INSTALLATION OF AN AUTOMATIC SPECTROCHEMICAL LABORATORY
X- RAY 1. INTRODUCTION
The X-ray spectrometry is becoming more and more advantageous in the steel field ana-lysis, specially on alloy steels, due to its speed, fine accuracy degree and good reproductibiiity.
Quantometers or spectrometers are instru-ments which carry out analysis by means of a X-ray spectrum. A radiation detector system is used to measure the spectrum Une intensities.
X-ray quantometers utilize fluorescence spectrum, in some case also a primary spectrum
o
by direct excitation, in the range from 0.36 A to 24 A.
Only the shorter wavelenght portion of this region is transmitted in air; for wavelenghts
o
above 3 A approx., it is necessary to use a vacuum chamber, Helium or Hydrogen atmos-phere.
Most X-ray quan*jmeters, including Pira-tini's one are manufactured with vacuum cham-ber.
With regard to the theoretical analysis aspects it is not our intention to discuss it in this paper because the matter was very well presented during the XXVTŒ A.B.M. meeting on July 1971 by Mr. José Geraldo Gomes Bar-bosa and others in the study "Theoretical Fun-damentals of X-ray Spectrometry with relation to Siderurgical Raw Materials Control".
(Bibliography 1)
We will present in this paper an activity summary to install a spectrochemica) laborato-ry, including specification, calibration, and the previous analysis resiklts.
This equipment is divided into the follow-ing parts:
— One X-ray Quantometer ARL - 72.000
— One Computer: PDP - 11/15
— One Send-Receiver Terminal: ARL - 502
— Four Receiver Terminals: ARL - 500 2. EQUIPMENT SPECIFICATION
Messers. AB BOFORS, know-how and te-chnical assistance suppliers for Aços Finos Pi-ratini, have prepared the following specifi-cation:
— One X-ray spectrometer suitable to work with or without computer, to analyse the following steels, according to Bofors production programmation :
— Group 1 and 2: Carbon and cons-truction steels
— Group 3 and 4: Low-alloy tool steels
— Group 5: High-alloy tool steels
— Group 6: High speed steels
— Group 7 and 8: Ferritic and marten-sitic Chromium steels
The analysis results must be transmitted to the Steel Plant by means of a teletype network.
The spectrometer must have the possibility to analyse the elements in the respective ranges and accuracies, which are shown under the TABLE I.
It was also foreseen the possibility of ana-lyse raw materials and therefore three new elements were included: Fe, Ca and Mg. The total number of elements has so totaled 19, as shown in the specification given by ARL, mentioned under TABLE IE.
The Bofors' specification regarding the Quantometer Laboratory Operation is mentio-ned under FIGURE 1.
3. EQUIPMENT DESCRIPTION Quantometer Unit
The X-ray fluorescence quantometer ARL 72.000, for simultaneous determinations of up to 19 elements, was projected as an indepen-dent unit, to operate connected or not to a computer, and manufactured by APPLIED RESEARCH LABORATORIES S/A, Lausanne, Switzerland (Subsidiary of Bausch e Lomb USA). See FIGURE 2.
It includes:
— Spectrometer assembly is composed of a vacuum chamber to receive X-ray tube, monochromators, external stan-dard, sample chamber, all at constant temperature.
See FIGURE 3.
— X-ray tube with Be end-window, mo-del Machlett OEG75 with Rhodium target, vertically mounted, to operate in 60 KV/50mA or 30 KV/100mA, output 3.0 KVA.
See FIGURE 3.
— One none dispersive monochromator to provide constant integrated inten-sity for reference (external standard).
— Nineteen monochromators, one for each element, provided with 7 different slits, 8 curved christals: LiF, NaCl, SiO2, EDDT, ADP, KAP, Ge, RAP, with two different curve radius.
See FIGURE 4.
— Seven different detectors: multitrons or exatrons, with different filling ga-ses, used for lines K or L.
— High voltage power supply for the X-ray, with complete retified and fil-tered wave, provided with voltage and current stabilizer with 220V ± 0.5%
control panel, overload switch, output of 3.0 KVA with 53 KV X 40mA.
