AR400 is a speciality steel designed at the chemical level for improved wear resistance for very specific applications. The steel is relatively expensive to produce, costing much more than simple mild steels such as A36 or 1018. However, the steel's special properties make it the only choice for applications such as blades in bulldozers.
AR400 contains many of the same elements as other tool steel, according to Baldwin International, a company that makes a steel based on AR400. This includes carbon (.30 per cent), manganese (.48 per cent), silicon (.25 per cent), molybdenum (.20 per cent), chromium (.88 per cent), sulphur (.04 per cent) and phosphorous (.035 per cent). Each of these elements is added for particular reasons and characteristics. Chromium adds corrosion resistance but also increases the material's hardenability, wear resistance and abrasion resistance. Molybdenum also increases the steel's hardenability but more importantly, it reduces the steel's risk of temper brittleness.
Physical properties account for a steel's ability to be machined, formed or manipulated. It also includes a steel's tension strength and yield strength. The tensile strength of AR400, often referred to as the ultimate strength, has been measured at about 200 kilograms per square inch, far more than commercial steels like American Iron and Steel Institute 1045 which has a measured tensile strength of only 90 ksi. AR400 also exceeds other steels in terms of yield strength, or the measurement at which a material begins to deform. AR400 has a yield strength of 250 ksi compared with only 50 ksi in AISI 1045.
Because of the unique strengths of AR400, it is used in applications such as heavy machinery and steel plate applications. In addition to the abrasion resistance benefits, AR400 has increased impact resistance. This translates to digger blades and buckets on heavy machinery that can not only withstand impacts from stones and other debris, but the constant movement of dirt doesn't wear the steel down as quickly as other steels would.