Prior Cold Rolling Research Articles

Effect of prior cold rolling on the dry wear performance of GCr15 bearing steel with multiphase microsturcture

In this work, the effect of cold rolling on the wear performance of GCr15 bearing steel with multiphase microstructure has been investigated. The microstructural observation shows that prior cold rolling facilitates to the dissolution of carbides during austenitization. With the increase of cold rolling reduction, the residual austenite content is increased after multiphase heat treatment. The wear results indicate that friction coefficient as well as wear rate distinctly decreases with the increase of rolling reduction. It is also found that the transformation of martensite from residual austenite induced by wear stress increases the surface compressive stress and hardness for the rolled specimens, thereby leading to the enhancement of dry wear resistance.

Effect of prior cold rolling and aging temperature on PH martensitic stainless steel: Evolution of microstructure, micro-texture and austenite stability

A systematic investigation of the evolution of martensitic microstructure, micro-texture, and austenite stability followed by correlation with hardness was carried out as a function of prior cold rolling (PCR) (20–80 % thickness reduction) and aging temperature (510–593 °C) for a very low C (0.007 wt.%) Fe-Cr-Ni-Ti-Mo precipitation hardened (PH) martensitic stainless steel. The cold-rolled and aged samples were compared with directly aged samples to emphasize the synergistic effect of PCR and aging temperature. Martensite has been found to have recrystallized to varied extents by this combined effect (severe deformation and higher aging temperature), resulting in variations in size, morphology, and texture of the martensitic/ ferritic microstructure. These in turn affect the formation and the stability of austenite. Austenite stability has been found to be a function of phase composition, strain, and size, which depend on PCR% and the aging temperature. Higher Ni content (which decreases with aging temperature) and fineness (driven by the extent of martensitic recrystallization) of austenite have been found to increase the stability of reverted austenite. Size distribution of the main strengthening precipitate Ni3Ti has been found to be a function of PCR% and aging temperature through the involved mechanisms of faster diffusion, more nucleation sites, and coarsening. Hardness has been significantly influenced by the morphology, size of martensite, and amount of austenite, and size distribution of Ni3Ti precipitates. In the present work, the individual effects of these factors were discerned, explaining the overall variation in hardness as a function of PCR% and aging temperature.

Tailored carburization gradient microstructure and enhanced wear properties of M50NiL steel via introduced prior cold rolling

M50NiL (Chinese grade G13Cr4Mo4Ni4V) steel is widely used in aircraft bearing raceways that require excellent wear resistance under harsh service conditions. However, the impact of cold rolling, as an advanced forming process for bearings, on the carburization process and wear properties is still unknown. Therefore, the gradient microstructure and dry sliding wear performance of the cold-rolled M50NiL disc against Si3N4 ceramic ball have been investigated. The results show that with the increase of cold rolling reduction to 40 %, the carbon concentration of surface is increased by 17.1 % due to the growing percentage of grain boundaries (GB) and dislocation density. The carbide content is increased by 29 % with average size declined by 21.2 %, which contributes to a 7.4 % increase in the surface hardness. Additionally, the wear test indicates that the average friction coefficient and wear rate are respectively reduced by 17.3 % and 47.1 % when the rolling reduction increases to 40 %. After prior rolling, the wear mechanism changes from severe abrasion to adhesion and tribochemical reactions accompanied with the enhancement of wear properties, which is mainly attributed to the uniform distribution of finer carbides with higher fraction on the surface and subsurface.

Precipitation/recovery kinetics and mechanical properties in rapidly solidified AA6005 AlMgSi sheets via thin strip casting: Effects of casting cooling rate and thermomechanical processing route

