Forging Method Research Articles

Quality assessment of hybrid aluminum billets jointing using torsional forging method

The producing of hybrid (composite) workpieces made of AMg2 and AMg6 wrought aluminum alloys by torsion forging under deformation conditions at room temperature is considered. The results of the microstructure and microhardness of the composite samples after the plastic deformation are presented. Conclusions are drawn about the possibility of connecting these pairs of materials using torsion forging.

Atmospheric corrosion in the metal pool of Ali Qapu palace in Isfahan: an experimental study

Isfahan, the capital of Iran during the Safavid period (1501–1736 CE), houses the Ali Qapu Palace. It was constructed during the Safavid period to be used as the royal court and a place for settling the affairs of the country. The palace was built in five stages; the final stage was the porch which contains a pool at its centre. The perimeter of the pool is made of white marble, the floor and walls are covered with metal sheets to which the marble is attached. Today, the dry pool is exposed to the urban environment of the metropolis of Isfahan. This study investigates the composition and the corrosion mechanism of the pool using optical microscopy, ICP-OES, SEM–EDS and X-ray diffraction techniques. The results show that the pool’s cover is made of a large number of sheets of copper joined together by copper and lead nails. The forging (cold-working and annealing) method was used to form the sheets. The corrosion products formed on the surface of the copper sheets are copper oxide and copper trihydroxychlorides. The mechanism of corrosion in the metal pool, including copper oxidation, is due to the formation of copper (II) compounds resulting from the reaction with Cl-contaminated airborne particulate matters (dust).

Preparation of high-performance parts of aluminum alloy A7075 by semi-solid forging method

Preparation of high-performance parts of aluminum alloy A7075 by semi-solid forging method

Thixotropic-core compound forging for aluminum-steel bimetal gears

Compound forging is a promising approach for the manufacturing of bimetal parts. However, reliable material interlock is difficult to be obtained in compound forged bimetal parts due to the asynchronous material flow. To overcome this problem, in this work, the previous proposed thixotropic-core compound forging (TCF1) method was applied in the precision forming of a bimetal cylinder spur gear. This investigation focuses on the feasibility of this new forming method. An aluminum alloy core and a steel shell were used as raw materials. The effects of the aluminum alloy core billet status on the material interlock and the shell thickness distribution were studied. Moreover, the microstructures and mechanical properties of the aluminum alloy core in the bimetal gear were investigated. The results suggested that the synchronous material flow could be achieved in the TCF. On this basis, reliable material interlock was obtained. Moreover, the thixotropic core is helpful to improve the uniformity of the shell thickness distribution by diminishing the friction. The liquid segregation in the thixotropic core can be remarkably diminished by the three-dimensional compressive pressures provided by the outer shell during the synchronous material flow. Therefore, uniform microstructure and property uniformities can be obtained in the core of bimetal parts manufactured by TCF. Furthermore, thixotropic core billets with a liquid fraction (fl) lower than the requirements of conventional thixoforming were found to be viable in TCF.

Comparison of the microstructure evolution and mechanical properties via MDF and ITMT methods

Based on the multi-directional forging (MDF) method under decreasing temperature conditions, intermediate thermo-mechanical treatment (ITMT) method was proposed to control the microstructure of the deformed Mg-13Gd-4Y–2Zn-0.5Zr (wt%) alloy and improve its mechanical properties, especially the yield strength (YS). The results showed that compared with the MDF method, ITMT can significantly improve the mechanical properties of the deformed alloy and shorten the process flow. As the number of deformation passes increased, the microstructure became uniform, the average grain size gradually decreased, and the mechanical properties gradually improved during the MDF process. The average grain size of the alloy after 4 passes exhibited a minimum value of 2.4 µm, and the mechanical properties achieved a maximum value with an ultimate tensile strength (UTS) of 357 MPa and a YS of 304 MPa. The average grain size of the deformed alloy first decreased significantly and then slowly increased with an increase in the number of deformation passes via the ITMT method. After 2 passes, the alloy exhibited the minimum grain size and the best mechanical properties after T4-ITMT and T6-ITMT. The minimum grain size was 3.7 µm, and the UTS and YS were 341 MPa and 320 MPa via T4-ITMT method, respectively. The average grain size was 3.1 µm, and the UTS and YS were 356 MPa and 332 MPa via T6-ITMT method, respectively.

