Advanced predictive quality control strategy involving different facilities

There are many industries that use highly technological solutions to improve quality in all of their products. The steel industry is one example. Several automatic surface-inspection systems are used in the steel industry to identify various types of defects and to help operators decide whether to accept, reroute, or downgrade the material, subject to the assessment process. This paper focuses on promoting a strategy that considers all defects in an integrated fashion. It does this by managing the uncertainty about the exact position of a defect due to different process conditions by means of Gaussian additive influence functions. The relevance of the approach is in making possible consistency and reliability between surface inspection systems. The results obtained are an increase in confidence in the automatic inspection system and an ability to introduce improved prediction and advanced routing models. The prediction is provided to technical operators to help them in their decision-making process. It shows the increase in improvement gained by reducing the 40 % of coils that are downgraded at the hot strip mill because of specific defects. In addition, this technology facilitates an increase of 50 % in the accuracy of the estimate of defect survival after the cleaning facility in comparison to the former approach. The proposed technology is implemented by means of software-based, multi-agent solutions. It makes possible the independent treatment of information, presentation, quality analysis, and other relevant functions

A multi-source feature-level fusion approach for predicting strip breakage in cold rolling

As an undesired and instantaneous failure in the production of cold-rolled strip products, strip breakage results in yield loss, reduced work speed and further equipment damage. Typically, studies have investigated this failure in a retrospective way focused on root cause analyses, and these causes are proven to be multi-faceted. In order to model the onset of this failure in a predictive manner, an integrated multi-source feature-level approach is proposed in this work. Firstly, by harnessing heterogeneous data across the breakage-relevant processes, blocks of data from different sources are collected to improve the breadth of breakage-centric information and are pre-processed according to its granularity. Afterwards, feature extraction or selection is applied to each block of data separately according to the domain knowledge. Matrices of selected features are concatenated in either flattened or expanded manner for comparison. Finally, fused features are used as inputs for strip breakage prediction using recurrent neural networks (RNNs). An experimental study using real-world data instantaneouseffectiveness of the proposed approach

Validation of Tornio AP3 model based furnace control and grain size calculation

Abstract. Automation for annealing and pickling -line 3 was renewed in 2016, but the model-based control wasn’t good enough that production could rely on it, so doing modifications to the model was necessary. The goal was to get the model working so that automation could control furnaces mostly without input from line operators. Phenomena concerning grain size calculation in the automation system was studied theoretically to acquire sufficient information. The solving of problem was done by inspecting source code for programming errors, examining calculation log files and tables used by automation and finally measuring accuracy of the calculation both statistically and comparing calculated results with measured grain size from production trials. The accuracy was improved by modifying both grain size calculation and set-point calculation. Many changes were suggested for general parameters, grain specific grain growth parameters and source code. After these changes maximum grain size calculation error improved to 0,45 ASTM, but because of poor control of zone temperatures high accuracy in annealing can’t be done. The fixing of automations system is started, and it continues even when this thesis project is finished.Tiivistelmä. Hehkutus- ja peittauslinja 3:n automaatio uusittiin vuonna 2016, mutta uunien mallipohjainen ohjaus ei ollut riittävän hyvällä tasolla, jotta tuotannossa voitaisiin luottaa siihen. Tämän vuoksi mallin validointi oli tarpeellista. Tavoitteena oli saada malli toimimaan siten, että uuneja voitaisiin ohjata pääasiassa pelkästään automaatiolla ilman operaattoreiden panosta. Raekokolaskennan taustalla olevia ilmiöitä ja automaatiota tarkasteltiin kirjallisuuden pohjalta tietopohjan luomiseksi. Ongelmaa lähestyttiin tarkastelemalla lähdekoodia ohjelmointivirheiden osalta, seuraamalla laskennan lokitietoja, tarkastelemalla automaation käyttämiä taulukoita, hyödyntämällä tilastollista tietoa, sekä vertaamalla laskennan tuloksia tuotantokokeiden tuottamaan raekokoon. Laskennan tarkkuutta on mahdollista parantaa modifioimalla sekä raekoko-, että vyöhykkeiden asetusarvojen laskentaa. Laskentaan ehdotettiin useita parannuksia yleisiin parametreihin, laatukohtaisiin rakeenkasvuparametreihin ja lähdekoodiin. Näiden parannusten perusteella laskennan suurin virhe on 0,45 ASTM yksikköä. Tuotantolinjan heikon vyöhykelämpötilan hallinnan takia näidenkään muutosten jälkeen tarkkuutta vaativia hehkutuksia ei voida suorittaa. Automaation korjaus on aloitettu, mutta sitä ei ehditty viemään loppuun tämän projektin puitteissa

Multi-sourced modelling for strip breakage using knowledge graph embeddings

Strip breakage is an undesired production failure in cold rolling. Typically, conventional studies focused on cause analyses, and existing data-driven approaches only rely on a single data source, resulting in a limited amount of information. Hence, we propose an approach for modelling breakage using multiple data sources. Many breakage-relevant features from multiple sources are identified and used, and these features are integrated using a breakage-centric ontology which is then used to create knowledge graphs. Through ontology construction and knowledge embedding, a real-world study using data from a cold-rolled strip manufacturer was conducted using the proposed approach

