High Strength Microscrew with Ultrafine Grained Structure

2014 ◽  
Vol 783-786 ◽  
pp. 2695-2700
Author(s):  
Shiro Torizuka ◽  
Eijiro Muramatsu
Keyword(s):  
Uniform Elongation ◽  
Steel Wire ◽  
High Strength ◽  
Tensile Tests ◽  
Low Carbon ◽  
Ultrafine Grained Structure ◽  
Bainitic Steels ◽  
Ultrafine Grained ◽  
Reduction In Area ◽  
Ultrafine Grained Steel

While uniform elongation is a measure of ductility of the material, reduction in area in tensile tests is also an important measure of ductility. It was found that the reduction in area - tensile strength balance is far better than the conventional ferrite+pearlite steels and even superior to martensitic and bainitic steels. Formability of ultrafine-grained steel is examined by applying to form a M1.7 micro screw using these ultrafine-grained steels. Screws are formed through the process of cold heading and rolling. Relationship between cold heading, rolling, uniform elongation and reduction in area are investigated to clarify the formability of ultrafine-grained steels. Low-carbon ultrafine-grained steel has excellent cold headability and favorable rolling properties, i.e., excellent formability. Reduction in area is a measure to determine formability on cold heading. Ultrafine grained steel wire with length of several hundred meter were developed with the technology of warm continuous multi-directional rolling. This wire also have a good formability which can form microscrews. High strength microscrew with ultrafine grained structure was obtained.

Ultrafine Grained Steel Wire and its Formability

2012 ◽  
Vol 710 ◽  
pp. 19-26 ◽  
Author(s):  
Shiro Torizuka ◽  
Eijiro Muramastu ◽  
S.V.S. Narayana Murty
Keyword(s):  
Uniform Elongation ◽  
Steel Wire ◽  
Tensile Tests ◽  
Low Carbon ◽  
High Carbon ◽  
Ultrafine Grained ◽  
Ultralow Carbon ◽  
Reduction In Area ◽  
Better Than ◽  
Ultrafine Grained Steel

While uniform elongation is a measure of ductility of the material, reduction in area in tensile tests is also an important measure of ductility. Ultrafine-grained steels with different carbon contents from ultralow carbon to high carbon were produced through warm caliber rolling. It was found that the reduction in area- tensile strength balance is far better than the conventional ferrite+pearlite steels and even superior to martensite steels for all materials. Formability of ultrafine-grained steel is examined by applying to form a M 1.7 micro screw using these ultrafine-grained steels. Screws are formed through the process of cold heading and rolling. Relationship between cold heading, rolling, uniform elongation and reduction in area are investigated to clarify the formability of ultrafine-grained steels. Low-carbon ultrafine-grained steel has excellent cold headability and favorable rolling properties, i.e., excellent formability. Reduction in area is a measure to determine formability on cold heading. Ultrafine grained steel wire with length of several hundred meter were developed with the technology of warm continuous multi-directional rolling. This wire also have a good formability which can form microscrews.

Formability of Ultrafine Grained Steel

2010 ◽  
Vol 638-642 ◽  
pp. 3543-3548 ◽  
Author(s):  
S. Torizuka ◽  
Eijiro Muramatsu
Keyword(s):  
Uniform Elongation ◽  
Tensile Tests ◽  
Ultrafine Grain ◽  
Strain Behavior ◽  
Bainitic Steels ◽  
Ultrafine Grained ◽  
Inherent Feature ◽  
Ultralow Carbon ◽  
Reduction In Area ◽  
Ultrafine Grained Steel

Ultrafine grain refinement to 1 m deteriorates the uniform elongation in the tensile tests of steels. Such loss of ductility has been argued to be an inherent feature of the ultrafine-grained steels. While uniform elongation is a measure of ductility of the material, reduction in area in tensile tests is also an important measure of ductility. Ultrafine grained steels with different carbon contents from ultralow carbon to high carbon were produced through warm caliber rolling and evaluated for their stress-strain behavior along with the reduction in area. It was found that the reduction in area- tensile strength balance is far better than the conventional ferrite+pearlite steels and even superior to bainitic steels for all materials tested in the present study. Formability of ultrafine grained steel is examined by applying to make a micro screw. Good formability was verified by this process.

scholarly journals Application of Artificial Neural Network to the Prediction of Tensile Properties in High-Strength Low-Carbon Bainitic Steels

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1314
Author(s):  
Sang-In Lee ◽  
Seung-Hyeok Shin ◽  
Byoung-Chul Hwang
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Yield Strength ◽  
Tensile Properties ◽  
Uniform Elongation ◽  
High Strength ◽  
Low Carbon ◽  
Ann Model ◽  
Bainitic Steels ◽  
Artificial Neural

