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APPLICATION REPORTEN
MEASURING SYSTEMSFOR ROD AND BAR
PROFILE MEASUREMENT OF WIRE ROD IN A MULTIPLE STRAND MILL
ARCELORMITTAL HOCHFELD GMBH
ARCELORMITTAL HOCHFELD GMBH
THE CUSTOMER
ArcelorMittal Hochfeld GmbH operates a 3-strand wire rod mill at the Hochfeld works in Duisburg, Germany. Annual production is 650,000 tons. The billets are supplied from ArcelorMittal Ruhrort GmbH and ArcelorMittal Hamburg GmbH. The production spectrum comprises ball bearing steel, free cutting steel, spring steel, valve steel, and drill steel.
THE BASIC DATA OF THE WIRE ROD MILL ARE
Diameter range: 5.5 to 21.0 mm (0.22” - 0.827”)
Material temperature behind finishing stand: 1,100 °C (2,010 °F)
Rolling speed: up to 70 m/s (13,780 fpm)
THE REQUIREMENTS
Increasingly, the customers of ArcelorMittal Hochfeld GmbH require products with tight dimensional accuracy. To control the H/V rolling process efficiently and to comply with quality assurance require-ments, key dimensions of the rods such as height, width, shoulder sizes and out-of-round must be available in real-time.
The existing oscillating single-axis gauges could neither display the complete profile to determine width and height nor over- or underfill. Therefore samples still had to be cut and measured manually. Furthermore, the samples were not representative for the entire coils. Hence a new profile measurement system became necessary.
The new measurement system should determine diameter and profile along the entire length of the billet to allow optimal crop cuts at head and tail of the billets. The trend towards ever smaller production lots resulting in frequent changes of size and steel grades requires to assess and display the rod diameter and profile in real-time, thus allowing to quickly adjust the mill to roll within the required tolerances. To monitor all 3 strands in parallel and to dis-play profile data independently on 6 terminals, a networked system was needed.
As the rod can break out at any gap of the guides a system with smallest footprint was needed. Therefore only a compact system could be considered.
LARGE BENEFITS FOR THE OPERATORS.
THE SOLUTION
ArcelorMittal Hochfeld GmbH decided to install LAP RDMS systems, because they fulfilled all requirements. In each of the three strands, RDMS gauge heads are located behind the wire rod blocks to obtain results with minimum time lag and to ensure gap-free high precision monitoring of sizes along the entire length of each rod.
LARGE BENEFITS FOR THE MILL
No limit violation can go unnoticed! No other systems provide similar dense readings of the entire rod surface. Deviations and trends are detected immediately. Thus, the operators can take preventive correcting actions even before tolerance limits are violated.
HIGHER DIMENSIONAL ACCURACY
Since the system operates and displays in real time, a glance at the monitors provides the operators with detailed informa-tion about the rolling train status.
Push/pull conditions, roll gap settings and even asymmetric fill of the finishing pass are monitored and can be optimized. Corrective action can be taken immediately to ensure contin-ued dimensional accuracy of the rolled stock.
Repeating dimensional surface defects which originate from roll breaks can be detected immediately, calling for replace-ment of the finishing passes.
HIGHER YIELD AND UTILIZATION
The ramp-up after size or grade changes could be shortened dramatically. Normally, final mill set-up is achieved during run time of a starter bar or the first billet, improving mill utilization.
By optimizing the crop lengths at head and tail the mill yield could be increased, too.
The certitude to quickly roll within tolerances after changes of steel grade or product size has increased considerably
“By using the system we could raise the dimensional accuracy of the shipped wire rod, increase the portion of good product and gain process reliability as well as flex-ibility. We have increased the effective rolling time and thus enhanced the productive time by 1.5 percent. The system has paid for itself in less than a year and allows us to pro-duce better and more profitable.”
DIPL.-ING. GERHARD DYRDEK PRODUCTION MANAGER ARCELORMITTAL HOCHFELD GMBH
DATA MONITORING, PRESENTATION, ARCHIVING
THE HIGHLIGHTS
The measurement system at ArcelorMittal Hochfeld GmbH consists of three gauge heads working independently from each other, connected via an Ethernet network to six independent visualization systems. At any time each terminal can display real-time data from any gauge head or archived data. Through this complete informa-tion, the mill personnel has perfect control over the rolling train, e.g. mill stand and drive settings, slitting and rolling force balance, push/pull conditions, roll wear etc.
