CC BY
8K.N. Shvedov, V.Yu. Rubtsov, I.K. Galimyanov, I.J. Lanovenko
EVRAZ Nizhny Tagil Metallurgical Plant
PRODUCT TRACKING SYSTEM OF THE METALS ROUTE IN THE BALL ROLLING MILL AT RAIL AND BEAM SHOP
Abstract. At the EVRAZ NTMK JSC in rail and beams rolling shop in 2018 years, was building ball rolling mill with high definition of automation. Product tracking system of the metals route in the ball rolling mill at rail and beam shop is devoted in this paper. System see all parameters on technologic process in all time, and all off-spec balls, will not reach the customer, because the system won't enable is make. The mill automation system, made it possible to ensure maximum tracea-bility of the metal, which not only greatly facilitates the work of the site employees, but also provides full feedback to consumers.
Keywords: grinding ball, ball rolling mill, automatic system, tracking of metal movement, process parameters, quenching.
In 2018, a grinding ball rolling mill was launched at EVRAZ NTMK JSC. The ball mill route is characterized by a high degree of automation, which primarily includes 100% tracking of metal movement along the site.
The product tracking system of the ball mill route at the rail and beam shop offers a strict sequential logic and is supported by recording, saving and further analysis of trends for all plant's main equipment units (Fig. 1).
Fig. 1. Ball mill layout: 1 - unbundler with a feeder; 2 - reheating furnace; 3 - hot rolling mill 60 to 120; 4 - temperature equalizer; 5 - quencher; 6 - tempering furnace; 7 - ball sorting tray system
The area's main equipment.
- A reheating furnace (see Fig. 1, position 2; Fig. 2a), the walking beam-type to convey feedstock, fueled by natural gas, an automatic parameter setting system for an energy efficient operation, including gas-air inflow and flue gas outflow control systems, as well as an individual nozzle setting capability. The reheating furnace was designed and manufactured by Forni E Combustione.
- A hot ball rolling mill (see Fig. 1, position 3; Fig. 2b), equipped with hydro mechanical drives for roll gap control, a hydraulic pusher, quick-detachable racks and guides which ensure changeover in less than 40 minutes, and an automation system which offers both continual ball rolling with discarding of scrap (hemi-balls), and an automatic adjustment of the mill to roll a target section with high positioning accuracy of the tools. The mill stand elements offer wide-range adjustments.
- A ball heat treatment plant includes a temperature equalizer (see Fig. 1, position 4; Fig. 2c), a quencher (see Fig. 1, position 5) and a tempering furnace (see Fig. 1, position 6; Fig. 2d).
Fig. 2. Ball mill area:
a - reheating furnace; b - mill stand 60 to 120; c - temperature equalizer; d - tempering furnace
The temperature equalizer has three conveyors with a ball conveyance speed control, as well as a switchover capability from short to long cycle, which ensures that balls are cooled down to the required quenching temperature. The drum-type quenching unit [1], offers a continual process of ball quenching with self-adjustment to a specified mode with a capability to adjust both the temperature. Water flow rate through the use of a closed water cycle through the cooling tower, and the
ball-in-quench soaking time regulation by controlling the rotation speed of the quenching drum [2]. A tempering furnace which has seven heating zones is designed to relieve internal stresses after quenching and impart high performance properties to balls, including impact strength, which is one of the important parameters for standard operation of balls in ball mills which show high dynamic and shock loads. Also, the plant is equipped with an automatic tray-type ball sorter (see Fig. 1, position 7), which offers both sorting by diameter and hardness class and also by heat and individual 'makings' [3].
To understand the whole automatic product tracking system please find below some of the interface parameters. The common interface offers the monitors below and monitoring of the following parameters:
process parameters;
fluid parameters, including automatic sensors, regulators to ensure the required operating parameters of all mechanisms; temperature sensors;
flow meters and automated valves and gates for gas, air, water, nitrogen, power, which offers optimized power consumption of the plant, and prevents equipment overloading; - safety monitoring systems, including automatic interlocks to restrict access to non-operating personnel and protection systems to prevent sudden infiltration into the work area.
Fig. 3 shows the window for access to the main parameters of the ball mill stand. In total, the interface offers access to 17 main units, the tabs provide item-by-item tracking of various systems of each unit, intended for monitoring and setting parameters by various specialists (workers) of the plant (automation, mechanics, electrics, utilities, operating parameters, etc.). Historical data trends of each variable parameter can be pulled out. The total tab number in the area interface exceeds 270, each of which visualizes up to several dozen parameters. General overview of the entire system all at once is unavailable, since over 4000 various parameters are simultaneously recorded and transmitted via AWSs (programmer's workbenches). A schematic overview of the SCADA interface to Ll is the above described plant control/monitoring system. Access to all parameters is restricted just to foremen and IT specialists of the ball mill area. Each operator has access only to the units and equipment within his / her duty.
