The paper presents a theoretical analysis of the process of drawing TRIP-effect steel wires involving simulation of the drawing process. The process was run following two variants, with small and large partial drafts for three drawing speeds: 1,11; 0,23 and 0,005 m/s. The investigations carried out allowed a relationship between the amount of retained austenite and strain intensity and strain rate to be established for TRIP steel wires drawn

S. Wiewiórowska

Z. Muskalski

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32  METALURGIJA 52 (2013) 1, 32-34S. WIEWIÓROWSKA, Z. MUSKALSKIANALYSIS THE INFLUENCE OF DRAWING PROCESS PARAMETERS ON THE AMOUNT OF RETAINED AUSTENITE IN TRIP STEEL WIRESReceived – Prispjelo: 2012-03-21Accepted – Prihvaćeno: 2012-07-30Original Scientifi c Paper – Izvorni znanstveni radISSN 0543-5846METABK 52(1) 32-34 (2013)UDC – UDK 621.778.001.5=111S.Wiewiórowska, Z.Muskalski, Czestochowa University of Technology, Czestochowa, PolandThe paper presents a theoretical analysis of the process of drawing TRIP-eff ect steel wires involving simulation of the drawing process. The process was run following two variants, with small and large partial drafts for three drawing speeds: 1,11; 0,23 and 0,005 m/s.  The investigations carried out allowed a relationship between the amount of re-tained austenite and strain intensity and strain rate to be established for TRIP steel wires drawn. Keywords: drawing, TRIP steel, wires, austeniteINTRODUCTIONThe drawing process is a complex process, in which the selection of optimal parameters, i.e. drawing speed and the magnitudes of partial drafts and total draft, sig-niﬁ cantly inﬂ uences the properties of ﬁ nished wire [1,2]. Published research on high-alloy austenitic TRIP steels has indicated an effect of strain intensity, strain rate, chemical composition and deformation tempera-ture on the effectiveness of the martensitic transforma-tion [3].ORIGINAL INVESTIGATIONThe investigation involved carrying out a theoretical analysis of the drawing process by means of process simulation using Drawing 2D, a ﬁ nite elements method-relying software program.The drawing process was conducted following two variants, with either small or large partial drafts (Table 1), for three drawing speeds: 1,11; 0,23 and 0,005 m/s. A friction coefﬁ cient value of µ = 0,06 (the convention-al drawing process) and the 2α drawing angle equal to 12 ° were assumed.The investigation enabled the determination of the strain intensity distribution for TRIP steel wires in par-ticular draws for different drawing speeds. Figure 1 rep-resents example strain intensity distributions in wires drawn with large partial drafts, at a high drawing speed of 1,11 m/s.From the nodes of the ﬁ nite element grid, the values of strain intensity of wire on exit from the drawing die sizing part were red out, while the strain rate was calcu-lated from the formula for the mean strain rate in the die approach part, as represented by the formula below (1):  −=1ln6.kcHmdtgv (1)where:  vc – drawing speed, λ - elongation factor, dk – ﬁ nal wire diameterRetained austenite volumetric fractions of the struc-ture of wire rod and wires after the process of drawing with either small or large partial drafts and three draw-ing speeds, as determined in previous experimental tests Table 1  A summary of partial drafts and the total draft used for wire drawn from φ 6,25 mm to φ 4,46 mmWire diameter /mm 6,25 5,60 5,20 4,80 4,46Variant 1 Gcz / % - 18,41 13,77 14,79 13,66Variant 2 Gcz / % - - 29,65 - 26,43Gc / % - 18,41 29,65 40,06 48,25 Draw 1  Draw 2Figure 1  Strain intensity distribution in wires drawn with large partial drafts and a drawing speed of 1,11 m/s33METALURGIJA 52 (2013) 1, 32-34S. WIEWIÓROWSKA et al.: ANALYSIS THE INFLUENCE OF DRAWING PROCESS PARAMETERS ON THE AMOUNT...