Influence of surface pretreatment in resistance spot welding of aluminum AA1050

Resistance spot welding (RSW) of aluminum alloys implies a major problem of inconsistent quality from weld to weld due to problems of varying thickness of the oxide layer. The high resistivity of oxide layer causes strong heat development, which has significant influence on electrode life and weld quality. An experimental study of the influence of pretreatment on weld quality in RSW of AA1050 sheets with three thicknesses, comparing welding of as-received sheet with pretreated sheet by either pickling in NaOH or glass-blasting were investigated. Different weld settings were applied with low-, medium-, and high-energy inputs. The as-received sheet showed higher electrical contact resistance because of thicker oxide layer. Lower values were noticed with pickled surfaces, whereas the lowest electrical contact resistance was obtained when glass blasting, resulting in the roughest surface topography, which facilitated breakdown the oxide layer. Highest strength and smaller scatter in strength were obtained by pickling in NaOH

The optimization of the scale growth model for line annealing in stainless steel production

Abstract. The aim of this thesis was to optimize an industrial scale growth model for stainless steel annealing. The focus of the experimental work conducted for this thesis was on the effect of annealing temperature and atmosphere within the annealing furnace on the amount of scale formed during annealing. In addition, the effect of annealing time was studied through the means of microscopy. The results of the experimental work were fitted into mathematical models discovered during the literature review. Thanks to this, the amount of scale formed during annealing can now be predicted thermodynamically. A literature review was performed for this thesis on industrial scale final annealing, the fuels used in industrial scale processes and their effects on e.g., the scale growth during the process and existing mathematical modelling methods and appliances. The experimental work consisted of simulating the annealing of cold rolled AISI 304, AISI 309 and AISI 441 on an industrial scale annealing- and pickling line. The purpose of the experiment was to simulate the scale growth taking place on an industrial scale annealing furnace and gather information on the effect of annealing temperature and atmosphere within the furnace on the amount of scale formed. Studied annealing temperatures ranged between 950–1250 °C and the holding time was 15 minutes. Three different atmospheres were used, simulating the usage of liquid natural gas burned with both air and oxygen enriched air as well as hydrogen burned with oxygen enriched air. In addition, stoppage experiments were conducted on AISI 304 with annealing times of one, five, ten and 15 minutes to study the effect of annealing time on scale growth. The experiments were conducted in a vertical tube furnace, with a weighing scale fixed above the furnace hanging and measuring the mass of the samples. The equipment used for microscopy was a FESEM-EDS. In most cases it was noted, that a higher temperature would cause a higher amount of oxidation. None of the simulated atmospheres were found to cause explicitly more oxidation than the other two between the studied atmospheres, and differences varied from temperature to temperature. A longer annealing time was observed to cause more oxidation, as was expected. When comparing the simulated liquid natural gas burned with air to hydrogen burned with oxygen enriched air as a fuel, no major difference was found in the morphology or depth of the scale formed. The results from experimental work were fitted into functional models. Using the Arrhenius-equation, activation energies and frequency factors could be calculated. These results permit the thermodynamic prediction of the amount of scale formed, and their implementation to an industrial scale.Nauhahehkutuksen hilseenkasvumallin optimointi ruostumattomien terästen valmistuksessa. Tiivistelmä. Tämän työn tavoitteena oli optimoida teollisessa mittakaavassa käytössä oleva ruostumattoman teräksen loppuhehkutuksen hilseenkasvumalli. Työtä varten tehdyn tutkimuksen pääpainoina olivat hehkutuslämpötilan ja hehkutusuunissa vallitsevan atmosfäärin vaikutus hilseenkasvun määrään, jonka lisäksi hehkutusajan vaikutusta hilseenkasvuun tutkittiin mikroskopoimalla. Kokeellisen työn tulokset sovitettiin kirjallisuusselvityksessä löydettyihin malleihin, joiden ansiosta hilseenkasvua pystytään ennustamaan termodynaamisesti. Työtä varten suoritettiin kirjallisuuskatsaus liittyen teollisen mittakaavan loppuhehkutukseen, teollisissa prosesseissa käytettäviin polttoaineisiin sekä niiden vaikutuksista mm. hilseenkasvuun sekä olemassa oleviin matemaattisiin mallinnuskeinoihin ja niiden hyödyntämiseen. Kokeellisessa osuudessa simuloitiin kylmävalssattujen AISI 304, AISI 309 sekä AISI 441 loppuhehkutusta hehkutus- ja peittauslinjalla. Kokeiden tarkoituksen oli simuloida hilseenkasvua tuotantolinjalla ja saada tietoa hehkutusolosuhteiden vaikututuksista muodostuvan hilseen määrään. Hehkutusolosuhteina käytettiin 950–1250 °C lämpötiloja, 15 minuutin pitoaikoja sekä kolmea eri atmosfääriä, jotka simuloivat maakaasun polttoa ilmalla ja happirikastetulla ilmalla sekä vedyn polttoa happirikastetulla ilmalla. Lisäksi AISI 304 ruostumattomalle teräkselle tehtiin pysäytyskokeita, joiden pitoajat olivat yksi, viisi, kymmenen ja 15 minuuttia hehkutusajan vaikutuksen tutkimiseksi. Kokeet suoritettiin pystysuorassa putkimaisessa hehkutusuunissa, ja näytteiden massaa mitattiin jatkuvasti uunin yläpuolelle kiinnitetyn vaa’an avulla. Mikroskopoinnissa käytettiin FESEM-EDS-laitteistoa. Suurimassa osassa tapauksia korkeamman lämpötilan havaittiin aiheuttavan enemmän hapettumista. Yksikään simuloiduista atmosfääreistä ei noussut selkeästi kaikista eniten hapettumista aiheuttavaksi, vaan tilanne vaihteli tapauskohtaisesti. Pidemmän hehkutusajan havaittiin aiheuttavan enemmän hapettumista. Verrattaessa ilmalla poltettua maakaasua ja happirikastetulla ilmalla poltettua vetyä hehkutuksen polttoaineena, ei havaittu merkittävää eroa hilsekerrosten koostumuksen tai syvyyden suhteen. Kokeellisesta työstä saadut tulokset sovitettiin toimiviksi havaittuihin malleihin, jonka tuloksena saatiin laskettua aktivaatioenergiat ja taajuustekijät Arrhenius-yhtälön avulla. Näiden tuloste ansiosta hehkutuksessa syntyvän hilseen määrä pystytään ennustamaan termodynaamisesti, ja tuloksia voidaan sovittaa teolliseen mittakaavaan

