CN117737396A - Flexible cold rolling post-treatment production line suitable for producing various ultra-high strength strip steels - Google Patents
Flexible cold rolling post-treatment production line suitable for producing various ultra-high strength strip steels Download PDFInfo
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Abstract
A flexible cold rolling post-treatment production line suitable for producing various ultra-high strength strip steels comprises the following stations: uncoiling, welding, inlet looping, cleaning, central continuous post-treatment, intermediate looping, flattening, outlet looping, finishing and coiling; the central continuous post-treatment station sequentially comprises a jet direct-fire preheating section, a direct-fire heating section, a radiant tube heating section, an optional transverse magnetic induction heating section or a muffle section, a radiant tube soaking section, a slow cooling section, a rapid cooling section and a reheating section; the transverse magnetic induction heating sections or the muffle furnace sections are arranged in parallel; two process paths are arranged from the reheating section: one path is provided with a moving channel, an overaging section and a final air-jet cooling section to a final water-cooling section; the other path is provided with a furnace nose section, a zinc pot section, an air knife section, an alloying heating section, an alloying soaking section and a cooling section after plating to a final water cooling section; the final water cooling section is provided with an optional acid washing section and/or flash plating section, so that the flexible manufacturing of the high-strength strip steel is realized, and the application prospect is particularly broad.
Description
Technical Field
The invention relates to the technical field of strip steel cold rolling post-treatment, in particular to a flexible cold rolling post-treatment production line suitable for producing various ultra-high strength strip steels.
Background
In recent years, the use amount of light non-steel materials such as aluminum alloy, magnesium alloy and carbon fiber composite materials in high-end brands of automobiles has been increasing year by year. The automobile emission regulations in China are also becoming strict, new energy automobiles are rapidly developed, and the application of aluminum alloy and composite materials in national autonomous brands is also beginning to increase. Against this background, steel enterprises are struggling to develop and produce high-strength steel and ultra-high-strength steel automotive sheet products meeting the light-weight requirements of automobiles to cope with competition for non-steel materials. The ultrahigh-strength steel can absorb higher collision energy, improve the safety of the automobile, has higher static strength and fatigue strength, and can reduce the materials of automobile parts, thereby realizing light weight. Namely, the ultra-high strength steel can meet the requirements of light weight and safety, the application technology is relatively mature, and the ultra-high strength steel is still the preferred material for the development of automobiles in the future at present. Accordingly, demands for high-strength steel strips, particularly ultra-high-strength steel strips, including continuously annealed cold-rolled steel strips, hot-dip galvanized steel strips (hereinafter abbreviated as GI) and galvannealed steel strips (hereinafter abbreviated as GA), have been increasing year by year.
Conventional strip steel processing lines typically include, in addition to the various looper stations, the following stations: uncoiling, welding, cleaning, central continuous post-treatment, flattening, finishing and coiling, wherein a withdrawal and straightening station is further arranged between a flattening station and a finishing station on some treatment lines, a post-treatment station is arranged between the flattening station and the finishing station on some treatment lines, and a withdrawal and straightening station and a post-treatment station are simultaneously arranged between the flattening station and the finishing station on other treatment lines.
The above-mentioned central continuous post-treatment station generally comprises the equipment of a general preheating section-heating section-soaking section-slow cooling section-fast cooling section-Overaging (OA) section-air-jet cooling section and final water-cooling section when producing continuously annealed cold rolled products, as shown in fig. 1.
And a reheating section is arranged between the quick cooling section and the overaging section of some treatment lines, and an acid washing section and a reheating section are simultaneously arranged between the quick cooling section and the overaging section of some units. In the production of GI products, the central continuous post-treatment station typically comprises in sequence the equipment of a common preheating section-heating section-soaking section-slow cooling section-fast cooling section-balanced heat preservation section-furnace nose section-zinc pot section-air knife section-post-plating cooling section-final water cooling section, as shown in fig. 2.
And a reheating section is arranged between the quick cooling section and the balanced heat preservation section in some GI processing lines, and an acid washing section and a reheating section are simultaneously arranged between the quick cooling section and the balanced heat preservation section in some units. Some treatment lines have a movable post-plating quench section disposed within 10 meters above the air knife between the air knife section and a stationary post-plating quench section (typically in the upper half of the APC tower). In the production of GA products, the central continuous post-treatment station typically comprises in sequence the equipment of a common preheating section-heating section-soaking section-slow cooling section-fast cooling section-balanced heat-preserving section-furnace nose section-zinc pot section-air knife section-alloying heating section-alloying soaking section-stationary post-plating cooling section and final water cooling section, as shown in fig. 3.
And a reheating section is arranged between the quick cooling section and the balanced heat preservation section in some processing lines, and an acid washing section and a reheating section are simultaneously arranged between the quick cooling section and the balanced heat preservation section in some units. The movable channel section is also arranged above the air knife section, so that the switching of two or three products is realized, wherein the movable channel section (only cold-rolled product is produced), the quick cooling section (only GI product is produced) after movable plating and the alloying heating section (only GA product is produced) are arranged in parallel, and strip steel is usually cut off for product switching. And the production line for producing the GI products and the GA products adopts parallel arrangement of a quick cooling section (only the GI products are put into use) and an alloying heating section (only the GA products are put into use) after mobile plating, so that the switching of the two products is realized.
For the common preheating section and the heating section, a common mode is to adopt a direct fire heating section, preferably clean natural gas is adopted for direct fire heating, unclean combustion waste gas is prevented from polluting the surface of the strip steel, the strip steel is directly preheated by the direct fire combustion waste gas, the temperature of the strip steel is generally lower than 750 ℃ after the direct fire heating, and the strip steel is further heated by a radiant tube and can be heated to about 850 ℃. Namely: directly preheating strip steel by using combustion waste gas of a direct-fired furnace, heating by using direct fire, heating by using a radiant tube, and then carrying out soaking and other treatments. The prior art has the following defects:
1) The exhaust gas emission temperature of direct-fire combustion after preheating the strip steel is still relatively high, and is usually over 800 ℃, sometimes over 850 ℃, and when the exhaust gas emission temperature exceeds 850 ℃, cold air is usually doped to control the exhaust gas emission temperature to 850 ℃ or below so as to carry out secondary off-line utilization. The higher the exhaust gas temperature means more thermal energy is lost. According to the method, the primary online utilization rate of heat energy is low, and steam or hot water generated by secondary offline utilization cannot be completely consumed in the unit, so that the energy balance of the area is difficult;
2) Because the direct-fired waste gas directly contacts the strip steel and the contact time is longer, in addition, excessive fuel gas in the direct-fired waste gas needs to be subjected to secondary combustion in a preheating section, the secondary combustion flame is often an oxidizing flame, the improvement of the preheating temperature of the strip steel is necessarily limited, otherwise, an excessively thick oxide layer is easily formed on the surface of the strip steel, the surface quality problem is caused, and the preheating temperature of the strip steel can only be preheated to about 250 ℃ generally, and the preheating effect is poor;
3) The direct fire heating section has limited heating capacity and cannot be too high, the strip steel can be heated to 750 ℃ or below, the strip steel is easy to be severely oxidized after the heating temperature is further increased, and the temperature uniformity along the width direction of the strip steel is relatively poor;
4) The traditional process generally adopts a radiant tube for further heating when the strip steel is annealed at the temperature higher than 750 ℃, and because the thermal inertia of a radiant tube heating furnace is large, when the thickness specification and the annealing target temperature change greatly, the temperature adjustment of the strip steel is slow, the temperature control precision is poor, the method is very unfavorable for producing ultra-high strength steel, and the quality loss is large;
5) The radiation tube is used for heating at the temperature above 750 ℃, particularly above 850 ℃, the heating efficiency is low, the heating speed is low, and the higher the heating temperature is, the lower the heat efficiency and the heating speed are, the lower the primary direct utilization efficiency of corresponding energy is;
6) The upper limit of the annealing temperature is limited, the temperature of the annealed strip steel is not more than 870 ℃ generally, if the process needs to anneal the strip steel at the ultra-high temperature of more than 870 ℃, the annealing cannot be realized, namely the product variety is limited, and the ultra-high temperature annealed ultra-high strength steel cannot be produced.
