Decrease In Heat Input Research Articles

Effect of heat input on ultrahard Fe-Cr-B-C-W-Mo-Nb hardfacing

Multicomponent alloys (Cr, Mo, W, Nb, C, B) nanostructured iron base with complex carboborides have been developed to provide great protection against abrasive wear to elements of agricultural and mining machines. These overlays are subject to severe material losses due to impact and abrasion of hard particles and therefore optimizing their wear resistance is critical when it comes to their lifespan, increasing it as a result. The objective of this work was to study the influence of heat input on the wear resistance through of the analysis of the solidification rate. In this sense, the increase of welding speed was produced a decrease of heat input and refined of microstructure. In order to explain these effects, an analysis was made of of the influence of welding speed on the geometry of the deposited metal, dilution with the base metal, microstructural evolution and hardness of iron-based nanostructured deposits with complex carbides. For this, four samples were welded with different speeds; these being 1, 2.5, 5 and 12 mm/s. A semi-automatic welding process was used with a 1.6 mm wire rope used to provide gas protection. The chemical composition was analyzed on a dilution free welded sample. For the each welded sample the dilution percentage was determined, the dimensional survey of the beads was carried out and the microstructure was characterized by X-ray diffraction and optical and scanning electron microscopy. In addition, Vickers microhardness tests were measured in the central area of the beads and the microhardness of phases were measured. The dilution of the deposited metals ranged from 17% to a maximum of 28%. A microstructure formed by a matrix with complex metal carbides and carboborides was observed. The hardness of the beads varied between 960 and 1350 HV2. The highest wear resistance was found in the sample with highest speed welding.

Effect of Welding Parameters on Al/Mg Dissimilar Friction Stir Lap Welding with and without Ultrasonic Vibration.

The amount of heat input during welding impacts the weld's thermal and mechanical behavior and the joint's properties. The current study involved conducting AA 6061 and AZ31B Mg dissimilar welding, using friction stir lap welding (FSLW) and ultrasonic vibration-enhanced FSLW (UVeFSLW). The comparison and analysis of the welding load, the weld's macro-microstructure, intermetallic compounds (IMCs), and joint properties were conducted by adjusting the process parameters. The study also examined the effect of ultrasonic vibration (UV) variations on welding heat input. The study demonstrated that it is possible to reduce the welding load by employing UV. Moreover, this impact becomes more pronounced as the welding heat input decreases. Additionally, the material flow in the weld, the width of the weld nugget zone, and the continuous IMC layer are significantly influenced by ultrasonic vibration, irrespective of the heat input during welding. However, the impact on large areas of irregular IMCs or eutectic structures is relatively small. Furthermore, achieving better joint properties becomes more feasible when a higher welding speed is employed for the Al alloy placed on top. Specifically, the impact of UV becomes more evident at higher welding speeds (≥220 mm/min).

Crystallographic texture evolution during friction stir processing of AA7075 alloy

This study investigates the effects of heat input on the crystallographic texture evolution during friction stir processing of AA7075 alloys. Three different heat input levels were applied to develop friction stir-modified regions. Electron backscattered diffraction (EBSD) was utilized to measure the micro-texture in the as-received base metal and friction stir processed (FSPed) stir zones. In particular, inverse pole figure (IPF) maps, pole figures, and orientation distribution functions were employed to compare the micro-textures of different processed regions. The results indicate that as the heat input decreases, the average microhardness of the nugget zone declines, accompanied by an increase in the size of recrystallized grains. The base metal AA7075 exhibits a predominantly rotated cube texture ({001} <110>). After friction stir processing, the stir zone transitions to a rotated cube texture with decreased intensities and the presence of copper texture ({112} <111>). Notably, as the heat input increases, the rotated cube texture transforms into a copper texture.

