Effects of addition of some elements on properties of Si-Mn structural steel were investigated. In the report I (Tetsu to Hagané, Vol.45, No.10 (1959) 1158), the effects of addition of V were researched, while in this report II, effects of B and Mo on Si-Mn and Si-Mn-Cr structural steel were studied.
There were four groups among specimens tested:
The 1st group, containing 4 grades steel, was prepared for testing the effects of B on properties of Si-Mn steel. The 2nd group, containing 3 grades of steel, was for testing the effects of B with Mo on properties of Si-Mn steel. The 3rd group, containing 3 grades ofsteel, was for testing B, and the 4th group, was for B with Mo on properties of Si-Mn-Cr steel.
All samples were melted by a high-frequency induction furnace and cast into 10 kg ingots, and then rolled or forged down to 16mm ∅; bars.
The specimens were tested under various conditions; such as rolled or as forged, furnacecooled or air-cooled after heating and, as quenched-and-tempered.
Mechanical properties as well as hardenability were tested.
It was concluded as follows:
(1) Addition of B to Si-Mn steel was found to enhance both tensile and yield strength as well as hardness, with specimens subjected to quenching and tempering treatment. No appreciable effcet of B, however, was recognized on the strength and hardness of the steel in the case of furnace-cooling or air-cooling treatment. Addition of 0.0050% B to these grades of steel was presumably essential to give the best result on the strength of specimens as quenched and tempered.
(2) Addition of both B and 0.5% Mo to Si-Mn steel improved the yield and tensile strength as well as hardness of the specimen as quenched and tempered. The similar effects were observed on the hardness of specimens subjected to furnace-cooling or air-cooling. It was found that 0.0050% B was suitable to give the best effect for strengthening of the steels after air cooling or furnace cooling, but that 0.0100% B was essential to give the best effect on it after quenching and tempering.
(3) Addition of both B and Mo to Si-Mn steel resulted in an increase of pearlitic hardenability, where as addition of only B had no effect on it.