CN116043115B - Cold and hot fatigue resistant forged steel for high-speed railway brake disc and heat treatment method and production method thereof - Google Patents

Cold and hot fatigue resistant forged steel for high-speed railway brake disc and heat treatment method and production method thereof Download PDF

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CN116043115B
CN116043115B CN202310046192.9A CN202310046192A CN116043115B CN 116043115 B CN116043115 B CN 116043115B CN 202310046192 A CN202310046192 A CN 202310046192A CN 116043115 B CN116043115 B CN 116043115B
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steel
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CN116043115A (en
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陈世杰
胡芳忠
汪开忠
金国忠
庄振
陈恩鑫
杨少朋
杨志强
周大元
吴胜付
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Maanshan Iron and Steel Co Ltd
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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
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Abstract

The invention discloses cold and hot fatigue resistant forged steel for a high-speed railway brake disc, and a heat treatment method and a production method thereof, wherein the cold and hot fatigue resistant forged steel for the high-speed railway brake disc comprises the following components: C. si, mn, cr, mo, ni, cu, nb, W, ti, V, al, zr, B, by controlling the content of each chemical component and the relation numerical value among part of chemical components, the cold and hot fatigue resistant forged steel for the high-iron brake disc, which has the mechanical properties of tensile strength of more than or equal to 1250MPa, yield strength of more than or equal to 1150MPa, A of more than or equal to 18%, Z of more than or equal to 65%, KV2 of more than or equal to 150J at 20 ℃ and tensile strength of more than or equal to 640MPa at 700 ℃ and has excellent cold and hot fatigue performance, is obtained, and has no cracks after cold and hot circulation for 1000 times at 800-20 ℃.

Description

Cold and hot fatigue resistant forged steel for high-speed railway brake disc and heat treatment method and production method thereof
Technical Field
The invention belongs to the field of alloy forged steel for brake discs, and particularly relates to cold and hot fatigue resistant forged steel for a high-speed railway brake disc, and a heat treatment method and a production method thereof.
Background
In recent years, the world rapid transit railway is rapidly developed, and the degree of high speed is higher and higher. With the increase of train speed, higher demands are being placed on the braking devices and the braking materials. For high speed trains, the large energy generated by braking is dissipated by the foundation braking element in a short period of time, which is a significant and critical issue. The brake disc is a core component in a basic brake device, plays an important role, and huge heat load, thermal shock and thermal cycle generated in the braking process can lead to the phenomena of reduced disc body manufacturing efficiency, high-temperature abrasion, thermal fatigue failure and the like, so that the steel for the brake disc is required to have excellent normal temperature performance, good high temperature performance, heat conduction performance and cold-hot fatigue performance.
The high-speed railway brake disc is used as an important part for ensuring the safe operation of the high-speed railway, and currently common materials of the high-speed railway brake disc in the world comprise AISI 4330, 28CrMoV5-08, 15CDV6 and the like, and the materials can meet the requirements of trains with the speed of 350 km per hour and below and cannot be applied to trains with higher speed per hour. With the rapid development of rail transportation industry, the rapid construction of coastal high-speed rails causes higher requirements on steel for brake discs of high-speed trains, and development of brake disc materials with excellent normal temperature, high temperature performance and thermal fatigue performance is urgently needed.
At present, most high-speed trains use cast steel or forged steel brake discs, but composite brake discs are still in a research and development stage and cannot be widely popularized and applied. And the cast steel brake disc has higher cost due to more alloy elements. The related patents disclosed in China mainly relate to the normal-temperature mechanical properties of the brake disc material of the high-speed train, and the fresh patents relate to the high-temperature properties and cold-hot fatigue resistance of the brake disc material, and the toughness of the brake disc material is difficult to consider while the high-temperature mechanical properties of the brake disc material are improved. The high-speed train brake disc material with excellent comprehensive mechanical properties and fatigue resistance is developed, and has important significance for improving the service performance and service life of the brake disc, realizing localization of the brake disc of the high-speed train and ensuring the running safety of the train.