Monitoring of thermo-cycles in fibre laser welding of duplex stainless steel 2205 sheets and its correlation with microstructures and mechanical properties

The study reports the influence of change in the heat supplied (43 J mm−1 to 18.5 J mm−1) on the microstructures as well as mechanical properties of weld joints obtained by welding of Duplex stainless steel 2205 using fibre laser. In-process thermal monitoring of the molten weld pool was carried out using IR pyrometer. Cooling rates (i.e. solidification and solid) were calculated from the thermo-profiles of weld pool, and it increases with the decrease in heat input. From the optical images, it is observed that columnar grains originated from the fusion zone walls and merged at the center. Since, solidification front velocity is comparable on both sides’ leads to a central edge. Ferrite phase content observed in fusion zone microstructure, increases with the increase in solid cooling rate. The result suggests that the joints fabricated at lowest heat input displayed highest tensile strength. The maximum tensile strength been reported to be 872.5 ± 10.8 MPa, and failure occurred at parent metal. Tensile strength of weld joints of DSS 2205 was found to have improved with increasing cooling rate. Higher cooling rate results in the formation of fine dendritic grains as well as higher ferrite content in the weld metal.

Effect of tool traverse speed on joint line remnant and mechanical properties of friction stir welded 2195-T8 Al–Li alloy joints

Abstract AA2195-T8 Al–Li alloy plates were welded by friction stir welding (FSW) at tool rotational speed of 1,000 rpm and tool traverse speeds (TS) of 100–400 mm·min−1 under three types of butting surface conditions, i.e., (1) without butting surface treatment, (2) butting surface milled, and (3) bead-on-plate welding. The effect of welding heat input and butting surface condition on joint line remnant (JLR) and mechanical properties of friction stir welded 2195-T8 Al–Li alloy was investigated comprehensively. In the stir zone of 2195-T8 FSW joints, there exists JLR composed of alumina-particle arrays and microcracks generated from the initial butting surface, and the morphology of JLR would evolve from smooth to serrate as TS increases. Moreover, as TS increases (i.e., the welding heat input decreases), JLR deteriorates the tensile strength of the 2195-T8 FSW joints, with joints prematurely fracturing along JLR. The fracture mode of 2195-T8 FSW joints was considered to be determined by the lower one between strength of JLR (S JLR) and strength of the lowest hardness zone (S LHZ), and JLR tends to be the fracture path at lower welding heat input. Furthermore, butting surface treatment (milling off oxide layer prior to welding) was found to be able to make the JLR in the 2195-T8 FSW joints less distinct and thus improve S JLR, while fracture along JLR could not be avoided.

HEAT INPUT EFFECT OF THE FCAW PROCESS ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF STRUCTURAL STEEL JOINTS

Flux-cored wires are commonly used in structural and pipeline welding, shipbuilding, offshore constructions, and petrochemical and power generation industries. The higher heat inputs in the multi-pass welding result in shorter production time while considerably changing the properties of the welded joint. In this study, robotic flux cored arc welding with varying heat inputs (between 0.56-2.52 kJ/mm) was performed to determine the effect of heat input on weld microstructure, hardness, tensile properties, and impact toughness in the structural steel joints. Results exhibited that decrease in heat input from 2.52 to 0.56 kJ/mm changed the majority of the microstructure from polygonal ferrite to acicular ferrite. Furthermore, this increased by 56%, 37%, and 47% in yield strength, tensile strength, and hardness values, respectively, while decreasing by 30% and 15% in elongation and Charpy impact test results, respectively. Moreover, all welded joints displayed a satisfying toughness value higher than the requested value of 47 J, even at the test temperature of -50 °C. Finally, it can be concluded that the optimum results were obtained with a heat input of 1.26 kJ/mm, considering the minimum requirements of the AWS A5.20 standard and the expectations in applications.

Features of the Macro-, Micro-, and Fine Structure of the Nickel Superalloy Product Material Formed by the Method of Electron Beam Additive Manufacturing.

In the present work, the products in the form of vertical walls were made of heat-resistant nickel-based superalloy ZhS32 via the method of electron beam additive technology. Unidirectional printing strategy was applied. The effect of heat input and 3D printing strategy on the macrostructure, dimensions, and morphology of microstructure elements was established. It was shown that the additive product material has a directed macrostructure. The only exclusion was the final layer with a thickness of no more than 3.5 mm. The directed macrostructure consisted of dendrites oriented predominantly along the crystallographic direction {001} of the primary dendrite arms. The misorientation of the dendrite axes did not exceed 9 degrees. The angle between the predominant dendrite growth direction and the normal to the substrate was 23 degrees. The average primary dendrite arms' spacing increased monotonically from 16 µm at 5 mm from the substrate to 23 µm in the final layers of the product material (the overall height was 41 mm). It was found that the average size of γ' (Ni3Al)-phase precipitations in the form of nanoscale and submicrocrystalline cuboids varied in the range of 76 to 163 nm depending on the distance from the substrate. The size of γ'-phase precipitations reached a maximum at about 30 mm from the substrate, while in the final layers of the product material, the average cuboid size did not exceed 135 nm. Extreme dependence of the size of γ'-phase precipitations on the height of the product followed from a combination of a given monotonic decrease in heat input and heat accumulation in the product material as it formed, as did additional heat removal by means of radiation during formation of the final layer of the product without re-melting. Chemical elements of the austenitic steel substrate material were not detected in the product material more than 8 mm from the substrate. There were no macrodefects, such as voids, in the entire volume of the product material.

