Forging Rolling Research Articles

Microstructure, thermophysical properties and neutron shielding properties of Gd/316 L composites for spent nuclear fuel transportation and storage

In this paper, (0.5–5.0 wt%)Gd/316 L composites were prepared by vacuum arc melting, and the microstructure, thermophysical properties, and neutron shielding properties were analyzed deeply. The results showed that the Gd/316 L composites started solidification in primary ferrite mode and terminated solidification by a peritectic-type reaction forming (Fe, Ni, Cr)3Gd that is rich in Ni and Gd. In the peritectic-type reaction, local convection in the Ni-rich and Gd-rich peritectic liquid phase leads to the formation of multiple variants of (Fe, Ni, Cr)3Gd. The higher the Gd content, the greater the amount of (Fe, Ni, Cr)3Gd and ferrite, and the harder it is to keep the austenitic matrix of 316 L stainless steel. The solidification temperature range of Gd/316 L composites is 1074–1460 °C, which severely limits the ability to further process it by high-temperature deformation techniques such as hot rolling or hot forging. (Fe, Ni, Cr)3Gd preferentially nucleates and grows in the triangular region of austenite grain boundaries at 1074 °C. At 50–500 °C, with increasing Gd content, thermal expansion and thermal diffusion coefficients become decrease, and thermal conductivity and specific heat capacity increase. The trend of thermophysical property changes is favorable for SNF transportation and storage applications. The thermal neutron shielding properties of 1.0 wt%Gd/316 L composite is comparable to that of 4.45 wt% B content boron steel and 15 wt%B4C/Al composite. The Gd content in Gd/316 L composites material should not exceed 2.5 wt%. If the Gd content continues to increase, it is of little significance to improving shielding properties and material thinning. A shielding thickness of 3 mm is more appropriate for Gd/316 L composites. Too thin would not provide sufficient mechanical properties and increase processing and manufacturing costs.

An innovative rotary rolling-forging process for manufacturing fork ring with extreme geometry

Fork ring is a key structural component of rocket fuel tank, which is difficult to be manufactured with high performance and high efficiency because of its extreme geometry and strict performance requirement. This paper proposes an innovative rotary rolling-forging (RRF) process to realize high performance and high efficiency manufacturing of fork ring. Firstly, the principle of RRF process of fork ring is proposed by combining the advantages of ring rolling and rotary forging. Secondly, the interference determination criterion of RRF die and fork ring is established and the effective die parameter windows are determined, and consequently the die design method for RRF of fork ring is proposed. Thirdly, the mechanical model for predicting the metal flow in RRF process of fork ring is developed by slab method and the uneven growth mechanisms of three ribs are revealed. It is found that the lower rib is the most difficult to be formed and its height hardly increases because of the large metal flow resistance. Based on the above results, the design method for preformed billet is proposed to realize the growth control of three ribs. Finally, the experiments of RRF of fork ring are conducted and it is verified that the proposed RRF process of fork ring and corresponding process design method are feasible.

Finite Element Analysis and Forming Test of Roll Forging of Thin - wall Inner and Outer Gear Cup

In this paper, a new forming process method for cup-shaped parts with internal and external teeth structure is proposed, and the forming principle is expounded. The forming characteristics of cup-shaped parts with internal and external teeth are analyzed by finite element method. The stress and strain distribution in different regions of internal teeth, external teeth and side wall are studied. The most prone areas of defects are predicted. The process parameters are determined by simulation. The sample trial production is completed on GD 62-380 roll forging machine, and the comprehensive performance test is verified by carrying HPT330 hydraulic automatic gearbox bench.

