Method for optimising the production technology of rolled products

Abstract

The inventive method is used for optimising a hot and/or cold strip mill process. Said method consists in discreetly measuring the technological parameters of a strip milling and the angular rates of the working rollers of mill stands and table rollers, in defining the liner speed of the strip and selecting a specified number of strip sections having an equal length and used for a subsequent averaging of at least three values of technological parameters for each section, in determining the normative part of the length of the strip, which is divided into sections, for a specific range of rolled products, defining useful quality for each section with respect to the averaged values of the technological parameters of the section rolling, comparing the useful quality with prescribed limits, determining the part of the strip length for which the useful quality values lie within prescribed limits and in using said technological parameters as a standard for milling a strip of the same range or for the range close thereto if the thus obtained part of the strip length is equal to or higher than the normative part, or for rectifying the technological parameters if the thus obtained part is lower than the normative part.

Description

FIELD OF THE INVENTION

The invention relates to the art of mechanical treatment of metal by pressure, i.e. to production of rolled products, in particular it relates to controlling of rolling mills and handling of the produced articles in the course of their treatment, and more particularly it relates to the rolling mill's monitoring and adjusting devices that are operable to respond to different variables of the rolled sheets. To a certain extent, the invention relates to auxiliary operations for treatment of metal in the course of rolling thereof.

The invention is particularly intended for optimizing the process of hot and/or cold rolling of strips.

BACKGROUND OF THE INVENTION

Known is the method for adjusting the rolling process, comprising the steps of measuring thickness of a rolled strip, and carrying out the correcting actions as to actuators of the roll drives when a rolled strip thickness deviates from predetermined values (patent RU No. 2125495, assigned to SMS Schloemann-Siemag AG, IPC B 21 B 37/00, 1999). This method provides for measurement of only one parameter, and does not provide for taking into account a change in speed of a rolled strip.

Known is the method for adjusting the rolling process, comprising the steps of measuring the strip rolling process parameters by measuring instruments at a number of points along a mill, and outputting appropriate correcting actions as to actuators (patent RU No. 2078626, assigned to Siemens AG, IPC B 21 B 37/00, 1997). Said method does not include the step of tracking the relationship between the monitored process parameters and particular length values of a rolled strip. For that reason, any exact moment for applying the correcting actions cannot be determined while selecting said correcting actions.

Also known is the method of adjustment of the rolling process, comprising the steps of discretely measuring the monitored strip rolling process parameters at a number of points along a mill, measuring angular velocities of the stand working rolls and table rolls, basing on which measurements a strip linear speed is determined; defining, according to the obtained data, a certain number of equally sized strip sections for subsequent averaging of at least three values of the measured monitored variables at each given section, and determining the required correcting actions as to actuators on the basis of the averaged values of the monitored parameters for a given section (patent RU No. 2177847, cl. B 21 B 37/00, 2002). In the applicant's opinion, this method is the art that is the most pertinent to the claimed invention.

SUMMARY OF THE INVENTION

The invention is based on the concept of continuous, more exactly: quasi-continuous measurement of such process parameters as, for instance, consumer properties of a rolled strip along its length in the course of rolling. These properties can be as follows: ultimate strength (σ_us) yield strength (σ^y), and/or elongation (δ) of a rolled strip, etc.

According to the invention: the monitored parameters are measured when a strips moves under an appropriate sensor, and/or at an appropriate measuring arrangement; further, for excluding a possibility that the measurement results would be affected by any occasional fluctuations of measured quantities, which are inevitable under conditions of high temperatures and large masses of a moving metal, at least three values obtained at adjacent measurement points are averaged, the obtained averaged values of the process parameters of a rolled article are compared with the standard values, and when said quantities do not coincide, the correcting actions are effected at the relevant sections of a mill. Such action may consist in modifying the gap between rolls, or the cooling action.

More particularly, according to the invention, implemented is a method for optimizing the rolling process by way of determination of settings for a mill, provision of sensors and measuring arrangements at a mill (for example, for selecting specimens of a rolled material) to determine parameters of a rolled strip while a strip is moving, to read and automatically process the sensor indications or the sampling results, and for determining the controlling actions to be performed as to the rolling process. Further, the rolling process parameters that should be monitored according to production specification of a given rolled products' batch are preset. The invention also provides for systematic measuring of the preset parameters' quantities in the course of movement of a rolled strip over a rolling mill. In this context, the “systematic” term means as frequent measurements of parameters as the used instruments allow such frequency, or as required by the monitoring conditions. Then, a number or length of sections of a rolled strip are defined; for each one of the sections, values of the rolling parameters' measured quantities should be obtained separately. Under conditions of the Examples described below, number of sections of the 800-meter (at exit) strip was 50 sections, so that, accordingly, one section was 16 m long. After that, the measured quantities relating to a given section of a rolled strip are averaged, the averaged quantities of the measured parameters are compared with the quantities defined in conformity with production specifications of a given batch of rolled articles. When the compared quantities do not coincide to an extent beyond certain tolerances, then the mill settings are corrected for rolling of next strip, in respect of which next strip these steps are repeated. When the comparison result is positive, the existing settings remain for rolling of next strip.

