Formability of Al-killed AISI 1040 Medium Carbon Steel for Cylindrical Cup Formation

Abstract

The basic formability of Aluminum-killed AISI 1040 graded medium carbon steel (cold rolled followed by hardening and spheroidization tempering) has been characterized by uniaxial tension, compression, bending, and Erichsen cup tests.

The results shows a good strength (~634 MPa) - ductility combination, high strain hardening exponent, normal plastic anisotropy value >1 and a considerably low planar anisotropy. The compressibility, bendability and biaxial strechability characteristics of the steel also signify its formability behavior in different loading states. The strain analysis on tensile and Erichsen cup specimens has provided deeper information on its strain dispersibility as well as necking tendency in both uniaxial and biaxial states.

The actual press formability also has been investigated by applying a process consisting of multistage deep drawing accompanied with wall ironing, without using blank holder and with intermediate stress relieving treatment. Thus ~56 mm long cylindrical cups, ~36.85 mm diameter and ~3.8 mm wall thickness, have been manufactured from 12 mm thick and 60 mm diameter circular blanks in a preformed shape. This experiment has yielded significant values of few press formability parameters in terms of draw ratio, draw reduction, ironing ratio, ironing reduction and etc. Further, by drawing comparisons with few sheet metals, the competitiveness of the steel has been shown with an objective to enlighten on its line of applications as per customer demands.

1. Introduction

In industries, low carbon steels are extensively used in cup drawing, because of their high inherent ductility. Because of low carbon content, these steels cannot receive heat treatment, resulting low strength, constricting their range of applications and demanding for a tryout of medium and high carbon steels as alternative high strength grades.¹⁾ Medium carbon steels, carbon content 0.30 to 0.60%, are mostly used in general engineering applications. Heat-treatability makes these steels applicable with moderate strength and toughness. Inherent low formability is the main limitation of these steels. In these steels pearlite lamellar morphology imparts undesirable mechanical properties, whereas globular cementites in ferrite matrix improves cold workability.²⁾

Sheet metal works are dependent on their basic formability characteristics. Formability depends on strength and ductility.³⁾ Strength decides the size of the machinery, while ductility determines the deformation ability of the material used. For a defect free product, it needs to maximize the mean normal anisotropy (r_m) and minimize the planar anisotropy (Δr) of the material.⁴⁾ A high strain hardening exponent (n) imparts uniform strain dispersability, improves biaxial stretchability and thus increases limit drawing ratio (LDR).^5,6,7) Formability characteristics are determined by different laboratory scale tests, such as: simple tension, compression, bend and cup tests etc. Although these tests do not simulate the actual sheet forming process, still a correlation exists between them. When a cup forming experiment in actual condition is conducted, the investigation is found complemented with each other.

Cylindrical cup drawing is an important and complex press forming process,⁸⁾ which has numerous applications in industries of different fields. These cups are normally produced by deep drawing process either in a single stage or multistage depending on the material, cup size and geometry etc. Sometimes, wall ironing process combining with deep drawing is applied for producing cups with a greater height-to-diameter ratio and reduced uniform wall thickness.^{9,10,11,12,13)} Manufacturability by these processes is directly dependent upon the press formability of sheet metals. In actual conditions, the process variables have the greatest influence on the overall formability and are commonly judged by die tryout.⁷⁾

In the present work, Aluminum-killed AISI 1040 graded medium carbon steel was selected as an alternative high strength material. The steel strips were made by hot rolling followed by cold rolling operation. Unlike to conventional sheet metal treatment (annealing) method, herein suitable microstructure was developed by a heat treatment cycle consisting of hardening with water quenching followed by prolonged spheroidal tempering to build up a good strength-ductility combination in the steel. The basic formability parameters were characterized by conducting few conventional tests on laboratory scale. The press formability was also examined in actual state of applications of cup manufacturing by multistage deep drawing operation. Further, the steel was compared with few literature obtained sheet metals, in respect to tensile properties and formability characteristics.

