CN105665674A - Ingredient prediction method for dissimilar steel continuous casting - Google Patents

Abstract

The invention discloses an ingredient prediction method for dissimilar steel continuous casting. The ingredient prediction method for dissimilar steel continuous casting comprises the following steps: a stopper is closed while a casting speed of a casting blank is reduced to a first casting speed value; an iron plate is inserted while a level height of a tundish is judged to achieve a preset level height interval; after the iron plate is inserted, casting for a large ladle is started at first, and then the stopper is opened and casting for the tundish is started, wherein during a level rising process of the tundish after the casting for the tundish is started, alloy element concentrations at an outlet of the tundish at the end of each time period of the level rising process of the tundish are obtained through a first molten steel mixed casting ingredient prediction model, and after the level of the tundish rises to a target tonnage, alloy element concentrations at the outlet of the tundish at the end of each time period after the target tonnage is achieved are obtained through a second molten steel mixed casting ingredient prediction model; and original steel rolling is carried out after plate blank ingredients are predicated to be qualified according to the alloy element concentrations. The technical problems of blank warehouse overstocking due to the existing manner of inserting the iron plate and carrying out continuous casting, and production period increasing of the dissimilar steel continuous casting, are solved, and the production efficiency of the continuous casting is improved.

Description

Grade transition composition prediction method

Technical field

The present invention relates to technical field of ferrous metallurgy, particularly relate to a kind of grade transition composition prediction method.

Background technology

Continuous casting produces to be organized in units of watering time. For improving production efficiency, improve as much as possible singly water time water steel stove number. For the steel grade that volume of production is little, it is possible to use the mode of grade transition improves singly waters time casting sequence. Different steel grades continuous casting between same different steel grades even waters, carry out usually by three kinds of modes: all the components has certain directly connecting of common factor to water, composition have certain gap undertaken even watering by dowel plate, the excessive mode using quick-replaceable tundish of composition gap carries out even watering.

The mode carrying out even watering currently for dowel plate needs to roll off the production line strand, and chemical examination is mixed waters base composition, it is determined for compliance with in molten steel judgement situation and just can arrange rolling, length consuming time, slab storehouse can be caused to overstock, reduce slab storehouse turnover ability, the production cycle of grade transition also can be caused to lengthen.

Summary of the invention

The embodiment of the present invention, by providing a kind of grade transition composition prediction method, solves existing dowel plate and carries out even watering and the technical problem that overstocks in the base storehouse that exists and the production cycle of grade transition lengthens.

A kind of grade transition composition prediction method that the embodiment of the present invention provides, comprises the steps:

Stopper is closed when reducing Casting speed to the first pulling rate value;

Judge insertion ferrum plate when pouring basket liquid level height reaches in pre-set level height interval;

After described insertion iron plate, first unwrap greatly and open described stopper after watering and carry out centre and unwrap and water;

In the described pouring basket liquid level rise process that described centre is unwrapped after watering, mix through the first molten steel and water the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of described pouring basket liquid level rise process, after described pouring basket liquid level increases to target tonnage, mix through the second molten steel and water the described alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish;

The qualified rear raw steel kind rolling of slab composition is being forecast according to described alloy element concentration.

Preferably, described mixing through the first molten steel waters the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of described pouring basket liquid level rise process, particularly as follows:

The described alloy element concentration of each time period Mo of described pouring basket liquid level rise process is obtained based on the described alloy element concentration iterative computation that initial time section is last.

Preferably, the described described alloy element concentration iterative computation based on initial time section end obtains the described alloy element concentration of each time period Mo of described pouring basket liquid level rise process, particularly as follows: be iterated calculating based on following iterative formula:

$C_{n+2}=\frac{M_1\×C_{n+1}+M_2\×C_2}{M_1+M_2-M_3};$

Wherein, C_n+2For the described alloy element concentration at current slot end, M₁For the tundish surplus materials total amount of a upper time period Mo, M₂For entering material total amount, M from big packet stream₃Material total amount, C is flowed out for tundish_n+1Described alloy element concentration for a upper time period Mo.

Preferably, described mixing through the first molten steel waters the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of described pouring basket liquid level rise process, particularly as follows: be calculated based on equation below every time:

$C_{\left|n\right|+2}=\frac{\begin{array}{c}(15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-0.237\×A\×7.8\×{\Σ}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8)\\ \×C_{\left|n\right|+1}+18\×C2\×t_n\end{array}}{15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-0.237\×A\×7.8\×{\Σ}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8}$

Wherein, C_|n|+2It is t_nThe described alloy element concentration of time period Mo, A is strand width, V_iFor Casting speed.