Chinese patent CN105779893B discloses an alloy cast steel for a brake disc of a high-speed train and a brake disc of a high-speed train manufactured from the alloy cast steel, which is characterized in that the total content of other components ,C 0.18％～0.26％;Si 0.30％～0.50％;Mn 0.68％～1.40％;P≤0.025％;S≤0.013％;Cr 1.10％～1.82％;Ni 0.90％～1.50％;Mo 0.65％～1.02％;V 0.22％～0.34％; is less than or equal to 0.30% by weight, wherein W is less than 0.1%; fe is the balance; normalizing at 900-980 deg.c for 3.5-5 hr, water quenching at 900-980 deg.c for 3.5-5 hr, and tempering at 580-650 deg.c for 3.5-5 hr, and the alloy cast steel has the following mechanical performance indexes after heat treatment: tensile strength is equal to or more than 1050MPa; yield strength is more than or equal to 935MPa; the elongation is more than or equal to 14%; the area shrinkage rate is more than or equal to 35 percent. The alloy cast steel has the defect that the crack length of the V-shaped notch is about 0.31mm after 600 times of 600-20 ℃ cold and hot fatigue tests, and the strength, toughness and cold and hot fatigue performance cannot meet the requirements of a high-speed iron brake disc with 400 km per hour.
Chinese patent CN111360198B discloses a cast steel for high-toughness cold-hot fatigue resistant high-speed train brake disc and preparation method, which is characterized in that the chemical composition ratio is C：0.20～0.40％,Si：0.30～0.70％,Mn：0.50～2.00％,P≤0.015％,S≤0.010％,Cr：0.50～2.00％,Ni：0.50～2.00％,Mo：0.40～1.80％,Nb：0.010～0.030％,V：0.01～0.30％,N≤0.015％,O≤0.010％,, and the balance is Fe and residual trace impurity according to weight percentage; the total content of Mn+Cr+Ni is 2.00-6.00%, and the total content of Mo+V is 0.71-1.35%. The cast steel material has room temperature mechanical properties: the yield strength is more than or equal to 1000MPa, the tensile strength is more than or equal to 1100MPa, the elongation after breaking is more than or equal to 12.0%, and the room temperature impact absorption power (KV 2) is more than or equal to 50J;600 ℃ high temperature mechanical properties: the yield strength is more than or equal to 500MPa, and the tensile strength is more than or equal to 550MPa. The defect is that the normal temperature mechanical property and the high temperature property of the steel are not enough to meet the requirement of a high-speed rail brake disc with the speed of 400 km per hour.
Chinese patent CN107760992A discloses a steel for a brake disc of a tungsten-containing high-speed train, which is characterized in that the percentage of chemical components is C：0.20～0.30％,Si：0.20～0.40％,Mn：0.20～0.40％,P≤0.010％,S≤0.005％,Cr：0.90～1.50％,Ni≤0.20％,Mo：0.40～0.90％,Al≤0.025％,V：0.70～1.00％,W：0.70～1.20％,Cu≤0.20％,N≤0.0050,, the balance is Fe and residual trace impurities, the material has excellent high-temperature performance, the tensile strength at 500 ℃ is more than or equal to 1000MPa, the tensile strength at 600 ℃ is more than or equal to 900MPa, the toughness and the high-temperature performance above 600 ℃ of the material are not characterized, the whole heat treatment temperature is higher, the quenching and tempering temperature interval is narrower, and the industrial mass production is not facilitated.
At present, although the research of the steel for the high-speed railway brake disc in China has a certain accumulation, the steel can only meet the requirement of a train with the speed of 350 km per hour and below, and the research on the brake disc of the high-speed train with the speed of 400 km per hour and above is almost blank. Along with Gao Tiedi speed, development of high-speed rail brake disc steel with high strength and toughness, good high-temperature performance and excellent thermal fatigue performance is urgently needed.