Rapidly solidified AA6005 Al-Mg-Si sheets produced via a novel Thin Strip (TS) casting route were characterized and compared with conventional Direct Chill (DC) counterparts for the evolution of microstructure (i.e., precipitation/recovery kinetics) and mechanical properties at various thermo-mechanical tempers. To get to 1 mm final gauge, the DC ingot was homogenized, hot and cold rolled, whereas the TS casting was only cold rolled. After solutionizing (the T4 temper), the final-gauge DC and TS sheets exhibited a similar aging response upon the T6 temper. However, upon artificial aging without solutionizing, termed TSH temper, the as-rolled TS sheets showed a better age hardening kinetics, as manifested in a larger volume fraction of precipitates (primarily β' in this case) and a higher yield strength than the DC sheets (285.1 ± 5.1 MPa vs. 195.2 ± 2.2 MPa, respectively). This was attributed to the higher cooling rates the as-rolled TS sheets experienced during casting; thereby a higher Mg/Si supersaturation in the matrix due to rapid solidification. The TS sheet with the TSH temper exhibited a comparable yield strength to that of the T6 temper, though at a reduced ductility (5.5 ± 0.6% vs. 11.8 ± 0.3% elongation, respectively). Despite with a reduced volume fraction of the hardening precipitates (as compared with the T6 temper), the yield strength of the TS sheet at the TSH temper was compensated for by a considerable amount of remaining cold work from the prior cold rolling stage. Finally, a yield strengths model for the TS-TSH material was developed.

Effect of prior processing on the decomposition of the β phase in Ti–Nb alloys during intermediate heat treatments

Metastable β-Ti alloys exhibit multiple decomposition pathways during isothermal ageing. Ages at intermediate temperatures below the α/β transus result in the formation of α or isothermal ω. The effect of prior processing on these pathways remains largely unexplored within the literature. Therefore, the role of processing on a Ti–Nb alloy was investigated in cold rolled and solutioned conditions. The solutioned sample showed evidence of recrystallisation, with shear bands remnant from the prior cold rolling that exhibited a greater degree of texture than the surrounding material. During isothermal ageing ωiso was observed outside of these bands whilst α phase precipitated within the bands and throughout the cold rolled sample. This shows that the remnant strain from the rolling process facilitated α nucleation over ωiso due to accommodation of the α/β interface. Additionally, it was seen that the magnitude of internal strains had a marked effect on the α morphology observed.

Increasing the yield strength while preserving strain hardenability and ductility in a beta titanium alloy exhibiting transformation induced plasticity (TRIP)

The commercial β-Ti alloy, Ti-10V-2Fe-3Al; primarily used with an α+β microstructure, exhibits a high yield strength but with poor strain-hardenability and limited ductility. This paper focuses on the interplay between stress-induced martensite (α”) in this alloy, introduced via prior cold-rolling (5,10, 20, and 30%) and additional martensite (α”) forming during subsequent tensile loading, leading to a simple way to substantially increase the yield strength while enhancing the high strain hardenability (via TRIP) and maintaining the uniform tensile ductility. The results indicate that the YS in this alloy can be substantially tuned from 400 to 1800 MPa, via cold-rolling. Among the various conditions that were analyzed, the 5% cold-rolled condition offered the best combination of YS (∼900 MPa), ductility (8%) and the strain hardenability. The stress-induced α” formation during tensile loading is essential for maintaining the high strain-hardening and, consequently the uniform tensile ductility in this alloy.

Investigation on the ballistic induced nanotwinning in the Mn-free Fe27Co24Ni23Cr26 high entropy alloy plate

Mn-free Fe27Co24Ni23Cr26 high-entropy alloy (cold-rolled 40% and then annealed at 800 °C) was subjected to ballistic deformation (strain rate > 106 s−1) at room temperature. The microstructural examinations of the bulletproof plate were focused on three regions (labeled I, II and III) starting from the no-deformation region to the heavy deformation region adjacent to the bullet hole. In region I, lamellar annealing nanotwins were found in the nearly recrystallized grains, and the boundaries of annealing nanotwins had accumulated dislocations, presumably created by prior cold-rolling. The intermediate deformation region was full of complex nanotwin structures and a high density of dislocations. The intersection block structures created by the boundaries of annealing and deformation nanotwins significantly confined the dislocation movement. Alternatively, in the heavy deformation region, besides the typical intersection structures of deformation nanotwins, the boundaries of annealing and deformation nanotwins were found to be significantly deviated from the ideal twin orientation, presumably due to successive deformation during the course of ballistic deformation. Moreover, high-resolution transmission electron microscopy (HRTEM) clearly revealed that bundles of stacking faults were created at the intersections of two bundles of deformation nanotwins.

