Why is steel so hard

Here is a plot showing the correlation between grain size and packet and block size [12]:. Another important factor that controls the size of the packets and blocks in carbon content; the higher the carbon content the smaller the packets and blocks. This is another mechanism by which higher carbon leads to stronger martensite [13][14]:. You can see in the schematic how the packets, blocks, and laths are decreased in size with increasing carbon content.

You can also see in the 0. Higher carbon leads to a shift between laths and plates [15]:. You might remember from the Effect of Grain Size article that you have definitely read by now that dislocation motion preferentially occurs along close-packed planes of atoms [17]:. The Body Centered Tetragonal BCT has a low number of slip planes available for dislocation motion so the microstructure itself makes dislocation movement more difficult.

Martensite gains its high strength through several mechanisms. It is not entirely known which of the mechanisms are the most important, but I covered several of the major ones:. There is a lot of technical information in this article to better understand how the martensite transformation works and how it makes steel hard and strong. Some of this detail is more than is necessary to know how to make a knife.

The bottom line is that quenching steel from high temperature makes it hard, the transformation to martensite makes it hard, and more carbon in the martensite makes it harder. This information should contribute to your understanding when reading other articles on heat treating such as what I wrote in Austenitizing Parts 1 , 2, and 3.

A question you may have asked yourself is this: why is martensite body centered tetragonal elongated cube rather than just a bigger cube? Why is the carbon preferentially located in one direction? We have to go back to the face centered cubic microstructure of the high temperature austenite, which has interstitial carbon atoms between its iron-iron bonds [19]:. There are two unit cells of austenite shown for a reason, because when you stick two of them together, you can find a unit cell that looks very much like body centered cubic ferrite, as is shown by the dark lines in this schematic [19]:.

Nishikawa, and T. ASM 62 : Inoue, H. Mimura, and Y. Iron Steel Inst. Kikumoto, H. This can be achieved by refining the structure and applying alloying techniques and thus furthering its utility value. We will have to find out ways to use steel and be ready to face a stiff competition from Aluminium in the future. Importance Of Steel. The various uses of steel which in turn is a measure of adaptability of steel can be judged from the following characteristics of steel : Hot and cold formable Weldable Suitable machinability Hard, tough and wear resistant Corrosion resistant Heat resistant and resistance to deformation at high temperatures.

At a glance, it might seem like only industrial and commercial industries are dealing with the problem, but consumer-facing businesses are, too. However, with most of the world opening back up, operations will be getting back on track.

The problem with steel is that production is already way behind, and demand — along with orders — continues to grow. So, even though the market is headed in the right direction, it will be a while before the supply is above water again. Overall, this translates to massive shortages even across adjacent industries. Without steel, construction and product development cannot move forward. And those are just two examples out of many.

The entire manufacturing industry is in a tight spot, and that problem compounds even more when you factor in the equipment and machinery needed to advance operations. From heavy machinery to automated hardware, steel is a major component of these systems.

Ironically, the machining process for steel requires equipment made of steel, which presents a unique yet challenging conundrum. Steel is dominant because of its strength, superb corrosion resistance, and relatively low cost. Although, with prices skyrocketing, the cost-benefit has gone out the window. Aluminum , titanium , and superglass are some alternatives that may be usable in the future after the materials have improved further.

Aluminum, for example, is much more brittle and not durable at high temperatures. Similarly, metallic glass is tough but requires expensive palladium. If an alternative to palladium can be found, the accessibility of superglass will grow. But that assumes normal market conditions. Steel producers are facing their own higher costs following a rise in scrap and iron ore prices. Logistical challenges, like container shortages, and thin overseas supply are keeping imports in check.

But some distributors expect imports to pick up by June if the domestic market remains tight. Uncertainty over the tariff outlook is one factor keeping the wraps on domestic steel output. Angela Reed, an executive at Atlanta-based steel distributor Reibus International, says an expected review of the import restrictions is delaying a ramp-up in production and a build-up in inventories as easing of the curbs will likely drive down the domestic prices.