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Konu Başlığı : Why use a master alloy?

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26-11-2021, Saat: 03:51
Why use a master alloy?
What is a master alloy and how is it different from a traditional alloy? And why is the use of master alloys so important in the field of jewelry? We find out in this article.

Most of the alloys in our catalog fall under the definition of master alloy and the question of what exactly is meant by this definition may arise.
An alloy is a compound made up of two or more elements, of which at least one is a metal. The characteristics of an alloy such as hardness, strength and even color are generally different from those of the elements that constitute it, for example copper and tin, both relatively soft, form the more resistant bronze.
A master alloy is a particular type of alloy designed to be added to a pure metal, in our case gold or silver, in order to modify its characteristics. A pre-master alloy is a master alloy from which a fundamental element has been subtracted. In our field, it is generally a master alloy from which silver was stolen for logistical reasons.

Why it is necessary to use a master alloy?
Most pure metals are not suitable for technical applications. Pure gold, for example, is extremely soft; this feature makes it easily workable and is one of the reasons for its success in jewelry, but a jewel made of pure gold would easily bend if treated without too much care and would not have sufficient wear resistance. The same considerations apply to silver. For this reason, pure gold is generally transformed into a gold alloy, according to the standard proportions indicated in twenty-fourths, or carats (K).


Until the Second World War, the most popular alloys were mainly formed by three elements: Gold, Silver and Copper.

With the evolution of technique, jewelry has required increasingly specialized performance from alloys, this has led to the need to study the use of new elements to be added to precious metals, which are able to drastically change their characteristics. So we went from having alloys composed of two or three elements, to new formulations that come to contain even 10, effectively increasing the complexity of the product.

What characteristics can a master alloy act on?
Once added to the precious metal, a master alloy can affect:
Color
A feature especially requested by users of gold, whose color can be changed to pink, gray-white or various shades of yellow.


Hardness
Perhaps the most important feature, as gold and silver are relatively soft when in their pure state. The hardness is controlled through the master alloys both directly, with the simple addition of alloying elements, and indirectly, making the precious metal capable of undergoing hardening heat treatments.


Melting temperature
it is another important parameter that in some applications it is useful to be able to control. Suppose we need to weld a joint, to do this we can use a particular alloy, which must melt at a lower temperature than the metal that forms the edges of the joint, in this way we will perform a particular type of welding called brazing.


The control of the melting temperature is also important in the case of casting with wax setting of stones, where too high a temperature of the metal could irreparably damage the stones.

Size of the crystalline grain
Using some elements called grain refiners it is possible to make the internal structure of the metal more compact, this greatly improves some aesthetic and technological aspects, we talked about i.


Fluidity
Fluidity is an important factor especially in investment casting applications. It can be described as the ability of a liquid metal to faithfully fill an elaborately shaped pattern, such as a grid or filigree.

Generally, the fluidity of precious metals increases as the casting temperature increases, but this can cause some side effects, such as interference between metal and refractory material, or evaporation of low-melting alloy elements. To overcome these problems, some elements, such as silicon, can be inserted in the master alloys for investment casting, which are able to increase the fluidity in the liquid state of the metal. In this article we have talked in detail about the role of silicon in investment casting alloys.
FeZr Master Alloys
The ferro zirconium 80% master alloy is employed in the ferrous metal industry. Zirconium is a strong grain refiner and denitrifier, a powerful deoxidizer and also acts as an excellent sulfide shape controller. Appropriate additions of zirconium enhance impact resistance, yield strength and the hardenability of steels.
In addition, the alloy can be utilized as a zirconium additive and serves as a beneficial trace element in cobalt and nickel-based super alloys wherein iron does not have a detrimental influence.
Applications of FeZr Master Alloys
  • FeZr serves as a grain refiner in steel and cast iron

  • FeZr is used in carbide formation, desulphurisation, deoxidation, nitrogen scavenging
Ferro-Zirconium or more accurately, Zirconium-Iron (80% Zr: 20% Iron), is a master alloy used in the production of stainless steels, special steels and some cobalt and nickel-base superalloys. As with copper-zirconium, this master alloy is a means by which Zirconium is added to an alloy.

