Cold Deep Drawing Research Articles

Microstructure evolution and twinning behavior of AZ31 magnesium alloy sheets with bimodal texture during cold deep-drawing deformation

Cold deep drawing experiments were conducted on AZ31 magnesium (Mg) alloy sheets with bimodal texture, which were prepared by the newly developed equal channel angular rolling and continuous bending and subsequent annealing (ECAR-CB-A) process. The results showed that the sheet could be successfully deep-drawn at a limiting drawing ratio (LDR) of 1.6, and the forming performance was better than that of the as-rolled base-texture sheet at room temperature. The microstructure after deep-drawing deformation was investigated by X-ray diffraction (XRD), optical microstructure (OM), and electron backscatter diffraction (EBSD). A large number of {10−12} extension twins (ETs) are observed in the outer shoulder region. Due to the bimodal texture, the activated {10−12} ET variants and the basal slip within the matrix have a higher Schmid Factor (SF) value when the outer shoulder region is under radial tensile stress, this enables the shoulder of the drawn cup to maintain good deformability. In addition, some {10−11} contraction twins (CTs) and {10−11}-{10−12} double twins (DTs) can be observed in this region, which is activated by the local strain accommodation between the twins and the slip systems, and the multiaxial stress. Due to different stress conditions, the volume fractions of {10−12} ETs in the inner shoulder region are less than that in the outer region. The stress concentration caused by {10−11}-{10−12} DTs that occurred in the edge region is the reason for the fracture of the drawn cups at a drawing ratio(DR) of 1.7.

Influence of boriding on the tribological behavior of AISI D2 tool steel for dry deep drawing of stainless steel and aluminum

Deep drawing of stainless steel and aluminum is a widely adopted method for manufacturing various industrial goods. However, the wear damage produced to die tools is a recurring problem in these processes. While lubricants are often employed to lubricate and reduce die wear, dry deep drawing is the current best alternative for meeting green manufacturing demands. Hence, enhanced solid lubricants or surface treatments for dies are highly required. This study aims to evaluate and compare the tribological behavior of a heat-treated AISI D2 steel and a boriding AISI D2 tool steel against stainless steel (AISI 304) and aluminum alloy (AA 6061 T6) in the absence of lubricant. The boride coating was formed on the AISI D2 steel by the closed-pack boriding technique, resulting in a tooth-saw morphology with an overall thickness of 33.6 μm. X-ray diffraction analysis confirmed the presence of FeB, Fe2B, and Cr2B3 phases on the surface of the borided AISI D2 tool steel. Notably, the boriding treatment led to a significant increase in the surface hardness of the tool steel, reaching a value of 20.7 GPa. The coefficient of friction (CoF) behavior and wear were evaluated by pin-on-disk tests, simulating conditions similar to those found in cold deep drawing operations. The wear surfaces were analyzed by optical profilometry and scanning electron microscopy (SEM). The results suggest boriding as a suitable treatment to reduce wear damage on the surface of deep drawing dies used for stainless steel and aluminum forming processes in the absence of lubricant. Two-body abrasion and adhesion were identified as the main wear mechanisms in AISI D2 steel against stainless steel and aluminum, with a significant amount of oxidation observed when aluminum was tested. Additionally, a reduction of approximately 20 % in the CoF was observed when employing borided tool steel against stainless steel. However, there was an observed increase of around 75 % in the CoF when the borided tool steel was tested against aluminum.

A Finite Element Analysis of Cold Deep Drawing of Al Alloy Considering Friction Condition and Corner Design of Plunger

This study presents an innovative methodology that integrates experimental investigations with finite element simulations to ascertain the validity and reliability of Al 3104 sheet metals during cold deep drawing. Focusing on the nose plunger radius and coefficient of friction at a fixed speed and temperature (25 °C), five different scenarios are utilized to simulate the optimum parameters. Through a detailed strain history analysis from simulations, the initiation of bending in the corner is precisely identified, with a validation achieved through a strain analysis obtained via digital image correlation. The study delves into the influence of strain and strain rate on the microstructures and mechanical properties near the corner region. It highlights the superior efficacy of strain-based criteria in characterizing deformation behavior. Notably, the strain distributions during the onset of bending and severe bending align remarkably well with the established simulation data. In brief, this work introduces an integrated approach that harmoniously combines computational simulations with empirical observations, resulting in significant ramifications for precisely comprehending and forecasting the strain distribution in metal forming operations.

