Cold Radial Forging Research Articles

Intelligent optimization of cold radial forging process for 20CrMnTiH alloy based on GA-BP and performance analysis

Intelligent optimization of cold radial forging process for 20CrMnTiH alloy based on GA-BP and performance analysis

Evolution of Gradient Structure Under Heat Treatment of Metastable Austenitic Stainless Steel Subjected to Cold Radial Forging

Evolution of Gradient Structure Under Heat Treatment of Metastable Austenitic Stainless Steel Subjected to Cold Radial Forging

Evolution of the Structure, Texture, and Mechanical Properties of Austenitic Stainless Steel during Annealing after Cold Radial Forging

Evolution of the Structure, Texture, and Mechanical Properties of Austenitic Stainless Steel during Annealing after Cold Radial Forging

Investigation of Through-Thickness Residual Stress, Microstructure and Texture in Radial Forged High-Strength Alloy Steel Tubes

Gradient variations of through-thickness residual stress, microstructure and texture greatly affect the performance of cold radial forged tubes. In this work, the through-thickness distribution of residual stress was measured based on the Debye ring. The microstructure was characterized with the electron backscattering diffraction technique. The texture was measured by the X-ray diffractometer. The influence of microstructure and texture on the strength and anisotropy of forged tubes with different thickness reductions was analyzed. The results show that the residual stress varies gradually from compressive to tensile from the outer to inner surface. The microhardness of the outer surface is lower than the inner. The dislocation density and low-angle grain boundary fraction are the smallest in the one-third thickness. The dislocation density and low-angle grain boundary fraction increase gradually from the one-third thickness to the inner surface. The main texture components of the forged tube include {111}<110>, {001}<110> and {114}<110>. Texture {111}<110> deflects gradually toward {114}<110>, {112}<110> and {110}<110> from the external tube to the internal tube. The gradient variation of strength mainly resulted from the difference of the dislocation density. The difference of strength along the radial direction is reduced with a larger thickness reduction. This work has important significance for improving the performance of high-strength alloy steel tubes processed by cold radial forging.

Evolution of Residual Stress and Microstructure during Annealing of 30SiMn2MoVA High-Strength Alloy Steel Tube Processed by Cold Radial Forging

Evolution of Residual Stress and Microstructure during Annealing of 30SiMn2MoVA High-Strength Alloy Steel Tube Processed by Cold Radial Forging

The microstructure, texture evolution and plasticity anisotropy of 30SiMn2MoVA high strength alloy steel tube processed by cold radial forging

Cold radial forging is an efficient and high-precision process for producing rotary parts such as axles and gun barrels, etc. 30SiMn2MoVA high strength alloy steel is a kind of fine pearlite steel usually used for moulds and barrels. This work focused on the effect of the cold radial forging on the microstructure, texture evolution and plasticity anisotropy of forged steel tube under different forging reductions. The results suggest that most banded structures that are parallel to the axial direction are developed by the radial forging process. The grains are elongated and refined after forging. The increase of dislocation density with the increase of deformation is the reason for grain refinement. Refined grains and high dislocation lead to high strength. Meanwhile, anisotropy was obvious and was exacerbated by the growth of the forging deformation. The circumferential strength and elongation are inferior to the axial. With the increasing of forging ratios, the α-fiber texture is well developed. The relationship between the volume fraction of texture and plastic strain was built. It can predict the volume fractions of the main texture components in the cold radial forged 30SiMn2MoVA steel tube. The Taylor factors of the main orientations were calculated. The {111}<011>(γ-fiber), {110}<110>, {111}<110>(α-fiber), {114}<110>, {112}<110> and {223}<110> texture components help to enhance the axial yield strength. Comparing the ratio of the axial average Taylor factor and the circumferential average Taylor factor with the yield strength ratio, it is found that yield strength anisotropy is not well predicted only taking into account the crystal texture. The effect of banded structures on the strength should also be considered.

Experimental Study of Mechanical Properties of 30SiMn2MoVA Steel Gun Barrel Processed by Cold Radial Forging

Abstract This work focused on the mechanical properties of 30SiMn2MoVA high strength steel gun barrel processed by cold radial forging. Three states of the tube made of this material (the state without forging, the as-forged state without annealing, and the as-forged state with annealing) were chosen to compare the axial and circumferential mechanical properties. As a result, anisotropy was found at as-forged state. The circumferential mechanical properties were inferior to the axial. The circumferential yield and tensile strength were about 150 MPa lower than the axial after forging, and the axial elongation was 155% higher than the circumferential. Even after annealing, the circumferential elongation cannot be restored to the same level as the state without forging. The reasons for anisotropy were investigated by the microstructure. The banded structure along the axial direction was observed in the forged barrel. Meanwhile, the crystalline grains of the forged gun barrel had the highest intensity of {111}〈110〉 texture which meant the grains had obvious preferential orientation. The relationship between crystallographic texture and yield strength was analyzed based on the Schmid factor. Additionally, the elastic limit internal pressure of anisotropic gun barrel was calculated, and it was lower than that under isotropic condition.