A stable and accurate control-volume technique based on integrated radial basis function networks for fluid-flow problems

Radial basis function networks (RBFNs) have been widely used in solving partial differential equations as they are able to provide fast convergence. Integrated RBFNs have the ability to avoid the problem of reduced convergence-rate caused by differentiation. This paper is concerned with the use of integrated RBFNs in the context of control-volume discretisations for the simulation of fluid-flow problems. Special attention is given to (i) the development of a stable high-order upwind scheme for the convection term and (ii) the development of a local high-order approximation scheme for the diffusion term. Benchmark problems including the lid-driven triangular-cavity flow are employed to validate the present technique. Accurate results at high values of the Reynolds number are obtained using relatively-coarse grids

Interfacial oxidation in processing of nanocrystallised metallic materials using duplex technique - experimental and modelling aspects

Duplex techniques are attempted to be developed combining nanocrystallisation processes with a subsequent thermomechanical processing in order to produce multilayered bulk structures with improved yield and ultimate tensile strengths, while conserving an acceptable elongation to failure. However, bonding imperfections at the interfaces due to interfacial oxidation among other reasons during the duplex process can significantly influence the final properties. Moreover, the interface oxidation occurring during duplex processes influences microstructure development around the interfaces depending on whether the oxide scale is a continuous layer or a layer of discontinuous oxide clusters with heterogeneous thicknesses. Effectively the oxide scale becomes a part of microstructure development in such nano-crystallised multilayered structures. This paper deals with understanding of the underlying events around the highly reactive interfaces explaining the microstructure evolution applying advanced experimental and numerical modelling techniques. The research encompassed surface mechanical attrition treatment followed by constrained compression testing and hot rolling of the assembly of steel strips supported by multilevel numerical analysis using combined finite element (FE) and cellular automata (CA) methods. Shear banding has been observed near metal-metal contact between the oxide clusters at the interfaces. The shear banding can be considered as bonding enhancement creating channels for the base metal of the different laminates to come into contact through the oxidised interface. Temperature, texture and grain refining are among the factors influencing the shear banding. In the simulations, the meso-level of the developed multi-level FE-based model is combined with the advanced 3D frontal CA numerical model allowing for both appearance of the new boundaries and rotation of dislocation cells (sub-grains and grains) simultaneously

Influence of hot dip galvanizing on fatigue behavior of welded steel joints

This thesis investigates the effect of hot dip galvanizing (HDG) on fatigue strength of fillet welded S355 structural steels. HDG is a surface treatment that allows protecting components from corrosion, but its effect on the fatigue strength of the welded joint is not well understood. In this thesis, a comparative study has been carried out between hot dip galvanized fillet welded cruciform joints made by S355 and non-galvanized welded joints characterized by the same geometry. Microstructures and the fracture surface of fatigue test specimens have been studied macroscopically and microscopically. The effect of galvanizing on microstructure, penetration of zinc to steel and its effects on initiation of crack has been investigated. Based on conducted fatigue tests, reduction of fatigue strength of galvanized samples comparing to bare metal is not considerable in low cycle fatigue regime. Using scanning electron microscopy (SEM), microstructure investigation has both revealed micro cracks on coating and also the notches located close to the welding toe. A few deep cracks were observed close to the weld notches. In high cycle fatigue regime, these cracks have the ability to propagate and lead to reduction of fatigue limit. Debonding and delamination between coating and substrate, which are potential sites for stress concentration and crack initiation, were observed. Based on this study, it has been concluded that HDG can reduce fatigue limit in high cycle load. Further investigation is needed in this subject