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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

An experimental study for determining human discomfort response to roll vibration

An experimental study using a passenger ride quality apparatus (PRQA) was conducted to determine the subjective reactions of passengers to roll vibrations. The data obtained illustrate the effect upon human comfort of several roll-vibration parameters: namely, roll acceleration level, roll frequency, and seat location (i.e., distance from axis of rotation). Results of an analysis of variance indicated that seat location had no effect on discomfort ratings of roll vibrations. The effect of roll acceleration level was significant, and discomfort ratings increased markedly with increasing roll acceleration level at all roll frequencies investigated. Of particular interest, is the fact that the relationship between discomfort ratings and roll acceleration level was linear in nature. The effect of roll frequency also was significant as was the interaction between roll acceleration level and roll frequency.

Leatherwood, J. D.↗
DOE OSTI2019

Analysis of Hot- and Cold-Rolled Loads in Medium-Mn TRIP Steels

The purpose of this work is to investigate the hot- and cold-rolling requirements to produce third-generation advanced high-strength steels (AHSS). Therefore, five medium-Mn (10 to 14 wt pct Mn) alloys that exhibit transformation-induced plasticity (TRIP) were compared to a commercially produced grade of AISI 1018 using hot- and cold-rolling experiments. Experimental data collected from a STANAT instrumented rolling mill was utilized to measure force and torque during hot- and cold-rolling. Experimental data were processed by a 1D analytical model, based on Orowan model, to determine rolling pressure. It was determined that pressures required to hot-roll TRIP alloys are 1.4 to 1.8 times greater than pressures for rolling AISI 1018 steel. Cold rolling of the medium-Mn TRIP steels was found to be 1.5 to 2.8 times greater than the AISI 1018 steel. Mechanical and microstructural characterization was also performed and the variation in rolling pressure was related to the starting microstructural constituents, and alloys containing greater starting quantities of ε-martensite in the microstructure had higher flow stresses at equivalent rolling strains during cold rolling.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of rolling processes on ridging generation of ferritic stainless steel

Highlights: • The effects of microstructural refinement and texture on ridging are analysed. • Optimal reduction during cold rolling benefits the enhancement of ridging resistance. • A Steckel-mill rolling method is proposed to improve ridging resistance of FSS 430. • 30% of ridging height reduction can be achieved with proposed rolling method. - Abstract: In order to reduce the ridging generation of ferritic stainless steel (FSS) during forming process, the crystallographic texture of the FSS was modified by optimisation of both rolling and annealing processes. A systematic study was carried out to improve the ridging resistance of the FSS by investigating the sequential changes in microstructure and texture during different rolling and annealing processes. The results show that the surface roughness of the final sheet strained by 20% along the rolling direction is decreased by 20% to 30% using Steckel-mill rolling compared to traditional tandem rolling. A direct correlation is found between the ridging resistance of the FSS and the rolling routines. It has been observed that an optimal reduction value during cold rolling process is critical to the microstructural refinement and surface quality improvement of the FSS. Reduction of the fraction of {001} <110> component by optimisation of the rolling processes is found to be effective in reducing the ridging height of the FSS during the formation process.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Roll Casting of Al-25%Si

Strip casting of Al-25%Si strip was tried using an unequal diameter twin roll caster. The diameter of the lower roll (large roll) was 1000 mm and the diameter of the upper roll (small roll) was 250 mm. Roll material was mild steel. The sound strip could be cast at the speeds ranging from 8 m/min to 12 m/min. The strip did not stick to the roll without the parting material. The primary Si, which existed at centre area of the thickness direction, was larger than that which existed at other area. The size of the primary Si was smaller than 0.2 mm. Eutectic Si was smaller 5 {mu}m. The as-cast strip was ranging from 2 mm to 3 mm thick and its width was 100 mm. The as-cast strip could be hot rolled down to 1 mm. The hot rolled strip was cold rolled. The primary Si became smaller and the pore occurred around the primary Si after the rolling.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of strain on the formation of cold-rolling and grain growth textures of an equiatomic HfZrTiTaNb refractory high entropy alloy

