Method for the production of continuously cast billets rolled low carbon steel for cold massive forming geometrically-complex fasteners

 

(57) Abstract:

The invention relates to the field of metallurgy, in particular to the production of rolled low-carbon steel for cold massive forming fasteners particularly complex form. The technical result of the invention to provide directly in the mill stream (without additional spheroidizing annealing) patterns of long steel products that provide sustainable conditions for cold massive forming geometrically-complex fasteners while providing high technological characteristics of the steel. Method for the production of long-rolled products includes steel smelting in the electric furnace, secondary treatment, continuous casting with stream protection with argon, hot rolling of continuously cast billets, the winding of the rolled riots smelted steel containing wt.%: carbon 0,17-0,25; manganese between 0.30 to 0.65; silicon from 0.01 to 0.17; chrome 0,01-0,50; sulfur of 0,005 0,020; vanadium from 0.005 to 0.07; niobium 0,05-0,02; calcium 0,001-0,010; iron rest. And: 12/S-Mn/0,0227; 0.466 V+8Nb0,22; Sa/S 0,065. Microalloying of steel vanadium inhibits the processes of recrystallization of the steel at a temperature of finish rolling 900-950 C that enables technology kontroliruemymi structure of austenite, favorable for accelerating the spheroidizing steel. Hot rolling of long products start at a temperature of 900-950 C and finished at a temperature of 740-850, with the deformation in the last passes of at least 20%. After rolling in the temperature range 600-S cool car with a speed of 5-20C/min, the Invention eliminates spheroidizing annealing of rolled steel in coils. 1 C.p. f-crystals.

The invention relates to the field of metallurgy, in particular to the production of rolled low-carbon steel for cold massive forming fasteners particularly complex form

The most important requirement of rolled steel of low carbon steel for cold massive forming fasteners particularly complex form, is, on the one hand, the high technological plasticity and low coefficient of strain hardening in the state of delivery and, on the other hand, the ability to provide the specified level of consumer properties of finished products. This steel from blending until ready rolled it takes a long processing, comprising the following operations: smelting, hot rolling, spheroidizing annealing, calibration. The task of ensuring NTA strain hardening of the metal in the state of delivery currently successfully resolved through a number of techniques used at various stages of steel making.

Known structural steel containing, wt.%: carbon 0,17-0,22%; silicon 0,17-0,37%; manganese of 0.27 to 0.60 percent; chromium 0,30-0,50%; vanadium 0,05-0,08%; niobium 0,02-0,04%; the rest of the iron (SU 1728303A, IPC 7 With 22 38/26, 22.12.1991).

A known method for the production of long steel products, including steel smelting in the electric furnace, the production of metal, secondary treatment, continuous casting, hot rolling of continuously cast billets, cooling (EN 2156313 C1 21 D 8/02, 20.09.2000,).

The closest analogue to the claimed invention is a method of producing rolled low-carbon steel for cold massive forming fasteners including steel smelting in the electric furnace, secondary treatment, continuous casting, hot rolling of continuously cast billets and the winding distribution in the riots. (see EN 2180277 C1, 21 1/46).

The objective of the invention is the development of steel with advanced technology of plasticity and method of manufacturing it rolled, providing directly into the mill stream (without additional spheroidizing annealing) rolled. The technical result of the invention is napravilnyh fasteners.

To achieve a technical result in the known method, including steel smelting in the electric furnace, secondary treatment, continuous casting, hot rolling of continuously cast billets and winding rental in riots, smelted steel in the following ratio, wt.%:

Carbon 0,17-0,25

Manganese between 0.30 to 0.65

Silicon, from 0.01 to 0.17

Chrome 0,01-0,50

Sera of 0,005 0,020

Vanadium from 0.005 to 0.07

Niobium 0,005-0,02

Calcium 0,001-0,010

Iron Rest

when performing correlations

0,466 V+8Nb0,22;

hot rolling starting at a temperature of 900-950 C and end at 740-850 with the degree of deformation of at least 20%, after rolling conduct regulated cooling in the temperature range 600-C with a cooling rate of 5-20C/s

Given the combination of alloying elements (p. 1) allow to get in the proposed steel rod with a diameter up to 25 mm), after controlled rolling of a homogeneous fine structure spheroidizing perlite with a favorable combination of strength and ductility.

Carbon and carbonitrides (vanadium, niobium, elements are introduced into the composition of this steel to ensure m is the level of origenaly steel. While niobium manages the processes in the upper part of the austenitic region (determines the tendency to grain growth of austenite, and vanadium in the lower part of the austenitic region (stabilizes the structure during thermomechanical processing, increases the temperature of recrystallization and, consequently, affects the character --transformation. Vanadium and niobium also contribute to the hardening of steel. The upper limit of carbon content (0,25%), vanadium (0,07%), niobium (0,02%) due to the need to ensure the required level of ductility of steel, and the bottom, respectively 0,17%; 0,005%; 0,005% by providing the required strength level of the steel.

