CN111910134B - High-strength high-toughness spring steel used under high-temperature and high-pressure conditions and production method thereof - Google Patents
High-strength high-toughness spring steel used under high-temperature and high-pressure conditions and production method thereof Download PDFInfo
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Abstract
The invention discloses high-strength high-toughness spring steel used under high-temperature and high-pressure conditions and a production method thereof, and belongs to the technical field of metal smelting. The spring steel comprises the following components in percentage by weight: 0.30 to 0.50 percent of C, 1.30 to 1.80 percent of Si, 0.80 to 1.00 percent of Mn, 0.10 to 0.30 percent of Cr, 0.10 to 0.30 percent of V, 0.020 to 0.040 percent of Nb, 0.10 to 0.30 percent of Mo, 0.60 to 1.20 percent of W, 0.015 percent of trace of P, 0.010 percent of trace of S and the balance of Fe and impurities. The chemical composition ratio satisfies that Meq ═ C- (0.10[ Cr ] +0.20[ V ] +0.03[ Nb ] +0.05[ W ] +0.08[ Mo ]). The steel has good heat resistance, and meets the use requirement of the spring under the high-temperature condition.
Description
Technical Field
The invention relates to the technical field of metal smelting, in particular to high-strength high-toughness spring steel used under high-temperature and high-pressure conditions and a production method thereof.
Background
The spring is widely used in various industries and plays an important role in the stability and safety of automobiles, airplanes and machinery, so that the requirement on the performance of the spring steel is extremely high. High strength, high elongation, high reduction of area and high fatigue resistance are trends in the development of spring steels in the future.
Moreover, the demand for heat-resistant spring steel which can simultaneously bear high-temperature and high-pressure special use conditions is increasing, and the demand is also increasing. Therefore, the research and development of the heat-resistant high-strength high-toughness spring steel are beneficial to improving the self-supporting capacity of high-end equipment parts in China and improving the current situation that high-grade spring steel still needs to be imported in China. The conventional method for improving the strength of the spring steel can improve the strength of the spring steel, but can cause the toughness of the spring steel to be reduced. The spring steel in special environments such as aviation and boiler industries not only needs high-temperature strength, but also needs to ensure toughness to meet requirements.
With the rapid development of the aviation industry, the requirements of high-strength high-toughness spring steel materials with heat resistance are more and more urgent, but the related reports of the heat-resistant high-strength high-toughness spring steel products are less, and the products and the achievements are almost blank.
Through retrieval, Chinese patent CN107747060A, publication date is: 3.2.2018, discloses a production method of a high-strength and high-fatigue life spring steel, which comprises the following chemical components in percentage by weight of 0.51-0.59% of carbon, 1.40-1.60% of silicon, 0.50-0.80% of manganese, less than or equal to 0.012% of phosphorus, less than or equal to 0.010% of sulfur, less than or equal to 0.02% of niobium, less than or equal to 0.005% of titanium, less than or equal to 0.005% of aluminum, 0.50-0.80% of chromium, and the balance of Fe and inevitable impurities. By adopting a series of new smelting and rolling technologies of high alloying component design, LF + VD composite refining, casting blank flaw detection and coping, stelmor controlled rolling and cooling and the like, the high-strength and high-fatigue-life wire spring steel with a sorbite structure as a matrix is produced, but the spring steel has lower strength which is only 1000MPa, and the heat resistance and the impact resistance of the spring steel still need to be further improved.
