Competition between grain boundary segregation and Cottrell atmosphere formation during static strain aging in ultra low carbon bake hardening steels

Soenen, B.; De, A. K.; Vandeputte, S.; Cooman, Bruno C. De

doi:10.1016/j.actamat.2004.03.046

Cited by 79 publications

(37 citation statements)

References 17 publications

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“…The strain ageing (ΔY 2 ) and hardness of test specimens increased approximately by 29MPa and by 12 HV 1 , respectively for AR & 5 % pre-strained specimens which were aged at 160 o C for 20 minutes while, the strain ageing (ΔY 2 ) and the hardness increased approximately by 59MPa in strength and by 22HV 1 in hardness, respectively for H+N heat treated & 5 % pre-strained specimens which were aged at 160 o C for 30 minutes. An increase in tensile strength, yield strength and (ΔY 2 ) could be explained by the diffusion of interstitial atoms such as C and N, by creating a Cottrell atmosphere by which mobile dislocations are locked 4,15,[18][19][20][21] . The strengthening effect in S275JRC steel could be also explained as a result of interference with the motion of dislocation due to the presence of secondary phase particles such as Fe 3 C, nitrides and carbonitrides of alloying elements 1,14 which could be responsible for increasing the matrix hardness.…”

Section: Strain Ageing Resultsmentioning

confidence: 99%

“…These structural mild steels are generally preferred in civil engineering and industry of machinery manufacturing 9 . Remarkable researches have been carried out on the strain aging of ultra-low carbon, interstitial free; bake hardenable, dual phase and various stainless steel [9][10][11][12][13][14][15][16][17][18] . As relatively inconclusive study is available in the literature, a work is needed to investigate the materials and processing factors that are significant parameters affecting the kinetics of strain ageing of S275JRC steel which is preferred for manufacturing heavy vehicle steel wheel rim.…”

Section: Introductionmentioning

confidence: 99%

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Factors Affecting Kinetics of Strain Aging in S275JRC Steel

Bülbül

Kaçar

2016

Mat. Res.

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The materials parameter i.e. microstructure as well as the processing factors i.e. aging time and temperature, the amount of plastic deformation, and residual stresses affecting the kinetic of strain ageing in the S275JRC steel were investigated in detail. For this purpose, 5 % pre-strained steel was aged at 160 o C for different intervals. The ageing behavior was determined for the as-received (AR) and homogenization & normalizing heat treated (H+N heat treated) conditions. The yield stresses before and after aging process and, the hardness values of the aged steels were considered to calculate strain aging progress. It was shown that a noticeable increase in the yield strength, tensile strength and hardness values was observed for aged AR and H+N heat treated specimens. Moreover, the repetitive increase in the yield and ultimate tensile strength was believed to be a result of strain ageing.

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Section: Strain Ageing Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Factors Affecting Kinetics of Strain Aging in S275JRC Steel

Bülbül

Kaçar

2016

Mat. Res.

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“…This process leads to an increase of the thermoelectric power value, since the solute atoms that are "pinned" by the dislocations (constituting the so-called Cottrell atmospheres) can no longer be detected by this technique [20]. [21].…”

Section: Resultsmentioning

confidence: 99%

Influence of chemical composition and processing conditions on interstitial content of cold rolled ferritic steels

Capdevila

Cock

Caballero

et al. 2011

Materials Science and Technology

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Determining the content of solute elements in cold-rolled ferritic steels constitutes an important aspect in metallurgy, since the interstitial elements have a harmful effect on the anisotropy properties (i.e. texture) of the final product, usually steel sheets for automotive applications. Both the carbon and nitrogen contents in solid solution depend on the chemical composition and thermomechanical parameters, such as the coiling temperature and the cold reduction degree. In this work, thermoelectric power measurements technique has been applied to study the relation between the process variables such as coiling temperature and cold-rolling reduction, and the amount of interstitial elements in solid solution. It was shown that at high coiling temperatures the value of the thermoelectric power only depends on the carbon content in solid solution, meanwhile at low coiling temperatures, a second contribution should be considered due to the presence of nitrogen in solid solution.