Disclosure of Invention
The invention aims to design a flexible cold rolling post-treatment production line suitable for producing various ultra-high strength strip steels, which can realize the following purposes: 1) The temperature of the strip steel can be quickly preheated to at least 350 ℃ by fully utilizing the waste heat of the direct-fired combustion waste gas; 2) The direct-fired combustion waste gas is prevented from directly contacting the strip steel in the preheating furnace for a long time, and an excessively thick oxide layer is prevented from being generated on the surface of the strip steel; 3) The rapid heating is realized during the ultra-high temperature period, so that the heat energy utilization rate is improved; 4) The rapid adjustment of the annealing temperature of the strip steel can be realized due to the remarkable reduction of the heating furnace and the reduction of the thermal inertia of the furnace; 5) The heating section of the annealing furnace can be obviously miniaturized and highly-efficient due to rapid heating, so that energy conservation and emission reduction can be realized, and the occupied area can be reduced; 6) Can realize the ultra-high temperature annealing treatment at about 930 ℃; 7) The flexible high-strength steel special production line can flexibly produce various products such as cold rolling, hot dip pure zinc (GI), alloying hot dip Galvanizing (GA), cold rolling surface nickel plating or zinc plating, and the like, so the production line can better meet market demands; 8) The platability of the ultra-high strength steel product can be greatly improved, so that the surface quality of the ultra-high strength hot dip product can also be obviously improved; 9) The application of the rapid heating, rapid cooling and rapid heat treatment process technology can adopt lower alloy components to produce various advanced high-strength steel products with higher strength grades, not only can reduce the production cost of high-strength steel, but also can improve the mechanical properties and subsequent processing properties (such as welding properties) of various super-high-strength steel products, and remarkably improve the market competitiveness of the high-strength steel products.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a flexible cold rolling post-treatment production line suitable for producing various high-strength strip steels comprises the following stations: uncoiling, welding, inlet looping, cleaning, central continuous post-treatment, intermediate looping, flattening, outlet looping, finishing and coiling; wherein,
the central continuous post-treatment station sequentially comprises a jet direct-fire preheating section, a direct-fire heating section, a radiant tube heating section, an optional transverse magnetic induction heating section or a muffle section, a radiant tube soaking section, a slow cooling section, a rapid cooling section and a reheating section; the transverse magnetic induction heating sections or the muffle furnace sections are arranged in parallel;
two process paths are arranged from the reheating section:
one path is provided with a moving channel, an overaging section and a final air-jet cooling section to a final water-cooling section;
the other path is provided with a furnace nose section, a zinc pot section, an air knife section, an alloying heating section, an alloying soaking section and a cooling section after plating to a final water cooling section;
an optional acid washing section and/or flash plating section are arranged behind the final water cooling section;
the direct-fire heating section adopts natural gas or liquefied petroleum gas combustion;
the injection direct-fire preheating section utilizes waste gas generated by combustion of the direct-fire heating section to exchange heat in the furnace to heat the recycled nitrogen-hydrogen protective gas, and then the nitrogen-hydrogen protective gas is injected to the upper surface and the lower surface of the strip steel to realize forced convection heat exchange;
The direct-fire heating section, the radiant tube heating section, the transverse magnetic induction heating section and the muffle furnace section which are arranged in parallel are arranged in series;
the rapid cooling section comprises a high-hydrogen cooling section, an aerosol cooling section or/and a water quenching cooling section.
Preferably, an optional withdrawal and straightening station and/or a surface post-treatment station such as passivation or fingerprint resistance is arranged between the flattening station and the outlet looper station, and withdrawal and/or surface post-treatment can be carried out on the strip steel.
Preferably, the transverse magnetic induction heating section and the muffle furnace section are arranged in parallel and between the radiant tube heating section and the radiant tube soaking section, and the switching between the transverse magnetic induction heating section and the muffle furnace section is realized by cutting off the strip steel and threading again; the muffle furnace section is provided with sealing devices at the front and back, and is also provided with an atmosphere adjusting device for independently adjusting and controlling the hydrogen content, the oxygen content and the dew point in the muffle furnace section.
Preferably, a balanced heat preservation section is arranged between the reheating section and the furnace nose section, and hot galvanizing is performed after heat preservation treatment is performed on the strip steel.
Preferably, a secondary reheating section is arranged after the balanced heat preservation section, and the balanced heat preservation strip steel is subjected to secondary reheating and then hot galvanizing or overaging treatment.
Preferably, a movable post-plating quick cooling section is arranged between the air knife section and the post-plating cooling section, and the movable post-plating quick cooling section is arranged in parallel with alloying heating equipment, so that the quick cooling of the strip steel after the hot-dip pure zinc high-strength steel product is plated is realized; preferably, a mobile plating post-fast cooling section is arranged within a range of 10 meters above the air knife section.
Preferably, a pickling section is arranged between the rapid cooling section and the reheating section, and comprises a pickling unit, a hot water scrubbing unit, a hot water rinsing unit and a hot air drying unit, so that the surface of the strip steel is pickled. Can be used for removing the oxide layer on the surface of the strip steel after aerosol cooling or/and water quenching cooling, and can also improve the platability of high-strength strip steel, especially ultra-high-strength strip steel for hot dip galvanizing pure zinc or alloyed hot dip galvanizing products.
Preferably, after the pickling section after the rapid cooling section, a flash iron plating section or a flash nickel plating section is arranged, and then reheating treatment is carried out, so that the platability of the ultra-high-strength strip steel can be further improved.
Preferably, the soaking section of the radiant tube adopts an air jet and radiant composite heating device to realize rapid adjustment of the soaking temperature of the strip steel.
The flexible cold rolling post-treatment production line suitable for producing various high-strength strip steel adopts spraying direct fire preheating section and adopts high hydrogen cooling or aerosol cooling or/and water quenching cooling to carry out rapid cooling treatment, then reheating and then galvanization or overaging treatment; the furnace nose section and the moving channel section are arranged in parallel, strip steel passes through the furnace nose section backwards and is used for producing hot-dip pure zinc or alloyed hot dip galvanized products, and strip steel passes through the moving channel section and is used for producing cold-rolled or flash-plated products; in addition, an acid washing section is arranged after the final water cooling section, and a flash plating section is arranged next, so that the strip steel can be selected to pass through the acid washing section to produce cold-rolled acid washing products, can bypass the acid washing section to produce cold-rolled annealed products, and can also be selected to enter the flash plating section after being acid washed to produce flash plating products such as flash nickel plating or flash zinc plating. The production line has at least three or more than three selectable process paths, and can realize the production of five different types of high-strength steel including cold rolling annealing, acid washing, flash plating, hot dip pure zinc and alloying hot dip galvanizing.
