Intermediate Annealing Research Articles

Production of transverse magnetic field annealed brass band and how the production process influences the mechanical properties, as well as their correlation and compliance

This paper examines the effect of the thickness h, the deformation reached during the last cold rolling operation ε and the final normalized annealing mode v on the mechanical properties of brass band. The paper looks at the correlation between the ultimate strength σв, elongation and hardness HV in terms of their meeting the specification. The production of L68 brass band involved semi-continuous casting, hot rolling to the thickness of 6 mm and cold rolling to h = ~0.56–0.96 mm with intermediate annealing at H = 1.5–2.7 mm ensuring the deformation ε within 62 to 72%. The intermediate and final continuous annealing lines are equipped with three-phase TFIH (Transverse Flux Induction Heating) units. An intermediate annealing mode has been established that ensures the grain size of 40–80 μm. The strip travel speed was varied as follows during final annealing: ν = 30–46 m/min. The authors determined the stochastic dependences of the properties on ν , h and ε, as well as the annealing modes that are necessary to achieve each property. Actual correlations HV(σв), δ(σв) within the specified ranges were considered versus the properties of the band produced by deformation. It was established that the cold rolling process, together with the heat treatment mode, has an effect on the properties of annealed band and, vice versa, on the heat treatment mode that is necessary to achieve the required properties. With hardness being the same, the induction heat annealed brass band has a higher ultimate strength в than the band produced by normalized final deformation. As a result, the linear relationship σв = f(HV) of the rolled band produced by normalized final annealing is shifted in relation to the optimum position of such relationship within the specified limits adopted in the period when the rolled band was exclusively produced by final deformation. Consequently, the final annealing mode ranges that are necessary for achieving certain properties within the specified ranges, do not match, thus making the task of having the resulting properties hit the above ranges more challenging. Thus, it is proposed to use online control and annealing control to eliminate rejects, and to use the annealing mode-required property relationships obtained from the given data for setting up the initial process mode.

Obtaining Al–Zr-Hf wire using electromagnetic casting, combined rolling-extrusion, and drawing

The article presents the results of obtaining an aluminum electrical wire with a diameter of 0.5 mm from alloys of the Al–Zr-Hf system used in aircraft. Alloys of three compositions were cast in the form of a billet with a diameter of 12 mm using the method of electromagnetic crystallization. Next, the rheological characteristics of billets from experimental alloys were studied. The obtained data were used to simulate the process of combined rolling-extrusion when obtaining a rod with a diameter of 5 mm from a billet with a diameter of 12 mm using the Deform 3D program. A comparison of the experimental forces and forces during the simulation is made for the forces acting on the rolls and the die of the CRE-200 unit. At the next stage, experimental studies were carried out to obtain rods based on simulation data. The obtained rods with a diameter of 5 mm were subjected to drawing or sectional rolling with drawing and intermediate annealing to obtain a wire with a diameter of 0.5 mm. At all stages, the mechanical (ultimate tensile strength, yield strength, elongation to failure and area reduction) and electrophysical properties (electrical resistivity) of the obtained deformed semi-finished products were studied.

Manufacturing of Pure Iron by Cold Rolling and Investigation for Application in Magnetic Flux Shielding.

The presented work investigates a novel method to manufacture 98.8% pure iron strips having high permeability and better saturation flux density for application in magnetic flux shielding. The proposed method uses electro-deposition and cold rolling along with intermediate annealing in a controlled environment to manufacture 0.05–0.5 mm thick pure iron strips. The presented approach is inexpensive, has better control over scaling/oxidation and requires low energy than that of the conventional methods of pure iron manufacturing by pyrometallurgical methods. Important magnetic and mechanical properties of the pure iron are investigated in the context of the application of the material in magnetic shielding. Magnetic properties of the material are investigated by following IEC60404-4 standard and toroidal coil test to determine hysteresis curve, magnetic permeability and core losses. The microstructure is investigated with an optical microscope and scanning electron microscopy to study grain size and defects after cold rolling and annealing. The properties derived from the experimental methods are used in finite element analysis to study the application of the material for static, low-frequency and high-frequency magnetic shielding. Theoretical simulation results for magnetic shielding around a current-carrying conductor and micro-electromechanical inductive sensor system are discussed. Further shielding performance of the material is compared with that of the other candidate materials, including that of Mu-metal and electrical steel. It is demonstrated that the pure iron strips manufactured in the present study can be used for magnetic shielding in the case of low-frequency applications. In the case of high-frequency applications, a conducting layer can be combined to ensure the required shielding effectiveness in the case of Class 2 applications.