Manganese and chromium are used, on the one hand, as a solid solution hardeners, on the other hand, as elements, greatly increasing the stability of the supercooled austenite and increases the hardenability of steel. The upper levels of manganese - 0.65% chromium, 0.50% is determined by the need to ensure the required level of ductility of steel, and the lower - 0.30% and 0.01%, respectively, of the need to ensure the required level of strength and hardenability of the steel.

Silicon belongs to territooriumil elements. The lower limit for silicon - 0,01% due to the surface of the steel.

Calcium is an element, modifying nonmetallic inclusions. The upper limit (0,010%) as in the case of sulfur caused by the necessity of obtaining a given level of ductility and toughness of steel, and the lower (0.001%) limit issues-tech production.

Sulfur determines the level of ductility of steel. The upper limit (0,020%) due to the necessity of obtaining a given level of ductility and toughness of steel, and the lower limit (0,005%) questions-tech production.

Ratio 0,466 V+8Nb0,22;

define the conditions ensure the specified characteristics of plasticity and proclaimeth cold steel at the drop-forging of geometrically-complex fasteners.

An example of the method.

Smelting of low carbon steel of the following composition: carbon - 0,21%; manganese - 0,45%; silicon - 0,10%; chromium - 0,20%; sulfur - 0,011%; vanadium - 0,03%; niobium - 0,01%; calcium - 0,001%; produced 150-ton electric arc furnaces (EAF) using the mixture of 100% DRI pellets, allowing for the mass fraction of nitrogen before the release of the DSP is not more of 0.003% and a low content of non-ferrous impurities. Pre-alloying metal to manganese and silicon is produced in coverea which steel raskalyaetsya aluminum. After that, the metal is fed to the Assembly of complex processing of steel (AKOS), on which there is a possibility of heating the metal to the required temperature, flushing it with argon through bottom vent unit, dosed additives necessary ferroalloys and steel flux-cored wire with various fillers. On the AKOS is pointing refining slag additive lime and fluorspar, deoxidizing slag granulated aluminum alloying metal aluminum content 0,050%, lapping metal content of manganese, heating up to the temperature optimum for further processing. After processing Agos metal is exposed to the vacuum processing on portions of the degasser. During degassing is the final adjustment of the chemical composition. When use cases for doped vanadium and niobium their additive is also under vacuum. After degassing the metal is processed by the silicocalcium and transferred to the casting process. The casting is on chetyrehluchevoy machine radial type in the ingot sizes 300360 mm with a speed of extrusion of 0.6-0.7 m/min, protecting the metal from oxidation by the use of top slag subspecial getting low content of nitrogen and oxygen and purity of the metal non-metallic inclusions. After casting and cut-to-length the length of the received continuous cast billet was cooled furnaces controlled cooling. Hot rolling of long products start at a temperature of 900-950 C and finished at a temperature of 740-850, with the deformation in the last passes of at least 20%. After rolling is used in the temperature range 600-S modes regulated cooling of rental with 5 speed-20C/min

The execution ratio of the alloying elements helped to provide the required level of ductility of steel directly in the hot rolled condition level =25% and the level of cold precipitation sample with a diameter of 20 mm to 75% of the height.

when the content of manganese - 0,45%; carbon - 0,21%;

6V+8Nb=0,26 when the vanadium content of 0.03%; niobium - 0,01%;

when the sulfur - 0,011%, calcium - 0.001%.

The introduction of the proposed method of production of rolled low-carbon steel of high hardenability providing directly into the mill stream (without additional spheroidizing annealing) patterns of rolled guaranteeing the rational conditions of cold massive forming geometrically-complex fasteners.

1. JV is selected fasteners, includes steel smelting in the electric furnace, the production of metal, secondary treatment, continuous casting, hot rolling of continuously cast billets and the winding of the rolled coils, characterized in that the smelted steel, in the following ratio, wt.%:

Carbon 0,17-0,25

Manganese between 0.30 to 0.65

Silicon, from 0.01 to 0.17

Chrome 0,01-0,50

Sera of 0,005 0,020

Vanadium from 0.005 to 0.07

Niobium 0,005-0,02

Calcium 0,001-0,010

Iron Rest

when performing correlations

0,466 V+8Nb0,22;

where C is carbon;

Mn - manganese;

V is vanadium;

Nb - niobium;

CA - calcium;

S - sulfur

hot rolling starting at a temperature of 900-950 C and end at 740-850 with the degree of deformation of at least 20%, after rolling conduct regulated cooling in the temperature range 600-C with a cooling rate of 5-20S/s

2. The method according to p. 1, wherein during the continuous casting of steel are stream protection with argon.

 

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