Chinese patent CN109868423A, published as: 6, 11 and 2019, discloses high-strength spring steel with excellent fatigue performance and corrosion resistance and a production method thereof, wherein the steel comprises the following chemical components in percentage by weight: 0.40 to 0.45 percent of C, 2.00 to 2.50 percent of Si, 0.40 to 0.60 percent of Mn, 0.80 to 1.00 percent of Cr, 0.02 to 0.10 percent of V, 0.015 to 0.04 percent of Nb, 0.10 to 0.30 percent of Mo, 0.05 to 0.15 percent of Ni, 0.05 to 0.15 percent of Cu, 0.01 to 0.03 percent of Re, 0.015 percent of trace of P, 0.010 percent of trace of S, less than or equal to 0.0012 percent of O, 0.006 to 0.010 percent of N, less than or equal to 0.00015 percent of H, and the balance of Fe and other inevitable impurities. According to the application, through niobium-vanadium microalloying component design, smelting, refining, vacuum degassing, continuous casting and wire rolling routes, after heat treatment, the tensile strength of the spring steel is not less than 2000MPa, the spring steel has excellent fatigue resistance and good corrosion resistance, but the heat resistance of the spring steel is still to be further improved.
Disclosure of Invention
1. Technical problem to be solved by the invention
In view of the fact that no heat-resistant high-strength high-toughness spring steel can meet the existing use requirements at present, the invention provides the high-strength high-toughness spring steel used under the conditions of high temperature and high pressure and the production method thereof, the Mn content is properly reduced on the basis of the traditional spring steel 60Si2Mn, and meanwhile, a plurality of elements are added to change the performance of the steel, so that the use requirements of high heat resistance and high toughness are met.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the high-strength high-toughness spring steel used under the high-temperature and high-pressure conditions comprises, by weight, 0.30% -0.50% of C, 1.30% -1.80% of Si, 0.80% -1.00% of Mn, 0.10% -0.30% of Cr, 0.10% -0.30% of V, 0.020% -0.040% of Nb, 0.10% -0.30% of Mo, 0.60% -1.20% of W, 0.015% of trace P, 0.010% of trace S, and the balance of iron and other impurities.
Furthermore, the chemical composition proportion of the spring steel meets the formula
Meq＝[C]-(0.10[Cr]+0.20[V]+0.03[Nb]+0.05[W]+0.08[Mo]) (1)
Wherein the Meq value is 0.05-0.7.
Further, the Meq value is preferably 0.15 to 0.3.
Furthermore, the content of the impurity O in the spring steel is controlled to be less than or equal to 0.0012 percent.
Furthermore, the content of the impurity N in the spring steel is controlled to be less than or equal to 0.006 percent.
A production method of high-strength high-toughness spring steel used under high-temperature and high-pressure conditions comprises the following steps:
step one, smelting in an electric arc furnace;
step two, refining in an LF furnace;
step three, RH or VD vacuum degassing;
step four, round billet continuous casting;
step five, rolling the square billet;
step six, finishing and peeling;
step seven, rolling the high-speed wire rod;
step eight, slowly cooling the stelmor cooling line;
step nine, finishing the wire rod;
step ten, quenching and tempering the wire rod.
Further, in the seventh step, the heating temperature of the high-speed wire heating furnace is 980-1050 ℃; the time of the square billet in the furnace is less than or equal to 120 min.
Furthermore, in the seventh step, the initial rolling temperature is 880-980 ℃, the final rolling temperature is 750-830 ℃, and the spinning temperature is 830-860 ℃ during the wire rod rolling.
Further, in the tenth step, the quenching and tempering process comprises quenching, heating at 800-850 ℃ for 30min, oil cooling, tempering, heating at 400 ℃ for 120min, and air cooling to room temperature.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) according to the heat-resistant high-strength high-toughness spring steel, the Mn content is properly reduced on the basis of the traditional spring steel 60Si2Mn, meanwhile, elements such as W, Mo, V and Nb are added into the steel, and the content of each component in the steel is adjusted, so that the components are mutually cooperated, the tensile strength and the fatigue strength of the spring steel at high temperature are improved, meanwhile, the toughness of the obtained spring steel is improved, and the use requirement of the current industry is met.