— Two water refrigerated circuits: one of potable water and other one of deio-nized for direct cooling of the anode which is at 50 KV above ground.
— Hydraulic system assembly consisting of rotary pump, control valves etc to move the closing window between va-cuum and sample chambers, and also to bring the samples in exposure po-sition.
— Vacuum system assembly consisting of two vacuum pumps, which maintain the main chamber under constant va-cuum, allowing to evacuate the sample chamber in 5 seconds approx., not dis-turbing the vacuum in the main cham-ber.
— Sample handling device allowing the introduction of 7 samples in a sequency way. Figure 5.
— Reading and measuring section assem-bly by a 2,400 V/15mA for detectors, amplificator to supply electric energy for the integrators, control panel with channel potentiometers, digital volt-meter (DVM) to read the currents accumulated in the integrators.
— Automatic device which allows keep-ing a constant temperature of the whole unit.
(Bibliography 2) Computer System
Process computer system Model PDP-11/15 from DIGITAL EQUIPMENT CORPORATION for controlling and evaluating analysis data from the quantometer — comprising a process computer, interfaced to the quantometer, ter-minal, inter-wiring of »11 units and object program (software).
See FIGURE 6.
(Bibliography 3)
The system has the following functions:
— Preparation of analysis via the termi-nal.
— Control of measurement parameter.
— Control of data output and read-out.
— Real time clock — pulses - from mains - with program interrupt
— Power supply — 230V =b 10%, 47-63 cycles, single phase grounding pro-tection, power consumption about 0.5KW.
One INT-72 Interface Quantometer 72.000 For connecting adaptation unit AUB-72 to computer UNIBUS.
Technical data:
— Design — control and register circuits, input and output amplifiers
— Tranfer Mode — word parallel
— Format — word 1 input: quantometer conditions
word 2 output: analysis conditions word 1 output: channel selection word 2 input: digital voltmeter value One AUB-72 Adaptation Unit 72.000 This unit is inserted into the 72.000 in the place of the programmer (same wiring). It converts the binary information from the com-puter via the interface into the control signals required by the quantometer - and vice versa
(bi-directional).
Technical data:
— Input — selection of 16 analytical conditions, selection of up to 60 channels, control of quantometer
(start, stop, readout)
— Output — DVM signal, quantometer control (general conditions, integr-ation, readout, overscale)
— Connection — 60-pole plug at the quantometer.
One TRP-11 High Speed Tape Reader and Punch
This units is used for fast reading of pro-gram and data tapes
— Automatic correction of measured values.
— Conversation of intensities into con-centrations.
— Inter-element correction.
— Print-out of individual analysis on the terminal.
— Print-out of averaged analysis.
— Print-out of additional data, date and hour.
— Transfer of data to further receivers (optional).
— Program — controlled variation of pa-rameters via the terminal.
— Automatic calibration of the quanto-meter.
The system is composed as follows:
One Process Computer: DPC-11
Central control and process unit: Digital modular computer DPC-11 with 16 - bit parallel - logic, freely programmable.
Program and data are stored in a core memory, picked up by the processor and exchanged via the universal data channel
(U-NIBUS) between computer, interfaces and peripheral units.
Technical data:
— Word length — 16 bit (word byte-and bit-processing)
— Addressing — direct — 32K words or 64K bytes
— Data channel — bi-directional UNI-BUS transfer rate 250K words/sec.
— Registers — 8 universal registers (16 bits)
— Interrupts — automatic priority in-terrupt system for eight program levels
— Memory — core memory 16K words of 16 bits, access time 400 ns, com-plete cycle 900 ns, can be extended externally by blocs to 32K words.
— Control panel — controls and signals for testing and programming
— Power failure protection — protection for program and data in case of power failure — automatic restart into the memory and for punching of program and data tapes from the memory — whenever large memory capacities are used.
Technical data:
— TRP-11 interface — 1/4 system unit in DPC-11 or EMB-01/02
— Speed — reading 300 char./sec.
punching: 50 char./sec.
