Method for the production of continuously cast billets rolled with spheroidizing structure of 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 geometrically-complex fasteners. The technical result of the invention is to provide a structure of the rolled that provide sustainable conditions for cold massive forming geometrically-complex fasteners while providing high performance technology of plasticity. To achieve a technical result smelted steel in an electric furnace containing, wt.%: carbon 0,27-0,32, manganese between 0.30 to 0.65, silicon from 0.01 to 0.17, chrome 0,01-0,25, sulfur of 0,005 0,020, niobium 0,005-0,02, calcium 0,001-0,010, iron - rest when performing correlations: 12/S - Mn/0,03 20; Sa/S 0,065, conduct secondary treatment, continuous steel casting with stream protection with argon, hot rolling of continuously cast billets, which start at 900-950º C and end at 740-850 with the degree of deformation in the last passes of at least 20%, cold deformation calibration with deformation rate of 20-25% and spheroidizing annealing, including high-speed induction in microtechno temperature range holomediterranean and further cooling in a heat chamber at 100-200C. Microalloying of steel niobium inhibits the processes of recrystallization of steel at the temperature of steel 1000-S that allows you to provide fine-grained structure of austenite conducive to accelerating the spheroidizing steel. 2 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.

Known structural steel, containing (wt.%): carbon 0.17-0.20%, manganese 0.65-1.0%, si 0,17-0,37%, chromium 0.55-0.70%, vanadium of 0.05-0.08%, niobium 0,02-0,04%, the rest of the iron in the following ratio, wt.%: (SU 1703709 A, 07.01.1992,)

The most important requirement of rolled steel of low carbon steel for cold massive forming geometrically-complex 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. This steel from blending until ready rolled it takes a long processing, including the following operas the KSA mechanical properties, indicators of technological plasticity and low coefficient of strain hardening of the metal in the state of delivery currently successfully resolved through a number of techniques used at different stages of steel making.

The closest analogue to the claimed invention is a method of producing rolled low-carbon steel for cold massive forming geometrically-complex fasteners including steel smelting in the electric furnace, secondary treatment, continuous casting, hot rolling of continuously cast billets and cooling (EN 2156313 C1, C 21 D 8/02, 20.09.2000).

The basis of the invention is the task of the development of the steel of increased deformability and production way it rolled. The technical result of the invention is to provide a structure of the rolled guaranteeing the rational conditions of cold massive forming geometrically-complex fasteners.

To achieve a technical result in the known method of production of rolled low-carbon steel for cold massive forming geometrically-complex fasteners including steel smelting in switching-mode power is lawsut steel in the following ratio of components, wt.%:

Carbon 0,27-0,32

Manganese between 0.30 to 0.65

Silicon, from 0.01 to 0.17

Chrome 0,01-0,25

Sera of 0,005 0,020

Niobium 0,005-0,02

Calcium 0,001-0,010

Iron rest

when performing ratios 12/S - MP/0.03 20; Ca/S 0,065,

where C is carbon, Mn - manganese, CA - calcium, S - sulfur, hot rolling start at 900-950º C and end at 740-850 with the degree of deformation in the last passes of at least 20%, followed by cold deformation calibration with deformation rate of 20-25% and spheroidizing annealing by the speed of heat in the temperature range ACL+(10-30)followed by controlled cooling in the temperature range 650-C with a cooling rate of 0.5-1.0 C/min, and further cooling in a heat chamber at room temperature 100-200C.

Used deoxidizers and alloying elements with low nitrogen content. In continuous casting protect stream of metal from contact with air.

Given the combination of alloying elements (p. 1) allow to get in the proposed steel rod with a diameter up to 25 mm), accelerated after spheroidizing annealing homogeneous fine structure spheroidizing perlite with a favorable combination of characteristics is authorized steel to ensure a fine grain structure, that will increase as the level of its strength, and to provide a given level of ductility, as well as expand the interval of origenaly” steel. The upper limit of the content of carbon (0.32%) and niobium (0.02%) due to the need to ensure the required level of ductility of steel, and the bottom, respectively, 0.27% and 0.005% by providing the required strength level of the steel.