Detailed investigation of TiN effect on hybrid intermetallic composites manufactured by combined sinter + forging method

Hybrid intermetallic composites (HICs-aluminum based matrix, new hybrid design) reinforced with titanium nitride (TiN) and alumina (γ-Al2O3) were designed and manufactured through the innovative combined method of sinter + forging. This method results in highly dense materials with, in general, improved mechanical properties. In the composites TiN content was varied (10, 20 and 30 wt %) but γ-Al2O3 content was kept constant at 10 wt%. Additionally, 5 wt% each of Cu and Ni were mixed in to improve processing of the composites. The mechanical properties were specified by different destructive test methods (wear performance, micro hardness, quasi-static compression, three-point bending tests). Wear performance was investigated by scratch experiments. Scanning electron microscopy (SEM) was used to determine the microstructure, interface characteristics and the fracture surfaces. The SEM analysis yielded that TiN powders were located at the grain boundaries and this can be attributed to the improvement observed in the mechanical properties and wear performance with the addition of TiN.

Semi-Solid Forging of Mg Alloy AZX1311 and Mechanical Properties

This paper describes basic property in semi-solid forging method of magnesium alloy AZX1311. In the semi-solid forging process, an arbitrary fraction of solid is selected at a temperature between the liquidus and the solidus line and rapidly cooled and coagulated simultaneously with deformation of the material in a die to obtain a product. In addition, the magnesium alloy AZX1311 has excellent castability and mechanical properties. In recent years, the use of magnesium alloys for home electric appliances and automotive parts has been increasing because weight reduction can be achieved. These main manufacturing methods are casting and forging. However, these manufacturing methods have disadvantages such as large forming load and poor dimensional accuracy. Therefore, the semi-solidification forging method can improve these disadvantages. In this study, a forged semi-solid material and air cooled semi-solid material were produced using a servo press machine. Focused on impurities, porosity and microstructure. A forged semi-solid material could be produced. A semi-solid structure could be observed.

Enhanced oxidation resistance of TiAlNbCr processed by isothermal forging

Poor ductility at room temperature and oxidation resistance at high temperature have hindered the wide usages of TiAl-based alloys, especially in advanced aero-engines. Room temperature ductility of TiAl-based alloys can be improved by grain refinement through the isothermal forging (ISF) method, whereas their oxidation behavior is unknown. In the present study, we investigate the oxidation behavior of TiAlNbCr -casting and -2nd-ISF alloys through the experiment of oxidation weight gain. Structure and phase characteristics before and after oxidation are examined through scanning electron microscopy, transmission electron microscopy and an electron probe microanalyzer. The results indicate that TiAlNbCr-2nd-ISF has higher oxidation resistance than that of TiAlNbCr-casting. The smaller grain size and more uniform structure of TiAlNbCr-2nd-ISF lead to the formation of smaller TiO2 particles on the alloy surface after oxidation, which is beneficial in hindering further diffusion of oxygen.

Compensation of springback error based on comprehensive displacement method in cold rotary forging for hypoid gear

Special cold rotary forging method for the fabrication of the big wheels of hypoid gears is proposed. The proposed method is established on the basis of the requirements of antifatigue manufacturing processes and the tooth profile characteristics of hypoid gears combined with the movement and forming methods of cold rotary forging. The geometric grid model is constructed on the basis of the basic theory of elastic-plastic thermo-mechanical coupling finite element for metal. Reasonable process parameters and boundary conditions are established. Thus, the cold rotary forging finite element model is built. The springback tooth surface is reconstructed through the results of finite element numerical simulation. The size and distribution of the springback error is the detected. In the springback process, a large displacement and large rotation can occur, so a comprehensive displacement compensation algorithm is adopted to modify the rotary forging die, and a springback error compensation iteration system is constructed based on the modified algorithm. In the case of a camion driving axle gear, the correction of the rotary forging die is analyzed. Results show that the error is already within the allowed range through only three iterations, which proves the efficiency of the system. The modified die is used for machining experiments. The measurement results of the experiment gear are consistent with the simulation results, which proves the reliability of the system. The LTCA of the gear further proves its reliability in compensating for springback error using numerical simulation technique.