The invention also provides a jet direct-fire type preheating device, which comprises: a direct fire furnace and a preheating furnace; wherein,
the direct fire includes:
a furnace shell, the upper end and the lower end of which are respectively provided with a furnace top roller chamber and a furnace bottom roller chamber; steering rollers are respectively arranged in the furnace top roller chamber and the furnace bottom roller chamber; a plurality of direct-fire heating areas are arranged in the furnace shell along the height direction, and a plurality of direct-fire burners are arranged in the direct-fire heating areas; the side wall of the upper part of the furnace shell is provided with at least two through holes which are symmetrically arranged left and right;
the preheating furnace comprises:
the side wall of the upper part of the furnace body is provided with at least two connecting holes which are symmetrically arranged left and right and are respectively connected with the through holes on the upper part of the furnace shell of the direct-fired furnace through communicating pipes; the top end of the furnace body is provided with a furnace throat which corresponds to the furnace top roller chamber of the direct furnace and is used for the strip steel to pass through; the bottom of the furnace body is provided with a strip steel inlet, a corresponding sealing device and a corresponding steering roller; an upper partition plate with a through hole is arranged at the upper part in the furnace body to form an upper gas collection chamber of the direct-fire waste gas; a direct-fire combustion waste gas secondary combustion chamber is arranged below the upper gas collection chamber of the direct-fire waste gas, and at least one open-fire burner is arranged in the direct-fire combustion waste gas secondary combustion chamber; preferably, a combustion waste gas thermometer is further arranged in the direct-fired combustion waste gas secondary combustion chamber; a lower partition plate with a penetrating hole is arranged at the lower part in the furnace body to form a lower straight fire waste gas collecting chamber, and the lower straight fire waste gas collecting chamber is connected with a waste gas fan through a waste gas discharge pipeline; a control valve is arranged on the waste gas discharge pipeline;
The heat exchange and air injection bellows units are arranged on two sides below the direct-fired combustion waste gas secondary combustion chamber in the furnace body along the height direction of the furnace body, and a strip penetrating channel for strip steel to pass through is formed in the middle of the heat exchange and air injection bellows units; each heat exchange and air injection bellows unit comprises,
the air box body is vertically provided with a plurality of heat exchange tubes, and a plurality of nozzles are arranged on one side surface of the air box body, which is opposite to the threading channel; an exhaust gas secondary mixing chamber communicated with the heat exchange tube is arranged between the upper and lower bellows bodies; introducing nitrogen and hydrogen protective gas into the bellows body;
the port of the inlet pipeline of the circulating fan is arranged in the threading channel, and the port of the outlet pipeline of the circulating fan is positioned in the bellows body;
the sealing devices are respectively arranged at the upper and lower ports of the threading channel and the threading holes of the upper and lower partition plates; preferably, the sealing device is of a nitrogen sealing structure, a nitrogen sealing chamber is adopted, and a nitrogen injection pipeline is arranged on the sealing device.
In the production process, high-temperature combustion waste gas generated by direct fire combustion of a direct fire furnace enters a preheating furnace through a communicating pipe, a plurality of heat exchange and air injection bellows units which are sequentially arranged up and down are arranged in the preheating furnace, a heat exchange pipeline (high-temperature combustion waste gas tube side and protective gas tube side) of the heat exchange and air injection bellows units heats nitrogen-hydrogen mixed gas in the bellows body, high Wen Danqing mixed gas is blown to two sides of the strip steel through high-speed nozzles opposite to two sides of the strip steel, the strip steel is rapidly heated, the ejected high Wen Danqing mixed gas exchanges heat with low-temperature strip steel, the mixed gas is subjected to heat exchange again from circulating fans which are arranged close to two sides of the strip steel after the temperature of the mixed gas is reduced, the temperature of the nitrogen-hydrogen mixed gas is raised again, and then the nitrogen-hydrogen mixed gas is sprayed to two sides of the strip steel from the inside of the air injection bellows unit again, and the strip steel is circulated and reciprocated in this way.
In the preheating device:
the preheating device is characterized in that a heat exchange and air injection bellows unit and a direct-fire combustion waste gas secondary combustion chamber are arranged, the heat exchange and air injection bellows unit adopts a heat exchange pipeline (the heat exchanger is not arranged outside the furnace), the waste gas which is combusted again in the direct-fire combustion waste gas secondary combustion chamber heats nitrogen and hydrogen protective gas circularly utilized in the bellows, and the heated nitrogen and hydrogen protective gas is sprayed to the upper surface and the lower surface of the strip steel at a high speed under the action of a circulating fan for forced convection heat exchange, so that the strip steel is preheated rapidly and efficiently.
And an open flame burner is further arranged in the direct-fire combustion waste gas secondary combustion chamber and is used for carrying out oxygen-enriched secondary combustion on insufficiently combusted fuel gas in the direct-fire combustion waste gas secondary combustion chamber, and the burning flame cannot contact strip steel.
An exhaust gas secondary mixing chamber communicated with the heat exchange tube is arranged between the upper and lower bellows bodies, and the exhaust gas temperature is homogenized in the exhaust gas secondary mixing chamber and then enters the downstream bellows body.
The sealing device is of a nitrogen sealing structure and is provided with a nitrogen sealing chamber, a nitrogen injection pipeline opening is arranged in the nitrogen sealing chamber, sealing nitrogen is introduced into the nitrogen sealing chamber to maintain relatively high pressure, a large amount of direct-fire combustion waste gas is prevented from entering a strip penetrating channel in the furnace for heat exchange and the air injection bellows unit, and accordingly the surface of strip steel can be prevented from being excessively oxidized by the direct-fire combustion waste gas.
The strip steel inlet of the preheating furnace is provided with a sealing device, and the inside of the sealing device is also provided with a gas injection port for injecting a small amount of sealing nitrogen or air, so that the sealing device has the function of preventing the direct-fired combustion waste gas from overflowing out of the furnace.
The invention relates to a jet-radiation composite heating device, which comprises:
the furnace body is internally provided with a composite heating body along the height direction; the composite heating body comprises an insulation box body, wherein an insulation material is arranged on the inner wall of the shell; a mounting hole is arranged in the center of one side surface of the heat preservation box body;
the circulating fan is arranged at the mounting hole of the heat insulation box body, the air suction inlet of the circulating fan corresponds to the axis of the mounting hole, and the air outlet is arranged on the side surface of the shell;
the buffer cavity is arranged in the insulation box body at a position corresponding to the air suction opening of the circulating fan, the back surface of the buffer cavity is provided with a hot air outlet corresponding to the air suction opening of the circulating fan, and the front surface of the buffer cavity is provided with a hot air inlet; preferably, the buffer cavity and the high-temperature air injection bellows are of an integrated structure;
the two high-temperature air jet bellows are vertically and symmetrically arranged at two sides of a hot air inlet at the front side of the buffer cavity in the heat insulation box body to form a strip penetrating channel for strip steel to pass through; a plurality of rows of jet nozzles are arranged on one side surface of the two high-temperature jet bellows at two sides of the threading channel at intervals along the height direction, and a gap is arranged between n rows of jet nozzles, wherein n is more than or equal to 1; n=1, the radiant tubes are arranged in parallel above or below the row of jet nozzles; preferably, the diameter of the jet nozzle is 1/10-1/5 of the distance from the jet nozzle to the strip steel; more preferably, the jet nozzle adopts a round hole structure;
The radiant tubes are symmetrically arranged in the two high-temperature air injection bellows and comprise a connecting tube section for connecting a burner, a radiant tube section bent and extended from one end of the connecting tube section and a heat exchange tube section formed by extending and bending from one end of the radiant tube section; the radiant tube section corresponds to gaps arranged between n rows of jet nozzles in the high-temperature jet bellows, so as to form a jet-radiation alternating structure; preferably, the radiant tube section, the connecting tube section and the heat exchange tube section of the radiant tube are arranged in parallel.
The soaking device can adopt an air-jet radiation composite heating device, and the device can organically combine a high-speed high-temperature air-jet technology and a radiant tube heating technology, so that the technical advantages of the high-speed high-temperature air-jet heating technology and the radiant tube heating technology are fully exerted. The structure of the radiant tube is optimally designed, the radiant tube is arranged in the high-speed high-temperature jet air box, heat generated by burning gas of the radiant tube is rapidly transferred to the strip steel through two modes of high-speed high-temperature jet and radiation, the rapid heating of the strip steel is realized, the highest average heating speed of the strip steel of 1mm is not lower than 40 ℃/s, the length of a heating furnace can be greatly shortened, the heating section of a unit with 30 ten thousand tons per year output is about 2 pass, and the thermal inertia of a furnace body is reduced;
Second, heat generated by the fuel gas is transferred to the circulating gas (N 2 +H 2 ) The heat-conducting material is taken away, so that the exhaust temperature of the radiant tube can be reduced, the exhaust temperature of the radiant tube can be reduced by about 100 ℃ under the same condition, the heat efficiency of the radiant tube is improved by about 5%, the average working temperature of the radiant tube can be reduced, and the service life of the radiant tube is prolonged;
and the temperature of the heated circulating gas is uniform, so that the temperature distribution of the strip steel in the width direction in the heating process is uniform, and the temperature distribution of the strip steel in the width direction in the actual heating process is controlled to be +/-5 ℃ according to the uniformity of the strip steel in the width direction, thereby realizing the stable operation of the unit. The high-speed air injection and radiation composite heating technology can obviously improve the productivity of the existing unit and solve the problem of insufficient heating capacity on the production line.