Laser Powder Bed Fusion of Inconel 718 Tools for Cold Deep Drawing Applications: Optimization of Printing and Post-Processing Parameters.

Inconel 718 (IN 718) powder is used for a laser powder bed fusion (LPBF) printer, but the mechanical properties of the as-built object are not suited to cold deep drawing applications. This study uses the Taguchi method to design experimental groups to determine the effect of various factors on the mechanical properties of as-built objects produced using an LPBF printer. The optimal printing parameters are defined using the result for the factor response to produce an as-built object with the greatest ultimate tensile strength (UTS), and this is used to produce a specimen for post-processing, including heat treatment (HT) and surface finishing. The HT parameter value that gives the maximum UTS is the optimal HT parameter. The optimal printing and HT parameter values are used to manufacture a die and a punch to verify the suitability of the manufactured tool for deep drawing applications. The experimental results show that the greatest UTS is 1091.33 MPa. The optimal printing parameters include a laser power of 190 W, a scanning speed of 600 mm/s, a hatch space of 0.105 mm and a layer thickness of 40 μm, which give a UTS of 1122.88 MPa. The UTS for the post-processed specimen increases to 1511.9 MPa. The optimal parameter values for HT are heating to 720 °C and maintaining this temperature for 8 h, decreasing the temperature to 620 °C and maintaining this temperature for 8 h, and cooling to room temperature in the furnace. Surface finishing increases the hardness to HRC 55. Tools, including a punch and a die, are manufactured using these optimized parameter values. The deep drawing experiment demonstrates that the manufactured tools that are produced using these values form a round cup of Aluminum alloy 6061. The parameter values that are defined can be used to manufacture IN 718 tools with a UTS of more than 1500 MPa and a hardness of more than 50 HRC, so these tools are suited to cold deep drawing specifications.

The Effect of Die Geometry on Cup Damages in Cold Deep Drawing of Rectangular Cups

Derin çekme, zımba kuvveti uygulanarak sac malzemenin kalıp boşluğuna akışıdır. Derin çekmede, düz ince tabakalar arasında sacı istenen şekle getirmek için zımba kullanılarak sacı merkez kısmından kalıp boşluğuna iterek kaplar üretilmektedir. Derin çekilmiş kaplarda kabın köşe yarıçaplarında boyun oluşumu veya çatlamaların oluşması nedeniyle daha yüksek çekme oranları elde edilememektedir. Bunun için derin çekme işleminin başarılı olmasında uygun işlem parametrelerinin doğru seçilmesi önemlidir. Bu makalede, dikdörtgen geometriye sahip kapların derin çekilmesinde matris üst yüzeyine ve pot çemberinin alt yüzeyine açılar verilerek matris geometrisinin, kap kesit incelmeleri ve hasarları üzerinde olan etkileri tespit edilmiştir. Bunun için matris üst yüzeyine/pot çemberi alt yüzeyine 0°, 3°, 6° ve 9°’lik açılar verilmiştir. Pot çemberi kuvveti sabit 1800 daN ve stampa hızı da sabit 4 mm/s olarak uygulanmıştır. Derin çekme işlemlerinde, matris/stampa arası boşluk 1.2 mm, stampa uç ve kenar radyüsleri ile matris ağız yarıçapları 6 mm alınmıştır. Çalışmada kalınlığı 1 mm olan St37 çeliği kullanılmıştır. Cidar kalınlıkları Mitutoyo LH-600E hassas lineer ölçüm cihazında 0.001 hassasiyetinde nokta temaslı olarak ölçülmüştür. Kap yükseklikleri artıkça kaplardaki cidar incelmelerinin arttığı, maksimum incelmenin kabın alt kısımlarındaki köşelerde meydana geldiği ve bu değerin 0,373 mm olduğu tespit edilmiştir. Plastik deformasyonun en çok etkilediği bölge kap alt bölgesidir. Bu bölgede deformasyon sertleşmesi nedeniyle maksimum basma ve çekme kuvvetleri oluşmakta ve dolayısıyla maksimum gerilme ve sertlik bu kısımda meydana gelmiştir. Maksimum sertlik kabın tabanının olduğu bölgede ve 61.4 HRC olarak ölçülmüştür. Minimum sertlik kap üst bölgesinde ölçülmüştür. Kabın üst ağız kısımlarına doğru sertliğin daha da düştüğü ve 43.8 HRC olduğu görülmüştür. Ortalama sertlik değeri ise 53.1 HRC olarak tespit edilmiştir. Sonuç olarak, dikdörtgen geometriye sahip kapların soğuk derin çekilmesinde, matris üst yüzeyine ve pot çemberinin alt yüzeyine açılar verilerek kalıp geometrisinin, kap cidar kalınlık değişimleri ve kap hasarları üzerinde önemli bir etkisinin olduğu tespit edilmiştir.