Characterization of Heterogeneous Microstructure and Mechanical Properties of Q345R Welded Joints including Roles of the Welding Process

In this paper, the roles of the welding process on the heterogeneous microstructure and mechanical properties of Q345R welded joints were analyzed by a series of tests, including the preparation of welded joints with different welding processes, optical microscope observation, uniaxial tensile tests, and hardness and impact measurements. The experimental results show that with the increase in welding heat input, the content of pre-eutectoid ferrite and the size of the Weidner structure increased, while the hardness and the impact absorption energy of the weld zone decreased gradually. With the increase in heat input, the volume proportion of eutectoid ferrite in the weld increased from 9.90% to 18.78%; the volume proportion of acicular ferrite decreased from 85.10% to 76.21%. With the decrease in heat input, the volume proportion of eutectoid ferrite decreased from 10.58% to 1.45%, and the volume proportion of acicular ferrite increased from 84.21% to 92.74%. Under the influence of the second welding heat, the first weld zone, the fusion zone and part of the heat-affected zone were re-austenitizing, and the distribution of ferrite and pearlite was more uniform. The hardness value of the former weld was lower than that of the second weld, and the distribution was more uniform. The maximum hardness value of the second weld zone and its corresponding heat-affected zone increased with the increase in depth. The distribution of the yield strength and the tensile strength of welded joints was similar to that of hardness.

Enhancement of tribological and mechanical properties of TiB2 - Co cladded layer developed by tungsten inert gas cladding on AISI 1020 Steel

In the present study, various compositions of TiB2-Co coating were deposited on AISI 1020 mild steel by tungsten inert gas cladding method. In this work, various heat energy of TIG with a fixed travelling speed of 1.5 mm s−1 was used to deposit the coating layer. The aim of this study was to investigate the optimal heat input of TIG to develop a thick layer in terms of coating microstructure and bonding quality. The influence of cobalt addition and current variation on microhardness and wear properties of the cladded layer was also investigated. The metallographic examination and microstructural analysis were investigated by x-ray diffraction, scanning electron microscope (SEM) and energy dispersive spectroscopy. The microhardness and wear rate have been analyzed by Vickers microhardness and dry sliding wear test, respectively. The investigations reveal that the influence of heat input on the wear resistance and hardness of the coated layer was significant. The microhardness value increases with increase in wt.% of TiB2 coating powder when TIG parameter is constant. The microhardness value also increases with decrease in heat input of the TIG when composition of the coating is kept constant. The maximum microhardness value was achieved up to 2563 HV0.1 which was 15 times higher than the substrate hardness value of 170 HV0.1. From the wear test result, it was noticed that the minimum wear rate found was 8.24 × 10–8 g Nm−1 for the coating composed by lower heat input (720 J mm−1) and higher wt.% of TiB2 (90 wt.%).

Research of Drop Formation during Electric Arc Surfacing with the Use of Mechanical Control Impacts on the Electrode

Investigations of the influence of the parameters of mechanical effects on the temperature and mass of electrode metal droplets during electric arc surfacing with electrode materials of various chemical composition and type have been carried out. The main regularities of the process of droplet transfer during melting of a strip electrode with the introduction of control mechanical impacts have been established. The optimal range of the oscillation frequency of the strip electrode end is 40 ÷ 80 Hz, in which the average droplet diameter decreases to 1.3 ÷ 1.5 mm, and the mass to 0.08 ÷ 0.1 g. As a result of the research, it was found that, during electric arc surfacing with a strip electrode, changing the parameters of mechanical control impacts on the strip end allows not only to control the drop transfer frequency, but also to reduce the size and temperature of the electrode metal droplets, ensuring a decrease in heat input into the base metal and the formation of a favorable structure of the deposited weld metal.

