Precision Forgings Research Articles

Automated defect detection in precision forging ultrasonic images based on deep learning

Ultrasonic testing is a widely used non-destructive testing technique for precision forgings. However, assessing defects in ultrasonic B-scan images can be prone to errors, misses, and inefficiencies due to human judgment. To address these challenges, we propose a method based on deep learning to automate the evaluation of such images. We started by creating a dataset comprising 8000 images, each measuring 224 × 224 pixels. These images were cropped from ultrasonic B-scan images of 7 specimens, each featuring different sizes and locations of holes and crack defects. We then used state-of-the-art deep learning models to benchmark the dataset and identified YOLOv5s as the best-performing baseline model for our study. To address the challenges of deploying deep learning models and the issue of small defects being easily confused with the background in ultrasonic B-scan images, we made lightweight improvements to the deep learning model. Additionally, we enhanced the quality of data labels through data cleaning. Our experiments show that our method achieved a precision of 97.8%, a recall of 98.1%, mAP@0.5 of 99.0%, and mAP@.5:.95 of 67.6%, with a frames per second (FPS) of 74.5. Furthermore, the number of model parameters was reduced by 43.2%, while maintaining high detection accuracy. Overall, our proposed method offers a significant improvement over the original model, making it a more reliable and efficient tool for automated defect assessment in ultrasonic B-scan images.

Problems of the process of manufacturing precision forgings in multiple systems on a hot hydraulic hammer

The article presents the results of a complex analysis referring to a periodical occurrence of forging defects in the form of twisting of pin-type elements (perpendicular to the main forging axis) as well as lack of total filling of these areas on the forgings in the process of hot precision forging on a hammer. The studies included: an analysis of the forging technology, advanced numerical simulations of the process and dynamic tests of the mutual shifting of the tools with the use of a high-speed measurement camera. The hot precision forging process was realized on a double operation hydraulic hammer with the maximal energy of 16 kJ, as a result of which, a so-called leaf is formed in the dies in two operations, which has 6 relatively small forgings (the mass of one is about 40 g), characterizing in a narrowed scope of dimension-shape tolerance (0.1–0.2 mm and 0.5–1°). The performed preliminary process analysis showed that, for this type of forgings made in a dynamic manner on a hammer, the key role is played by elastic deformations as well as the construction of the dies (application of guide locks) and the impression geometry. Additionally, during the forging process, in the case of pin-type elements (shape of a truncated cone with the convergence of 1°), their twisting was observed as well as small underfills caused by “closed volumes”, connected with the non-vaporized lubricant and the formation of air pockets. The mentioned problems relating to this process significantly affect the quality and precision of the forgings and cause defects. For this reason, based on the results of the conducted tests and analyses, a different approach to the design of dies was applied than in standard hammer forging technologies. It was introduced the necessary changes in the technology as well as modify the construction and geometry of the tools (in the lower die a negative slope was applied) in order to eliminate joggle and twisting of the forging elements, which disqualify such items.

Optimizing the local microstructure and mechanical properties of variable section particulate reinforced titanium matrix composites component based on numerical simulation and isothermal forming

To solve the precision forming problem of titanium matrix composites (TMCs) precision components with variable cross-sections, isothermal compression model of (TiB + La2O3)/IMI834 composite was established to investigate the deformation behaviors, determine forming strategy, predict and optimize the local microstructure. The subsequent isothermal precision forming experiment proved the precision forgings can be successfully fulfilled with good surface quality in one step using a cylindrical billet following the simulation strategy. Referring to simulation results, the local microstructure and performance were successfully optimized by controlling the deformation degree in different section regions to meet the service requirements. Fine-grained regions and reinforcement-rich regions were formed in the small cross-section (large deformation) regions due to the rotation and directional arrangement of the reinforcements and the dynamic recrystallization stimulated by the reinforcements, where the engineering strength and elongation were both improved from 1137 MPa and 2.55% to 1176.5 MPa and 4.0%, respectively, compared with the large cross-section (small deformation) regions. This research provided an important guidance for improving the fabrication efficiency and optimizing the local microstructure and performance of TMCs precision components by isothermal forming.

Study on Saponification Technology of Precision Forgings for Constant Speed Transmission Shaft of Car

The high-concentration pickling and the extreme emission and energy consumption of the precision saponification process before the cold finishing of the precision forgings of the constant speed drive shaft of the car. Oil mist emissions from the cold finishing process and relatively harsh working conditions. The purpose of this paper is to develop a new saponification process that saves energy and reduces emissions while ensuring product quality during production. Through a large number of tests, it shows that the saponification of precision forgings for the drive shaft can be completed by three steps including simple saponification liquid spraying, liquid extraction and hot air drying. Thus in this way, the saponification quality is the best, At the same time, it has greatly reduced emissions, while the instability of the saponification quality mainly relates to the control of saponification process.