Preferably, described mixing through the second molten steel waters the described alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish, particularly as follows: be calculated based on following iterative formula described target tonnage from reaching:

$C_{n+2}=\frac{M_1\×C_{n+1}+M_2\×C_2}{m}$

Wherein, C_n+2For the described alloy element concentration at current slot end, M₁For the tundish surplus materials total amount of a upper time period Mo, M₂For entering material total amount, C from big packet stream_n+1For the described alloy element concentration of a upper time period Mo, m is described target tonnage.

Preferably, described mixing through the second molten steel waters the described alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish, particularly as follows: be calculated based on equation below every time:

$C_{\left|n\right|+2}=\frac{\begin{array}{c}(15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-1\×0.237\×A\×7.8\×{\Σ}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8)\\ \×C_{\left|n\right|+1}+18\×C2\×t_n-0.237\×A\×7.8\×V\×{\Σ}_{i=n}^i{t}_i\end{array}}{70}$

Wherein, C_|n|+2It is t_nThe described alloy element concentration of time period Mo, A is strand width, V_iFor Casting speed.

Preferably, described pre-set level height interval is 250-350mm.

Preferably, described first pulling rate value is 0.15-0.25m/min.

The one or more technical schemes provided in the embodiment of the present invention, at least have the following technical effect that or advantage:

Water, owing to have employed the pouring basket liquid level rise process unwrapped after watering in centre is mixed through the first molten steel, the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of pouring basket liquid level rise process, mix through the second molten steel after pouring basket liquid level increases to target tonnage and water the alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish. Thus prediction obtains the change of each elemental composition of tundish outlet under the premise sampled without strand off-line, slab composition prediction is watered to mixed thus online, avoiding and strand is rolled off the production line that chemical examination is mixed waters this period of waiting time of base composition, efficiently solve existing dowel plate to carry out even watering plate and the technical problem that overstocks in the base storehouse that exists and the production cycle of grade transition lengthens, be effectively increased continuous casting production efficiency.

Accompanying drawing explanation

In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, the accompanying drawing used required in embodiment or description of the prior art will be briefly described below, apparently, accompanying drawing in the following describes is only embodiments of the invention, for those of ordinary skill in the art, under the premise not paying creative work, it is also possible to obtain other accompanying drawing according to the accompanying drawing provided.

Fig. 1 is the flow chart of grade transition composition prediction method in the embodiment of the present invention.

Detailed description of the invention

For making the purpose of the embodiment of the present invention, technical scheme and advantage clearly, below in conjunction with the accompanying drawing in the embodiment of the present invention, technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is a part of embodiment of the present invention, rather than whole embodiments. Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain under not making creative work premise, broadly fall into the scope of protection of the invention.

With reference to, shown in Fig. 1, embodiments providing a kind of grade transition composition prediction method, comprise the steps:

Stopper is closed when S101, reduction Casting speed are to the first pulling rate value.

In specific implementation process, the first pulling rate value is 0.15-0.25m/min. For example, reduce Casting speed to 0.15m/min, and pouring basket liquid level height is when 250-350mm, close stopper. In specific implementation process, pouring basket liquid level height is when 250-350mm, and the Metal Weight in tundish reaches 15-25 ton.

S102, judge when pouring basket liquid level height reaches in pre-set level height interval insertion iron plate.

Specifically, after closing stopper, rapidly tundish car is raised to a high position iron plate is swung in automatically, realize inserting iron plate, but the rising numerical value of hired car is defined between misaligning herein, to facilitate insertion iron plate to be as the criterion, and reduce tundish to normal operation position.

S103, inserting after iron plate, first unwrap greatly and open stopper after watering and carry out centre and unwrap and water.

S104, in the pouring basket liquid level rise process that centre is unwrapped after watering, mix through the first molten steel and water the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of pouring basket liquid level rise process, after pouring basket liquid level increases to target tonnage, mix through the second molten steel and water the alloy element concentration that ingredient prediction model obtains each time period Mo after target tonnage and exports at tundish.

By S104, thus after liquid level rise process and pouring basket liquid level are reached operating fluid level, forecasting slab composition.

Concrete, mix through the first molten steel and water the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of pouring basket liquid level rise process, particularly as follows: obtain the alloy element concentration of each time period Mo of pouring basket liquid level rise process based on the alloy element concentration iterative computation that initial time section is last.

