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Important Information About Alloys

Alloys and Their Correct Cooling Methods

There are four typical methods of cooling, and the type of alloy being
annealed will dictate the method (see table):

1. Water quench from red heat. This method can be used for alloys that are age hardened and will result in maximum ductility, however may result in some distortion to the work piece.
2. Natural air cool. This method may be used for alloys that do not age harden or require a slow cooling rate if susceptible to quench cracking.
3. Air cool to “black heat” and then water quench. Black heat is a description used for when the work piece no longer glows red (840°F - 930°F). This method is usually employed for alloys that, if quenched above this temperature, will result in cracking due to the generation of internal stresses. Once the metal has cooled to the above temperature, water quenching will then result in optimum properties for further cold working operations to take place.
4. Cool by any of the above methods. These alloys will be unaffected by the cooling method, however, the best advice is to avoid quenching from red heat to minimize distortion effects.

Please note that the above recommendations are for optimum results. It is possible to anneal most alloys by heat-treating to a variety of temperatures, times and cool by several different methods and still achieve acceptable results.

White Alloys and the White Gold Index

Hoover & Strong customers will no doubt want to know where our white alloys sit on the MJSA white gold index. This index works by measuring the yellowness of a color, and so the lower the number, the less yellow it is. The assumption is then that if it's less yellow, it's "whiter". The value assigned is known as a "YI" value, so here are the MJSA specified levels: 

• Grade 1: "Good white" alloys. These are described as alloys that will not require rhodium plating. They must measure less than 19 on the YI index.
• Grade 2: "Reasonable white" alloys. These are described as alloys where
  rhodium plating is an option. They must measure between 19 and 24.5 on the YI index.
• Grade 3: "Poor white" alloys. These are described as having "incomplete
  bleaching" and require rhodium plating. They must measure between 24.5 and 32 on the YI index.

A non-white alloy is described as one that measures above 32 on the YI index. The chart below shows how H7S alloys measure on the YI Index. As you can see from the table, the majority of our white alloys make the "premium" or Grade 1 standard and do not require rhodium plating.

Of the three that are Grade 2 white alloys, 14KW is very close to being a Grade 1 with a value of 19, which is the borderline value between the premium and next grade. The other two are well above the limit of Grade 3.

TruPd™ has the same value as 950 platinum-ruthenium. It is extremely difficult to tell the difference between these two alloys with the naked eye.

 

See Links Below For Related Information

Argentium® Sterling Silver

Seeing Red: The Hoover & Strong Red Gold Range

Reticulated Metals - Textures For Your Designs