To the best of authors’ knowledge, formability characterization of any medium carbon steel is less to be attended. Further, the study on actual press formability of this grade of steels by multistage deep drawing with simultaneous ironing process is also rarely available. Nevertheless, the application of 12 mm thick circular blanks for forming long cylindrical cup is almost found nonexistent. Such lack of information possibly arise the needs of this investigation work to fill up the gap and thus created databank would serve as a potential reference for process engineers in the field of deep drawing, automobile and defence industries.

2. Experimental

2.1. Material

The chemical composition of as received Al-killed AISI 1040 graded medium carbon steel was reported in Table 1. The basic input material, 14 mm thick strips (cold rolled with 15% reduction) were subjected to a heat treatment cycle, hardening (heating at 1133°K for 1 hour - water quench) followed by prolonged tempering at 923°K for 36 hours - furnace cooling to 473°K - air cooling to room temperature (298°K).

Table 1. Chemical composition of the steel (in %wt.).

Elements	C	Mn	Si	S	P	Ni	Cr	Mo	Al	Cu	Sn	As	Sb	Fe
wt%	0.39	0.79	0.34	0.009	0.005	0.12	0.18	0.10	0.05	0.08	0.0059	0.0053	0.0018	Bal.

Note: H, O and N are 1.8, 18.4 and 82.3 ppm respectively; Bal. = balance quantity.

2.2. Microstructure Examination

The microstructures of steel samples, etched in 2% nital solution, were examined using both optical (OM) and scanning electron microscopes (SEM). The typical microstructures are shown in Figs. 1(a) and 1(b), which show uniformly distributed globular cementites in an equiaxed ferrite matrix.

Fig. 1.

Typical micrographs of the steel strip, (a) image by OM, and (b) image by SEM.

2.3. Tensile Test and Formability Characterization

Tensile test was conducted at room temperature on flat specimens (5 mm thickness, 6.5 mm width and 32 mm gauge length) along 0° (longitudinal), 45° (diagonal), and 90° (transverse) to the rolling direction (RD), shown in Fig. 2(a). The testing was done by a Tensometer (20 kN; make, KIL; model, PC 2000) at a strain rate, 2.5 × 10⁻⁴ s⁻¹, according to Indian Standard IS 1608: 2005. True values of tensile properties, yield strength (YS); tensile strength (UTS); yield ratio (YR); uniform elongation (UEl.); total elongation (TEl.) were determined from load-extension curves. The strain hardening exponent (n), an indicator of formability, was evaluated by regression method, applying on flow curves. Formability indicators, plastic strain ratios (r) were evaluated from tensile tests (Fig. 2(b)), at an elongation 16–17% of UEl and using Eq. (1), as per Indian Standard IS 11999: 2007.   

$$r={\epsilon }_{\mathrm{w}}/{\epsilon }_{\mathrm{t}}=ln(w_0/w)/\mathrm{l}\mathrm{n}(t_0/t)$$(1)

Where, ε_w and ε_t = true strain along width and thickness respectively; w₀ and t₀ = Original width and thickness respectively; w and t = specimen width and thickness after test respectively.

Fig. 2.

Photo images of tensile specimens, (a) test up to break, and (b) test up to 16–17% of UEl.

The product ‘n.r’, as an indicative of overall press performance factor,⁷⁾ was also evaluated along each orientation. The mean value of each parameter, such as, n_m; r_m (normal anisotropy); Δr (planar anisotropy); n.r_m, were calculated by standard equations given in Table 2.

Table 2. Tensile properties and formability characteristics.

Orientation w.r.t. RD (°)	YS (MPa)	UTS (MPa)	YR (%)	UEl.32 (%)	TEl. (%)	n -value	r -value	n.r	Hardness(VH)
0	390.14	651.84	59.85	22.2	40.97	0.437	1.11	0.485	202
45	374.4	629.8	59.45	23.98	38.9	0.418	1.01	0.422
90	354.83	624.44	56.82	22.57	33.77	0.399	1.27	0.507
Normal mean (Xm)	373.44	633.97 ≈ 634	58.89 ≈ 59	23.18 ≈ 23.2	38.13	0.418 ≈ 0.42	1.1	0.459 ≈ 0.46
Planar mean (ΔX)							0.18

Note: X_m = (X₀ + 2X₄₅ +X₉₀)/4; ΔX = (X₀ − 2X₄₅ +X₉₀)/2; UEl32, Uniform elongation in 32 mm; r -value measured at 16–17% of UEl.; n.r = Overall press performance factor.

