Si killed steel wire material having excellent fatigue property and spring

A silicon-killed steel, fatigue-resistant technology, applied in the direction of metal rolling, can solve the problems of fatigue strength, difficulty, inability to make full use of various component differences and compounding, etc., to promote the miniaturization of inclusions and fatigue resistance characteristics excellent effect

Inactive Publication Date: 2009-10-07
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0017] However, it is not possible to meet the demand for higher fatigue resistance characteristics in the future only by using existing methods
In addition, in order to further promote deformation, the melting point of inclusions must be lowered, and there are currently a large number of announced SiO 2 -Al 2 o 3 -CaO-MgO-MnO and other systems, even if a significantly lower melting point is pursued, it is difficult to achieve a level higher than this
[0018] In addition, in the above-mentioned Patent Document 3, although the utilization of Ba, Sr, Ca, Mg, etc. is mentioned, it only focuses on the effect of lowering the melting point, and cannot make full use of the difference and the effect of compounding of various components. As a result, Can only become a technology that cannot achieve the fatigue strength that can withstand the current high demand

Method used

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  • Si killed steel wire material having excellent fatigue property and spring
  • Si killed steel wire material having excellent fatigue property and spring
  • Si killed steel wire material having excellent fatigue property and spring

Examples

Experimental program
Comparison scheme
Effect test

no. 1 approach

[0044] It is known that a wire rod having a large deformation ratio during hot rolling is useful because inclusions are stretched and split during hot rolling to make them finer. Under such circumstances, the present inventors considered the changes in the shape of inclusions caused by heating and hot rolling after solidification, and selected the composition and shape of each inclusion for improving the fatigue resistance of the spring from various research angle. As a result, it was found that by appropriately controlling the concentrations of Sr, Al, Si, Mg, and Ca, the deformation of oxide-based inclusions during hot rolling is significantly promoted and easily miniaturized.

[0045] It has also been known that the addition of small amounts of alkaline earth metal elements such as Sr, Mg, and Ca is effective for improving the characteristics of springs (for example, the aforementioned Patent Document 3), but it has been found that it is not necessary to add only a small am...

no. 2 approach

[0060]Based on the research results of the present inventors, it has also been found that if SrO, Al 2 o 3 , SiO 2 , MgO, CaO, and MnO concentrations, and if the ratio of each oxide component in the oxide-based inclusions is appropriate, the deformation of the oxide-based inclusions during hot rolling will be significantly promoted and the micronization will be facilitated.

[0061] Conventionally, it has also been known that appropriate ratios of oxides in the oxide-based inclusion system are effective in improving the properties of steel (for example, the aforementioned Patent Documents 1 to 3, 5 to 7), but the fatigue strength is not necessarily good. When these elements are contained in a balanced manner, it has been found that the fatigue resistance of the silicon-killed steel wire rod is significantly improved. For example, CaO-Al 2 o 3 -SiO 2 Three-component system inclusions, in the generally known ternary system phase diagram, although it can be seen that there i...

Embodiment 1

[0085] Experiments are implemented on a real machine (or laboratory level). That is, the actual machine is to tap the molten steel smelted in the converter into the ladle (the laboratory is to smelt 500kg of molten steel, which simulates the molten steel tapped from the converter), add various additives to adjust the composition, and implement Electrode heating and argon bubbling are performed to perform molten steel treatment (slag refining). In addition, after adjusting other components, Ca, Mg, Ce, Ba, Li, etc. were added as necessary during the molten steel treatment, and kept for 5 minutes or more. The obtained steel ingot was forged and hot-rolled to obtain a wire rod having a diameter of 8.0 mm.

[0086] For each of the obtained steel wire rods, the contents of Sr and Li in the steel were measured by the following method, and an evaluation test simulating a rotational bending fatigue test of a valve spring was performed.

[0087] (Contents of Sr and Li in steel)

[0...

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Abstract

Disclosed is a Si killed steel wire material for producing a spring having an excellent fatigue property. Also disclosed is a spring having an excellent fatigue property, which is produced from the steel wire material. The Si killed wire material comprises 0.03 to 20 ppm (''ppm'' means ''ppm by mass'', hereinbelow) of Sr, 1 to 30 ppm of Al and 0.2 to 4% (''%'' means ''% by mass'', hereinbelow) of Si, and additionally comprises Mg and/or Ca in a total amount of 0.5 to 30 ppm. The Si killed wire material contains an oxide inclusion comprising 30 to 90% of SiO2, 2 to 50% of Al2O3, 35% or less (more than 0%) of MgO, 50% or less (more than 0%) of CaO, 20% or less (more than 0%) of MnO and 0.2 to 15% of SrO, wherein the total content of CaO and MgO is 3% or more. A spring formed from the steel wire material has an excellent fatigue property.

Description

technical field [0001] The present invention relates to a silicon-killed steel wire excellent in fatigue resistance and a spring obtained from the steel wire, which can exhibit high fatigue resistance when used as a high-strength spring (especially a valve spring), etc. It is useful to use raw materials such as engine valve springs, clutch springs, brake springs, suspension springs, and steel cords. Background technique [0002] Recently, as the demand for weight reduction and higher output of automobiles has increased, even valve springs and suspension springs used in engines and suspensions have been directed to high-stress designs. Therefore, among these springs, it is strongly desired that they are excellent in fatigue resistance and damping resistance in order to cope with an increase in load stress. In particular, there is a strong demand for increased fatigue strength of valve springs, and it is difficult to meet SWOSC-V (JIS G 3566), which is considered to be excell...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00B21B3/00C22C38/06C22C38/58C21C7/00C21C7/04
Inventor 杉村朋子坂本浩一
Owner KOBE STEEL LTD
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