Technical background
In hot rolling production process, heating steel billet energy consumption generally accounts for 70% ~ 80% of process energy consumption, and the energy consumption for rolling only accounts for 20% ~ 30%, and the potentiality therefore reducing hot rolling energy consumption are mainly derived from the energy consumption of billet heating furnace.In existing hot rolled strip production process, raw material before the rolling, heat by blank, improves the plasticity of steel, reduces resistance to deformation and improves metal inside structure and properties, so that rolling processing.But high temperature and incorrect heating cycle may cause the defects such as the strong oxidation of steel, decarburization and burning, reduce the quality of steel, even cause waste product.Therefore, the Heating temperature of steel should according to the characteristic of various steel and rolling technology requirement, and collateral security steel product quality and output are set out and determined.
In existing hot rolled strip production technology, also there is the relevant report about reducing Heating temperature.As document " Huang Chuanqing; Chen Jianrong etc.; Baosteel 2050mm hot continuous rolling low temperature rolling technology application brief analysis; " bao steel technology " " describes the application of Baosteel in low temperature rolling technology, Heating temperature being reduced to 1200 DEG C, by optimizing rolling procedure and the de-scaling passage of roughing, increasing the measures such as de-scaling dash chain, reduce the temperature drop at rough rolling step, ensure the temperature in of finish rolling.But this low temperature rolling method, although Heating temperature is lower than original conventional heating temperature 1250 DEG C, but mainly considers Heating temperature, does not carry out the overall situation and systematic consideration to the whole operation of rolling.The patent No. is the Chinese patent " warm rolling method " of CN200480013648.7, describe a kind of novel multi-direction warm rolling method, be mainly used in the rolling of Bar Wire Product, manufacture the ultra tiny crystal grain steel having median size and be less than the ultra tiny grain structure of 3 μm, the temperature range being 350 DEG C ~ 800 DEG C in temperature range carries out groove rolling.The patent No. be the Chinese patent " warm rolling method of Twisted Steel " of CN94105768.2 it is also proposed a kind of utilize hot rolling after waste heat carry out the production method of warm-rolling Twisted Steel again, steel after hot rolling are cooled on cold bed 300 DEG C ~ 600 DEG C, by attemperator, steel are delivered to roughing mill rolling, the wire rod after rolling carries out finish rolling tube reducing rag again.Above two patents are applied to the production of wire and rod, only consider the temperature of the operation of rolling, equally also do not do an of overall importance and systematic consideration to the low temperature rolling of the whole operation of rolling.
In addition, the patent No. is the Chinese patent " a kind of temperature-controlled rolling method of Q345 steel plate " of CN201010607955.5, propose and Q345 plate slab is come out of the stove after preheating section, heating zone, soaking zone in pusher-type furnace, except removing iron scale, carry out first stage rolling at 1000 DEG C ~ 1050 DEG C, then treat that temperature carries out subordinate phase rolling to 900 DEG C ~ 950 DEG C by air cooling or water-cooled.This rolling method, or adopt controlled rolling air cooling technique thinking to ensure the mechanical property of Q345 steel plate, do not adopt critical temperature thought, Heating temperature and the whole operation of rolling are carried out to the consideration of energy-conservation aspect.Therefore, be also a kind of Rolling production process of nonsystematic and locality.
In sum, existing hot rolled strip production method, main or conventional heat, the thinking be then rolled.Also have and consider from reduction energy consumption, reduce the trial of Heating temperature, but be all go to consider from each isolated point of the rolling process such as heating or rolling.Effect is not clearly.
Summary of the invention
Object of the present invention is exactly to provide a kind of low alloy steel based on critical temperature energy-saving rolling method, the method is for the feature of low alloy steel, propose systematicness and low temperature rolling production method of overall importance, good tissue, mechanical property level can be ensured, heating energy consumption can be effectively reduced again, reduce production cost.
