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One of the challenges in welding ultrahigh- and high-strength steels is the effect of limited heat input on the production times. As the cooling times of these steels have to be controlled tightly to achieve the desired weld qualities, such as impact toughness, the allowed heat input is low, which translates to reduced material deposition rates. This means that multipass welding is often required to achieve good weld quality. Because multipass welding is often used, the time spent waiting for the weld to cool to the desired interpass temperature, which is usually 100 °C, is often multiple minutes for each weld pass. The trend so far has been that more efficient welding processes have been developed to maximize the material deposition rates without increasing the heat input. Even with these efforts the use of multipass welding is still required. The use of ultrahigh- or high-strength steels reduces the material cost, allows for lighter and thinner structures while reducing transport costs as well. However, the production cost can negate some of these cost savings because of the wasted time due to the aforementioned problems with multipass welding. To establish the feasibility of introducing forced cooling to the welding process, the effect of the cooling on the mechanical properties was studied by conducting tensile, impact, and fatigue strength experiments with Gleeble simulated and with welded specimens. Also, the microstructural differences were studied. The tensile properties were improved when forced cooling was used to cool the weld down to the temperature of 100 °C and the impact toughness was also improved or remained unchanged. The cooling also demonstrated that it may have a positive effect on the fatigue strength of the steel. The grain size was usually reduced due to the forced cooling and larger quantities of lower bainite could be seen in some of the experiments. Overall there were no negative effects caused by the forced cooling on the steel. The external cooling method used was water-cooled copper heat sinks that were placed on top of the steel being welded. This external cooling had the potential to reduce the time it takes for the steel to cool down to 100 °C by 83.6% when 6 mm thick steel was welded. Overall, taking into consideration other processes, such as Setup times, the potential time savings that can be achieved by applying such cooling methods to multipass welding processes is a significant and worthwhile option to consider. Tiivistelmä Hitsausprosesseissa yksi merkittävimmistä ongelmista erikoislujilla teräksillä on saavuttaa riittävän nopeat jäähdytysajat sillä hidas jäähtyminen heikentää hitsin lujuutta. Jäähdytysnopeuksien kasvattaminen vaatii lämmöntuonnin vähentämistä, jolloin hitsipalkojen lukumäärää joudutaan vastaavasti kasvattamaan. Hitsipalkon lämpötila pitää olla esim. 100°C ennen kuin seuraava palko voidaan hitsata päälle. Jäähtyminen saattaa kestää kuitenkin useita minuutteja, jolloin tuotannon tehokkuus kärsii palkojen lukumäärän lisääntyessä. Palkojen määrää on pyritty vähentämään kehittämällä tehokkaampia hitsausprosesseja, mutta siitä huolimatta monipalkohitsausta käytetään yleisesti. Hitsausprosessiin käytetty tehollinen työaika kasvaa jäähtymiseen kuluvan ajan vuoksi ja se kumoaa helposti muutoin optimoidut materiaali- ja kuljetuskustannukset. Tämän tutkimuksen tarkoituksena oli tutkia nopeutetun eli pakotetun jäähdytyksen vaikutusta erikoislujien terästen mekaanisiin ominaisuuksiin sekä selvittää pakotetun jäähdytyksen aikaansaamiseksi kehitetyn laitteiston suorityskykyä ja vaikutusta tuotannon tehokkuuteen. Tutkittujen terästen mekaaniset ominaisuudet määritettiin lujuus-, iskusitkeys- ja väsymislujuuskokein. Lisäksi jäähdytyksen vaikutusta teräksen faasirakenteeseen tutkittiin mikrorakennetarkastelujen kautta. Työssä osoitetaan, että pakotettu jäähdytys paransi hitsien lujuusominaisuuksia kuten myötö- ja murtolujuutta. Lisäksi iskusitkeys kasvoi osalle näytteistä, muiden pysyessä ennallaan. Väsytystestausta tehtiin vain osalle näytteistä mutta niilläkin vaikutus oli positiivinen eli väsymislujuus näytti kasvavan. Teräksen hitsialueen mikrorakenteeseen liittyen, jäähdytys pienensi HAZ-vyöhykkseen raekokoa osassa testeistä, sekä joidenkin terästen kohdalla ala-bainiitin osuus kasvoi selkeästi. Oleellista kokeellisessa osuudessa oli, että jäähdytyksellä ei ollut yhdenkään kokeen kohdalla heikentävää vaikutusta tutkittavan teräksen mekaanisiin ominaisuuksiin. Jäähdytysajat 6,0 mm:n levylle 100°C:een lyhenivät keskimäärin 83,6% käytettäessä hitsin sivulle asetettuja jäähdytysblokkeja. Tämä on merkittävä tekijä tuotannon tehokkuuden kannalta konepajateollisuudessa.