— Design — 8 channel folding tape, non oiled.
Four AKL-500 Heavy-Duty Data Terminal Heavy-duty 8-channel printer for permanent operation with high working speed and wide carriage.
The input/output terminal comprises the printing mechanism and the keyboard.
It is used for the dialogue with the compu-ter and for the print-out of analytical results.
Technical data:
— Transmission rate — synchronous 30 char./sec, asynchronous 0-30 char./
— Printing width — 13-132 char./linesec.
(adjustable)
— Characters — 64 (10 figures, 27 letters, 26 alpha sign, space)
— Line spacing — 6 Unes per inch
— Paper width — 7.6 to 37.8cm, adjusta-ble up to 6 copies
— Code — 8 channel ISO/ASCH, CCIT No. 5
— Motor — automatic switch on/off
— Printing mechanism — type wheel
with helical movement, with ink roller full, keyboard, solid state contacts
Power supply — 220V ± 10%, 60 cy-cle, single phase, power consumption about 0.5 KW
Other Equipment (Separate Units) One "Kienzle" printer, to use with the quantometer in manual operation.
One "Wattford" power stabilizator, of 9 KVA output and 220V ± 0.5%.
One WKL closed circuit water cooling sys-tem of 144 1/h of water from + 30°C to + 15».
(Bibliography 4)
4. STEEL AND RAW MATERIAL PROGRAMME
The 8 steel group, specified by AB BO-FORS, envolving approx. 120 qualities of steel, to be adopted by PIRATINI in its production line, were re-arranged by APPLIED RESE-ARCH LABORATORIES (ARL) in function of the concentration of elements and inter-element effect, as follows:
Program 01: High chromium steels Chromium-nickel steels Low-alloy and carbon
steels
— Program 04: Tool steels
— Program 02:
— Program 03:
A certain number of BOFORS' steel sam-ples were selected by ARL as representative ones and arranged in the 4 Programs as we can see in the TABLES m , IV, V and VI.
The raw materials were grouped on the following programs:
— Program 11: Slags
— Program 12: Iron ore
— Program 13: Limestone
— Program 14: Dolomite See TABLE VH.
5. ANAYTICAL PROGRAMMATION The analytical programmations is based in a phisio-mathematical model, developed by ARL, which must be calculated by the com-puter for each element to be analysed, as we can see in the FIGURE 9.
The read intensities, comming from the mo-nochromators are recalculated by m^ans of a polynom and transformed in concentrations, taking into account the datas of calibration, the corrected curve of calibration and the inter-element effect.
See FIGURE 10.
The coefficients A, B and C of tht polynom are calculated initially from binary alloys on which the inter-element effect is not significant or by means of the corrected calibration curves.
If the curve is straight A=O.
In cases of standard programme resulting in curves, they are divided in straight parts.
The automatic calibration is made regularly according the Block-diagram of FIGURE 11, by means of calculations of ALPHA and BETA coefficients, which modifies the position of the curve however without changing its form, re-sulting the corrected calibration curves, as we can see in FIGURE 12.
From the corrected calibration curves we can determine the corrected concentrations.
The inter-element effect correction is ne-cessary to compensate the effect due the ra-diation interference of one element to another, resulting into increasing the intensity of one element and consequently decreasing of the other one. This effect is corrected by means of adequated formulas according to the know-how of ARL.
(Bibliography 5, 6 and 7).
In case of PIRATINI's programmation, the adopted procedure was to divide the BOFORS samples (approx. 140) into four groups (i.e.
low alloy, high Cr, high Cr-Ni, tool steel) and to set suitable instrumental sensitivities for these groups.
We than ran all the BOFORS samples
to-gether with a large number of commercially available standards and printed out the inten-sities for each element.
After this, each group was taken sepa-rately and multi-regression analyses were carried out on each element one after the other to determine the basic binary curve and the inter-element coefficients.
Thus once this was completed for any given group the computer provided an equation either linear, or a 2nd degree polynomial which re-presented the binary curve for each element with iron. No graphs were drawn. In addition to this the inter-element coefficients were pro-vided by the computer.
