Method of production of 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 increased deformability characteristics of steel. For the technical implementation of the method includes steel smelting in the electric furnace, secondary treatment, casting molds with stream protection, hot rolling of the ingot and receiving the workpiece and subsequent rolling, controlled cooling and winding rolled in the riots. Smelted steel containing, wt.%: carbon 0.17-0.25, manganese 0.30-0.65, si 0.01-0.17, sulfur 0.005-0.020, vanadium 0.005-0.07, niobium 0.005-0.02, calcium 0.001-0.010. Moreover 0.466 V+8Nb0,22; . Microalloying of steel niobium inhibits the processes of recrystallization of the steel at a temperature of finish rolling 1000-S, allowing technolo-S, then rapidly cooled down to 750-850C and rolled to a deformation of at least 30%, followed by air cooling to 300C. 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.

Known structural steel containing, wt.%: carbon 0.18-0.22%, manganese 0.27-0.67%, si 0.17-0.37%, vanadium 0.05-0.10% niobium, 0.01-0.04%, the rest of the iron, in the following ratio, wt.%: 6V+8Nb 0.56 and 100000VNb28.0 (USSR author's certificate 1772208 from 30.10.1992, bull. NO. 40, WITH 22 38/12).

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 after cold forming processes. This steel from blending until ready rolled it takes a long processing, comprising the following operations: smelting, hot rolling, SLA 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 various stages of steel making.

Object of the invention is the development of steel increased stanoevska and method of manufacturing it rolled, providing directly into the mill stream (without additional spheroidizing annealing) rolled. The technical result of the invention is to provide a structure of the car, ensuring the rational conditions of cold massive forming geometrically-complex fasteners.

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, casting molds, hot rolling of the ingot and cooling (EN 2156311 C1, C 21 D 8/12, 20.09.2000).

To achieve a technical result in the known method of production of rolled low-carbon steel for cold massive forming fasteners including steel smelting in the electric furnace, secondary treatment, casting molds, hot rolling of the ingot and cooling, smelted steel in the following ratio comp is">Vanadium 0.005-0.07

Niobium 0.005-0.02

Calcium 0.001-0.010

Iron Rest

when performing correlations

0.46 6 V+8 Nb 0,22;

hot rolling finish at 1000-1050 C, rapidly cooled to 750-850 With and rolled with the degree of deformation of at least 30%, followed by air cooling. When casting molds stream of metal to protect argon.

Given the combination of alloying elements (p. 1) allow to get in the proposed carbon steel rod with a diameter up to 25 mm) directly in the delivery spheroidizing patterns that provide sustainable conditions for cold massive forming geometrically-complex parts and providing a favorable combination of strength and ductility.

Carbon and carbonitrides elements (vanadium, niobium) are entered into the composition of this steel to ensure a fine grain structure, which will increase as the level of its strength, and to provide a given level of ductility. While niobium and vanadium manage the processes in the austenitic region (determines the tendency to grain growth of austenite, stabilizes the structure during thermomechanical processing, increases those who also hardening steel at thermolysine. The upper limit of carbon content (0.25%), niobium (0.02%) and vanadium (0.07%) due to the need to ensure the required level of ductility of steel, and the bottom, respectively, 0.17%, 0.005% and 0.005% by providing the required strength level of the steel.

Manganese is used, on the one hand, as a solid solution hardener, on the other hand, as an element, substantially increasing the stability of the supercooled austenite. The upper levels of manganese 0.65% determined by the need to ensure the required level of ductility of steel, and the lower 0.30% by the need to provide an appropriate level of strength of the 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. 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.

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

The ratio of 0.46 6 V+8 Nb 0,22;

define the conditions ensure the specified characteristics of plasticity and proclaimeth cold steel at the drop-forging of geometrically-complex fasteners. The following are examples of implementation of the present invention, without excluding others, in the scope of the claims.

Smelting of low carbon steel of the following composition: carbon, 0.21%, manganese 0.45%, si 0.10%, chromium 0.20%, sulfur 0.011%, vanadium 0.03% niobium, 0.01%, calcium 0.001%, is produced in shaft furnace “Fuchs”. For guaranteed low nitrogen content developed special technology, including melt blending liquid cast iron up to 40% of the total volume of the mixture. Oxidative period provides a high rate of oxidation of carbon within 0,05-0,07%/min electric mode involves shutting off the furnace when the carbon content of 0.2-0.4 percent above the lower limit specified, dodavku the carbon produced without arcing. The temperature of the discharge from the furnace 1640-1680 C. Enter ferroalloys, steel treatment to remove non-metallic inclusions is made at the ladle furnace equipped with an electric heating system or hinotori. The temperature of the steel before casting on 60 With higher temperature overcome the CSOs nitrogen content in the casting is the protection of the jet of metal with argon through a special ring device. Heating of the ingots in the blooming shop is regenerative wells before the temperature started rolling 1250-1270 S. Rolling of ingots produced at the blooming mill (mill 1300) and then on a continuous billet mill on the billet cross section of 100 100 mm For removing the formed during heating of ingots de-carbonized layer of the workpiece are subjected to abrasive blasting." Then he made hot rolling the resulting workpiece on a wire mill 150 or small-section mill 250 in diameters from 5.5 to 23 mm in coils. To ensure the value of de-carbonized layer is not more than 1% of the diameter of the limited rate of billets from the furnace is not less than 100 t/h for 150 mill and at least 56 t/h to 250 mill. The onset temperature rolling of billets 1220-1240 for mill 250 and 1270-1290 for mill 150. Hot rolling of the rolled finish at a temperature of 1000-1050 With, then rapid cooling to 750-850, rolled with the degree of deformation of at least 30%, followed by air cooling to 300 C and the subsequent winding in the riots.

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 at obia - 0.01%

when the sulfur - 0.011%, calcium - 0.001%.

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

1. Method of production of rolled low-carbon steel for cold massive forming fasteners including steel smelting in the electric furnace, secondary treatment, casting molds, hot rolling of the ingot, cooling, 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

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 finish rolling at a temperature of 1m in air up to 300C.

2. The method according to p. 1, characterized in that the casting molds protect the metal stream with argon.

 

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FIELD: rolled tube production, namely method for making pilger mill mandrels from heat resistant steel for rolling hot rolled tubes.

SUBSTANCE: method for making mandrels used for rolling hot rolled tubes with large and mean diameters in range 273-550mm comprises steps of casting ingots of hear resistant steel; forging cylindrical solid or hollow blanks, roughly working of them, performing heat treatment and finishing mandrels at forming conicity 1 - 2 mm on length of their working portion while taking into account designed linear expansion coefficient during rolling process; determining diameter size by means of expression δ = dn - Δ/1 + α·t. One portion of mandrel from lock along length of half of working portion of mandrel is in the form of cone with diameters of cone bases determined form given expression and second portion is in the form of cylinder or truncated cone whose diameters are determined according to next expression

EFFECT: lowered lengthwise thickness difference of tubes.

3 cl, 1 dwg, 1 tbl

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