Warm Deep Drawing by Friction Heating Punch

Warm processing was performed by frictional heat generation between different materials installed inside the punch. Forming with press machine is a technology for processing materials by applying heat and force, and is an important technology for industrial machines such as automobiles and electronic devices. For light metals such as aluminum alloys and magnesium alloys, it may be difficult to form depending on the type of alloy in cold deep drawing. As a method of improving formability, warm working is performed in which the metal die heated and deep drawing is performed. However, warm working requires many control devices such as heating and cooling for the mold. Using a prototype punch with a built-in friction heat generation jig, friction heat was generated by combining several types of steel materials. The changes in the exothermic temperature were mainly investigated in the combination of different materials. The test materials were carbon steel, tool steel, and stainless steel. The heat generation temperature generated by friction was measured by a thermocouple installed inside the heat generation jig. The friction surface of the jig after frictional heat generation was observed by a microscope. In frictional heating, the temperature of the processed area reached more than 350 °C in a few minutes. The proposed method was able to heat the punch. After frictional heating, the load of deep drawing of pure aluminum sheet decreased. It was found that there is a possibility of improving workability by warm deep drawing.

Investigation on Friction Coefficient Considering Al-Si Coating Layer Fracture of Boron Sheets in Hot and Cold Deep Drawing

In this paper, hot and cold deep drawing processes are determined with direct deep drawing process and indirect deep drawing process. To predict the friction coefficient, the finite-element method, which can predict deformation behavior until the fracture of a blank sheet, was proposed using the forming limit diagram (FLD) curve. The effect of fracturing of the coating layer on the friction coefficient during the hot and cold deep drawing processes was investigated. The deformation behavior of the coating layer of the boron steel sheet that affects the friction coefficient in the hot and cold deep drawing processes was also proposed. A forming method that can control the surface condition of the formed product is further proposed by explaining the fracture of the coating due to the forming process.

Effect on Blank Holding Force on Blank Deformation at Direct and Indirect Hot Deep Drawings of Boron Steel Sheets

This study involves performing direct and indirect hot press forming on ultra-high-strength steel (UHSS) boron steel sheets to determine formability. The indirect hot press process is performed as a cold deep drawing process, while the direct hot press process is performed as a hot deep drawing process. The initial blank temperature and the blank holding force are set as parameters to evaluate the performance of the direct and indirect deep drawing processes. The values of punch load and forming depth curve were obtained in the experiment. In addition, the hardness and microstructure of the boron steel sheets are examined to evaluate the mechanical properties of the material. The forming depth, maximum punch load, thickness, and thinning rate according to blank holding force were examined. The result shows that a larger blank holding force has a more significant effect on the variation of the thickness and thinning rate of the samples during the drawing process. Furthermore, the thinning rate of the deep drawing part in with and without fracture boundary was respectively examined.