In this study, we present the effect of enhanced cooling on the mechanical properties of a high-strength low-alloy steel (having a yield strength of 700 MPa) following a single-pass weld process. The properties evaluated in this study include uniform elongation, impact toughness, yield, tensile and fatigue strengths alongside the cooling time of the weld. With the steel used in this study, the enhanced cooling resulted in a weld joint characterized with excellent cross-weld uniform elongation, yield and fatigue strength. The intensified cooling reduced the time it takes for the weld to reach 100 °C by around 190 s. Not only the fusion line of the weld was less pronounced, but also the grain size of the CGHAZ was greatly refined as a result of the enhanced cooling. The results indicate that combining external cooling to the welding processes can be beneficial for the studied high-strength steel.

Commercial-scale liquid-biofuel production utilizing forest-based biomass would require feedstock supply from a large geographical area. This work assessed GHG emissions derived from the feedstock supply and transportation chain to three possible commercial-scale biodiesel plant locations in Finland at site-specific level. The supply of 7.2 PJ year-1 (approximately 1 million m3solid) of forest biomass (harvesting residues, stumps, and small-diameter energy wood) was assessed for each location, including four distinct scenarios for truck and railway transportation. Biomass availability and transportation-network assessments were conducted through utilization of geographical information system (GIS) methods, and the GHG emissions were assessed by means of life-cycle assessment (LCA). The results showed that the differences in supply chain GHG emissions between different plant locations can be effectively reduced through use of railway transportation from distant supply areas. Furthermore, the location and availability of biomass in the proximity of a given plant is not a decisive factor in supply-chain GHG emissions or the possible GHG savings to be achieved with energy use of forest biomass based products., Proceedings of the 21st European Biomass Conference and Exhibition, 3-7 June 2013, Copenhagen, Denmark, pp. 1800-1810

The seasonal temperature changes under Nordic climate conditions cause a pronounced variation of the fuel demand, regarding both quantity and quality, in forest bioenergy plants. Peak times occur during winter when limited road accessibility and available fleet capacities may restrict the supply of forest fuel. The present study aims to address these challenges by developing a precision supply scenario for forest fuel to bioenergy plants, meaning supplying the right material at the right time. The precision supply scenario utilises existing data and drying models for predicting the moisture of raw material aiming to improve tactical planning in the supply network. Its potential benefits will be evaluated by comparing it to the business as usual approach by means of object-oriented discrete-event simulation. Subsequently, the influence of a bio oil plant with steady fuel demand on the supply network and the potential for precision supply in the working environment of other Nordic and Baltic countries will be investigated., Proceedings of the 21st European Biomass Conference and Exhibition, 3-7 June 2013, Copenhagen, Denmark, pp. 9-10

This paper gives an overview of the driving forces behind the current technical solutions of forest fuel procurement systems in Finland and Sweden and perspectives on future developments and transfer of experiences to other countries. Focus is in the primary forest residues for energy production including logging residues, stump and root wood, small diameter wood and other wood not in demand by the traditional forest industries. Finland consumed 7.5 mill. m3 forest chips and Sweden 7.6 mill m3 in 2011 . Both countries aim to almost double the use of forest biomass for energy by 2020. Experiences in Finland and Sweden show that forest fuel supply benefits from the integration with industrial wood harvesting: Industrial roundwood and residual forest biomass for energy are often extracted from the same stands and by using the same base machines. According to many feasibility studies, Nordic energy wood technology can be applied in the Baltic countriesand in Central Europe with minor modifications., Proceedings of the 21st European Biomass Conference and Exhibition, 3-7 June 2013, Copenhagen, Denmark, pp. 1-4