Disclosure of Invention
The invention aims to provide cold and hot fatigue resistant forged steel for a high-speed railway brake disc, a heat treatment method and a production method thereof, wherein the cold and hot fatigue resistant forged steel for the high-speed railway brake disc, which has excellent cold and hot fatigue resistant performance, is obtained by controlling the content of each chemical component and the relational numerical value among part of the chemical components, and has the mechanical properties of tensile strength of more than or equal to 1250MPa, yield strength of more than or equal to 1150MPa, A of more than or equal to 18%, Z of more than or equal to 65%, KV2 of more than or equal to 150J of 20 ℃ and tensile strength of more than or equal to 640MPa of 700 ℃ after cold and hot circulation for 1000 times at 800-20 ℃.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
The cold and hot fatigue resistant forged steel for the high-speed rail brake disc contains ：C 0.18％～0.25％、Si 0.15％～0.40％、Mn 0.40％～0.80％、Cr 1.00％～1.50％、Mo 0.90％～1.20％、Ni 0.40％～0.60％、Zr：0.020％～0.030％、Nb 0.010％～0.040％、B：0.0006～0.0010％、W：0.20％～0.40％、Cu 0.22％～0.48％、Ti：0.040％～0.080％、V 0.25％～0.35％、Al 0.015％～0.040％、P≤0.015％、S≤0.010％、N≤0.0050％、T.O≤0.0012％, weight percent of Fe and other unavoidable impurities;
Wherein,
36.5≤λ700℃＝32.65+0.25W-2.2V+0.64Mo+0.35Cr+17Cu-1.08Ni-1.66Mn-3.67Si
+4.52C+1.36Zr≤38.5；
14.5≤X＝6C+4Cr+3.6Mo+2.8Ni+3.2W+24Nb+28Ti+3.5V+386B≤18.5。
The metallographic structure of the cold and hot fatigue resistant forged steel for the high-speed railway brake disc is tempered sorbite.
The cold and hot fatigue resistant forged steel for the high-speed railway brake disc has the tensile strength of more than or equal to 1250MPa and the yield strength
More than or equal to 1150MPa, more than or equal to 18 percent of A, more than or equal to 65 percent of Z, more than or equal to 150J of 20 ℃ KV2, more than or equal to 640MPa of tensile strength at 700 ℃; after 1000 times of cold and hot circulation at 800-20 ℃, no crack is generated.
The heat treatment method of the cold and hot fatigue resistant forged steel for the high-speed railway brake disc comprises the following steps of:
(1) Normalizing: heating the brake disc to 920-1020 ℃, preserving heat, and then air-cooling; through the normalizing treatment, the alloy elements in the steel for the brake disc are fully and uniformly dissolved, so that preparation is made for subsequent quenching and tempering;
(2) Quenching: heating the brake disc to 880-960 ℃, preserving heat, and then water-cooling to ensure that the austenite grain size in the steel is moderate;
(3) Tempering: heating the brake disc to 600-680 ℃, preserving heat, then air-cooling, eliminating internal structural stress through tempering, fully precipitating carbide in the steel, ensuring moderate carbide size, ensuring that the steel for the brake disc has excellent toughness matching, improving the structural stability of the steel in the quenching and rapid heating process, and improving the high-temperature performance of the steel.
In the normalizing process, the heating speed is 100-160 ℃/h, the heat preservation time t is determined by the thickness delta of a brake disc, t=1.5-2.5 delta, the unit of t is min, and the unit of delta is mm.
In the quenching process, the heating speed is 100-160 ℃/h, the heat preservation time t is determined by the thickness delta of a brake disc, t=1.0-1.2 delta, the unit of t is min, and the unit of delta is mm.
In the tempering process, the heating speed is 50-110 ℃/h, the heat preservation time t is determined by the thickness delta of the brake disc, t=2.0-4.0 delta, the unit of t is min, and the unit of delta is mm.
The production method of the cold and hot fatigue resistant forged steel for the high-speed railway brake disc comprises the following steps: smelting in an arc furnace or a converter, refining in an LF furnace, vacuum degassing in RH or VD, continuous casting, heating in a casting blank heating furnace, rolling round steel for a brake disc, forging a brake disc blank, heat treatment, machining, flaw detection, packaging and warehousing, wherein the heat treatment process is carried out by adopting the heat treatment method.
The cold and hot fatigue resistant forged steel for the high-speed railway brake disc comprises the following components in parts by weight:
C: c is the least expensive strengthening element in the steel, and each 0.1% of solid solution C can improve the strength by about 450MPa, and the C and the alloy element in the steel form a precipitated phase to play a role in precipitation strengthening. C can obviously improve the hardenability, but as the content of C increases, the plasticity and toughness decrease, so the content of C is controlled to be 0.18-0.25%.