Effect of heat input on auxiliary wire GMA-AM TiAl alloys

ABSTRACT In-situ γ-Ti48Al alloys are fabricated using auxiliary wire gas metal arc additive manufacturing in which pure Ti plus Al wires are fused in the arc. This study focuses on the influence of heat input on microstructure and mechanical properties of γ-Ti48Al alloys. As the heat input decreases, the upper part of the homogeneous zone in the middle region always shows α2/γ fully lamellar colonies with the decreased grain size, the dual-phase microstructures in the centric and lower parts gradually transform into fully lamellar colonies, and the volume fraction of α2 phase increases. The average microhardness mainly distributes in the range of 310–490 HV. With a decrease in heat input, the compressive strength in the vertical orientation reduces, and the compression rates in both orientations first decrease and then increase. The fracture morphologies always show a mixed-mode of inter-lamellar and trans-lamellar cleavage fractures.

Research on high efficiency deposition method of titanium alloy based on double-hot-wire arc additive manufacturing and heat treatment

Wire arc additive manufacturing (WAAM) is a promising additive manufacturing technique with growing acceptance in fabricating large size components. In this paper, titanium alloy Ti-6.5Al-2Zr-1Mo-1V (TA15) for double-hot-wire arc additive manufacturing (DHWAAM) was firstly investigated and analyzed in deposition state and heat treatment, mainly including mechanical properties and microstructure evolution. The heat input modes of the two processes are different, the deposition efficiency is doubled and the material processing efficiency is greatly accelerated but the change of mechanical properties is not obvious. The microstructure and mechanical properties were analyzed. Due to the decrease of heat input, the grains of DHWAAM are mainly equiaxed grains, while the grains of WAAM are coarse columnar grains. In addition, in the perpendicular direction to columnar grains growth, tensile specimens have better mechanical properties. Sample with fine αP in the microstructure has better elongation. In the heat treatment, it is found that the heat treatment temperature has a great influence on the mechanical properties under air-cooling conditions. The α in the stress-relieved state is finer than the double-annealed state, which shows better yield strength.

Study of steel-aluminium joining under the influence of current waveforms using advanced CMT process variants

ABSTRACT In the conventional GMAW process, increasing weld deposition increases the heat input, which adversely affects the steel-aluminum joint performance due to the brittle IMC layer growth. In the present work, advanced CMT variants in AA6061-T6 and galvannealed steel joining were investigated. All Fe-Al joints are made at a constant joining speed and wire feed rate with CMT process variants, viz. CMT-Standard, CMT-Advanced, CMT-Pulsed, and CMT-Pulsed-Advanced. The influence of current and voltage characteristics of process variants on the thermal profile, joint profile, IMC layer morphology, and mechanical properties of the joint was studied. The welding arc and molten droplet transfer phenomena were explained using recorded welding current and voltage waveforms synchronized with welding arc images. The FE-SEM, EDS, and XRD analyses were performed to confirm the phases and morphology of the IMC layer. The results show that the localized heating due to positive current pulses in CMT-Pulsed and CMT-Pulsed-Advanced processes affects the IMC layer morphology and induces cracks at the Fe-Al joints’ root, leading to low shear tensile strength. The crack-free joints were observed with the CMT-Standard and CMT-Advanced processes. Also, with an increase in the positive CMT cycle in the CMT-Advanced process, heat input decreases and shear tensile strength increases.

Effect of Laser Welding on In-Vitro Bioactivity Properties of Ti6Al4V Joints

In this study, the Ti6AI4V alloy, which is used as an implant material in the medical field, was joined with the laser welding method at different welding speeds. The bioactivity features of the Ti6AI4V alloy and its samples joined at different welding speeds were determined by immersing in a simulated body fluid (SBF) for 1, 7, 14, 21 and 28 days. The hydroxyapatite (HA) formation on the surfaces of the samples was determined by calculating the weight gain. The weight loss was calculated by removing the HA from the surface after bioactivity testing. The corrosion rates of the samples were also determined according to the weight loss. In addition, the characterization of the HA formed on the surfaces of the samples was performed. As a result of the investigations, it was determined that the increase in laser welding speed, and therefore the decrease in heat input, positively affected the bioactivity and biocorrosion features of the Ti6Al4V laser welded joints. It was determined that the particle sizes of the HAs of the laser weldments increased with lower heat inputs. It was also observed that the amount of HA nucleated on the laser-welded samples increased in accordance with the increase in the laser welding speed. The laser welded samples that were welded at higher welding speeds and therefore at lower heat inputs, exhibited better biocorrosion behaviors.