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“…To enhance the BH strength and formability of the extra low carbon (ELC) steel more, the previous works [1][2][3][4][5] have mainly focused on contents of Ti, Nb, C, N and S. However, in contrast to these operations, we reduced the number of variables. The basic idea is that the modern steelmaking technology can make "very extra low carbon steel" which described with lower levels of C and N. Thus, the addition of Ti and Nb is not more needed for partially stabilization of C and N. The ELC steel, which has the enough BH strength above 30 MPa and excellent formability can be produced by the optimum amount of C and N.…”

Section: Introductionmentioning

confidence: 99%

Precipitation Hardening with Copper Sulfide in Cu Bearing Extra Low Carbon Steel Sheet

2009

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High strength cold-rolled bake hardenable steel sheets for automotive use have been developed. In the last decade, the major strengthening methods of extra low carbon (ELC) steel and interstitial free (IF) steel were the solid-solution strengthening with silicon, manganese and phosphorous and the precipitation strengthening with microalloying elements, such as niobium and titanium. When the steels are strengthened with the high amount of solid-solution elements such as silicon and manganese, it shows the low surface quality due to surface oxidation. In addition, phosphorous added ELC and IF steels become susceptible to the secondary work embrittlement because of the lack of grain boundary strength, which is the essential drawback of the steels.In this paper, we propose the extra low carbon bake hardenable steel which is precipitation strengthened by means of the fine distribution of Copper sulfide (Cu 2 S) precipitates instead of solid-solution strengthening and precipitation strengthening using silicon, manganese, niobium and titanium. These Cu sulfides are oriented to the body-centered cubic a-Fe matrix in (001) KEY WORDS: extra low carbon steel; Cu precipitate; sulfide; precipitation hardening; bake hardenability; cold-rolled sheet. 109© 2009 ISIJ Cu and to treat temper annealing.9-11) Thus, in case of small addition of Cu, it is difficult to form the Cu precipitate (eCu).On the other hand, some researchers studied about the solid-solution strengthening and Cu-S precipitation in Ti added ELC steel. Yamada et al. reported that the addition of 0.22 % Cu increases tensile strength about 10 MPa in Tistabilized IF steel. 12) They described that the increment of tensile strength is mainly resulted from grain refinement and solid-solution strengthening. In addition, Kejian et al. and Ishiguro et al. suggested that a residual level of Cu can make large sulfides and inclusion in Ti added steels. 13,14) However, they did not consider the possibility of precipitation hardening of Cu sulfides.Guilet et al. reported that nano-sized Cu-S precipitates can be formed in batch annealing process for Ti free low carbon steels.15) Recently, Liu et al. studied the crystallography and precipitation kinetics of copper sulfide for low carbon steel in strip casting process. 16,17) In this work, we examine the evidence of Cu-S precipitation hardening due to fine Cu 2 S for extra low carbon steels in continuous annealing process. Also, the performance of the Cu added ELC steel is compared with conventional Nb-Ti BH steel. Experiments MaterialThe materials used in this study are extra low carbon steels with a bake hardenability are listed in Table 1. In order to investigate the effect of Cu on the strengthening for the ELC steel, three ELC steels (0Cu ELC, 01Cu ELC and 02Cu ELC) that contain different content of Cu were selected. In addition, the mechanical properties of the 02Cu ELC steel are compared with conventional Nb-Ti added BH steel (Nb-Ti BH). The Nb-Ti added BH steel means that solute elements of C, N, and S are partially sc...

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Competition between grain boundary segregation and Cottrell atmosphere formation during static strain aging in ultra low carbon bake hardening steels

Cited by 79 publications

References 17 publications

Factors Affecting Kinetics of Strain Aging in S275JRC Steel

Factors Affecting Kinetics of Strain Aging in S275JRC Steel

Influence of chemical composition and processing conditions on interstitial content of cold rolled ferritic steels

Precipitation Hardening with Copper Sulfide in Cu Bearing Extra Low Carbon Steel Sheet

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