WO2018106016A1 - Fil machine pour ressorts à excellente résistance à la fatigue par corrosion, fil d'acier et son procédé de fabrication - Google Patents

Fil machine pour ressorts à excellente résistance à la fatigue par corrosion, fil d'acier et son procédé de fabrication Download PDF

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WO2018106016A1
WO2018106016A1 PCT/KR2017/014232 KR2017014232W WO2018106016A1 WO 2018106016 A1 WO2018106016 A1 WO 2018106016A1 KR 2017014232 W KR2017014232 W KR 2017014232W WO 2018106016 A1 WO2018106016 A1 WO 2018106016A1
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corrosion
wire
less
steel wire
resistance
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PCT/KR2017/014232
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Korean (ko)
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김관호
김한휘
정회영
이병갑
전영수
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주식회사 포스코
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Priority to EP17877467.5A priority Critical patent/EP3553198A4/fr
Priority to CN201780075012.2A priority patent/CN110036131B/zh
Priority to JP2019526575A priority patent/JP7018444B2/ja
Priority to US16/466,984 priority patent/US20200063228A1/en
Publication of WO2018106016A1 publication Critical patent/WO2018106016A1/fr

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    • C—CHEMISTRY; METALLURGY
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • C—CHEMISTRY; METALLURGY
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    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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    • C21D9/02—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for springs
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/573—Continuous furnaces for strip or wire with cooling
    • C21D9/5732—Continuous furnaces for strip or wire with cooling of wires; of rods
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Definitions