Manganese and chromium is used on the one hand, as a solid solution hardeners, on the other hand, as elements significantly increases the stability of the supercooled austenite. The upper levels of manganese - 0.65% and chromium - 0.25% 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 technological plasticity steel.

Silicon belongs to territooriumil elements. The lower limit for silicon - 0.01% caused by the deoxidation of steel. The silicon content higher than 0.17% will adversely affect the characteristics of ductility of steel.

Calcium is an element, modifying nonmetallic inclusions. The upper limit (0.010%) as in the case of sulfur due to the need to polycesta.

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.

Relations define the conditions ensure the specified characteristics of plasticity and proclaimeth cold steel at the drop-forging of geometrically-complex fasteners, use deoxidizing and alloying with low nitrogen content.

An example of the method

Smelting of low carbon steel of the following composition: carbon - 0.30%, manganese - 0.45%, silicon - 0.10%, chromium - 0.20%, sulfur - 0,011%, niobium - 0.012%, calcium - 0.001% is in the 150-ton electric arc furnaces using charge 100% of the 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 in the bucket for the production of particleboard. After the release was made metal blowing argon through the bottom vent block during which the steel raskalyaetsya aluminum. After that, the metal is fed to the Assembly of complex processing of steel (AKOS), nd the purge 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. 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 mixtures in the tundish and the mould, protective pipes, submersible glasses and a flow of argon. It also provides for obtaining a 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 € at a temperature of 740-850, when the deformation in the last passes of at least 20%. Followed by pickling hot-rolled steel in sulfuric acid solution (concentration of 180-200 g/l) at a temperature of 80C for 30 min, followed by the application of podmazochnaja coverage. Followed by cold deformation calibration with deformation of 20-25% and spheroidizing annealing, including high-speed induction in microtechno temperature range (ACl+10-30C) of cold metal followed by controlled cooling in the temperature range 650-S, with speeds of 1.0-1.5 C/min, and further cooled in a heat chamber at room temperature 100-200S, which reduces the duration of the process of spheroidizing 5-10 times.

The execution ratio of the alloying elements helped to provide the required level of ductility of steel directly in the hot rolled condition level =28%, and the level of cold precipitation sample with a diameter of 20 mm to 75% of the height.

when the manganese content is 0.45% of carbon - 0.30%

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

The introduction of the proposed method of production of rolled low-carbon steel with advanced technology of plasticity, providing recip is a multidisciplinary fasteners.

1. Method of production of rolled low-carbon steel for cold massive forming geometrically-complex fasteners including steel smelting in the electric furnace, secondary treatment, continuous casting, hot rolling of continuously cast billets and cooling, characterized in that the smelted steel in the following ratio, wt.%:

Carbon 0,27-0,32

Manganese between 0.30 to 0.65

Silicon, from 0.01 to 0.17

Chrome 0,01-0,25

Sera of 0,005 0,020

Niobium 0,005-0,02

Calcium 0,001-0,010

Iron Rest

when performing correlations

12/S - Mn/20 0,03;

Sa/S 0,065,

where C is carbon;

Mn - manganese;

CA - calcium;

S - sulfur

hot rolling start at 900-950º C and end at 740-850 with the degree of deformation in the last passes of at least 20%, followed by cold deformation calibration with deformation rate of 20-25% and spheroidizing annealing by the speed of heat in the temperature range ANDC1+(10-30), followed by controlled cooling in the temperature range 650-C with a cooling rate of 0.5-1.0 C/min, and further cooling in a heat chamber at room temperature 100-200C.

2. The method according to p. 1, tlicho p. 1, characterized in that during the continuous casting protect stream of metal from contact with air.

 

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