The effects of cold rolling and aging conditions on the microstructure and magnetic properties of a semi-hard Fe–Mo–Ni magnetic alloy

Experiments were conducted to examine the effect of prior cold rolling and ageing conditions on the microstructure and magnetic properties of a ternary Fe–Mo–Ni magnetic alloy. For this purpose, a semi-hard Fe–18Mo–5Ni (wt. %) magnetic alloy was cold rolled at various reductions in area of 65, 80, and 95% for inducing the magnetic anisotropy. The cold rolled specimens were then aged at the various temperatures of 570, 610, and 640 °C for the different times of 1, 2, 3, and 6 h. The cold-rolled and aged specimens showed the crystallography texture as characterized by X-ray diffractometry method. The crystallography texture was described as the parallel orientation of the {002} family planes with the surface of rolling. The preferred orientation of {002} planes was intensified by cold-rolling, while it weakened by subsequent aging treatment. The coercive force was controlled in the range of 23–110 Oe by adjusting the ageing temperature and time due to the formation of the ferromagnetic (Fe,Ni)7Mo6 precipitates as revealed by optical and electron microscopy techniques. Furthermore, the magnetic measurements by vibrating sample magnetometer showed that the remanence and squareness increased from 0.94 to 1.2 T and from 0.58 to 0.77, respectively.

Engineering mechanical properties by controlling the microstructure of an Fe–Ni–Mn martensitic steel through pre-cold rolling and subsequent heat treatment

Experiments were conducted to examine the effects of prior cold rolling and subsequent heat treatment on the microstructure, phase evolution and mechanical properties of an Fe–10Ni–7Mn martensitic steel. The results show that 70% cold rolling leads to deformation-induced austenite formation in the microstructure and reduces the size of the martensite blocks. Prior cold rolling increases the reversed austenite volume fraction under post-deformation intercritical annealing (PDIA) at 600 °C compared with the solution annealed condition. Electron back scattering diffraction and dilatometric studies showed that under PDIA there is a reverse transformation of martensite to austenite through a sequential combination of martensitic and diffusional mechanisms. There is also a precipitation of θ-NiMn particles in the PDIA specimen after subsequent ageing leading to an increase in the ultimate tensile strength in tensile testing. Cyclic tensile testing revealed pseudoelastic behavior in the cold-rolled specimen but this disappeared after PDIA and appeared again after subsequent ageing. • Cold rolling produces deformation-induced austenite formation and also refines the martensite blocks. • The prior austenite and the smaller martensite blocks are the primary potential sites for austenite nucleation during PDIA. • Ultimate tensile strength improves from ~695 MPa for the solution annealed sample to ~1215 MPa for the PDIA processed specimen followed by ageing. • Observed pseudoelasticity in the cold rolled specimen disappears after PDIA. • Pseudoelasticity appears again in the PDIA processed specimen followed by ageing.

Effect of cold rolling on aging precipitation behavior and mechanical properties of Cu–15Ni–8Sn alloy

The present study investigated the aging precipitation behavior and mechanical, electrical properties of Cu–15Ni–8Sn alloy affected by cold rolling with different deformations. During cold rolling, the grain is elongated gradually along rolling direction with increasing deformation, simultaneously accompanied by the occurrence of a great deal of dislocations and deformation twins. During aging process, the coherent DO22 and L12 ordered phases precipitate successively from the matrix after 90% rolling deformation and aging treatment at 400 °C for 0.5 h with the orientation relationship of (1¯10)DO22 // (022¯)Cu, [111]DO22 // [211]Cu; (11¯1¯)L12// (11¯1¯)Cu, [211]L12 // [211]Cu. However, discontinuous precipitation (DP) behavior is significantly accelerated by prior cold rolling. On the one hand, by revealing the underlying growth kinetics of DP, it can be found that the nucleation sites of DP transform from grain edges to grain boundaries gradually with increasing rolling deformation. On the other hand, the nucleation sites and nucleation rate of DP can be enhanced greatly with increasing dislocation density. Furthermore, the interlamellar spacing of DP slightly increases and the morphology transforms from lamellar structure to bush-like structure gradually with increasing rolling deformation. In addition, the hardness, tensile strength and electrical conductivity are obviously improved while the peak aging time greatly shortens with increasing rolling deformation. The optimal combination of properties with a hardness of 409 HV, a yield strength of 1256 MPa, and an electrical conductivity of 7.5 %IACS can be obtained in the sample with 90% rolling deformation after aging treatment at 400 °C for 0.5 h. The corresponding strengthening mechanism and conductive mechanism were discussed. It can be discovered that the precipitation strengthening, dislocation strengthening and solid solution strengthening are believed to be the main strengthening mechanisms to enhance the alloy strength.

