Cold Stamping Research Articles

Parametric investigation of the effects of variables controlling thermal characteristics during continuous and high-speed cold stamping processes with active cooling structures

Knowledge of the thermal phenomena that occur during stamping is important for improving the design and performance of stamping die thermal structures. A new mathematical full-scale model for energy and carbon flows is established based on operational data from a cold stamping production line in China. Moreover, numerical simulations of the thermal-fluid–solid coupling field for a cooling medium in an asymmetrically heated rectangular channel with high heat flux and strong wall superheating are carried out with a suitable CFD solver. The results are discussed in detail and compared with theoretical calculations, and the deviation of the surface heat transfer coefficient is ± 11.9 %. Emphasis is placed on parametric effects of variables controlling thermal characteristics on cold stamping with an active cooling structure. The effects of heat flux, and ambient temperature on temperature rise, pressure drops, and heat transfer coefficients are limited less than 7 °C, 167 Pa and 45.11 % under specific operating conditions, respectively. While the heat transfer coefficient and pressure drops are increased hundreds of times with inlet velocity. The fluid cooling performance, threshold value, and approaches for heat transfer enhancement are obtained. Finally, the CO2 emissions rates is assessed as approximately 1.8 g per piece associated with stamping operations, as well as major contributors, CO2 reduction potential, and economic impacts. Negative energy consumption can be achieved with active cooling. These results can help to improve production quality in the future application and provide theoretical support for determining the causes of metal sheet tensile cracking accidents.

Limit State of Bake Hardened Stamped Interstitial-free Steel Automotive Parts Caused by Local Thickness Reduction

Current trends in the complex shapes of modern automobiles lead to the need for extremely formable materials for deep drawing applications. In general Interstitial–Free (IF) steels present the solution for this purpose. In addition, the cold stamping process is influenced by a variety of input factors that must be correctly adjusted. An imperfection in one of the inputs may cause stamping defects even with deep drawing materials. Limit states may then appear in the form of cracks or unacceptable thinning in the critically stressed areas of the stamped parts. For this reason, a general focus is placed on the use of non-destructive methods and inspection of stamped parts after stamping for potential subsequent modification of the stamping process. The presented work deals with the material analyses of stamped parts made of Bake-Hardened Interstitial-Free steel, including the local thickness reduction of the material, leading to the occurrence of crack propagation. The focus of the work was placed on the critical influencing factors resulting from the limit states presented. The evaluation of the material flow and the local plastic response was carried out using a cylindrical indentation method. In addition, the SEM analyses showed the importance of the deformation capacity of the surface coating which proved to be one of the decisive parameters for the occurrence of limit states.

Advancing Die Design and Optimization through the Combination Approach: A Focus on Spring-back Compensation

This study explores the geometrical deviations that occur in cold stamping, which are caused by the spring-back effects in elastic metals after forming. The primary aim is to introduce and assess the Combination Approach. This approach seamlessly integrates the Displacement Adjustment and Spring Forward methods for die compensation. This multi-stage process meticulously corrects dimensional errors and effectively reduces spring back through iterative processes. Using the NUMISHEET model, numerical simulations have shown a significant reduction in spring back errors, with up to a 55% reduction achieved with optimized die surfaces after five iterations. The proposed Combination Approach improves the accuracy of die design and contributes significantly to the stamping industry by incorporating established techniques within finite element software. This research broadens the scope of die compensation strategies, creating new opportunities for achieving precise die design in stamping.

Study of the Industrial Application of Diamond-Like Carbon Coatings Deposited on Advanced Tool Steels

