CHANGING B G BEHAVIOUR OF HYRD DOGEN SUSPECATIB IBALITY ON IF - - PDF document

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CHANGING B SUSPECATIB PRESE

Research Scholar, Depar Abstract:-The influence of niobium industry the mechanical properties a

• f if steels with deep drawabality an

In this paper these promoted transgr presence of niobium with cold rolled Key Words:- Interstitial free steel, H

• 1. INTRODUCTION

Ni-bearing interstitial free steel h drawing quality and is possibl excellent surface condition, thickn and good flatness, allowing using industries [1, 3]. Many systema results of hydrogen permeation ha in well-annealed and cold wor Hydrogen is known to degrade num particular interest are the detrim hydrogen on iron-base alloys since

• ften used in applications, whe

hydrogen is likely. Recently, the steel has been developed and ach drawing quality with a yield stres 150 MPa. Generally, the inters should be considered susceptib embrittlement due to the high diffu interstitial free steel has an ext quality and is possible to obta surface condition, thickness homog flatness, allowing using in sheet m 4].Many systematic experimen hydrogen permeation have been r annealed and cold worked iron [3 known todegrade numerous alloy interest are the detrimental effects iron-base alloys since these alloys applications, where exposure to h [5-7]. Recently, the interstitial fre developed and achieved extra-deep with a yield stress (YS) of a Generally, the interstitial free considered susceptible to hydroge due to the high diffusivity.

• urnal of Engineering, Pure and Applied Sc
• Vol. 1, No. 1, 2016

G BEHAVIOUR OF HYRD IBALITY ON IF STEELS D SENTATION OF NIOBIUM

Verjesh Kumar Magotra

artment of Physics, QSRC NITA Dongguk University, So Email: birju.srm@gmail.com um in the hydrogen suspecatibality of IF steels change s and permeation trapping of all these effects are studie and metallographic investigation concluded due to the a sgranular fracture in cold rolled specimens. All these re led susceptible for niobium hydrogen embrittlement. , Hydrogen embrittlement, Cold work, Hydrogen permea l has an extra-deep ible to obtain an kness homogeneity ing in sheet metal matic experimental have been reported

• rked iron [4–7].

numerous alloys; of rimental effects of nce these alloys are here exposure to the interstitial free chieved extra-deep tress (YS) of about terstitial free steel ble to hydrogen ffusivity Ti-bearing extra-deep drawing btain an excellent

• geneity and good

metal industries [1, ental results

• f

n reported in well- [3–7]. Hydrogen is lloys; of particular cts of hydrogen on ys are often used in hydrogen is likely free steel has been eep drawing quality about 150 MPa. e steel should be

• gen embrittlement
• 2. EXPERIMENTAL PROCE

In this study, an electrochemical was utilized to study the hydr annealed and cold worked interst Hydrogen precharged technique study the degradation pheno specimens. Table 1 Chemical Compositio steal

• Fig. 1. Optical m

annealed (b) CW 2 CW

Sciences,

1

DOGEN DUE TO M

South Korea. ge a new change for the died with a cold working e absorption of niobium. results of IF steel shows eation, Fracture surface CEDURE cal permeation technique drogen transport in the rstitial free steel at 25oC. ue was also performed to nomena in the same tion of Interstitial free l micrographs of (a) 20% (c) CW 40% (d) W 60%

International Journal of Engineering, Pure and Applied Sciences,

• Vol. 1, No. 1, 2016

2 Table-B Permeation rate, diffusivity for the interstitial free steel with a constant charging current density (10 mA/cm2 at25Jc IF steel J∞ L (mol(H)/ms D eff (m2/s) 2/s) Annealed 1.65 x10 7.81x10 CW 20% 2.59x101.77 x10 CW 40% 1.88x101.18x10 CW 60% 4.72x101.18x10 CW 80% 3.66x 103.55x10 Fig.2 Fracture surface of CW 80% specimen: (a) uncharged and (b) 5-days cathodic charged. The instrumentation and procedure were similar to those described elsewhere [8-10]. The cathodic site or hydrogen entry cell was galvano statically polarized at a constant charging current in 0. 1 N Na OH. The anodic side or hydroge n exit cell was potentiostated at 250 mV (SCE) in 0.1 N Noah. The potent iostatic curren t, i p , gives a direct measure of the hydrogen flow rate. The cell assembly was immersed at 25 F 0.5 j C. Both sides were deoxygen ated.The materials chosen for this study were an interstitial free steel and were provided by China Steel Corporation. Chemical compositions of the interstitial free steel are listed in Table 1. Specimens were cut from steel plate then heated at 850 j C for 1 hand furnace cooled. The preparation of these specimens involves cold rolled to different percent - age reduct ion and optical micrograp has are shown in Fig. 1. Then these specimens were ground with Carbimet- Sic grining paper down to 800 grit. Prior to the insertion in the test cell, each speci men was nickel plated (200 nm)

• n the anodic side to eliminate surface defects.