Creep rupture ductility of ferritic creep resistant steels

ABSTRACT The creep rupture ductility of not only creep strength enhanced ferritic steels but also conventional 2.25Cr-1Mo steels was investigated, focusing on the remarkable decrease in ductility in the long term. The decrease was well described as a function of yield ratio of applied stress and appeared at about 50% of the 0.2% offset yield stress at the creep test temperature with decrease in the yield ratio. A trade-off relation between creep rupture strength and creep rupture ductility was found for Grade T/P23 steels. The similar trade-off relation between creep strength and ductility was observed also for conventional 2.25Cr-1Mo steels. A remarkable drop in creep rupture ductility of quenched and tempered 2.25Cr-1Mo steels was found in conjunction with a large drop in creep rupture strength. This remarkable drop was considered to be caused by microstructural changes due to the inhomogeneous progress of recovery of tempered martensitic microstructure. A modified heat treatment process with intermediate tempering on partially quenched dual phase microstructure was found to have a beneficial effect on creep rupture ductility for Grade P92 steel. This was considered to be the result of the reduction in residual stress introduced by martensitic phase transformation accompanied with shape change and volume expansion.

Effect of Annealing Temperature on the Interfacial Microstructure and Bonding Strength of Cu/Al Clad Sheets with a Stainless Steel Interlayer.

To explore the influence of annealing temperatures on the interfacial structure and peeling strength of Cu/Al clad sheets with a 304 stainless steel foil interlayer, an intermediate annealing treatment was performed at temperatures of 450 °C, 550 °C, and 600 °C, separately. The experimental results indicate that the interfacial atomic diffusion is significantly enhanced by increasing the intermediate annealing temperature. The average peeling strength of the clad sheets annealed at 550 °C can reach 34.3 N/mm and the crack propagation is along the steel/Cu interface, Cu-Al intermetallic compounds layer, and Al matrix. However, after high-temperature annealing treatment (600 °C), the liquid phase is formed at the bonding interface and the clear Cu/steel/Al interface is replaced by the chaotic composite interfaces. The clad sheet broke completely in the unduly thick intermetallic compounds layer, resulting in a sharp decrease in the interfacial bonding strength.

Effect of antimony addition and asymmetric cold rolling on the texture and magnetic properties of a 1.2% Si steel

This paper investigates the effect of antimony on the microstructure, texture, and magnetic properties of a 1.2 wt% Si steel sheet produced by asymmetric cold rolling. First, the specimens were cast with three different antimony percentages, and after homogenization and hot rolling, they were subjected to an intermediate annealing treatment at 1150 °C for 30 min. The sheet thickness was then reduced to 1 mm using an asymmetric cold rolling process with 80% thickness reduction and finally, the final annealing treatment was performed at 1000 °C for 3 min. The results indicated that increasing antimony improved the texture parameter by increasing the intensity of the θ-fiber. Antimony also accelerated the formation and density of shear bands. Additionally, Cube components nucleated predominantly in shear bands, enhancing the desired texture in the microstructure. Texture evolution affected the magnetic properties of the specimens such that the sample containing 0.026 wt% Sb exhibiting the lowest coercivity and remanence compared to the sample devoid of antimony. It seems that asymmetric rolling has a good interaction with antimony to improve the magnetic properties of low silicon steels.

Terahertz charge and spin transport in metallic ferromagnets: The role of crystalline and magnetic order

We study the charge and spin dependent scattering in a set of CoFeB thin films whose crystalline order is systematically enhanced and controlled by annealing at increasingly higher temperatures. Terahertz conductivity measurements reveal that charge transport closely follows the development of the crystalline phase, with the increasing structural order leading to higher conductivity. The terahertz-induced ultrafast demagnetization, driven by spin-flip scattering mediated by the spin–orbit interaction, is measurable in the pristine amorphous sample and much reduced in the sample with the highest crystalline order. Surprisingly, the largest demagnetization is observed at intermediate annealing temperatures, where the enhancement in spin-flip probability is not associated with an increased charge scattering. We are able to correlate the demagnetization amplitude with the magnitude of the in-plane magnetic anisotropy, which we characterize independently, suggesting a magnetoresistance-like description of the phenomenon.

