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In this paper, the influence of bismuth content and heating rate on the morphology of MnS inclusions in bismuth-containing free-cutting steel during heating was investigated through in situ observation experiments and 3D electrolytic corrosion experiments. By observing the microscopic morphology of inclusions in the original sample, it was found that MnS inclusions in the sample were rod-shaped, spherical, irregular, small in size, and mostly clustered at the grain boundary in the form of chains and divergences. With the addition of bismuth, MnS inclusions of a larger size appear in the steel, and the inclusions distributed at grain boundaries are also reduced. When bismuth (0.010~0.020%) is added to the steel, MnS is mainly spherical and uniformly dispersed in the steel matrix. If the bismuth content is too high, the inclusions aggregate. Through in situ observations of the inclusions in the sample, it was found that the addition of bismuth in the heating process delays the appearance of ferrite grain boundaries and contributes to the spheroidization of MnS inclusions. Mn and S elements can fully diffuse slowly in the matrix with a heating rate below 1 °C/s and a long holding time (300 s), which provides the possibility for the spheroidization of MnS inclusions. [ABSTRACT FROM AUTHOR]

Three-mm-diameter WC/HSS composites with different binders (Co and Co-Ni-Fe) were prepared. The effect of two different binders on the microstructure and properties of WC powder and HSS composites was compared to investigate the feasibility of substituting Fe and Ni for Co in WC and steel composites. The results show that the WC/HSS sample without binder has significant macropores at the interface, with a porosity of up to 43.76%. The porosity of the composite material containing Co binder is 6.07%. The partial substitution of Ni and Fe for Co significantly reduces the shrinkage temperature of WC powder, and the porosity was reduced to 0.77%. The addition of Ni and Fe in WC facilitates the mutual diffusion among Cr, Mo, and Co elements and the interface bonding between WC and HSS. After adding Ni and Fe elements, the microhardness of the WC/HSS composite materials is slightly lower than that of the Co-added composites, with a microhardness of 1204 HV in the WC region. The HSS microhardness remains almost constant during the binder substitution, maintaining around 600 HV. The wear resistance of the composite outer layer can be effectively enhanced by the use of Co, Ni, and Fe additives. [ABSTRACT FROM AUTHOR]

The development of free-cutting steel is inseparable from the development of environmentally friendly alloy elements and the control of inclusions shape. Alloying elements can affect the composition, morphology, size, and distribution of inclusion, which are the main factors affecting the machinability of free-cutting steel. This study selected sulfur free-cutting steel with different chemical compositions as the research object to examine the effects of bismuth and bismuth tellurium on sulfur-containing free-cutting steel through electrolytic corrosion experiments, metallographic microscopy, scanning electron microscopy, energy spectrum, and electron backscattering analyzer. The results showed that the microstructures of free-cutting-steel containing sulfur, free-cutting steel containing sulfur bismuth, and free-cutting steel containing sulfur bismuth tellurium are composed of ferrite, pearlite, and inclusions. The inclusions in sulfur-containing free-cutting steel are chain, cluster, and a few dotted MnS. The inclusions in sulfur-bismuth free-cutting steel are point and a few dotted MnS. After the addition of Te, the number of dotted inclusions is reduced, while the number of chain and cluster inclusions is increased. Most of the inclusions in bismuth-containing free-cutting steel are flake inclusions, and the class II MnS change into class III MnS, which is beneficial for improving the free-cutting property of steel and to reduce anisotropy. With the addition of Te, MnS of other shapes, such as heart, water drop, butterfly, etc. of a length–width ratio of less than 4 also appeared as MnS and MnTe complex inclusions, and the fusiform manganese sulfide accounted for most of the steel. Both Bi and Te had modification effects on MnS. [ABSTRACT FROM AUTHOR]