Highlights: • Effect of strain on Texture formation is reported in HfZrTiTaNb for the first time. • Cold-rolled microstructure shows high density of deformation heterogeneities. • Weak texture compared to other BCC phases in HEAs • Imposed strain does not affect texture significantly unlike other BCC materials. - Abstract: The effect of cold-rolling strain on the evolution of deformation and grain growth textures in an equiatomic HfZrTiTaNb refractory high entropy alloy (RHEA) was investigated. For this purpose, the development of microstructure and texture was compared in 50% and 90% cold-rolled materials. The development of deformation microstructure was accompanied by the formation of extensive deformation heterogeneities. The 90% cold-rolled material showed ultrafine lamellar regions as well as regions severely fragmented by the fine scale deformation heterogeneities. The 50% cold-rolled material showed dominant ND-fiber (ND//), while the 90% cold-rolled material showed presence of both RD (RD//) and ND-fiber components. Profuse deformation heterogeneities presumably weakened the deformation texture considerably. The annealing texture of the 50% and 90% cold-rolled material showed stronger {111} component. Comparison of the annealing texture of the 50% and 90% cold-rolled materials with other BCC HEA phases indicated much weaker texture. The annealing texture of the RHEA was not significantly strengthened by increasing cold-rolling strain, presumably due to the high density of deformation heterogeneities in the cold-rolled microstructure. Thus, deformation heterogeneities significantly influenced the formation of cold-rolling and annealing textures of the equiatomic HfZrTiTaNb RHEA.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Computer-aided analysis and design of the shape rolling process for producing turbine engine airfoils

Mild steel (AISI 1018) was selected as model cold-rolling material and Ti-6Al-4V and INCONEL 718 were selected as typical hot-rolling and cold-rolling alloys, respectively. The flow stress and workability of these alloys were characterized and friction factor at the roll/workpiece interface was determined at their respective working conditions by conducting ring tests. Computer-aided mathematical models for predicting metal flow and stresses, and for simulating the shape-rolling process were developed. These models utilize the upper-bound and the slab methods of analysis, and are capable of predicting the lateral spread, roll-separating force, roll torque and local stresses, strains and strain rates. This computer-aided design (CAD) system is also capable of simulating the actual rolling process and thereby designing roll-pass schedule in rolling of an airfoil or similar shape. The predictions from the CAD system were verified with respect to cold rolling of mild steel plates. The system is being applied to cold and hot isothermal rolling of an airfoil shape, and will be verified with respect to laboratory experiments under controlled conditions.

Lahoti, G. D.↗
NASA NTRS1985

Wind-tunnel investigation at supersonic speeds of a remote-controlled canard missile with a free-rolling-tail brake torque system

Wind tunnel tests were conducted at Mach numbers 1.70, 2.16, and 2.86 to determine the static aerodynamic characteristics of a cruciform canard-controlled missile with fixed or free rolling tailfin afterbodies. Mechanical coupling effects of the free-rolling-tail afterbody were investigated by using an electronic electromagnetic brake system providing arbitrary tail-fin brake torques with continuous measurements of tail-to-mainframe torque and tail roll rate. Remote-controlled canards were deflected to provide pitch, yaw, and roll control. Results indicate that the induced rolling moment coefficients due to canard yaw control are reduced and linearized for the free-rolling-tail (free-tail) configuration. The canards of the latter provide conventional roll control for the entire angle-of-attack test range. For the free-tail configuration, the induced rolling moment coefficient due to canard yaw control increased and the canard roll control decreased with increases in brake torque, which simulated bearing friction torque. It appears that a compromise in regard to bearing friction, for example, low-cost bearings with some friction, may allow satisfactory free-tail aerodynamic characteristics that include reductions in adverse rolling-moment coefficients and lower tail roll rates.

Blair, A. B., Jr.↗
NASA NTRS2008

GRCop-84 Rolling Parameter Study

This report is a section of the final report on the GRCop-84 task of the Constellation Program and incorporates the results obtained between October 2000 and September 2005, when the program ended. NASA Glenn Research Center (GRC) has developed a new copper alloy, GRCop-84 (Cu-8 at.% Cr-4 at.% Nb), for rocket engine main combustion chamber components that will improve rocket engine life and performance. This work examines the sensitivity of GRCop-84 mechanical properties to rolling parameters as a means to better define rolling parameters for commercial warm rolling. Experiment variables studied were total reduction, rolling temperature, rolling speed, and post rolling annealing heat treatment. The responses were tensile properties measured at 23 and 500 C, hardness, and creep at three stress-temperature combinations. Understanding these relationships will better define boundaries for a robust commercial warm rolling process. The four processing parameters were varied within limits consistent with typical commercial production processes. Testing revealed that the rolling-related variables selected have a minimal influence on tensile, hardness, and creep properties over the range of values tested. Annealing had the expected result of lowering room temperature hardness and strength while increasing room temperature elongations with 600 C (1112 F) having the most effect. These results indicate that the process conditions to warm roll plate and sheet for these variables can range over wide levels without negatively impacting mechanical properties. Incorporating broader process ranges in future rolling campaigns should lower commercial rolling costs through increased productivity.