The mixed process of watering is disassembled into n time period, at t₁Time period Mo, M₁×C₁Plus M₂×C₂It is exactly current time tundish surplus materials total amount, by M₁×C₁Plus M₂×C₂As molecule, denominator was " surplus materials total amount in the tundish of a upper time period Mo+enter material total amount-tundish from big packet stream flow out material total amount ", thus obtaining C₃It is exactly the alloy element concentration of the tundish outlet at initial time section end, namely t₁The alloy element concentration that time period Mo exports at tundish. Based on t₁The alloy element concentration of the tundish outlet of time period Mo is iterated calculating, it is possible to obtain t₂～t_nThe alloy element concentration of the tundish outlet of time period Mo, is specifically calculated obtaining the alloy element concentration of each time period Mo of pouring basket liquid level rise process based on following iterative formula every time:

$C_{n+2}=\frac{M_1\×C_{n+1}+M_2\×C_2}{M_1+M_2-M_3};$

Wherein, C_n+2For the alloy element concentration at current slot end, M₁For the tundish surplus materials total amount of a upper time period Mo, M₂For entering material total amount, M from big packet stream₃Material total amount, C is flowed out for tundish_n+1Alloy element concentration for a upper time period Mo.

Specifically see, in order to set up, the first molten steel is mixed waters composition forecast model and the second molten steel is mixed waters composition forecast model, it is 80t below based on middle bag specification, to the first molten steel mixed water composition forecast model and the second molten steel is mixed water composition forecast model needed for variable be defined below: definition starts residue molten steel in tundish and takes 15 tons, certainly being decided to be 15 tons in specific implementation process one, the actual specification according to tundish is determined. Unwrapping greatly and water until when tundish reaches target tonnage (such as target tonnage is 70 tons), the steel-passing amount of big bag is 15-20 ton, the steel-passing amount of big bag takes 18 tons when calculating, and after about 5min, tundish reaches target tonnage. According to rising soon, pulling rate pattern is calculated, and is V at Casting speed₁, V₂, V₃... time each corresponding keep t₁Time period, t₂Time period, t₃Time period .... Pulling rate increases to V from 0m/min₁(V₁For initial pulling rate) time ignore, casting blank section is defined as A × 0.237, and A is strand width.

In tundish, residue molten steel takes 15 ton hour alloy element concentrations and is defined as C₁. In next ladle, the alloy element concentration of molten steel is defined as C₂, the molten steel that next ladle injects is thoroughly mixed with molten steel in tundish, and the alloy element concentration entering crystallizer after mixing is defined below: t₁Time period end is C3, t₂Time period end is C4, t₃Time period end is C5, t₄Time period end is C6 ..., the rest may be inferred.

Then at t₁Time period Mo:

$C_3=\frac{15\×C_1+18\×t_1\×C_2}{15+18\×t_1-V_1\×t_1\×0.237\×A\×7.8}$

Then at t₂Time period Mo:

$C_4=\frac{\begin{array}{c}(15+18\×t_1-V_1\×t_1\×0.237\×A\×7.8)\\ \×C_3+18\×t_2\×C_2\end{array}}{15+18\×{\mathrm{\Σ}}_{i=1}^2{t}_i-0.237\×A\×7.8\×{\Σ}_{i=1}^{2}Vi\×t_i}$

Then at t₃Time period Mo:

$C_5=\frac{\begin{array}{c}(15+18\×{\Σ}_{i=1}^2{t}_i-{\Σ}_{i=1}^2{V}_i\×t_i\×0.237\×A\×7.8)\\ \×C_4+18\×t_3\×C_2\end{array}}{15+18\×{\mathrm{\Σ}}_{i=1}^3{t}_i-0.237\×A\×7.8\×{\Σ}_{i=1}^3{V}_i\×t_i}$

Then at t₄Time period Mo:

$C_6=\frac{\begin{array}{c}(15+18\×{\Σ}_{i=1}^3{t}_i-0.237\×A\×7.8\×{\Σ}_{i=1}^3{V}_i\×t_i)\\ \×C_5+18\×t_4\×C_2\end{array}}{15+18\×{\mathrm{\Σ}}_{i=1}^4{t}_i-0.237\×A\×7.8\×{\Σ}_{i=1}^4{V}_i\×t_i}$

By that analogy, namely before tundish miss the mark tonnage, obtain at t_nTime period Mo:

$C_{\left|n\right|+2}=\frac{\begin{array}{c}(15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-10.237\×A\×7.8\×{\Σ}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8)\\ \×C_{\left|n\right|+1}+18\×C_2\×t_n\end{array}}{15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-0.237\×A\×7.8\×{\Σ}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8}$

Mass percent for every kind of alloying element that each time period Mo calculated after dowel plate exports at tundish, it is only necessary to input C1, C2, strand width A, Casting speed V_i, then iterative computation each alloy element concentration can be gone out successively.