This paper compares the microstructure and mechanical evolution in a high-strength quenched and micro-alloyed steel during the austenitising bending process. Simulation results indicated a new finding that the stress neutral layer (SNL) tends to move to the tension zone during straining. The hardness gradient detected from the centre to compression/tension zones was resulted from comprehensive factors: First of all, the location of SNL revealed a prominent impact on strength. Second, the dislocation accumulation would be responsible for the hardness gradient on the surfaces. In addition, the overall strength decrease during straining was mainly ascribed to integrated effects of dynamic recovery (DRV) and dynamic recrystallisation (DRX). Apart from that, overall smaller martensite packet size and coarser prior austenite grains resulted in the increased hardness value at a lower bending degree. Also, the high consistency between experimental and simulation results is instructive for the practical forming process of railway spring fasteners. [ABSTRACT FROM AUTHOR]

The construction of heavy polar icebreakers is usually done with special hull steels, which require comprehensive properties such as good low-temperature toughness, high strength, and superior fatigue resistance. Reasonable and satisfactory heat treatments should be investigated and applied to acquire the required high strength and superior low-temperature toughness, since this is deemed an effective approach to ameliorate the combined properties of high-strength hull steels. Regarding this, the present study specifically explores the effects of different laboratory-based quenching (850 to 930 °C) and tempering (580 to 660 °C) heat treatments on the final low-temperature toughness of the high-strength hull steels. The low-temperature toughness is eventually improved without significantly sacrificing the strength. The results show that a favourable combination of properties can be obtained in the specimens under 900 °C quenching and 660 °C tempering processes. Additionality, the specimens tempered at 620 °C present the highest hardness, owing to the higher percentage of tempered martensite. Detailed mechanisms of the enhanced properties of the typical specimens subjected to the corresponding quenching and tempering processing are analysed and explicated. [ABSTRACT FROM AUTHOR]

The formation and performance of oxide scale on a low-alloy steel were investigated during hot rolling at 850 and 950 °C under various lubrication conditions, including benchmarks (dry condition and water) and water-based nanolubricants containing various concentrations of nano-TiO2 from 1.0 to 8.0 wt%. The results showed that the addition of nano-TiO2 particles in the lubricant significantly reduced the thickness of oxide scale and surface oxide roughness. The reduction reached the maximum when the concentration of TiO2 was 4.0 wt%. Detailed oxide phase characterisation and oxide component fraction determination revealed that hot rolling destroyed the conventional multi-layer oxide scale and promoted magnetite and haematite formation because of easy access of oxygen from the deformed structure. The effect of TiO2 was explained by the decrease in the rolling force, which led to a higher fraction of dense retaining wustite and therefore reduced the extent of further oxidation. Increasing temperature did not change the trend of lubrication effect but raised the rate of steel oxidation in general. [ABSTRACT FROM AUTHOR]

The comprehensive effect of strain and ausforming temperature on the martensite start temperature (MS) of a medium-carbon bainite steel was investigated by thermal simulation, optical microscope, scanning electron microscope, etc. It is already known that small strain increases the MS, while larger strain decreases the MS. However, the effect of ausforming temperature on the MS has not been reported and clarified. In this study, the concepts of critical strain (εc) and saturated strain (εs) are proposed. The MS at the critical strain is equal to the MS of the nondeformed specimen. The saturation strain, which is first observed, is the strain value, and the MS does not further decrease with the increasing strain. The results show that the MS depends on the strain amount of ausforming but is not affected by the ausforming temperature. Moreover, with the increase of strain amount and ausforming temperature, the length of the martensite laths decreases. In addition, the hardness of the specimen increases with the increase of the ausforming strain amount, whereas the ausforming temperature has little effect on the hardness. [ABSTRACT FROM AUTHOR]