Loewenthal, William S.↗
DOE OSTI2018

Roll Compaction of Powdered Radioactive Wastes - 18251

Most of low- and intermediate-level radioactive wastes must be solidified by a proper binding matrix and disposed at the centralized disposal site. So it is desirable to achieve a high loading of radwastes in a drum to reduce the disposal fee while meeting both the national regulations and the waste acceptance criteria of the disposal site. In general, the radioactive wastes (liquid, dried powder and sludge) were solidified by mixing with a proper binding matrix (cement, polymer, asphalt, etc.), but their solidified volume inevitably increases due to the limitation of incorporating of radwaste into a binding matrix. To solve this problem, some Korean NPPs operate both a CTS (Concentrate Treatment System, evaporation and granulation) and a polymer solidification system. The size distribution of granulated wastes produced by CTS is so broad (diameter; several μm ∼ several cm) that a polymer cannot impregnate the void space between particles due to their small size. However, if the powdered radwaste can be compacted into high density pellets, and the pellets can be loaded in a drum with maximum waste loading, then the binding matrix can fill the void between pellets, it might be more desirable to keep the size distribution of pellets constant to reduce the solidified waste volume. This compaction methodology can greatly reduce the disposal fee due to the reduction of the solidified waste volume, and can facilitate polymer solidification due to the constant size of the radwaste pellets. This methodology is also applicable to solidify powdered wastes such a depleted uranium used as a catalyst, ash and sludge. Loading radwaste compacted with bentonite pellets versus particles into a container serves, as an engineered or natural barrier in a deep geologic disposal system. Roll compaction is a typical agglomeration process for dry powders and depends on the device parameters and the material properties. This study, firstly, was focused on the design of roll compactor (briquetting machine), the shape and size of pellet, and secondly the loading method of pellets into a drum, their solidification in polymer, and evaluating the overall volume reduction. We used bentonite (particle size; 85 ∼ 100 μm) as a material to be compacted instead of radwaste powders (concentrates and depleted uranium wastes) without the addition of agglomeration agents. In the design of roll, we considered the diameter (200 mm) and width (41 mm) of roll, two types of pocket shapes (< 9 mm, 0.275 ml), and the surface of the pocket. Fig. 2 shows two pellet shapes, tetragonal and circular. The pressure of roll compactor, one of the main process variables, is > 320 kg f/cm{sup 2}, and the roll gap is 0.5 mm. The powders are compacted in a compaction zone between two counter-rotating rolls according to the complicated mechanisms. As a result of the state and the apparent density of the pellets obtained by changing the pressure from 0 to 286 kg f/cm{sup 2}, the pellets were unstable at pressure=0, but above 148 kg f/cm{sup 2} the pellets were more stable, and the apparent density of the pellets was 2.63 g/cm{sup 3} at 148 kg f/cm{sup 3}, and 2.68 g/cm{sup 3} at 286 kg f/cm{sup 2}. The roller speed (rpm) can determine the capacity (kg/h) of a compactor, and depends on both the compaction pressure and the feeding rate. By increasing the roll speed from 2 to 4 rpm, the apparent density of pellets was decreased gradually from 2.74 g/cm{sup 3} to 1.45 g/cm{sup 3}. We designed the special feeding system in order to feed powders uniformly to the roll gripping zone and to supply powders into the narrowest part of the roll gap. At a constant roll speed (3 rpm) and a constant compaction pressure (286 kg f/cm{sup 2}), the apparent density of the pellets was linearly proportional to the feeding rate from 2.18 to 2.74 g/cm{sup 3} by changing the feeding rate of powders from 8 to 12 rpm. In the polymer solidification of the obtained pellets, we used epoxy resin as a solidification agent, and showed their solidified waste forms in Fig. 5. The incorporation ratio (wt.%) of powders/polymer was about 71.7/28.3 in tetragonal pellets, 71.9/28.1 in circular pellets. We calculated the volume reduction in an aspect of powders itself and the solidified waste form. In powder case, through the comparison of the apparent density of the obtained pellets (2.74 g/cm{sup 3}) and raw powders (0.93 g/cm{sup 3}), the volume reduction was calculated as about 2.74/0.93 = 2.95 times. This means that powders can be compacted to 1/2.95 times. And in waste form case, the weight ratio of powder/polymer in a mixing method (workable) and a compaction method is about 0.42, 2.56, individually. Therefore the volume reduction was calculated as about 2.56/0.42 = 6.01 times. We found a compaction methodology for the volume reduction of powdered radioactive wastes, and their polymer solidification will be more effective to reduce the volume of radwastes to be disposed. After a characterization of the solidified waste form incorporated pellets (including sintered pellets), this methodology will be applied to treat depleted uranium wastes used as catalyst, and to solve the problem of NPPs' polymer solidification system, as mentioned above. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Effect of deformation path on microstructure, microhardness and texture evolution of interstitial free steel fabricated by differential speed rolling

