Silver Brazed Stainless Steel Cable Presented by: Erik Clark Tim Flynn Tony Foster Peter Jones Brian Martel Ried Snyder

What is it?  Lets start with what a Cable is

 In this case it is a 1 x 19 cable that is made out of little wires put together  To be exact it is 1 strand of one set of 19 little wires

 In this application it is important to use cable instead of a solid piece because cables are flexible and have give  Cable is cost effective  Cable is easy to form for this application

 What is Stainless Steel?  Why would we want to use Stainless Steel?

 What is Stainless Steel?  Steel, Stainless High Alloy Steel (usually containing Cr, or Cr + Ni) designed for resistance to corrosion and/or oxidation  Chromium content in stainless varies from 13% - 27%  Many, but not all stainless alloys contain 8% - 10% Nickel  Here are some of the other metals used in stainless alloys; Mn, Si, N, P, S, and or course, C

Example of properties Steel (18 CR - 8 Ni Stainless) Modulus of elasticity E = 205,000MPa or 30x10 6 psi

 Why would we want to use Stainless Steel?  Stainless Steel is needed to help avoid the problems created by corrosion

 Corrosion Control  The goal of using stainless steel is to control corrosion  There are different ways to do this ─Protective coatings or ─Avoidance of galvanic couples

 Protective coatings  This method works well for many applications ─ Cars, Houses, and other painted things ─ Galvanized Steel  Problems ─ Protective coatings can wear off leaving surface at risk ─ Coated materials must be treated with care

 One way to avoid galvanic couples is by limiting designs to a single type of metal. ─ Brass bolt – steel washer pitfall  This does not always solve the problem though ─A cathode and anode may develop in a single material

 Alloying steel with certain other materials makes it resistant to the cathode anode relationship that creates corrosion  Stainless steel keeps the strength of regular steel without having the corrosion problem

Joining Stainless Steel Components Many Different Methods: –Welding –Brazing –Soldering –Adhesive Bonding –Mechanical Fastening

Brazing Outline Why Brazing? Applications Involving Brazing Brazing Processes Filler Materials

The Method of Brazing Brazing employs filler metals having a liquidus above 450°C (840°F) and below the solidus of the metal. In comparison: –Solders employ a filler metal which DOES melt below 450°C (840°F). –Welding applications end up melting a substantial amount of the base metal. –Adhesive bonding is becoming very competitive with other joining methods

Brazing Applications Brazing is often used to join stainless steels to dissimilar metals, such as carbon steels, low-alloy steels, and copper alloys. Brazing can obtain strong, corrosion- resistant, leak-tight joints in small or thin walled components with minimal buckling and warpage. Brazing can produce joints in delicate assemblies and in very thin-gage metals.

Brazeability of Stainless Steel No more difficult than carbon and low-alloy steels. However, chromium oxide films which form during the brazing process must be adequately removed. –Their refractory and strongly adherent nature will prevent the molten metal from wetting the base metal.

Removing Chromium Oxides Many different techniques exist for removing chromium oxide: –Chemical room temperature –Heating to the brazing temperature in a hydrogen atmosphere –Coating the area with a chemically active flux which dissolves the oxide –Heating in a vacuum –Etc.

Brazing Processes Many different methods for brazing exist as well, including: –Furnace –Torch –Induction –Resistance –Salt-bathing

Furnace Brazing Popular because of its comparatively low equipment cost Used extensively where the parts to be brazed can be assembled with the brazing material pre placed near or on the joint. Heating is usually produced by electrical resistance.

Torch Brazing Commonly used for repairs, one-of-a-kind brazing jobs, and short production runs. The technique is relatively simple and is similar to other torch welding applications. Slightly reducing flames are commonly used to prevent oxidation. Rather easily automated.

Brazing Filler Materials Silver (Ag) Nickel (Ni) Copper (Cu) Gold (Au) Which one used is based on mechanical properties, corrosion resistance, service temperature, compatibility with the base material, and cost.

Silver Brazing BAg – 3 is the most commonly used filler Commonly applied with torch brazing, as opposed to furnace brazing. Unable to be used for high-temperature applications -- below 370°C (700°F) Many factors will vary heat temperature ranges used and time allowances.

Other Brazing Fillers Nickel is the second most common and allows for high corrosion resistance and high-temperature strength. Copper has poor resistive properties and special protective atmospheres must be used during brazing. Gold is high cost but can lead to some of the most corrosive resistant joinings.

Why Silver Brazing Then? Brazing is more applicable than welding since a minimum of the base material of the part will be lost. Silver is cheaper and most widely used than other fillers, and special corrosion resistive properties are not needed. Torch welding is easily applied and prevents the need for an automated furnace system.

Resources ASM Handbook Volume 6 ASM Specialty Handbook (Stainless Steels) Questions?