More specifically, the invention further comprises the steps of: discrete measuring of the strip rolling process parameters, measuring of the angular velocities of the stand working rolls and tables rolls, determining the strip linear speeds; defining a certain number of equally sized strip sections for subsequent averaging of at least three values of the measured process parameters at each given section, setting a rated portion of the strip length subdivided into sections; for a given rolled products range, further defining the consumer properties at each one of the rolled strip sections depending on the averaged values of each section's measured process parameters; comparing the defined consumer properties with the preset limits of the consumer properties; defining a strip length portion wherein the consumer properties are within the preset limits, and establishing these process parameters as the primary standard for rolling of strips of the same or proximate product range—when this defined strip length portion is not less than the rated portion, or amending the process parameters on a new strip—when said defined strip length portion is less than the rated one.

DETAILED DESCRIPTION OF THE INVENTION

EXAMPLE 1

The method was carried out at a continuous wide-strip hot mill. Strips 800 m long, made of steel 08nc (semi-killed steel), 4 mm thick, were rolled. Chemical composition of the rolled steel was indicated in the heat log issued by the steel-making unit: Table 1.

	TABLE 1
	Element
	C	Si	Mn	S	P	Al
Content, %	0.09	0.01	0.42	0.023	0.015	0.044

The monitored process parameters were the rolling termination temperature (T_re) and coiling temperature (T_co). For measuring the strip rolling termination temperature, a pyrometer positioned at exit from the last finishing stand in the start of the run-out table was used; and the coiling temperature was measured by a pyrometer positioned upstream of the coiler. The strip temperature downstream of the final roughing stand (the sixth stand, T₆) was measured by a pyrometer positioned in the start of the span between the roughing and finishing groups of the mill stands. Strip thickness was measured by an X-ray thickness gauge at exit from the mill finishing group; strip parameters were measured discretely 10 times/s by pyrometers and thickness gauge. Angular velocities of working rolls of the final finishing stand, final roughing stand, of the run-out table and intermediary tables' rolls were measured by tachometers mounted on the respective drives. Basing on the angular velocity measurements, taking into account diameters of the stands and table rolls, the strip linear speed was measured, which speed had the following values: 2 m/s within the span between the roughing and finishing groups, and 6.5-11.2 m/s downstream of the stands' finishing group. For each one of 50 sections 16 m long, basing on a value of the strip linear speed: a set of the measured values relating to the time, when each one of said strip sections has passed under a relevant sensor, was determined. The number of sections selected in this case was determined, on the one hand, by the response speed of the used measuring systems and actuators and, on the hand, by the required adjustment accuracy. The measured discrete values of instrument indications were averaged for each section. As the averaged values were within the tolerances of the rolled products range, next strips were rolled under the same settings.

EXAMPLE 2

Under the same initial conditions as were used in Example 1, part from the process parameters mentioned in said Example: values of σ (ultimate strength) and δ (elongation) were determined for each one of the strip sections to check them upon their compliance with requirements of the applicable standards (the general standards and those demanded by a customer).

The obtained data are summarized in Table 2.