The utilization of diamond-like carbon (DLC) coatings has emerged as a promising strategy to enhance the performance, durability, and functionality of industrial tools and components. Recognized for their exceptional attributes such as hardness, wear resistance, low friction, and biocompatibility, DLC coatings have achieved widespread acclaim for their potential to improve the capabilities of tool steels for different applications. This present study shows a comprehensive investigation into the application of DLC coatings on a diverse range of tool steel substrates, encompassing 1.2379, 1.2358, Caldie, K340, HWS, and Vanadis 4. The main aim is to show the effects of DLC coatings on these substrates and to provide an in-depth analysis of their properties during forming processes. Furthermore, this study explores the practical utilization of DLC-coated tool steel components, with a particular focus on their role in cold forming dies. Additionally, the study reviews the application of duplex treatments involving plasma nitriding to enhance DLC coating performance. To sum up, this study pursues a threefold objective: to investigate DLC coatings’ performance on diverse tool steel substrates; to assess the potential for improvement through nitriding; and to evaluate the behavior of DLC coatings in the cold stamping of S235 steel, which is of great technological and industrial interest to the cold forging sector.

АНАЛИЗ ДЕФОРМАЦИОННО-СТРУКТУРНЫХ ХАРАКТЕРИСТИК МОДИФИЦИРОВАННОЙ СИСТЕМЫ ИНСТРУМЕНТА ХОЛОДНОЙ ШТАМПОВКИ «ПОДЛОЖКА-ПОКРЫТИЕ»

The analysis of the level of residual stresses of the third kind in the "substrate-coating" system of a cold stamping tool is carried out, depending on the nature of the structural and deformation characteristics of the preliminary cold deformation of 20X13 steel samples with a wear-resistant coating. An assessment of the nature of the intensity of changes in the values of residual stresses both in the metal of the modified samples and on the coating, depending on the PPD, was carried out.

The influence of rolling at subcritical temperatures on the low-carbon steel structure and properties formation

Problem. In practice, the rolling of a low-carbon steel sheet due to significant heat losses ends in the austenite – ferrite two-phase structure region, which leads to the metal heterogeneous structure formation, that decreases the sheet steel properties of the and its ability to be drawn.
 Adverse temperature conditions characteristic of traditional hot rolling technology can be prevented by metal processing in the single-phase ferrite structure region below the critical point Ar1. Rolling of a thin sheet in the subcritical temperature range will ensure obtaining a uniform metal structure, which determines the level of its mechanical properties, as well as the quality of stamped parts
 Goal. The purpose of the work is study the rolling modes influence at subcritical temperatures on the low-carbon steel structure and properties formation.Methodology. The microstructure of 08ps steel samples was studied using a metallographic and electron microscope JSM-840 with a "Link-860/|500" microanalysis system, the 08ps steel samples cross-section fine structure was studied using an electron microscope JEM - 200Сx. The metal mechanical properties complex was determined by standard tensile test methods.Results. The 08ps steel structure and properties after rolling at subcritical temperatures were studied. The comparative analysis of the fine structure of the initial blank and deformed samples of low-carbon steel was carried out. It was established that changes are observed in the structure of the deformed samples and the initial blank, which indicate the polygonization and recrystallization processes implementation and do not provide the of metal mechanical properties level provided for by DSTU 2834-94.Originality. Тhe thin structure of a 08ps steel sheet deformed in the subcritical temperature range with air cooling was studied. The development differs in the temperatures of the beginning and end of rolling, as well as the cooling rate in the post-deformation period. It allows to expand theoretical ideas about the patterns of 08ps deformed steel structure formation and to use them in practice. Practical value. The results of the work can be applied in determining rational processing modes, which involve rolling at subcritical temperatures, to increase the complex metal properties and obtain high-quality parts by cold stamping.

Numerical modeling and topological analysis of entangled single-wire metal rubber

Metal rubber materials, formed by entangling single metal wires and also known as ESW-MR, have attracted widespread attention due to their unique non-linear load curves and excellent environmental adaptability. The mechanical behavior of these materials, which are created through the weaving or winding of pure metal wires, is influenced by the structural characteristics of semi-flexible fiber cross-linked fibers. This study delves deeply into the microstructure of ESW-MR, with the aim of establishing a numerical model that can accurately simulate and characterize its structure. A method based on arbitrarily defined baselines parametric equations in the global space was adopted, leading to the creation of a parametric model for a continuously wound wire with multiple spiral mechanisms. Finite element simulations based on explicit dynamics were conducted using LS-DYNA and could successfully simulate the cold stamping forming process of ESW-MR blanks. The model was validated through stamping and quasi-static tests, as well as computed tomography (CT) scan tests. The results demonstrate the model accuracy in describing the macroscopic and microscopic characteristics of the material, showing excellent agreement with the actual material. Furthermore, the study successfully extracted the micro-topological features of the material, providing additional quantitative information on the topological characteristics of ESW-MR. This work offers a valuable tool for the study and application of ESW-MR and presents a novel perspective for the numerical simulation of a wide range of entangled materials. It paves the way for gaining a deeper understanding of the microstructure and mechanical behavior of such materials.