  • the present invention relates to a high-strength, corrosion-resistant wire rod, steel wire and a manufacturing method thereof that can be preferably applied to suspension springs, torsion bars, stabilizers and the like for automobiles.
  • the steel for spring is made of hot wire by hot rolling, and in the case of hot forming spring, it is heated and then molded and then quenched and tempered. In the case of cold formed spring, after tempering, quenched and tempered Molding
  • Suspension corrosion of suspension spring is when the surface of the spring is peeled off by gravel or other foreign material on the road surface, the material of this part is exposed to the outside, causing pitting corrosion reaction, and the generated corrosion pit grows gradually and starts the pit.
  • the cracks are generated and propagated, and at some point, hydrogen introduced from the outside concentrates on the cracks, and the spring is broken due to hydrogen embrittlement.
  • Patent Document 1 Conventional techniques for improving the resistance to corrosion fatigue of the spring include a method of increasing the type and amount of alloying elements.
  • the Ni content was increased to 0.55% by weight to increase corrosion fatigue life by improving corrosion resistance
  • Patent Document 2 the Si content was increased to refine corrosion carbide by tempering carbide precipitated during tempering. Improved strength.
  • Patent Document 3 was able to improve the life of the spring corrosion fatigue by improving the hydrogen delayed fracture resistance by appropriate combination of Ti precipitates, which are strong hydrogen trapping sites, and (V, Nb, Zr, Hf), which are weak hydrogen trapping sites.
  • Ni is a very expensive element, and when a large amount is added, it causes a problem of material cost increase.
  • Si is a representative element that promotes decarburization, and it may cause a considerable risk in increasing the amount of addition, and precipitates such as Ti, V, and Nb Forming elements are at risk of degrading the life of corrosion fatigue by crystallizing coarse carbonitride from the liquid phase during material solidification.
  • the prior art for increasing the strength of the spring is a method of adding an alloying element and a method of lowering the tempering temperature.
  • a method of increasing the strength by adding alloying elements there is basically a method of increasing the quenching hardness using C, Si, Mn, Cr, etc., and quenching using expensive alloying elements Mo, Ni, V, Ti, Nb, etc.
  • the strength of steel materials is raised by tempering heat treatment.
  • such a technique has a problem of rising cost.
  • Patent Document 1 Japanese Unexamined Patent Publication No. 2008-190042
  • Patent Document 2 Japanese Unexamined Patent Publication No. 2011-074431
  • Patent Document 3 Japanese Unexamined Patent Publication No. 2005-023404
  • One aspect of the present invention is to control the combination of Cr, Cu, Ni content to an appropriate level, the maximum depth of the corrosion pit to a certain level or less, high-strength and corrosion-resistant fatigue resistance by a certain level of fine carbide containing Mo To provide this excellent spring wire rod, steel wire and their manufacturing method.
  • One aspect of the invention is by weight, C: 0.40-0.70%, Si: 1.30-2.30%, Mn: 0.20-0.80%, Cr: 0.20-0.80%, Cu: 0.01-0.40%, Ni: 0.10-0.60% %, Mo: 0.01-0.40%, P: 0.02% or less, S: 0.015% or less, N: 0.01% or less, remaining Fe and other unavoidable impurities, satisfying the following relational formula 1,
  • the microstructure is composed of up to 50 area% ferrite and the remaining pearlite,
  • the present invention relates to a spring wire rod having excellent corrosion fatigue resistance including Mo-based carbides of 8.0 ⁇ 10 4 particles / mm 2 or more.
  • Another aspect of the present invention is by weight, C: 0.40 to 0.70%, Si: 1.30 to 2.30%, Mn: 0.20 to 0.80%, Cr: 0.20 to 0.80%, Cu: 0.01 to 0.40%, Ni: 0.10 to 0.60%, Mo: 0.01-0.40%, P: 0.02% or less, S: 0.015% or less, N: 0.01% or less, remaining Fe and other unavoidable impurities, and the billets satisfying the following relation 1, 900 ⁇ 1100 °C Heating to;
  • the cooling time so that the holding time in the temperature range of 600 ⁇ 700 °C 31 seconds or more; relates to a method for producing a wire rod for excellent corrosion resistance comprising a.
  • each element symbol is a value representing each element content in weight%.
  • another aspect of the present invention relates to a steel wire manufactured using the wire and the method of manufacturing the same.
  • 1 is a graph showing the relative corrosion fatigue life according to the maximum depth of corrosion pit of embodiments of the present invention.
  • Figure 2 is a graph showing the relative corrosion fatigue life according to the number of Mo-based carbide of the embodiments of the present invention.
  • the present inventors examine various influence factors on the corrosion resistance of the steel for spring, and at the same time, the corrosion fatigue of the spring is generated by the peeling of the surface of the spring, and the corrosion pits are generated.
  • the following findings were obtained from the fact that the cracks are generated and propagated to the starting point, and hydrogen introduced from the outside is concentrated in the cracks and the springs are broken.
  • the corrosion resistance of the spring steel decreases as the maximum depth of the corrosion pit formed on the surface of the material during the corrosion reaction.
  • the narrower the shape and the deeper the corrosion pit the lower the corrosion fatigue characteristics. Therefore, it is necessary to control the maximum depth of the corrosion pit below a certain level in order to improve the corrosion resistance of the spring steel.
