The effect of wire rods quality on mechanical properties of drawn wires.

Liskova, Jana ; Tittel, Viktor ; Zelenay, Miroslav 等

1. INTRODUCTION

Mechanical properties of cold drawn wires are influenced by all mechanical properties of wire rods above all and by technological conditions of cold drawing. Not only the diameter of wire, but also the mechanical properties of wires are changing during the drawing process because there is an increase of strength properties and a decrease of plastic properties. Therefore, every change of input material WR will evoke the need of availability attest of using technology, eventually its change (Tittel, 2006).

Main goal of the experiment was to verify WR availability from the new producer and compare the reached properties after drawing to standard reached values from current used material. These wires were produced from WR quality C76D from producer A and are suitable in the present.

2. ACTUAL PRODUCTION TECHNOLOGY

Technology of drawn wires production is following (Liskova, 2007):

* Pickling of WR in HCl by two sinks. Goal of pickling is to eliminate the oxides, which are created by rolling process, from WR

* Phosphating and boraxing. Goal of this surface treatment is to create an appropriate layer on wire surface which serves as lubricant carrier. This layer also protects wire against corrosion for a short term (few days).

* Drawing from [empty set] 5.5 mm to [empty set] 2.8 mm. This (first) drawing process from [empty set] 5.5 mm to [empty set] 2.8 mm, consists of six passes. Total reduction by first drawing process is 74.09 %. Drawing speed was 7 [m.s.sup.-1]. Drawing was performed on the accumulation drawing wire machine.

* Patenting with using austenitisation process and cooling in lead bath for acquirement necessary composition applicable to drawing.

* Surfacing--continuous phosphating and boraxing.

* Drawing from [empty set] 2.8 mm to [empty set] 0.83 mm. This (second) drawing process consists of 11 passes and total reduction is 91.21%. Drawing speed was 12 [m.s-.sup.1]. Drawing was performed on the straight-drawing wire machine. Values of partial and total reductions are put in table No.1.

[[epsilon].sub.d] = [d.sup.2.sub.0] - [d.sup.2.sub.1]/[d.sup.2.sub.0] x 100 [%] (1)

[[epsilon].sub.c] = [D.sup.2.sub.0] - [d.sup.2.sub.n]/[D.sup.2.sub.0] x 100 [%] (2)

[d.sub.0]--input diameter of wire before die, [d.sub.1]--output diameter of wire after die, [D.sub.0]--begginig diameter of wire, [d.sub.n]--finishing diameter of wire (Baca & Bilik, 2000)

3. DESCRIPTION OF THE EXPERIMENT

We tried to find out the parameters differences of drawn wires which were produced from two sorts of WR in our experiment. We found out that the mechanical properties, chemical composition and also metallography were very similar without much difference. Also the quantity of processing was about the same.

There was retained production technology such as by WR from producer A by experiment of checking another WR. Experiment consisted in exact evaluation of tensile strength after drawing process, patenting and the following--second drawing process and also in more detail evaluation of mechanical properties, which were not required by a customer, such as: values of bends, values of torsion and elongation after drawing so that it is possible to confirm not only the availability of this material for producing but also the comparison of both WR sorts in whole technological process. We also followed the values of worn dies and occurrence of wire breakages which gave a vision about way- and conditions- of drawing. Request on drawn wires is according to EN STN 10204.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Formula of wire strengthening (polynomial of 3. level):

[R.sub.m] = 0,0043[[epsilon].sub.c.sup.3] - 0,4469[[epsilon].sub.c.sup.2] + 17,192[[epsilon].sub.c] + 1216,4 [R.sup.2] = 0,9936 (3)

