Preparation And Investigation On Properties Of 15B37HC Fork Arm Steel

Based on intermediate carbon alloy structural steel micro-alloyed with additional appropriate elements of Cr,B,and Ti,15B37HC fork arm steel with good hardenability and excellent mechanical properties were prepared by using the technique of long flow converter and short process refining furnace,combined with the methods of control rolling and finishing. The gain size,microstructure,strength,hardness,low-temperature impact toughness,wearing resistance,and hardenability were studied.The content of C(%) should be controlled at about 0.32%to ensure the general mechanical properties of 15B37HC steel.The strength,toughness and hardenability were improved by adding element of Ti to refine grain size and also adding element of B,Cr,etc.for micro-alloyed.In addition,it will ensure proper strength and will not reduce the low temperature impact toughness at the same time by increasing the Mn content appropriately and limiting Si content.Thus the general mechanical properties of steel can be ensured after heat treatment.The macro-structure of the billet,especially for reducing the central segregation and rolled banded,can be improved after being adjusting and optimizing the parameter of process,such as, selecting an appropriate crystal pulling speed,using electromagnetic stirring with higher current.The grain size of steel is grade of 8 and it attributes to fine grain steel.The grain size and grain uniformity are greatly improved as well.The strength,hardness,toughness and hardenability of 15B37HC steel can be significant improved after being micro-alloyed.The mechanical properties,e.g.tensile strength is about 1090～1140MPa;elongation is about 15～17%;area reduction rate is 55～58%,which are greater than the agreement index.It is full in compliance with performance requirements.The hardness is 568HV after oil quenching,and is higher than the 1537HC steel 20HV around.The impact powery of 15B37HC steel after 510℃quenching and tempering is 75～98J under the temperature of -20℃.The hardenability is also greatly improved and the hardness of the required points lists as J1≥53.5,J11≥50.4 and J15≥49.5,respectively.It is greater than the requirements of the agreement.Furthermore friction and wearing tests show that the friction coefficient increases firstly and then decreases as the tempering temperature increasing for oil-quenched samples with little fluctuation,while the wearing volume-loss gets up which demonstrate a worse wearability. This is consistent with the variation of the hardness.All the properties of the 15B37HC steel are better than those of 1537HC steel approved by the reference tests.