The appearance of low-alloy steel can be traced back to the 1870s of the 19th century, a steel with a carbon content of 0.64 to 0.9% and a chromium content of 0.54 to 0.68%, a tensile strength of 685 MPa, and an elastic limit of 410 MPa. It was first used in engineering structures and construction. An arched bridge spanning 158.5m. However, this steel is not ideal, and it requires a post-rolling heat treatment, which is difficult to machine and has poor corrosion resistance. For more than a century, countries around the world have continued to explore, and in general, low-alloy steel can be divided into three different stages of development, before the 1920s, after the 20s and 60s and after the 1960s. The first two stages are collectively referred to as the traditional low-alloy steel development stage, and the latter stage can be called the modern low-alloy steel development stage (we call it Microalloyed Steel later).
From single element alloying to multi-element alloying
In 1895, the Russian "Eagle" class destroyer was built with 0.40 to 0.56% C and 3.5% Ni steel. The steel is much more processable than the initial chrome steel and has a yield strength of 355 MPa. At the beginning of the 20th century, more than 8,000 tons of nickel-containing steel was used to build a bridge with a span of 448 m. The fly in the ointment is that the steel has limited alloy resources and high cost. Since then, 1.25% Si low-alloy steel has been developed, and transatlantic ships and bridges spanning 110m have been built. Russia has used iron-copper mixed source and developed low-alloy steel of 0.7-1.1% Cu for shipbuilding and bridge construction. The steel has good conductivity and excellent corrosion resistance.
With more than 30 years of experience in production and application, it has been found that multi-alloyed low-alloy steels have better overall performance and are more economical, and have developed binary alloyed Ni-Cr, Cr-Mn, and Mn-V low alloys. Steel, and ternary composite alloyed low alloy steel such as Cr-Mn-V, Cr-Mn-Si, Mn-Cu-P. The use has also expanded to include boilers, vessels, buildings and towers. In the 1920s, the world's low-alloy steel production reached 2 million tons.