Method of manufacturing cold rolled strip

 

(57) Abstract:

The invention relates to metallurgy, in particular to the production of rolled steel, and can be used in the production of strip and sheet steel for stamping. The method comprises hot rolling, pickling, cold rolling emulsion, recrystallization annealing in Kolpakova kiln with multistage preheating and regulation of the composition of the protective environment. After cold rolling before annealing carried out in the shop exposure for 8-24 hours. Heating coils in the cover furnace after a cold start blowing podkupolnogo space protective environment within 2-3 hours. Annealing is performed with two intermediate extracts at a temperature of 580 and 650C. The removal of the products of sublimation and decomposition of the emulsion is produced continuously from the start of heating until the completion of the intermediate heating at a temperature of 650C by filing a protective environment containing 4-7% hydrogen and 93-96% nitrogen with a flow rate equal to the consumption of the protective environment during cold blowing. Carry out the infiltration of the protective environment of podkupolnogo space through sand shutter continuously from the beginning of the cold blowing until the process is complete cooling of the annealed coils under the muffle is to obtain high-quality cold-rolled strip, to reduce the consumption of fluids and increase the production of strips. table 1.

The invention relates to metallurgy, in particular to the production of rolled steel, and can be used in the production of strip steel for stamping parts of complex configuration under the paintwork.

The known method (U.S. patent No. 4475369, WV 9/00, WV 45/08, Appl. 18.09.82, publ. 09.10.84) production of purified cold-rolled strip, comprising cold rolling, the flow of emulsion used during rolling as a lubricant and having a concentration of 0.5-2.0%, removing from the surface of the strip grease and metal dust boot cold rolled strip after rolling in the annealing furnace, mixing the input flow of moisture from the gas atmosphere annealing furnace, consisting mainly of nitrogen and hydrogen, the regulation of the dew point temperature of the gas inside the annealing furnace in the range of 0-10S in order to reduce deposits of soot on the surface origemail strip.

The disadvantage of this method is that it cannot provide in the annealing process untrimmed metal, high surface quality of the strip. The supply of moisture in the annealing environment helps to reduce deposits of soot, but pravolinijsko annealing. The surface of the annealed strip is not that shiny and bright and matte and grey due to the presence of a thin layer of recovered oxides. When training band gets a lot of dispersed metallic dust that significantly impairs sanitary and hygienic working conditions, polluted rolls temper mills.

The band with the remains recovered oxides on the surface are not suitable for the manufacture of vehicle parts, refrigerator and other units that require a high quality paint finish.

In addition, the known method does not provide high stampability strip for parts of complex configuration.

Also known removal method of cooling and lubricating means (GDR patent No. 235907, Appl. 28.03.85, No. 2745304, publ. 21.05.86, F27D 7/06) from the surface of cold rolled products in the process of annealing in a protective atmosphere, whereby upload your batch of metal in the furnace, are blowing workspace protective atmosphere to reduce the oxygen concentration to a value of 1% and heat the metal to a temperature 280S, providing evaporation rolling lubricant. Then to the furnace is regulated amount of air so as to receive the opportunity to get clean and bright metal surface of the car because of the appearance of the finished annealed product with a refurbished product oxides, which greatly impairs the consumer properties of the metal.

The closest analogue is the way bands (Ed. mon. The USSR №1475942, C21D 9/46, Appl. 18.03.87, publ. 30.04.89) mainly from autopistol steel, including hot rolling, annealing and cold rolling emulsion, a two-step annealing up to 550-S, then to a temperature below ACmoreover, heating of the metal to the initial temperature of the two-stage annealing is carried out in two stages: the first - to 330-370C with irregular speed, then the second - rate controlled depending on the nitrogen content of aluminum in steel, concrete temperature regime of the end of hot rolling and the total reduction during cold rolling.