Zirconium is a strong grain refiner but also acts as a ‘getter’ of nitrogen, sulphides and oxides while aiding carbide formation. The addition of Zirconium improves impact resistance, yield strength and hardenability (a measure of the capacity of steel to be hardened in depth when quenched from its austenitic temperature).

At Lipmann Walton & Co Ltd, we commission production of 5x50mm FeZr lumps through our partners. We focus on tin-free FeZr by carefully controlling the Zirconium raw materials selected for re-melting, though tin-bearing FeZr is also available.

Ferro-Zirconium master alloy can be easily confused with ferro silicon zirconium, with dramatic effects. It is thought that a contributing factor in the Deepwater Horizon oil spill could have been the misuse of FeSiZr alloy instead of FeZr, which would have weakened components in the pipework. FeSiZr contains less than half the Zirconium content of FeZr master alloy.

Recent novel applications of special steels made with FeZr are exploited in certain amorphous alloy formulations. These applications are industrial hardware components for civil and marine construction, plant boiler tubes, gears and so forth as well as protective coatings for industrial machinery such as pipelines.
Why using rare metals to clean up the planet is no cheap fix
WE REAP seven times as much energy from the wind and 44 times as much energy from the sun as we did a decade ago. Is this good news? Guillaume Pitron, a French journalist and documentary maker, isn’t sure.
He is neither a climate sceptic nor a fan of inaction. But as the world moves to adopt a target of net-zero carbon emissions by 2050, Pitron worries about the costs. The figures in his book The Rare Metals War are stark. Changing the energy model means doubling the production of rare metals about every 15 years, mostly to satisfy demand for non-ferrous magnets and lithium-ion batteries. “At this rate,” writes Pitron, “over the next 30 years we… will need to mine more mineral ores than humans have extracted over the last 70,000 years.”
Before the Renaissance, humans had found uses for seven metals. During the industrial revolution, this increased to a mere dozen. Today, we have found uses for all 90-odd of them, and some are very rare. Neodymium and gallium, for instance, are found in iron ore, but there is 1200 times less neodymium and up to 2650 times less gallium than there is iron.

Zipping from an abandoned mine in the Mojave desert to the toxic lakes and cancer-afflicted areas of Baotou in China, Pitron weighs the awful price of refining the materials, ably blending investigative journalism with insights from science, politics and business.
There are two sides to Pitron’s story, woven seamlessly together. First, there is the economic story of how China worked to dominate the energy and digital transition. It now controls 95 per cent of the rare earth metals market, making between 80 and 90 per cent of the batteries for electric vehicles, says Pitron, and more than half the magnets in wind turbines and electric motors.
Then there is the ecological story of the lengths China took to succeed. Today, 10 per cent of its arable land is contaminated by heavy metals, 80 per cent of its groundwater isn’t fit for consumption and air pollution contributes to around 1.6 million deaths a year there, according to Pitron (a recent paper in The Lancet says 1.24 million deaths in China a year are attributable to air pollution – but let’s not quibble).
China freely entered into this Faustian bargain. Yet it wouldn’t have been possible had the Western world not outsourced its own industrial activities, creating a planet divided, as Pitron memorably describes it, “between the dirty and those who pretend to be clean”.
The West’s comeuppance is at hand, as its manufacturers, starved of rare metals, must take their technologies to China. It should have seen how its reliance on Chinese raw materials would quickly morph into a dependence on China for the technologies of the energy and digital transition.
By 2040, in our pursuit of ever-greater connectivity and a cleaner atmosphere, we will need to mine three times more rare earth metals, five times more tellurium, 12 times more cobalt and 16 times more lithium than we do now. China’s ecological ruination and global technological dominance advance in lockstep, unstoppably, unless the West and others start to mine for rare metals in Brazil, the US, Russia, Turkey, South Africa, Thailand and Pitron’s native France.


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