Improving the quality of forgings based on upsetting the workpieces with concave facets

We propose a forging method for forgings, which implies the upsetting of workpieces with concave facets. A procedure for the theoretical research has been devised aimed at studying the mechanism of closure of artificial axial defects in workpieces. The study was performed based on a finite element method. The key examined parameter was the depth of the concave facets in a workpiece. This parameter varied in the range 0.75; 0.85; and 0.80. The angle of the concave facets was 120°. The results of the theoretical study are the following distributions: deformations, temperatures, and stresses in the body of a workpiece in the process of upsetting the workpieces with concave facets. Based on these parameters, we established an indicator of the stressed state in the axial zone of the workpiece.In order to verify the theoretical results obtained, a procedure for experimental research has been developed. The study was performed using the lead and steel workpieces. The results of the theoretical study allowed us to establish that the effective depth of the concave facets is the ratio of diameters of protrusions and ledges equal to 0.85. At this ratio there occurs the intensive closure of an axial defect. This is due to the high level of compressive stresses when upsetting the workpieces with concave facets. We have established the effective degree of deformation at which the intensive closure of defects takes place. Also established are the distributions of deformations for the cross-section and height of the workpiece, as well as a change in the indicator of the stressed state in the process of upsetting workpieces with concave facets. The closure of axial defects has been confirmed by experimental study using lead and steel samples.The new technique for upsetting workpieces with concave facets has been implemented. The results of ultrasonic testing have allowed us to establish that the obtained parts do not have internal defects, which exceed the requirements of the European standard SEP 1921. Our research has led to the conclusion of the high efficiency of the proposed new method for upsetting workpieces with concave facets, which implies the improvement of quality of the axial zone of large forgings when using a given technique.

Reactive Forging − Pressure Assisted Thermal Explosion Mode of SHS for Processing Dense In Situ Composites and Structural Parts: A Review

Over the last decades, there has been a decisive shift from basic science to applied research that brought about the development of a number of unconventional combustion processes that allow for simultaneous synthesis and consolidation of otherwise difficult‐to‐process high temperature materials. External pressure application during thermal explosion (TE) mode of self‐propagating high‐temperature synthesis (SHS) can produce dense products provided the combination temperature and pressure are sufficient for consolidation. In the developed TE‐based reactive forging (RF) method, a self‐sustained reaction is ignited by rapid heat transfer from press die and rams, and a moderate consolidation pressure is applied when the combustion product still contains a sufficient amount of liquid or very soft phase. Plastic flow of the product results in filling the shape of the die thus producing a near‐net‐shape part. Reactive forging (RF) is especially efficient in combination with the developed short distance infiltration (SDI) approach based on the presence of a low melting phase component (e.g., Al, Mg, Ti–Ni eutectics) in the non‐dense reactant blend that is squeezed into the pores under the applied pressure thereby increasing the interparticle contact area and enhancing exothermic heat release rate. Compared to traditional reactive melt infiltration, SDI has the advantage of the considerably shorter infiltration distances (μm vs. mm–cm). Close temperature monitoring during RF and RF/SDI processing provides a deeper insight into the SHS reaction mechanisms. The “heat sink” action of the pressure die after TE results in rapid cooling of the consolidated products and correspondingly fine microstructures and high mechanical properties. Examples of successful application of the RF/SDI processing of homogeneous and functionally graded in situ composites based on binary (Al2O3, TiB2, TiC, TiN) and ternary (MgAl2O4, Ti3SiC2, Ti3AlC2) ceramics, as well as intermetallic–ceramic and metal–ceramic interpenetrating phase composites are described. Nanostructuring of reactant blends results in lower SHS ignition temperatures, and thus can be utilized for two‐stage ignition of multi‐component composite materials and structures with tunable ignition delay. Pressure assisted SHS is a “green,” cost‐effective, and thus perspective manufacturing route of near‐net‐shape structural parts. Examples of successful application of RF and RF‐SDI approach to fabrication of ceramic matrix–diamond grinding wheels, light armor tiles and high melting temperature nozzles are presented.