Si: si is an effective solid solution strengthening element in steel, improves the strength and the hardness of the steel, can play a deoxidizing role in steelmaking, and is a common deoxidizer. However, si tends to be biased at austenite grain boundaries, which reduces the grain boundary binding force and causes brittleness. In addition, si tends to cause element segregation in steel. Therefore, the Si content is controlled to be 0.15% to 0.40%.
Mn: mn can play a solid solution strengthening role, the solid solution strengthening capability is weaker than that of Si, mn is an austenite stabilizing element, the hardenability of steel can be obviously improved, decarburization of steel can be reduced, and the combination of Mn and S can prevent hot shortness caused by S. However, excessive Mn can reduce the plasticity of the steel, and simultaneously can easily cause austenite-martensite transformation in the repeated heating and cooling process, so that the thermal expansion coefficient and the heat conduction coefficient are shock-changed, and the cold-hot fatigue performance of the brake disc is reduced. Therefore, the Mn content is controlled to be 0.40-0.80%.
Cr: cr is a carbide forming element, can improve the hardenability, strength and wear resistance of steel, can improve the high-temperature performance and fatigue resistance of steel, is an important alloy element of heat-resistant steel, but is easy to cause tempering brittleness, and can increase reheat crack sensitivity when the Cr content is too high. The Cr content should be controlled to be 1.00% -1.50%.
Mo: mo is mainly used for improving the hardenability and the heat strength of steel, maintaining enough strength and creep resistance at high temperature, enabling the structure of the steel to maintain higher stability in the tempering process, effectively reducing the segregation of P, S, as and other impurity elements at the grain boundary, improving the toughness of the steel and reducing the tempering brittleness. Mo can improve the strength of steel by the combined action of solid solution strengthening and precipitation strengthening, and can also change the toughness of steel by changing the precipitation of carbide. Mo is controlled to be 0.90-1.20%.
Ni: ni can form infinite mutual-soluble solid solution with Fe, is an austenite stabilizing element, has the effect of expanding a phase area, increases the stability of supercooled austenite, makes a C curve move right, and improves the hardenability of steel. Ni can refine the width of the martensite lath and improve the strength. Ni is used for obviously reducing the ductile-brittle transition temperature of steel and improving the low-temperature toughness. With the increase of the nickel content, the normal temperature strength and the high temperature strength of the steel are increased, but the influence on the plasticity and the toughness is not great, but the Ni element is a noble metal element, and excessive addition causes excessive cost. The Ni content is controlled to be 0.40% -0.60%.
Nb: nb is a strong C, N compound forming element, nb (C, N) is finely dispersed and maintains a coherent relation with the matrix, so that the matrix can play a role in strengthening and refining tissues, and the strengthening of the matrix can increase the fatigue crack initiation and propagation resistance, thereby improving the fatigue strength. The Nb content is controlled to be 0.010-0.040 percent.
Ti: ti is a strong carbide forming element, and the addition of a proper amount of titanium into steel can obviously refine structural grains, improve strength and toughness, and particularly has obvious contribution to improving impact toughness. The Ti content is controlled to be 0.040-0.080 percent.
V: v is a widely used microalloying element that has the effect of preventing austenite grain growth when heated. The addition of vanadium prevents the growth of austenite grains by the precipitation of V (C, N) and the grain boundary pinning of undissolved V (C, N) particles, thereby improving the toughness of the steel, but at the same time, reducing the hardenability of the steel. The research results show that the V content is about 0.30 percent, and the effect of improving the high-temperature strength is most obvious, so that the V content is controlled to be 0.25 to 0.35 percent.
Nb, ti, V are the most commonly used microalloying elements, which in turn decrease the pinning effect on grain boundaries. The addition of Nb, ti, V and other alloys can form carbonitride, and the steel is strengthened through dissolution-precipitation behavior in the heating and cooling processes of the steel, and in addition, microalloy elements exist in the steel in the form of substitutional solute atoms, are easy to be aggregated on dislocation lines, generate strong dragging action on the dislocation, and finally play a strong role in preventing recrystallization.
Zr: the Zr alloy has good plasticity and good weldability, and can be used for welding processing. Has deoxidizing, nitrogen removing and sulfur removing effects. And the hardness and strength of the alloy are greatly improved by a small amount of zirconium. The Zr content is controlled to be 0.020 to 0.030 percent.