Microstructural evolution of the bonding zone in TRIP-TWIP laminate produced by accumulative roll bonding

For the first time a four-layered laminate made of X5CrMnNi-16-6-6 (TRIP steel) and X5CrMnNi16-6-9 (TWIP steel) was manufactured by accumulative roll bonding (ARB). An intermediate annealing between rolling passes allowed to achieve good bonding between the laminate layers. The microstructure of the laminate at each step of production was analysed with the main focus on the bonding interface and deformation lenses by means of scanning electron microscopy, including chemical and orientation mapping techniques, and microhardness measurements. Additionally, a special measuring routine was developed to reveal spatial distribution of the grain size along the cross section. Finally, tensile specimens were cut out from the laminate and tested under quasi-static loading with subsequent fracture surface analysis. Repeated rolling and annealing of the steel layers resulted in the alteration of the grain size and microhardness, whereas significant texture appeared only after tensile loading. The grain size in the layer of TWIP steel after first roll bonding and annealing was found to drop down near the surface, whereas no such effect was found in TRIP steel. The microstructure of a deformation lens was found to fully change from severely deformed brittle steel matrix with excessive oxygen content after rolling to a ductile mixture of sub-micron globular oxides and austenite grains after annealing. These ductile deformation lenses ensure excellent bonding of layers and microcrack blunting. This allowed to achieve a remarkable combination of mechanical properties of the four-layered TRIP-TWIP laminate with a yield strength up to 800 MPa and an elongation to failure up to 45%, which resulted in the work of deformation up to 41 GPa·%.

Titanium Drawing

To improve the quality of human life, sometimes, surgical interventions are required to replace or retain damaged tissue during reparative regeneration. Titanium and titanium alloys are well-proven biocompatible materials. The methods of modeling the phase composition of the titanium alloy can be used to predict the chemical and physical-mechanical properties of implants and suture material. In this research, the features of the titanium drawing process are investigated, recommendations are given for thermo-mechanical processing and the choice of a lubricant. Modeling the structure and phase composition of alloys allows predicting their properties and choosing the optimal technological parameters for all drawing transitions. Drawing must be performed in a friction mode close to the hydrodynamic regime with intermediate annealing to control the phase composition of titanium, restore the plasticity resource, and heal crystal structure defects. The composition of atmospheric gases during annealing makes it possible to control the phase composition and properties of the alloy. The use of exfoliated graphite is proposed as a lubricant applied to the anodized titanium surface.

Study of a complex of physical, crystallographic and mechanical properties of aluminum foil for electrolytic capacitors

The results of studies of the complex of physical, crystallographic and mechanical properties of aluminum foil for low-voltage and high-voltage electrolytic capacitors made of high-purity aluminum (99.99% Al) are presented. A comparative analysis of technological schemes for the production of foil for lowvoltage and high-voltage applications is given, the main differences in the schemes are shown, and the results are presented for the physical parameter: the value of specific capacitance, crystallographic characteristics (structure and predominant texture), mechanical properties (tensile strength and relative elongation). Low-voltage foil after electrochemical etching has a fine etching relief, which can cause the danger of its smoothing after the next operation of the electronic processing of molding — the creation of an oxide film of the dielectric. The required surface topography can be achieved at high total degrees of cold deformation, amounting to 98.8%, without intermediate annealing, obtaining a structure that is fibrous along the rolling direction with a predominant deformation texture {011} and pole density according to the results obtained (5.2). On the contrary, high-voltage foil after electrochemical etching has a rougher relief, and here the risk of surface smoothing after the molding operation is minimal, since the dielectric oxide film being formed is actually superimposed and duplicated along the trajectory of the resulting relief. The latter can be achieved by using a foil after recrystallization (intermediate) and final annealing to obtain an average grain size of about 72 microns, a predominantly near-cubic texture of the {420} foil, and a pole density of 2.4 obtained results. At the same time, high values of specific capacitance can be observed in the studied range: at forming voltages of 30 and 450 V, the value of specific capacitance is 1750 and 29 μF/dm2 for low-voltage and high-voltage foils, respectively.