2.4. Compression Test

The compression test was conducted on 20 × 20 mm² specimens (Fig. 3(a)) of various thicknesses (12.8 mm, 6 mm, 4.2 mm and 3.8 mm). The test was done on a universal testing machine, 80 tons, at room temperature without using lubricant, as per ASTM Standard D 695 - 02a. Specimens were subjected to a compression load, 50 tons, for 60 seconds. The compressive stresses and strains were evaluated by using standard formulae.⁴⁾

Fig. 3.

Photo images of specimens in, (a) compression test, and (b) bend test.

2.5. Bend Test

Simple bend test was conducted on 87 mm long, 25 mm wide and 5 mm thick specimens (marked with 5 mm square grids), along 0°; 45°; 90° to the RD, by a universal testing machine, as per Indian Standard IS 1599: 1985. Specimens were bent in different patterns, such as: V - 45° + R5 radius, U - 180° + R3 radius and a complete bend by flattened upon them - 180° + R0.5 radius (Fig. 3(b)). The tensile strain at outer fibers on bend radius was determined by measuring the grids at deformed location for each specimen.

2.6. Erichsen Cup Test

Erichsen cup test was conducted on 2 mm thick steel samples of 75 mm length and varying widths such as: 56 mm, 38 mm, 21 mm and 15 mm (Figs. 4(a)–4(e)), which were with printed with 2.5 mm square grids by electro etching on copper sulphate coated surfaces. Testing was done at room temperature, by an electro-hydraulic drive ERICHSEN sheet metal testing machine (model, 140; drawing force, 0–30 kN; sheet holding force, 0–34 kN), assembled with 20 mm diameter spherical punch, as per Indian Standard IS 10175 (Part 1): 1993. Erichsen Index (IE) for each sample was measured as the respective cup height.

Fig. 4.

(a–e) Photo images of Erichsen cups, and (f) Graphical showing of FLD.

2.7. Formability Limit Diagram (FLD)

From the Erichsen cup test with varying widths, true major (ε₁) and minor (ε₂) strains were calculated by measuring deformed grids^2,14,15) printed on cups and the result was represented in a 2D strain space (Fig. 4(f)), known as formability limit diagram (FLD).¹⁶⁾ In order to obtain the maximum value of minor strains, tensile test was also done with samples of 2.5 mm grid marked. A line was drawn just below the points under visible necking as well as of the fracture zone to represent the formability limit curve (FLC).

2.8. Thickness Reduction Distribution Profile

In order to identify strain dispersibility of the steel under deformation, distribution of thickness reduction rate was estimated for tensile specimens (Figs. 2(a) and 2(b)) with respect to different positions around a centre line (passing through centre of specimens), referred as the pole line. A similar analysis was also carried out in the cup test. This study considered orientations (0°, 45° and 90° to the RD) in both cases.

2.9. Strain Distribution Profiles in Cup Test

In Erichsen cup test the steel was considered to involve with strains such as: radial or major strain (ε_mj.), hoop or minor strain (ε_mn.) and thickness strain (ε_thk.). The distribution of these strains around a pole line was predicted by measuring the deformed square grids (2.5 mm) at different locations on the cup specimen, 75 mm width. The major and the minor strains of a deformed square grid were evaluated by using Eqs. (2)–(3).⁸⁾   

$${\epsilon }_{\mathrm{m}\mathrm{j}.}=ln(d_1/d_0)$$(2)

  

$${\epsilon }_{\mathrm{m}\mathrm{n}.}=ln(d_2/d_0)$$(3)

Where, d₀ = side of grid before test, d₁ and d₂= major and minor side of the deformed grid respectively.

