WO2022126862A1 - Cryogenic steel and heat treatment process therefor - Google Patents

Cryogenic steel and heat treatment process therefor Download PDF

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WO2022126862A1
WO2022126862A1 PCT/CN2021/078443 CN2021078443W WO2022126862A1 WO 2022126862 A1 WO2022126862 A1 WO 2022126862A1 CN 2021078443 W CN2021078443 W CN 2021078443W WO 2022126862 A1 WO2022126862 A1 WO 2022126862A1
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temperature
low
isothermal
heat treatment
treatment process
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PCT/CN2021/078443
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French (fr)
Chinese (zh)
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李伟
金学军
李勇
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上海交通大学
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    • C—CHEMISTRY; METALLURGY
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • C21D1/20—Isothermal quenching, e.g. bainitic hardening
    • C—CHEMISTRY; METALLURGY
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

Definitions

  • the invention belongs to the technical field of low-temperature steel, and relates to a precipitation-strengthened low-temperature steel and a heat treatment process thereof, in particular to a nickel-saving nanometer precipitation-strengthened low-temperature steel and a pre-precipitation-double-partition heat treatment process.
  • the strengthening method of refining grains and introducing dislocations by cold deformation is not suitable for thick materials, thus greatly limiting the large-scale industrial application of materials.
  • the purpose of the present invention is to provide a kind of low-temperature steel and its heat treatment process.
  • the steel is used to solve the problem of the lack of ultra-low carbon and low nickel type low temperature steel with good low temperature strength and toughness combination in the prior art and a preparation method thereof.
  • a first aspect of the present invention provides a kind of low-temperature steel, which is made up of the elements of the following mass percentages:
  • the above-mentioned low temperature steel also includes inevitable impurities.
  • the unavoidable impurities are trace impurity elements that are inevitably contaminated during the preparation process of the low-temperature steel.
  • the low temperature steel is composed of the following elements by mass percentage:
  • the low temperature steel is composed of the following elements by mass percentage:
  • the elemental composition of the low-temperature steel in the present invention can improve the economic benefits of the nickel-based ferritic low-temperature steel and its low-temperature strong plasticity, wherein:
  • the reduction of C element can reduce the austenite stabilized by C element, improve the stability of austenite, at the same time, the reduction of C element can also ensure the welding performance of the material; at the same time, the reduction of Ni element can greatly reduce the cost;
  • the above-mentioned precipitation strengthening is realized based on the NiAl and copper-rich phases in which Al and Cu elements and Ni elements form high-density nano-precipitation phases, and the precipitation strengthening effect further improves the strength of the material.
  • the second aspect of the present invention provides a heat treatment process for low-temperature steel.
  • the element components are mixed according to the proportions and then smelted, and then slabs are continuously cast into ingots, followed by hot rolling treatment, and the obtained ingots are tempered and pre-precipitated. quenching, and then perform the first two-phase zone isothermal water quenching and the second two-phase zone isothermal water quenching in sequence, so as to provide the low-temperature steel.
  • the smelting is a conventional iron and steel smelting process.
  • the slab continuous casting is a conventional steel casting process.
  • the ingot needs to be derusted, degreasing and cleaned before the hot rolling treatment. Avoid uneven stress during hot rolling.
  • the hot rolling treatment is to perform multi-step hot rolling of the ingot from the preliminary rolling temperature to the final rolling temperature and then air-cool the ingot.
  • the blooming temperature is 1150-1250°C.
  • the finish rolling temperature is 700-800°C.
  • the multi-step hot rolling includes the following steps:
  • the first step hot rolling temperature: 1150-1250 °C, holding time: 115-125 minutes;
  • the second step hot rolling temperature: 880-970 °C, holding time: 65-75 minutes;
  • the third step hot rolling temperature: 700-800 °C, holding time: 20-30 minutes.
  • each reduction ratio of the multi-step hot rolling is maintained at 20-30%.
  • the reduction ratio is a commonly used parameter representing relative deformation during forging and rolling.
  • the tempering temperature is in the range from A1 temperature to 50-120 °C below A1 temperature
  • A1 is the A1 critical point temperature, that is, in an equilibrium state, austenite, ferrite, carburizing The temperature at which body equilibrium coexists.