Effect of prior cold ring rolling on carbide dissolution during the austenitizing process of an M50 bearing steel

The influence of prior cold ring rolling (PCRR) on carbide dissolution during the austenitizing process of an M50 bearing steel was investigated by combining microstructural observations with kinetics analysis. The microstructural results show that the PCRR leads to a reduction in the volume fraction and the mean diameter of the undissolved carbides. The matrix of the as-quenched specimens after PCRR is enriched with more carbon and alloying elements than those without PCRR, which further confirms that the dissolution behavior of the alloy carbides is enhanced by PCRR during the austenitizing process. The kinetics of the transformation from ferrite to austenite (α → γ) without and with PCRR are determined by differential scanning calorimetry (DSC) upon heating. The austenite onset (Ac1) and end (Ac3) temperatures both decrease with as the thickness reduction from the PCRR increases. The activation energy for the α → γ transformation is calculated and shows a significant decline when the PCRR process is applied. In addition, the PCRR process results in a slight increase in the hardness regardless of the austenitizing temperature.

Anomalous size-dependent strength in micropillar compression deformation of commercial-purity aluminum single-crystals

An anomalously reduced size-dependent strength of commercial-purity aluminum (Al) single-crystal micropillars with diameters ranging approximately from 1 to 10 μm is reported. High-purity Al (99.99%) single-crystal micropillars exhibited an obvious size dependence of the resolved shear stress for slip. The measured shear stress resolved onto a primary slip system (τi) scaled by the shear modulus (G) and the pillar diameter (d) scaled by the Burgers vector (b) showed the following correlation: τi/G = 0.33(d/b)−0.63, which agreed well with previous works. However, the commercial-purity Al samples exhibited a lower power-law exponent (0.19) for their size-dependent strength, resulting in (τi/G) = 0.006(d/b)−0.19. TEM characterization revealed the local presence of Al–Fe intermetallic precipitates surrounded by relatively high-density dislocations in annealed commercial-purity Al samples. These results indicate the relatively high-density dislocations could be responsible for the reduced size-dependent strength, which was confirmed by the remarkably reduced size dependence of their resolved shear stress by prior cold rolling. The reduced size-dependent strength can be rationalized using the stochastic model of the dislocation source length. Thus, this study provides a new insight to allow the application of the micropillar compression test to commercially produced Al alloys.

Recrystallized cube grains in an Al–Mg–Si alloy dependent on prior cold rolling

ABSTRACTThis paper reports on the experimental investigation of an industrial Al–Mg–Si alloy, which was subjected to different cold rolling reductions and subsequently solution annealed. Based on large-scale electron backscatter detection (EBSD) measurements, it provides an analysis of the area fraction, size and number density of cube grains in the fully recrystallized microstructure. The area fraction and number density of recrystallized cube grains increase continuously with increasing strain, but the cube grain size equals the average grain size independent of prior strain. The recrystallization advantage of cube grains decreases rapidly with increasing misorientation from the ideal cube component. The technological relevance of this misorientation dependence and its possible micro-mechanical origins are discussed.

Effect of microstructure and microtexture evolution on creep behavior of hot-rolled and mushy-state rolled Al-4.5Cu-5TiB2 in-situ composite

Tensile creep behavior of the Al-4.5 wt.%Cu-5wt.%TiB2 in-situ composite, subjected to hot rolling, and mushy state rolling with or without prior cold rolling has been examined at two different temperatures (275°C and 300°C) under 25 MPa stress in order to study the effects of the microstructural and microtextural evolutions introduced by the thermo-mechanical treatments. The creep behavior of the investigated samples has been analyzed in terms of minimum or steady-state creep rate, time to rupture, and strain fractions in primary, secondary or tertiary stages of creep along with a thorough assessment of microstructural evolution and related damage examined using scanning electron microscopy, transmission electron microscopy, and electron back-scattered diffraction technique. The creep resistance of the pre-cold rolled mushy state rolled composite (PCMRC) at both the test temperatures has been found to be superior to that of the hot rolled composite or mushy state rolled composite. When tested at 275°C, the PCMRC composite has exhibited the lowest steady-state creep rate (∼1.36 × 10−10 s−1) and the highest time to rupture (∼903 h). The homogeneity of elemental Cu in the solid solution, a uniform distribution of CuAl2 and TiB2 particles in the matrix, and the highest low angle boundary density achieved due to mushy state rolling with prior cold rolling have imparted higher creep resistance through restricting dislocation glide. The formation of fine CuAl2 precipitates at the pre-existing dislocations and sub-grain boundaries within grains in course of the creep test has further improved the creep resistance through Orowan strengthening. The fracture surfaces have revealed the presence of dimples containing fine CuAl2 precipitates confirming partial ductile failure, along with intergranular cracking due to de-cohesion of CuAl2 and TiB2 particles at the α-Al grain boundaries.