The corresponding thickness strain (ε_thk.) was estimated by considering volume constancy formula,⁸⁾ Eq. (4).   

$${\epsilon }_{\mathrm{m}\mathrm{j}.}+{\epsilon }_{\mathrm{m}\mathrm{n}.}+{\epsilon }_{\mathrm{t}\mathrm{h}\mathrm{k}.}=0$$(4)

The resultant effective strain (ε_eff.) at a particular location was determined by slab method,⁸⁾ Eq. (5).   

$${\epsilon }_{\mathrm{e}\mathrm{f}\mathrm{f}.}={\{2/3({\epsilon }_{\mathrm{m}\mathrm{j}.}{}^2+{\epsilon }_{\mathrm{m}\mathrm{n}.}{}^2+{\epsilon }_{\mathrm{t}\mathrm{h}\mathrm{k}.}{}^2)\}}^{0.5}$$(5)

Herein also, the study considered orientations, 0°; 45°; 90° to the RD, and separately presented their strain profiles around the pole line.

2.10. Press Formability by Multistage Deep Drawing with Ironing Process

Flat circular blanks (Fig. 5(a)), 60 mm diameter; 12 mm thick, were stamped to a preformed shape (Fig. 5(b)) of 60 mm diameter; 13.5 mm as average thickness, from which cylindrical cups (Figs. 6(d)–6(f)) were manufactured by deep drawing with simultaneous ironing process in three stages without using blank holders. The process as first, second and third as final draw were conducted on mechanical presses of 500 tons (83 mm/s), 350 tons (183 mm/s) and 250 tons (192 mm/s) respectively, assembled with draw die-punches, schematically shown in Figs. 6(a)–6(c). The intermediate stress relieving treatment was applied by heating at 933–983°K for 4 hours, followed by furnace cooling to 473°K and air cooling to room temperature. The components were also undergone an intermediate surface treatment by acid pickling (HCl: 6–7%, PH: 2–5); phosphating; lubricating by immersing in soap solution (33% soap flakes) for 2 hours to ensure a proper diffusion of the lubricant into porous layer of phosphate coating.

Fig. 5.

Photo images of, (a) circular flat blank, and (b) preformed blank.

Fig. 6.

3-stage cup drawing process, (a–c) schematically showing of arrangements, and (d–f) photo images of drawn cups.

After drawing in the final stage, microstructure of the cup (at mouth zone) was examined by OM and SEM for observing grain size (Fig. 7(a)) and micro-defect (Fig. 7(b)) respectively. In order to evaluate drawability and ironability parameters in each stage of forming step, dimensions of drawn cups were measured by micrometers and vernier calipers.

Fig. 7.

Typical micrographs of the final drawn cup wall, (a) image by OM, and (b) image by SEM.

3. Results and Discussion

3.1. Microstructure

From Fig. 1(a) and as per IS4748:1988, average grain size is determined as ASTM No. 7–8, a favorable range for deep drawing⁷⁾ with good surface finish.^2,17) The microstructure (Fig. 1(b)) is revealed as consisting of uniformly distributed globular cementites in equiaxed ferrite matrix, indicates to good cold formability with strength.^17,18)

3.2. Tensile Properties and Formability Characteristics

Table 2 represents tensile properties of the steel, showing their anisotropic values. It exhibits the average (mean) UTS 634 MPa with YR 59% and TEl 38.13% with UEl 23.2%, indicate a good combination of strength-ductility, which is attributed by the microstructure obtained from the heat treatment cycle adopted.

Table 2 also presents formability characteristics with their degrees of anisotropy. The mean n -value, 0.42, indicates to high stretchability with uniform strain dispersibility.⁵⁾ The normal anisotropy, r_m –value is evaluated as 1.1, i.e. >1 (isotropic value), signifies that the steel has moderate drawability. The planar anisotropy with Δr -value, 0.18, a low value, confirms its good earring resistance. More importantly, by getting ‘nr_m’ -value, 0.46, the overall press performance factor of the steel is said to be high, considering the results shown by Kumar⁷⁾ for low carbon steels.