On online texture quality control and management of continuous processes for the production of non-ferrous sheets

The results of the studies of the connection of texture parameters and the quality characteristics of commercial batches of the finally rolled or finally annealed tape made of fcc- materials, which differ in the value of stacking fault energy, phase composition and processing technology are considered. Strips of brass L68 and L63 containing ~62.5 and ~64% of copper and aluminum alloy AMg2 were hot rolled from ingots that were cast in water-cooled and electromagnetic casting mould respectively. Cold rolling was carried out with intermediate annealing to the state of complete recrystallization in the resistance heating furnace (AMg2) or in the induction annealing line (brass) to the finite thickness: ~0.3 mm (AMg2) and 0.6–1.0 mm (brass), varying the degree of the finite plastic deformation. During the final annealing of the brass strip in the line of induction annealing and etching, the speed was varied. The tape was tested for breaking, Vickers hardness number, cutting-out and draw-forming of “glasses” in the combination die. In particular, we controlled the characteristics of the anisotropy of plastic properties, the magnitude of the relative earing and intensity 200 and 220 lines of the texture on the general purpose diffractometers in Fe Karadiation by the Schulz reflection method. The texture parameters T and Т, expressing the ratio of the components of the recrystallization texture and the rolling texture of fcc-materials, were determined. It was found that the accuracy of texture control during annealing of brass L63 rolled products using the same texture parameters is reduced in comparison with materials with high stacking fault energy due to the small fraction of {100} <hkl> recrystallization texture component and the dependence of the structure and phase ratio on small, 1.5% for copper, fluctuations in the chemical composition. At the same time, it remains high enough to control the process of organizing feedback when managing the process online. That is, texture control can be extended to annealing materials with very low stacking fault energy, which contain the second phase. At the same time, there are serious restrictions on the degree of deformation during rolling and on the annealing regimes, in which it is reasonable to use the texture control, as well as the absolute need to determine regression dependences of the properties on the texture when changing the technological processing scheme. In each individual case, the necessary condition for organizing the texture control is the presence of the “close” correlation between the texture parameter and the controlled characteristic. The proposed structural scheme of the texture control during rolling is discussed.The authors gratefully acknowledge S. G. Khayutin, Doctor of Technical Sciences, a founder of a texture control research area in Russia, globally pione ering in texture control of mechanical properties, taking part in acquiring some experimental data used in the research paper, and giving important recommendations at the initial stage of preparing the presented paper.

Ultrathin-gauge high silicon non-oriented electrical steel with high permeability and low core loss fabricated by optimized two-stage cold rolling method

In the present work, the evolution of microstructure and texture and the resultant magnetic properties with different rolling reductions and intermediate annealing temperatures during two-stage cold rolling process were systematically studied. The one-stage cold rolling was also employed for comparison. It was found that finally annealed sheet fabricated by one-stage rolling exhibited pronounced α*-fiber ({h,1,1} < 1/h,1,2>) and γ-fiber (〈111〉//ND) textures. By contrast, the two-stage rolling significantly weakened the unfavorable γ-fiber texture and enhanced the λ-fiber (〈100〉//ND), Goss ({110} 〈001〉) and near-Brass ({110} 〈112〉) textures in final sheets. Meanwhile, the introduction of intermediate annealing reduced the grain boundary density and deformation stored energy in secondly cold-rolled microstructure. The nucleation rate of recrystallization was hence decreased, thereby increasing the final grain size. Increasing intermediate annealing temperature in two-stage rolling process further optimized the recrystallization texture and increased the final grain size. It is noted that the γ-fiber texture in final sheets was gradually decreased with the decrease of second rolling reduction, while the λ-fiber texture and grain size were both increased firstly and then decreased. Eventually, an optimized combination of magnetic properties (B50 = 1.709 T, P15/50 = 1.828 W/kg, P10/400 = 11.92 W/kg) was obtained via a higher intermediate annealing temperature (950 °C) and an appropriate second rolling reduction (75%). Furthermore, the deformation and recrystallization behaviors of specifically oriented grains (i.e., λ-, Goss and near-Brass grains) were discussed in detail.