A Novel Cold Rotary Forging Method of Producing Multiple Racks Using One Set of Punch

When producing racks by cold rotary forging, the top punch and the rack teeth definitely intervene and thus the top punch has to be amended, which makes the technical designing processes difficult and complex (Han et al., 2016, “Cold Orbital Forging of Gear Rack,” Int. J. Mech. Sci., 117(10), pp. 227–242). In this study, a novel cold rotary forging method of producing racks is put forward to avoid the interventions between the top punch and the racks. Thus, the top punch need not be amended and the technical designing processes correspondingly become simple. In light of this presented method, a novel idea for cold rotary forging of producing multiple racks using one set of punch is motivated. The concrete researches are as follows: First, the mathematical models are developed and three kinds of key forging conditions in cold rotary forging of racks are calculated to avoid the interventions between the top punch and the racks. The first one is the condition that the top punch and the rack teeth do not intervene. The second one is the condition that the top punch and cylindrical surfaces of racks do not intervene. The third one is the condition that the top punch can be successfully constructed. On the basis of these three kinds of key forging conditions, the workpiece is optimized and the cold rotary forging processes of racks with constant and variable transmission ratio are examined using finite element (FE) simulations. The experimental researches are also conducted. The results show that for both racks with constant and variable transmission ratio, the obtained key forging conditions are effective and the presented cold rotary forging principles of producing multiple racks using one set of punch are feasible.

Corrosion resistance of Mg4AlZn alloy aircraft brackets produced by new forging methods

This paper presents the results of a study investigating the corrosion resistance of Mg4AlZn magnesium alloy aircraft brackets produced by new forging methods with a three-slide forging press. The forgings produced by the above processes were subjected to corrosion testing in a 5% NaCl solution for 170 hours at 35°C. Following the corrosion tests, the surface of the forgings was subjected to stereoscopic examination to preliminarily identify corrosion type. In addition, the forgings underwent microstructural examination. The experimental results demonstrate that local pitting corrosion is dominant. The mass decrease in the test samples varies and depends on the employed forging method.

Research on gear tooth forming control in the closed die hot forging of spiral bevel gear

To improve the tooth forming quality of forging spiral bevel gear, a systematic hot forging method for spiral bevel gear is proposed in this paper, which helps to improve some defects in the traditional forging methods, such as the insufficient gear tooth corner filling, the high forming load, and the low die service life. With Deform-3D, the simulation analyses of the closed die structures are carried out to reveal the effects from the tooth forming process parameters, which are including the forging temperature, the strike speed, the die preheating temperature, and the friction coefficient. For further meliorating the addendum of tooth toe-end filling situation, an improved forging process with tooth preformed is presented. Thereinto, the excess material is reserved at the tooth toe-end position in preformed stage, so that the material flow velocity at the tooth toe-end area synchronizes with that at tooth heel-end area. Compared with the traditional process by the numerical analysis, the improved process can not only reduce more than 6% of the forming load but also relieve the sharp rising trend of finish forging load. Finally, the effectiveness of the improved process is verified through the forming experiments, and the results are in good agreement with the simulation ones, which can provide the theories foundation for enhancing the forging quality and decreasing the scrap rate of the forged spiral bevel gear.

Numerical simulation of different types of voids closure in large continuous casting billet during multi-pass stretching process

Abstract Large continuous casting billet always contain void defects which may adversely affect the mechanical properties and safe performance of final products. The void must be completely eliminated during hot forging process. In this paper, different types of void defects in large billet are showed and analyzed. It is found that the voids have different geometry, orientations and positions. Using finite element (FE) software DEFORM 3D, a FE model was developed to investigate the void closure in large continuous casting billet during multi-pass stretching process. The wide die heavy blow forging (WHF) method which has been proved to be an effective method to eliminate void defects was adapted during the stretching process. Then, the stretching processes of various sizes of billets which contained different kinds of void defects were simulated. The closure processes of different kinds of void defects were obtained. The critical forging ratio for large billets from Φ500mm to Φ1000mm was obtained as 2.40. In addition, the void closure evaluation index is analyzed, and the critical value for the closure of all voids is 0.87. The work in this paper is verified by actual production, which illustrates that the simulation results and the proposed criterion in this research are reliable.

Hot Forging Operations of Brass Chips for Material Reclamation after Machining Operations

The production of chips is an inevitable part of any machining operation. Today, brass chips are commonly recycled through re-melting by the material supplier implying a “loop” where material is sent back and forth between the material supplier and the manufacturing company. The research presented in this paper evaluates a method for compaction and hot forging of brass chips into blanks for subsequent machining into a finished product. A series of experiments have been performed to evaluate the method. The results indicate a possibility of a successful hot forging method for brass chips into machining blanks.

