3 Metals for Machine Tools
Metals are the primary materials fabricated in the machine shop. The science of the chemistry of metals and its physical engineering is called metallurgy. This type of scientist is a metallurgist. A machinist still needs to know a good deal about metallurgy because they fabricate so many types of metals. Let’s start with thinking about four different groups of metals.
Group 1: Carbon steels are a type of ferrous metal which contains iron. Carbon plays a large role with ferrous metals. Carbon added to iron produces steel. It behaves differently depending on the amount of carbon in the iron. Generally, the more carbon the harder the steel. The drawback is that the more carbon in the steel the more brittle it becomes.
- Low-carbon steel (iron and from .1 to .3% carbon- example product: bolts)
- Medium-carbon steel (iron and from .3 to .6% carbon – example product: car axles)
- High-carbon steel (iron and from .6 to 1.7% carbon- example product: hammers)
Group 2: Ferrous alloys improve the properties of steel by adding specific elements.
- Stainless steel has added chromium and nickel. It is used for kitchen ware.
- High Speed Steel has added tungsten. Machine tool cutting tools are an example.
Group 3: Nonferrous metallic materials. These metals do not contain iron.
- Aluminum is rarely used in unalloyed state.
- Copper is used widely as wire for the electrical and electronics industries.
- Nickel can be found as plating on steel.
- Zinc is used to galvanize the surface of steel to prevent rust or oxidation.
Closeup of a galvanized steel Strong Tie. Image: CC0
Galvanized spangle refers to the visible crystalline pattern visible on the surface of galvanized steel. The pattern forms due to alloying elements or impurities that are present in the liquid zinc used in the galvanizing process.
Group 4: Non ferrous metallic alloys. Examples:
- Aluminum alloys are aluminum plus other elements. Airplane frames rely on this lighter-weight metal alloy.
- Bronze is a mixture of copper and tin. It is used widely for decorative purposes.
- Brass is a mixture of copper and zinc. Its anti-corrosive properties make is ideal for ship hardware.
Video
Watch this most excellent 17:57 video Understanding Metals by the Efficient Engineer June 8, 2021. It provides a very good overview of the information you should have about metals.
The majority of information in this book is about the physical and/or mechanical properties of metals that are important for production and fabrication metal workers to understand. These properties sometimes rely on the chemical definitions as we have covered here.
Derived from Metal – Wikipedia accessed and available online 24 January 2024, and The Virtual Machine Shop (jjjtrain.com/metallurgy) accessed and available via the WayBack Machine 15 January 2024.