Example
Low Alloy Steels (Group 03) Silicon
For this element there are no inter-element corrections to make and the basic curve ge-nerated by the computer is used directly to calculate the element concentration.
The equation form is:
% Si = a + b ((DVM) + c (DVM)2
a = . + 0.1611531 X lO-i b = + 0.4023157 X 10-3 e = + 0.1155239 X 10-"
Thus for a DVM reading of 1000 digits the percent silicon is
-.01611531 + .4023157 X 10-s (1000)
= -.01611531 + .4023157 + - = -Sfi'ôl + .4023 +
= 0.39% Si
+ .1155239 X 10-9 (100)2 .0001155239
.0001 = .3863 Manganese
This element needs correcting for Cr, Ni, Mo, W, Co and V.
The basic curve is:
% Mn = -.04712296 + .5093138 X 10-3 (DVM) + .1215459 X 10-7 (DVM) 2 The correction coefficients are used in the following equation to correct for the effects
C k % k
Mnc = %MnAp + (DVM) Mn %Cr + k2 k3 %Mo + k4 %w k5 %Co k6 %V were Mn = correct concentration
Mn = apparent concentration Mh obtained using previous graph.
ki correction k2 correction k3 correction k4 correction k5 correction k6 correction
constant for Cr constant for Ni constant for Mo constant for W constant for Co constant for V
.5077083 X 10-6 .9049956 X 10-e .4573602 X 10-5 .1168191 X IO-«
.3796167 X 10-5 .2255871 X 10-5
6. TESTS CARRIED OUT IN LAUSANNE AND CHARQUEADAS
After the equipment conclusion they were tested in ARL's Quality Control Department, Lausanne, Switzerland, with samples of Bureau of Analysed Samples Ltd., and National Bureau of Standards USA. Graphs were drawn showing the good equipment,
(bibliography 8)
In the FIGURE 13 — 17 we can see some curves of a BAS sample.
More than 140 samples of steel, specially prepared by AB BOFORS for this purpose, were run on the quantometer. These tests were assisted by BOFORS and PIRATINI, which have reached good results.
Afterwards, the installation of the quan-tometer on June and December 1973, a new serie of tests were carried out, now in the Central Laboratory, in Charqueadas.
Also very good results were obtained as we can observe on TABLE VIII which was prepared including results from Lausanne, Charqueadas, in comparison with the wet-ana-lysis carried out by BOFORS.
7. INSTALLATION WORKS
The Automatic Spectrometer Laboratory is composed of:
— One X-ray Quantometer ARL Model 72.000 N« 144
— One Digital Computer PDP-11/15
— One Input/Output Data Terminal Mo-del ARL-500
— Four Receiver Data Terminals Model ARL-502
These equipments were transported via highway till Frankfurt and from there to Por-to Alegre airfreighted.
The critical temperature of +43°C, which could damage the cristais of the Spectrometer, was never reached, neither during the trans-port, nor in the Laboratory room, which was already airconditioned.
All equipment was installed and put into operation in approx. 50 days by two technicians from ARL, Switzerland. One wa3 an eletronic specialist and the other one a specialist in computer programming and operation.
During the transport the equipment did not show any kind of alteration so that the positioning of monochromators was not distur-bed and also the calibration was keeped.
Some initial problems arised with the pro-visional power supply of 220 V, 60 Hz had caused troubles, breakdowns and consequently delays. To solve them, a Diesel Generator was utilized for the production of a more stable current.
The Quantometer started to operate, ma-nually by the end of May 1973, the Computer was connected on June and finally on the 7th of July 1973, the whole system after testing, was received by PIRATINI, within the full guarantee of one year.
8. PERSONNEL TRAINING
Quite a lot of emphasis has been done by ARL and PIRATINI to the training of per-sonnel. So, in June 1972, it has been organized by ARL, an exclusive course for operation and maintenance technicians lasting two weeks. It was attended by 1 operation engineer, 1 main-tenance engineer, 2 operations technicians and 1 maintenance technician.