Assessing the Feasibility of Cold Forming of Automotive Parts from Quenched and Partitioned Martensitic Stainless Steels

Sheet metal forming is among the most widely employed processes in manufacturing. Its economic feasibility relies on many factors, including the mechanical properties of the processed materials, energy efficiency of the metal‐forming processes, and quality of the manufactured parts. This work focuses on developing a computational approach to assess the mechanical behavior of quenched and partitioned (QP) martensitic stainless steels (MSSs) undergoing cold forming, aiming at the serial production of automotive parts. The Johnson–Cook (J–C) constitutive model and forming limit diagram (FLD) are derived and validated for each alloy using the experimental data from tensile and Nakajima tests. From the simulated FLD, a theoretical forming limit stress diagram (FLSD) is calculated. The latter is used as a fracture criterion for the cold‐forming process. Cold stamping of two automotive parts, B‐pillar and tunnel, is modeled using the J–C constitutive model and the FLSD. It is demonstrated that the tunnel can be successfully cold‐formed from all three studied steels. In contrast, extensive cracking is expected during the cold forming of the B‐pillar from all materials. It is envisaged that these computational models can be employed for the assessment of any comparable part manufacturing procedure from the QP MSSs.

PLAHS: A Partial Labelling Autonomous Hyper-heuristic System for Industry 4.0 with application on classification of cold stamping process

In real-life industry it is difficult to have fully-labelled datasets due to lack of time, resources or knowledge. In this sense, this paper proposes the design and development of a Partial Labelling Autonomous Hyper-heuristic System PLAHS, a solution that autonomously labels partially labelled databases and evaluates the yielded labelling solution by means of a novel Trustworthiness Metric (TM). The proposal combines a hyper-heuristic inspired approach with a Semi Supervised Learning Clustering (SSLC) methodology that optimizes the parameters of different clustering algorithms, based on a novel semi-supervised metric named Partially Supervised Optimization Metric (PSOM). The proposal has been tested with promising and excellent results on both a real use case for labelling work orders in a cold stamping press, and 13 databases from the UCI (multivariate data) and UCR (time series data) repositories.

Development of rapid die cooling technology using the Groove Pressing method in hot stamping process

The demand for hot stamping parts in the automobile industry is increasing due to the growth of eco-friendly vehicles with improved crash safety performance and lighter weight. However, the use of ultra-high-strength steel in cold stamping is challenging due to its high yield strength and low elongation. Hot stamping is a widely used process to overcome this challenge, but the long die quenching time reduces its productivity. In order to address this issue, a Groove Pressing method was applied to the sidewall of the die to improve cooling performance without requiring additional devices within the die. The study investigated the required contact pressure between the sheet and the die for the implementation of the groove shape on the sidewall. Computational analysis was performed to design optimal groove shape for the sidewall, and the results showed that Case 3 was the most suitable in terms of cooling performance and contact pressure. The groove shape was incorporated into the die making, and experiments were conducted on aluminized coated 22MnB5 1.2 mm sheet. The results showed that the implementation of the groove shape on the sidewall improved cooling performance, dimensional quality, and mechanical properties without affecting the corrosion resistance of the component. The study demonstrates the potential of the Groove Pressing method as a practical solution for improving the productivity of the hot stamping process in the automobile industry.

