent homogeneity without any depletion zone. CdO free backing AgCd layer (10 to 30% of the thickness) is available which has 100% bond with AgCdO top layer by use of special Internal Oxidation process.

MODISON started production of this material under Licence from DODUCO GmbH, Germany with whom we had technical collaboration from 1983 till 1996.

Small additions of graphite to silver are found to reduce Considerably the welding properties of silver. Silver-graphite Composites exhibit excellent resistance to abrasion and have good self lubrication for sliding contacts application and antiweld properties.

Silver-graphite provides optimized performance in current limiting MCB, MCCB, ACB & ELCB devices. The direction of graphite fibers are perpendicular to the contact surface. The backing surface of the contact is specially prepared by decarburisation (burn – off), as the presence of graphite in the surface makes welding / brazing impossible.

Modison also supply silver graphite with graphite fibre aligned parallel to the contact surface.

BI-METAL, as the name implies, is a combination of two metals – a precious contact metal bonded to a suitable backing metal. Bi-metals are designed to effect economy by way of reduction in use of precious metals like Silver. Generally, Silver or an alloy of Silver forms the contact material while Copper/ Brass aee the most commonly used Backing materials. The bond between contacts and Backing materials is mechanically and Thermally sound.

BI-METALS are available in various forms and mostly of Contact material inlaid where required, or with one or both sides completely faced with Contact material.

MML BI-METAL strips are available in widths up to 150mm and in total thickness starting from 0.2mm onwards. Normally, Contact material thickness is 25% 30% or 50% of the total strip thickness. However Contact materials thickness ranging from 3% to 50% of the total strip thickness can be provided.

Bimetal can also be available in the form of either edgelay or throughlay. It is also possible to have an arrangement of several strips of different width. Edgelay and Throughlay Contact Bimetals are suitable for manufacture of contacts for micro switches, MCB’s etc.

Material in strips having thickness of 1.2mm and below is normally supplied in coils, while material in higher strip thickness is always supplied flat.

Apart form Bi-Metal strips, finished BI-METAL CONTACTS can also be press formed and supplied against specific orders.

Silver Tungsten

The silver and tungsten composite group combines the high thermal and electrical conductivity of silver with the high erosion resistance of the high melting tungsten. These materials are also characterized by their high strength and their resistance to welding or sticking. They are principally made by infiltration and the nominal silver content varies from 20-50%. By increasing the amount of tungsten, the hardness and welding is reduced. This composite group of alloys is specially preferred for use in air.

On account of their excellent properties, silver tungsten materials have found a wide field of applications.

They are used successfully with high tungsten content as burn-off contacts for large low-voltage circuit breakers and with lower contents as contacts carrying a steady line current for moulded case circuit breakers and in various protective circuit breakers. These contacts are also used in high current contactors where resistance to contact welding and arc erosion are required.

The silver and tungsten carbide composites exhibit initial resistance to formation of surface films and possess good antiweld and arc erosion resistance. These are specially used for devices requiring more consistent millivolt drop as compare to silver tungsten.

Modison manufacture these composites by powder metallurgy. Pressed parts are sintered and infiltered by silver in liquid phase.