| 摘要 |
A method for assigning surplus slabs in slab yards to orders includes loading slab pre-yards of a plurality of production lines with surplus slabs, describing the assignment of the surplus slabs to the orders with a mathematical model, grouping order data and slab data based on steel grades, obtaining an assignment scheme for the surplus slabs and the orders in each group with a mixed scatter search algorithm, and assigning the surplus slabs to the orders using the assignment scheme. If a surplus slab is in a pre-yard of a production line associated with an order the surplus slab is assigned to, the slab is moved using a crane to the production line. Otherwise, the slab is moved to the pre-yard associated with the production line, and then moved using a crane to the production line. The slab is then heated and rolled by the production line. |
| 主权项 |
1. A method for assigning surplus slabs in a slab yard to orders before a hot rolling process, the method comprising steps of:
S50: loading each of slab pre-yards of a plurality of production lines with slabs for rolling; S100: quantitatively describing the assignment of the surplus slabs in the slab yard to the orders before hot rolling process with a mathematical model, said quantitative description comprises choosing decision variables, setting optimization objectives and constraints on the assignments of the surplus slabs, wherein setting optimization objectives includes:
maximizing a hot-charged ratio of slabs that are loaded into reheating furnace loaded at a high temperature, hot slabs with intervals between cutting times when the hot slabs are being cut by a cutting machine and current time less than 12 hours taking precedence to be assigned to an order for rolling using a rolling machine, thereby reducing thermal loss, andminimizing a number of the surplus slabs which are of high steel grade and assigned to the orders requiring lower steel grade, thereby improving the suitability of the steel provided when fulfilling an order; S200: setting parameters of the mathematical model used in the step S100; S300: grouping order data and slab data based on steel grades, each group including slabs with a same steel grade and the orders matching the steel grade of slabs in the group, so that no slab in one group is assigned to an order of another group; S400: obtaining an assignment scheme for the surplus slabs and the orders in each group with a mixed scatter search algorithm; S500: assigning said surplus slabs in the slab yard to the orders before the hot rolling process by using said assignment scheme; S600: determining, according to the assignment scheme, whether a surplus slab, which has been assigned to an order, will stay in a present pre-yard the surplus slab was loaded to; S700: if it is determined in step S600 that the slab stays in the present pre-yard, then moving the slab with a first crane to the production line associated with the present pre-yard for rolling; S800: if it is determined in step S600 that the slab is not staying in the present pre-yard, then moving the slab with a transport unit to a second pre-yard, and then moving the slab from the second pre-yard with a second crane to a production line associated with the second pre-yard for rolling; and S900: heating the slab with a reheating furnace and rolling the slab with a roller of a production line according to the order to which the slab is assigned, the order operating to reduce an energy consumption of the reheating furnace, wherein the mixed scatter search algorithm used in the step S400 for each group further comprises steps of: S401: initializing parameters of the algorithm, setting a value of PSize which is size of initial population consisted of assignment schemes, a value of Maxlter which is a maximum number of iterations, a value of b1 which is a number of the assignment schemes with good qualities in a reference set, and a value of b2 which is a number of the assignment schemes with good dispersity in the reference set, setting an update mark of the reference set NewElements=FALSE, setting a reading of iterations counter Iter=0 and a candidate scheme set AlterSet=Φ; S402: constructing initial population of the assignment schemes with heuristics methods and a randomization strategy respectively; S403: constructing the assignment scheme reference set Refset based on the initial population of the assignment schemes, namely Refset={x1, . . . , xb1, xb1+1, . . . , xb1+b2}, and setting NewElements=TRUE; wherein xi stands for an assignment scheme, i=1, . . . b1+b2; S404: setting the reading of iterations counter Iter=Iter+1, and if Iter>Maxlter or NewElements=FALSE, then proceeding to step S410; otherwise, constructing a scheme subset NewSubsets based on the assignment schemes in the Refset; S405: choosing an assignment scheme subset s in NewSubsets, and combining the assignment schemes in the assignment scheme subset s with a scheme combination method to generate a new assignment scheme xnew; S406: improving the new assignment scheme xnew with a variable depth search strategy to get an improved assignment scheme x′; S407: if the assignment scheme x′ does not exist in the reference set Refset or the candidate set AlterSet, and an objective function value of the assignment scheme x′ is smaller than an objective function value of any assignment scheme in the reference set Refset, then putting said improved assignment scheme x′ into a scheme candidate set AlterSet; S408: deleting the subset s from NewSubsets, and if NewSubsets is empty, then proceeding to step S409; otherwise, executing the step S405; S409: updating the reference set Refset, and if the reference set is updated, letting NewElements=TRUE; otherwise, NewElements=FALSE, and carrying out the step S404; S410: outputting the assignment scheme for the surplus slabs and the orders in the group. |
