Degree Of Cold Drawing Research Articles

Mechanical Properties as a Function of Zinc Content, Degree of Cold Drawing and Annealing Temperature in α-Brasses

Mechanical Properties as a Function of Zinc Content, Degree of Cold Drawing and Annealing Temperature in α-Brasses

Fracture Process Zone in Notched Samples of Cold Drawn Pearlitic Steels.

This paper deals with the influence of the manufacturing process on the microscopic fracture behaviour of axisymmetric notched specimens of pearlitic steels with different degrees of cold drawing. To this end, samples from different steps of the manufacturing chain were obtained, from the initial hot rolled material (not cold draw at all) to the final prestressing steel (heavily cold drawn). A detailed fractographic analysis was performed by using scanning electron microscopy and image analysis techniques, in order to define and measure the fracture process zone in each case (final aim of this paper). Results show that the microscopic fracture modes range from ductile micro-void coalescence to brittle cleavage, depending on the stress triaxiality generated in the vicinity of the notch tip. A special fibrous region was detected, which al-lows a definition of the fracture process zone as the central region of the fractured area in bluntly notched samples and the external ring (i.e., the notch tip) in sharply notched specimens.

Enhancement of the dimensional stability of poly(ethylene-2,6-naphthalene dicarboxylate) filament by multistep zone annealing spinning

Both good tensile properties and good resistance to thermal shrinkage are prerequisites for tire cord applications. For these purposes, poly(ethylene-2,6-naphthalene dicarboxylate) (PEN) filaments were prepared by multistep zone annealing (MSZA) spinning with a specially devised system. The melting temperature of the PEN filaments so obtained was slightly increased with an increasing total draw ratio. All the filaments exhibited a sharp melting peak around 270°C, but glass-transition behavior was barely visible via differential scanning calorimetry. Rheovibron experiments showed α relaxation in the vicinity of 175°C. Increasing the draw ratio above 4 did not increase the birefringence value much, but it did lead to increases in the tensile properties. The PEN filaments consisted exclusively of α-form crystals. The PEN filaments showed excellent resistance to thermal shrinkage, which was less than 1% even with heating to 140°C. In the MSZA spinning process, increasing the degree of hot drawing proved more effective than increasing the degree of cold drawing for obtaining PEN filaments with better dimensional stability at elevated temperatures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 916–922, 2002

Fracture Performance of Progressively Drawn Pearlitic Steel under Triaxial Stress States

We study fracture processes in specimens with axially symmetric notches made of prestressed steels with various degrees of cold drawing of the wire. For this purpose, we use steel samples drawn to the required degrees. The intensity of drawing or the level of strains (characterized by the yield limit) is used as the main parameter of the technological treatment of the material. In specimens with notches of various shapes, we analyze the role of triaxiality of stresses. Special attention is given to the behavior of the sensitivity of the wire to notches as a function of triaxiality of stresses and the yield limit. The changes caused by the anisotropy of strength formed as a result of cold drawing are studied on the microscopic level.

Development of two-phase stainless steel wire rope having excellent fatigue properties: Tamai, K. Kodama, M. and Yamaoka, Y. Wire J. Int. (February 1995) 28 (2), 232–236

This paper deals with the role of microstructure on the fatigue behaviour of pearlitic steels with different degrees of cold drawing. The analysis is focussed on the region II (Paris) of the fatigue behaviour, measuring the constants (C and m) for the different degrees of drawing. From the engineering point of view, the manufacturing process by cold drawing improves the fatigue behaviour of the steels, since the fatigue crack growth rate decreases as the strain hardening level in the material increases. In particular, the coefficient m (slope of the Paris laws) remains almost constant and independent of the drawing degree, whereas the constant C decreases as the drawing degree rises. The paper focuses on the relationship between the pearlitic microstructure of the steels (progressively oriented as a consequence of the manufacturing process by cold drawing) and the macroscopic fatigue behaviour. To this end, a detailed metallographic analysis was performed on the fatigue crack propagation path after cutting and polishing on a plane perpendicular to the crack front (fracto-metallographic analysis). It is seen that the fatigue crack growth path presents certain roughness at the microscopic level, such a roughness being related to the pearlitic colony boundaries more than to the ferrite/cementite lamellae interfaces. Fatigue cracks are transcollonial and exhibit a preference for fracturing pearlitic lamellae, with non-uniform crack opening displacement values, micro-discontinuities, branchings, bifurcations and frequent local deflections that create microstructural roughness. The net fatigue surface increases with cold drawing due to the higher angle of crack deflections. With regard to the influence of the R-ratio, an increase of such a stress ratio produces microcracking with a higher number of branchings for the same stress intensity range.

Mechanical Properties of Austenitic Stainless Steel Wire (2nd Report). Effect of C Content

Variation of mechanical properties due to cold drawing and subsequent annealing was studied. The materials used in this investigation were three kinds of austenitic stainless steels, containing about 10% nickel and 0.03, 0.06, 0.08% carbon respectively. The following conclusions may be drawn from the experimental results. (1) The following empirical equations describe the relationships among the Vickers hardness (Hv), the tensile strength (σB·kg/mm2) and the yield point (0.2% set) (σy0.2·kg/mm2).(This article is not displayable. Please see full text pdf.) (2) The proportional limit of cold drawn wires is very low in spite of their high Hv and σB,and independent of both the degree of cold drawing ranging from 20 to 90% reduction of area and the carbon content ranging from 0.03 to 0.08% in weight. (3) Annealing after cold drawing is very effective for increasing the proportional limit. For example, the proportional limit is about 15 kg/mm2 when they are cold drawn, and about 50 kg/mm2 when they are annealed for 1/2 hr at 400° after cold drawing. The proportional limit of stainless steel wire,cold drawn and subsequently annealed,is also independent of both the degree of cold drawing ranging from 20 to 90% reduction of area and the carbon content ranging from 0.03 to 0.08% in weight.

New Spring Formulas and New Materials for Precision Spring Scales

Abstract This paper describes development work on springs for precision measuring instruments in which the various errors or deviations from desired behavior of the springs were studied separately. These errors were then compensated for by the design of a new-type helical spring, the combined error of which was reduced to well within 0.05 per cent. Variations due to change in elastic modulus with changes in temperature were eliminated essentially by the development of a special alloy of a modified elinvar type containing 36 per cent nickel; 8 per cent or more chromium; 4 per cent of other elements including manganese, silicon, molybdenum, copper, and vanadium; and the remainder iron. By making use of a high degree of cold drawing followed by a moderate-temperature heat-treatment and by other special processing, safe working stresses were raised to 60,000 lb per sq in. in shear, while the error due to creep under working loads was reduced to less than 0.02 per cent and the error due to “back error” or hysteresis was reduced to less than 0.04 per cent. Due to changes in pitch angle of wire and in radius of the coil as the load is applied, the load-deflection curve for a truly elastic helical spring of round wire deviates slightly from a straight line. Accurate formulas for the curve are developed in the paper. Using wires with the proper rectangular cross section, the resulting helical springs will theoretically have an exact straight-line rate. Actual behavior of these springs approximates very closely their theoretical behavior. An error results from the twisting of the springs under load. This has been corrected by using two springs in series, oppositely wound. Various other means of compensating for the various errors were also studied, some of which are mentioned in the paper.