The radiant tube of the jet-radiation composite heating device has the functions of combustion radiation (namely, the high-temperature section of the radiant tube between two rows of nozzles) and a heat exchanger, and is used for heating circulating gas, so that the heat of the combustion gas in the radiant tube can be rapidly transferred to strip steel through forced heat exchange, the rapid heating of the strip steel is realized, the length of a heating furnace can be greatly shortened, and the thermal inertia of a large-scale vertical continuous annealing furnace body is reduced.
The invention is different from the traditional process in that:
1) The invention has at least three or more than three selectable process paths;
2) The invention can realize the production of five different types of high-strength steel, especially super-high-strength steel, including cold rolling annealing, acid washing, flash plating, hot plating pure zinc and alloying hot galvanizing;
3) The five different types of ultra-high strength steel can be subjected to surface post-treatment such as withdrawal and straightening or/and passivation or fingerprint resistance;
4) The invention is provided with the secondary reheating section, realizes the twice lifting of the temperature of the strip steel before hot galvanizing or overaging treatment, can realize the rapid cooling of third-generation high-strength steel (QP steel) products to lower temperature, then rapidly heats the products to higher temperature for long-time carbon redistribution treatment, and rapidly re-heats the products to the hot galvanizing zinc-entering pot temperature for the second time after the treatment is finished, and performs galvanization treatment;
5) The invention changes the common preheating section into the injection direct fire preheating section, more precisely the high-temperature nitrogen-hydrogen protective gas injection direct fire preheating section, which is one of the novelty and creativity of the invention, and the remarkable characteristics of the invention are that the invention is different from the common preheating section:
(1) the method has the advantages that compared with the traditional preheating method, the heat loss of a furnace shell and a protective gas channel is obviously reduced, the waste heat utilization of combustion waste gas is more complete, the heating efficiency is higher, and the heating rate is faster;
(2) In the preheating furnace, the direct-fire combustion waste gas passes through a heat exchanger chamber of the preheating furnace, and the direct-fire combustion waste gas and the heat exchanger in the heat exchanger chamber perform sufficient heat exchange in the passing process to heat the nitrogen-hydrogen protective gas, so that the direct-fire combustion waste gas in the preheating furnace is not always in direct contact with strip steel (only in short time in a high-temperature section and the waste gas belongs to a reducing atmosphere or a micro-oxidation atmosphere), thereby avoiding the surface peroxidation of the strip steel;
(3) the insufficiently combusted fuel gas in the directly-fired waste gas is subjected to oxygen-enriched secondary combustion in a semi-sealing unit at the top of the jet preheating furnace, but the burning flame does not contact strip steel, so that the surface peroxidation of the strip steel is effectively avoided;
(4) the preheating temperature of the strip steel is higher, and the high-temperature nitrogen-hydrogen protective gas injection direct-fire preheating heat exchange coefficient is high, so that the temperature of the preheated strip steel at least reaches 350 ℃ and above, and is at least 100 ℃ higher than that of the common preheating strip steel;
(5) the temperature of the direct-fire combustion exhaust gas from the preheating furnace is usually far lower than 750 ℃ (if the number of the high-speed jet preheating units is enough, the direct discharge below 200 ℃ can be achieved), and the secondary utilization of cold air outside the furnace or secondary utilization is not needed at all. The jet direct fire preheating section is one of the core technologies of the invention.
6) According to the invention, the transverse magnetic induction heating section device and the muffle furnace section are arranged between the radiant tube heating section and the radiant tube soaking section, and are arranged in parallel, and the switching between the transverse magnetic induction heating section and the muffle furnace section is realized by cutting off strip steel and re-threading. The muffle furnace section is provided with sealing devices, and is also provided with an atmosphere adjusting device, so that the hydrogen content, the oxygen content and the dew point in the muffle furnace section can be independently adjusted and controlled. The novel and creative embodiment of the invention is realized by simultaneously using the high-efficiency high-speed jet preheating section and the transverse magnetic induction heating section between the radiant tube heating section and the radiant tube soaking section.
The transverse magnetic induction heating section is arranged between the radiant tube heating section and the radiant tube soaking section, and has the beneficial effects that:
(1) the rapid adjustment of the temperature of the strip steel can be realized, which is very critical to the production of high-strength steel, especially ultra-high-strength steel, and the loss of the strip steel can be reduced;
(2) the strip steel can be heated to a higher temperature, and the prior engineering realizes the heat treatment of heating to about 930 ℃ through radiant tube heating and transverse magnetic induction heater;
(3) the soaking is matched with a radiant tube, the temperature uniformity of the strip steel after soaking is good, and the temperature uniformity along the width direction of the strip steel can be controlled within +/-5 ℃;
(4) The improvement of the heating rate can refine the grain structure to improve the strong plasticity of the material, and is particularly beneficial to the performance improvement and the cost reduction of high-strength steel and ultra-high-strength steel products.
The invention has the beneficial effects that:
1) The primary utilization rate of the waste heat of the directly heated combustion waste gas is high, and the temperature of the strip steel can be preheated to at least 350 ℃;
2) The direct-fired combustion waste gas is prevented from directly contacting the strip steel in the preheating furnace for a long time, and an excessively thick oxide layer can be prevented from being generated on the surface of the strip steel;
3) The secondary ignition combustion flame of excessive fuel gas in the direct-fired waste gas can not contact the strip steel, and the generation of an excessively thick oxide layer on the surface of the strip steel can be avoided;
4) The strip steel can be economically and rapidly heated to about 930 ℃ when transverse magnetic induction heating is used, so that ultra-high temperature annealing can be realized, and various novel ultra-high strength steels can be produced;
5) The strip steel after the jet-air radiation composite soaking has good temperature uniformity, and the temperature uniformity along the width direction of the strip steel can be controlled within +/-5 ℃;
6) The soaking section adopts an air jet radiation composite heating device to realize rapid adjustment of the soaking temperature of the strip steel;
7) The same production line can be used for producing continuous annealing cold rolled DP steel, MS steel, TRIP steel, QP steel, hot galvanized DP steel, TRIP steel, QP steel and other super-high-strength steel, and various high-strength steel products produced by adopting the rapid heat treatment process have better performance and lower cost;
8) The martensite ultra-high strength steel with the strength up to 1500MPa can be produced by adopting water mist cooling and acid washing, the surface quality and the plate shape quality are high, the platability of the strip steel during hot galvanizing is good, and the plating quality is excellent;
9) According to the invention, through the adjustment of the air-fuel ratio of the direct-fired furnace, a pre-oxidation reduction process can be realized, and the platability of the ultra-high-strength steel is better; the invention can realize the production of five different types of high-strength steel, especially super-high-strength steel, such as cold rolling annealing, acid washing, flash plating, hot plating pure zinc and alloying hot galvanizing.