  • the tempering temperature is in the range of 50-100° C. below the A 1 temperature to the A 1 temperature.
  • the tempering time is 0.5-1.5h. More preferably, the tempering time is 0.5-1.0h.
  • the isothermal temperature of the first two-phase zone isothermal temperature is in the range of 20-100° C. above the temperature of A 1 to the temperature of A 1 .
  • the isothermal temperature of the first two-phase zone isothermal temperature is in the range of 50-80° C. above the temperature of A 1 to the temperature of A 1 .
  • the above - mentioned A1 temperature is 620-670°C.
  • the isothermal temperature of the first two-phase zone isothermal is higher than the isothermal temperature of the second two-phase zone isothermal temperature by 30-40°C.
  • the higher isothermal temperature of the first two-phase zone isothermal is to obtain more fresh martensite before the second two-phase zone isothermal to optimize the interfacial coherence of the reversed austenite and ferrite matrix .
  • the isothermal time of the first two-phase zone isothermal and the second two-phase zone isothermal time are both 0.5-1.5 h.
  • the isothermal time of the first two-phase zone isothermal and the second two-phase zone isothermal time are both 0.5-1.0 h.
  • the water quenching is to water-cool the tempered or isothermally treated ingot to room temperature.
  • the above room temperature is 20-25°C.
  • a kind of precipitation-strengthened low-temperature steel and heat treatment process thereof provided by the present invention adopts multi-step isothermal quenching to achieve pre-precipitation-double-partition process, and by selecting suitable isothermal temperature and holding time, in the first step of reclamation
  • the second step a small amount of retained austenite and fresh martensite are obtained by the first two-phase zone isothermal
  • the third step is the second two-phase zone isothermal to achieve austenite inversion.
  • Phase transformation and Mn element distribution through the combined effect of nano-precipitation phase and austenite, obtain a nickel-saving nano-precipitation-strengthened low-temperature steel with both low-temperature strong plasticity and toughness.
  • the first step of pre-precipitation plays a role of precipitation strengthening by introducing nano-precipitation phase on the one hand, and local segregation of Mn element is realized by the enrichment of Mn element near the precipitation phase on the other hand.
  • the synergistic precipitation of the NiAl phase and the Cu-rich phase increases the strength without reducing the toughness, and at the same time, due to the higher binding enthalpy of Mn element, Cu and Ni elements, local segregation of Mn element can be achieved.
  • the replacement of some Ni elements by Mn elements can significantly improve the strength and plasticity of steel, reduce costs, and improve economic benefits.
  • part of the retained austenite obtained by the isothermal treatment of the first two-phase region in the second step will further generate fresh martensite due to the lack of austenite stabilizing elements in the subsequent quenching process.
  • these fresh martensites optimize the interfacial coherence between the reversed austenite and the ferrite matrix during the isothermal process of the second two-phase region in the third step, thereby improving the mechanical stability of the retained austenite.
  • the low-temperature steel and the heat treatment process thereof provided by the invention adopt the pre-precipitation-double-partition process, utilize the TRIP effect of the retained austenite and the precipitation strengthening of the nano-precipitate phase in the stretching process, and can prepare the yield strength at a temperature of -196° C. 940-980MPa, 1300-1400MPa tensile strength, 30-40% elongation and 45,000-48,000MPa% high-strength plastic nickel-section nano-precipitation-strengthened low-temperature steel, without cold deformation treatment, can adapt to mass production.
  • the precipitation-induced reverse phase transformation is used to optimize the interface coherence between the retained austenite and the ferrite matrix, and the TRIP effect of the retained austenite and the nanometer precipitation of NiAl and copper-rich are utilized.
  • the strengthening effect of particles can prepare nickel-saving low-temperature steel with both strong plasticity and low-temperature toughness, with low application cost, simple heat treatment process and strong economical applicability.
  • Fig. 1 shows the scanning microstructure comparison of low-temperature steel obtained after pre-precipitation and double-partition heat treatment without pre-precipitation in the present invention. Scanning microstructure of steel; Figure 1b is a scanning microstructure of low-temperature steel without pre-precipitation in Comparative Example 1.