Cermet and steel material bonding is a challenging task, due to their large difference of physical properties, e.g. coefficient of thermal expansion. In this study, a hot compaction diffusion bonding method was employed to fabricate a small-dimensional bimetallic composite of WC-10Co and high strength AISI 4340 steel, where the cermet was used in powder form and the steel as solid. The bimetal composite was characterised by microstructural analysis and mechanical properties evaluation. The interface microstructure reveals a successful metallurgical bonding between the cermet and steel materials. The influence of sintering temperature (1050–1250 °C) was examined at intervals of 50 °C. This study shows that the properties of sintered powder and the bonding quality with the steel improve with an increase in sintering temperature. A bonding beneficiary reaction layer was observed to grow at the joining interface by mutual diffusion of the alloying elements, which increases with the increasing temperature. The maximum width of the reaction layer observed was 4.13 μm and consists mainly of intermetallic ternary carbides. The bonding shear strength of the interface is found to be slightly higher than claimed in previous studies. The developed bimetal composite could be used in applications where a combination of high strength and hardness is required. [ABSTRACT FROM AUTHOR]

This work presents a fine microstructure and local misorientation study of various oxide phases in the tertiary oxide scale formed on a hot-rolled steel strip via electron back-scattering diffraction (EBSD). Local strain in individual grains of four phases, ferrite ( α -Fe), wustite (FeO), magnetite (Fe 3 O 4 ) and hematite ( α -Fe 2 O 3 ), has been systematically analysed. The results reveal that Fe 3 O 4 has a lower local strain than α -Fe 2 O 3 , in particular, on the surface and inner layers of the oxide scale. The multiphase oxides along the cracking or α -Fe 2 O 3 penetration generally develop a high local misorientation. Localised stain along the cracks demonstrates that the misorientation tends to be strong near grain boundaries. The high fraction of small Fe 3 O 4 grains accumulate at the oxide–substrate interface, which leads to a dramatic increase in the intensity of local stain. This variation is due mainly to the phase transformation among the oxide phases, i.e., the Fe 3 O 4 particles during their nucleation and growth. The combined action of stress relief and re-oxidisation is proposed to explain the formation of Fe 3 O 4 seam at the oxide–steel interface. The present study offers an intriguing insight into the deformation behaviour of the tertiary oxide scale formed on steels, and may help with understanding the stress-aided oxidation effect of metal alloys. [ABSTRACT FROM AUTHOR]

Severe sticking occurs in the hot rolling of ferritic stainless steel B445J1M. The characteristics of the oxide scale on the steel in hot rolling are associated with this phenomenon. The tensile failure of the oxide scale formed on the steel B445J1M was investigated by using a Gleeble 3500 thermo-mechanical simulator over temperature range from 1000 to 1150 °C in humid air. Two passes hot rolling were carried out on a 2-high Hille 100 experimental rolling mill. The results show that the temperature is a significant factor for the formed thickness of the oxide scale and its failure in tensile stress. On the specimen before hot rolling, irregular spinels are extruded from the surface of a thin oxide scale with Cr 2 O 3 as its main component, which are hard and brittle at lower rolling temperature. [ABSTRACT FROM AUTHOR]

High-speed steel (HSS) materials are universally used as work rolls for the hot rolling of stainless steels. Their use has increased the output of the rolling mill and decreased roll material consumption and grinding. Sticking defects often occur, however, during the hot rolling process. In this article, extreme pressure (EP) additives were dropped on the HSS samples at high temperature. Zinc dialkyl dithiophosphate (ZDDP) was chosen as the most effective EP additive by scratch tests on the HSS samples. In order to determine the optimum proportion of ZDDP in the lubricant, two reduction rates were tested on a Hille 100 experimental rolling mill by hot rolling ferritic stainless steel 445J1M at five different concentrations of ZDDP. The mechanism of EP additive action during the hot rolling process was also investigated. By analyzing the deformation behavior of the oxide scale of samples after hot rolling using different proportions of ZDDP, it was found that 20% ZDDP in the lubricant is the preferred concentration for industrial application. [ABSTRACT FROM PUBLISHER]