(2) According to the heat-resistant high-strength high-toughness spring steel, elements such as V, Nb, W, Mo and Cr are added, so that the content of each element in the steel meets the formula Meq ═ C- (0.10[ Cr ] +0.20[ V ] +0.03[ Nb ] +0.05[ W ] +0.08[ Mo ]), the Meq value is preferably 0.15-0.3, on one hand, all C elements are dissolved in a solid solution, stable and fine dispersed carbides such as V, Nb, W and Mo are formed at high temperature, high strength and toughness and high yield ratio of the spring steel are ensured, and the heat resistance of the spring steel is improved; on the other hand, the content of Nb and V elements is controlled, and the grain size of the prior austenite is refined through the compounding of the Nb and V elements; and the hardenability, heat resistance and high-temperature tempering resistance of the spring steel are improved by using elements such as W, Mo and the like, so that the high-temperature tempering brittleness tendency of the steel is reduced, and the plastic toughness of the steel is further improved.
(3) According to the production method of the heat-resistant high-strength high-toughness spring steel, the temperature of each stage is controlled when the steel is subjected to heat treatment, so that the spring steel can achieve the best performance after the heat treatment. By controlling the quenching and high-temperature tempering treatment process of the steel, the heat treatment microstructure of the steel is fine zone oriented tempered troostite and a large amount of dispersed short rod-shaped or spherical fine carbide, the austenite grain size is more than or equal to 11 grades, the grain size is 20-25 mu m, and the average grain size of the carbide is 0.020-0.040 mu m.
(4) The invention relates to a production method of heat-resistant high-strength high-toughness spring steel, which has the following mechanical properties at normal temperature after heat treatment: the tensile strength is more than or equal to 1850MPa, the elongation after fracture is more than or equal to 10 percent, the reduction of area is more than or equal to 40 percent, the fatigue strength is more than or equal to 860MPa, and the fatigue life is more than or equal to 1000 ten thousand times under the condition of 850MPa cyclic stress; vertical impact absorption energy KV at normal temperature2Not less than 100J, high strength and good toughness; the tensile strength is more than or equal to 800MPa at the high-temperature mechanical property of 500 ℃, and the high-temperature heat-resistant steel has good strength, toughness and heat resistance.
Drawings
FIG. 1 is a gold phase diagram of austenite grain size of spring steel at 100 times magnification in example 1;
FIG. 2 is a table showing chemical components and structures used in examples and comparative examples of the present invention;
FIG. 3 is a table showing the normal temperature mechanical properties of the quenched and tempered steels obtained in the examples and comparative examples of the present invention after heat treatment;
FIG. 4 is a table of high temperature mechanical properties of quenched and tempered steels obtained in examples of the present invention and comparative examples.
Detailed Description
According to the heat-resistant high-strength high-toughness spring steel, the Mn content is properly reduced on the basis of the traditional spring steel 60Si2Mn, meanwhile, elements such as W, Mo, V and Nb are added into the steel, and the content of each component in the steel is adjusted, so that the components are mutually cooperated, the tensile strength and the fatigue strength of the spring steel at high temperature are improved, meanwhile, the toughness of the obtained spring steel is improved, and the use requirement of the current industry is met.
According to the invention, V, Nb, W, Mo, Cr and other elements are added into the spring steel, so that the content of each element in the steel meets the formula:
Meq＝[C]-(0.10[Cr]+0.20[V]+0.03[Nb]+0.05[W]+0.08[Mo])(1)
the Meq value is 0.05-0.7, preferably 0.15-0.3, on one hand, C is completely dissolved in solid solution, stable and fine dispersed carbides of V, Nb, W, Mo and the like are formed at high temperature, high strength and toughness and high yield ratio of the spring steel are ensured, and meanwhile, the heat resistance of the spring steel is improved; on the other hand, the content of Nb and V elements is controlled, and the grain size of the prior austenite is refined through the compounding of the Nb and V elements; and the hardenability, heat resistance and high-temperature tempering resistance of the spring steel are improved by using elements such as W, Mo and the like, so that the high-temperature tempering brittleness tendency of the steel is reduced, and the plastic toughness of the steel is further improved.