Metallurgical processing of Mg alloys and MgH2 for hydrogen storage

The reversible reaction of hydrogen with metallic Mg to form MgH2 has been evaluated by more than 70 years, with particular attention in the last 20–30 years for the exceptional properties of this hydride to store energy. The main challenges to the practical use of these properties were soon identified; the high thermodynamical stability of the hydride, resulting in high temperatures for absorption / desorption of hydrogen; the low diffusion rate of hydrogen in Mg and in MgH2, which requires short diffusion distances and therefore, large surface, interface or interphase areas and the presence of catalyst to improve the absorption and desorption kinetics. Thermodynamic stability cannot be modified by the microstructure, which can, however, affect the other above-mentioned challenges. The first Mg samples to react with hydrogen were prepared by conventional metallurgical routes, but with the important addition of being crushed to be smaller than a certain particle size. Turnings of bulk Mg or Mg alloys samples were also used, resulting in the same increase in surface and interfaces area as the crushed particles. Alloys of different compositions, including eutectic alloys were designed to result in a combination of phases, with one of them in conditions to form a hydride and the other to act as catalyst, or most likely just supplying extra interphases for hydrogen diffusion. But since melting of Mg and Mg alloys is not a friendly process, mechanical alloying was considered simpler and more adequate to prepare Mg powders, resulting in the identification of the exceptional properties of nano powders to improve kinetics but also stressing the difficulties of handling nano powders and the deleterious effect of surface contamination. Severe plastic deformation was then used to prepare “bulk” nanograined material with the expectation to design microstructures with special textures and special types of grain boundaries and to avoid the problem associated with surface reactivity. Because of kinetics limitation, the SPD techniques had to be combined with other processing step, such as filing, cold rolling or milling, basically to increase the surface / interface area. Extensive plastic deformation via co-lamination had already been used but the necessity to complement SPD processing led to the use of conventional metallurgical processing such as cold rolling and cold forging to process Mg and MgH2. Such metallurgical routes prove to be simpler and cost-effective to deliver microstructures satisfying the requirement for Mg and MgH2 to act as hydrogen storage material. Other processing routes or combination of routes that could result in refined microstructure have also been studied, including melt spinning, melt spinning combined with HEBM or with cold-rolling, friction stir welding, mechanical grinding and filing and chips from lathe turnings. In this review we discuss the evolution of metallurgical processing of Mg and MgH2 based hydrogen storage material and how each processing route can lead to microstructures with the required characteristics.

High cycle fatigue performance, crack growth and failure mechanisms of an ultrafine-grained Nb+Ti stabilized, low-C microalloyed steel processed by multiphase controlled rolling and forging

An effort has been made to examine the high cycle fatigue (HCF) properties including crack propagation characteristics and related fracture mechanisms of submicron-grained (SG) Nb + Ti stabilized low C steel processed through advanced multiphase-controlled rolling (MCR) and multiaxial forging (MAF). The HCF and other mechanical properties have been correlated with microstructural features characterized by light optical (LOM), transmission electron (TEM) and scanning electron microscopy (SEM), aided with electron backscatter diffraction (EBSD). TEM analysis near the fracture zones of the fatigue tested samples and corresponding fractographic analysis corroborated well in explaining the improved fatigue life of the SG steel. The fatigue strength was found to have a linear relationship with the tensile strength in both types of processed samples. The fatigue strength of the forged specimens was estimated to be nearly twice than that of the untreated annealed steel, demonstrating significantly different fracture characteristics. Intergranular fracture is found to be dominant in the rolled/forged specimens, in comparison to the transgranular fracture observed in the as-received steel. Such variances in fatigue strength and fracture characteristics have been endorsed to their microstructural constituents. Superior combinations of yield strength (YS), tensile strength (UTS), elongation (% El.) and high cycle fatigue strength (σf) (YS = 1027 MPa, %El. = 8.3%, σf = 355 MPa) were obtained in multiphase-controlled 15-cycle multiaxially forged (MAFed) specimens (processed in intercritical α+γ phase regime). An enhancement of the fatigue strength can be ascribed to the formation of evenly dispersed nano-sized fragmented cementite (Fe3C) particles (~35 nm size) present in the SG ferritic matrix (average ~280 nm size). The fine dislocation substructures/cells together with the nano-sized Fe3C particles could efficiently block the initiation and propagation of cracks thereby enhancing the fatigue endurance limit of the steel. Superior mechanical properties together with high fatigue resistance in the SG material render the present steels highly beneficial for high-strength structural applications.

