When we were kids, my older brother and I were chocolate chip cookie lovers. On a regular basis, mother and grandmother indulged our addiction. However, I noticed that each used slightly different ingredients. The end result was that mom’s cookies were my favorite, while my brother was a fan of grandma’s chocolate chip creations. In a pinch, however, it didn’t matter whose cookies were cooling on the stove. It was all good.
The same thing can be seen in blade steel. There are a host of widely different alloys, each knife user having their own preference. In reality, however, many steels bear more than a passing similarity to each other. This is certainly true when you compare the Japanese AUS formulations with the domestically produced 440 series of blade steels.
Only the AUS4-A, which is roughly akin to 420HC, lies outside of this AUS/440 comparison. With its slightly lower Carbon component (0.40-0.45), as compared to 420HC (0.40-0.50), AUS4-A has a little less hardness and wear resistance. The Vanadium content (0.10-0.26), which is absent in 420HC, however, enables AUS4-A to perform quite similarly to 420HC.
The Carbon content of AUS6-A (0.55-0.65) is somewhat lower than that of 440A (0.60-0.75). The Vanadium component of AUS6-A, which is absent in 440A, allows the steel to achieve a slightly higher hardness value (Rc 56-58), when compared to 440A (Rc 56-57). The increase in hardness and wear resistance, however, is only one factor. Since AUS6-A has less chromium (13.0-14.5%) than 440A (16-18%), it also is less resistant to environmental invective. Otherwise, both steels are roughly comparable.
When comparing AUS8-A and 440B, we also see considerable similarity. Certainly, the AUS8-A Carbon content (070-0.75%) remains below that of 440B (0.75-0.95%). However, the addition of Nickel (0.49%) and Vanadium (0.10-0.26%), which are not found in 440B, enable AUS8-A to achieve slightly higher hardness values (Rc 58-62), as compared to 440B (Rc 56-60). When put to use, both steels provide nearly the same performance and most users will be unable to distinguish one from another.
Looking at the chemical formulations of AUS10-A and 440C, we see that both have some similarities. Where the significant difference lies can be found in the fact that AUS10-A possesses both Nickel (0.49%) and Vanadium (0.10-0.27%), which are not part of the 440C chemical makeup. Since the Carbon component of both formulations is similar, the Nickel and Vanadium in AUS10-A can provide increased hardness potential if heat-treated properly. While AUS10-A has less Chromium (13.00-14.50%) than 440C (16.00-18.00%), the added Nickel does enhance corrosion resistance. Users report that both AUS10-A and 440C provide similar performance, with AUS10-A offering a smidgen more wear resistance.