According to the production method of the heat-resistant high-strength high-toughness spring steel, the temperature of each stage is controlled when the steel is subjected to heat treatment, so that the spring steel can achieve the best performance after the heat treatment. Through quenching and high-temperature tempering of steel, the heat treatment microstructure of the steel is fine zone oriented tempered troostite and a large amount of dispersed short rod-shaped or spherical fine carbides, the austenite grain size is more than or equal to 11 grade, the grain size is 20-25 mu m, and the average grain size of the carbides is 0.020-0.040 mu m. The spring steel has the following mechanical properties at normal temperature after heat treatment: the tensile strength is more than or equal to 1850MPa, the elongation after fracture is more than or equal to 10 percent, the reduction of area is more than or equal to 40 percent, the fatigue strength is more than or equal to 860MPa, and the fatigue life is more than or equal to 1000 ten thousand times under the condition of 850MPa cyclic stress; vertical impact absorption energy KV at normal temperature2Not less than 100J, high strength and good toughness; the tensile strength is more than or equal to 800MPa at the high-temperature mechanical property of 500 ℃, and the high-temperature heat-resistant steel has good strength, toughness and heat resistance.
The spring steel comprises the following chemical components in percentage by weight: 0.30 to 0.50 percent of C, 1.30 to 1.80 percent of Si, 0.80 to 1.00 percent of Mn, 0.10 to 0.30 percent of Cr, 0.10 to 0.30 percent of V, 0.02 to 0.04 percent of Nb, 0.10 to 0.30 percent of Mo, 0.60 to 1.20 percent of W, 0.015 percent of trace of P, 0.010 percent of trace of S and the balance of iron and other impurities. And the content of O is controlled to be less than or equal to 0.0012 percent and the content of N is controlled to be less than or equal to 0.006 percent. Meanwhile, the chemical component proportion needs to be ensured to satisfy the relation:
Meq＝[C]-(0.10[Cr]+0.20[V]+0.03[Nb]+0.05[W]+0.08[Mo])(1)
wherein the Meq value is 0.05 to 0.7, preferably 0.15 to 0.3. The relation is to ensure that the carbide is evenly and finely dispersed and precipitated, fully exert the precipitation strengthening effect, ensure that the average grain size of the precipitated Nb-V carbide is 0.020-0.040 mu m, ensure the grain size to be more than or equal to 11 grades, and have fatigue performance.
Wherein, each element has the following functions:
c: c is the most effective reinforcing element in steel, is an important element for ensuring the fire hardness and wear resistance in spring steel, and is necessary for obtaining spring steel having high strength and hardness. The high carbon content is advantageous for strength, hardness, elasticity, and creep properties of the steel, but is disadvantageous for plasticity and toughness of the steel, and also causes a decrease in yield ratio of the spring steel, an increase in decarburization sensitivity, and deterioration in fatigue resistance and workability of the steel.
Si: si is an important element for strengthening in steel, and the strong hardness of the steel is improved through the solid solution effect, and meanwhile, the sag resistance of the spring steel is improved. Silicon can improve the stability of the rust layer and the corrosion resistance. However, the increase of the Si element increases the diffusion of carbon in the steel, and thus the decarburization of the steel is promoted.
Mn: mn and Fe form a solid solution, so that the hardness and strength of ferrite and austenite in the steel are improved, and meanwhile, Mn is used for improving the stability of an austenite structure and remarkably improving the hardenability of the steel. However, excessive Mn lowers the plasticity of the steel. The addition of Mn is simultaneously beneficial to forming a rust layer on the surface of the steel and improving the corrosion resistance of the steel, but excessive Mn can cause the growth of corrosion product particles and improve the corrosion rate.
Cr: cr and C can form a stable compound, prevent segregation of C or impurities, improve the stability of a matrix, obviously improve the antioxidation of steel and increase the corrosion resistance of the steel. Chromium can significantly increase the hardenability of the steel, but excess Cr increases the temper brittleness tendency of the steel.
V: v is an excellent deoxidizer of steel, vanadium is added into the steel to refine structure grains and improve the strength and the toughness, and the V element can improve the tempering resistance of the steel, and vanadium carbonitride precipitated during tempering at higher temperature can produce secondary hardening to further improve the strength of the steel.
