Depending on which copper alloy you chose, you can achieve the strength of steel, superior corrosion resistance and/or durability in applications that require wear and galling resistance. But first, let’s differentiate between brass and bronze, because in some quarters of industry, the terms are used interchangeably.
Aluminum Bronzes are a family of copper-based alloys that use iron and nickel in their chemistry - but rely on aluminum as the principle alloying element. Aluminum significantly adds to the strength to the point that it is similar to that of medium carbon steel. The additional advantage is that aluminum bronze also possesses excellent corrosion resistance. It is that strength and corrosion resistance that gave rise to the early use of aluminum bronze.
A small adjustment in metallurgy causes significant changes in performance. This recognition of other properties has led to the use of Aluminum Bronzes for a variety of parts requiring strength, hardness, resistance to wear and galling, low magnetic permeability, resistance to cavitation, erosion, softening and oxidation at elevated temperatures. These properties, together with ease of weldability, have greatly extended the fields of application for Aluminum Bronze.
Non-ferrous metals or alloys are materials that are not iron based like their ferrous counterparts. One of the more common groups of non-ferrous materials are copper-based alloys such as bronze and brass. While it is common to use brass and bronze interchangeably, there is a difference.
Brasses are copper-based alloys which have zinc as the principle alloying element. In some cases, small amounts of nickel, aluminum, iron, or silicon may be also present. A good example is C85500 (also known as “60-40 yellow brass”). This alloy contains up to 63% copper, 0.8% aluminum, and around 40% zinc. Since the zinc content is high, the material is classified as brass.
Bronzes are copper-based alloys where the major alloying element is not zinc or nickel. The term bronze is used with a preceding modifier that describes the type of bronze it is, by indicating the major alloying element(s). For example, MTEK 83-7-7-3/C93200 is a high lead tin bronze because it contains 7% tin and 7% lead in addition to 83% copper and 3% zinc. Also, MTEK 175/C95400 is called an aluminum bronze because it is made up of 11% aluminum in addition to 85% copper and 4% iron.
Surfing around the reaches of cable TV the other night, we came across an airing of Atlas Shrugged. In the book/movie, Hank Rearden has developed a brand new light-weight high-performance alloy for railroads that threatens to revolutionize the industry. Called “Rearden Metal” (once his career-savvy Marketing guys get a hold of it), Hank is protective of the chemistry and properties of the metal - other than to assert its superiority in the manufacture of train rails.
The burgeoning US rail industry in the late 1800’s was facing Rearden-like conditions. Steel used in rail manufacture was of inconsistent quality – suppliers differed, manufacturing lots differed, and expectations between buyer and seller differed. A take-it-or-leave it attitude prevailed.
Enter Charles Dudley, the father of ASTM, now the American Society for Testing and Materials. Dudley engendered a collaborative process as a means to develop and adopt standards that were acceptable to both producers and users. What began with railroad steel has expanded through the efforts of ASTM, DIN, BSI, JSA, AFNOR and others to thousands of other materials used in countless applications.
ASTM standards describe the composition of alloys, minimum mechanical properties that the materials must exhibit when test bars are evaluated, and standards for how those tests are to be done. Customers know what to expect when designing components and suppliers know what properties must be achieved.
Walking across a grocery store parking lot, six-year-old Danny stumbled, fell down and did further damage to his already worn jeans. He looked up with little tears in his eyes and said, “Daddy, maybe you should get me pants made out of steel!” That got Daddy to thinking: What really is wear and what makes a metal resist it?
Among other qualities, metals are characterized by their toughness and by their hardness. Toughness is the ability of a material to absorb impact without fracturing. Hardness is the material’s ability to resist indentation, so typically the harder the material, the better it resists wear. But hard materials are, generally, not tough materials. A high impact application with a lot of wear would be a difficult environment. Metal selection often demands tradeoffs.
Like Danny’s jeans, wear in metals comes in various forms and can be caused by a variety of events.