  • Fig. 2 shows the coherence relationship statistics of the dual-phase interface of low-temperature steel obtained after pre-precipitation and double-partition heat treatment without pre-precipitation in the present invention, wherein Fig. 2a shows the pre-precipitation-double-partition in Example 1
  • Figure 2b is a coherent relationship statistical diagram of the low-temperature steel dual-phase interface without pre-precipitation in Comparative Example 1.
  • the raw materials containing carbon, nickel, manganese, aluminum, copper, sulfur, phosphorus, nitrogen, oxygen, calcium, iron and other elements used in the following examples can be purchased from the market to achieve smelting, continuous slab casting, hot rolling, Equipment for tempering, isothermal treatment, water quenching and other processes can also be purchased from the market.
  • each component is composed of the following elements by mass percentage: C: 0.008-0.012%; Ni: 2.0-3.0%; 8.0%; Al: 1.5-2.0%; Cu: 2.5-3.0%; S: ⁇ 0.004%; P: ⁇ 0.003%; N: 0.003-0.005%; O: 0.0005-0.001%; Ca: 0.0005-0.005%; The balance is Fe. Remove rust and oil from the ingot, and clean it to avoid uneven stress during the hot rolling process.
  • the ingot is subjected to hot rolling treatment, and is subjected to multi-step hot rolling from a preliminary rolling temperature of 1200 °C to a final rolling temperature of 750 °C, followed by air cooling.
  • the steps of the multi-step hot rolling are as follows: successively at temperatures of 1200, 900 and 750° C., the reduction rates are respectively 25%, 25% and 25%, and the holding times are respectively 120, 70 and 30 minutes.
  • the hot-rolled steel ingot is kept at 50-100° C. below the A1 temperature for 0.5-1.0 h for tempering and pre - precipitation, and then water-cooled to room temperature for water quenching. Then, at 50-80°C above the A1 temperature, the first two-phase zone is isothermally held for 0.5-1.0h, and then water-cooled to room temperature for water quenching. Finally, carry out the second two-phase zone isothermal heat preservation for 0.5-1.5h, the isothermal temperature of the second two-phase zone isothermal temperature is lower than that of the first two-phase zone isothermal temperature by 30-40°C, and then water-cooled to room temperature for water quenching, Obtain low temperature steel sample 1#. The above A1 temperature is 620-670 °C. Room temperature is 20-25°C.
  • each component is composed of the following elements by mass percentage: C: 0.008%; Ni: 2.0%; Mn: 7.0%; Al: 1.5 %; Cu: 2.0%; S: 0.004%; P: 0.003%; N: 0.003%; O: 0.0005%; Ca: 0.0005%; Remove rust and oil from the ingot, and clean it to avoid uneven stress during the hot rolling process.
  • the ingot is subjected to hot rolling treatment, and is subjected to multi-step hot rolling from a preliminary rolling temperature of 1200 °C to a final rolling temperature of 750 °C, followed by air cooling.
  • the steps of the multi-step hot rolling are as follows: continuously at temperatures of 1150, 850, and 770° C., the reduction rates are 30%, 25%, and 25%, respectively, and the holding time is 115, 65, and 25 minutes, respectively.
  • the hot-rolled ingot is kept at 50°C below the A1 temperature for 1.0 h for tempering and pre-precipitation, and then water-cooled to room temperature for water quenching.
  • the first two-phase zone isothermal heat preservation was carried out at 80 °C above the A1 temperature for 0.5 h, and then water-cooled to room temperature for water quenching.
  • the second isothermal temperature in the two-phase zone is carried out for 1.0 h.
  • the isothermal temperature of the second two-phase zone is lower than the isothermal temperature of the first two-phase zone by 40°C, and then water-cooled to room temperature for water quenching to obtain low-temperature steel.
  • the above - mentioned A1 temperature is 630°C. Room temperature is 20-25°C.
  • each component is composed of the following elements by mass percentage: C: 0.01%; Ni: 2.5%; Mn: 7.0%; Al: 2.0 %; Cu: 2.5%; S: 0.004%; P: 0.003%; N: 0.003%; O: 0.0005%; Ca: 0.0005%; Remove rust and oil from the ingot, and clean it to avoid uneven stress during the hot rolling process.