Nb: nb is a microalloying element for refining grains very effectively, and the Nb in steel has the characteristic of improving the recrystallization temperature of austenite so as to achieve the purpose of refining austenite grains. The addition of Nb promotes the generation of a stable rust layer, and obviously reduces the corrosion rate. However, the strengthening effect of excess Nb is no longer significant and increases the crack sensitivity of the steel.
Mo: mo is a stronger carbide forming element, can improve the strength and hardness of steel, can also obviously improve the high-temperature strength, and is the most effective alloy element for improving the heat strength of the steel. In addition, Mo element can improve the hardenability and the tempering stability of the steel, effectively eliminate or reduce the residual stress therein and improve the plasticity thereof. The addition of Mo to spring steel improves the resistance to springing, since Mo can form finely dispersed carbides that prevent dislocation motion. The addition of Mo also reduces the incidence of pitting, but too much Mo content increases the deformation resistance and the inter-granular corrosion tendency.
W: high temperature resistance, which is a solid solution formed by partially dissolving iron in steel in addition to carbide, can improve the normal temperature strength and high temperature strength of steel, increase the tempering stability, red hardness, hot strength and wear resistance, but excessive W can reduce the toughness and high temperature oxidation resistance of steel.
S and P: the sulfur is easy to form MnS inclusion with manganese in the steel, and is unfavorable for the fatigue property of the spring; p is an element with a strong segregation tendency and usually also causes co-segregation of sulphur and manganese, which is detrimental to the homogeneity of the product structure and properties. P is controlled to be less than or equal to 0.015 percent, and S is controlled to be less than or equal to 0.010 percent.
When the spring steel is smelted, O and N are impurities in the spring steel, and the content of the impurities needs to be controlled: o forms oxide inclusions in the steel, and the content of O is controlled to be less than or equal to 0.0012%; n precipitation of Fe in steel4N is low in diffusion speed, so that the steel has timeliness, and simultaneously, the cold processing performance of the steel is reduced by the N, and the N is controlled to be less than or equal to 0.006%.
For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
Example 1
The specific production process flow of the spring steel of the embodiment is as follows: electric arc furnace smelting → LF furnace refining → RH or VD vacuum degassing → round billet continuous casting → square billet rolling → finishing and skimming → high-speed wire rod rolling → stelmor cooling line slow cooling → phi 6.5-25 mm wire rod finished product → rod quenching and tempering.
When the high-speed wire rod is rolled, the heating temperature of the high-speed wire rod heating furnace is 980-1050 ℃, and preferably 1000-1030 ℃. The furnace time of the square billet is less than or equal to 120min, preferably 100 min. When the wire rod is rolled, the initial rolling temperature is 880-980 ℃, and preferably 900-920 ℃; the finishing temperature is 750-830 ℃, preferably 780-810 ℃; the spinning temperature is 830-860 ℃, and preferably 840-850 ℃.
The wire rod rolling adopts high-speed, no-twist and low-tension rolling, the heating temperature of a billet is controlled to be less than or equal to 1050 ℃ during rolling, and the billet quickly passes through a low-temperature full-decarburization sensitive area at 800-900 ℃. The finish rolling temperature is controlled to be above 900 ℃, the controlled rolling of a non-recrystallization area is realized, and the strength and toughness of the steel are improved. The controlled cooling adopts a slow cooling process, and the cooling speed is controlled to slowly cool by controlling the speed of the roller way, the air quantity of the fan and the opening and closing quantity of the heat-insulating cover, so that the generation of bainite is prevented.