B: b can refine grains, remarkably improve hardenability of steel, and simultaneously can improve wear resistance and strength of steel, B in grain boundary has a function of preventing recrystallization diffusion, and can increase high temperature strength of steel, but excessive B easily causes brittleness. Therefore, the content of B is controlled to be 0.0006-0.0010%.
Cu: cu has a solid solution strengthening effect, and the solid solution strengthening degree is similar to Mn. However, cu produces high crack sensitivity in the steel, which reduces the cold and hot fatigue performance of the brake disc. The Cu content is controlled to be 0.22-0.48%.
W: w is a strong carbide forming element, so that the high-temperature strength and heat resistance of the steel are improved, and the content of W is controlled to be 0.20-0.40%.
Al: al is a stronger deoxidizing element and forms an AlN precipitated phase with N element in steel to have the effect of inhibiting grain growth, but the high-temperature performance is reduced due to the ultra-fine grains, and the content of Al is controlled to be 0.015% -0.040%.
P and S: sulfur easily forms MnS inclusions with manganese in the steel, so that the steel is thermally brittle; p is an element with strong segregation tendency, increases the cold brittleness of steel, reduces plasticity, and is harmful to uniformity of product structure and performance. Controlling P to be less than or equal to 0.015 percent and S to be less than or equal to 0.010 percent.
T.o and N: b has strong affinity with O, N, and is easy to generate nonmetallic inclusions with high hardness and low toughness, so that the content of T.O and N in steel is strictly controlled, the content of T.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 0.0050 percent.
The heat conductivity of pure iron gradually decreases along with the rise of temperature, and the influence of different alloy elements in steel on the heat conductivity is different, so that the steel still has good heat conductivity under the high temperature condition, the problem that local overheating is caused by the fact that heat generated by braking cannot be conducted rapidly in the high-speed emergency braking process is avoided, fatigue failure occurs, the proportion of C, si, mn, cr, ni, mo, V, W, cu, zr is limited, and therefore the steel still has high heat conductivity at high temperature is guaranteed. The impurity elements such as P, S have great influence on the heat conductivity coefficient of steel, but the P, S content is extremely low in the invention, so the influence is negligible. The addition of the C atoms distributes more strong carbide forming elements and weak carbide forming elements such as Mn from the matrix of the steel into the carbide, so that the influence of the elements on the heat conductivity is weakened, and the influence coefficient of the C content on the heat conductivity is higher and is 4.52. The significant difference in the electronic structure of the outer layers of the semiconductor element Si and the base Fe results in a significant reduction in the thermal conductivity of the steel, so the Si coefficient is-3.67. The influence of carbide forming elements on the heat conductivity is weaker than that of non-carbide forming elements, and the carbide forming elements have different contribution coefficients according to different contribution degrees of different alloy elements on the heat conductivity, so that the calculation formula of the heat conductivity of the steel at the high temperature of 700 ℃ is as follows:
λ700℃＝32.65+0.25W-2.2V+0.64Mo+0.35Cr+17Cu-1.08Ni-1.66Mn-3.67Si+4.52
C
+1.36Zr。
In order to ensure that the steel still has good heat conduction performance at high temperature (700 ℃), the heat conduction coefficient is in accordance with that of lambda 700℃ which is not more than 36.5 and not more than 38.5.
Wherein, the numerical value part of the element percentage is directly adopted in calculation.
In order to ensure that the steel has better high-temperature strength, the addition amount of C, cr, mo, ni, W, nb, ti, V, B alloy meets the requirement of the component range, and according to the contribution degree of each alloy element to the high-temperature strength, the addition amount of C, cr, mo, ni, W, nb, ti, V, B alloy also meets 14.5-18.5, wherein
X＝6C+4Cr+3.6Mo+2.8Ni+3.2W+24Nb+28Ti+3.5V+386B。
Compared with the prior art, the cold and hot fatigue resistant forged steel for the high-speed railway brake disc has excellent normal temperature performance, high temperature performance and cold and hot fatigue performance, and is suitable for manufacturing high-speed railway brake discs with the speed of 400 km/h and above.
Drawings
Fig. 1 shows a metallographic structure of cold and hot fatigue resistant wrought steel for a high-speed railway brake disc in example 1.