This paper reports the effect of the deformation path on the microstructure, microhardness, and texture evolution of interstitial free (IF) steel processed by differential speed rolling (DSR) method. For this purpose, total height reductions of 50% and 75% were imposed on the samples by a series of differential speed rolling operations with various height reductions per pass (deformation levels) ranging from 10 to 50% under a fixed roll speed ratio of 1:4 for the upper and lower rolls, respectively. Microstructural observations using transmission electron microscopy and electron backscattered diffraction measurements showed that the samples rolled at deformation level of 50% had the finest mean grain size (∼ 0.5 μm) compared to the other counterparts; also the samples rolled at deformation level of 50% showed a more uniform microstructure. Based on the microhardness measurements along the thickness direction of the deformed samples, gradual evolution of the microhardness value and its homogeneity was observed with the increase of the deformation level per pass. Texture analysis showed that, as the deformation level per pass increased, the fraction of alpha fiber and gamma fiber in the deformed samples increased. The textures obtained by the differential speed rolling process under the lubricated condition would be equivalent to those obtained by the conventional rolling. - Highlights: • Effect of DSR deformation path on microstructure of IF steel is significant. • IF steel rolled at deformation level of 50% has the ultrafine grains of ∼ 0.5 μm. • Rolling texture components are pronounced with increasing deformation level.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Microstructural evolution in an ultra-fine YAl{sub 2p} reinforced Mg–14Li–3Al composite during warm-rolling

The YAl{sub 2p}/MgLiAl composite prepared by stir casting was initially forged and then rolled at 200 °C to different thicknesses. The microstructural evolution in the composite during warm rolling was investigated by using transmission electron microscope (TEM). It is found that increasing rolling reduction is conducive to the uniform distribution and refinement of the YAl{sub 2} particles. The rolling deformation promoted the precipitation of an α phase, and the α precipitate is semi-coherent to the matrix with an orientation relationship to the β matrix as: (0002){sub α}‖(110){sub β}. In addition, many nano-sized YAl particles with a cubic shape were found in the matrix of the composite with a high rolling reduction due to the diffusion of Y from YAl{sub 2} to the matrix, which reacted with the Al in the matrix during warm rolling. - Highlights: • The reinforcement YAl{sub 2} particles were distributed more uniformly in the matrix and refined with increasing rolling reduction. • The rolling deformation promoted and refined the precipitation of an α phase with increasing rolling reduction. • Many nano-sized YAl phases were produced and distributed in the matrix of the composite at a high rolling reduction.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Electron backscatter diffraction study of deformation and recrystallization textures of individual phases in a cross-rolled duplex steel

