RU2003729C1 - Steel - Google Patents

Abstract

The invention relates to ferrous metallurgy, mainly to structural steels used in automobile and tractor engineering for the manufacture of axle shafts and other heavily loaded parts, hardened by surface hardening with induction heating. The purpose of the invention is to obtain steel that is technologically advanced in the metallurgical industry, with increased coolness and favorable heredity, which makes it possible to obtain the necessary microstructure in finished products, as well as increased strength and ductility. Steel additionally contains vanadium in the following ratio of components, wt%: carbon 0.44 - 0.53; silicon 0.17-0.37; Manganese 0.90 - 1.30; aluminum 0.01 - 0.05; titanium 0.01 - 0.03; vanadium 0.05 - 0.12; calcium 0.0001 - 0.003; nitrogen 0.006-0.012; the rest is iron, when the ratio is satisfied: {(aluminum + titanium + vanadium) / nitrogen} 2: 6. 1 tab.

Description

The invention relates to ferrous metallurgy, mainly to structural steels used in automobiles and tractor engineering for the manufacture of semi-axes and other heavy-loaded parts hardened by surface hardening with induction heating.

Known steel 50G (GOST 4543-71} of the following chemical composition, wt.%:

Carbon 0.48-0.56

Silicon 0.17-0.37

Manganese 0.70-1.00.

IronOther

A disadvantage of the known steel grade is its insufficient strength and hardenability, as well as its sensitivity to overheating.

The closest to the proposed technical essence and the achieved pe-v result is steel grade 47GT 1 composition, wt.%:

Carbon 0.44-0.52

Manganese 0.92-1.25

Silicon 0.06-0.20

Aluminum 0.01-0.05

Nickel 0.06-0.19

Copper 0.05-0.19

Nitrogen 0.002-0.007

Calcium 0.0001-0.0010

T tan -0.01-0.03

IronOther

The disadvantage of this steel is the poor processability during smelting and rolling, as well as the unsatisfactory quality of the products, as evidenced by the presence of defects in cracks both in hot rolled and in turned state.

The purpose of the invention is the production of technological steel in metallurgical production with increased hardenability and favorable heredity, which makes it possible to provide the necessary microstructure in finished products, as well as increased strength and ductility.

The goal is achieved in that the steel containing carbon, silicon, manganese, aluminum, titanium, calcium, nitrogen, iron, additionally contains vanadium in the following ratio, wt.%:

Carbon 0.44-0.53

Silicon 0.17-0.37

Manganese .90-1.30

Aluminum 0.01-0.05

 Titanium 0.01-0.03

Vanadium 0.05-0.12

Calcium 0.0001-0.003

Nitrogen Not more than 0.012

IronOther

while providing a ratio of AI + Ti + V. th

.

A vanadium content below 0.05 wt.% Does not provide a sufficient effect to increase the calcined ™ and to inhibit the migration of austenite grain boundaries upon heating for rolling. A vanadium content above 0.12 wt.% For the proposed chemical composition of the steel may cause through hardenability and increased hardness of the core of the finished parts.

The introduction of vanadium steel in the range of 0.05-0.12 wt.% Allows to obtain the required level of strength and regulated hardenability, providing high resistance to alternating and impact loads.

The presence of vanadium in combination with other modifying elements (A1, P)

in the ratio rj 6 forms

hereditary fine-grained steel, due to which the length of the borders increases and their purity with respect to harmful impurities (oxygen, sulfur, phosphorus, etc.) increases. As a result, an increased level of plasticity is achieved in the hot rolled state and after

tremoprocessing of finished products. In addition, hereditarily fine-grained steel is not prone to overheating, which is an important technological prerequisite for reducing scrap during its manufacture.

Example p. Steel is smelted in 300- and 600-ton open-hearth furnaces. The metal is deoxidized in a combined way: silicomanganese in the furnace, ferrosilicon, ferrotitanium, ferrovanadium, and calcium calcium

and aluminum in the bucket. Poured into varietal molds with profitable extensions through a glass-collector with a diameter of 60 mm. Ingots weighing 8 tons are rolled onto billets of square section 150 X 150 mm, then

into a circle with a diameter of 52 mm, then cut into measured lengths and grind it with a cutter into a circle with a diameter of 50 mm.

Fur: further tests of experimental steel are carried out in accordance with GOST 1497-84 on samples

after heat treatment according to the regime: quenching from 850 ° С to oil, tempering 600 ° С. The penetrability is determined on standard samples according to GOST 5657-69.

In order to evaluate the quality of the proposed steel, the consumer also tests finished axle shafts.

The chemical composition of steel and its properties are shown in the table.

As follows from the above data, the proposed structural steel (compositions 1-4) has, in comparison with the known (composition 5) increased strength and deep hardenability in combination with a high level of plastic properties.

A pilot industrial batch of long products of the proposed steel in the amount of 4240 tons was tested at KAMAZ JSC for the manufacture of the leading axles of KAMAZ-55111 advanced vehicles

designs. Tests of finished parts made of experimental steel showed that they are 30% higher than the serial parts made of steel 47GT in strength characteristics and can be used for machines with increased carrying capacity and engine power.

(56) 1. USSR Copyright Certificate Ms 1250592, cl. C 22 C 38/16, 1986,

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