3.3. Compressibility

Table 3 shows compression test results, such as: % of thickness reduction; increase in cross section area; strain; stress, which represent the degree of compression with respect to thicknesses of specimens. This is indirectly indicates to ironability of the steel under static loading condition without using lubricant, which is likely to increase further upon use of suitable lubricants under high speed press work. Herein, the maximum compressive strain, 32.41%, is being obtained at a stress, 577.78 MPa, for the specimen thickness 12.8 mm. It is also observed that the compressibility, in terms of strain value, reduces on decreasing of sample thickness, which is as expected from the experiment. Further is confirmed its good compressibility by observing crack free surfaces on compressed specimens (Fig. 3(a)).

Table 3. Compression test results.

Specimen thickness (mm)	Thickness reduction (%)	Increase in area (%)	Strain (%)	Stress (MPa)	Surface condition
12.8	27.68	38.27	32.41	577.78	O
6.0	22.25	28.62	25.17	541.14	O
4.2	17.18	20.75	18.86	504.18	O
3.8	12.7	14.54	13.58	482.33	O

Note: Surface condition as O = good (no crack) and Δ = crack.

3.4. Bending Formability

Table 4 illustrates the degree of bending formability with anisotropic behaviors and also surface condition on bent surface. It shows a crack free bent surface (Fig. 3(b)) in the most severity condition of bending by 180°+R0.5, at the lowest possible ‘R/t’ (R, bend radius; t, specimen thickness) ratio, 0.1, which is significant. This mode of bending also shows the maximum tensile strain value, 62.5%, for outer fibers on the bent surface, indicates its excellence in bending formability.

Table 4. Bend test results.

	Bent by 45°+R5			Bent by 180°+R3			Bent by 180°+R0.5
Angle (°) to RD	0	45	90	0	45	90	0	45	90
Tensile strain at outer fibers on bend radius (%)	41.5	42.5	45.5	54	55	58	61	62	65
Mean (Xm) in %	43			55.5			62.5
R/t ratio	1			0.6			0.1
surface condition on bent surface	O			O			O

Note: X_m = (X₀ + 2X₄₅ +X₉₀)/4; R = bend radius, t = thickness; surface condition as O = good (no crack) and Δ = crack.

3.5. Stretch Formability

Table 5 summaries Erichen Index (IE) -values of cup specimens (Figs. 4(a)–4(e)) of different widths, formed in Erichsen test. These IE -values shows an increasing trend with reduction in sample width. The value, 11.95, for the specimen of width 75 mm, represents the biaxial strechability of the steel and is considered to be higher than a value, reported by Sunil and Pai³⁾ for the steel with 0.15% carbon.

Table 5. Erichsen cup test results.

Specimen width (mm)	Erichsen Index, IE -value (mm)	Crack type	Crack orientation w.r.t. RD
75	11.95	X	90°
56	11.82	X	90°
38	13.28	Δ	90°
21	16.11	Δ	90°
15	22.17	O	–

Note: Crack type as O = good (no crack), Δ = hair crack and X = through crack.

3.6. Formability Limit Curve (FLC)

Figure 6(f) shows the formability limit diagram (FLD), wherein true major and minor strains, evaluated from deformed square grids on Erichsen test made cups, are plotted as fail; marginal; safe values. Thus is obtained a demarcation line, known as true formability limit curve (FLC), which distinguishes a safe forming zone for the steel. The lowest forming limit, with a true FLC₀ -value, 33.451%, is observed at the plain strain condition (ε₂ = 0).²⁾ This value is found larger than that of a DP 980 steel sheet, FLC₀ < 15%, reported by Firat.¹⁹⁾ Although the value is observed lower than that of a SAE 1050 steel,¹⁾ low carbon steels⁷⁾ and a TRIP 600 steel,¹⁹⁾ which may be due to inherent weaker texture⁴⁾ of the steel, attributed by insufficient cold reduction, that needs more experimental works.