Mechanical properties of carbon steel by compound arc and vibration shock forging-rolling

Abstract To solve problems of coarse grains and low mechanical performance in low carbon steel parts fabricated by wire and arc additive manufacturing (WAAM), a novel compound arc and vibration shock forging-rolling (CAVSFR) method was proposed in this study. Carbon steel components were fabricated by the proposed method. And results showed that the total deformation of 28.3 % was obtained and the average grain size was reduced from 9.6 μm of WAAM to 6.4 μm. Grain refining was attributed to the static-force rolling, vibration-shock forging and micro self-forging of the molten pool. The large deformation in the medium-high-temperature zone, which provided more nucleation sites, accounted for grain refining in both static-force rolling and vibration-shock forging. Vibration shock greatly promoted dendrite fragmentation and more dendrite fragments were obtained as nuclei for new grains. Besides, the larger constitutional supercooling helped these nuclei survive and induced more nucleation, which could refine grains. These two factors were responsible for the grain refining in micro self-forging of the molten pool. What’s more, the refined grains enhanced the strength and plasticity of the material. The ultimate tensile strength (UTS), yield strength (YS) and elongation of the optimized component manufactured using the proposed method were increased to 555 MPa, 391 MPa and 38.9 %, which were enhanced by 14.2 %, 8.6 % and 1.8 % respectively and exceeded that of the wrought low alloy steel with the UTS of 550 MPa. Compared with other methods, small load and simple equipment could obtain components with the high performance through the proposed method.

Influence of Process Parameters on the Forward Slip of Cup during Roll Forming

The effect of friction coefficient, reduction of thickness, forming speed, roller diameter on the coefficient of forward slip at the rim of the roller during cup roll forming was studied by numerical simulation. The results show that during roll pre-forming, the friction coefficient and forming speed have little effect on the coefficient of forward slip, and the reduction of thickness and the diameter of the roller have a greater influence on the coefficient of forward slip; as the reduction of thickness increases, the coefficient of forward slip increases; as the roller diameter increases, the coefficient of forward slip increases first and then decreases. The coefficient of forward slip during the roll pre-forming of cup is much larger than that of roll forging. During roll shaping, the process parameters have little effect on the coefficient of forward slip and its value is close to zero, that is, the axial length of the roll shaped part is almost equal to the arc length of the roller rim. The accuracy of numerical simulation is verified by experiments, and the error between the numerical simulation and experiment is less than 1%.

Influence of the Combined Radial Shear Rolling and Rotary Forging on the Deformation Mode of the Small-Diameter Rod Billet Made of Titanium Alloys

This work is devoted to the finite-element modeling of the deformation mode of a small-diameter rod billet during pressure hot treatment in the combination of radial shear rolling (RSR) and rotary forging (RF). Modeling is performed using a rheological model of the Ti–6Al–4V titanium alloy using the QForm VX program. The combination of RSR for one passage of a billet 15 mm in diameter to a rod 12 mm in diameter and subsequent RF in 1, 2, and 3 passages with the formation of rods 11, 10, and 8 mm in diameter is modeled. The operation-by-operation accumulation of the plastic deformation in nonuniformity conditions of its distribution is taken into account. Intermediate and final plastic deformation fields, deformation rates, and average stresses are found. It is shown that the distribution of the plastic deformation after RSR has the pronounced gradient character with a minimal value (3 and larger) at the cross-section periphery and a minimal value (about 1) in the center. Due to this, RF, even with small reductions, leads to a substantial increase in uniformity of the deformation mode when compared with the billet after the same diameter after radial shear rolling only. In addition, residual tensile stresses decrease due to compressing stresses during RF. The direct experimental approval of the combined deformation method is performed for the promising Ti–Zr–Nb shape memory alloy of medical prescription when fabricating rods 7–8 mm in diameter under pilot production conditions. The results of modeling are qualitatively confirmed by the metallographic analysis. The prospects of a combination of RSR and RF for the development of industrial fabrication technologies of small-diameter rods with a high uniformity of finely dispersed structure are shown.