The described alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish is watered in concrete mixing through the second molten steel, particularly as follows: following iterative formula is calculated reaching the alloy element concentration of each time period Mo after target tonnage from reaching target tonnage:

$C_{n+2}=\frac{M_1\×C_{n+1}+M_2\×C_2}{m}$

Wherein, C_n+2For the alloy element concentration at current slot end, M₁For surplus materials total amount, M in the tundish of a upper time period Mo₂For entering material total amount, C from big packet stream_n+1For the alloy element concentration of a upper time period Mo, m is the target tonnage of tundish.

Mix through the second molten steel and water the alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish, particularly as follows: be calculated based on equation below every time, it be specially to calculate through equation below every time and obtain reaching the alloy element concentration that each time period Mo after target tonnage exports at tundish:

$C_{\left|n\right|+2}=\frac{\begin{array}{c}(15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-1\×0.237\×A\×7.8\×{\Σ}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8)\\ \×C_{\left|n\right|+1}+18\×C_2\×t_n-0.237\×A\×7.8\×V\×{\Σ}_{i=n}^i{t}_i\end{array}}{70}$

Wherein, C_|n|+2It is t_nThe alloy element concentration of time period Mo, A is strand width, V_iFor Casting speed, target tonnage is 70 tons.

S105, forecasting the rolling of slab composition qualified rear raw steel kind according to alloy element concentration.

In specific implementation process, pre-set level height interval is 250-350mm, below, based on grade transition composition prediction method provided by the invention, dowel plate is even watered three kinds of slabs of generation: A base, B base and C base, A base rolls according to steel grade before plate, and B base waters base need to sentence useless for mixed, and C base can the rolling of raw steel kind after forecast slab composition is qualified.

No. three test datas that technical scheme based on embodiment of the present invention offer carry out test are given below, and table 1 is the dowel plate process datas of three tests.

1 three process of the test data of table

Table 2, table 3, table 4, table 5 are test the every kind of alloy element concentration obtained three times:

The slab composition information of one tested by table 2

The slab composition information of two tested by table 3

	C	Si	Mn	P
					Before plate, heat judges	[0.05,0.07]	(0.0,0.05]	[0.30,0.50]	(0.0,0.015]
After plate, heat judges	[0.06,0.08]	(0,0.05]	[0.50,0.60]	[0.010,0.025]
					Heat composition before plate	.0574	.037	.3967	.0088
Heat composition after plate	.0674	.0258	.5521	.0147
					C base head composition	0.08	0.03	0.52	0.015
Forecast composition	0.0772		0.51012	0.0138
					Forecast departure	-3.5%		-1.9%	-8.0%

The slab composition information of two tested by table 4

	S	Alt	Nb
				Before plate, heat judges	(0.0,0.012]	[0.030,0.060]	[0.045,0.055]
After plate, heat judges	(0,0.010]	[0.025,0.055]	[0.025,0.035]
				Heat composition before plate	.003	.0502	0.04924
Heat composition after plate	.0032	.0465	0.02742
				C base head composition	0.004	0.036	0.03
Forecast composition			0.02676
				Forecast departure			-10.8%

The composition information of three tested by table 5

	C	Si	Mn	P	S	Alt
							Before plate, heat judges	[0.015,0.040]	(0,0.03]	[0.19,0.26]	(0,0.020]	(0,0.012]	[0.023,0.050]
After plate, heat judges	[0.06,0.10]	(0,0.03]	[0.35,0.45]	(0,0.015]	(0,0.015]	[0.020,0.060]
							Heat composition before plate	.028	.0075	.2114	.0115	.0043	.0424
Heat composition after plate	.0718	.0091	.3747	.0131	.0059	.0464
							C base head composition	0.06	0.01	0.35	0.01	0.005	0.032
Forecast composition	0.06312		0.3724
							Forecast departure	5.2%		6.4%

By table 2, table 3, table 4, table 5 data it can be seen that the grade transition composition prediction method error provided by the embodiment of the present invention is between-11.8～16.5%.

By the one or more technical schemes provided in the invention described above embodiment, at least have the following technical effect that or advantage:

Water, owing to have employed the pouring basket liquid level rise process unwrapped after watering in centre is mixed through the first molten steel, the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of pouring basket liquid level rise process, mix through the second molten steel after pouring basket liquid level increases to target tonnage and water the alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish. Thus prediction obtains the change of each elemental composition of tundish outlet under the premise sampled without strand off-line, slab composition prediction is watered to mixed thus online, avoiding and strand is rolled off the production line that chemical examination is mixed waters this period of waiting time of base composition, efficiently solve existing dowel plate to carry out even watering plate and the technical problem that overstocks in the base storehouse that exists and the production cycle of grade transition lengthens, be effectively increased continuous casting production efficiency.

