Investigation on Microstructure and Martensitic Transformation Mechanism for the Warm-Stamped Third-Generation Automotive Medium-Mn Steel

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Xiaodong Li ◽  
Ying Chang ◽  
Cunyu Wang ◽  
Shuo Han ◽  
Daxin Ren ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Strain Rate ◽  
Compressive Load ◽  
High Strength ◽  
Third Generation ◽  
Transformation Mechanism ◽  
Loading Method ◽  
Strain And Strain Rate ◽  
Medium Mn Steel ◽  
Mn Steel

With the development of the automotive industry, the application of the high-strength steel (HSS) becomes an effective way to improve the lightweight and safety. In this paper, the third-generation automotive medium-Mn steel (TAMM steel) is studied. The warm-stamped TAMM steel holds the complete and fine-grained martensitic microstructure without decarbonization layer, which contributes to high and well-balanced mechanical properties. Furthermore, the martensitic transformation mechanism of the TAMM steel is investigated by the dilatation tests. The results indicate that the effects of the loading method on the Ms temperature under different loads are different. The Ms temperature is hardly influenced under the tensile loads and low compressive load. However, it is slightly decreased under the high compressive load. Moreover, the effects of the strain and strain rate on the Ms temperature are insignificant and can be neglected. As a result, this research proves that the martensitic transformation of the TAMM steel is rarely influenced by the process parameters, such as stamping temperature, loading method, load, strain, and strain rate. The actual stamping process can be designed and controlled accurately referring to the continuous cooling transformation (CCT) curves to realize the required properties and improve the formability of the automotive part.

Introduction to a Third-Generation Automobile Steel and Its Optimal Warm-Stamping Process

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Ying Chang ◽  
Cunyu Wang ◽  
Kunmin Zhao ◽  
Han Dong ◽  
Jianwen Yan
Keyword(s):  
Tensile Strength ◽  
Third Generation ◽  
Range Analysis ◽  
Forming Process ◽  
Soaking Time ◽  
Stamping Process ◽  
Medium Mn Steel ◽  
Automobile Steel ◽  
Formed Part ◽  
Mn Steel

The medium-Mn steel is a promising third-generation automobile steel. Its chemical composition, microstructure, and thermal and mechanical properties are introduced and a warm-stamping process for the medium-Mn steel is proposed. The optimal process parameters are identified through the design of experiments (DOE) and range analysis. The evaluated experimental indexes include tensile strength, elongation, and hardness. The optimal forming process consists of an austenitization temperature of 840 °C, a soaking time of 4 min, and an initial stamping temperature of 500 °C. The proposed process was applied to the warm stamping of an automotive B-pillar. The microstructure of ultrafine, uniform, and complete martensite laths was obtained. The formed part exhibits approximately 1420 MPa tensile strength, over 11% elongation and 460 HV hardness. The optimal warm-stamping process has proved effective and applicable for forming medium-Mn steel parts. It will help promote the application of the third-generation automotive steels.

Dynamic Strength Estimates for a High Strength, Experimental Steel

2005 ◽  
Author(s):  
Karen L. Torres ◽  
Hollie A. Clements ◽  
Stanley E. Jones ◽  
Morris Dilmore ◽  
Bradley Martin
Keyword(s):  
Strain Rate ◽  
Dynamic Testing ◽  
Dynamic Strength ◽  
High Strength ◽  
High Mass ◽  
Performance Requirements ◽  
Cylinder Test ◽  
Strain And Strain Rate ◽  
Initial Shock ◽  
The Impact

For several years, the Air Force has been engaged in the development of high velocity air to surface missiles. The objective is to replace larger, high mass weapons with smaller, more versatile projectiles that can achieve the same goals. The reduction of mass requires that the impact velocity be increased to meet the performance requirements. This has presented researchers with several challenges. First, the steel must be such that it survives the initial shock at impact. Second, because the tunnel is long, the material must resist friction and wear, which could erode the projectile nose, thereby degrading performance. The purpose of this paper is to present the results of dynamic testing of an experimental, high-strength steel. Using a one-dimensional model for the Taylor cylinder test, the constitutive behavior of the steel as a function of strain and strain-rate can be assessed through a strain-rate of roughly 105/second. This behavior is consistent with that required for successful modeling of the response of a penetrator casing in the ultra-ordinance velocity range.