Влияние равноканального углового прессования на зеренную структуру и внутренние напряжения технически чистого никеля

The structure, phase composition, defects, amplitude of internal stresses and their sources in ultrafine grained technically pure nickel, obtained by equal-channel angular pressing deformation, have been studied by the method of transmission electron microscopy. At equal-channel angular pressing the samples were subjected to shear deformation by compression along two intersecting channels of equal diameter at an angle of 120° at temperature T = 400 °C without intermediate annealing. Number of passes n = 4. The grain structure was studied. It was found that all grains were anisotropic. According to the dislocation structure, the grains were classified into three types: 1) the smallest grains with no substructure (practically no dislocations) - dislocation-free grains, 2) larger grains containing chaotically distributed dislocations or a net substructure, and 3) the largest grains with a cellular or fragmented substructure. The average value of the scalar dislocation density in the grains of each type was calculated. It was found that equal-channel angular pressing resulted in the formation of nanometer-sized particles of secondary phases in ultrafine grained nickel localized inside, on grain boundaries and at grain junctions. The sources of internal stresses are revealed and their amplitude is determined. Determination of the amplitude of internal stresses consisted in determining the amplitude of the curvature-torsion of the crystal lattice by bending extinction contours

Effect of Intermediate Annealing and Reduction Ratio on the Texture Evolution and Formability in Aa5083

Effect of Intermediate Annealing and Reduction Ratio on the Texture Evolution and Formability in Aa5083

Microstructure and mechanical behaviors of Al/Cu laminated composites fabricated by accumulative roll bonding and intermediate annealing

Strength and toughness of laminated composites with alternatively stacked “brick-and-mortar” structure can be synchronously improved along the direction parallel to the layer interface. However, it is still a challenge to prepare high-performance laminated composites in large quantities to meet industrial needs. In this work, we employ accumulative roll bonding (ARB) and/or intermediate annealing to prepare Al/Cu laminated composites as cheaper substitutes for Cu alloys due to lightweight and considered electrical conductivity. Our results show that the ARB process decreases the layer thicknesses and grain sizes, and improves the Vickers micro-hardness of Al/Cu laminated composites. As the ARB cycle increases from 1 to 8, the tensile strength firstly increases from 279.20 MPa to 358.71 MPa, and then decreases to 317.88 MPa. Meanwhile, the uniform elongation firstly increases from 1.25% to 1.71%, and then decreases to 0.58%. These variations of tensile properties are tightly linked to the layer-integrity and microstructures of Al and Cu layers. Moreover, the intermediate annealing (350 °C for 30 min) applied after every 2 ARB cycles can significantly increase the tensile strength, uniform elongation and elongation to failure, especially for Al/Cu laminated composites with high ARB cycles, because intermediate annealing remarkably improves the interfacial metallurgical bonding and continuity/integrity of Al and Cu layers. However, the final annealing for long time would introduce brittle intermetallics (like AlCu and Al2Cu), and therefore deteriorate the tensile ductility. This work provides a new treatment process for fabricating Al/Cu laminated composites with synchronously increasing strength and ductility.

A route to produce toughened acicular ferrite with equivalent hardness as martensite: The combined effect of elements segregation and pre-transformed allotriomorphic ferrite

Acicular ferrite (AF) is a universal occurrence during the welding of steel. In this study, when heat treatment of intermediate annealing after austenitization was adopted, AF was obtained in the quenching process (−100 °C/s). The transformed AF has significantly higher toughness with no loss in hardness compared to martensite, which was also obtained at a cooling rate of −100 °C/s. The experimental and calculated results showed that film-like allotriomorphic ferrite are generated and high levels of boron (B) and molybdenum (Mo) segregation occur before transformation. These two effects inhibit the nucleation of bainitic ferrite (BF) and promote AF nucleation of inclusions. The segregation of B mainly occurred during the cooling process from austenitizing temperature to intermediate annealing temperature via the nonequilibrium mechanism, and the Mo segregation could be enhanced during intermediate annealing treatment by the generation of allotriomorphic ferrite.

Fabrication of Low AC Loss Cu0.5Mn-Based NbTi Superconducting Strands

The Cu-0.5 wt.% Mn alloy is selected as the inter-filament matrix in NbTi superconducting strand with low AC Loss. Three types of NbTi strand with the filament number of 10800,12960 and 33696 were prepared based on high homogeneity Nb47Ti alloy,pure Nb sheet,high purity oxygen free copper and Cu-0.5 wt.% Mn alloy. Heat treatment with 3-5 intermediate annealings has been applied to increase the Jc of the strands. When the number of annealings increases from 3 to 5,Jc raises from 2295 to 2958 A/mm2 for the 10800 filament strand,and from ~2500 to ~2800 A/mm2 for the 12960 filament and 33696 filament strands. As the filament number increases from 10800 to 33696,the n values keep the same level,demonstrating that no "sausage like" or "nodular like" filaments exist in the final strands. When the filament diameter of the strand reduces from 4.6 m to 2.6 m,the hysteresis loss decrease from 42.8 mJ/cm3 to 17.3 mJ/cm3 at 3 T&4.2 K. Based on this research,WST has obtained the stable mass production technology of the strands. Using heat treatment with 4 annealings,the different batches of the strands with Jc ranged from 2600 to 2800 A/mm2 have been produced with piece length level of 1-3 kilometer.