The disadvantage of the closest analogue is the inability to prevent soot deposition on the surface origemail strip, since the heating is to a temperature of 550-S perform very slowly with time at a temperature of 350-370C for 4.5 hours, not adjusting the removal of the products of sublimation and decomposition of the emulsion.

In addition, prolonged stay origimage metal at a temperature below the recrystallization temperature of the beginning (for steel 08U it 600C) Eney favorable for stamping parts of complex configuration. That is the nearest equivalent at the considerable cost of energy does not provide adequate quality origemail stripes on the surface and the complex parameters (mechanical properties, texture, recrystallization), providing the highest category hood.

Object of the present invention to provide a high-quality cold-rolled strip, i.e. with a high surface quality, with virtually no soot deposits, defect and a set of parameters that provide the highest category hoods for stamping intricate parts while reducing energy consumption and increasing production.

This object is achieved in that in the method of manufacturing a cold-rolled strip, including hot rolling, pickling, cold rolling emulsion, recrystallization annealing in Kolpakova kiln with multistage preheating and regulation of the composition of the protective environment to reduce contamination strip products of sublimation and decomposition of residues rolling emulsion, after cold rolling before recrystallization annealing carried out in the shop exposure for 8-24 hours, the heating coils in the cover furnace start poma intermediate exposures at temperatures of 580 and 650S, the removal of the products of sublimation and decomposition of the emulsion is produced continuously from the start of heating until the completion of the intermediate heating at a temperature of 650C by filing a protective environment containing 4-7% hydrogen and 93-96% nitrogen with a flow rate equal to the consumption of the protective environment during cold blowing, that you are carrying out infiltration of the protective environment of podkupolnogo space through sand shutter continuously from the beginning of the cold blowing until the process is complete cooling of the annealed coils under muffle the cover furnace.

The duration of the interim exposure less than 8 hours to evaporate a small part of the emulsion, resulting in increased rejection of metal defect “soot”, decreases the output of the metal of the 1st group surface finish.

The duration of the process extracts more than 24 hours increases the production cycle hire, there is a deficit production areas for storage of cold-rolled coils, restrains the production of cold rolling mill.

The duration of the cold blowing less than 2 hours does not provide a lower oxygen content under the muffle to 1%, as a result of deteriorating the quality of the car.

The duration of the cold blowing over x2">When the temperature of the first intermediate exposure less S slows down the process of heating coils, increases the probability of recrystallization texture, which does not provide the best stampability metal, thereby not providing the required quality of the strip.

At temperatures over S increases the temperature drop across the section of a roll, which leads to an increase in the heterogeneity of the mechanical properties of the annealed metal and the probability of joining adjacent turns of the coil due to the increased thermal stresses, which leads to deterioration of the surface due to defects “welding” and “fracture”.

When the temperature of the second intermediate exposure less than 650C decreasing the heating rate of the metal, which leads to performance degradation Kolpakova furnace, to reduce manufacturing strips.

When the temperature of the second intermediate exposure more 650S changed the dynamics of gas exchange processes to remove from a roll products of sublimation and decomposition of the emulsion, which increases the probability of deterioration of the metal.

The additional temperature, that is, the second intermediate exposure equal to 650C selected to ensure the stay origimage metal in tema recrystallization texture, contributing to high ratio (11-13) intensity component crystallographic texture, {111}/{100} and defect-free stamping parts very very difficult and very complex drawing.

The hydrogen content of the protective environment is selected in the range of 4-7%. When the hydrogen content of less than 4% decreases the performance of the annealing, and the possibility of oxidation of the metal, and consequently, low quality of the finished strip.

When the hydrogen content of more than 7% of the risk of formation of explosive mixtures under muffle the cover furnace, there is a “popping” kicks sand gate that leads to the suction of air under the muffle and the oxidation of the metal, deterioration of the quality of the strip surface.

Infiltration protective environment as carrier particles of soot in the gas phase under the muffle can reduce the soot formation on the metal surface, localizing this process on the particles of sand.