Wear characteristics of the tool in the cold stamping process of ultra high strength steel sheets by establishing a novel wear test method based on the progressive die

Demands for lightweighting and crashworthiness of the vehicle body have increased. For this purpose, advanced high strength steel to the automobile body was regarded as a solution with respect to manufacturing cost and impact energy absorption. However, increasing the strength of the automotive steel sheet lead to a diversity of problems caused by the tool wear due to higher forming load than that of commonly used steel sheets. Hence, systematic wear experiment and evaluation methods are required to quantitatively and qualitatively evaluate the tool wear amount in the sheet metal forming process. In this study, a methodology is proposed to quantitatively evaluate the wear of sheet metal forming tool based on the experimental results. In order to carry out a systematic wear test and save the time and cost, the progressive die set was designed to be suitable for wear test. The designed testing machine can simultaneously test four types of punches made under various tooling conditions such as materials, shapes, and coatings. Through the measurement of the wear depth, roughness, and surface imaging of the punch and product roughness, which represent the wear characteristics, quantitative evaluation methods for tool wear in the sheet metal forming process are established. By referring to the wear test results, it is confirmed that it is appropriate to analyze the reasonable tool wear characteristics by using the proposed methodology for quantifying the tool wear in the sheet metal forming process.

Experimental characterization of forming behavior of 3rd GEN AHSS

Third generation of Advanced High Strength Steels (3rd GEN AHSS) for cold stamping combine superior formability and ductility at higher strengths. Their combination with the Laser Welded Blanks (LWB) technology is one answer to improve safety and weight reduction of vehicules for automakers. In this study, a Nakazima test is used to evaluate the forming behavior of LWB based 3rd GEN AHSS and to estimate their Forming Limit. Tests equipped with a Digital Image Correlation (DIC) system are carried out for several materials combinations in order to understand the influence of the weld on LWB formability. The experimental results are used to determine the critical area during this forming test and a dedicated FLC for each material combination. The location of the onset of failure is investigated, from optical observations, DIC data as well as modeling. It appears that different failure locations are obtained depending on both AHSS combination and strain paths. In order to improve the accuracy of the determination of the onset of the failure, a method is proposed to evaluate the failure risk in base metal and in the vicinity of the weld. The improvement of failure prediction will be very helpful to analyze part formability and provide design recommendations.

Control System for Automated Technological Process of Hot Stamping-A Case Study.

Hot forming process has been used more and more frequently in the production of body structures of modern ultralight passenger cars for several years. This, unlike the commonly used cold stamping, is a complicated process, combining heat treatment and plastic-forming methods. For this reason, permanent control at each stage is required. This includes, among others, measurement of the blank thickness, monitoring its heating process in the suitable atmosphere in the furnace, control of the forming process itself, measurement of shape-dimensional accuracy as well as mechanical parameters of the finished drawpiece. This paper discusses the method of controlling the values of production parameters during the hot stamping process of a selected drawpiece. For this purpose, digital twins of the production line and the stamping process, made in accordance with the assumptions of Industry 4.0, have been used. Individual components of the production line with sensors for monitoring process parameters have been shown. The system's response to emerging threats has also been described. The correctness of the adopted values is confirmed via tests of mechanical properties and the assessment of the shape-dimensional accuracy of a drawpiece test series.

Effect of complicated deformation behaviors during cold stamping on springback prediction of DP980 steel

Effect of complicated deformation behaviors during cold stamping on springback prediction of DP980 steel

Sustainable Lifecycle of Perforated Metal Materials.