4. MEASURING DATA VALUATION

Tensile strength of wire. By measuring there was detected, that required values [R.sub.m] = (2 160 - 2 360) MPa were fulfilled in both of materials acc. to specification. Material A had the average value 2 314 MPa and material B 2 279 MPa. The variation of tensile strength was greater by material B. It follows that values of tensile strength are better than by material A, however, both are completely suitable. By reason of obtaining tensile strength is not necessary to change the technology (diameter of half product, number of passes, material change, or patenting change). Fig. 1 was made by help of the program SPC- PC IV, which is a statistical program for appraisal of capability process. Limit value of Cpk is 1 (Zelenay, 2006). Cpk for material A was 0.9 and for B 1.13. It follows that material B is more capable. Elongation. Acquired average values of elongation by final wire for material A were 4.81% and 4.69% for material B. It follows, that plasticity ratio by both of materials is almost the same, however, material A shows better plasticity. Values of torsions. Average value for material A is 39.1 and 37.7 for material B. Following result is that material A is better. Values of bends. The wire was tested by bending with angle 90[degrees]. Average value for material A is 17.9 and for material B it is 17.7. Both of materials reached almost the same results. Treatment of compatibility. There is a regression curve on fig. 2. It follows that the total reduction and tensile strength are statistically interdependent.

5. CONCLUSION

Results were acquired by processing of both wires rod sorts, while time between material A and material B processing was only 10 days. For comparison, there were 49 tons of wires rod used and consisted of 25 tons from material A and 24 ton from material B, which is sufficient value for attest and arbitration. Based on found results we can say that the results of material A were better than the results of material B in general. On experiment were used two sorts of WR quality C76D but each wire was from another melt.

Following determined values, tensile strength of wire and values, which were made for plasticity of material check, we can state that both materials are suitable to fulfill the requirements which are given for this specification of high-strength drawn product.

In addition, the determined values or the pass of consolidation or values on final wire can serve to appraisal of these materials availability to produce other products-wire spring and ropes.

6. REFERENCES

Baca, J. & Bilik, J. (2000) Technology of forming. STU, Trnava

Enghang, P. (2004). Steel wire technology. Repro Orebro University, Sweden

Liskova, J. (2007). Influence of wire rods quality on mechanical properties of drawn wires. Graduation theses. MTF STU, Trnava

Tittel, V. (1992). Wire forming from non-standard steels.. Academic dissertation thesis. MTF STU, Trnava

Tittel, V. (2006). Material for production of steel ropes. In: Steel ropes. TU, ISBN 80-8073-639-4, Kosice

Zelenay, M. (2006). Tools for drawing of steelcoord wires. Graduation theses. MTF STU, Trnava

Tab.1. Measuring values by second drawing on straight-
drawing wire machine from [empty set] 2.8 mm to [empty set] 0.83 mm

Nr. Diameter Partial Total Real tensile
 of of die reduction reduction strength
draw [mm] [[epsilon] [[epsilon] [MPa]
 .sub.d][%] .sub.c][%]

 1 2.48 21.55 21.55 1 401.8
 2 2.20 21.31 38.26 1 443.3
 3 1.96 20.63 51.00 1 524.1
 4 1.75 20.28 60.93 1 612.9
 5 1.56 20.54 68.96 1 691.1
 6 1.39 20.61 75.36 1 774.5
 7 1.25 19.13 80.07 1 885.5
 8 1.12 19.72 84.00 1 998.3
 9 1.01 18.68 86.99 2 138.9
 10 0.91 18.82 89.44 2 274.1
 11 0.83 16.81 91.21 2 329.9

Tab. 2. Measuring values of the number of bends, torsions and
elongation on wire [empty set] 0.83 mm

 Material A
 No.
 of Values Values of Elongation
 test of bend torsion [%]

 1 18 33 4.8
 2 16 38 4.9
 3 20 35 5.1
 4 23 45 4.7
 5 18 38 5.1
 6 16 45 4.1
 7 17 36 5.0
 8 18 36 4.9
 9 17 43 4.6
 10 16 42 4.9
 Min. 16 33 4.7
 Max. 23 45 5.1
Average 17.9 39.1 4.81

 Material B
 No.
 of Values of Values of Elongation
 test bend torsion [%]

 1 17 43 4,6
 2 18 33 4,9
 3 14 38 4,8
 4 16 38 5,0
 5 19 32 4,4
 6 21 35 4,4
 7 17 35 4,4
 8 16 42 4,9
 9 21 41 4,5
 10 18 40 5,0
 Min. 16 32 4,1
 Max. 21 43 5,0
Average 17.7 37.7 4.69