Drawings
FIG. 1 is a schematic diagram of a station arrangement of a conventional continuous annealing production line;
FIG. 2 is a station layout of a conventional hot dip Galvanizing (GI) line;
FIG. 3 is a station layout of a conventional Galvannealed (GA) production line;
FIG. 4 is a layout of the production line of embodiment 1 of the present invention;
FIG. 5 is a layout of the production line in accordance with embodiment 2 of the present invention;
FIG. 6 is a station layout of the production line of example 3 of the present invention;
FIG. 7 is a station layout of the production line of example 4 of the present invention;
FIG. 8 is a layout of the production line of embodiment 5 of the present invention;
FIG. 9 is a layout of the production line of embodiment 6 of the present invention;
FIG. 10 is a schematic view of an embodiment of a jet direct-fired preheating device according to the present invention;
FIG. 11 is a schematic view of a preheating furnace in an embodiment of the jet direct-fired preheating device according to the present invention;
FIG. 12 is a schematic view of an embodiment of a jet-beam radiation composite heating apparatus according to the present invention 1;
FIG. 13 is a schematic view of an embodiment of a jet-beam radiation composite heating apparatus according to the present invention 2;
fig. 14 is a schematic structural diagram of a composite heating body in an embodiment of the jet radiation composite heating device according to the present invention;
FIG. 15 is a partial perspective view of a high temperature jet bellows in an embodiment of a jet radiation complex heating device according to the present invention;
fig. 16 is a perspective view of a radiant tube in an embodiment of the jet radiant composite heating device according to the present invention.
Detailed Description
The invention is further illustrated by the following examples and figures: it should be noted that, by applying the inventive concept, various production lines can be simplified and combined, only one embodiment is given in this example, and other embodiments are given in the present invention, even though all the group patent examples are given only in some embodiments, various combinations generated by selecting and not selecting the optional stations according to the inventive concept are within the scope of the present invention, and various production lines derived according to the inventive concept are also within the scope of the present invention. In addition, for conventional stations, such as cleaning stations including alkali liquor spraying sections, alkali liquor brushing sections, electrolytic cleaning sections, hot water brushing or cold water abrasive roll brushing sections and hot water rinsing sections, even new cleaning technologies of high-pressure water jet brushing sections, ultrasonic cleaning sections, high-pressure cleaning sections and the like are simplified and combined, and are considered to be the production line of the invention, and are also within the protection scope of the invention. As another example, finishing stations including trimming, oiling, etc., are also within the scope of the present invention.
Referring to fig. 4, there is shown an embodiment 1 of the present invention, in embodiment 1, a flexible cold rolling post-treatment production line suitable for producing various high-strength steel strips according to the present invention, comprising the following stations: uncoiling, welding, inlet looping, cleaning, central continuous post-treatment, intermediate looping, flattening, outlet looping, finishing and coiling; wherein,
the central continuous post-treatment station sequentially comprises a jet direct-fire preheating section, a direct-fire heating section, a radiant tube heating section, an optional transverse magnetic induction heating section or a muffle section, a radiant tube soaking section, a slow cooling section, a rapid cooling section and a reheating section; the transverse magnetic induction heating sections or the muffle furnace sections are arranged in parallel;
two process paths are arranged from the reheating section:
one path is provided with a moving channel, an overaging section and a final air-jet cooling section to a final water-cooling section;
the other path is provided with a furnace nose section, a zinc pot section, an air knife section, an alloying heating section, an alloying soaking section and a cooling section after plating to a final water cooling section;
an optional acid washing section and/or flash plating section are arranged behind the final water cooling section;
the direct-fire heating section adopts natural gas or liquefied petroleum gas combustion;
the injection direct-fire preheating section utilizes waste gas generated by combustion of the direct-fire heating section to exchange heat in the furnace to heat the recycled nitrogen-hydrogen protective gas, and then the nitrogen-hydrogen protective gas is injected to the upper surface and the lower surface of the strip steel to realize forced convection heat exchange;
The direct-fire heating section, the radiant tube heating section, the transverse magnetic induction heating section and the muffle furnace section which are arranged in parallel are arranged in series;
the rapid cooling section comprises a high-hydrogen cooling section, an aerosol cooling section or/and a water quenching cooling section.
As the production line adopts the spray direct fire preheating section and adopts high hydrogen cooling or aerosol cooling or/and water quenching cooling to carry out rapid cooling treatment, then reheating and then galvanization or overaging treatment; the furnace nose section and the moving channel section are arranged in parallel, strip steel passes through the furnace nose section backwards and is used for producing hot-dip pure zinc or alloyed hot dip galvanized products, and strip steel passes through the moving channel section and is used for producing cold-rolled or flash-plated products; in addition, an acid washing section is arranged after the final water cooling section, and a flash plating section is arranged next, so that the strip steel can be selected to pass through the acid washing section to produce cold-rolled acid washing products, can bypass the acid washing section to produce cold-rolled annealed products, and can also be selected to enter the flash plating section after being acid washed to produce flash plating products such as flash nickel plating or flash zinc plating.
The production line provided by the invention has at least three or more than three selectable process paths, and can realize the production of five different types of high-strength steel including cold rolling annealing, pickling, flash plating, hot dip pure zinc and alloy hot dip galvanizing.
In the embodiment, an optional withdrawal and straightening station and/or a surface post-treatment station such as passivation or fingerprint resistance and the like are arranged between the flattening station and the outlet looper station, so that the strip steel can be withdrawn and straightened and/or subjected to surface post-treatment.
The transverse magnetic induction heating section and the muffle furnace section are arranged in parallel and between the radiant tube heating section and the radiant tube soaking section, and the switching between the transverse magnetic induction heating section and the muffle furnace section is realized by cutting off strip steel and threading the strip steel again; the production line is further characterized in that sealing devices are arranged on the front and rear parts of the muffle furnace section, and the muffle furnace section is further provided with an atmosphere adjusting device, so that the hydrogen content, the oxygen content and the dew point in the muffle furnace section can be independently adjusted and controlled.
Referring to fig. 5, in embodiment 2 of the present invention, a balanced heat-preserving section is further disposed between the reheating section and the furnace nose section, and hot galvanizing is performed after heat-preserving treatment is performed on the strip steel.
Referring to fig. 6, in embodiment 3 of the present invention, a mobile post-plating fast cooling section is further disposed between the air knife section and the post-plating cooling section, and the mobile post-plating fast cooling section is disposed in parallel with alloying heating and alloying soaking, so as to realize fast cooling of the strip steel after plating of the hot-dip galvanized pure high-strength steel product; preferably, a mobile plating post-fast cooling section is arranged within a range of 10 meters above the air knife section.
Referring to fig. 7, there is shown an embodiment 4 of the present invention, in which a secondary reheating section is disposed after the equilibrium maintaining section in embodiment 4, the equilibrium maintaining strip steel is secondarily reheated and then hot-dip galvanized or overaged.
Referring to fig. 8, an embodiment 5 of the present invention is shown, in embodiment 5, a pickling section is disposed between the rapid cooling section (high hydrogen cooling or gas mist cooling or/and water quenching cooling section) and the reheating section, where the pickling section includes a pickling unit, a hot water scrubbing unit, a hot water rinsing unit, and a hot air drying unit, so as to implement pickling of the surface of the strip steel, and the pickling section can be used for removing an oxide layer on the surface of the strip steel after gas mist cooling or/and water quenching cooling, and can also improve the platability of the high-strength strip steel, especially the ultra-high-strength strip steel, for hot-dip pure zinc or alloyed hot dip galvanized products.
Referring to fig. 9, which shows embodiment 6 of the present invention, in embodiment 6, after the pickling section after the rapid cooling section, a flash iron or nickel plating section is disposed, and then a reheating treatment is performed, so that the platability of the ultra-high-strength steel strip can be further improved.
Preferably, the soaking section of the radiant tube adopts an air-jet radiation composite heating device to realize rapid adjustment of the soaking temperature of the strip steel.