  • the fine carbides that can be utilized are not cementite but V, Ti, Nb, Mo. It is a carbide mainly containing alloying elements, such as these. Particularly, Mo-based carbides precipitate very finely at a temperature of 700 ° C. or below in nano size, and have a great hydrogen trap effect. Carbides including V, Ti, Nb, etc. as well as Mo also have a hydrogen trap effect when they contain Mo. outstanding.
  • the combination of Cr, Cu, and Ni content is controlled to an appropriate level, the maximum depth of the corrosion pit is below a certain level, and the fine carbide containing Mo is above a certain level, thereby providing high strength and corrosion resistance. It was confirmed that the wire rod, the steel wire, and their manufacturing method can be provided, and the present invention has been completed.
  • the microstructure is composed of ferrite of 50 area% or less and the remaining pearlite, and contains Mo-based carbide of 8.0 ⁇ 10 4 / mm 2 or more.
  • alloy composition of the present invention will be described in detail.
  • the unit of each element content hereafter means weight% unless there is particular notice.
  • alloy composition of the present invention is equally applied to the production method of the wire rod, steel wire and steel wire production method to be described below.
  • C is an essential element added to secure the strength of the spring. In order to exhibit the effect effectively, it is preferable to contain 0.40% or more. On the other hand, if the C content is more than 0.70%, the twin type martensite structure is formed during quenching and tempering heat treatment, resulting in material cracking. However, the fracture stress can be significantly reduced. Therefore, it is preferable that C content is 0.40 to 0.70%.
  • the lower limit of the C content may be more preferably 0.45%, and the upper limit may be 0.65%.
  • Si is dissolved in ferrite and has the effect of strengthening the base material strength and improving the deformation resistance.
  • the lower limit of Si is preferably 1.30%, and the lower limit may be 1.45% because Si is insufficiently effective in solidifying the ferrite to strengthen the base material strength and improving the deformation resistance.
  • the Si content is more than 2.30%, the effect of improving the deformation resistance is saturated, and the effect of additional addition is not obtained, and the surface decarburization is promoted during the heat treatment. Therefore, it is preferable that the upper limit of Si is 2.30%, and a more preferable upper limit may be 2.25%.
  • Mn is an element useful for securing strength by improving the hardenability of steel when present in steel.
  • the Mn content is less than 0.20%, it is difficult to obtain sufficient strength and hardenability required as a material for high strength springs. On the contrary, if the Mn content is higher than 0.80%, the hardenability is excessively increased and martensite hard tissues are likely to occur during cooling after hot rolling. In addition, the formation of MnS inclusions increases, rather there is a fear that the corrosion resistance fatigue resistance. Therefore, the Mn content is preferably 0.20 to 0.80%.
  • the lower limit of the Mn content may be 0.30%, more preferably 0.40%.
  • the more preferred upper limit of the Mn content may be 0.75%, and the more preferable upper limit may be 0.70%.
  • Cr is an element useful for securing oxidation resistance, temper softening, surface decarburization prevention and quenching.
  • the Cr content is less than 0.20%, it is difficult to secure sufficient oxidation resistance, temper softening, surface decarburization and quenching effects. On the other hand, when the Cr content is more than 0.80%, the deformation resistance may be lowered, which may lead to a decrease in strength. Therefore, the Cr content is preferably 0.20 to 0.80%.
  • the lower limit of the Cr content may be 0.22%, and the upper limit may be 0.75%.
  • Copper (Cu) is an element added to improve the corrosion resistance. If the content is less than 0.01%, the effect of improving the corrosion resistance is insufficient, whereas if it is more than 0.40%, the brittleness during hot rolling causes a problem such as cracking. May cause Therefore, the Cu content is preferably 0.01 to 0.40%. More preferably, the Cu content may be 0.05 to 0.30%.
  • Nickel (Ni) is an element added to improve the hardenability and toughness. If the content is less than 0.10%, the effect of the hardenability and toughness is not sufficient, whereas if the content is higher than 0.60%, the amount of retained austenite This increases the fatigue life, and the expensive Ni properties cause a sharp rise in manufacturing costs. Therefore, the Ni content is preferably 0.10 to 0.60%.
  • Mo is an element which forms carbon or nitrogen and carbonitrides, contributes to the refinement of the structure, and acts as a trap site for hydrogen, and in order to effectively exhibit such an effect
  • the content is preferably 0.01% or more.
  • the Mo content is excessive, the martensite hard structure is likely to occur during hot rolling after cooling, and the upper limit of the Mo content is preferably 0.40% because coarse carbonitride is formed and the ductility of the steel is reduced.
  • P is an impurity, and it is preferable to limit the upper limit to 0.02% because of a problem of segregation at grain boundaries and deterioration of toughness.
  • S is an impurity, and it is preferable to limit the upper limit to 0.015% because it not only lowers the toughness by grain boundary segregation with low melting elements but also forms a large amount of MnS, which adversely affects the corrosion resistance of the spring.
  • Nitrogen (N) is easy to form BN by reacting with boron (B), and should be controlled as low as possible because it is an element that reduces the quenching effect, but considering the process load, it is preferable to limit it to 0.01% or less.