Effects of annealing on microstructure evolution and mechanical properties of constrained groove pressed pure titanium

Constrained groove pressing (CGP) is performed on pure Ti followed by intermediate annealing at 450–650°C to fabricate large-scale plate-shaped sheets with improved mechanical properties. The results reveal that intermediate annealing not only improves ductility, enabling the successful achievement of the three-pass CGP at room temperature, but also enhances the tensile strength during the subsequent passes. The process involving three CGP passes with intermediate annealing after the first pass (referred to as PAPP) is superior for strength improvement. Compared to that of pure Ti, the tensile strength of the PAPP specimen annealed at 550°C is improved by 67%. This is ascribed to the recovery of the secondary twins, 85° <11–20> during annealing at 550°C, resulting in the activated 29.5° <1–100> twin variant in the two subsequent CGP passes. Meanwhile, the dislocations within the shear bands recover and form dislocation networks or subgrains at 550°C, and thus the dislocations continue to entangle and pile up at these sub-grain boundaries in the subsequent pressing, which further contributes to the improvement in the tensile strength. However, recrystallisation occurs in the CGP-deformed pure Ti annealed at 650°C, leading to a decrease in the tensile strength.

Enhancing the performance and stability of carbon-based CsPbI2Br perovskite solar cells via tetrabutylammonium iodide surface passivation

All-inorganic carbon-based perovskite solar cells (C-PSCs) with CsPbI2Br as photosensitizer have attracted great attention due to their low cost, high efficiency, and good stability. However, the CsPbI2Br film prepared by the solution method usually has many defects, which reduces the charge extraction rate and photoelectric performance. In this paper, intermediate gradient annealing and antisolvent ethyl acetate treatment are combined to prepare CsPbI2Br films with good crystallinity and few voids. The surface of the obtained CsPbI2Br film is then treated using tetrabutylammonium iodide (TBAI), which can interact with the Pb-I framework to passivate defect states and extend the carrier lifetime. Finally, the champion power conversion efficiency (PCE) of the optimized C-PSCs with a structure of FTO/SnO2/CsPbI2Br/carbon electrode prepared in the air reach 12.29%. At the same time, TBAI molecules also effectively enhance the stability of the PSCs, and the unencapsulated device can still maintain 90% of the initial efficiency after 300 h of storage in an ambient air atmosphere with a relative humidity of 20%-30%. This work provides a simple and effective strategy for the preparation of cheap, high-performance, and stable all-inorganic C-PSCs under atmospheric conditions, and also increases the feasibility of PSCs commercialization.

Investigation of Primary Recrystallization and Decarbonization with Different Heating Rates of Intermediate Annealing Using Nb-Containing Grain-Oriented Silicon Steel

An Nb-containing grain-oriented silicon steel was produced through double-stage cold rolling in order to investigate the effect of the heating rate during intermediate annealing on primary recrystallization and decarburization behavior. The microstructure and texture were observed and analyzed by an optical microscope and an electron backscatter diffraction system. A transmission electron microscope was used to observe the precipitation behavior of inhibitors. The decarburization effect during intermediate annealing was also calculated and discussed. The results show that primary recrystallization takes place after intermediate annealing. As the heating rate increases, the average grain size decreases gradually. The textures of {411}&lt;148&gt; and {111}&lt;112&gt; were found to be the strongest along the thickness direction in all of the annealed specimens and are mainly surrounded by HEGB and HAGB (&gt; 45°). A large number of inhibitors with the size of 14~20 nm precipitate are distributed evenly in the matrix. The above results indicate that the higher heating rate during intermediate annealing contributes to both an excellent microstructure and magnetic properties. From the calculation, as the heating rate increases, decarbonization tends to proceed in the insulation stage, and the total amount of carbonization declines.