Table-4 The instrumentation and procedure were similar to those described elsewhere [8-10]. The cathodic site or hydrogen entry cell was galvano statically polarized at a constant charging current in 0. 1 N Na OH. The anodic side or hydroge n exit cell was potentiostated at 250 mV (SCE) in 0.1 N Noah. The potent iostatic curren t, i p , gives a direct measure of the hydrogen flow rate. The cell assembly was immersed at 25 F 0.5 j C. Both sides were deoxygen ated.The materials chosen for this study were an interstitial free steel and were provided by China Steel Corporation. Chemical compositions of the interstitial free steel are listed in Table 1. Specimens were cut from steel plate then heated at 850 j C for 1 hand furnace cooled. The preparation of these specimens involves cold rolled to different percent - age reduct ion and optical micrograp has are shown in Fig. 1. Then these specimens were ground with Carbimet- Sic grining paper down to 800

• grit. Prior to the insertion in the test cell, each speci

men was nickel plated (200 nm) on the anodic side to eliminate surface defects.

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Table-5 The tensile specimens with gage sect mm were fabricated by EDM. Tensile tested in air for the uncharged and

• conditions. The hydrogen charging

making the specimen as a cathode

• solutions. For the precharging test,

charged with a constant current densit for 5 days, then it was removed from rinsed with distilled water, acetone, pressurized air. The specimen was t strained to failure using a Shimadzu testing machine. The strain rate adopt was 105 . After completing the tensile surface was examined by sca microscope.

• 3. DATA ANALYSIS

For this study, the flux of hydrog specimen was measured in terms of current density, i Pl (mA/c m 2), an tothe steady-state hydrogen permeation 2 s), according to = /nf where n is the number of electrons inv F is the Faraday’s constant. The hydr rate (mol/m 2 s) is defined by = /nf L where L is the specimen thickne diffusion as the rate-limiting step diffusivity, Deff (m 2 /s) is related to (s), by = /6tl

urnal of Engineering, Pure and Applied Sci

• Vol. 1, No. 1, 2016

ection of 7x 25x 1 sile specimens were d cathodic charged ing was done by e in 0.1 N NaOH t, a specimen was sity (40 mA/cm 2 ) rom the electrolyte, ne, and dried with s then immediately zu AG- 300K NG

• pte d in this study

ile test, the fracture scanning electron rogen through the

• f the stead y-state

and was converted tion flux, J l (mol/m involved 1/mol and ydrogen permeation ness in mm. For tep, the effective to the time lag, t L

• 4. RESULTS AND DISCCUSI

4.1. Permeation Test The diffusivity and the perm interstitial free steel at 300 C wi current density (10 mA/cm2) are hydrogen diffusivity of annealed lower than those of pure iron [4 hydrogen trap and causing titani

• matrix. The data also clearly sho

but an increased in J L as c increased for annealed specimen decreased with increasing cold more hydrogen trapping s dislocations and deformation- 9-10 ] .Cold work increases the been explained by short-circuit dis- locations networks as wel trapping of hydrogen to dislocatio 4.2. Tensile Testing Tensile proper ties of hydrogen c specimens are listed in Table 3. a slight loss in mechanical pro hydrogen charging for all cold slight improvement for annealed charged specimen s, it is mainly even the 80% cold- rolled specim 2(a) , while the fractograph s cleavge effect with a partial ducti a 5-day hydrogen charged. T explained as more hydrogn t worked specimen with higher di hydrogen precharged annealed slight improvement in strength a explained as the tiny titanium hy matrix, providing the easy glide precipitates also enhancing streng

• 5. CONCLUSION

The work which is presented i that cold worked interstitial free hydrogen degradation .with the p REFERENCES [1]

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3 SION ermeation rate of the with a constant charging re listed in Table 2. The ed interstitial free steel is [4 – 6]. It is due to the nium hydride formation show a decreased in Deff s cold-rolled percentage

• ens. The value of Deff is

ld work, is due to the site resulting from

• induced microvoids [

e J L , this effect has it diffusion paths down ell a s by low energy ation [7-8] . n charged and uncharged

• 3. The tensitle data show

roper ties with a 5-day ld-rolled specimens, but led specimen.For the un ly simpleductile fracture, cimen as show n in Fig. h shows a trangronular ctile fracture surface for . This results can be trapping site in cold dislocation density. The ed speci- means show h and elonogation can be hydride formation in the de of dislocation, and the ength. in this paper indicates ree steel is susceptible to e presence of niobium. i, Trans. Jpn. Inst. Met. deja, J.A. Pero-Sanz, M 45 i, W.W. Bose Filho, Int. g, Acta Mater. 46 (1998)

International Journal of Engineering, Pure and Applied Sciences,

• Vol. 1, No. 1, 2016

4 [5] D.L. Johnson, J.K. Wu, J. Mater. Energy Syst. 8 (1987) 402` [6] R.D. McCright, “Stress Corrosion Cracking and Hydrogen Em-brittlement of Iron Base Alloys”, NACE, Houston, TX, 1977, p. 306 [7]

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