Extreme pressure (EP) additives form reasonable hard films by reacting with metal surfaces and are a good alternative to protect the surface of metals exposed to various types of wear. In this paper, the chemical reactions between high-speed steel (HSS) roll material and various EP agents, such as those containing sulfur, chlorine and zinc dialkyl dithio phosphate (ZDDP), were investigated by dropping EP solutions on the heated HSS samples. The research results show that the sulfur element from the sulfur EP solutions was found in the substrate and the carbides. However, the chromium element could not be detected in the sample, and the decomposition products of the ZDDP covered the sample. The scratch tests were carried out to demonstrate that the ZDDP is more resistant to scratching than other EP agents. [ABSTRACT FROM AUTHOR]

In the current study, the effects of tungsten (W) addition on the microstructure, hardness, and room/low [223 K and 173 K (−50 °C and −100 °C)] temperature tensile properties of microalloyed forging steels were systematically investigated. Four kinds of steel specimens were produced by varying the W additions (0, 0.1, 0.5, and 1 wt pct). The microstructure showed that the addition of W does not have any noticeable effect on the amount of precipitates. The precipitates in W-containing steels were all rich in W, and the W concentration in the precipitates increased with the increasing W content. The mean sizes of both austenite grains and precipitates decreased with the increasing W content. When the W content was equal to or less than 0.5 pct, the addition of W favored the formation of allotriomorphic ferrite, which subsequently promoted the development of acicular ferrite in the microalloyed forging steels. The results of mechanical tests indicated that W plays an important role in increasing the hardness and tensile strength. When the testing temperature was decreased, the tensile strength showed an increasing trend. Both the yield strength and the ultimate tensile strength obeyed an Arrhenius type of relation with respect to temperature. When the temperature was decreased from 223 K to 173 K (from −50 °C to −100 °C), a ductile-to-brittle transition (DBT) of the specimen with 1 pct W occurred. The addition of W favored a higher DBT temperature. From the microstructural and mechanical test results, it is demonstrated that the addition of 0.5 pct W results in the best combination of excellent room/low-temperature tensile strength and ductility. [ABSTRACT FROM AUTHOR]

Using a period immersion wet/dry cyclic corrosion test, in-situ copper-coated steels prepared by corroding copper-bearing steels were investigated in this study. The steel with a higher copper content (>3%) has a higher initial corrosion rate due to its obvious two-phase microstructure. The corrosion rates of all copper bearing steels tend to be stable after a certain time of corrosion. A copper-rich layer is formed between the matrix and the rust layer, which is due to the diffusion of copper from the rust layer to the metal surface. The copper's stability under this corrosion condition led to the formation of a thin copper-rich film, which was uncovered after removing the rust by choosing appropriate descaling reagents. The copper coating was generated from the matrix itself during the corrosion process at 25 °C, which provided a new approach for producing in-situ composite materials without any bonding defect. It is found that the corrosion rate, corrosion time, and copper content in steel all affect the formation of copper-rich layer. In addition to the noble copper surface, the electrochemical corrosion test results show that the corrosion resistance of copper-coated steel has been significantly improved. [ABSTRACT FROM AUTHOR]

In this paper, electrochemical corrosion tests and full immersion corrosion experiments were conducted in seawater at room temperature to investigate the electrochemical corrosion behavior and the corrosion mechanism of high-strength EH47. The polarization curve, EIS (electrochemical impedance spectroscopy), SEM (scanning electron microscope), and EDS analyses were employed to analyze the results of the electrochemical corrosion process. The electrochemical corrosion experiments showed that the open circuit potential of EH47 decreases and then increases with an increase in total immersion time, with the minimum value obtained at 28 days. With an increase in immersion time, the corrosion current density (Icorr) of EH47 steel first decreases and then increases, with the minimum at about 28 days. This 28-day sample also showed the maximum capacitance arc radius, the maximum impedance and the minimum corrosion rate. In the seawater immersion test in the laboratory, the corrosion mechanism of EH47 steel in the initial stage of corrosion is mainly pitting corrosion, accompanied by a small amount of crevice corrosion with increased corrosion time. The corrosion products of EH47 steel after immersion in seawater for 30 days are mainly composed of FeOOH, Fe3O4 and Fe2O3. [ABSTRACT FROM AUTHOR]