After equipment installation, it was pro-piciated in December 1973, a two week's course, only for maintenance technicians at Charquea-das' Laboratory.
In October 1973 it was propiciated by ARL, in Lausanne, an intensive Programmation Cour-se, during one week for 20 technicians in ope-ration of X-ray quantometers ARL 72.000 to which interested customers of the whole world have been invited. Aços Finos Piratini attended with 1 engineer and 1 technician.
A course to be realized in Charqueadas, with exclusive emphasis to analytical part:
Steels, Briquetts, Pearls and Little Programs have been agreed between PIRATINI and ARL, to take place in 1974.
9. ANALYSIS OF RAW MATERIALS These analysis were foreseen in specifi-cation, manufacture, programming and cali-bration of the Quantometer using basically some domestic raw materials and some foreign.
Domestic raw materials were:
— Limestone
— Dolomite
— Iron Ore
The foreign raw materials were:
— Different kinds of slags.
The chemical analysis obtained from ore and slags were good, permitting the drawing of calibration curves, the same not hapening with the others.
We are strongly engaged into analyse in the wet Laboratory and in the Atomic Absorpt-ion Laboratory many types of slags coming from PIRATINI's steel shop, as well as limes-tone, dolomite and iron ore used in the Steel Works and Direct Reduction Plants.
Regarding the necessary equipment, for pearl and briquetts preparation, they have been brought, installed and tested already.
They are:
— a SCHOEPS-DUISBURG melting set
— a HERSOG-TYPE HTP 60 T hydraulic press
— a BLEULER rotating disc mill We have a few Jernkontorets' slag stan-dards which permits us to determine the exact analytic results already got. We are importing a lot of standardized raw materials from Brit-ish Analysed Standards Ltd., England, and Jernkontorets Institute, Sweden, which mate-rial will allow us to check the whole range of analysis carried out here.
At this ocasion, pearls on base of sodium tetraborate or on lithium of briquetts with additives will be prepared. With these raw ma-terials carefully analysed, it means, standards, it will be possible then to calibrate properly the quantometer.
We hope to reach this aim at the end of July 1974, in order to follow analysing usually the raw materials at the Quantometric Labo-ratory.
10. TECHNICAL SERVICE
This is provided directly by ARL Lausan-ne, sending technicians twice a year in order to carry-out revisions. The one year guarantee provided is total, covering all equipment in-cluding pieces, substitution or reparation.
Air tickets and a local allowance are to be paid by PIRATINI.
The electronic maintenance service of PI-RATINI, that has taken part on a maintenance course in Lausanne and another one in Char-queadas, assumed gradually the whole main-tenance. Eventually letters or telexes are sent or telephonic connections are made, for clear-ing up and guidance in specific cases.
The problems of maintenance up to now were smal and have been caused almost exclu-sively by agents strange to the equipment.
i.e.:
— Disturbance of the electric current (95%)
— Impurities in primary cooling water (4%)
— Excessive dust in the air (1%)
In order to solve the electrical problem, an electronic stabilizer of 15 KVA has already been ordered.
Should this stabilizer not be sufficient, there is available on the market a currente inver ter, including a rectifier and a batery set, that will supply electric power without disturbance or black-outs.
It is foreseen the association of deionization filters to the water supply.
The dust will be reduced to a minimum with the installation of air conditioning in the whole floor cf the Laboratory, with positive prersurization in relation with the external air.
11. COSTS OF ANALYSIS
AC OS FINOS PIRATINI S.A. has already a costs system and through its Cost Depart-ment, since January 1974, is making available the cost of analysis of the Laboratory so that it became possible to present in this paper the real costs of the quantometer analysis:
Month:
Real cost Cr$:
The costs above calculated includes: direct and indirect labor, materials, utilities, mainte-nance, building depreciation and financing in-terests on the equipment. In these equipments there are included instruments for preparing briquetts and pearls and for cutting and
The costs above calculated includes: direct and indirect labor, materials, utilities, mainte-nance, building depreciation and financing in-terests on the equipment. In these equipments there are included instruments for preparing briquetts and pearls and for cutting and