Effect of Plastic Deformation on Elastic and Plastic Recovery in CP-Titanium

The springback associated with cold deep drawing of sheet metals leads to undesired dimensional changes in the final products. This is often due to the heterogeneous plastic deformation in different areas of the intended geometry that creates various stress states throughout the part. The major objective of this study is to understand the interconnection between springback, level of plastic deformation, degradation of elastic modulus and strain recovery in a CP-Ti material. The mechanical properties of the sheet material and the dependency of mechanical properties on directionality are investigated by examining samples from three orientations of parallel to the rolling direction (RD), at 45° to RD and perpendicular to RD. The degradation of elastic modulus as a function of level of plastic deformation was explored for 0° and 45° samples by conducting multi-step uniaxial loading-unloading in tension.The experimental results showed that the mechanical properties vary for each direction, with the lowest elastic modulus along RD. A significant degradation was observed in elastic modulus (up to 50% reduction) with increased plastic deformation. This resulted in more strain relaxation compared to that associated with the initial elastic modulus. For stresses below 100MPa, a nonlinear (plastic) recovery was observed, resulting in additional relaxation in the total strain upon load removal in each step of the interrupted tests. This plastic recovery behaviour is observed to be dependent on sample orientation. It is concluded that accurate prediction of springback during sheet metal forming, requires a material model which takes into accounts the directional degradation of elastic modulus and the plastic recovery as a function of plastic deformation.

冷間深絞り加工による高耐食性チタンクラッド板の成形性

冷間深絞り加工による高耐食性チタンクラッド板の成形性

冷間多段深絞り加工による純チタン角筒容器の成形性

冷間多段深絞り加工による純チタン角筒容器の成形性

Multi-Stage Cold Deep Drawing of Pure Titanium Square Cup

This paper deals with the formability of pure titanium sheet in square cup deep drawing. Pure titanium has very excellent corrosion resistance. In the metal forming process, pure titanium has very good ductility in cold forming. The normal anisotropy of pure titanium is very high. Therefore, the property is suitable to the sheet metal forming, such as deep drawing process. However, the most important problem is that the occurrence of seizure becomes remarkable in severe forming operations. Many investigations on the effect of processing conditions on the seizure of titanium were carried out. In the present study, the formability of pure titanium sheet in square cup deep drawing was investigated. For the prevention, pure titanium sheets were treated by heat oxide coating. The fresh and clean titanium is not in direct contact with the die during the forming due to the existence of the oxide layer. The material was pure titanium sheets of the JIS grade 2. The initial thickness of the blank was 0.5 mm in thickness. In the deep drawing process, the sheets were employed and a flat sheet blank is formed into a square by a punch. Forming of sheet by multi-stage deep drawing was tried. Various cups were drawn by exchanging the punch and die. The die was taper without a blankholder in the subsequent stages. The effects of the intermediate annealing and tool shape on the occurrence of seizure in square cup deep drawing were also examined. The square cups were successfully drawn by heat oxide coating. The coating of titanium sheet has sufficient ability in preventing the seizure in multi-stage deep drawing operation. The results of the present study revealed that the pure titanium square cups were successfully formed by using heat oxide coating treatment.

Hot Spline Forming of Ultra-High Strength Steel Gear Drum Using Resistance Heating

A hot spline forming process of die-quenched gear drums using resistance heating of a side wall of a cup formed by cold deep drawing and ironing was developed. The side wall having uniform cross-sectional area is resistance-heated by passage of the current in the axial direction, the heated side wall of the drawn cup is ironed and is finally die-quenched. The gear drum was successfully formed and the hardness was between 400 and 500 HV. Not only the formability was improved but also the formed dram was hardly oxidised because of rapid resistance heating.

Research on Formability of AZ31B Magnesium Alloy at Room Temperature

Tensile tests and a cold deep drawing process were developed at room temperature to estimate the stamping formability of AZ31B magnesium alloy sheet. The results show that AZ31B magnesium alloy sheet has poor formability at room temperature with the total elongation of ~ 20%, the yield ratio is about 0.6 and the strain-hardening exponent is 0.18, while the plastic strain ratio is 1.58, and the earing ratio is-0.55.Thus, AZ31B magnesium alloy sheet can not suffer server plastic deformation. It was found that comparatively shallow magnesium alloy cups were satisfactorily formed at room temperature without heating when the punch fillet radius 6mm and the die fillet radius10mm with a 1mm thickness sheet with limit drawing ratio of 1.25.