In this study, WC-Ni/high-speed steel composite materials for application as micro-drills were prepared by cold pressing and high-temperature vacuum sintering using a self-designed mold in the laboratory. The effect of Ni on the microstructure and diffusion behavior at the interface of the WC/high-speed steel composite was investigated. The results show that the addition of Ni promoted the diffusion of elements, and reduced defects such as micropores and microcracks at the WC/high-speed steel composite interface. It also improved the bonding strength of the WC/high-speed steel composite interface, and significantly decreased the WC hardness. [ABSTRACT FROM AUTHOR]

The macroscopic formability of advanced high strength dual-phase steels (AHSDPSs) relies highly on the microstructure. Therefore, building the relationship between the microstructure and the formability is vital to enhancing the formability by microstructure optimisation. In this study, a formability model based on microstructure for AHSDPSs was proposed. The tensile simulation of representative volume element (RVE) was implemented to acquire the stress-strain curve (SSC). The forming limit curve (FLC) was constructed based on the method developed in our previous research. The simulation of hole-expansion with the pre-damage of the central-hole induced by the blanking process was conducted to obtain the hole-expansion ratio (HER), in which the vital failure model is developed based on the simulated FLC. For a typical advanced high strength dual-phase steel of DP1180 steel, the prediction errors of SSC, FLC and HER are 5.83 %, 6.85 % and 10.71 %, respectively. The results also depicted that the damage of the prefabricated hole has a noticeable influence on the HER, which could not be ignored for the hole-expansion simulation. [ABSTRACT FROM AUTHOR]

In this paper, an experimental simulation of oxidation scales during hot strip rolling was carried out on a GLEEBLE-3500 thermo-mechanical simulator. Specimens were exposed to an oxidizing water vapour mixture for different exposure times from 0.6 to 160 s isothermally at 800, 900 and 1000 °C, respectively under atmospheric pressure, which are representative duration of time for oxidation on a hot finishing mill. The oxidation kinetics was analyzed and a prediction of scale thickness as a function of oxidation time and temperature has been obtained. Phase compositions and macrostructure of the surface oxide films formed during the oxidation were investigated by microscope image analyzer and X-ray diffraction. A Nanoscope IIIA atomic force microscope (AFM), was also used to examine the 3-D surface profiles before and after oxidation. The surface characteristics of the oxide scale were investigated with a power spectrum analysis. [Copyright &y& Elsevier]

In this paper, WC-Co-Ni-Fe (powder)/high-speed steel (solid) composites with a diameter of 3 mm were prepared. The microstructure and microhardness of WC-Co-Ni-Fe/HSS composites at different sintering temperatures were studied. The results indicated that with the increase of sintering temperature, the number of micropores in the WC area decreased significantly, and the mutual diffusion trend of Co, Ni and Cr elements increased. In addition, with the increase of sintering temperature, the microhardness of the WC area increased and the microhardness of the HSS area was practically unchanged. The WC zone was more heat-resistant than the high-speed steel region in the heating process of the WC-Co-Ni-Fe/HSS composite. The composite interface began to melt at the temperature of 945.3 °C. When the temperature of the WC-Co-Ni-Fe/HSS composite reached 1341.3 °C, the high-speed steel and WC zone were completely separated. [Display omitted] • WC-Co-Ni-Fe/High-speed steel layered composites were successfully prepared. • Small-diameter composites were obtained by partially replacing Co with Ni and Fe as adhesives. • The diffusion between elements is helpful to realize the stable and firm combination of WC-Co-Ni-Fe/High-speed steel. • The temperature reaches 1341.3 °C, the interface between WC-Co-Ni-Fe and HSS is completely separated. [ABSTRACT FROM AUTHOR]