Effect of heat input on microstructure, mechanical and corrosion properties of electron beam welded zircaloy-4 sheets

The present study reports the effect of heat input on the evolution of microstructure, mechanical properties, and corrosion behavior of electron beam butt welded zircaloy-4 sheet. Joints prepared with lower heat input demonstrated lower peak temperature and higher cooling rate that resulted in narrow fusion zone and heat-affected zone. Fine basket weave Widmanstatten type structure in fusion zone was observed at lower heat input, while at higher heat input, a large columnar grain with coarse parallel plate Widmanstatten type structure was observed. Traces of second phase particles Zr(Cr,Fe)2 were also found in the fusion zone. The tensile strength of all welds was better than the base metal, irrespective of heat inputs. However, the joint prepared with lower heat input demonstrated higher ductility compared to other joints. The dominant mechanism of corrosion was found to be pitting type and it was supposed to be caused by intermetallic precipitation. The extent of corrosion decreased with decrease in heat input. Adhesive wear was found to be the dominant mechanism of wear and the coefficient of friction decreased with the decrease in heat input.

MICROSTRUCTURAL CHARACTERIZATION AND TENSILE PROPERTIES ASSESSMENT OF GTAW WELDED INCOLOY 800H ALLOYS FUEL CLADDING FOR SCWR

Incoloy 800H is one of several candidates for a fuel cladding material in super-critical water nuclear reactor concepts. The objective of this work is to determine the effect of the gas tungsten arc welding (GTAW) process on the microstructure and resulting tensile properties of Incoloy 800H tubes. In this work, GTAW was used to join Incoloy 800H. During welding, the weld thermal cycle produces differently featured heat-affected zone and fusion zone (FZ) microstructures. Microstructural examination revealed that weld-characteristic columnar and equiaxed dendritic structures were formed in the FZ. In comparison with the optimum heat input, both increase and decrease of heat input led to the formation of more columnar dendritic structures in the FZ. The chemical element distribution analysis using scanning electron microscopy/energy dispersive X-ray spectroscopy showed the segregation of Ti in the form of Ti-rich carbides and nitrides; other elements did not display any obvious segregation. Tensile test results revealed that Incoloy 800H alloy welds exhibit an excellent combination of strength and ductility almost equal to the base metal (BM) at the optimum and higher than optimum heat input conditions with full penetration. The welding process has no obvious effect on the microhardness across the whole welding zone. The refinement of grain size and morphology in the FZ can contribute to the improvement in the mechanical properties. As a result, the Incoloy 800H weldment shows the comparable mechanical properties to the BM.

Підвищення тріщиностійкості при аргонодуговому високошвидкісному наплавленні на низькій погонній енергії

The rolling mills are operated under high specific pressures, therefore the rolls are produced from high carbon steel 90HF, prone to hot and cold cracking. Therefore, crack resistance and wear resistance increase is an important scientific and technical problem. An effective way to increase crack resistance is arc and energy concentration, which increase the surfacing process. Arc concentration due to electrode diameter decrease provides increase in magnetic field induction, electromagnetic pressure of compression, pinch effect, the weld pool liquid metal crystallization speed, crack resistance and wear resistance. It also provides droplets and microstructure grinding, welding stresses reduction. It has been established that with the carbon content increase, the heat input decreases, thus ensuring heat input decrease, welding stresses reduction, liquid metal crystallization rate increase, microstructure grinding, the interatomic compression pressure and deposited metal crack resistance increase. The argon-arc high-speed surfacing at low heat input of roll necks with chromium-nickel wire, which provides arc and energy concentration, heat input and welding stresses reduction, crystallization rate increase, microstructure grinding, interatomic distance reduction, the pinch effect and interatomic pressures of compression enhancement, rolls crack resistance, wear resistance and durability increase, has been developed

An assessment of microstructure and mechanical properties of inconel 601/ 304 stainless steel dissimilar weld

