SU657079A1 - Constructional steel - Google Patents

Description

The limits-a 1e of the aluminum concentration are chosen for reasons of obtaining the necessary degree of deoxidation of the steel, and the limits of the concentration of titanium on the one hand contribute to the preparation of the complex oxide phase, and on the other hand exclude the formation of unfavorable titanium nitrides. Carbon limits are limited, on the one hand, by the need to obtain high strength properties, and on the other hand, the requirements for toughness and good weldability. Silicon in the selected limits contributes to the improvement of the strength properties, not at the same time its cold resistance. Manganese, within the Selected Composition, strengthens the solid solution and increases the cold-resistance / w. Vanadium and niobium are among the most active nitride forming elements. In the stage with a high content of nitrogen, they form fine particles of carboitrides, due to which the grain is crushed and the strength properties, ductility and cold resistance of steel are increased. The limits of semiconducting niobium and vanadium correspond to the region of the most effective effect on the mechanical properties of steel. The nitrogen content in the selection limits, on the one hand, allows the grain to be crushed to the maximum, and on the other hand, eliminates the formation of bubbly ingots. Steel undergoes normalization at 90 ° -98 ° C (speed 2 min / mm, air-control:) 6

Table 94 When heated to 90 ° C, vanadium carbonitrides are dissolved in a solid solution, and then cooled again, they are released in the form of tiny particles. These carbonitride segregations serve as additional nuclei in the transformation, grinding the ferrite grain. The carbonitride particles released after austenitic transformation are much smaller than the particles formed in austenite, and generally have no coherent connection with the matrix, so their strengthening effect is not large. After the normalization of steel with vanadium nitrides, the strength characteristics (by 5–8 kg / mm 2) are lowered and plasticity and viscosity increase (by 2–4 kgm / cm at 40 ° C). Unlike vanadium carbonitrides, the dissociation temperature of carbonitrides is nioi much higher (1250 ° C), and therefore, during normalization (900-980 ° C), there is no significant softening and large increment of impact in vitality. In the proposed steel containing hot-rolled state at the same time, vanadium and niobium carbonitrides, after normalization, due to the presence of iobi, almost no reduction in strength properties is observed and, at the same time, the viscous properties of vanadium alloyed steel increase. All variants of the proposed steel after normalization have a ferritic-well structure. The chemical composition of the steel is presented in table 1, the mechanical properties in table 2.

Table2

Thus, the proposed construction steel, as compared to the known, allows to obtain, after normalization, similar strength properties with a lower content (0, OZ-O, 05%) of carbon and, therefore, to provide higher (2-3 units) values of impact strength. viscosity at negative temperatures, higher cold resistance and better weldability. The economic effect of used construction steel will be 1OO- 120 thousand rubles.

Claims (1)

1. USSR author's certificate Кь 336367, кл. C 22 C 38/12, 1975. biy, nitrogen and iron, so that, in order to increase and cold resistance, it additionally contains ali minium and titanium in the following ratio of components,%: 0, O6 -O, 3 Carbon Manganese 0.8-2.0 Silicon 0.17-1.0 Vanadium 0.01-0.25 0, OO5-O, 15 Niobium 0, O1-0, O4 / Chlorium 0.005-0, 10 Titan Oh, OO1-0, O15 Iron Else