  • the remaining component of the present invention is iron (Fe).
  • impurities which are not intended from the raw material or the surrounding environment may be inevitably mixed, and thus cannot be excluded. Since these impurities are known to those skilled in the art, all of them are not specifically mentioned in the present specification.
  • each element symbol is a value representing each element content in weight%.
  • Cr is generally known as a corrosion resistance improving element, but corrosion resistance decreases with increasing Cr content in spring steel. This is because Cr lowers the pH of the pit base (bottom) during the corrosion reaction, making the inside of the pit a strong acid atmosphere, thereby increasing the maximum depth of the pit. That is, Cr plays a role of lowering corrosion resistance as the content increases.
  • alloy composition described above it may further include at least one selected from V: 0.01 to 0.20%, Ti: 0.01 to 0.15%, and Nb: 0.01 to 0.10% by weight.
  • V is not only an element that contributes to strength improvement and grain refinement, but also forms a carbon nitride with carbon (C) or nitrogen (N) and acts as a trap site for hydrogen infiltrating into steel, thereby inhibiting hydrogen intrusion inside steel materials. It is an element that serves to reduce the occurrence of corrosion.
  • the upper limit of the V content is preferably 0.20%.
  • Ti is an element that improves the spring characteristics by forming a carbonitride to cause precipitation hardening, and improves strength and toughness through particle refinement and precipitation strengthening. In addition, Ti acts as a trap site for hydrogen infiltrating into steel, thereby inhibiting hydrogen ingress and reducing corrosion.
  • the Ti content is less than 0.01%, the precipitation reinforcement and the frequency of precipitates acting as hydrogen trapsites are not effective. If the Ti content is more than 0.15%, the manufacturing cost increases rapidly, and the effect of improving the spring properties by the precipitates is saturated and austenite Coarse alloy carbides that are not dissolved in the base material during heat treatment are increased to act as non-metallic inclusions, thereby reducing fatigue characteristics and precipitation strengthening effects.
  • the amount of addition is preferably 0.01% or more in order to effectively exhibit the effect.
  • the upper limit of the added amount is preferably 0.10%.
  • the microstructure of the wire rod according to the present invention consists of ferrite of 50 area% or less and the remaining pearlite.
  • the area fraction here means the measurement except for the precipitate.
  • the strength of the material is so low that the desired level of strength cannot be achieved after the final heat treatment.
  • the remainder except for ferrite is pearlite. If there are hard tissues such as martensite in addition to ferrite and pearlite, there is a possibility that the wire will be disconnected at the stage of wire drawing.
  • the wire rod according to the present invention contains Mo-based carbide at least 8.0 ⁇ 10 4 / mm 2.
  • the fine carbides that can be utilized are not cementite but V, Ti, Nb, Mo, etc.
  • Carbide is composed mainly of alloying elements.
  • carbides containing Mo as the main component are very finely precipitated at a nano size in the temperature range of 600 to 700 ° C., so that the hydrogen trap effect is very large, and carbides containing V, Ti, and Nb as the main component also contain Mo. Hydrogen trap effect is excellent.
  • the Mo-based carbide is preferably included 8.0 ⁇ 10 4 / mm 2 or more, more preferably 8.5 ⁇ 10 4 / mm 2 or more.
  • the Mo-based carbide may be a carbide containing 5% by weight or more based on the carbide.
  • carbides containing V, Ti, Nb, etc. as a main component also have an excellent hydrogen trap effect when they contain Mo.
  • Another aspect of the present invention provides a method for producing a spring wire rod excellent corrosion resistance step of heating a billet satisfying the above-described alloy composition to 900 ⁇ 1100 °C; Hot-rolling the heated billet to 800 to 1000 ° C. to obtain a wire rod; And after winding the wire rod, cooling the holding time in a temperature range of 600 to 700 ° C. to 31 seconds or more.
  • Billets satisfying the above-described alloy composition is heated to 900 ⁇ 1100 °C.
  • the heating temperature of the billet is above 900 ° C to dissolve all coarse carbides that may be produced during casting so that the alloying elements are uniformly distributed in the austenite.
  • the heating temperature of the billet is more than 1100 °C, it is heated more than necessary, the heat consumption is high, there is a fear that the decarburization becomes severe as the time is long.
  • the heated billet is hot rolled to finish at 800 to 1000 ° C. to obtain a wire rod.
  • the finishing rolling temperature is 800 ° C. or higher to promote precipitation of fine carbides. If the finish rolling temperature is less than 800 °C, the load of the rolling roll is large, when the finish rolling temperature is greater than 1000 °C grain size is large, toughness is lowered, the transformation is delayed during cooling, martensite hard structure may occur.
  • the wire After winding the wire, it is cooled so that the holding time in the temperature range of 600 to 700 ° C is 31 seconds or more.
  • Controlling the holding time in the temperature range of 600 to 700 ° C to be 31 seconds or more is to ensure sufficient time for the pearlite transformation to be completed without martensite hard structure being formed upon cooling. This is to allow the carbide to precipitate sufficiently.