THE INFORMATION
The results of all gauge heads are displayed simultaneously in the main control pulpit, in the mill pulpit and at the operator working platform. Following different screens are available:
Cross-section profile graphics plus numerical display of diameters (height and width) and ovality (maximum/minimum/mean value).
Line charts showing diameter of every axis and ovality with precise allocation of the measured results along each rod.
Trend chart showing the last 50 billets with indication of tolerance violations through colour change.
Numerical display with shrinkage compensation considering rolling temperature and grade-specific shrinkage coefficients for precise pre-diction of the cold size.
Furthermore large numerical displays on the mill floor show actual and statistical data. The RDMS software also determines the off-size lengths of the rod head and tail sections allowing optimization of the crop cuts.
SCREENSHOTS OF PROFILE GRAPHICS
SCREENSHOTS OF LINE CHARTS OF DIAMETER AND OVALITY
MULTIPLE DATA DISPLAYS
AUTOMATIC MEASUREMENT AND DATA ARCHIVING
The system is connected to the ArcelorMittal Hochfeld GmbH product data base, receiving customer and product specifi c setup data according to the rolling schedule, thus providing a fully automatic measurement. After each rod, summarized measured data are archived in the product data base. Thus, complete documentation of all rods produced is achieved. Production data can be viewed even after the stock was shipped and customer claims can be analyzed in detail at any time.
Additionally, the local RDMS data base can store all raw data of the RDMS over several months or even years. A systematic offl ine evaluation allows identifi cation of rolling mill fl aws related to specifi c sizes or steel grades.
THE MEASUREMENT PRINCIPLE: TRUE PROFILE POLYGONAL LASER SCAN MICROMETERS
Laser Scan Micrometers synchronously scan the surface of the rolled stock 400 times per second in six axes. This constitutes closely spaced “envelope curves” around the rolled stock, representing size and out-of-round deviations with much higher accuracy than conventional oscillating or rotating shadow gauges.
A 32-bit real-time PC interpolates the complete rod profi le based on the 12 “envelope tangents” and displays height, width, over-/underfi ll, asymmetric fi ll, roll misalignment and the resulting ovality. The measure-ments are carried out 400 times per second in each axis, providing monitoring of the dimensions along the rod with unrivaled density, resulting in precise determination of crop lengths at head and tail. The sensors are mounted stationary in the static gauge heads, eliminating
any moving parts.
LOW COBBLE RISK
The gauge requires a gap of only 10–15 mm between adjacent rod guides, minimizing the risk of rod break-outs.
LOW MAINTENANCE COSTS – HIGH AVAILABILITY
Contamination of the sensors is prevented by an optimized air purg-ing system. Since there are no moving parts, maintenance costs are minimal.
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TECHNICAL DETAILSMESSSYSTEM
Three 6-axes RDMS gauge heads, connected to the PC processing unit by optical fiber cables 400 complete profiles per second, respectively every 175 mm along the rod , at a rolling speed of 70 m/s! Accuracy: better than ±0.020 mm
MECHANICAL SETUP 6 stationary axes per gauge head
MILL-FRIENDLY DESIGN The measurement frame has a length of only 130 mm in rolling direction, requiring a minimal gap of 15 mm or less between entry and exit rod guides. Rugged, cobble resistant gauge head with temperature surveillance incorporating and protecting the sensors. Autonomous air supply using filtered ambient air for air purging and cooling of the measurement frame. Neither compressed air nor cooling water are required. IP 54 rack for PCs and electronics
MEASUREMENT CYCLE AND CALIBRATION Fully automatic measurement or manual operation possible.Start and completion of each measurement cycle by a rod entering resp. leaving the system. Fast and simple on site calibration using certified calibration standards with a magnetic quick-mount holder.
INTEGRATION INTO PRODUCTION Transfer of product parameters and customer data according to the rolling schedule Data transfer to the ArcelorMittal Hochfeld GmbH product data base after each rod
SOFTWARE/COMPUTER ARCHITECTURE Modular Client-Server structure with central server program
MAINTENANCE Availability: virtually 100 % Maintenance: change of air filter cartridges approx. every 3–6 months, depending on the dust load of the intake air.
LAP GmbH Laser ApplikationenZeppelinstrasse 2321337 LueneburgGermanyPhone +49 4131 9511-95Fax +49 4131 9511-96Email [email protected]
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LAP Laser Applications Asia Pacific Pte Ltd Shanghai Representative Office #1903 World Trade Tower 500 Guang Dong Road, Huangpu District Shanghai 200001 ChinaPhone +86 (21)5047-8881Fax +86 (21)5047-8887Email [email protected]