Numerical and Experimental Studies of the Precision Forging of a Screw Propeller

The isothermal precision forging of a screw propeller was studied by means of numerical simulation and experimental forming. The deforming processes of the billet under two different forging patterns were discussed. The distributions of the flow line, the effective strain within the billet and the variation of the forging load during the forming process were analyzed. Results showed that there was a great difference of the effective strain existing between the blades and the wheel hub. The material flow and the distribution of deformation can be improved obviously by adding a core punch on the die. The distribution of deformation and forming load can be changed and controlled by adjusting the process parameters. The forging die was designed and manufactured according to the simulation results and perfect precision forgings have been acquired. Both of the simulation and the forming test showed that the precision forging of screw propellers could be formed with the isothermal precision forging satisfactorily.

Numerical Analysis on Precision Forging of 7A09 Aluminum Impeller

Numerical simulation and test forming of the isothermal precision forging of an impeller was carried out. The forming processes were simulated with DEFORM-3D to obtain the forming characteristics and metal flow pattern. It indicated that the impeller can be forged by the method of isothermal-forging, and the deforming process can be divided into 3 stages. The forming of blades was depended on the extrusion of materials. During the forming, uneven deformation was existed in the billet, especially in the field of the blade root. The forging load was increased rapidly during the later stage of the forming process, and the maximum forging load was about 2961kN. According to the simulations, the die structure and the billet dimension were determined, the forging die was designed and manufactured, and the precision forgings of the impeller were produced successfully. Both of the simulation and the test forming indicated that the impeller forging could be performed with the assembled structure die and the isothermal extruding forming style satisfactorily. The ideal parameters to produce the precision forgings of the impeller are: a forging temperature of 450°C and a punch speed of 1mm/s. Under these conditions, the forgings of the impeller can be produced with full blades, smooth outer surface and good flow line, which can meet the requirements of the precision forging of impellers.

Using Polyalkylene Glycol Quenchants to Effectively Control Distortion and Residual Stresses in Heat Treated Aluminum Alloys

Abstract Polyalkylene glycol quenchants (also commonly called “glycol” quenchants throughout the industry) were introduced into the aluminum heat treating industry in the mid 1960s and immediately became the most important tool for reducing quenching distortion in sheet metal alloys. Later, the feasibility and benefit of glycol quenching thicker products, such as castings and forgings (which were normally quenched in hot or boiling water), was proven. Specifications were changed to permit glycol quenching of forgings and castings. However, because of a lack of understanding of the technology, the original benefits achieved in sheet metal distortion control and optimum distortion and residual stress control of thicker products has diminished. Currently, there is a significant lack of understanding regarding glycol quenching and, as a result, the full benefit of this technology is not currently being utilized. Distortion of sheet metal products and precision forgings has increased, resulting in increased check and straightening costs and higher residual stresses being imparted to parts. The realization of the benefits of glycols being able to reduce residual stress and ultimately machining costs is waning due to the reluctance of many engineers to recognize and understand the benefits of expanding the limits of the technology to achieve results not heretofore achievable. It is the purpose of this paper to review the basic concepts regarding glycol quenching of high strength aluminum alloys and to present recommendations for optimum control of distortion and residual stresses using the products. Specific illustrations showing that the proper use of glycol quenchants can provide the producer significant savings by (1) reducing quenching distortion and (2) minimizing residual stresses (which significantly improve machining practices and reduce the generation of scrap) are provided.

Study of the Precision Forging of an Impeller by Numerical Simulation and Test Forming

In the present paper, the precision forging of an impeller was studied by means of numerical simulation and test forming. Based on the structure and dimension of the impeller, the combination structure was used in the forging die to obtain the extrusion deformation. The forming processes were simulated with DEFORM-3D for different billet dimensions and processing parameters. The parameters, which could ensure the forming quality of the impeller, were determined by the calculations and analysis. The die structure and the billet dimensions were determined according to the simulation results, and the forging die was designed and manufactured. The billet with semi-solid microstructure was produced by means of the direct heating-isothermal treatment. The forming was conduced in an YX-315F hydraulic press, and the precision forgings of the impeller were produced successfully. Both of the simulation and the forming test show that the impeller forging can be formed with the combination structure die and the extruding forming stale satisfactorily. The ideal parameters to produce the precision forgings of the impeller are: billet temperature at 625°C, die temperature at 450°C and punch speed at 20mm/s. Under these conditions, forgings of the impeller can be produced with plump blades, smooth outer surface, and good flow line. This can match the requirements of the precision forging of impellers.

Computer Simulation on Formation of Precision Forgings of Titanium Alloy and Superalloy

The deformation features are analyzed for titanium alloy and superalloy during isothermal/hot die forging process, and proper finite element models with appropriate parameter values are determined. On the platform of DEFORM software, the formation processes of vane-integrated disk and compressor disk, made of titanium alloy and superalloy respectively, are simulated and analyzed. Based on the simulation results, some important suggestions to the process design and parameter determination are brought forward, which have been taken into consideration or adoption in practice. As a result, the production yield is promoted, and a large amount of expenses of testing and die trial-manufacture are saved.