The evolution of microstructure and texture during cross-rolling and annealing was investigated by electron backscatter diffraction in a ferritic–austenitic duplex stainless steel. For this purpose an alloy with nearly equal volume fraction of the two phases was deformed by multi-pass cross-rolling process up to 90% reduction in thickness. The rolling and transverse directions were mutually interchanged in each pass by rotating the sample by 90° around the normal direction. In order to avoid deformation induced phase transformation and dynamic strain aging, the rolling was carried out at an optimized temperature of 898 K (625 °C) at the warm-deformation range. The microstructure after cross warm-rolling revealed a lamellar structure with alternate arrangement of the bands of two phases. Strong brass and rotated brass components were observed in austenite in the steel after processing by cross warm-rolling. The ferrite in the cross warm-rolling processed steel showed remarkably strong RD-fiber (RD//< 011 >) component (001)< 011 >. The development of texture in the two phases after processing by cross warm-rolling could be explained by the stability of the texture components. During isothermal annealing of the 90% cross warm-rolling processed material the lamellar morphology was retained before collapse of the lamellar structure to the mutual interpenetration of the phase bands. Ferrite showed recovery resulting in annealing texture similar to the deformation texture. In contrast, the austenite showed primary recrystallization without preferential orientation selection leading to the retention of deformation texture. The evolution of deformation and annealing texture in the two phases of the steel was independent of one another. - Highlights: • Effect of cross warm-rolling on texture formation is studied in duplex steel. • Brass texture in austenite and (001)<110 > in ferrite are developed. • Ferrite shows recovery during annealing retaining the (001)<110 > component. • Austenite shows recrystallization during annealing retaining the deformation texture. • The deformation of recrystallization of two phases is independent of one other.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Kinematics and aerodynamics of the velocity vector roll

The velocity vector roll is an angular rotation of an aircraft about its instantaneous velocity vector, constrained to be performed at constant angle-of-attack (AOA), no sideslip, and constant velocity. Consideration of the aerodynamic force equations leads to requirements for body-axis yawing and pitching rotations that satisfy these constraints. Here, the body axis rotations, and the constraints, are used in the moment equations to determine the aerodynamic moments required to perform the velocity vector roll. For representative tactical aircraft, the conditions for maximum pitching moment are a function of orientation, occurring at about 90 deg of bank in a level trajectory. Maximum required pitching moment occurs at peak roll rate, and is achieved at AOA above 45 deg. The conditions for maximum rolling moment depend on the value of the roll mode time constant. For a small time constant (fast response) the maximum rolling moment occurs at maximum roll acceleration and zero AOA, largely independent of aircraft orientation; for a large time constant, maximum required rolling moment occurs at maximum roll rate, at maximum AOA, and at 180 deg of bank in level flight. Maximum yawing moment occurs at maximum roll acceleration, maximum AOA, and is largely independent of airplane orientation.

Durham, Wayne C.↗
DOE OSTI2018

Effects of Rolling Passes on the Transport Properties of 37-Filamentary AgAu-Sheathed Bi-2223 Tapes

Thirty-seven-filamentary AgAu-sheathed Bi-2223 tapes were fabricated by a powder-in-tube (PIT) process. And, the round wires (ϕ 1.86 mm) were rolled to 0.35-mm tapes with 12, 7, 5, and 4 rolling passes through flat rolling, respectively. The influences of different rolling passes on the core density, deformation, and transport properties of Bi-2223/AgAu tapes were systematically investigated. It was noticed that after rolling, the Vickers microhardness of the superconducting core and deform homogeneity along both the horizontal and vertical directions on the cross section of seven-pass rolled tape were better than those on the tapes with other passes, which proved the larger core density and uniform deformation with the seven-pass rolling process. Meanwhile for the wires with 12 and 7 passes, the AgAu/superconducting core interfaces were much flatter. With the rolling passes decreasing from 12 to 4, the critical current density (J{sub c}) first increased and then decreased. Due to the better homogeneity and flatter interfaces, J{sub c} reached the maximum value of 17.3 kA/cm{sup 2} on the seven-pass sample. Meanwhile, the enhancement of current capacities in magnetic field applied parallel to the Bi-2223/AgAu tape surface could also be recognized as the evidence of improving intergrain connections due to the higher density in seven-pass rolled tapes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Rolling Temperature on the Microstructure and Tensile Properties of 47Zr-45Ti-5Al-3V Alloy