• The proposed approach can directly connect the microstructure with FLC. • The newly proposed method can determine the constitutive model of the constituent phase. • f 0 of the M-K model should not relate to the roughness of sheets. • The FLC on the left-hand side is overestimated based on the Nakajima simulation without damage model. A multiscale approach was proposed to predict the macroscopic forming limit of Q&P980 steel. The microstructure-based simulation was implemented in the microscopic simulation to obtain the macroscopic stress-strain curve. The representative volume element (RVE) was established using the data extracted from the characterised results of electron back-scattered diffraction (EBSD). The microscopic constitutive model of each constituent phase was determined based on a new method. The acquired macroscopic stress-strain curve was extrapolated using the modified Power-Law (MPL) strain hardening model. In the macroscopic simulation, the Nakajima and Marciniak-Kuczynski (M-K) simulations were combined to obtain the macroscopic forming limit only based on the macroscopic stress-strain curve. The microscopic and macroscopic simulations show good agreement with the experiment results, verifying the multiscale approach's accuracy. This study provides a solution for the direct connection between the microstructure and macroscopic forming limit. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, wear and friction behaviour of high-speed steel (HSS) and indefinite chill (IC) material for rolling a ferritic stainless steel were investigated on a tribometer. A disk specimen of the ferritic stainless steel-B445J1M was pre-oxidised at 1100 °C for 30 min, and then rotated against a pin at 500 °C for 30 min. The pin was made of HSS or IC material. It was found that the friction coefficient of the IC was lower than that of the HSS, but the mass loss of the HSS pin was less than that of the IC pin. The oxide scale of the disk was more easily worn out and attached on the HSS pin than that of the IC pin. [ABSTRACT FROM AUTHOR]

In this study, a small-dimensional layered composites of WC-Co-Ni and stainless steel (SS 304) were obtained by self-made mold, in which the cermet was used in powder form and the steel as solid with a diameter of 1 mm. The effects of holding time (60–120 min) on the microstructure, bonding interface, element diffusion, microhardness and wear of WC-Co-Ni/stainless steel composite were examined under the sintering temperature of 1300 °C. This study shows that the microstructure and diffusion behavior reveals a successful metallurgical bonding between the WC cermet and stainless steel. With the increase of holding time, the mutual diffusion of alloy elements is enhanced, the density and microhardness of the composite are increased, and the loss of wear is reduced. An average maximum hardness of 1500 HV was found at the holding time is 120 min. There are crack clusters at the interface of WC-Co-Ni/SS composite when the holding time is 120 min. • WC-Co-Ni/Stainless steel layered composites were successfully prepared. • The diffusion between elements is helpful to realize the stable and firm combination of WC-Co-Ni/Stainless steel. • The holding time (60–120 min) greatly affects the microstructure and mechanical properties of the composites. • The microhardness of WC near the bonding interface is higher than that in other regions. [ABSTRACT FROM AUTHOR]

A method is proposed to determine the accurate constitutive model of individual phase in multiphase steel with small phase size. The nanoindentation tests with continuous stiffness method (CSM) were implemented to obtain the hardness-displacement curves of the advanced high strength steel DP1180. The validity of the nanoindentation results was evaluated based on the EBSD results and classic indentation size effect (ISE) model. The extra loading of loading-displacement curves due to geometrically necessary dislocations (GNDs) was excluded based on the simple established model. The constitutive model of each phase was determined based on the corrected loading-displacement curves using the inversion method. The results of microstructure based simulation agree well with those of tensile tests, which proves the reliability and accuracy of the constitutive model of individual phase obtained from the method proposed in this study. [ABSTRACT FROM AUTHOR]