Although preferred embodiments of the present invention have been described, but those skilled in the art are once know basic creative concept, then these embodiments can be made other change and amendment. So, claims are intended to be construed to include preferred embodiment and fall into all changes and the amendment of the scope of the invention.

Obviously, the present invention can be carried out various change and modification without deviating from the spirit and scope of the present invention by those skilled in the art. So, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.

Claims (8)

1. a grade transition composition prediction method, it is characterised in that comprise the steps:

Stopper is closed when reducing Casting speed to the first pulling rate value;

Judge insertion ferrum plate when pouring basket liquid level height reaches in pre-set level height interval;

After described insertion iron plate, first unwrap greatly and open described stopper after watering and carry out centre and unwrap and water;

In the described pouring basket liquid level rise process that described centre is unwrapped after watering, mix through the first molten steel and water the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of described pouring basket liquid level rise process, after described pouring basket liquid level increases to target tonnage, mix through the second molten steel and water the described alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish;

The qualified rear raw steel kind rolling of slab composition is being forecast according to described alloy element concentration.

2. grade transition composition prediction method as claimed in claim 1, it is characterized in that, described mixing through the first molten steel waters the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of described pouring basket liquid level rise process, particularly as follows:

The described alloy element concentration of each time period Mo of described pouring basket liquid level rise process is obtained based on the described alloy element concentration iterative computation that initial time section is last.

3. grade transition composition prediction method as claimed in claim 2, it is characterized in that, the described described alloy element concentration iterative computation based on initial time section end obtains the described alloy element concentration of each time period Mo of described pouring basket liquid level rise process, particularly as follows: be iterated calculating based on following iterative formula:

$C_{n+2}=\frac{M_1\×C_{n+1}+M_2\×C_2}{M_1+M_2-M_3};$

Wherein, C_n+2For the described alloy element concentration at current slot end, M₁For the tundish surplus materials total amount of a upper time period Mo, M₂For entering material total amount, M from big packet stream₃Material total amount, C is flowed out for tundish_n+1Described alloy element concentration for a upper time period Mo.

4. grade transition composition prediction method as claimed in claim 1, it is characterized in that, described mixing through the first molten steel waters the alloy element concentration that composition forecast model obtains exporting at tundish in each time period Mo of described pouring basket liquid level rise process, particularly as follows: be calculated based on equation below every time:

$C_{\left|n\right|+2}=\frac{\begin{array}{c}\left(15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-0.237\×A\×7.8\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8\right)\\ \×C_{\left|n\right|+1}+18\×C2\×t_n\end{array}}{15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-0.237\×A\×7.8\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8}$

Wherein, C_|n|+2It is t_nThe described alloy element concentration of time period Mo, A is strand width, V_iFor Casting speed.

5. grade transition composition prediction method as claimed in claim 1, it is characterized in that, described mixing through the second molten steel waters the described alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish, particularly as follows: be calculated based on following iterative formula described target tonnage from reaching:

$C_{n+2}=\frac{M_1\×C_{n+1}+M_2\×C_2}{m}$

Wherein, C_n+2For the described alloy element concentration at current slot end, M₁For the tundish surplus materials total amount of a upper time period Mo, M₂For entering material total amount, C from big packet stream_n+1For the described alloy element concentration of a upper time period Mo, m is described target tonnage.

6. grade transition composition prediction method as claimed in claim 1, it is characterized in that, described mixing through the second molten steel waters the described alloy element concentration that ingredient prediction model must reach each time period Mo after target tonnage and export at tundish, particularly as follows: be calculated based on equation below every time:

$C_{\left|n\right|+2}=\frac{\begin{array}{c}\left(15+18\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{t}_i-1\×0.237\×A\×7.8\×{\mathrm{\Σ}}_{i=1}^{\left|n\right|}{V}_i\×t_i-V_n\×t_n\×0.237\×A\×7.8\right)\\ \×C_{\left|n\right|+1}+18\×C2\×t_n-0.237\×A\×7.8\×V\×{\mathrm{\Σ}}_{i=n}^i{t}_i\end{array}}{70}$

Wherein, C_|n|+2It is t_nThe described alloy element concentration of time period Mo, A is strand width, V_iFor Casting speed.

7. grade transition composition prediction method as claimed in claim 1, it is characterised in that described pre-set level height interval is 250-350mm.

8. grade transition composition prediction method as claimed in claim 1, it is characterised in that described first pulling rate value is 0.15-0.25m/min.