Evolution of Structure and Properties of Multiphase Low-Carbon Steel During Cold Radial Forging

The structure and mechanical properties of low-carbon steel 10Kh3G3MFS after cold radial forging with 20, 40 and 60% deformation are studied. The initial (multiphase) condition of the steel is provided by quenching from the intercritical temperature range. The effect of the degree of the deformation on the characteristics of strength, ductility, impact toughness, micromechanism of fracture and parameters of the substructure of the steel is determined.

Structural and Fractographic Features of Formation of Splits in Low-Alloy Steel Subjected to Thermal Deformation Treatment

The structure and micromechanism of crack growth in steel 09G2S are studied after heat and thermal deformation treatments involving cold radial forging (CRF) with 55% total deformation and subsequent annealing at 300 and 600°C. A method for electron microscope panoramic X – Y – Z joining of images of a fracture surface with level difference up to 3 mm is developed and tested. The structure under a fracture surface of steel 09G2S after CRF and annealing at 300°C is studied. The positive role of bands of adiabatic shear forming in the structure under cold radial forging in dispersion of the steel is demonstrated. Special features of the micromechanism of crack growth due to formation of splits are determined.

Cold Resistance of Structural Steel Subjected to Cold Radial Forging

Cold Resistance of Structural Steel Subjected to Cold Radial Forging

Structure, Mechanical Properties and Fracture Surface Features of Structural Steels Subjected to Deformation-Heat Treatment

A comparative study is made of the structure, mechanical properties and crack growth micromechanisms of 09G2S, 25 and 35X steel pipes after different versions of deformation and heat treatment, including cold plastic deformation of highly tempered material by radial forging and subsequent annealing. It is established that the maximum strength of the test steels is achieved after cold radial forging (CRF) with a degree of deformation of 55% and subsequent annealing at 300 °C. It is shown that CRF and annealing at 600 °C leads to formation of an ultra-fine-grained structure as a result of which reliability properties are achieved similar to a highly tempered condition with retention of improved strength properties. Features of the structure are revealed that is formed during CRF. The micromechanism of crack growth after heat and deformation-heat treatment is studied. Analysis is provided for elements of the failure surface after dynamic tests.

Metastable Austenitic Steel Structure and Mechanical Properties Evolution in the Process of Cold Radial Forging.

The article presents the influence of structure formation on the properties of 321 metastable austenitic stainless steel in the process of cold radial forging (CRF). The steel under study after austenitization was subjected to CRF at room temperature with degrees of true strain (e) 0.26, 0.56, 1.00, 1.71 and 2.14. It has been shown that structure formation of the studied steel during CRF consists of three stages: formation of the lamellar structure of austenite, formation of the trapezoidal structure, and formation of the equiaxial grain structure. The kinetics of the strain-induced α′-martensitic transformation is related to the stages of structure evolution. Hardness, ultimate tensile strength and yield strength uniformly increase in all stages of structure formation with a significant decrease of elongation to fracture during the first stage of structure formation while the value of elongation to fracture remains constant in the subsequent stages of deformation. Impact strength of fatigue cracked specimens (KCT) decreases sharply at the first stage of structure formation and smoothly increases at the second and third stages. However, the impact strength of V-notch specimens (KCV) continuously decreases when deformation degree increases in the overall investigated deformation range.

Comparative analysis of machine steels structure parameters and dynamic crack resistance after deformation-and-heat treatment

Abstract The structure, impact strength and dynamic crack resistance of pipe billets from structural steels 09G2S, 25 and 35Kh are compared after a heat treatment and after different variants of deformation-and-heat treatment involving plastic deformation by cold radial forging (CRF) and subsequent annealing. The features of the structure formed by CRF processing are revealed and their evolution during subsequent thermal effects is considered. It has been shown that CRF and annealing of initially highly tempered pipe billets at 600 °C leads to formation of an ultra-fine grained structure, thereby achieving reliability characteristics close to the highly tempered state with increased strength characteristics.

Structure, Dynamic Cracking Resistance, and Crack Growth Micromechanism in Pipe Billets after Thermomechanical Treatment

The structure, dynamic cracking resistance, and micromechanisms of crack growth in initially highly tempered pipe billets made of structural carbon steel are studied after thermomechanical treatment, including cold plastic deformation by radial forging followed by annealing, under various conditions. The strength is found to be maximum after cold radial forging followed by annealing at 300°C. Cold radial forging and annealing at 600°C are shown to cause the formation of an ultrafine-grained structure with an average grain/subgrain size of ~900 nm. The structural features formed in both the axial and the transverse direction after cold radial forging have been revealed. The mechanism of crack growth after heat treatment and thermomechanical treatment has been studied. The fracture surface elements formed during dynamic-crackingresistance tests have been qualitatively analyzed.