The hot rolled spring steel wire rod of the present example was subjected to the following thermal refining: quenching at 800-850 ℃ for 30min and oil cooling, tempering at 400 ℃ for 120min and air cooling to room temperature, wherein the heat treatment microstructure is fine band oriented tempered troostite and a large amount of dispersed short rod-shaped or spherical fine carbide, the austenite grain size is not less than 11 grade, the grain size is 20-25 mu m, and the average grain size of the carbide is 0.020-0.040 mu m. Mechanical properties at normal temperature after heat treatment: the tensile strength is more than or equal to 1850MPa, the elongation after fracture is more than or equal to 10 percent, the reduction of area is more than or equal to 40 percent, the fatigue strength is more than or equal to 860MPa, and the fatigue life is more than or equal to 1000 ten thousand times under the condition of 850MPa cyclic stress. Vertical impact absorption energy KV at normal temperature2Not less than 100J, high strength and good toughness; the tensile strength is more than or equal to 800MPa at the high-temperature mechanical property of 500 ℃, and the high-temperature heat-resistant steel has good strength, toughness and heat resistance.
Specifically, the spring steel of the present embodiment is composed of: 0.40% of C, 1.53% of Si, 0.84% of Mn, 0.25% of Cr, 0.10% of V, 0.020% of Nb, 0.25% of Mo, 0.10% of W, 0.008% of P, 0.002% of S and the balance of iron and other impurities. In this embodiment, the heating temperature of the high-speed wire rod heating furnace is preferably 1000 ℃. The time of the billet in the furnace is preferably 100 min. When the wire rod is rolled, the initial rolling temperature is preferably 900 ℃; the finishing temperature is preferably 780 ℃; the spinning temperature is preferably 840 ℃. The heat treatment process comprises the following steps: quenching at 830 deg.C (oil cooling), and tempering at 400 deg.C for 120min (air cooling). The structure after heat treatment is tempered troostite. The hot rolled structure is pearlite + ferrite, and the austenite grain size is 11 grades.
Example 2
The spring steel and the production method of the spring steel are basically the same as those of the embodiment 1, except that the spring steel of the embodiment comprises the following chemical components: 0.35% of C, 1.56% of Si, 0.85% of Mn, 0.23% of Cr, 0.18% of V, 0.028% of Nb, 0.21% of Mo, 0.84% of W, 0.007% of P, 0.003% of S, and the balance of iron and other impurities. In this embodiment, the heating temperature of the high-speed wire rod heating furnace is preferably 1010 ℃. The time of the billet in the furnace is preferably 110 min. When the wire rod is rolled, the initial rolling temperature is preferably 910 ℃; the final rolling temperature is preferably 790 ℃; the spinning temperature is preferably 842 ℃. The heat treatment process comprises the following steps: quenching at 830 deg.C (oil cooling), tempering at 400 deg.C for 120min, and air cooling. The structure after heat treatment is tempered troostite. The hot rolled structure is pearlite + ferrite, and the austenite grain size is 11.5 grade.
Example 3
The spring steel and the production method of the spring steel are basically the same as those of the embodiment 1, except that the spring steel of the embodiment comprises the following chemical components: 0.42% of C, 1.55% of Si, 0.83% of Mn, 0.24% of Cr, 0.25% of V, 0.030% of Nb, 0.23% of Mo, 0.88% of W, 0.009% of P, 0.002% of S, and the balance of iron and other impurities. In this embodiment, the heating temperature of the high-speed wire rod heating furnace is preferably 1020 ℃. The time of the billet in the furnace is preferably 110 min. When the wire rod is rolled, the initial rolling temperature is preferably 915 ℃; the final rolling temperature is preferably 800 ℃; the spinning temperature is preferably 845 ℃. The heat treatment process comprises the following steps: quenching at 830 deg.C (oil cooling), and tempering at 400 deg.C for 120min (air cooling) at quenching medium temperature of 30 deg.C. The structure after heat treatment is tempered troostite. The hot rolled structure is pearlite + ferrite, and the austenite grain size is 11.5 grade.