Study on isothermal precision forging technology for a cylindrical aluminium-alloy housing

High-precision forging is becoming increasingly popular in modern plastic working. The effects of forging force, die chilling, residual stress and lubricant are significant in a hot precision forge. Producing aluminium-alloy precision forgings of reasonable complexity is a difficult operation. Temperature control within narrow ranges, high-accuracy dies and suitable forming methods are necessary in order to develop desirable microstructures, properties and the near-net shape of forgings. Therefore, isothermal forging is a prime method from the precision forming viewpoint. This paper presents details of isothermal precision forging technology for a cylindrical aluminium-alloy housing.

Analysis of ejection in precision forging

A theoretical model for predicting loads for ejecting precision forgings from a die, has been developed. This has been used to determine the effects of forging load, friction and die wall/workpiece interface contact area on ejection load of cylinders forged at room and elevated temperatures. Experimental results obtained for cold and warm forgings, compare well with theoretical predictions. At higher temperatures (above 800°C), neglect of oxidation and post forging thermal contraction in the theory makes it unable to predict results with sensible accuracy.

Precision forging of a high strength superplastic zinc-aluminum alloy

Precision forgings can be produced in a high strength zinc aluminum alloy exhibiting superplasticity by means of an isothermal forging cycle which combines an approach at constant speed followed by a dwell at constant load. This study shows that integral threads, sharp corners, and very thin webs can be formed directly in the forging operation. A pressure compensated time parameter is developed which permits forging operations over a range of different conditions to be correlated. This parameter may be used to predict the result of actual precision forging processes from scale model tests.

Rapid Alloy Classification of Small Precision Forgings for the Aircraft Industry

In the manufacture of small precise-to-form forgings for the aero-space industry, components, many of identical shape, in a wide range of alloys are processed at the same time. Methods of alloy classification employed have developed from chemical spot checks up to automatic read-out spectrographs, which produce a high spectrum dispersion. This technique necessitates highly skilled operators and introduces a mental fatigue factor. This paper describes the development of a direct reading automatic read-out unit capable of operation by personnel having a minimum of training. A special counter-electrode and feed system was required. Due to the variation in surface finish and geometric shape of the forgings, the simple setting procedure envisaged was not practical and use of a trimming standard was required as an integral part of the procedure. The unit has been in production for over two years and has completed over 900 000 alloy classifications.

Development of alloy systems for powder forging

Precision forgings are now being produced from preforms pressed from steel powders. There are a greater number of factors influencing the choice of alloy composition than in traditional wrought technology. Since strength is frequently controlled by heat treatment, hardenability is of importance. The elements that are most useful in promoting hardenability at lowest cost are manganese and chromium. However, because of their affinity for oxygen they are not the most satisfactory elements for powder making. The author gives the reasoning behind the design of alloys for the powder-forging process. It is shown how mechanical strength and cost are considered to be controlling variables.

The Importance of Vacuum and Remelting Practices in a Modern Specialty Steel Plant. Part II: The Production of Different Specialty Steels

The various groups of specialty steels require different melting techniques, treatments, pouring methods, and remelting processes. Depending on their composition and application, quality and cost are significant factors governing the decision for a specific procedure. For example, the two-stage technique—UHP electric furnace or BOF-vacuum plant—is successful in the production of anti-friction bearing steel, in that it reduces the oxide content and produces a more consistent product. In the production of alloyed engineering steels, as used by the automotive industry, excellent results are obtained with this same two-step method. This method reduces melting times with gains in purity and closer control of alloying content and grain size. For special requirements such as aircraft engines, the steel is vacuum-melted and vacuum-remelted. Precision forgings require degassing treatments and with unusual specifications for purity and freedom from segregation vacuum-arc or electro-slag remelting. Special purity tool steels are initially melted in the arc furnace or oxygen converter and then treated under vacuum. Widespread use is made of the possible variations in the two-stage arrangement, “melting furnace-vacuum plant”, in the production of stainless steels. As opposed to the traditional methods of producing this type of steel, appropriate combinations result in significant cost and quality advantages. High purity stainless steels, particularly in the form of flat shapes, are commonly VAR- or ESR-remelted. However, the most pronounced effects in melting, vacuum treatment, and remelting are found in the field of high-temperature materials.

LUBRICANTS FOR U.S.A.F. FORGING PRESSES

INTERESTING lubrication applications are involved in the production of heavy precision forgings by means of two new 35,000‐ton and 50,000‐ton hydraulic presses recently installed at the Cleveland works of Aluminium Company of America, who are operating the plant on behalf of the U.S. Air Force. Such heavy precision forgings will make possible the construction of lighter and less expensive components for all types of modern military aircraft and their size will permit one‐piece construction of airframe parts, which formerly required several pieces.