[4], were assigned to respective values of strain rate and strain intensity. Results illustrating the amount of retained austenite (vγ) as a function of strain intensity on the surface and in the axis of drawn wires, for different strain rates, are given in Tables 2÷5.Table 2  The amount of retained austenite (vγ) as a function of strain intensity and diff erent strain rates on the surface of wires drawn with small partial draftsε ε⋅ /s-1 νγ /%0 0 23,950,24 78,57 10,310,39 86,53 7,500,55 93,02 6,150,69 99,99 5,310,19 16,28 13,320,32 17,93 11,500,44 19,27 9,100,55 20,72 7,900,17 0,35 15,370,28 0,38 12,650,39 0,41 10,020,48 0,42 8,98Table 3  The amount of retained austenite (vγ) as a function of strain intensity and diff erent strain rates in the axis of wires drawn with small partial draftsε ε⋅ /s-1 νγ /%0 0 23,950,21 78,57 12,820,35 86,53 10,120,51 93,02 8,140,65 99,99 6,540,16 16,28 15,210,27 17,93 13,600,39 19,27 11,200,49 20,72 8,620,14 0,35 17,260,20 0,38 14,910,31 0,41 12,060,45 0,42 10,12Table 4  The amount of retained austenite (vγ) as a function of strain intensity and diff erent strain rates on the surface of wires drawn with large partial draftsε ε⋅ /s-1 νγ /%0 0 23,950,39 80,64 6,650,72 96,09 4,940,36 16,71 10,980,64 19,91 6,240,30 0,36 11,950,59 0,43 8,02Based on the results given in Table 2÷5 and after making the approximating with a function of two vari-ables, relationships have been obtained, which deﬁ ne the amount of retained austenite as a function of ε and ε⋅ (Figures 2÷5).Table 5  The amount of retained austenite (νγ) as a function of strain intensity and diff erent strain rates in the axis of wires drawn with large partial draftsε ε⋅ /s-1 νγ /%0 0 23,950,35 80,64 9,140,65 96,09 5,060,30 16,71 12,040,54 19,91 7,410,24 0,36 13,060,43 0,43 9,14Figure 2  The plane representing the relationship between the retained austenite percentage fraction of the structure and strain intensity and strain rate on the surface of TRIP steel wires drawn with small partial draftsFigure 3  The plane representing the relationship between the retained austenite percentage fraction of the structure and strain intensity and strain rate in the axis of TRIP steel wires drawn with small partial draftsFigure 4  The plane representing the relationship between the retained austenite percentage fraction of the structure and strain intensity and strain rate on the surface of TRIP steel wires drawn with large partial drafts34  METALURGIJA 52 (2013) 1, 32-34S. WIEWIÓROWSKA et al.: ANALYSIS THE INFLUENCE OF DRAWING PROCESS PARAMETERS ON THE AMOUNT...CONCLUSIONSFigures 2÷5 show that, in the drawing process, strain intensity has a deﬁ nite effect on the amount of trans-formed retained austenite in the wire structure. By ex-amining the data in Figures 2 and 4, a small effect of strain rate on the decrease in the amount of transformed retained austenite in the wire sub-surface layer and its virtually insigniﬁ cant effect in the wire axis can be found. This is probably caused not so much by the ac-tion of strain rate (whose difference between the wire surface and axis is small) as by the larger non-dilata-tional strain occurring at a higher strain rate.The acceleration of the transformation of retained austenite into martensite in the drawing process is pre-dominantly inﬂ uenced by the magnitude of partial drafts.REFERENCES[1]  Łuksza J., Skołyszewski A., Witek F., Zachariasz W. – Druty ze stali i stopów specjalnych. Wydawnictwa Nau-kowo-Techniczne. Warszawa (2006).[2]  Staub F., Steininger Z., Tkaczyk S.: Wpływ odkształcenia plastycznego na zimno realizowanego przez przeciąganie na strukturę i własności drutu ze stali OH17N4G8. Sym-pozjum ciągarskie, Włocławek, (1975), 24-26.[3]  De Cooman B.C: Structure-properties relationship in TRIP steels containing carbide-free bainite, Current Opinion in Solid State&Materials Science 8 (2004), 285-303.[4]  Wiewiórowska S. - Analiza teoretyczno-eksperymentalna procesów ciągnienia nowej generacji drutów ze stali TRIP. Series Monograﬁ e. Częstochowa 18 (2011).Note:  The professional translator for English language is Czesław Grochowina, Studio – Tekst, PolandFigure 5  The plane representing the relationship between the retained austenite percentage fraction of the structure and strain intensity and strain rate in the axis of TRIP steel wires drawn with large partial drafts

Analysis the influence of drawing process parameters on the amount of retained austenite in trip steel wires

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