Dynamic Crack Resistance and Steel 09G2S Tubular Billet Structure After Deformation and Heat Treatment

The structure and the dynamic crack resistance of steel 09G2S tubular billets are compared after a heat treatment and different versions of deformation and heat treatment, including cold plastic deformation by radial forging and subsequent annealing. Radial forging followed by annealing has a favorable effect on strength and dynamic crack resistance, which confirms the possibility of industrial use of tubular billets from steel 09G2S after cold radial forging.

An upper bound solution of forging load in cold radial forging process of rectangular cross-section billet

Investigation in the radial forging process for rectangular cross-section billet is scarce. In this paper, a kind of radial forging method for rectangular cross-section billet is studied. For simplicity, a rectangular cross-section billet, being forged in one hammer stroke at the middle part by two pairs of hammers, is considered. Based on a kinematically admissible velocity field, a three-dimensional model by the upper bound method (UBM) is proposed to predict the forging load in the radial forging process. Because of the non-steady flow of material in one stroke of the forging process, the forging process is divided into finite steps so that each step can be assumed as steady flow. The accuracy of the UBM model is verified by the results acquired through radial forging experiments and that of the three-dimensional finite element simulation. Then, the influences of various process parameters on the forging load and longitudinal flow of material are discussed.

Study on the Mechanical Property of 20Cr13 Stainless Steel Barrel Processed by Cold Radial Forging

The barrel is a key part of automatic weapon. And the cold radial forging progress is a new technology for manufacturing the barrels. It will introduce some changes of the material, such as increased strength, decreased plasticity and introduction of anisotropic mechanical property. It can affect the service performance, so it is necessary to study the difference of tangential and axial mechanical properties of barrel blank and forged barrel. This paper focuses on the research of 20Cr13 stainless steel barrel. The mechanical properties of barrel blank and forged barrel are measured by the tensile, compression and bulging test. And the hardness is measured by Vickers hardness tester. The structural change of 20Cr13 stainless steel also has been observed by metalloscope in the metallographic experiment. It reveals the influence of the cold radial forging progress on the mechanical properties of 20Cr13 stainless steel barrel. And it also provides the reference data of the cold radial forging progress of 20Cr13 stainless steel.

Effect of Structure on the Dynamic Crack Resistance and Special Features of the Micromechanism of Crack Growth in Steel 35Kh After Cold Radial Forging

The structure, dynamic crack resistance, strength and micromechanisms of crack growth are studied in tubular billets from steel 35Kh after different variants of deformation and heat treatment including cold plastic deformation by radial forging followed by annealing. The radial forging with subsequent post-deformation annealing is shown to affect positively the strength and the dynamic crack resistance of the metal. Quantitative analysis of the micromechanism of crack growth is made after tests for dynamic crack resistance. Special features of the formation of macro-splits are determined.

Prediction of Residual Stresses for a Hollow Product in Cold Radial Forging Process

Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axles and also for creating internal profiles such as rifling the gun barrels. The radial forging of tube is usually performed over a mandrel to create an internal profile and/or size the internal diameter. Most of the previous studies conducted on the radial forging process have used axisymmetric models. In this research, residual stresses of a short hollow tube in a cold radial forging process are investigated using 3-D finite element simulation. In this study, a mandrel with six helical grooves and two steps along its length is used. This kind of mandrel is innovated in this research. The workpiece is modeled as an elastic-plastic material and the commercial finite element software, ABAQUS is used to simulate of the process. The accuracy of the model is tested by comparing the predicted results with available experimental work and also validated by both slab and upper bound methods. Residual stresses in the radial forged product and the influence of the process parameters on stress distribution, such as workpiece motions, friction and percentage of reduction are studied to determine the optimized parameters of simulation and improve the condition of this process.

An upper bound solution of axial metal flow in cold radial forging process of rods

Abstract In process design of radial forging, the prediction of axial metal flow, which has an effect on the forging efficiency, is very important. In this paper, based on a kinematically admissible velocity field, an axisymmetric model of radial forging of rods by an upper bound method (UBM) is proposed. Because the deforming process in a stroke is non-steady, it is divided into finite small steps so that the deformation in a step can be assumed as homogeneous steady flow. In addition, front-pull and back-push forces are taken into account. The amounts of metal flowing forward and backward can be predicted reasonably. The UBM model is validated by comparing the predicted forging load with published experimental data, and by comparing the predicted neutral plane position and axial metal flow with that of finite element simulation. Then the influences of friction factor, axial feed per stroke, reduction in cross-section area, inlet angle of hammer, front-pull and back-push forces on the percentage of forward material flow are investigated.