The 47Zr-45Ti-5Al-3V (wt.%) alloy was solution-treated at 850 and 780 °C for 30 min and then rolled at different temperatures. The effect of rolling temperature on microstructure and tensile properties was investigated. The results showed that the microstructure contained a large amount of α phase at a rolling temperature of 600 °C. As the rolling temperature increased, the amount of α phase decreased, whereas the amount of β phase increased. When the rolling temperature was higher than 700 °C, the alloy was composed of a single β phase. The tensile properties of the alloy depended strongly on rolling temperature. The yield strength and tensile strength decreased with increasing rolling temperature, whereas the elongation increased. At a given rolling temperature, low solution treatment temperature resulted in higher strength and lower elongation than high solution treatment temperature. The fracture mode changed from cleavage fracture and quasi-cleavage fracture to dimple fracture with increasing rolling temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Hot Rolling on the Microstructure and Mechanical Properties of Nitrogen Alloyed Austenitic Stainless Steel

In the present investigation, the effect of multi-pass hot rolling in the temperature range of 700–1000 °C on the microstructure and mechanical properties of nitrogen alloyed austenitic stainless steel was studied with the aid of optical microscopy, tensile testing and x-ray diffraction measurements. The microstructural changes that occurred in the hot rolled specimens were elongation of grains in rolling direction, nucleation of new grains at the grain boundaries of elongated grains and growth of nucleated grains to form fully recrystallized grains. Elongated grains formed at lower rolling temperature (700–800 °C) due to inadequate strain/temperature for the initiation of dynamic recrystallization. At higher rolling temperature (900–1000 °C), fine grains formed due to dynamic recrystallization. Tensile properties showed strong dependency on the rolling temperature. Tensile strength increased with the decrease in the rolling temperature at the cost of ductility. Maximum strength was observed in samples hot rolled at 700 °C with yield strength of 917 MPa and ductility of 25%. This variation in the tensile properties with the rolling temperature is attributed to changes in the dislocation density and grain structure. The estimated yield strength from the dislocation density, solid solution and grain boundary strengthening closely matched with experimentally determined yield strength confirming the role of dislocation density and grain size in the strengthening.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Numerical Investigation of the Effect of Rolling on the Localized Stress and Strain Induction for Wire + Arc Additive Manufactured Structures

Cold rolling can be used in-process or post-process to improve microstructure, mechanical properties and residual stress in directed-energy-deposition techniques, such as the high deposition rate wire + arc additive manufacturing (WAAM) process. Finite element simulations of the rolling process are employed to investigate the effect of rolling parameters, in particular rolling load and roller profile radius on the residual stress field as well as plastic strain distribution for the profiled roller. The results show the response to rolling of commonly used structural metals in WAAM, i.e., AA2319, S335JR steel and Ti-6Al-4V, taking into account the presence of residual stresses. The rolling load leads to changes in the location and the maximum value of the compressive residual stresses, as well as the depth of the compressive residual stresses. However, the roller profile radius only changes the maximum value of these compressive residual stresses. Changing the rolling load influences the equivalent plastic strain close to the top surface of the wall as well as in deeper areas, whereas the influence of the roller profile radius is negligible. The plastic strain distribution is virtually unaffected by the initial residual stresses prior to rolling. Finally, design curves were generated from the simulations for different materials, suggesting ideal rolling load and roller profile combinations for microstructural improvement requiring certain plastic strains at a specific depth of the additive structure.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Design and Application of CSC-Roll for Heavy Reduction of the Bloom Continuous Casting Process

Center quality control is a key issue affecting large-section bloom production and product quality. The central convex roll could avoid the bloom side part and yield a high reduction amount, which benefit the implement of heavy reduction (HR) for bloom continuous casting process without upgrading the mechanical and hydraulic system of withdrawal and straightening machine. In this work, a curving surface convex roll (CSC-Roll), which could significantly improve bloom center quality, was designed by finite element simulation for a 360 mm × 450 mm #45 steel continuous casting bloom. The optimal roll surface shape of the CSC-Roll was determined based on an analysis of the distribution of the reduction amount in the bloom center and the strain of the bloom centerline and inner surface. The calculation results showed that the optimal size of the CSC-Roll was 200 mm in convex platform region length, 30 mm in convex platform region height, and 80 mm in gradient curvature region length. The bloom heat transfer and deformation behavior in the CSC-Roll reduction process were then analyzed. The results showed that in the CSC-Roll HR process, 61.71 pct of the reduction amount could be transmitted to the inner side of the porosity zone. Macrographs of the 360 mm × 450 mm #45 steel continuous casting bloom proved that the bloom center quality was significantly improved after CSC-Roll HR was applied.

36 MATERIALS SCIENCE↗