Soldering, Brazing, and Welding
Kinds of Flux
Solder and flux choice:
Kester carries solid wire solders:
Flux for Stainless Steel
When working on stainless, you'll need silver solder and an appropriate flux!
Stay-Clean is a zinc chloride flux:
Kester: "Soldering to Stainless Steel"
"Stainless steel requires the use of special fluxs in order to acheive good adhesion of the solder to the stainless steel. Typical acid core fluxes will not work on stainless. Kester has 817, which is specially formulated for applications of soldering to stainless. Kester 817 must be used with solid wire or it can be used in addition to acid core solder. Kester 817 flux is typically brushed on the stainless and then the solder is reflowed using standard reflow procedures with an iron or a torch. "
More on Kester 817:
"Complete removal of residues left when soldering with 715 and 817 can be assured by rinsing with a 1% solution of hydrochloric acid. This should be followed by a rinse with a 2-10% solution of 5760 Neutralizer and a final rinse with clean water. "
- RubyFluid Stainless Steel
- LA-CO M-A Liquid Stainless Steel Flux Liquid, 4 oz
- Harris Stay-Clean® Liquid Soldering Flux
- Stay-Clean® Paste Soldering Flux
"Developed for fast fluxing action on stainless steel, M-A Flux is excellent for projects on stainless gutters and roofs, among many other applications. It contains no zinc chloride and it will not cause progressive corrosion on stainless pipe. There is no neutralizing necessary when using it to solder stainless steel."
A still-builder using M-A Flux:
Solder I Have
Kester 44, Rosin Core, 1 lb Spool, 63/37 Sn/Pb Eutectic, 183C/361F
Wikipedia: "Common in electronics; exceptional tinning and wetting properties, also good for stainless steel. One of most common solders. Low cost and good bonding properties. Used in both SMT and through-hole electronics. Rapidly dissolves gold and silver, not recommended for those. Sn60Pb40 is slightly cheaper and is often used instead for cost reasons, as the melting point difference is insignificant in practice. On slow cooling gives slightly brighter joints than Sn60Pb40."
Silver Solder Options
Kester, Solid Core, 1 lb Spool, 10/88/02 Sn/Pb/Ag, 268-299C/514-570F
Wikipedia: "Silver content reduces solubility of silver coatings in the solder. Not recommended for gold. Forms a eutectic phase, not recommended for operation above 120 °C."
Kester, Solid Core, 1 lb Spool, 62/36/02 Sn/Pb/Ag, 179C
Wikipedia: "Common in electronics. The strongest tin-lead solder. Appearance identical to Sn60Pb40 or Sn63Pb37. Crystals of Ag3Sn may be seen growing from the solder. Extended heat treatment leads to formation of crystals of binary alloys. Silver content decreases solubility of silver, making the alloy suitable for soldering silver-metallized surfaces, e.g. SMD capacitors and other silver-metallized ceramics. Not recommended for gold. General-purpose."
Wikipedia: "exceptional strength, silver gives it a bright long-lasting finish; ideal for stainless steel"
Wikipedia: "Lead Free, Cadmium Free formulation designed specifically to replace Lead solders in Copper and Stainless Steel plumbing, and in electrical and electronic applications."
Wikipedia: "Fine lamellar structure of densely distributed Ag3Sn. Annealing at 125 °C coarsens the structure and softens the solder. Creeps via dislocation climb as a result of lattice diffusion. Used as wire for hand soldering rework; compatible with SnCu0.7, SnAg3Cu0.5, SnAg3.9Cu0.6, and similar alloys. Used as solder spheres for BGA/CSP components. Used for step soldering and die attachment in high power devices. Established history in the industry. Widely used. Strong lead-free joints. Silver content minimizes solubility of silver coatings. Not recommended for gold. Marginal wetting. Good for step soldering. Used for soldering stainless steel as it wets stainless steel better than other soft solders. Silver content does not suppress dissolution of silver metallizations. High tin content allows absorbing significant amount of gold without embrittlement."
Wikipedia: "Widely used. Strong lead-free joints. Silver content minimizes solubility of silver coatings. Not recommended for gold. Produces strong and ductile joints on Copper and Stainless Steel. The resulting joints have high tolerance to vibration and stress, with tensile strengths to 30,000 psi on Stainless."
94/06 Sn/Ag, 221-279C
Wikipedia: "Produces strong and ductile joints on Copper and Stainless Steel. The resulting joints have high tolerance to vibration and stress, with tensile strengths to 30,000 psi on Stainless."
Wikipedia: "Produces strong and ductile joints on Copper and Stainless Steel. The resulting joints have high tolerance to vibration and stress, with tensile strengths to 31,000 psi on Stainless. Audio industry standard for vehicle and home theater speaker installations. Its 7% Silver content requires a higher temperature range, but yields superior strength and vibration resistance."