Fig. 3. The mill control tab screen
Will go into details of just the operating parameters and the material flow through the area. Feedstock is received at the plant as bundles made of one to 100 round billets of the same diameter, single steel grade and single heat. Each bundle has an ID tag / barcode label (Fig. 4a).
a b
Fig. 4. ID tag / barcode label: a - barcode label of a bundle of billets 060 mm; b - ball 060 mm big bag tag
The bundle is placed, onto an unbundler, and the data from the label are entered into the IT system (Fig. 5). Each bar is automatically individually weighed, before being charged into the furnace and the substandard / off-spec bars rejected from the production flow are excluded from the 'making'.
Then the bars are charged into the furnace, and by pointing to each specific bar, you can already get data on its 'making', heat, etc., and its reheating pattern data are also saved. As an example Fig. 4 shows a cursored bar (yellow), with its data shown in window ('making' 2021-09-22 2 includes 63 bars of a total weight of 8.4 tons). The screen also shows other furnace parameters, which can also be displayed as trends.
At the next stage, the material is rolled in the mill, where the bars are recorded piece by piece, the hemi-balls (end crop) produced by rolling are discarded into a box, weighed and the weight of the discard is subsequently deducted from the weight of the 'making'. After rolling, the material is carried over into the quenching plant, where all parameters are also monitored (Fig. 6).
After quenching, balls are carried over to the tempering furnace, where, based on the 'making' data, they run through all zones of the furnace, with all parameters recorded and the trends for each 'making' are saved (Fig. 7) (shown in different colors). By pointing to each conditional cell the 'making' of a given material can be seen, including all parameters and conformance (the balls are deemed conformal unless they have been found deviant during the manufacturing process, including the residence time and temperature value at each stage of the ball heat treatment process).
PK0141909935
Fig. 5. Reheating furnace settings screen
Fig. 6. Heat treatment of balls in a quenching drum
If a non-conformity (delayed material, holdups, temperature deviations) is suspected, the material is deemed allegedly off-spec and is dropped off into an allegedly off-spec material bin.
Then, after going through all the stages of the manufacturing process, the material is automatically packed into big bags, or loaded into a bin, that depends on the further shipment method. Before loading into a big bag (Fig. 8), the hopper scale builds up required weight of balls, depending on the consumer's needs, the weight and the 'makings' are divided into conditional cells (here, in Fig. 8, the weight setting of a cell is 1460 kg). Then based on the real weight of the material, this material is poured into a big bag, or into a hopper.
Fig. 7. Material advancement through the tempering furnace
Fig. 8. Ball pre-packing screen interface
A tag is automatically generated and hung on each big-bag (Fig. 4b) indicating the hardness class, heat number, date and time of packaging, loading position (5 loading positions in total -Fig. 8). After the big bags have been filled up, they are moved into the warehouse. Sample size: 10 balls from each heat for surface hardness test; 2 balls for body hardness test;
2 balls for macrostructure test, and, if necessary (at the request of the customer, where balls hardness class 4 or 5 are manufactured or those intended for export) [4];
- 5 balls are harvested for impact strength and falling weight test and each ball is identified with an indication of the heat number.
After successful passing of all tests, the big bags containing these heats are shipped to the customer, while the big bags barcode is automatically scanned and a draft certificate of shipment to customer is generated. The final certificate is issued only after it has been updated with acceptable test performance values of these heats and the finished products have been weighed in the railcars.
Balls found off-spec and loaded into the allegedly off-spec material bin are also tested on a heat-by-heat basis and, if they show good test performance they are redispositioned. They are subject to the expert review, and distributed to other orders depending on their real properties (for example, hardness downgraded), or if critical deviations have been found and they cannot be further downgraded they are rejected and scrapped.
Should any defective, fractured balls be detected by the customer the balls manufacturing history can be tracked by the big bag ID and to check out the manufacturing modes applied to this 'making'. This being the case, a detailed investigation is carried out, corrective actions are taken and the manufacturing process of the balls made of this steel grade is improved, new modes are put in place, limits are tightened, etc.
Therefore, they are specific for each steel grade and for each ball. In case of deviations from these modes, an error message will pop up on the operator's screen (depending on where the deviation occurred, and afterwards the conditional cell, which contains, the balls will be checked off as 'non-conforming'. They will be automatically redispositioned into the allegedly off-spec material bin. Therefore, the off-spec balls, as well as those to have failed the tests, will not reach the customer, because the system won't enable a clean certificate drafting.
The mill automation system, made it possible to ensure maximum traceability of the metal, which not only greatly facilitates the work of the site employees, but also provides full feedback to consumers.
References
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