A new process chain combining cross-wedge rolling and isothermal forging for the forming of titanium alloy turbine blades

Titanium alloy blades are significantly important parts for aero-engine, and their special outline and production status requires an efficient and low-cost production process. In this paper, a new sequence for forming the titanium alloy blade using cross-wedge rolling (CWR) and isothermal forging was proposed. A finite element (FE) numerical model which contains the entire sequence, including the transfer process, CWR process, and isothermal forging process, was developed. And the axial displacement, strain-stress state, and temperature variation were analyzed based on its material properties of titanium alloy. The results showed that the billet experiences a smooth flowing in the center along the axial direction, and no large concavity occurs due to the higher viscosity. Moreover, the chilling effect of the dies was effectively counterbalanced by the deformation-heat near the surface, and there is no larger temperature difference. During the isothermal forging, the flash is symmetrically distributed around the fully filled blade and no obvious forming defects occur. Moreover, the novel sequence contributes to improving the deformed microstructure by accelerating the globularization of the long-strip alpha phase and increasing the volume fraction of the primary alpha phase. The technical feasibility of the novel sequence was verified by the corresponding experiments.

Influence of the combined radial shear rolling and rotary forging on the stress-strain state of the small diameter bar stock of titanium-based alloys

The paper focuses on the finite element method used to simulate the stress-strain state of a small-diameter bar stock during hot-forming in a combination of radial shear rolling (RSR) and rotary forging (RF). Simulation was carried out using the rheological model of the Ti-6Al-4V titanium-based alloy with the QForm VX software. A combination of radial shear rolling of a workpiece with a diameter of 15 mm to 12 mm bar in one pass and subsequent rotary forging in one, two and three passes to obtain bars with diameters 11, 10 and 8 mm is simulated. During the simulation, step-by-step accumulation of plastic deformation was taken into account in the conditions of its nonuniform distribution. The intermediate and finite fields of plastic deformation, strain rate and average stress are obtained. It is shown that plastic deformation distribution after RSR has an expressed gradient with a maximum value (3 or more) at the periphery of the cross-section and a minimum value (about 1) at the center. As a result of RF, even with small reductions, the stress-strain state becomes much more uniform compared with a workpiece of the same diameter after radial shear rolling only. In addition, residual tensile stresses due to compressive stresses during rotary forging are reduced. Direct experimental testing of the combined deformation method was carried out for a promising medical-grade Ti-Zr-Nb shape memory alloy when manufacturing 7-8 mm diameter rods in experimental production conditions. Qualitative confirmation of modeling results is obtained by metallographic analysis. It is shown that the combination of radial shear rolling and rotary forging is promising for creating industrial technologies for the manufacture of small-diameter rods with a highly uniform finely-dispersed structure.

Optimum design of the double roll rotary forging machine frame

Abstract. The equipment to realize the rotary forging technology is called the rotary forging machine. Compared with the common forging equipment, machine frame will bear a large torsion force in the working process, and the load in the forming process will eventually act on the rotary forging machine frame, and cause it to deform, thus affecting the rolling situation of the workpiece. Therefore, good frame performance is the premise to achieve stable rotary forging. The good performance of the frame is closely related to the structural design and structural optimization. However, at present, there are few researches on the overall optimization design of the rotary forging machine, and the lightweight technology has become the current trend. In the early manufacturing of low tonnage rotary forging machine, the lightweight design is not paid enough attention to, even if it meets the use performance, but the machine is bulky, which seriously reduces the utilization rate of materials and increases the manufacturing costs. In this paper, based on the existing rotary forging machine, the topological optimization of the main body of the rotary forging machine is carried out, and then the sensitivity analysis of the thickness of each component of the machine frame to the performance of the frame is studied, which provides the basis for the follow-up size optimization. Finally, the experimental verification is carried out, and it is found that the work pieces of the rotary forging are relatively good, which shows that the optimization scheme is reasonable and can be reduced on the premise of satisfying the performance weight, saving manufacturing cost.