  • the spring steel wire having excellent corrosion fatigue resistance satisfies the alloy composition described above, and the microstructure is a tempered martensite single phase and includes Mo-based carbide of 8.0 ⁇ 10 4 / mm 2 or more.
  • Corrosion fatigue resistance can be improved by making a microstructure a tempered martensite single phase and including Mo-type carbide 8.0 * 10 ⁇ 4> / mm ⁇ 2> or more.
  • Tempered martensite single phase means composed of tempered martensite except for some unavoidable impurities.
  • the fine carbides that can be utilized are not cementite but V, Ti, Nb, Mo, etc.
  • Carbide is composed mainly of alloying elements.
  • carbides containing Mo as the main component are very finely precipitated at a nano size in the temperature range of 600 to 700 ° C., so that the hydrogen trap effect is very large, and carbides containing V, Ti, and Nb as the main component also contain Mo. Hydrogen trap effect is excellent. Therefore, the Mo-based carbide is preferably included at least 8.0 ⁇ 10 4 / mm 2, more preferably 8.5 ⁇ 10 4 / mm 2 or more. On the other hand, Mo-based carbide is produced during the production of the wire rod, and does not significantly change even after heating and cooling according to steel wire manufacturing, but may be slightly reduced.
  • the steel wire of the present invention may have a maximum depth of the corrosion pit 120 ⁇ m or less.
  • the maximum depth measurement of the corrosion pit is put the test piece of the steel wire in the salt spray tester sprayed 5% brine for 4 hours in a 35 °C atmosphere, dried for 4 hours in a temperature 25 °C, 50% humidity, 40 °C atmosphere
  • the cycle of moistening for 16 hours to 100% humidity was repeated 14 cycles and then measured. This is to set the harshest conditions in consideration of the use environment of the spring steel, it can ensure excellent corrosion fatigue resistance when the maximum depth of the corrosion pit is 120 ⁇ m or less under these conditions.
  • the steel wire of the present invention may have a tensile strength of 1800 MPa or more.
  • Another aspect of the present invention is a method for producing a spring steel wire having excellent resistance to corrosion fatigue step of obtaining a steel wire by drawing a wire produced by the method for producing a wire according to the present invention; An austenitization step of maintaining the steel wire at 850 to 1000 ° C. for at least 1 minute; And tempering at 350-500 ° C. after cooling the austenitic wire at 25-80 ° C.
  • the holding time after heating is less than 1 minute, the ferrite and pearlite structures may not be sufficiently heated and may not be transformed into austenite, so the heating time is preferably 1 minute or more.
  • oil-cooling temperature is normal conditions, it does not specifically limit.
  • tempering temperature is less than 350 °C, the toughness is not secured, there is a risk of damage in the molding and product state, while if the temperature exceeds 500 °C tempering temperature is preferably 350 ⁇ 500 °C.
  • the billet having the composition shown in Table 1 was heated to 1000 °C and then rolled to finish rolling at 900 °C, the winding after cooling to maintain a temperature range of 600 ⁇ 700 °C during the holding time shown in Table 2 to prepare a wire rod. .
  • the microstructure of the wire rod was observed and listed in Table 2 below.
  • Tensile strength was measured by performing a tensile test after taking the tensile specimen in accordance with the ASTM E 8 standard.
  • Mo-based carbides were cross sectioned and then fine carbides were extracted by replica method and analyzed using Transmission Electron Microscope and Energy Dispersive X-ray Spectroscopy. Table 2 shows the number of carbides containing 5% or more.
  • the specimen was placed in a salt spray tester and sprayed with 5% brine for 4 hours in a 35 ° C atmosphere, dried for 4 hours in a temperature of 25 ° C and a humidity of 50%, and wetted for 16 hours to be 100% humidity in a 40 ° C atmosphere ( cycle) after 14 cycles. Corrosion pit maximum depth and relative corrosion fatigue life were measured.
  • Corrosion pit maximum depth was measured with a Confocal Laser Microscope.
  • the relative corrosion fatigue life was tested by rotational bending fatigue test, the fatigue test speed was 3,000rpm, and the load applied to the specimen was 40% of the tensile strength. The fatigue life was averaged to give the corrosion fatigue life of the specimen. Table 2 shows the relative corrosion fatigue life of the remaining specimens when the corrosion fatigue life of Comparative Example 1 is 1.
  • relation 1 represents a value of 0.70 [Cr]-0.76 [Cu]-0.24 [Ni].
  • F means ferrite
  • P means pearlite
  • M means martensite
  • the tensile strength of 1800 MPa or more can be secured in the comparative examples, it can be seen that the relative corrosion fatigue life is inferior because the alloy composition or the manufacturing conditions presented in the present invention are not satisfied.
  • the maximum depths of the corrosion pits were all 128 ⁇ m or more, and the number of Mo-based carbides was all observed to be less than 8 ⁇ 10 4 pieces / mm 2.
  • 1 is a graph showing the relative corrosion fatigue life according to the maximum depth of corrosion pit of embodiments of the present invention. The smaller the maximum depth of the corrosion pit, the greater the relative corrosion fatigue life. When the maximum depth of the corrosion pit was greater than 120 ⁇ m, the relative corrosion fatigue life was greatly reduced.
  • Figure 2 is a graph showing the relative corrosion fatigue life according to the number of Mo-based carbide of the embodiments of the present invention. The more the number of fatigue Mo system carbides is relatively corrosion life was increased significantly, 8.0 ⁇ 10 4 number / relative to the mm2 If the Mo-based carbide smaller than this decreased significantly relative corrosion fatigue life.