The effect of prior cold rolling on the carbide dissolution, precipitation and dry wear behaviors of M50 bearing steel

Abstract In this work, the carbide dissolution and precipitation of M50 bearing steel were investigated as a function of cold rolling reduction. It is observed that the prior cold rolling not only enhances the dissolution of primary carbides, but also contributes to the carbide precipitation. Additionally, the influence of prior cold rolling on the dry wear behaviors of M50 bearing steel was studied, finding that the friction coefficient as well as wear rate decreases with the increasing cold rolling reduction. This result could be attributed to the formation of stable self-lubricating film within the subsurface layer for the specimens with cold rolling.

Effect of pre-cold rolling on the evolution of microstructure, microtexture, and mechanical properties of the mushy state rolled in-situ Al-4.5Cu-5TiB2 composite

The mushy state rolling has been found as a promising technique for near-net forming of the cast Al-4.5 wt% Cu-5 wt% TiB2 in-situ composite to obtain microstructural refinement and moderate mechanical properties. Cold rolling with 30% reduction in thickness was carried out before mushy state rolling, for achieving a relatively more homogeneous distribution of CuAl2-TiB2 particles as well as an appropriate microstructure to enhance the mechanical properties. A comparative investigation on the microstructural and microtextural evolution, along with mechanical properties of both the mushy state rolled composite (MRC) and pre-cold rolled mushy-state rolled composite (PCMRC) was performed, and the microstructure-property correlation was established. The PCMRC exhibited the lowest homogenized lengthscale parameter (LH 29 μm) indicating the maximum uniformity of particle distribution, computed with the help of multi-scalar analysis of area fractions (MSAAF) technique. Electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) studies revealed the presence of fine sub-grains within centrally located deformed Al grains due to dynamic recovery, as well as the particle stimulated nucleation of equiaxed fine Al grains by dynamic recrystallization or rapid solidification of liquid near edges for both the investigated composites. The PCMRC displayed a superior combination of hardness (96.82 ± 4.5 HV5kgf), 40% higher ultimate tensile strength (301.4 ± 1.8 MPa), and 68% more uniform elongation (30.8% ± 0.5%), compared to the MRC. The improvement in mechanical properties is attributed to the uniform particle distribution and presence of both higher density of low angle boundaries and recrystallized grains adjacent to the particles, obtained from prior cold rolling.

Heat Treatment Optimization in Al-Cu-Mg-Si Alloys, with or without Prior Deformation

The properties of Al-Cu-Mg alloys simultaneously depend on dissolving the maximum amount of Cu and Mg in the solution treatment and on achieving optimal ageing. The aim of this study is to analyze the effect on an Al-Cu4.5-Mg1.5-Si0.75 alloy, manufactured by continuous casting and hot rolling until achieving a reduction in its cross-section greater than 90%, of the dwell time at the solution temperature, 495 °C (4, 8, and 24 h), of the different ageing temperatures (160, 180, and 200 °C), and of cold rolling prior to ageing. The microstructural variations underwent the material during its manufacturing process, form its continuous casting to subsequent hot rolling, were analyzed by means of optical microscopy (OM) and scanning electronic microscopy (SEM), with characteristic energy dispersive X-ray (EDX) microanalysis. The crystalline phases present after the different solution and natural ageing treatments were identified and quantified by means of X-ray diffraction (XRD), concluding that Mg is easier to dissolve than Cu. The transient states associated with the Mg2Si phase are the most abundant. However, the longer the dwell time at the solution temperature, the greater the weight percentage of the transient states associated with the Al2Cu phase during ageing. The higher the ageing temperature, the faster the peak hardness is reached, but the lower its value. The ageing temperature that allows the highest hardness to be obtained was 160 °C. The maximum hardness value reached was 162 HV, obtained after a solution treatment at 495 °C for 4 h and ageing at 160 °C for 50 h. By means of prior cold rolling, the peak hardness values are reached more quickly and their values slightly exceed those obtained without this deformation. With ageing at 180 °C, 168 HV are reached after 6 h at this temperature.