Example 4
The spring steel and the production method of the spring steel are basically the same as those of the embodiment 1, but the spring steel of the embodiment comprises the following chemical components: 0.33% of C, 1.53% of Si, 0.82% of Mn, 0.22% of Cr, 0.30% of V, 0.040% of Nb, 0.25% of Mo, 0.90% of W, 0.006% of P, 0.001% of S, and the balance of iron and other impurities. In this embodiment, the heating temperature of the high-speed wire heating furnace is preferably 1030 ℃ in the high-speed wire rolling. The time of the billet in the furnace is preferably 120 min. When the wire rod is rolled, the initial rolling temperature is preferably 920 ℃; the final rolling temperature is preferably 810 ℃; the spinning temperature is preferably 850 ℃. The heat treatment process comprises the following steps: quenching at 830 deg.C (oil cooling), and tempering at 400 deg.C for 120min (air cooling). The structure after heat treatment is tempered troostite. The hot rolled structure is pearlite + ferrite, and the austenite grain size is 11 grades.
Comparative example 1
The spring steel of the comparative example comprises the following chemical components: 0.57% of C, 1.91% of Si, 0.80% of Mn, 0.23% of Cr, 0.001% of P, 0.001% of S, and the balance of Fe and other inevitable impurities. The hot rolling structure is pearlite + ferrite, and the austenite grain size is 10 grades.
Comparative example 2
The spring steel of the comparative example comprises the following chemical components: 1.50% of C, 1.55% of Si, 0.83% of Mn, 0.25% of Cr, 0.03% of V, 0.15% of Nb, 0.35% of Mo, 0.50% of W, 0.006% of P, 0.001% of S, and the balance of Fe and other inevitable impurities. The hot rolled structure is pearlite + ferrite, and the austenite grain size is grade 10.
Comparative example 3
The spring steel of the comparative example comprises the following chemical components: 0.20% of C, 1.55% of Si, 0.83% of Mn, 0.05% of Cr, 0.4% of V, 0.10% of Nb, 0.35% of Mo, 1.25% of W, 0.006% of P, 0.001% of S, and the balance of Fe and other unavoidable impurities. The hot rolling structure is pearlite + ferrite, and the austenite grain size is 10 grades.
With reference to fig. 1, the heat-treated blank was finished into a standard tensile sample, and mechanical properties at room temperature were analyzed, and the results are shown in fig. 3. Fine machining the blank after heat treatment into a high-temperature tensile sample, then carrying out high-temperature mechanical property analysis, and processing the spring steel after rough machining and heat treatment into a rotary bending fatigue sample to carry out rotary bending fatigueAnd (4) testing. The spring steel was subjected to the rotational bending fatigue test in accordance with the standard GB/T4337-2015 rotational bending test for Metal materials. The test is carried out on a laboratory PQ1-6 fatigue testing machine by adopting axial strain control, the strain cycle ratio R is-1, the frequency is 83Hz, the room temperature is 20 ℃, the loading waveform of the fatigue test is a sine wave, and the criterion of the test ending is 107Secondary or sample failure. The analysis results of the high temperature mechanical properties and fatigue strength are shown in FIG. 4.
With the combination of the figures 2-4, the strength of the embodiment reaches more than 1800MPa, the elongation reaches more than 10%, the face shrinkage reaches more than 40%, the grain size is more than or equal to 11 grade, and the longitudinal impact absorption power KV at normal temperature2The tensile strength is more than or equal to 100J and more than or equal to 800MPa at 500 ℃, which shows that the spring steel obtained in the embodiment has better obdurability, heat resistance and excellent fatigue property, and meets the requirement of spring use in a high-temperature environment. Comparative example 1 does not contain the key elements added in the present invention, and comparative examples 2 and 3 contain these elements, but the contents of the elements do not conform to the formula (1), and it can be seen from the figure that the spring steels obtained by the three comparative examples are significantly weaker than those of the examples.