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  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Manufacturing & Machinery (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)

Abstract

Selon un aspect, la présente invention concerne une fil machine pour ressorts ayant une haute résistance et une excellente résistance à la fatigue par corrosion, dans laquelle une combinaison de teneur en Cr, Cu et Ni est contrôlée à un niveau approprié, la profondeur maximale des piqûres de corrosion est réglée de sorte à être inférieure à un certain niveau, et la teneur en carbures fins contenant du Mo est réglée de sorte à être supérieure ou égale à un certain niveau.
PCT/KR2017/014232 2016-12-06 2017-12-06 Fil machine pour ressorts à excellente résistance à la fatigue par corrosion, fil d'acier et son procédé de fabrication WO2018106016A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP17877467.5A EP3553198A4 (fr) 2016-12-06 2017-12-06 Fil machine pour ressorts à excellente résistance à la fatigue par corrosion, fil d'acier et son procédé de fabrication
CN201780075012.2A CN110036131B (zh) 2016-12-06 2017-12-06 具有优异耐腐蚀疲劳性能的弹簧用线材、钢丝及其制造方法
JP2019526575A JP7018444B2 (ja) 2016-12-06 2017-12-06 耐腐食疲労性に優れたばね用線材及び鋼線並びにそれらの製造方法
US16/466,984 US20200063228A1 (en) 2016-12-06 2017-12-06 Wire rod for springs with excellent corrosion fatigue resistance, steel wire, and manufacturing method thereof

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KR1020160165185A KR101867709B1 (ko) 2016-12-06 2016-12-06 부식피로 저항성이 우수한 스프링용 선재, 강선 및 그들의 제조방법
KR10-2016-0165185 2016-12-06

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JP7239729B2 (ja) * 2019-10-16 2023-03-14 日本製鉄株式会社 鋼線

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Publication number Priority date Publication date Assignee Title
CN109735771A (zh) * 2019-03-19 2019-05-10 马鞍山钢铁股份有限公司 一种具有优良疲劳性能和耐蚀性能的高强度弹簧用钢及其生产方法

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CN110036131A (zh) 2019-07-19
US20200063228A1 (en) 2020-02-27
EP3553198A1 (fr) 2019-10-16
JP2020509158A (ja) 2020-03-26
CN110036131B (zh) 2021-07-06
JP7018444B2 (ja) 2022-02-10
KR101867709B1 (ko) 2018-06-14

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