When the flow of shielding gas when infiltration through sand gate is less than 0.4 from the gas flow to the blowdown increases the sooting on trigema metal that does not provide the desired quality of the finished strip.

An example of the method

Concast slab thickness of 250 mm at a temperature of C, carried pickling hot-rolled strip for descaling, cold rolling to a thickness of 1.0 mm when the strip width 1250 mm with emulsion with a concentration of 1.5%. Strip after cold rolling was wound into a roll weighing 25 tons, was carried out by holding the shutter for 10 hours and was placed on the stand Kolpakova furnace for recrystallization annealing. Heating coils in cages with a weight of 100 tons was started after the cold blowing podkupolnogo space protective environment for 2.5 hours with a flow rate of 20 m3/hour.

Recrystallization annealing was carried out with two intermediate exposures at temperatures of 580 and 650S in the process of heating to a temperature of final extracts 690 or S, the removal of the products of sublimation and decomposition of the emulsion produced continuously from the start of heating until the completion of the intermediate heating at a temperature of 650C by filing a protective environment under muffle the cover furnace, containing 6% hydrogen and 94% nitrogen with a flow rate of 20 m3per hour, when it was carried out by the infiltration of the protective environment of podkupolnogo space through the sand gate stand the cover furnace continuously from the beginning of the cold blowing until the process is complete cooling of the annealed coils under the muffle. CSOs space, amounted to 20 hours.

Annealing the strip with a width of 1800 mm or more, in rolls weighing 30 tons and more than the duration of the hot purge podkupolnogo space is 30 hours, as the duration of exposure at temperatures of 580 and 650S as well as the time of heating to a temperature of 650C increases with increasing bandwidth.

In the process of hot purge podkupolnogo space to complete the extracts at a temperature of 650C was controlled by changing the content of N2, CO, CO2CH4. Upon completion of the heating process your batch rolls were cooled in a protective atmosphere under the muffle to a temperature of 120C, while continuously from the beginning of the cold blowing until the completion of cooling are infiltration protective environment through sand shutter with a flow rate of 0.4 from its consumption in hot and cold blow. Then the muffle was removed and the rolls were cooled in stock to a temperature of training, i.e., up to 40C. After completion of the forced cooling coils in the warehouse they had been trained, without finding chilled rolls in stock for more than 48 hours to avoid corrosion of the surface of the strip rolls and ensure you receive the strip surface, eligible high is not to determine the presence or absence of deposits of soot, the location of these deposits on the strip width, the length along the length of the strip. In addition, assessed the quality of the annealed metal volume output of the first group of surface finishing and analysis in his lower surface finish group (group III according to GOST 9045-93), or II grade defect “break”.

The use of the proposed method of production of cold-rolled strip obtained metal with higher consumer characteristics (see table).

As can be seen from the table, the proposed method can significantly improve the yield of metal of high surface finish (group I according to GOST 9045-93) and significantly reduce the rejection of metal defect “soot” and “kink” in the lower surface finish group.

The inventive method of manufacturing cold rolled strip provides improved product quality, increased production, reduced production costs, improved work orders, i.e., an increase in profit and profitability.

Method for the production of cold rolled strip, including hot rolling, pickling, cold rolling emulsion and recrystallization annealing in Kolpakova kiln with multistage preheating and regulirovanie implement interoperable exposure for 8-24 h, heating coils in the cover furnace after a cold start blowing podkupolnogo space protective environment within 2-3 h, the annealing is performed with two intermediate exposures at temperatures of 580 and 650S, the removal of the products of sublimation and decomposition of the emulsion is produced continuously from the start of heating until the completion of the intermediate heating at a temperature of 650C by filing a protective environment containing 4-7% hydrogen and 93-96% nitrogen, with a flow rate equal to the consumption of the protective environment during cold blowing, when this exercise infiltration of the protective environment of podkupolnogo space through sand shutter continuously from the beginning of the cold blowing until the process is complete cooling of the annealed coils under the muffle with the consumption of the protective environment of 0.4-0.5 from the consumption of the latter, while hot and cold blow.