Effect of Heat Treatment and Combination of Cold Rolling and Heat Treatment on Microstructure and Mechanical Properties of Titanium Alloy Ti6Al2V2Zr1.5Mo

The heat treatment and cold rolling combinations have been carried out on titanium alloy Ti6Al2V2Zr1.5Mo, and microstructure evolution and mechanical behavior have been studied. Solution treatment below the β-transus temperature, followed by air cooling, resulted in higher microhardness/strength as compared to the same with water quenching. A sudden drop in microhardness/strength is observed in sample solution heat-treated above β-transus temperature followed by air cooling. The former is attributed to the additional presence of fine secondary α-phase formed by dynamic aging during air cooling as compared to water-quenched samples which did not have fine secondary α-phase. Solution treatment above β-transus temperature resulted in Widmanstatten microstructure with no significant fine secondary α in air-cooled samples. Among the studied conditions of cold rolling (CR), gain in strength of the alloy from annealed condition is significant with first 15% reduction and thereafter it is marginal for 30% reduction. Initiation of cracks at the edges has been observed in 30% CR. The microstructure of cold-rolled samples confirms the fragmentation of α-plates with the presence of high dislocation density. Heat treatment of cold-rolled samples resulted in significant reduction in strength from the as-cold-rolled conditions. The marginally lower strength than the as-received (annealed) or heat-treated alloy samples is due to the recrystallization in CR samples and the formation of Widmanstatten microstructure in air-cooled samples. The alloy does not have fine secondary α or regions with large dislocation density in this condition. The microstructure in the samples heat-treated (with air cooling) below as well as above β-transus temperature (after CR) is similar to air-cooled samples (without prior CR) with heat treatment above β-transus temperature. This indicates the reduction in recrystallization temperature with cold working, which is substantiated with the reduction in strength as well.

Reversed Microstructures and Tensile Properties after Various Cold Rolling Reductions in AISI 301LN Steel

Heavy cold rolling is generally required for efficient grain size refinement in the martensitic reversion process, which is, however, not desirable in practical processing. In the present work, the influence of cold rolling reductions of 32%, 45% and 63% on the microstructure evolution and mechanical properties of a metastable austenitic AISI 301LN type steel were investigated in detail adopting scanning electron microscopy with the electron backscatter diffraction method and mechanical testing. A completely austenitic microstructure and a partially reversed counterpart were created. It was found that the fraction of grains with a size of 3 µm or larger, called medium-sized grains, increased with decreasing the prior cold rolling reduction. These grains are formed mainly from the shear-reversed austenite, transformed from slightly-deformed martensite, by gradual evolution of subgrains to grains. However, in spite of significant amounts of medium-sized grains, the tensile properties after the 32% or 45% cold rolling reductions were practically equal to those after the 63% reduction. The austenite stability against the formation of deformation-induced martensite in subsequent straining was reduced by lowering the cold rolling reduction, due to the larger grain size of medium-sized grains and the shift of their orientation towards {211} <uvw>.

The spheroidizing tendency and spheroidization mechanism of 75Cr1 steel

Spheroidization annealing process was carried out on 75Cr1 steel after cold rolling. Using TEM, SEM and image analysis software Image-Pro Plus 6.0, the effects of cold rolling and spheroidization processes on microstructure and mechanical properties were analyzed. The result shows that the cold rolling leads to fragmentation of the cementite and formation of the defects, which induces faster lamellae break-up and accelerates the annealing process. With the increase of isothermal temperature and holding time, the dimension of the spheroidized carbides increase as driven by Ostwald ripening mechanism, whereas the hardness of the steel decreases. The prior cold rolling before annealing process causes the yield strength improve slightly, however shows little effect on the cold formability. The optimum heat treatment process is, holding the samples at 705oC for 6 hours with cold deformation ratio (ε) of 0.6.