Effect of Primary Carbides on the Sharpness of Kitchen Knives Made of 8Cr13MoV Steel

Although there are many primary carbides in the cutting edge of knives made of high-carbon martensitic steel, the effect of primary carbides on the sharpness of knives has not been clarified. In this paper, the evolution of primary carbides during the production process of 8Cr13MoV steel was presented. The effect of size and amount of primary carbides on the sharpness of knives was studied via employing rolling forging and diffusion annealing process, respectively. Results indicated that primary carbides easily fell off from cutting edge during cutting process, which would decrease the wear resistance of knives. The refinement of primary carbides could not only improve the wear resistance of cutting edge, but also weaken the fluctuation of sharpness during the service process of knives. By decreasing the amount of primary carbides, the wear resistance of knives would increase effectively, which improved the cutting performance effectively. Reducing the amount of primary carbides and refining the primary carbides in cutting edge were both effective ways to improve the sharpness of knives.

Simulation Analysis of Forging Process of Automobile Aluminum Alloy Swing Arm

To effectively shorten product development cycle, cut down the expense and reduce costs, in the production forging process of aluminum alloy swing arm, the technological process of sawing off, high temperature heat treatment, roll forging, blank making, flattening, die forging, residual edge removing and forging inspection are adopted. Taking Deform-3D software as the platform, the forging process of aluminum alloy swing arm is modeled and simulated by finite element method, and the flow law of cold extrusion metal during the forging process of aluminum alloy swing arm is analyzed. The results show that the forging process can achieve a better forming forging, which can provide a theoretical basis for the actual industrial production of forgings.

Advanced Technology for Preparing Bar from Medical Grade Ti-Zr-Nb Superelastic Alloy Based on Combination of Radial-Shear Rolling and Rotary Forging

Prospects are presented for the technology of preparing biomedical Ti–Zr–Nb shape memory alloy 3–8 mm diameter bars more than 2000 mm long using an advanced combination of radial shear rolling and rotary forging. Radial shear rolling parameters are calculated on the basis of technological limitations of true degree and rate of deformation of 0.05–0.5 and 1–5 sec–1 respectively per pass. Full-scale experimental verification of the technology is performed in NITU MISiS 1030 and 1440 radial shear rolling mini-mills with subsequent rotary forging using an RKM2 machine. Bars are obtained with a grain size of ∼ 40 μm demonstrating superelastic behavior at room temperature with a favorable combination of relatively low Young’s modulus (E = 39 GPa) and relatively high strength (σf = 618 MPa). The technology has a high degree of readiness for direct industrial application.

Effect of High Strain Rolling and Multiaxial Forging on Tensile and Fracture Behaviour of ZE41 Magnesium alloy

The present work is focused to study tensile and fracture strength of severely plastically deformed ZE41 Mg alloy and correlate it with the microstructural characteristics of deformed samples. Two types of severe plastic deformation (SPD) were performed such as high strain rolling (75% HSR) and multiaxial forging (6 Pass Forged) followed by high strain rolling (75%HSR). The tensile and fracture properties of deformed samples were compared with as received (AR) and solution treated (ST) samples. The 6 pass forged followed by 75% HSR (6PF75HSR) sample has shown maximum yield strength (YS) and ductility (%E), 250 MPa and 17%, respectively. However, ultimate tensile strength (UTS) of both the SPDed samples was found to be 315 MPa. The fracture toughness (J1C) and hardness of 75%HSR were slightly superior to 6PF75HSR i.e. 11.4 kJ/m2 and 76 HV, respectively. The high tensile and fracture strength of the processed Mg alloy are due to its fine grain size and high dislocation density. The microstructural features characterized by optical (OM) and scanning electron microscopy (SEM) are used to elucidate the improved strength of the processed alloy. The grain refinement was evident from the transmission electron microscopy (TEM) results.