Detailed Description
The invention provides cold and hot fatigue resistant forged steel for a high-speed rail brake disc, which comprises ：C0.18％～0.25％、Si 0.15％～0.40％、Mn 0.40％～0.80％、Cr 1.00％～1.50％、Mo0.90％～1.20％、Ni 0.40％～0.60％、Zr：0.020％～0.030％、Nb 0.010％～0.040％、B：0.0006～0.0010％、W：0.20％～0.40％、Cu 0.22％～0.48％、Ti：0.040％～0.080％、V 0.25％～0.35％、Al 0.015％～0.040％、P≤0.015％、S≤0.010％、N≤0.0050％、T.O≤0.0012％, weight percent of Fe and other unavoidable impurities;
Wherein,
36.5≤λ700℃＝32.65+0.25W-2.2V+0.64Mo+0.35Cr+17Cu-1.08Ni-1.66Mn-3.67Si
+4.52C+1.36Zr≤38.5；
14.5≤X＝6C+4Cr+3.6Mo+2.8Ni+3.2W+24Nb+28Ti+3.5V+386B≤18.5。
The heat treatment method of the cold and hot fatigue resistant forged steel for the high-speed railway brake disc comprises the following steps of:
(1) Normalizing: heating the brake disc to 920-1020 ℃, preserving heat, and then air-cooling; through the normalizing treatment, the alloy elements in the steel for the brake disc are fully and uniformly dissolved, so that preparation is made for subsequent quenching and tempering;
(2) Quenching: heating the brake disc to 880-960 ℃, preserving heat, and then water-cooling to ensure that the austenite grain size in the steel is moderate;
(3) Tempering: heating the brake disc to 600-680 ℃, preserving heat, then air-cooling, eliminating internal structural stress through tempering, fully precipitating carbide in the steel, ensuring moderate carbide size, ensuring that the steel for the brake disc has excellent toughness matching, improving the structural stability of the steel in the quenching and rapid heating process, and improving the high-temperature performance of the steel.
In the normalizing process, the heating speed is 100-160 ℃/h, the heat preservation time t is determined by the thickness delta of a brake disc, t=1.5-2.5 delta, the unit of t is min, and the unit of delta is mm.
In the quenching process, the heating speed is 100-160 ℃/h, the heat preservation time t is determined by the thickness delta of a brake disc, t=1.0-1.2 delta, the unit of t is min, and the unit of delta is mm.
In the tempering process, the heating speed is 50-110 ℃/h, the heat preservation time t is determined by the thickness delta of the brake disc, t=2.0-4.0 delta, the unit of t is min, and the unit of delta is mm.
The production method of the cold and hot fatigue resistant forged steel for the high-speed railway brake disc comprises the following steps of: smelting in an arc furnace or a converter, refining in an LF furnace, vacuum degassing in RH or VD, continuous casting, heating in a casting blank heating furnace, rolling round steel for a brake disc, forging a brake disc blank, heat treatment, machining, flaw detection, packaging and warehousing, wherein the heat treatment process is carried out by adopting the heat treatment method.
The present invention will be described in detail with reference to examples.
The chemical compositions and weight percentages of the alloy forged steels for high-speed railway brake disks in the examples and comparative examples are shown in table 1.
Table 1 chemical composition (wt%) of examples and comparative examples
The production process of the alloy wrought steel for the high-speed railway brake disc in each example and comparative example is as follows:
Smelting in an electric furnace: oxygen is fixed before tapping, and steel retaining operation is adopted in the tapping process, so that slag discharging is avoided;
LF furnace: C. si, mn, cr, ni, mo, cu, nb, V, W, ti, B, zr and other elements are adjusted to target values;
Vacuum degassing: the pure degassing time is more than or equal to 15 minutes, the H content after vacuum treatment is less than or equal to 1.5ppm, and the phenomenon of hydrogen embrittlement caused by white spots in steel is avoided;
Continuous casting: the target temperature of the ladle molten steel is controlled to be 10-40 ℃ above the liquidus temperature, and round billets with phi 380-700 mm are continuously cast.
Rolling route: round billet heating, high-pressure water descaling, cogging, hot rolling round steel and slow cooling, wherein the rolling ratio during hot rolling is more than or equal to 3:1.
Forging route: round steel heating and brake disc blank forging.