Anisotropy in Cold Deep Drawing of CP-Ti Sheet

Anisotropy of CP-Ti sheet in cold deep drawing was investigated by means of experiments. The as-received blank showed remarkable anisotropy due to the existence of the spilt basal texture. Deformation intensified the anisotropy in the distributions of wall thickness and ears, and mechanical properties after drawing. The micro-mechanism causing anisotropy of CP-Ti was analyzed. Then, methods for the improvements of anisotropy were brought out as profile optimization of the initial blank and heat treatment on the finished part at 650 °C for 1 hour.

Microstructure and texture of commercially pure titanium in cold deep drawing

The development of microstructure and texture during cold deep drawing of commercially pure titanium (CP-Ti) was investigated. Three parts, stretching region, drawing region and flange region, were sequentially formed in the deep drawing process of the hemispheric surface part, with reference to deformation modes and strain regimes. Results show that the plastic strain is accommodated by dislocation slip and deformation twinning in the whole deep drawing process. The texture of the CP-Ti sheet and its drawn part consists of rolling texture component and recrystallization texture component. The intensity and type of the initial texture varied during the drawing process are related to the production of deformation twinning and dislocation slip. Twinning weakens the initial texture by randomizing the orientations of crystals, especially for the recrystallization texture. The recrystallization texture in the drawing region disappears due to the significant forming of twinning. Furthermore, over drawing would result in the predominance of dislocation slip and the texture is strengthened.

923 マグネシウム-リチウム系合金薄板の冷間深絞り加工性(GS-4 軽合金の評価)

923 マグネシウム-リチウム系合金薄板の冷間深絞り加工性(GS-4 軽合金の評価)

Spline forming of ultra-high strength gear drum using resistance heating of side wall of cup

A spline forming process of an ultra-high strength steel gear drum using resistance heating of a side wall of a cup formed by cold deep drawing and ironing was developed. The side wall having uniform cross-sectional area was heated by the electrification in the axial direction. The uniformity of the temperature was improved by inserting copper foils between the electrode and the side wall, and by decreasing the area of contact. Although the high strength steel cup was fractured by cold spline forming, the gear drum was successfully formed by the heating.

Formability of Pure Titanium Long-Cup by Multi-Stage Deep Drawing

The pure titanium long-cups were formed by preventing the seizing in cold multi-stage deep drawing processes. For the prevention, pure titanium sheets were treated by heating oxide coating. The coating is very effective in preventing the occurrence of seizure and galling. The fresh and clean titanium is not in direct contact with the die during the forming due to the existence of the oxide layer. In multi-stage deep drawing, pure titanium sheets of the JIS grade 2 was employed. Various cups were drawn by exchanging the punch and ringed die. The die was flat in the first stage, and was taped without a blankholder in the subsequent stages. The effects of the coating conditions on the occurrence of seizure in multi-stage deep drawing were examined. It was found that the coating titanium sheet has sufficient ability in preventing the seizure in multi-stage deep drawing processes. The pure titanium long-cups were successfully formed by a multi-stage deep drawing operation in cold.

On the Modeling of Dual Phase Steels: Microstructure-based Simulation from the Hot Rolled Sheet to the Deep Drawn Component

A major part of the industrial development in sheet metal forming is supported by numerical simulation. While individual simulation solutions for each application are available to study the producibility or serviceability of parts, a more unified approach that considers the results from the previous step along the production chain has not been presented so far. Within a joint research project that is founded by the German Federal Ministry of Education, a simulation strategy to model the process chain of dual phase steels from the hot rolled strip up to the behavior of components under crash conditions is developed. One important aim is to close the virtual process chain that ranges from steel design to crashworthiness simulation. The proposed concept will take into account micro-structural aspects of the material as well as macroscopic approaches, depending on the process step. This contribution presents the current status of the project considering the process steps cold rolling, annealing and deep drawing.