Experimental investigation of different parameters at a combined cross wedge rolling and multi-directional forging process

To forge a flashless crankshaft within few steps and with low energy consumption innovative forging processes are necessary, such as cross wedge rolling and multi-directional forging. The direct combination of the two forming processes normally leads to flash at the bottom of the crankweb preform after the multi-directional forging. The reason for the flash generation is the rotation-symmetric cross wedge rolled billet, which is formed laterally to the main axis during multi-directional forging. In this paper, a parameter field in which flashless crankshaft preforms can be forged is presented. The parameters varied within the experimental research are the forming angle and the cross section area reduction at cross wedge rolling as well as the axis offset, the billet temperature and the forming velocity at the multi-directional forging. The limits of this flashless parameter field are shown in several diagrams. For a flashless combination of two forming process low values for all parameters such as a forming angle α = 30°, a cross section area reduction ΔA = 30%, and a billet temperature T = 1050 °C are recommended. Furthermore, the intensity of the influence of the significant parameters are shown. The cross section area reduction ΔA thereby caused the highest range at flash generation with 0.4 mm.

Konstrukcja i możliwości technologiczne uniwersalnej walcarki kuźniczej

The paper presents selected results of the research related to the development and verification of a multi-purpose construction of forging mill suitable for the following processes: longitudinal roll forging, cross-wedge rolling, and steel bar cropping. Modern CAD/CAE numerical tools have been used to facilitate the design and analysis of the construction. The designed forging mill is characterized by high versatility due to the possibility of two different kinematic processes of roll forging (longitudinal and transverse) as well as semi-products waste-free cropping. Its technological capabilities are considerably higher as compared to the machines currently used in industry. Verification of adopted construction solutions was made during the commissioning tests. The achieved results have fully confirmed the usefulness of multi-task forging mill for rolling forgings and preforms as well as cropping process.

Influence of the cross section area reduction in cross wedge rolling on the multi-directional forging of crankshafts

Low energy demand and fast processing time are required in each industrial process for the production of crankshafts. A crankshaft is a part of combustion engines. It has a very complex geometry and is forged with a high percentage of flash compared to other forging parts. Recent research showed the feasibility of a flashless forging of crankshafts. One way to forge a flashless crankshaft within three steps, is to use cross wedge rolling, multi-directional forging and final forging. This paper presents the investigation results of the influence of the cross section area reduction in cross wedge rolling on different parameters at multi-directional forging. First the state of research, the process development and tool design of cross wedge rolling and multi-directional forging will be described. Then the parameter field study will be presented and the influence of the cross section area reduction on flash, billet temperature, forming degree, forming forces and stress will be shown. Generally, flash develops because a rotation-symmetric billet is forced into an asymmetric movement. The least amount of flash develops at high cross section area reductions (>40%).

Study of the spring back of calibres in material forming processes of roll forging mills

ABSTRACTRoll forging for the preliminary profiling of heated material is one of the methods used to optimise material utilisation and minimise the waste of metal as flash in preforming operations as well as to improve material distribution for the subsequent operations. Processes of roll forging using calibres were presented and the technology using 16 different experiments were analysed to validate the propositions regarding roll forging in multiple stages. The presented process was evaluated using the finite-element method, and an elementary formula was obtained to determine the spring back amount during the roll forging and investigations conducted to analyse the obtained results.

Influence of the forming angle in cross wedge rolling on the multi-directional forging of crankshafts

In each industrial process for the production of crankshafts a low energy demand and a fast processing time are required. Crankshafts have a very complex geometry and are forged with a high percentage of flash compared to other forging parts. Recent research showed the feasibility of a flashless forging of crankshafts. One way to forge a flashless crankshaft within three steps is to use cross wedge rolling, multi-directional forging and final forging. This paper presents the investigation results regarding the influence of the forming angle α in cross wedge rolling on different parameters at multi-directional forging. First, the state of the art is presented. As a basis for the investigations the process development and tool design of cross wedge rolling and multi-directional forging are described. Afterwards the paper’s results regarding the influence of the forming angle α on flash generation, billet temperatures, forming degree, forming forces and effective strain will be presented as a parameter study. Generally, flash is generated because a rotation-symmetric billet is forced into an asymmetric movement. The influence of an increasing forming angle leads to a higher amount of flash at the bottom of the crankwebs.