Brake disc processing route: rough machining of a blank, normalizing, quenching and tempering heat treatment, finish machining, grinding, flaw detection, packaging and warehousing.
Wherein the heat treatment process is shown in table 2.
TABLE 2
Steel grade Heat treatment process
Example 1 Normalizing: air cooling at 930 ℃ for 2.5h, and quenching: water cooling at 900 ℃ for 1.5h, tempering: 620 ℃ x 4h air cooling
Example 2 Normalizing: air cooling at 1020 ℃ for 2.5h, and quenching: water cooling at 960 ℃ for 1.5h, tempering: 680 ℃ for 4h of air cooling
Example 3 Normalizing: air cooling at 960 ℃ for 2.5h, and quenching: 930 ℃ for 1.5h of water cooling, tempering: 650 ℃ 4h air cooling
Comparative example 1 Normalizing: air cooling at 930 ℃ for 2.5h, and quenching: water cooling at 900 ℃ for 1.5h, tempering: 620 ℃ x 4h air cooling
Comparative example 2 Normalizing: 950 ℃ for 2.5h of air cooling, quenching: 930 ℃ for 1.5h of water cooling, tempering: 640 ℃ 4h air cooling
Comparative example 3 Normalizing: air cooling at 1020 ℃ for 2.5h, and quenching: water cooling at 960 ℃ for 1.5h, tempering: 680 ℃ for 4h of air cooling
Comparative example 4 Normalizing: air cooling at 1000 ℃ for 2.5h, and quenching: 950 ℃ for 1.5h water cooling, tempering: 660 ℃ for 4h air cooling
Comparative example 5 Normalizing: 890 ℃ for 2.5h of air cooling, quenching: 860 ℃ for 1.5h water cooling, tempering: 580 ℃ x 4h air cooling
The mechanical properties of the alloy forged steel for high-speed railway brake disks in each example and comparative example are shown in table 3.
TABLE 3 Table 3
The service condition of the brake disc is simulated, the test sample is heated to 800 ℃, the test sample is quickly placed into water with the temperature of 20 ℃ after being kept warm for a period of time, and after repeated heating and cooling for 1000 times, whether cracks are generated or not is observed under a metallographic microscope. The cracking conditions for the examples and comparative examples are shown in Table 4.
TABLE 4 Cold and hot fatigue performance test cases list for examples and comparative examples of the present invention
The chemical composition and the production method of the alloy forged steel for the high-speed railway brake disc in the examples 1 to 3 are properly controlled, and the chemical composition ensures
1)
36.5≤λ700℃＝32.65+0.25W-2.2V+0.64Mo+0.35Cr+17Cu-1.08Ni-1.66Mn-3.67Si+4.52C+1.36Zr≤38.5；
2)
X=6% C+4% Cr+3.6% Mo+2.8% Ni+3.2% W+24% Nb+28% Ti+3.5% V+386% B is less than or equal to 18.5, and the steel has high normal temperature performance, high temperature performance and cold and hot fatigue performance, and may be used in high speed brake disc at speed of 400 km/hr or over.
Comparative examples 1 to 4 are unsuitable in chemical composition and the heat treatment processes of comparative examples 3 and 5 are unsuitable. Comparative example 1 was not properly controlled in chemical composition, but the materials were low in room temperature strength, poor in toughness, and low in high temperature strength, although lambda 700℃ and X values were both higher than the target ranges. The X value in comparative example 2 is lower, the chemical composition of comparative example 3 is unreasonable, and the heat treatment temperature is unreasonable, so that the overall performance of the material is not ideal. In comparative example 4, the thermal conductivity lambda 700℃ is high, but the final material strength cannot meet the requirement due to unreasonable control of components. Comparative example 5 has a reasonable chemical composition, but the heat treatment process is not reasonable, and the strength and cold and hot fatigue properties are also poor.
The foregoing detailed description of a cold and hot fatigue resistant wrought steel for high-speed railway brake discs, and a heat treatment method and production method thereof, with reference to the embodiments, is illustrative and not restrictive, and several embodiments may be listed in terms of the defined scope, thus variations and modifications without departing from the general inventive concept shall fall within the scope of protection of the present invention.

