Steel

 

The invention relates to ferrous metallurgy, in particular to the finding of high strength steels for bolts of the rail. The objective of the invention is the improvement of the complex mechanical properties of steel. Steel contains carbon, silicon, manganese, chromium, vanadium, calcium, aluminum, nitrogen and iron in the following ratio of components, wt. %: carbon of 0.15 to 0.19; manganese 0,40-0,60; silicon 0.25 to 0,37; chrome 0,20-0,35; vanadium 0,05-0,09; calcium 0,0005-0,004; nitrogen 0,004-0,020; iron - rest. In addition, the steel composition is further limited to the amount of impurities in the following ratio, wt.%: sulfur does not exceed 0.025; phosphorus does not exceed 0.025; Nickel does not exceed 0.30; copper does not exceed 0.30; aluminum of 0,005 0,035; Declare the chemical composition of the steel improves the mechanical properties of steel and operational stability of the bolts. 1 C.p. f-crystals, 2 tab.

The invention relates to ferrous metallurgy, in particular to research of high-strength steel for bolted mounting rails.

Known as the prototype steel [1], containing: carbon 0,12-0,19%, silicon 0,17-0,37%, manganese 0,35-0,65%, chromium not more than 0,25%, iron - rest.

A significant drawback of steel are low mechanical properties, leading to low quality bolts and output Poslednyaya this steel, containing carbon, silicon, manganese, chromium, further comprises vanadium, calcium, aluminum and nitrogen in the following ratio of components (wt.%): Carbon - 0,15-0,19 Manganese - 0,40-0,60 Silicon - 0,25-0,37 Chrome - 0,20-0,35 vanadium 0.05 to 0.09 Calcium - 0,0005-0,004 Nitrogen - 0,004-0,020 Iron - Rest in Addition, it is further limited to the amount of impurities in the following ratio (wt.%):
Sulfur is Not more than 0,025
Phosphorus - Not more than 0,025
Nickel is Not more than 0,30
Copper - No more than 0,30
Aluminum - 0,005-0,035
The inventive chemical composition of the steel selected based on the following assumptions.

Selected carbon content increases the yield strength and the temporary rupture strength of bolt products.

The ratio of manganese and silicon in the claimed limits ensures, on the one hand, the desired strength and wear resistance, on the other hand, the hardness of steel.

Increasing the chromium content in comparison with the prototype allows to significantly improve the strength characteristics of steel, hardness and wear resistance of steel. Upon receipt in steel chromium concentration less than 0,20% not provided the required values of yield strength and temporary tear resistance, while increasing 0.35% umalali calcium has a positive effect on microstructure - there is a change in the grain and produce favorable (globular) form of sulfide, oxide and oxysulfide inclusions. With the introduction of calcium more than 0.004% significantly increases the cost of steel without increasing the mechanical properties. Included in the steel vanadium increases the hardness, strength and slightly plasticity. Aluminum is introduced into the claimed limits, provides the fine grains; increase in concentration above the top of the proposed limit leads to higher rejection steel surface defects and reduce the impact toughness of the steel. Reducing the aluminum content of less than 0,005% significantly escalates the grain of the steel, which does not provide the required marsvolta. When the aluminum concentration is higher than 0.035% of possible contamination of the steel alumina-containing non-metallic inclusions, dramatically increasing the probability of crack formation on the bolts. Nitrogen, connecting with nitridebased elements (vanadium and aluminum), grinds the grain and provides a nitride hardening steel. When the content of nitrogen than 0,020% increased rejection of steel defects of the macrostructure (bubbles, cracks and surface cracks, voloviny), thus reducing the strength of steel. Reducing sadvabana, on the basis of ensuring the quality of the surface after rolling (with the exception of the formation of hot cracks).

To determine the mechanical properties of the inventive steel was melted a series of heats (declared outside the chemical composition of steel) 100-ton electric arc furnaces type EAF-I. Chemical composition shown in table 1.

Rolling steel was carried out at the bars with a diameter of 21 mm Mechanical tests according to the requirements of the State standards are shown in table 2.

According to the results of the claimed steel in comparison with the prototype has the following advantages: increase the mechanical properties of the steel.

Literature
1. GOST 1050-88 "car gauged bars with special surface finish quality carbon structural steel. General technical conditions".


Claims

1. Steel containing carbon, silicon, manganese, chromium, characterized in that it further comprises vanadium, calcium and nitrogen in the following ratio, wt.%:

Carbon 0,15-0,19

Manganese 0,40-0,60

Silicon 0.25 to 0,37

Chrome 0,20-0,35

Vanadium 0,05-0,09

Calcium 0,0005-0,004

Nitrogen 0,004-0,020

about impurities in the following ratio, wt.%:

Sulfur does Not exceed 0.025

Phosphorus does Not exceed 0.025

Nickel does Not exceed 0.30

Copper does Not exceed 0.30

Aluminum of 0,005 0,035

 

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