  • the ingot is subjected to hot rolling treatment, and is subjected to multi-step hot rolling from a preliminary rolling temperature of 1200 °C to a final rolling temperature of 750 °C, followed by air cooling.
  • the steps of the multi-step hot rolling are as follows: continuously at temperatures of 1180, 880 and 760° C., the reduction rates are respectively 25%, 25% and 30%, and the holding times are respectively 125, 65 and 30 minutes.
  • the hot-rolled steel ingot is kept at 80°C below the A1 temperature for 1.0 h for tempering and pre-precipitation, and then water-cooled to room temperature for water quenching.
  • the first two-phase zone isothermal heat preservation was carried out at 80 °C above the A1 temperature for 0.5 h, and then water-cooled to room temperature for water quenching.
  • the second isothermal temperature in the two-phase zone is carried out for 1.0 h.
  • the isothermal temperature of the second two-phase zone is lower than the isothermal temperature of the first two-phase zone by 40°C, and then water-cooled to room temperature for water quenching to obtain low-temperature steel.
  • Sample 3# The above - mentioned A1 temperature is 620°C. Room temperature is 20-25°C.
  • each component is composed of the following elements by mass percentage: C: 0.008-0.012%; Ni: 2.0-3.0%; 8.0%; Al: 1.5-2.0%; Cu: 2.5-3.0%; S: ⁇ 0.004%; P: ⁇ 0.003%; N: 0.003-0.005%; O: 0.0005-0.001%; Ca: 0.0005-0.005%; The balance is Fe. Remove rust and oil from the ingot, and clean it to avoid uneven stress during the hot rolling process.
  • the ingot is subjected to hot rolling treatment, and is subjected to multi-step hot rolling from a preliminary rolling temperature of 1200 °C to a final rolling temperature of 750 °C, followed by air cooling.
  • the steps of the multi-step hot rolling are as follows: continuously at temperatures of 1200, 900 and 750° C., the reduction rates are respectively 25%, 25% and 25%, and the holding times are respectively 120, 60 and 30 minutes.
  • the hot-rolled steel ingot is kept at 50-80° C. below the A1 temperature for 0.5-1.0 h for tempering and pre - precipitation, and then water-cooled to room temperature for water quenching. Then, the two-phase zone is isothermally held at 50-70°C above the A1 temperature for 0.5-1.5h , and then water-cooled to room temperature for water quenching to obtain a low-temperature steel comparative sample 1*.
  • the above - mentioned A1 temperature is 620-670°C. Room temperature is 20-25°C.
  • Example 1 The low-temperature steel sample 1# obtained in Example 1 and the low-temperature steel comparative sample 1* obtained in Comparative Example 1 were subjected to tensile experiments at room temperature and low temperature, respectively.
  • the specific results are shown in Table 1. It can be seen from Table 1 that compared with the low-temperature steel without pre-precipitation, it is mainly due to the TRIP effect induced by retained austenite and the synergistic strengthening effect of the nano-precipitation phase.
  • the ultra-low temperature strength and plasticity have been greatly improved, and it can prepare high-strength-plastic product nickel-type nanometers with a yield strength of 940-980MPa, a tensile strength of 1300-1400MPa, an elongation of 30-40%, and a strong-plastic product of 49000-63000MPa% at -196°C.
  • Precipitation strengthened low temperature steel Precipitation strengthened low temperature steel.
  • the content of retained austenite was measured by X-ray diffraction experiments on the low-temperature steel sample 1# obtained in Example 1 and the low-temperature steel comparative sample 1* obtained in Comparative Example 1. The specific results are shown in Table 2. The two samples were characterized by scanning electron microscopy, and the specific results are shown in Figures 1a and 1b.
  • the structure treated by the pre-precipitation-double partition process has both retained austenite, ferrite (tempered martensite) and nano-precipitated phases, and the grain size is effectively refined, After multi-step heat treatment, the nano-precipitate phase is dispersed in the matrix, which plays an effective strengthening role.
  • the microstructure of the low-temperature steel without pre-precipitation process is similar to the former, and the matrix structure is a complex structure of tempered martensite and nano-precipitated phase.
  • the low-temperature steel sample 1# obtained in Example 1 and the low-temperature steel comparative sample 1* obtained in Comparative Example 1 were subjected to a statistical analysis of the interface orientation relationship by electron backscatter diffraction (EBSD).
