High tensile strength steel wire

Inactive Publication Date: 2016-08-18
NV BEKAERT SA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0039]Preferably, in the process said work hardening occurs at a temperature below 400° C. More preferably, said work hardening is cold drawing. Cold drawing has an added effect of work hardening and strengthening the material, and thus further improves the material's mechanical properties. It also improves the surface finish and

Problems solved by technology

For instance, extension springs operating above their tensile strength will break.
It has been found, nevertheless, that increasing mechanical strength beyond certain

Method used

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  • High tensile strength steel wire
  • High tensile strength steel wire
  • High tensile strength steel wire

Examples

Experimental program
Comparison scheme
Effect test

embodiment 1

[0049]FIG. 4 illustrates a suitable temperature versus time curve applied to a steel wire or wire rod with a diameter of 5.29 mm and with following steel composition:[0050]% wt C=0.55[0051]% wt Si=1.4[0052]% wt Cr=0.6[0053]% wt Mn=0.7

the balance being iron and unavoidable impurities.

[0054]The starting temperature of martensite transformation Ms of this steel is about 280° C. and the temperature Mf, at which martensite formation ends is about 100° C.

[0055]The various steps of the process are as follows:[0056]a first austenitizing step (10) during which the steel wire stays in a furnace at about 950° C. during 120 seconds,[0057]a second quenching step (12) for martensite transformation in oil at a temperature below 100° C. during at least 20 seconds;[0058]a third tempering step (14) for increase the toughness at a temperature above 320° C. during less than 60 seconds; and[0059]a fourth cooling step (16) at room temperature during 20 or more seconds.

[0060]Curve 18 is the temperature cu...

embodiment 2

[0067]In this embodiment, a similar thermal treatment of embodiment 1 was applied to a steel wire with a diameter of 3.75 mm and with the following steel composition:[0068]% wt C=0.55[0069]% wt Si=1.4[0070]% wt Cr=0.6[0071]% wt Mn=0.7

the balance being iron and unavoidable impurities.

[0072]The steel wire after thermal treatment mainly has martensitic microstructure. The steel wire further undergoes six passes drawing steps with a diameter reduction to 2.8 mm. The properties of the steel wire after each pass are shown in table 2. Although an extreme high tensile strength is obtained after six passes, the steel wire still has sufficient ductility as indicated by a reduction in area of 52.8%. Moreover, the ductility of the steel wire is ensured during the whole drawing process, which can be verified by the reductions in area of the steel wires after one to six passes all being above 52.8% as shown in table 2.

TABLE 2Properties of a steel wire with an initial diameter of 3.75 mmdrawn in s...

embodiment 3

[0073]Different from the samples of embodiment 2, in this example, after a similar thermal treatment, the martensitic steel wire with 3.75 mm diameter is drawn by three passes.

[0074]The diameter, diameter reduction, section reduction, cumulative section reduction, tensile strength, tensile strength variation and reduction in area after each pass of the steel wire drawn by this three passes process are summarized in table 3.

[0075]The average diameter reduction of each pass is about 9.5% for three passes process which is almost a double of that of six passes process as shown in embodiment 1 and 2. The tensile strength (Rm) of three passes drawn wire (SW3) as a function of section reduction (Δs) is plot in FIG. 6 in comparison with the tensile strength of six passes drawn wires of embodiment 1 (SW1) and embodiment 2 (SW2). As shown in FIG. 6, the increase of tensile strength is almost proportional to the increase of section reduction for both the three and the six passes drawn steel wi...

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Abstract

A high tensile strength steel wire having as steel composition: a carbon content ranging from 0.20 weight percent to 1.00 weight percent, e.g. from 0.3 weight percent to 0.85 weight percent, e.g. from 0.4 weight percent to 0.7 weight percent, e.g. from 0.5 weight percent to 0.6 weight percent, a silicon content ranging from 0.05 weight percent to 2.0 weight percent, e.g. from 0.2 weight percent to 1.8 weight percent, e.g. from 1.2 weight percent to 1.6 weight percent, a manganese content ranging from 0.40 weight percent to 1.0 weight percent, e.g. from 0.5 weight percent to 0.9 weight percent, a chromium content ranging from 0.0 weight percent to 1.0 weight percent, e.g. from 0.5 weight percent to 0.8 weight percent, a sulfur and phosphor content being individually limited to 0.05 weight percent, e.g. limited to 0.025 weight percent, contents of nickel, vanadium, aluminum, copper or other micro-alloying elements all being individually limited to 0.5 weight percent, e.g. limited to 0.2 weight percent, e.g. limited to 0.08 weight percent, the remainder being iron, said steel wire having martensitic structure, wherein at least 10 volume percent of martensite are oriented.

Description

TECHNICAL FIELD[0001]The present invention relates to a high tensile strength steel wire, to a process for manufacturing a high tensile strength steel wire and to the uses or applications of such a high tensile strength steel wire as spring wire or an element for producing a rope.BACKGROUND ART[0002]Springs are usually made from alloys of steel. The most common spring steels are music wire, oil tempered wire, chrome silicon, chrome vanadium, and 302 and 17-7 stainless. Spring wires made of chrome silicon or chrome vanadium are higher quality, higher strength versions of oil tempered wire.[0003]Spring steel used in applications such as automotive valve springs is in general required to have a very high tensile and yield strength. Tensile strength is a material's ability to resist forces that attempt to pull apart or stretch it. Tensile strength is an important property for wires for spring applications. For instance, extension springs operating above their tensile strength will break...

Claims

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Application Information

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IPC IPC(8): C21D9/02C22C38/02C22C38/18C22C38/04C21D9/52C21D8/06
CPCC21D8/06C21D8/065C21D9/02C21D9/52C22C38/00C22C38/18C21D2211/008B21C1/003C21D1/25C22C38/04C21D9/525C22C38/02C22C38/60
Inventor MESPLONT, CHRISTOPHE
Owner NV BEKAERT SA
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