3.7. Strain Dispersibility

Figure 8(a) shows thickness reduction rate distribution profile of tensile specimens, wherein curves for tensile loading up to break and for loading up to 16–17% of UEl, are expressed by dotted and firm lines respectively. In both the cases, thickness reduction rates along all orientations are found considerably uniform around the pole line, signify to homogeneous strain dispersibility, attributed by high n-value.⁵⁾ Similar trends are also observed for curves (Fig. 8(b)) in Erichsen cup test, confirms uniform strain dispersibility in biaxial state also. More importantly, peaks of curves (around dome of the cup) indicate to a crack sensitive zone, which is confirmed by observing cracks lying in this area, not on the dome.

Fig. 8.

Thickness reduction rate distribution profiles of, (a) tensile tests, and (b) Erichsen cup test.

3.8. Strain Profiles

Figures 9(a)–9(c) exhibit strain distribution profiles of the cup formed in Erichsen test, along 0°, 45° and 90° to the RD respectively, which represent indirectly the deformation pattern in a biaxial state. In figures, major and minor stains are found to gradually increase (with positive values) up to their respective peak and afterwards they decrease up to the center, exactly above the punch, a region under minimum deformation. In case of thickness stains, a similar trend is observed but with negative values, attributed to reduction in specimen thickness. The effective strain, a resultant of these three stains, is found influenced by major and minor strains. Almost a similar trend is seen for all the strains along 0°; 45°; 90° to the RD, although a greater uniformity is observed for strain curves along 45°. Further, the curves show two distinct peaks (symmetrically located on either side of the pole line), indicate a zone of localized thinning,⁷⁾ the weaker part of the cup.

Fig. 9.

Strain distribution profiles of Erichsen cup along, (a) 0°, (b) 45°, and (b) 90° to RD.

3.9. Press Formability: Effects of Multistage Deep Drawing with Ironing

3.9.1. Evolution of Cup Dimensions and Quality

Table 6 summarizes dimensions of cups drawn in each draw stage. It shows, a cylindrical cup of size, 56 mm length; 36.85 mm diameter; 3.8 mm wall thickness, has been drawn with good surface finish and free from common forming defects (Fig. 6(f)), which conform the process feasibility as well as the press formability of the steel.

Table 6. Results of cup forming by multistage deep drawing with ironing.

	Punch and Cup size (mm)					Deep Drawability		Ironability
Draw Stages	Punch Dia. (Dp)	Initial Dia. (Do)	Finish Dia. (D)	Initial Thick. (to)	Finish Thick. (t)	Draw Ratio (β)	Drawing Reduction (rd) %	Ironing Ratio (IR)	Ironing Reduction (ri) %
1st draw	30.8+0.05	60+0.25	43+0.06	13.5+0.5	6+0.1	1.95	48.67	2.25	55.55
2nd draw	30.1+0.05	43+0.06	38.7+0.06	6+0.1	4.2+0.1	1.28	22.22	1.43	30.00
3rd draw	29.1+0.05	38.7+0.06	36.85+0.06	4.2+0.1	3.8+0.1	1.26	21.03	1.10	09.52
Overall Stages						2.06 (LDR)	51.50	3.55 (LIR)	71.85

Note: LDR = limit draw ratio, and LIR = limit ironing ratio.

3.9.2. Evolution of Microstructure

From Fig. 7(a) average grain size is determined as ASTM No. 9–10, indicates to a refinement of grains, attributed to enhancement of mechanical properties of the cup,²⁰⁾ agreed by Suresh et al.²¹⁾ From Fig. 7(b), a micrograph of x5000 magnification, no appreciable change is observed in microstructure during such complex deformation process. Further is also revealed that the microstructure doesn’t contain any micro-defect, manifests the press formability of the steel.

3.9.3. Evolution of Deep Drawability and Ironability Parameters

Table 6 summarizes drawability and ironability parameters, evaluated in each draw stage, wherein all parameters show maximum values in the first stage, confirms the forming severity in this stage. Later on they are found decreasing in subsequent stages.