For realizing this object, the energy-saving rolling method of the low alloy steel based on critical temperature designed by the present invention, comprise the step of alloy steel sheet billet successively de-scaling before process furnace thermal pretreatment, process furnace heat treated, the equal thermal treatment of process furnace, roughing, roughing, finish rolling, section cooling and coiling process, it is characterized in that:
The warm up time of described alloy steel sheet billet when process furnace thermal pretreatment is 50 ~ 100min, and preheating temperature is 800 ~ 1000 DEG C;
The heat-up time of described alloy steel sheet billet when process furnace heat treated is 50 ~ 100min, and Heating temperature is 1200 ~ 1280 DEG C;
The heat-up time of described alloy steel sheet billet when the equal thermal treatment of process furnace is 15 ~ 40min, and soaking temperature is 1170 ~ 1220 DEG C;
The roughing temperature out of described alloy steel sheet billet when roughing is 1020 ~ 1060 DEG C;
The entry temperature at finishing of described alloy steel sheet billet when finish rolling is 980 ~ 1040 DEG C, and described exit temperature at finishing is 820 ~ 870 DEG C;
Described alloy steel sheet billet temperature is when take-up 580 ~ 650 DEG C.
Further, the chemical composition of described alloy steel sheet billet by mass percentage wt% is C:0.10 ~ 0.16%, Si:0.01 ~ 0.30%, Mn:1.20 ~ 1.6%, S≤0.030%, P≤0.030%, Nb≤0.03%, Ti≤0.05%, and all the other are iron and inevitable impurity.
Further, the air-fuel ratio of described alloy steel sheet billet when process furnace thermal pretreatment is 1.0 ~ 1.2; The air-fuel ratio of described alloy steel sheet billet when process furnace heat treated is 0.9 ~ 1.1; Described alloy steel sheet billet in the combustion of process furnace equal thermal treatment space-time than being 1.0 ~ 1.4.
Further, described alloy steel sheet billet is 150min ~ 200min at total time inside furnace of process furnace.
Further, the furnace pressure of described process furnace is 10 ~ 25Pa.
Again further, the de-scaling passage before described roughing in de-scaling treating processes is 4 ~ 8.
Further, the roll speed of described alloy steel sheet billet when finish rolling is 5 ~ 12m/s.
The present invention adopts the process control method in the rolling process, by reducing the Heating temperature of process furnace, alloy steel sheet billet is rolled between pair rolling temperature history and rolling critical temperature, produces the hot rolled strip of the low alloy steel meeting organization mechanics performance requriements.In addition, the process control method in the rolling process significantly reduces Heating temperature while guarantee effect of rolling, decreases heating energy consumption, has saved the production cost of hot rolled strip.
Embodiment
Below in conjunction with specific embodiment, the present invention is described in further detail:
Heating temperature in the conventional hot rolled strip operation of rolling and operation of rolling temperature general higher, therefore, in actual hot rolled strip production process, because too high Heating temperature causes the energy consumption of slab when process furnace heats more.The present invention proposes the energy-saving rolling method of a kind of low alloy steel based on critical temperature, the method formulates the critical temperature of the required operation of rolling on the basis ensureing original alloy steel sheet billet mechanical property, and the basis of critical temperature is made the rolling method of low alloy steel.The critical temperature of the alloy steel sheet billet operation of rolling is determined by following formula:
Critical temperature determination formula:
RH=Max [T (hot-short), T (C solid solution), T (Mn solid solution), T (Nb solid solution), T (Ti solid solution), T (de-scaling)]
RT=Max [T (roughing machine power energy), T (nipping of milling train), T (FT0+ Δ T transportation temperature drop+Δ T de-scaling temperature drop)]
FT0=Max [T (FT7+ Δ T operation of rolling temperature drop), T (finish rolling machine power energy), T (recrystallize mark)]
FT7=Min [T (Ar3), T (NbC precipitation), T (TiC precipitation), T (TiN precipitation)]
CT=T (transformation temperature)
In above-mentioned formula: T is temperature, RH is soaking zone heating critical temperature, RT is roughing outlet critical temperature, FT0 is the critical temperature of finish rolling entrance, FT7 is that finish rolling outlet critical temperature, CT are for batching critical temperature.
