Silver Brazed Stainless Steel Cable

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Silver Brazed StainlessSteel Cable

• Presented by
• Erik Clark
• Tim Flynn
• Tony Foster
• Peter Jones
• Brian Martel
• Ried Snyder

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Stainless Steel Cable?

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

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Cable

• 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

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Cable Continued

• 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

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Stainless Steel

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

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Stainless Continued

• 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

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Stainless Continued

• Example of properties
• Steel (18 CR - 8 Ni Stainless)
• Modulus of elasticity E 205,000MPa or 30x106psi

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Stainless Continued

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

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Stainless Continued

• 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

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Stainless Continued

• 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

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Stainless Continued

• 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

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Stainless Continued

• 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

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Joining Stainless Steel Components

• Many Different Methods
• Welding
• Brazing
• Soldering
• Adhesive Bonding
• Mechanical Fastening

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Brazing Outline

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

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The Method of Brazing

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

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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.

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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.

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Removing Chromium Oxides

• Many different techniques exist for removing
  chromium oxide
• Chemical cleaning _at_ 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.

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Brazing Processes

• Many different methods for brazing exist as well,
  including
• Furnace
• Torch
• Induction
• Resistance
• Salt-bathing

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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.

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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.

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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.

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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 370C (700F)
• Many factors will vary heat temperature ranges
  used and time allowances.

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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.

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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.

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Resources

• ASM Handbook Volume 6
• ASM Specialty Handbook (Stainless Steels)

• Questions?