The microstructure and the mechanical properties of dissimilar joints between Inconel 601 superalloy and 304 austenitic stainless steel were investigated in this work. For this purpose, gas tungsten arc welding (GTAW) process was performed using an austenitic (ER304) stainless steel filler metal in two modes of pulsed and constant current conditions in pure (99.999%) argon gas. Furthermore, an autogenous welding (without filler metal) procedure was also carried out for comparison. The microstructure of weldments was investigated using optical and scanning electron microscopy. Tensile tests and microhardness measurements were carried out to evaluate the mechanical properties. High vacuum FE-SEM investigations revealed that no segregation has occurred in the weld metal. It was found that a decrease in heat input led to a significant grain refinement in the welds, which improved the mechanical properties. Among the welds fabricated with filler metals, welding with pulsed current resulted in superior mechanical properties. Finally, an excellent strength ductility matching (UTS = 485 MPa and Elongation = 39%) was obtained by autogenous welding procedure.

Microstructural evolution and mechanical property of TC4/304 stainless steel joined by CMT using a CuSi3 filler wire

Abstract To obtain excellent spreadability under lower heat input and optimize interfacial microstructure, the spreading limited factors were analysed in wetting of liquid CuSi3 on 304ss and TC4 plates. At the CuSi3/TC4 joining side, the spreading model changed from diffusion-limited to reaction-limited with the interfacial temperature decreases which caused by the decrease of heat input. In the reaction-limited spreading, a continuously thin reaction layer (∼61 μm) was observed, consisting of Cu + Ti2Cu3 + TiCu4 + Ti5Si3, and TiCu + Ti2Cu + Ti5Si3. In the diffusion-limited spreading, a thin reaction layer was transformed to a thick (∼125 μm) one with intricate phases, containing primarily of Ti5Si3 + TiFe2+Ti2Cu3 + TiCu4, Ti5Si3 + TiCu + AlCu2Ti, and TiCu + Ti2Cu therein. The spreading energy provided by the interfacial reaction (26 kJ/mol) was higher than that provided by the diffusion of Ti atoms in copper (21 kJ/mol), i.e. the spreading rate under 65 A welding current with a 0.783 KJ/cm heat input was greater than that under 70 A with a 0.853 KJ/cm heat input. The rapid spreading with a short residence time at a high temperature could reduce the thickness of the interface layer. At the CuSi3/304ss joining side, CuSi3 droplet could not wet 304ss when the heat input was lower than 0.783 KJ/cm. The wettability was gradually improved with increasing heat input, and the spreading driving force was provided by the diffusion of Fe in liquid Cu. A typical solid solution interface without crack defects presented at the CuSi3/304ss. Under the dual effects of reaction-promoted spreading at TC4 side and diffusion-promoted spreading at 304ss side, a wrap-around joint with high strength (∼407.6 MPa) was formed.

Experimental Study on Monitoring of Heat Input in Continuous CO2 Laser Butt Welding of Dissimilar Thin Steels

In the present study, CO2 laser with the continuous wave was used for the welding of dissimilar thin steels i.e., low carbon steel (LCS) and AISI 304 stainless steel (SS 304). In laser welding, the most significant process parameters are laser power (Plaser) and laser scanning speed i.e., welding speed (V). The heat input per unit length (J/mm) was considered in this study, which was calculated by the Plaser/V ratio. The effect of heat input on mechanical properties, weld bead dimensions and residual deformation was investigated. Micro and macrostructural characteristics of welded samples were evaluated using an optical microscope and EDX system equipped with a scanning electron microscope. Within the present working range of the heat input (i.e., 150 to 300 J/mm), the tensile samples were fractured in the LCS side under a ductile manner. The heat input of 210 J/mm was experienced the full depth of penetration and maximum tensile strength of 387.94 MPa. The fusion zone was exhibited the vermicular δ–ferrite at the dendritic core in the austenite matrix. The LCS was showed the recrystallisation in the heat affected zone (HAZ), whereas the grain coarsening was occurred in SS 304. The dendrites width was found to reduce with a decrease in heat input, which resulted in higher hardness values in the fusion zone. The residual deformation was increased by 26.4% with an increase in the heat input from 150 to 300 J/mm and the extreme deformation of 0.211 mm was obtained at a heat input of 300 J/mm.