The energy-saving rolling method of low alloy steel based on critical temperature of the present invention's design, it comprises the steps:, by alloy steel sheet billet successively de-scaling before process furnace thermal pretreatment, process furnace heat treated, the equal thermal treatment of process furnace, roughing, roughing, finish rolling, section cooling and coiling process, namely to complete the rolling of whole alloy steel sheet billet; It is systemic and of overall importance that above-mentioned steps makes rolling method have;
The warm up time of described alloy steel sheet billet when process furnace thermal pretreatment is 50 ~ 100min, and preheating temperature is 800 ~ 1000 DEG C;
The heat-up time of described alloy steel sheet billet when process furnace heat treated is 50 ~ 100min, and Heating temperature is 1200 ~ 1280 DEG C;
The heat-up time of described alloy steel sheet billet when the equal thermal treatment of process furnace is 15 ~ 40min, and soaking temperature is 1170 ~ 1220 DEG C;
In technique scheme, by the selection to process furnace each section of acid extraction parameter, whole board briquette is even in the short period of time to make low alloy steel, and meets Heating temperature requirement.
The roughing temperature out of described alloy steel sheet billet when roughing is 1020 ~ 1060 DEG C;
In technique scheme, entry temperature at finishing substantially remains unchanged or slightly reduces in original temperature schedule, and the entry temperature at finishing of alloy steel sheet billet when finish rolling is 980 ~ 1040 DEG C, and described exit temperature at finishing is 820 ~ 870 DEG C;
Described alloy steel sheet billet temperature is when take-up 580 ~ 650 DEG C.
In technique scheme, alloy steel sheet billet is in low temperature rolling process, and due to the reduction of texturing temperature, the mechanical property of band steel can have a certain upgrade; Meanwhile, consider that chilling process can cause the difficulty of de-scaling, therefore on the basis of comprehensive mechanical property and surface quality, following regulation has been made to the chemical composition of low alloy steel.The chemical composition of described alloy steel sheet billet by mass percentage wt% is C:0.10 ~ 0.16%, Si:0.01 ~ 0.30%, Mn:1.20 ~ 1.6%, S≤0.030%, P≤0.030%, Nb≤0.03%, Ti≤0.05%, and all the other are iron and inevitable impurity.
In technique scheme, the air-fuel ratio of described alloy steel sheet billet when process furnace thermal pretreatment is 1.0 ~ 1.2; The air-fuel ratio of described alloy steel sheet billet when process furnace heat treated is 0.9 ~ 1.1; Described alloy steel sheet billet in the combustion of process furnace equal thermal treatment space-time than being 1.0 ~ 1.4.
In technique scheme, described alloy steel sheet billet is 150min ~ 200min at total time inside furnace of process furnace.
In technique scheme, the furnace pressure of described process furnace is the pressure-fired of 10 ~ 25Pa, prevents from sucking cold wind.
In technique scheme, the de-scaling passage before described roughing in de-scaling treating processes is 4 ~ 8.Need the surface quality ensureing alloy steel sheet billet in rough rolling process, and adopt stay-warm case to reduce the temperature drop of rough rolling process.
In technique scheme, the roll speed of described alloy steel sheet billet when finish rolling is 5 ~ 12m/s.By promoting roll speed, ensure that exit temperature at finishing and coiling temperature remain unchanged on original conventional hot rolling technology.
In technique scheme, adopt edge-masking technology when the process of alloy steel sheet billet section cooling, reduce the edge temperature drop of hot rolled strip in process of cooling.
Choose the Rolling Production process of 3 blocks of slabs to low alloy steel to be below described:
Composition is in table 1
Table 1 smelts composition and technology point
Table 2 operation of rolling temperature
In table 2, RH is soaking zone Heating temperature, RT is roughing temperature out, FT0 is entry temperature at finishing, FT7 is exit temperature at finishing, CT is coiling temperature.