Cold orbital forging of gear rack

At present, gear rack is manufactured mainly by cutting method while its precision plastic forming method has not been reported. This paper proposes an innovative cold orbital forging method for manufacturing gear rack, in which the complicated teeth of gear rack are forged by the highly dynamic rocking tool under straight line path. Firstly, a universal method for designing the rocking tool under straight line path is proposed according to the forming mode and contacting mode between the rocking tool and component, i.e., one side of the component is ultimately overall formed by the overall contact (it is achieved by the incremental deformation) between the corresponding side of the rocking tool and component. Based on this universal method, the rocking tool in cold orbital forging of gear rack is accurately designed. Secondly, the mathematical model and method for interference examinations between the rocking tool and gear rack are developed and the interference amount and interference zone are calculated. Thirdly, to eliminate the interference between the rocking tool and gear rack so as to guarantee the forming accuracy of gear rack, a dynamic envelope forming principle is proposed and an innovative forming mode of gear rack is correspondingly developed, i.e., all the time-varying interference zones in the rocking tool are cut one by one and the ultimate tooth surface (planar) of gear rack is incrementally formed by the local contact between a series of modified surfaces (nonplanar) of the rocking tool and tooth surface of gear rack. Based on this proposed dynamic envelope forming principle, the mathematical model and method for modifying the rocking tool are developed and the dynamic envelope forming of gear rack is achieved successfully. The FE simulations and experiments of cold orbital forging of gear rack are conducted. The results demonstrate that the proposed cold orbital forging method for manufacturing gear rack in this paper is effective and cold orbital forging shows great potential in manufacturing gear rack.

Manufacturing of nanostructured Ti-6Al-4V alloy via closed-die isothermal multi-axial-temperature forging: microstructure and mechanical properties

Manufacturing of nanostructured Ti-6Al-4V via a novel severe plastic deformation (SPD) method, named “multi-axial-temperature forging (MATF)” and study of its microstructure and some of its mechanical properties were the aims of this research. In this new technique, known multi-axial forging (MAF) method was developed by a multi-temperature procedure for producing nanostructure in rather brittle materials. Due to room-temperature workability limits and in order to prevent low-temperature embrittlement in Ti-6Al-4V, MATF process was started at elevated temperature of 725 °C, but in order to attain the smallest possible grain size, deformation temperature at subsequent passes was gradually decreased in steps of 75 °C. Grain refinement due to application of MATF was investigated using scanning electron microscopy (SEM). The results show that this process can severely refine the microstructure. The refinement occurred at a variable rate, so that it was significant at the first pass, but reduced substantially at subsequent passes. The average grain size of the final product obtained after the fourth pass was about 100 nm. The results of shear punch and hardness tests show that application of MATF process significantly increased the yield strength up to 50 %, ultimate strength up to 45 %, and hardness up to 26 % relative to those of the as-cast alloy, but it reduced its elongation slightly. The results of this research also show that MATF process facilitates production of nanostructure in low-temperature brittle materials like Ti-6Al-4V alloy by means of SPD techniques.

Experimental Determination of Stress and Deformation Pressure in Nanostructuring Copper by Multiaxial Forging Method

This paper aims to determine by experiment total stress and pressure of deformation depending on punch stroke and the level of deformation on severe plastic deformation of copper Cu_99.75 by multiaxial cold forging. The deformation process is discontinuous and includes deformation processes that define a cycle of severe plastic deformation. This paper aims to determine the stress and pressure corresponding to the first 12 cycles of severe plastic deformation.

Experimental Determination of Force and Deformation Stress in Nanostructuring Aluminum by Multiaxial Forging Method

This Paper Aims to Determine by Experiment Total Force and Stress of Deformation Depending on Punch Stroke and the Level of Deformation on Severe Plastic Deformation of Aluminum by Multiaxial Cold Forging. the Deformation Force in Multiaxial Forging Depends on a Number of Parameters of whom the most Important are: Strain, the Flow Force of Aluminum, Deformation Speed, the Friction between the Material and the Die, Shape and Size of Die, the Dimensions of Deform Profile, Shape and Dimensions of Workpiece, Temperature Variation during the Process, Physical and Mechanical Properties of the Workpiece Material, the Structural Inhomogeneity of Workpiece Material. the Deformation Process is Discontinuous and Includes Deformation Processes that Define a Cycle of Severe Plastic Deformation. this Paper Aims to Determine the Force and Stress Corresponding to the First 12 Cycles of Severe Plastic Deformation.