Considering overall steps, the cup drawing process is found consisting of an overall draw reduction 51.5%; limit draw ratio (LDR) 2.06; overall ironing reduction 71.85%; limit ironing ratio (LIR) 3.86, which are significant and indirectly quantify the press formability in actual conditions.

3.10. A Comparison with Literatures

In order to find an appeal of the steel in industries, a comparison study has been conducted with few conventional sheet metals, obtained from literatures.^{1,5,7,22,23,24,25,26,27,28,29)} Figures 10(a)–10(c) show three different comparison sheets, TEL vs UTS; YR vs UTS; r_m vs n –values. These figures are self explanatory, wherein the steel is distinguished with relatively a better position and thus finds its applicability in deep drawing industries. Considering some parameters, the steel also finds its superiority than many grades of sheet metals and even offers a fair competition to few AHSS (Advance High Strength Steels) grades, which are significant.

Fig. 10.

Comparisons of the steel with conventional sheet metals with respect to, (a) TEl. vs. UTS; (b) YR vs. UTS; (c) r_m vs. n –value.^{1,5,7,22,23,24,25,26,27,28,29)}

4. Conclusions

(1) In this paper, a heat treatment cycle, hardening by water quenching followed by prolonged (36 hours) tempering (at 923°K), was proposed for enhancement of strength and formability of Al-killed AISI 1040 graded steel strips. The results of formability characterizations on laboratory scale draw following conclusions:

a) The steel with UTS ~634 MPa can be used in deep drawing applications of moderate strength, although degrees and sequences of forming processes should be carefully selected by considering its moderate drawability attributed to r_m –value, 1.1; Δr –value, 0.18; UEl, ~23%; true FLC₀ -value, 33.451%.

b) By showing a large total elongation (TEl), ~38%; high strain hardening exponent (n_m) –value, 0.42; Erichsen Index (IE ) –value, 11.95; uniform strain dispersibility behavior, the steel finds applicability in forming under a highly stretchable condition.

c) The good compressibility and excellent bendability characteristics further enlarge its application area to a wider range.

d) The experimentally obtained formability limit diagram (FLD) and strain profiles cups made in Erichsen cup test, can help process engineers to identify the forming limits of the steel for a safe application.

(2) The actual state of press formability of the steel was experimentally investigated while manufacturing of cylindrical cups by three stage deep drawing accompanied with ironing and thus corresponding findings draw following conclusions:

a) The degrees of press formability (with respect to the process parameters used in) in terms of drawability and ironability for whole processing stages were obtained as: overall draw reduction 51.5%; LDR 2.06; overall ironing reduction 71.85%; LIR 3.86.

b) The success of forming process interaction with the steel, was evidenced by, i) observing good surface finish on cup walls; ii) revealing no micro defect; iii) manifesting grain refinement as an additional advantage.

c) Wall ironing is recommended to be adapted with deep drawing process for the steel to prevent forming difficulties caused by the low r_m -value.

(3) Moreover, the experimental results and the comparison study with literatures suggest for the investigated medium carbon steel with ample applicability in deep drawing, automobile, defence and other metal forming industries, as a suitable alternative high strength grade.

Acknowledgements

The material and experimental supports extended from Sr. General Manager, Metal & Steel Factory, Ishapore, India, is gratefully acknowledged by the Authors.