An artificial neural network (ANN) model was designed to predict the tensile properties in high-strength, low-carbon bainitic steels with a focus on the fraction of constituents such as PF (polygonal ferrite), AF (acicular ferrite), GB (granular bainite), and BF (bainitic ferrite). The input parameters of the model were the fraction of constituents, while the output parameters of the model were composed of the yield strength, yield-to-tensile ratio, and uniform elongation. The ANN model to predict the tensile properties exhibited a higher accuracy than the multi linear regression (MLR) model. According to the average index of the relative importance for the input parameters, the yield strength, yield-to-tensile ratio, and uniform elongation could be effectively improved by increasing the fraction of AF, bainitic microstructures (AF, GB, and BF), and PF, respectively, in terms of the work hardening and dislocation slip behavior depending on their microstructural characteristics such as grain size and dislocation density. The ANN model is expected to provide a clearer understanding of the complex relationships between constituent fraction and tensile properties in high-strength, low-carbon bainitic steels.

Development of Low Carbon Microalloyed Bainitic Steels for Structural Plate Applications

2005 ◽  
Vol 500-501 ◽  
pp. 573-580 ◽  
Author(s):  
D. Ormston ◽  
Volker Schwinn ◽  
Klaus Hulka
Keyword(s):  
High Strength ◽  
Carbon Steels ◽  
Chemical Compositions ◽  
Low Carbon ◽  
Controlled Processes ◽  
Bainitic Steels ◽  
Steel Grades ◽  
Carbon Microalloyed ◽  
Hot Rolled ◽  
Plate Steels

Steels with bainitic microstructures show the capacity to fulfil the requirements of high strength and low temperature toughness necessary for plate steels in specialised industrial constructions. The introduction of steels with higher strength allows for weight reductions of steel constructions. This paper investigates the development of hot rolled structural plate steels through laboratory hot rolling simulations of thermo-mechanically controlled processes (TMCP). Specific alloying and microalloying along with an optimised TMCP process has allowed high tensile properties to be achieved in combination with high levels of toughness. Tensile strengths of up to 900 MPa have been achieved with Charpy V-notch toughness greater than 200J at –40°C. Elements such as molybdenum, niobium and boron have been added to low carbon steels to promote the formation of fully bainitic microstructures with much lightened chemical compositions. The presented concepts allow the production of steel grades above S500 up to S690.

scholarly journals Potential of High Compressive Ductility of Ultrafine Grained Copper Fabricated by Severe Plastic Deformation

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1503
Author(s):  
Mayu Asano ◽  
Motohiro Yuasa ◽  
Hiroyuki Miyamoto ◽  
Tatsuya Tanaka ◽  
Can Erdogan ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Void Formation ◽  
Rate Sensitivity ◽  
High Strength ◽  
Local Strain ◽  
Tensile Tests ◽  
Dislocation Slip ◽  
Shear Mode ◽  
Ultrafine Grained

Severe plastic deformation (SPD) can fabricate high-strength materials by forming an ultrafine grained (UFG) microstructure. Low elongation to failure of UFG materials in tensile tests, which has often been regarded as a measure of ductility of materials, has been attributed to low strain hardening of UFG structures where dislocation slip and its accumulation is very limited. In the present work, it is shown that the compressive extensibility of UFG materials can be comparable or potentially superior to that of annealed materials by using a parallel round-bar compression (PRBC) test which was designed for imposing an appropriate stress state preferable for high ductility using the shear mode. The high compressive extensibility of UFG materials can be a result of high accommodation of local strain incompatibility at non-equilibrium grain boundaries and a grain boundary-mediated deformation mechanism, which result in high damage tolerance against void formation and growth. Low strain rate sensitivity indicated that the superplastic viscous nature of deformation is not involved in the high compressive ductility of UFG materials using SPD.

Ultrafine-Grained Steel Produced by Warm Rolling and Annealing of Lath Martensite

2010 ◽  
Vol 667-669 ◽  
pp. 863-866
Author(s):  
Xin Zhao ◽  
Xiao Ling Yang
Keyword(s):  
Lath Martensite ◽  
Tensile Tests ◽  
Total Elongation ◽  
Optical Microscope ◽  
Warm Rolling ◽  
Steel Plates ◽  
Transmission Electron ◽  
Hardness Tests ◽  
Ultrafine Grained ◽  
Ultrafine Grained Steel

Steel plates with lath martensite microstructure were rolled up to 68% reduction at 673 K and then annealed at 473-973 K. The microstructure evolution was studied by using an optical microscope and a transmission electron microscopy. And the properties were investigated by using tensile tests and hardness tests. Results show that ultrafine grains + nano-carbides are obtained in the steel plates. The specimen annealed at 823 K has a good combination of strength and ductility. The tensile strength and total elongation are 1028 MPa and 7.2%, respectively. And the hardness is 338 Hv.

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