TABLE 2
				Thickness,	σus
Section No.	T6 ° C.	Trt ° C.	Tco ° C.	mm	MPa	δ, %
1	1097	888	563	3.04	386.7	30.1
2	1095	900	561	2.84	381.6	29.8
3	1088	900	566	2.80	380.7	29.7
4	1081	895	575	2.83	381.5	29.9
5	1073	895	577	2.85	381.1	29.9
6	1064	889	578	2.88	383.7	30.0
7	1061	883	578	2.93	386.5	30.0
8	1064	885	583	2.96	384.7	30.1
9	1069	888	583	2.95	383.3	30.1
10	1075	890	582	2.94	382.6	30.1
11	1078	894	579	2.91	381.2	30.0
12	1080	896	577	2.89	380.7	30.0
13	1081	896	577	2.87	380.7	29.9
14	1080	898	578	2.86	379.6	29.9
15	1079	896	579	2.86	380.3	30.0
16	1078	898	586	2.86	378.2	30.0
17	1077	899	584	2.86	378.1	30.0
18	1077	898	582	2.87	378.9	30.0
19	1077	899	580	2.86	378.8	30.0
20	1078	902	580	2.85	377.4	29.9
21	1078	903	581	2.84	376.8	29.9
22	1077	903	583	2.84	376.4	30.0
23	1074	901	582	2.85	377.5	30.0
24	1070	899	582	2.86	378.4	30.0
25	1068	897	582	2.86	379.3	30.0
26	1068	897	581	2.87	379.5	30.0
27	1070	899	580	2.86	378.8	30.0
28	1074	900	581	2.85	378.1	30.0
29	1077	904	583	2.84	376.0	30.0
30	1080	906	584	2.83	374.9	30.0
31	1082	906	585	2.82	374.7	29.9
32	1082	906	587	2.82	374.3	30.0
33	1082	902	586	2.82	376.4	30.0
34	1079	903	582	2.82	376.6	29.9
35	1077	901	586	2.82	377.0	29.9
36	1078	901	586	2.82	376.8	30.0
37	1078	900	580	2.83	378.3	29.9
38	979	901	585	2.83	377.0	30.0
39	1080	903	590	2.83	375.2	30.0
40	1082	904	590	2.83	374.8	30.0
41	1083	905	589	2.82	374.5	30.0
42	1084	905	590	2.82	374.3	30.0
43	1084	901	590	2.82	376.1	30.0
44	1082	903	590	2.82	375.2	30.0
45	1080	901	589	2.83	376.3	30.0
46	1078	900	599	2.84	375.1	30.1
47	1076	902	602	2.84	373.6	30.1
48	1077	903	601	2.83	373.3	30.1
49	1081	904	603	2.81	372.5	30.1
50	1081	898	644	2.88	368.3	30.6
Tolerance,	1060-1100	880-910	560-590	2.8-3.2	295.4-384.5	>28.5
	(95%)	(95%)	(90%)	(92%)	(92%)	(92%)
Within	100%	100%	90%	100%	94.0%	100%
Tolerance,
Fitness to	yes	yes	yes	yes	yes	yes
use

It follows from Table 2 that the strip length portion wherein the consumer properties' values are within the preset limits, exceeds the strip length rated portion having the consumer properties' values within the preset limits (every rolled product range is rated by the engineering specifications on the basis of previous investigations), i.e. for a given chemical composition of steel, the rolling termination temperature of 886° C. and that of coiling of 680° C. provided the strip mechanical properties required by the applicable standard. These values were subsequently used as the primary standard for strip rolling of the same or proximate range of rolled products (having a proximate metal composition and thickness). For subsequent rolling of strips of the same or proximate product range, the established primary standard was used for setting T_rt and T_ro process values.

EXAMPLE 3

Under the initial conditions of Example 2, strips selected from a group having a somewhat different chemical composition were rolled. Data on the same measurements for this strip are summarized in Table 3.