The invention and its embodiments have been described above schematically, without limitation, and in the drawings they are shown as just one of the embodiments of the invention. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (5)
1. A high-strength high-toughness spring steel used under high-temperature and high-pressure conditions is characterized in that: the spring steel comprises, by weight, 0.30-0.50% of C, 1.30-1.80% of Si, 0.80-1.00% of Mn, 0.10-0.30% of Cr, 0.10-0.30% of V, 0.020-0.040% of Nb, 0.10-0.30% of Mo, 0.60-1.20% of W, 0.015% of trace of P, 0.010% of trace of S and the balance of iron and other impurities; the chemical component proportion of the spring steel meets the formula
Meq＝[C]-(0.10[Cr]+0.20[V]+0.03[Nb]+0.05[W]+0.08[Mo]) (1)
Wherein the Meq value is 0.05-0.7;
in the production process of the spring steel, the heating temperature of the spring steel heated by a high-speed wire heating furnace is 980-1050 ℃; the time of the square billet in the furnace is less than or equal to 120 min;
when the wire rod is rolled, the initial rolling temperature is 880-980 ℃, the final rolling temperature is 750-830 ℃, and the spinning temperature is 830-860 ℃;
the quenching and tempering process comprises the steps of quenching, heating at 800-850 ℃ for 30min, oil cooling, tempering, heating at 400 ℃ for 120min, and air cooling to room temperature;
the microstructure of the spring steel after heat treatment is fine tempered troostite with orientation and a large amount of dispersed short rod-shaped or spherical fine carbide, and the austenite grain size of the spring steel>11-grade, the grain size is 20-25 μm, and the average grain size of carbide is 0.020-0.040 μm; the spring steel has the following mechanical properties at normal temperature after heat treatment: the tensile strength is more than or equal to 1850MPa, the elongation after fracture is more than or equal to 10 percent, the reduction of area is more than or equal to 40 percent, and the fatigue strength is more than or equal to 860 MPa; vertical impact absorption energy KV at normal temperature2Not less than 100J, high-temperature mechanical property of 500 deg.C and tensile strength of not less than 800 MPa.
2. A high strength and high toughness spring steel for use under high temperature and high pressure conditions as claimed in claim 1, wherein: the Meq value is preferably 0.15 to 0.3.
3. A high strength and toughness spring steel for use in high temperature and high pressure conditions according to claim 2, wherein: the content of impurity O in the spring steel is controlled to be less than or equal to 0.0012 percent.
4. A high strength and toughness spring steel for use in high temperature and high pressure conditions according to claim 3 wherein: the content of impurity N in the spring steel is controlled to be less than or equal to 0.006 percent.
5. Method for producing a spring steel according to any one of claims 1-4, characterized in that it comprises the steps of:
step one, smelting in an electric arc furnace;
step two, refining in an LF furnace;
step three, RH or VD vacuum degassing;
step four, round billet continuous casting;
step five, rolling the square billet;
step six, finishing and peeling;
step seven, rolling the high-speed wire rod;
step eight, slowly cooling the stelmor cooling line;
step nine, finishing the wire rod;
step ten, quenching and tempering the wire rod.
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| CN1847438A (en) * | 2005-04-11 | 2006-10-18 | 株式会社神户制钢所 | Steel wire for cold-formed spring excellent in corrosion resistance and method for producing the same |
| CN109811266A (en) * | 2019-03-19 | 2019-05-28 | 马鞍山钢铁股份有限公司 | A kind of anti-corrosion spring steel and its production method of tensile strength >=2000MPa |
| JP2019178405A (en) * | 2018-03-30 | 2019-10-17 | Ｊｆｅスチール株式会社 | Production method of steel wire |
| JP2020007619A (en) * | 2018-07-10 | 2020-01-16 | 日本発條株式会社 | Compression coil spring and manufacturing method therefor |
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| CN1847438A (en) * | 2005-04-11 | 2006-10-18 | 株式会社神户制钢所 | Steel wire for cold-formed spring excellent in corrosion resistance and method for producing the same |
| JP2019178405A (en) * | 2018-03-30 | 2019-10-17 | Ｊｆｅスチール株式会社 | Production method of steel wire |
| JP2020007619A (en) * | 2018-07-10 | 2020-01-16 | 日本発條株式会社 | Compression coil spring and manufacturing method therefor |
| CN109811266A (en) * | 2019-03-19 | 2019-05-28 | 马鞍山钢铁股份有限公司 | A kind of anti-corrosion spring steel and its production method of tensile strength >=2000MPa |
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