Referring to fig. 10 and 11, the jet direct-fire preheating device according to the present invention includes: a direct burner 1 and a preheating furnace 2; wherein,
the direct burner 1 comprises:
a furnace shell 11, the upper and lower ends of which are respectively provided with a furnace top roller chamber 101 and a furnace bottom roller chamber 102; the furnace top roller chamber 101 and the furnace bottom roller chamber 102 are respectively provided with steering rollers 12 and 12'; a plurality of direct-fire heating areas 111 are arranged in the furnace shell 11 along the height direction, and a plurality of direct-fire burners 13 are arranged in the direct-fire heating areas 111; the side wall of the upper part of the furnace shell 11 is provided with two through holes which are symmetrically arranged left and right;
the preheating furnace 2 includes:
the furnace body 21 is provided with two connecting holes on the side wall of the upper part, is symmetrically arranged left and right, and is respectively connected with the through holes on the upper part of the furnace shell 11 of the direct-fired furnace 1 through the communicating pipe 22; the top end of the furnace body 21 is provided with a furnace throat 211 which corresponds to the furnace top roller chamber 101 of the direct furnace 1 and is used for the strip steel to pass through; the bottom of the furnace body 21 is provided with a strip steel inlet and a corresponding sealing device 212 and a steering roller 23; an upper partition plate 213 with a through hole is arranged at the upper part in the furnace body 21 to form a direct-fire waste gas upper gas collection chamber 201; a direct-fire combustion waste gas secondary combustion chamber 202 is arranged below the direct-fire waste gas upper gas collection chamber 201, and at least one open-fire burner 24 is arranged in the direct-fire combustion waste gas secondary combustion chamber 202; a lower partition plate 214 with a penetrating hole is arranged at the lower part in the furnace body 21 to form a lower straight fire waste gas collecting chamber 203, and is connected with a waste gas fan 25 through a waste gas discharge pipeline 215 to be discharged from a chimney 500;
A plurality of heat exchange and air injection bellows units 26 which are arranged at two sides below the direct-fire combustion waste gas secondary combustion chamber 202 in the furnace body 21 along the height direction of the furnace body 21, and a penetrating channel 204 for the strip steel to pass through is formed in the middle; each heat exchange and air injection bellows unit 26 includes,
a bellows body 261, in which a plurality of heat exchange tubes 262 are vertically arranged, and a plurality of nozzles 263 are arranged on one side surface of the bellows body 261 opposite to the threading channel 204; an exhaust gas secondary mixing chamber 205 communicated with the heat exchange tube 262 is arranged between the upper and lower bellows bodies 261; introducing nitrogen and hydrogen protective gas into the bellows 261;
a circulating fan 264, the inlet of which is arranged in the threading channel 204, and the outlet of which is arranged in the bellows 261;
a plurality of sealing devices 27, 27', 27″ for the strip steel to pass through are respectively arranged at the upper and lower ports of the strip passing channel 204 and at the strip passing holes of the upper and lower partition plates 213, 214.
Preferably, a combustion exhaust gas thermometer 28 is also disposed in the direct-fired combustion exhaust gas secondary combustion chamber 202.
Preferably, the sealing devices 27, 27', 27″ are nitrogen sealing structures, and nitrogen sealing chambers are adopted, on which nitrogen injection pipelines are arranged.
Preferably, a control valve 216 is provided on the exhaust gas discharge pipe 215.
The strip steel 100 is turned to upwards run by a turning roll in front of the direct fire furnace, enters the preheating furnace 2 for preheating after being sealed by a preheating furnace inlet sealing device, then enters a furnace top roll chamber of the direct fire furnace 1 for direct fire heating after being turned by the turning roll, then enters a furnace bottom roll chamber of the direct fire furnace 1 for continuous running after being turned by the turning roll.
The temperature of the waste gas is reduced after the nitrogen-hydrogen protective gas is heated by the direct-fire combustion waste gas through the heat exchange pipeline (the nitrogen-hydrogen protective gas is blown to the upper surface and the lower surface of the strip steel to preheat the strip steel under the action of the circulating fan), and the nitrogen-hydrogen protective gas after the temperature reduction is sucked into the bellows by the circulating fan 264 on the two sides of the working side (WS side) and the driving side (DS side) of the preheating furnace to exchange heat with the heat exchange pipeline; the direct-fired combustion waste gas sequentially passes through the heat exchange and air injection bellows unit from top to bottom, is subjected to secondary utilization of the waste heat of the combustion waste gas outside the furnace through the waste heat boiler 400 under the suction of the variable-frequency waste gas fan 25 and enters the chimney 500 for final discharge.
Referring to fig. 13 to 16, the jet-radiation composite heating device according to the present invention includes:
a furnace body 4 in which a composite heating body 5 is arranged in the height direction; the composite heating body 5 comprises a metal sheet and a metal sheet,
A heat-insulating box 51, the inner wall of which is provided with a heat-insulating material; a mounting hole is arranged in the center of one side surface of the heat preservation box body 51;
the circulating fan 52 is arranged at the mounting hole of the heat insulation box body 51, the air suction inlet 521 of the circulating fan corresponds to the axis of the mounting hole, and the air outlet 522 is arranged on the side surface of the casing;
the buffer cavity 53 is arranged in the insulation box 51 at a position corresponding to the air suction opening of the circulating fan 52, the back surface of the buffer cavity 53 is provided with a hot air outlet corresponding to the air suction opening of the circulating fan 52, and the front surface of the buffer cavity is provided with a hot air inlet;
the two high-temperature air jet bellows 54, 54' are vertically and symmetrically arranged at two sides of the hot air inlet at the front side of the buffer cavity 53 in the heat insulation box body 51 to form a strip penetrating channel 200 for the strip 100 to penetrate through; a plurality of rows of jet nozzles 55, 55 'are arranged on one side surface of the two high-temperature jet bellows 54, 54' positioned on two sides of the threading channel 100 at intervals along the height direction, and a gap 300 is arranged between n rows of jet nozzles, wherein n is more than or equal to 1;
the plurality of radiant tubes 56, 56 'are symmetrically arranged in the two high-temperature jet bellows 54, 54', and the radiant tubes 56 (radiant tubes 56 are exemplified by the same below) comprise a connecting tube section 561 for connecting with a burner, a radiant tube section 562 which is bent and extended from one end of the connecting tube section 561, and a heat exchange tube section 563 which is formed by extending and bending from one end of the radiant tube section 562; the radiant tube sections 562 correspond to the gaps 300 provided between the n rows of jet nozzles in the high temperature jet bellows 54 to form an alternating jet and radiant configuration.
Preferably, the buffer cavity and the high-temperature air injection bellows are of an integrated structure.
Preferably, the diameter of the jet nozzle is 1/10-1/5 of the distance from the jet nozzle to the strip steel.
Preferably, the jet nozzle adopts a round hole structure.
Preferably, the radiant tube adopts a space four-stroke structure to form four sections of tube sections which are arranged in parallel, wherein one of the tube sections is a radiant tube section, and the rest is a connecting tube section and a heat exchange tube section.
Example 1
The production line is shown in fig. 4, the main chemical composition (mass%) of the substrate is 0.09% C-0.20% Si-2.1% Mn, after the strip steel is uncoiled, welded, inlet loopers pass through and cleaned, the strip steel is sprayed with direct fire to be preheated to 365 ℃, then the radiation pipe is heated to 825 ℃, the strip steel is arranged in parallel with a muffle furnace in a transverse magnetic induction heating section, the strip steel passes through the transverse magnetic induction heating section, the transverse magnetic induction heating section is heated to 925 ℃, then the radiation pipe is soaked for 60 seconds at 925 ℃, the strip steel is slowly cooled to 750 ℃, the quick cooling section is arranged in parallel by high hydrogen cooling, aerosol cooling and water quenching, the strip steel passes through the aerosol cooling section, the aerosol cooling section is then passed through a reheating section and a moving channel, the strip steel enters an overaging section at 290 ℃, overaging treatment (reheating is not needed to be put into use) is finally cooled to about 140 ℃, the strip steel is subjected to final water cooling to room temperature, and an optional pickling section and an optional plating section is arranged after final water cooling, the strip steel is subjected to finishing treatment, the strip steel is finished through the intermediate section, directly enters an outlet loopers, and is coiled, and the loopers are coiled. The final product band steel has the yield strength of 951MPa, the tensile strength of 1182MPa and the elongation at break of 12 percent.