TABLE 3
				Thickness,	σus
Section No.	T6 ° C.	Trt ° C.	Tco ° C.	mm	MPa	δ, %
1	1082	905	583	2.99	375.5	30.2
2	1076	908	580	2.91	374.6	32.9
3	1070	903	579	2.86	377.1	32.8
4	1068	901	572	2.83	379.2	32.7
5	1068	900	568	2.80	380.4	32.7
6	1069	897	564	2.78	382.4	32.6
7	1071	897	552	2.77	382.8	32.6
8	1072	899	560	2.76	382.2	32.5
9	1074	897	558	2.78	383.4	32.5
10	1074	898	560	2.79	382.6	32.6
11	1074	899	562	2.80	381.8	32.6
12	1074	898	565	2.82	381.8	32.7
13	1074	895	567	2.83	382.8	32.7
14	1072	893	567	2.85	383.7	32.7
15	1072	892	569	2.86	383.9	32.7
16	1073	893	568	2.87	383.6	32.8
17	1075	894	568	2.86	383.1	32.7
18	1075	895	567	2.87	382.8	32.7
19	1076	896	567	2.86	382.4	32.7
20	1076	895	566	2.87	383.0	32.7
21	1075	897	566	2.86	382.1	32.7
22	1075	895	565	2.86	383.2	32.7
23	1073	893	564	2.86	384.3	32.7
24	1068	891	563	2.87	385.4	32.7
25	1065	887	563	2.88	387.2	32.7
26	1066	884	563	2.89	388.6	32.7
27	1068	888	566	2.90	386.2	32.8
28	1071	889	565	2.90	385.9	32.8
29	1072	893	566	2.88	383.9	32.8
30	1073	895	568	2.88	382.7	32.8
31	1073	893	566	2.87	383.9	32.7
32	1071	892	564	2.86	384.7	32.7
33	1068	890	564	2.87	385.6	32.7
34	1066	887	566	2.87	386.7	32.7
35	1067	886	571	2.88	386.3	32.8
36	1068	889	572	2.88	384.7	32.8
37	1068	889	576	2.89	384.0	32.9
38	1069	890	579	2.90	383.1	32.9
39	1068	891	574	2.90	383.5	32.9
40	1067	891	571	2.89	384.0	32.8
41	1064	889	568	2.89	385.4	32.8
42	1060	885	568	2.90	387.3	32.8
43	1057	884	566	2.90	388.1	32.8
44	1058	883	566	2.91	388.5	32.8
45	1065	888	570	2.90	385.5	32.8
46	1074	893	571	2.89	383.1	32.8
47	1085	901	568	2.87	379.9	32.8
48	1094	904	567	2.85	378.7	32.7
49	1100	903	620	2.83	370.1	33.2
50	1100	903	639	2.89	366.8	33.1
Tolerance,	1060-1100	880-910	560-590	2.8-3.2	294.4-384.5	>28.5
	(95%)	(95%)	(90%)	(92%)	(92%)	(92%)
Within	96.0%	100%	94.0%	100%	68.0%	100%
Tolerance,
Fitness	yes	yes	yes	yes	no	yes
to use

Table 3 shows that values of σ_us (ultimate strength) exceed the standard values by 32% of the strip length, while the allowed excessive value is 8%. For this reason, for rolling of next strip of that group, the correcting action to be effected at its relevant sections was modified, and said measurement procedure was entirely repeated so that the needed fitness of the strip's rated portion was provided; then the defined mode was being maintained in the course of rolling of other homogeneous blanks.

INDUSTRIAL APPLICABILITY

The invention can be suitably used first of all for rolling of groups of homogeneous blanks, and also can be used for rolling of single blanks, particularly in the cases when subsequent use of separate portions of a rolled sheet for different purposes or different subsequent processes is anticipated.

Claims

1. A method for optimizing the production technology of rolled products, said optimizing being effected by determination of operation settings of a rolling mill, comprising the steps of: at the rolling mill, positioning sensors and/or measuring arrangements to determine the variables of a rolled strip when said strip moves; reading and computer-aided processing of indications of said sensors and measuring arrangements, and working-out the controlling actions to which the rolling process is to be subjected; said method being characterized in that it further includes the following steps: presetting the rolling process parameters needed to be monitored according to production specifications for a given batch of rolled products; systematic measuring of values of the preset parameters when a rolled strips moves along the rolling mill; presetting a number and/or length of the rolled strip sections, for each of which sections the measured quantities' values of the rolling parameters must be obtained separately; averaging the measured quantities that relate to a given section of the rolled strip; comparing the averaged quantities of the measured parameters with the quantities determined by the production specifications for a given batch of rolled products; correcting the rolling mill's settings for rolling of next strip—when the averaged quantities of the measured parameters do not coincide with the quantities defined by the production specifications for a given batch of rolled products; and maintaining said quantities for rolling of next strip—when said quantities coincide.

2. The method as claimed in claim 1, characterized in that the monitored parameter is the rolling termination temperature (Trt) or coiling temperature (Tco) of a rolled strip, or a combination thereof.

3. The method as claimed in claims 1 or 2, characterized in that it further includes the following steps: discrete measuring of the strip rolling process parameters, measuring the angular velocities of the stand working rolls and table rolls, determining the linear speed of strip movement, and determining a certain number of the equal-length strip sections for subsequent averaging of at least three values of the measured process parameters at each one of the sections, further establishing a rated portion of the strip length, subdivided into sections, for a particular range of rolled products; further determining the consumer properties at each rolled strip section depending on the averaged values of the measured process parameters of each section rolling; comparing the determined consumer properties with the preset limits of consumer properties; determining a portion of a strip length wherein the consumer properties' values are within the preset limits; and establishing these process parameters as the primary standard for the same or proximate products range—when said determined strip length portion is not less than the rated portion, or amending the process parameters on a new strip—when said determined strip length portion is less than the rated one.