Dynamic Strength Estimates for a High-Strength Experimental Steel

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
K. L. Torres ◽  
H. A. Clements ◽  
S. E. Jones ◽  
M. Dilmore ◽  
B. Martin
Keyword(s):  
Strain Rate ◽  
Dynamic Testing ◽  
Dynamic Strength ◽  
High Strength ◽  
High Mass ◽  
Performance Requirements ◽  
Cylinder Test ◽  
Strain And Strain Rate ◽  
Initial Shock ◽  
The Impact

For several years, the Air Force has been engaged in the development of high velocity air to surface missiles to defeat hard targets, such as concrete, sand, and soil. The objective is to replace larger, high mass weapons with smaller, more versatile projectiles that can achieve the same goals. The reduction of mass requires that the impact velocity be increased to meet the performance requirements. This has presented researchers with several challenges. First, the steel must be such that it survives the initial shock at impact. Second, because the travel distance in the target is long, the material must resist friction and wear, which could erode the projectile nose, thereby degrading performance. The purpose of this paper is to present the results of dynamic testing of an experimental high-strength steel, also called Eglin steel. Using a one-dimensional model for the Taylor cylinder test, the constitutive behavior of the steel as a function of strain and strain rate can be assessed through a strain rate of roughly 105∕s. This behavior is consistent with that required for successful modeling of the response of a penetrator casing in the ultra-ordinance velocity range.

High strength-high ductility medium Mn steel obtained through CALPHAD based alloy design and thermomechanical processing

2021 ◽  
pp. 140756
Author(s):  
Achintya Kumar Patra ◽  
C.N. Athreya ◽  
Sumantra Mandal ◽  
K.C. Hari Kumar ◽  
V. Subramanya Sarma
Keyword(s):  
Thermomechanical Processing ◽  
High Strength ◽  
Alloy Design ◽  
High Ductility ◽  
Medium Mn Steel ◽  
Mn Steel

Effects of Different Cutting Processes on Characteristics of Cut Damage for the Third-Generation Automobile Medium-Mn Steel

2017 ◽  
Vol 89 (9) ◽  
pp. 1700375 ◽  
Author(s):  
Ying Chang ◽  
Shuo Han ◽  
Xiaodong Li ◽  
Cunyu Wang ◽  
Guojun Zheng ◽  
...  
Keyword(s):  
Third Generation ◽  
The Third ◽  
Medium Mn Steel ◽  
Cutting Processes ◽  
Mn Steel

scholarly journals Microstructure and Local Mechanical Properties of the Heat-Affected Zone of a Resistance Spot Welded Medium-Mn Steel

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3362
Author(s):  
Manfred Stadler ◽  
Ronald Schnitzer ◽  
Martin Gruber ◽  
Katharina Steineder ◽  
Christina Hofer
Keyword(s):  
Mechanical Properties ◽  
Heat Affected Zone ◽  
Great Influence ◽  
High Strength ◽  
Total Elongation ◽  
Resistance Spot ◽  
Heat Treated ◽  
Medium Mn Steel ◽  
Mn Steel ◽  
Spot Welded

The properties of the heat-affected zone (HAZ) are reported to have a great influence on the mechanical performance of resistance spot welded advanced high strength steels. Therefore, in the present work, the HAZ of a medium-Mn steel is characterized regarding its microstructure and its mechanical properties depending on the distance to the fusion zone (FZ). In order to obtain the local mechanical properties of the HAZ, samples were heat-treated in a joule-heating thermal simulator using different peak temperatures to physically simulate the microstructure of the HAZ. By comparing the microstructure and the hardness of these heat-treated samples and the HAZ, the local peak temperatures within the HAZ could be determined. Subsequently, tensile tests were conducted, and the austenite phase fraction was measured magnetically on the physically simulated HAZ samples in order to determine the local mechanical properties of the HAZ. As verified by energy-dispersive X-ray spectroscopy, peak temperatures above 1200 °C led to a uniform distribution of manganese, resulting in a predominantly martensitic microstructure with high strength and low total elongation after quenching. Below 1100 °C, the diffusion of manganese is restricted, and considerable fractions of austenite remain stable. The austenite fraction increases almost linearly with decreasing peak temperature, which leads to an increase of the total elongation and to a slight decrease in the strength, depending on the distance to the FZ. Temperatures below 700 °C exhibit hardly any effect on the initial microstructure and mechanical properties.

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