Example 2
A preparation method of ultra-high-strength strip steel comprises the steps of uncoiling, welding, passing through an inlet loop and cleaning strip steel with the main chemical component (mass%) of 0.082-0.88-1.85-Mn of a substrate, spraying direct fire to preheat to 370 ℃, heating to 670 ℃ by direct fire, heating a radiant tube to 810 ℃, arranging the transverse magnetic induction heating and the muffle in parallel, carrying out surface micro pre-oxidation on the strip steel in the embodiment by the muffle (nitrogen doped with trace air) for 60 seconds (soaking section is filled with nitrogen and hydrogen protective gas) at 810 ℃, slowly cooling to 675 ℃, cooling the strip steel in the embodiment to 675 ℃ by high hydrogen gas jet, cooling to the temperature by the high hydrogen jet, entering the furnace nose by the reheating section (no start-up investment) and the balanced heat-preserving section, carrying out hot galvanizing by a zinc pot, carrying out hot galvanizing by an air knife, carrying out alloying to 520 ℃, carrying out alloying to about 510 ℃, cooling to about 140 seconds, carrying out water cooling to the soaking section, carrying out water cooling to the intermediate section, and entering the strip steel in the intermediate section to 475, and finishing the strip steel. The yield strength of the final product is 797MPa, the tensile strength is 1028MPa, and the elongation at break is 13%.
Example 3
A preparation of ultra-high-strength strip steel, the production line of which is shown in figure 6, wherein the main chemical composition (mass%) of a substrate is 0.10 percent C-0.18 percent Si-1.90 percent Mn, strip steel is uncoiled, welded, passed through an inlet loop and cleaned, sprayed with direct fire and preheated to 365 ℃, then heated to 665 ℃ by direct fire, heated to 830 ℃ by a radiant tube, the transverse magnetic induction heating and muffle furnace are arranged in parallel, the strip steel is heated to 930 ℃ by transverse magnetic induction, then soaked for 60 seconds by the radiant tube at 930 ℃, slowly cooled to 730 ℃, then cooled to about 350 ℃ by high hydrogen, then heated to 460 ℃, immersed into a zinc pot through a furnace nose for hot galvanizing after being subjected to air knife control coating weight, quickly cooled after being subjected to mobile plating, the quick cooling section is arranged in parallel with an alloying heating and alloying section after mobile plating, the strip steel is quickly cooled after being subjected to plating, then cooled to room temperature by a cooling section after being subjected to final cooling, and cooled to room temperature by entering an intermediate loop, then is subjected to leveling after passing through an outlet loop, finishing and coiling, and completing production. The yield strength of the final product strip steel is 651MPa, the tensile strength is 992MPa, and the breaking elongation is 17%.
Example 4
A production line of ultra-high-strength strip steel is shown in figure 7, the main chemical composition (mass%) of a substrate is 0.15% C-1.7% Si-2.3% Mn strip steel, uncoiling, welding, passing through an inlet looper, cleaning, preheating to 360 ℃ by adopting jet direct fire, heating to 710 ℃ by adopting direct fire, heating to 810 ℃ by adopting a radiant tube, arranging the transverse magnetic induction heating and a muffle furnace in parallel, enabling the strip steel to pass through a transverse magnetic induction heating section to 910 ℃, soaking the radiant tube for 70 seconds at 910 ℃, slowly cooling to 675 ℃, arranging a quick cooling section in parallel by adopting high hydrogen cooling, water mist cooling and water quenching, cooling the strip steel to 230 ℃, then heating to 410 ℃ in a balanced mode, then reheating to 460 ℃, immersing the strip steel into a zinc pot through a furnace nose, hot galvanizing, cooling after controlling the weight of a coating by adopting an air knife, cooling after plating by adopting an alloying heating section (heating function is not input) and an alloying soaking section (function is not input), entering into an intermediate looper, and finishing production is completed. The final product band steel has the yield strength of 695MPa, the tensile strength of 1039MPa and the breaking elongation of 21.5 percent.
Example 5
A production line of ultra-high-strength strip steel is shown in figure 8, the strip steel with the main chemical composition (mass%) of 0.16 percent C-0.35 percent Si-2.4 percent Mn is uncoiled, welded, passed through an inlet loop and cleaned, sprayed with direct fire to be preheated to 365 ℃, then heated to 665 ℃, then heated to 820 ℃ by the direct fire, passed through a muffle furnace, soaked for 50 seconds by the radiant tube at 820 ℃, slowly cooled to 746 ℃, quenched to room temperature by water, then pickled, heated to 230 ℃ by a reheating section, passed through a balanced heat-preserving section and a secondary reheating section (without adding heating function), passed through a moving channel section, passed through an overaging section and finally cooled to 140 ℃ by air injection, then finally cooled to room temperature, passed through an intermediate loop, passed through an outlet loop after flattening, finished and coiled, and finished the production. The final product has a yield strength of 1262MPa, a tensile strength of 1483MPa and an elongation at break of 5%.
Example 6
The production line of the ultra-high strength strip steel is shown in fig. 9, and the main chemical components (mass%) of the substrate are: uncoiling, welding, passing through an inlet loop, cleaning a strip steel with 0.15-0.32% of C-2.3% of Mn, spraying direct fire, preheating to 360 ℃, then heating to 660 ℃ by direct fire, heating to 820 ℃ by a radiant tube, carrying out soaking for 60 seconds by the radiant tube at 820 ℃ after the radiant tube is empty and passed through a muffle furnace, slowly cooling to 742 ℃, carrying out water quenching to room temperature, then carrying out acid washing, then carrying out flash plating iron, heating to 235 ℃ by a reheating section, carrying out overaging treatment at about 230 ℃ by a moving channel section after passing through a balanced heat preservation section and a secondary reheating section (without throwing in a heating function), finally carrying out air injection cooling to about 140 ℃, then carrying out water cooling to room temperature, entering an intermediate loop, and carrying out passing through, finishing and coiling by an outlet loop after flattening, thus completing production. The yield strength of the final product is 1213MPa, the tensile strength is 1415MPa, and the breaking elongation is 6%.
The flexible cold rolling post-treatment production line suitable for producing various high-strength strip steels has the advantages of realizing industrial application, flexibly producing various high-strength steels and ultrahigh-strength steels, along with large market flexibility, and having very wide application prospects under the conditions that the variety of the existing ultrahigh-strength steels is large and the market demands are increased year by year.
Claims (11)
1. A flexible cold rolling post-treatment production line suitable for producing various ultra-high strength strip steels is characterized by comprising the following stations: uncoiling, welding, inlet looping, cleaning, central continuous post-treatment, intermediate looping, flattening, outlet looping, finishing and coiling; wherein,
the central continuous post-treatment station sequentially comprises a jet direct-fire preheating section, a direct-fire heating section, a radiant tube heating section, an optional transverse magnetic induction heating section or a muffle section, a radiant tube soaking section, a slow cooling section, a rapid cooling section and a reheating section; the transverse magnetic induction heating sections or the muffle furnace sections are arranged in parallel;
two process paths are arranged from the reheating section:
one path is provided with a moving channel, an overaging section and a final air-jet cooling section to a final water-cooling section;
the other path is provided with a furnace nose section, a zinc pot section, an air knife section, an alloying heating section, an alloying soaking section and a cooling section after plating to a final water cooling section;
An optional acid washing section and/or a flash plating section are arranged behind the final water cooling section;
the direct-fire heating section adopts natural gas or liquefied petroleum gas combustion;
the injection direct-fire preheating section utilizes waste gas generated by combustion of the direct-fire heating section to exchange heat in the furnace to heat the recycled nitrogen-hydrogen protective gas, and then the nitrogen-hydrogen protective gas is injected to the upper surface and the lower surface of the strip steel to realize forced convection heat exchange;
the direct-fire heating section, the radiant tube heating section, the transverse magnetic induction heating section and the muffle furnace section which are arranged in parallel are arranged in series;
the rapid cooling section comprises a high-hydrogen cooling section, an aerosol cooling section or/and a water quenching cooling section.