Above-mentioned slab 1 is 196min at total time inside furnace of heat-processed.The pressure-fired of 25Pa is kept in heating-furnace, process furnace preheating section air-fuel ratio remains on 1.2, warm up time is 68min, process furnace heating zone air-fuel ratio remains on 1.05, heat-up time is 100min, process furnace soaking zone air-fuel ratio remains on 1.28, and soaking temperature controls at 1185 DEG C, and soaking time is 18min.Alloy steel sheet billet takes three quarter continuous rolling mill rolling in rolling process of rough rolling, first group of roughing mill de-scaling 1 road, second group of roughing mill rolling 5 passage, de-scaling 2 road, 3rd group of roughing mill de-scaling 1 road, the 4th group of roughing mill not de-scaling, total de-scaling passage is 4 passages, adopt stay-warm case to reduce rough rolling process temperature drop, the 4th group of roughing mill roughing temperature out is 1037 DEG C.Entry temperature at finishing is 1022 DEG C, and roll speed is 5.4m/S, and exit temperature at finishing is 837 DEG C, and coiling temperature is 631 DEG C, adopts edge-masking technology in laminar cooling process, reduces the edge temperature drop of hot rolled strip in process of cooling.
Above-mentioned slab 2 is 157min at total time inside furnace of heat-processed.The pressure-fired of 20Pa is kept in heating-furnace, process furnace preheating section air-fuel ratio remains on 1.1, warm up time is 59min, process furnace heating zone air-fuel ratio remains on 1.04, heat-up time is 79min, process furnace soaking zone air-fuel ratio remains on 1.25, and soaking temperature controls at 1200 DEG C, and soaking time is 19min.Alloy steel sheet billet takes three quarter continuous rolling mill rolling in rolling process of rough rolling, first group of roughing mill de-scaling 1 road, second group of roughing mill rolling 5 passage, de-scaling 2 road, 3rd group of roughing mill de-scaling 1 road, the 4th group of roughing mill not de-scaling, total de-scaling passage is 4 passages, adopt stay-warm case to reduce rough rolling process temperature drop, the 4th group of roughing mill roughing temperature out is 1055 DEG C.Entry temperature at finishing is 1023 DEG C, and roll speed is 5.06m/S, and exit temperature at finishing is 839 DEG C, and coiling temperature is 613 DEG C, adopts edge-masking technology in laminar cooling process, reduces the edge temperature drop of hot rolled strip in process of cooling.
Above-mentioned slab 3 is 175min at total time inside furnace of heat-processed.The pressure-fired of 22Pa is kept in heating-furnace, process furnace preheating section air-fuel ratio remains on 1.1, warm up time is 64min, process furnace heating zone air-fuel ratio remains on 1.05, heat-up time is 90min, process furnace soaking zone air-fuel ratio remains on 1.15, and soaking temperature controls at 1200 DEG C, soaking time 21min.Alloy steel sheet billet takes three quarter continuous rolling mill rolling in rolling process of rough rolling, first group of roughing mill de-scaling 1 road, second group of roughing mill rolling 5 passage, de-scaling 2 road, 3rd group of roughing mill de-scaling 1 road, the 4th group of roughing mill not de-scaling, total de-scaling passage is 4 passages, adopt stay-warm case to reduce rough rolling process temperature drop, the 4th group of roughing mill roughing temperature out is 1050 DEG C.Entry temperature at finishing 1020 DEG C, roll speed is 7.6m/S, and exit temperature at finishing is 856 DEG C, and coiling temperature is 593 DEG C, adopts edge-masking technology in laminar cooling process, reduces the edge temperature drop of hot rolled strip in process of cooling.
The hot-rolled sheet coil mechanical property contrast that above-mentioned 3 pieces of slab rollings go out is in table 2.
Table 2 is organized, mechanical property contrast
Can find out that the coil of strip microstructure and mechanical property that above 3 pieces of slab rollings go out all meets standard-required.
As can be seen from the present embodiment: the feature that the present invention is directed to low alloy steel, propose systematicness and low temperature rolling production method of overall importance, whole heating and Rolling Production process are considered, the microstructure and mechanical property level that low alloy steel is good can be ensured, heating energy consumption can be effectively reduced again, reduce production cost.
The content that specification sheets is not described in detail belongs to the known prior art of professional and technical personnel in the field.