• WC-Co-Ni-Fe/High-speed steel (Cermet / steel) layered composites were successfully prepared. • The diffusion between elements is helpful to realize the stable and firm combination of WC-Co-Ni-Fe / High-speed steel. • When the sintering temperature is 1250 °C, a bonding phenomenon called reaction layer occurs. • The sintering temperature greatly affects the diffusion depth of WC / HSS elements. In this study, the layered composites of the micro bit with WC-Co-Ni-Fe as outer material and high-speed steel (HSS) as inner material were prepared by self-designed mold in the laboratory. The effects of sintering temperature on microstructure, interfacial element diffusion and microhardness of WC-Co-Ni-Fe/HSS composites were studied. The results show that with the increase of sintering temperature, the number of micropores in WC-Co-Ni-Fe/HSS composites decreases, the mutual diffusion trend of Co, Ni, Cr and Mo at band area increases, and W element has no obvious diffusion in band area. When the sintering temperature is 1250 °C, a reaction layer with a certain width begins to form at the interface between the WC-Co-Ni-Fe and high-speed steel, and the two materials are metallurgical bonded. When the sintering temperature was 1310℃, micropores were observed at the interface. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel designed austenitising bending process was realised on a thermomechanical simulator. • Integrated effects of SNL, martensite packet, PA grain, DRV and DRX were responsible for the strength gradient. • Parent grain reconstruction and martensite variants can be achieved a more effective technique. • The high consistency between simulation and experiments means valuable reference of the current study to simulate rail clip forming process. A systematic study was carried out on a novel designed austenitising bending process to explore the effects of quenching temperatures on the evolution of microstructure and mechanical properties of high-strength micro-alloyed steel. Results reveal that the qualified parts could be bent into a satisfactory shape without spring-back and cracks in bending temperatures of 850–1000 °C. The simulation was applied to predict the equivalent stress, stress neutral layer (SNL) and plate thickness. Strength presents a decreasing trend with the increase of bending temperature owing to integrated influences of high-temperature dynamic recovery (DRV) and dynamic recrystallisation (DRX). Beyond that, SNL nearby the geometrical centre line throughout the plate thickness and dislocation pile-ups on the tension/compression zones are responsible for the smaller hardness on middle regions while higher hardness on the surface areas. Through austenite reconstruction, a smaller martensite packet size would directly improve the strength of the plates bent at a lower temperature. The prior austenite size may be related to the appearance of martensite variants but not necessary. Furthermore, the high accuracy by comparing the experimental results with simulation would provide a high-value reference for the practical manufacturing process of railway spring clips. [ABSTRACT FROM AUTHOR]

This article explores the characteristic flow behaviour and microstructure analysis of Si–Cr spring steel under various compression conditions by a Gleeble 3500 facility. To better simulate the abrupt and complex compression during the hot forming process, three compression strain rates (0.01 s−1, 0.1 s−1, and 1 s−1) and four compressive temperatures (850, 900, 950 and 1000 °C) were selected. The outcomes exhibit the intragranular dislocation cells and pile-up along the subgrains were formed during the dynamic recovery (DRV) progress. The dynamic recrystallisation (DRX) of the experimental steel arose with a higher value of the compression temperature. On this basis, a strain-compensated constitutive model considering the compression activation energy and a linear correlation between the Z parameter and DRX grain size are both established according to the strain-stress curves. The constitutive model is further verified by the multiple sets of hot deformation data and exhibits a good agreement between experimental and predicted points with an excellent correlation coefficient of 0.986 and a low relative error of 5.41%, indicating the reliability of the constitutive model throughout the entirety of the hot deformation process. • The flow behaviour and microstructure evolution of a commercial Si-Cr micro-alloyed spring steel under various hot compression conditions were investigated. • The dislocation mechanism were investigated during the high-temperature dynamic recovery (DRV) progress. • A strain-compensated constitutive model considering the compression activation energy and a linear correlation between the Z parameter and DRX grain size were both established according to the strain-stress curves. • The established constitutive model in a good agreement with experimental results will provide a valuable reference for the further manufacturing design and simulation of a spring fastener in the high-speed railway system. [ABSTRACT FROM AUTHOR]