2. The flexible cold rolling post-treatment production line suitable for producing various ultra-high strength strip steels according to claim 1, wherein optional withdrawal and straightening stations and/or surface post-treatment stations such as passivation or fingerprint resistance are arranged between the flattening station and the outlet looper station.
3. The flexible cold rolling post-treatment production line suitable for producing various ultra-high-strength strip steels according to claim 1 or 2, wherein the transverse magnetic induction heating section and the muffle furnace section are arranged in parallel and between the radiant tube heating section and the radiant tube soaking section, and the switching between the transverse magnetic induction heating section and the muffle furnace section is realized by cutting off the strip steels and re-threading; the muffle furnace section is provided with sealing devices at the front and back, and is also provided with an atmosphere adjusting device for independently adjusting and controlling the hydrogen content, the oxygen content and the dew point in the muffle furnace section.
4. A flexible cold rolling post-treatment production line suitable for producing various ultra-high strength strip steel according to claim 1, 2 or 3, wherein a balanced heat preservation section is arranged between the reheating section and the furnace nose section, and the strip steel is subjected to heat preservation treatment and then hot galvanizing.
5. The flexible cold rolling post-treatment production line suitable for producing various ultra-high-strength strip steels according to claim 4, wherein a secondary reheating section is arranged after the balanced heat-preserving section, and the balanced heat-preserving strip steels are subjected to secondary reheating and then hot galvanizing or overaging treatment.
6. The flexible cold rolling post-treatment production line suitable for producing various ultra-high strength steel strips according to any one of claims 1 to 5, wherein a mobile post-plating quick cooling section is arranged between the air knife section and the post-plating cooling section, and the mobile post-plating quick cooling section is arranged in parallel with an alloying heating device to realize quick cooling of the steel strips after plating of hot-dip pure zinc high strength steel products; preferably, a mobile plating post-fast cooling section is arranged within a range of 10 meters above the air knife section.
7. The flexible cold rolling post-treatment production line suitable for producing various ultra-high-strength strip steel according to any one of claims 1 to 6, wherein a pickling section is arranged between the rapid cooling section and the reheating section, and comprises a pickling unit, a hot water scrubbing unit, a hot water rinsing unit and a hot air drying unit, so that the surface of the strip steel is pickled.
8. The flexible cold rolling post-treatment line suitable for producing a plurality of ultra-high strength steel strips according to any one of claims 1 to 7, wherein a flash iron or nickel plating section is provided after the pickling section following the rapid cooling section.
9. The flexible cold rolling post-treatment production line suitable for producing various ultra-high-strength strip steel according to any one of claims 1 to 8, wherein the soaking section of the radiant tube is changed to a jet-air radiation composite heating device, so that the quick adjustment of the soaking temperature of the strip steel is realized.
10. A jet direct-fire preheating device for a flexible cold rolling post-treatment line according to any one of claims 1 to 9, characterized by comprising: a direct fire furnace and a preheating furnace; wherein, the direct fire includes:
a furnace shell, the upper end and the lower end of which are respectively provided with a furnace top roller chamber and a furnace bottom roller chamber; steering rollers are respectively arranged in the furnace top roller chamber and the furnace bottom roller chamber; a plurality of direct-fire heating areas are arranged in the furnace shell along the height direction, and a plurality of direct-fire burners are arranged in the direct-fire heating areas; the side wall of the upper part of the furnace shell is provided with at least two through holes which are symmetrically arranged left and right;
the preheating furnace comprises:
the side wall of the upper part of the furnace body is provided with at least two connecting holes which are symmetrically arranged left and right and are respectively connected with the through holes on the upper part of the furnace shell of the direct-fired furnace through communicating pipes; the top end of the furnace body is provided with a furnace throat which corresponds to the furnace top roller chamber of the direct furnace and is used for the strip steel to pass through; the bottom of the furnace body is provided with a strip steel inlet, a corresponding sealing device and a corresponding steering roller; an upper partition plate with a through hole is arranged at the upper part in the furnace body to form an upper gas collection chamber of the direct-fire waste gas; a direct-fire combustion waste gas secondary combustion chamber is arranged below the upper gas collection chamber of the direct-fire waste gas, and at least one open-fire burner is arranged in the direct-fire combustion waste gas secondary combustion chamber; preferably, a combustion waste gas thermometer is further arranged in the direct-fired combustion waste gas secondary combustion chamber; a lower partition plate with a penetrating hole is arranged at the lower part in the furnace body to form a lower straight fire waste gas collecting chamber, and the lower straight fire waste gas collecting chamber is connected with a waste gas fan through a waste gas discharge pipeline; a control valve is arranged on the waste gas discharge pipeline;
The heat exchange and air injection bellows units are arranged on two sides below the direct-fired combustion waste gas secondary combustion chamber in the furnace body along the height direction of the furnace body, and a strip penetrating channel for strip steel to pass through is formed in the middle of the heat exchange and air injection bellows units; each heat exchange and air injection bellows unit comprises,
the air box body is vertically provided with a plurality of heat exchange tubes, and a plurality of nozzles are arranged on one side surface of the air box body, which is opposite to the threading channel; an exhaust gas secondary mixing chamber communicated with the heat exchange tube is arranged between the upper and lower bellows bodies; introducing nitrogen and hydrogen protective gas into the bellows body;
the port of the inlet pipeline of the circulating fan is arranged in the threading channel, and the port of the outlet pipeline of the circulating fan is positioned in the bellows body;
the sealing devices are respectively arranged at the upper and lower ports of the threading channel and the threading holes of the upper and lower partition plates; preferably, the sealing device is of a nitrogen sealing structure, a nitrogen sealing chamber is adopted, and a nitrogen injection pipeline is arranged on the sealing device.
11. A jet-radiation composite heating device for a flexible cold rolling finishing line according to any one of claims 1 to 9, characterized by comprising:
the furnace body is internally provided with a composite heating body along the height direction; the composite heating body comprises a plurality of heating elements,
The inner wall of the shell of the heat preservation box body is provided with a heat preservation material; a mounting hole is arranged in the center of one side surface of the heat preservation box body;
the circulating fan is arranged at the mounting hole of the heat insulation box body, the air suction inlet of the circulating fan corresponds to the axis of the mounting hole, and the air outlet is arranged on the side surface of the shell;
the buffer cavity is arranged in the insulation box body at a position corresponding to the air suction opening of the circulating fan, the back surface of the buffer cavity is provided with a hot air outlet corresponding to the air suction opening of the circulating fan, and the front surface of the buffer cavity is provided with a hot air inlet; preferably, the buffer cavity and the high-temperature air injection bellows are of an integrated structure;
the two high-temperature air jet bellows are vertically and symmetrically arranged at two sides of a hot air inlet at the front side of the buffer cavity in the heat insulation box body to form a strip penetrating channel for strip steel to pass through; a plurality of rows of jet nozzles are arranged on one side surface of the two high-temperature jet bellows at two sides of the threading channel at intervals along the height direction, and a gap is arranged between n rows of jet nozzles, wherein n is more than or equal to 1; preferably, the diameter of the jet nozzle is 1/10-1/5 of the distance from the jet nozzle to the strip steel; more preferably, the jet nozzle adopts a round hole structure;
the radiant tubes are symmetrically arranged in the two high-temperature air injection bellows and comprise a connecting tube section for connecting a burner, a radiant tube section bent and extended from one end of the connecting tube section and a heat exchange tube section formed by extending and bending from one end of the radiant tube section; the radiant tube section corresponds to gaps arranged between n rows of jet nozzles in the high-temperature jet bellows, so as to form a jet-radiation alternating structure; preferably, the radiant tube section, the connecting tube section and the heat exchange tube section of the radiant tube are arranged in parallel.
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