 

Same patents:

The invention relates to metallurgy, and more specifically to the production of sheet steel, and may be used in the manufacture of hot-rolled sheets of low-carbon or low-carbon low-alloy steels intended for cold forming, deep drawing, extrusion and so on

The invention relates to the manufacture of steel strip for parts made deep hood or hood with thinning

The invention relates to the field of metallurgy, namely, rolling and heat treatment of steel, and can be used in the production of cold-rolled galvanized tape used to protect electrical cables

The invention relates to metallurgy, and more specifically to a technology of manufacturing a hot-rolled steel and cold-rolled sheet with high exhaust properties for cold forming

The invention relates to metallurgy, and more particularly to a technology for hot rolled galvanized strips of mild steel units continuous hot-dip galvanizing
The invention relates to ferrous metallurgy, namely rolling production

The invention relates to the field of metallurgy, in particular to the production of rolled steel, and can be used to obtain a strip steel for stamping parts of complex configuration

The invention relates to rolling production, more specifically to the technology of hot rolling strips of low-carbon steels, including tackle for subsequent cold rolling and high-speed annealing

The invention relates to rolling production and can be used to obtain strips for the cold steel autopistol

The invention relates to metallurgy, in particular to the production of rolled steel and can be used in the production of low carbon steel strip for cold forming and sheet of low hardness

The invention relates to metallurgy, and more specifically to the production of sheet steel, and may be used in the manufacture of hot-rolled sheets of low-carbon or low-carbon low-alloy steels intended for cold forming, deep drawing, extrusion and so on

The invention relates to a method of manufacturing a hot-rolled strip and sheet

The invention relates to a method for producing a high-strength steel strip and device for its implementation

The invention relates to the manufacture of steel strip for parts made deep hood or hood with thinning
The invention relates to the technology of production of cold-rolled strips of sverkhnizkochastotnye steels for the automotive industry, with a hardening effect during drying of the paint coating (EXT-effect)

The invention relates to the field of metallurgy, in particular to the production of the rolled strip from sverhskorostey steel (IF-steel) for further forging used in the automotive industry

The invention relates to the production of steel strip or sheet for deep drawing in the manufacture of cans

The invention relates to the field of metallurgy, namely, rolling and heat treatment of steel, and can be used in the production of cold-rolled galvanized tape used to protect electrical cables

The invention relates to sheets of very high-strength welded low-alloy steel and the method of production of steel sheets

FIELD: metallurgy, production of rolled steel.

SUBSTANCE: the invention is pertaining to the field of metallurgy, production of rolled steel, in particular, to methods of production of cold rolled steel sheets with the high drawing properties for a cold forming of details of cars bodies. The technical problem being solved by the invention consists in improvement of the quality of a cold rolled sheet steel. The method provides for hot rolling of continuously-cast low-carbon steel slabs, etching treatment, multirun cold rolling with total relative reduction of no less than 75 %, a recrystallization annealing in the following mode: a heating at an average speed of 70-80°C/h up to temperature of 490-510°C, a repeated heating at an average speed of 3-4 °C/h up to the intermediate temperatures of 540-560 °C/h and the final heating at an average speed of 50 - 55°C/h up to the annealing temperature of 700-720 °C, at which the steel rolls are kept for 12-18 h. Upon termination of keeping the rolls at the annealing temperature they are cooled at the rate of 19-21 °C/h up to the temperatures not exceeding 690 °C. At that the continuously cast low-carbon steel slabs have the following chemical composition (in mass %): 0.025-0.050 - carbon, 0.003-0.010 - silicon, 0.12-0.19 - manganese, 0.02-0.05 - aluminum, no more than 0,011 - nitrogen, the rest - iron and impurities.

EFFECT: the invention ensures improvement of the quality of a cold rolled sheet steel.

3 cl, 5 ex, 3 tbl

Up!