References

• 1)   R. L.  Plaut,  A. F.  Padilha,  N. B.  Lima,  C.  Herrera,  A. F.  Filho and  L. H.  Yoshimura: Mater. Sci. Eng., A499 (2009), 337.
• 2)   W. F.  Hosford and  R. M.  Caddell: Metal Forming - Mechanics and Metallurgy, 3rd ed., Cambridge Univ. Press, UK, (2007), 185, 241, 293.
• 3)   S. U.  Sunil and  K. B.  Pai: IOSR - J. Mech. Civ. Eng., 11 (2014), 52.
• 4)   G. E.  Dieter: Mechanical Metallurgy, ed. by S. I. Metric, 3rd ed., Mc Graw-Hill Book Company, London, (1988), 520, 671, 672, 678.
• 5)   T.  Kimura: Kobelco Technol. Rev., 30 (2011), 85.
• 6)   C.  Meric,  N. S.  Koksal and  B.  Karlik: Math. Comput. Appl., 2 (1997), 119.
• 7)   D. R.  Kumar: J. Mater. Process. Technol., 130–131 (2002), 31.
• 8)   W. K.  Jawad: Iraq Acad. Sci. J. - Eng. Technol., 26 (2008), 29.
• 9)   J. M.  Choi and  J. H.  Kim: Trans. Mater. Process., 24 (2015), 115.
• 10)   P. D.  Barros,  J. L.  Alves,  M. C.  Oliveira and  L. F.  Menezes: Proc. 10th World Cong. on Comput. Mech., Blucher Mech. Eng. Proc., Vol. 1, Blucher, Sao Paulo, (2014), 3954.
• 11)   S.  Aleksandrovic,  M.  Dordevic,  M.  Stefanovic,  V.  Lazic,  D.  Adamovic and  D.  Arsic: Tribol. Indust., 36 (2014), 293.
• 12)   M. M.  Moshksar and  A. H.  Kalvarzi: Mater. Manuf. Process., 16 (2007), 461.
• 13)   J.  Nam and  K. S.  Han: ISIJ Int., 40 (2000), 1223.
• 14)   L. J.  Kilfoil: MSc. (Eng.) Thesis, Queen’s University, Ontario, Canada, (2007), 7, 8, 11–15, 33–40.
• 15)   S.  Sadagopan: Formability Characterization of a New Generation of Advanced High-Strength Steels-AISI/DOE Technology Roadmap Program, Report No. TBD, U.S. Department of Energy, Pittsburgh, (2003), 47.
• 16)   R. P.  Ramsingh and  H. K.  Raval: Int. J. Appl. Eng. Res., 4 (2009), 2377.
• 17)   K.  Banerjee: Physical Metallurgy and Drawability of Extra Deep Drawing and Interstitial Free Steels, Recrystallization, Chapt.7, ed. by Prof. Krzysztof Sztwiertnia, InTech Europe, Croatia, (2012), 141, 144, 147.
• 18)   L.  Storojeva,  D.  Ponge,  R.  Kaspar and  D.  Raabe: Acta Mater., 52 (2004), 2209.
• 19)   M.  Firat: Comput. Mater. Sci., 43 (2008), 802.
• 20)   K.  Shah,  D.  Bhatt,  T.  Panchal,  D.  Panchal and  B.  Dogra: Int. J. Emerg. Res. Manag. Technol., 3 (2014), 16.
• 21)   K.  Suresh,  S. D.  Bagade and  S. P.  Regalla: Mater. Manuf. Process., 30 (2015), 1202.
• 22)   T.  Irie,  S.  Satoh,  K.  Hashiguchi,  I.  Takahashi and  O.  Hashimoto: Trans. Iron Steel Inst. Jpn., 21 (1981), 793.
• 23)   C.  Ozek and  E.  Unal: Mater. Manuf. Process., 26 (2011), 1117.
• 24)   S.  Aleksandrovic,  M.  Stefanovic,  D.  Adamovic and  V.  Lazic: J. Mech. Eng., 55 (2009), 392.
• 25)   N.  Arab: Merit Res. J. Pet. Geol. Min., 1 (2013), 001.
• 26)   S. A. J.  Jahromi,  A.  Nazarboland,  E.  Mansouri and  S.  Abbasi: Iran. J. Sci. Technol., Trans. B, Eng., 30 (2006), 377.
• 27)   R. T.  van Tol,  J. K.  Kim,  L.  Zhao,  J.  Sietsma and  B. C.  De Cooman: J. Mater. Sci., 47 (2012), 4845.
• 28)   S.  Matsuoka,  K.  Hasegawa and  Y.  Tanaka: JFE Tech. Rep., 10 (2007), 13.
• 29)   Y.  Sakuma,  N.  Kimura,  A.  Itami,  S.  Hiwatashi,  O.  Kawano and  K.  Sakata: Nippon Steel Tech. Rep., 64 (1995), 20.