Claims (9)

1. The cold and hot fatigue resistant forged steel for the high-speed railway brake disc is characterized by comprising the following components in percentage by weight: c
0.18％～0.25％、Si 0.15％～0.40％、Mn 0.40％～0.80％、Cr 1.00％～1.50％、Mo 0.90％～1.20％、Ni 0.40％～0.60％、Zr：0.020％～0.030％、Nb 0.010％～
0.040％、B：0.0006～0.0010％、W：0.20％～0.40％、Cu 0.22％～0.48％、Ti：
0.040-0.080 Percent, 0.25-0.35 percent of V, 0.015-0.040 percent of Al, less than or equal to 0.015 percent of P, less than or equal to 0.010 percent of S, less than or equal to 0.0050 percent of N, less than or equal to 0.0012 percent of T.O, and the balance of Fe and other unavoidable impurities;
Wherein,
36.5≤λ700℃＝32.65+0.25W-2.2V+0.64Mo+0.35Cr+17Cu-1.08Ni-1.66Mn-3.67Si+4.52C+1.36Zr≤38.5；
14.5≤X＝6C+4Cr+3.6Mo+2.8Ni+3.2W+24Nb+28Ti+3.5V+386B≤18.5；
The heat treatment method of the cold and hot fatigue resistant forged steel for the high-speed railway brake disc comprises the following steps of:
(1) Normalizing: heating the brake disc to 920-1020 ℃, preserving heat, and then air-cooling;
(2) Quenching: heating the brake disc to 880-960 ℃, preserving heat, and then water-cooling;
(3) Tempering: heating the brake disc to 600-680 ℃, preserving heat, and then air-cooling.
2. The cold and hot fatigue resistant forged steel for high-speed railway brake disks according to claim 1, wherein the metallographic structure of the cold and hot fatigue resistant forged steel for high-speed railway brake disks is tempered sorbite.
3. The cold and hot fatigue resistant forged steel for high-speed railway brake disks according to claim 1, wherein the tensile strength of the cold and hot fatigue resistant forged steel for high-speed railway brake disks is not less than 1250MPa, the yield strength is not less than 1150MPa,
A is more than or equal to 18%, Z is more than or equal to 65%, KV2 is more than or equal to 150J at 20 ℃, and tensile strength at 700 ℃ is more than or equal to 640MPa; after 1000 times of cold and hot circulation at 800-20 ℃, no crack is generated.
4. A heat treatment method of cold and hot fatigue resistant wrought steel for high-speed railway brake discs according to any one of claims 1-3, characterized in that the heat treatment method comprises the steps of:
(1) Normalizing: heating the brake disc to 920-1020 ℃, preserving heat, and then air-cooling;
(2) Quenching: heating the brake disc to 880-960 ℃, preserving heat, and then water-cooling;
(3) Tempering: heating the brake disc to 600-680 ℃, preserving heat, and then air-cooling.
5. The heat treatment method according to claim 4, wherein in the normalizing process, the heating rate is 100-160 ℃/h, the holding time t is determined by the thickness δ of the brake disc, t=1.5-2.5 δ, t is in min, and δ is in mm.
6. The heat treatment method according to claim 4, wherein in the quenching process, the heating rate is 100-160 ℃/h, the holding time t is determined by the thickness delta of the brake disc, t=1.0-1.2 delta, t is in min, and delta is in mm.
7. The heat treatment method according to claim 4, wherein in the tempering process, the heating rate is 50-110 ℃/h, the holding time t is determined by the thickness δ of the brake disc, t=2.0-4.0 δ, t is in min, and δ is in mm.
8. A method for producing cold and hot fatigue resistant forged steel for high-speed railway brake discs according to any one of claims 1-3, characterized in that the production method comprises the steps of: smelting in an arc furnace or a converter, refining in an LF furnace, vacuum degassing in RH or VD, continuous casting, heating in a casting blank heating furnace, rolling round steel for a brake disc, forging a brake disc blank, heat treatment, machining, flaw detection, packaging and warehousing.
9. The production method according to claim 8, wherein the heat treatment process is performed by the heat treatment method according to any one of claims 4 to 7.
CN202310046192.9A 2023-01-31 2023-01-31 Cold and hot fatigue resistant forged steel for high-speed railway brake disc and heat treatment method and production method thereof Active CN116043115B (en)

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