In an era of rapidly growing consumer demand and the subsequent development of production, light materials and structures with a wide range of applications are becoming increasingly important in the field of construction and mechanical engineering, including aerospace engineering. At the same time, one of the trends is the use of perforated metal materials (PMMs). They are used as finishing, decorative and structural building materials. The main feature of PMMs is the presence of through holes of a given shape and size, which makes it possible to have low specific gravity; however, their tensile strength and rigidity can vary widely depending on the source material. In addition, PMMs have several properties that cannot be achieved with solid materials; for example, they can provide considerable noise reduction and partial light absorption, significantly reducing the weight of structures. They are also used for damping dynamic forces, filtering liquids and gases and shielding electromagnetic fields. For the perforation of strips and sheets, cold stamping methods are usually used, carried out on stamping presses, particularly using wide-tape production lines. Other methods of manufacturing PMMs are rapidly developing, for example, using liquid and laser cutting. An urgent but relatively new and little-studied problem is the recycling and further efficient use of PMMs, primarily such materials as stainless and high-strength steels, titanium, and aluminum alloys. The life cycle of PMMs can be prolonged because they can be repurposed for various applications such as constructing new buildings, designing elements, and producing additional products, making them more environmentally friendly. This work aimed to overview sustainable ways of PMM recycling, use or reuse, proposing different ecological methods and applications considering the types and properties of PMM technological waste. Moreover, the review is accompanied by graphical illustrations of real examples. PMM waste recycling methods that can prolong their lifecycle include construction technologies, powder metallurgy, permeable structures, etc. Several new technologies have been proposed and described for the sustainable application of products and structures based on perforated steel strips and profiles obtained from waste products during stamping. With more developers aiming for sustainability and buildings achieving higher levels of environmental performance, PMM provides significant environmental and aesthetic advantages.

Parametric optimization and wear analysis of AISI D2 steel components

AISI D2 steel is widely used for forming die or cold stamping, chipper knives, shear blade, trimming cutter threading dies, punches and stamping tools etc. Hence, the current investigation aim is to determine the effects of sliding parameters on the wear performance of AISI D2 steel. The experiments were conducted on AISI D2 steel pin and disk of mild steel using the pin-on-disk apparatus. After that, relationships for forecasting weight loss of pins due to rubbing action have been developed using the design of experiment (DOE), which is based on response surface methodology (RSM) and has three independent parameters (slide duration, normal load, and sliding speed). ANOVA was used to perform the model adequacy tests, and the results of various parameters were computed and displayed in 3D surface graphs and contour plots. To reduce the weight loss, numerical optimization has been done while keeping all of the input parameters within range (wear volume). The manufacturing sector that uses AISI D2 steel for deforming dies would benefit from the study's findings.

Investigation of forming defects in 5A06 aluminum alloy cold stamping of thin-walled shell with corner

Investigation of forming defects in 5A06 aluminum alloy cold stamping of thin-walled shell with corner

Ways to increase the thermal power of the convector

The necessity of improving the production of heating devices in order to ensure their nominal thermal power is substantiated. The features of the manufacture of convectors "Universal" by the burnishing method are considered. The damages of the edges of the plates that occur during the expansion of the pipe during burnishing are investigated. The most promising direction for improving the quality of convector production has been identified - cold stamping of plates. The analysis of the shortcomings of plate stamping was carried out, the main reasons for the decrease in the thermal power of convectors were identified, and measures were developed to eliminate them. To increase the objectivity of the results of the study, tests were carried out with two different casings of convectors on a test bench. The optimal degree of plate tension has been determined and confirmed experimentally.

Research on mechanical properties of metal entangled structure‐silicone rubber composite vibration damping materials

AbstractMetal entangled structure is a porous metal damping material wound by spiral springs and formed by cold stamping. Its interior consists of interlocking and interlocking spiral springs. To further make the metal entangled structure have the characteristics of high stiffness and high damping at the same time, a high‐performance metal entangled structure‐silicone rubber composite damping material was designed. The viscoelastic properties, mechanical stability, deformation behavior, and damage mechanism of metal entangled structure‐silicone rubber composite were investigated by relaxation test, cyclic loading test, different loading rate test, and damage test, respectively. The effects of different preparation process parameters and loading conditions on the static mechanical properties of metal entangled structure‐silicone rubber composite were investigated. The experimental results show that metal entangled structure‐silicone rubber composite has good mechanical stability, insignificant viscoelasticity, and also variable damping and variable stiffness properties, and the load carrying capacity is substantially increased while maintaining good damping properties.

DEVELOPMENT OF TECHNOLOGY FOR THERMAL CYCLING OF PARTS MADE OF HIGH-ALLOY STEELS

This paper presents an analysis of the technical requirements for cold stamping, wear of their working zones, factors affecting wear and ways to increase wear resistance.