  • EBSD electron backscatter diffraction
  • the precipitation-strengthened low-temperature steel and its heat treatment process provided by the present invention can obtain a nickel-saving nano-precipitation-strengthened low-temperature steel with both low-temperature strong plasticity and toughness, with low application cost and no need for cold deformation Treatment, the heat treatment process is simple, and the economical applicability is strong. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

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Abstract

Provided is cryogenic steel. The cryogenic steel is composed of the following elements in percentage by mass: 0.005%-0.015% of C, 1.5%-4.5% of Ni, 5.0%-10.0% of Mn, 1.0%-3.0% of Al, 1.5%-3.0% of Cu, less than or equal to 0.004% of S, less than or equal to 0.003% of P, 0.003%-0.005% of N, 0.0005%-0.001% of O, 0.0005-0.005% of Ca and the balance being Fe. Further provided is a heat treatment process for the cryogenic steel. By means of the cryogenic steel and the heat treatment process thereof provided in the present invention, nickel-saving and nanoprecipitation-strengthened cryogenic steel with high low-temperature plasticity and toughness can be obtained, the application cost is low, cold deformation treatment is not required, the heat treatment process is simple, and has high economic applicability.

Description

一种低温用钢及其热处理工艺A kind of low temperature steel and its heat treatment process 技术领域technical field
本发明属于低温用钢的技术领域，涉及一种析出强化的低温用钢及其热处理工艺，具体涉及一种节镍型纳米析出强化的低温用钢及其预析出-双配分热处理工艺。The invention belongs to the technical field of low-temperature steel, and relates to a precipitation-strengthened low-temperature steel and a heat treatment process thereof, in particular to a nickel-saving nanometer precipitation-strengthened low-temperature steel and a pre-precipitation-double-partition heat treatment process.
背景技术Background technique
随着海洋钻井平台、海底油气输送与油气储运等装备制造的快速发展，在海洋环境下使用的低温用特殊钢的需求量显著上升。以液化天然气(LNG)为例，LNG运输船所用到的材料一方面需要有较高的低温强塑性，另一方面则需要兼具低温韧性和止裂能力。在富Ni铁素体型低温钢中，目前应用较为成熟的是9Ni钢。因为Ni元素成本高，故这类低温钢在现阶段同时面临需要提升性能和降低成本的问题。With the rapid development of equipment manufacturing such as offshore drilling platforms, submarine oil and gas transportation and oil and gas storage and transportation, the demand for special steel for low temperature used in the marine environment has increased significantly. Taking liquefied natural gas (LNG) as an example, the materials used in LNG carriers need to have high low-temperature strong plasticity on the one hand, and low-temperature toughness and crack arrest ability on the other hand. Among Ni-rich ferritic low-temperature steels, 9Ni steel is currently the most mature application. Because of the high cost of Ni element, this kind of low-temperature steel is facing the problem of improving performance and reducing cost at the same time.
特别的，在性能方面，现有技术中，为保证良好的低温塑性，需要引入一定量的残余奥氏体，进而激发相变诱发塑性(TRIP)效应。残余奥氏体的热稳定性和机械稳定性是维持TRIP效应的关键因素，常规的淬火-配分(QP)或淬火-配分-回火(QPT)工艺是利用C元素在马氏体和奥氏体之间的配分实现奥氏体稳定化。同时，众所周知，通过冷变形细化晶粒和引入位错是提高强度的有效途径。然而，上述工艺至少带来以下技术问题：In particular, in terms of performance, in the prior art, in order to ensure good low-temperature plasticity, it is necessary to introduce a certain amount of retained austenite, thereby stimulating the transformation-induced plasticity (TRIP) effect. The thermal and mechanical stability of retained austenite is the key factor to maintain the TRIP effect. The conventional quenching-partitioning (QP) or quenching-partitioning-tempering (QPT) process utilizes C in martensite and austenite. The partition between the bodies achieves austenite stabilization. Meanwhile, it is well known that grain refinement and introduction of dislocations through cold deformation are effective ways to improve strength. However, the above process brings at least the following technical problems:
1、通过C元素稳定的奥氏体在低温下的机械稳定性往往较低，并且过量的C元素引起的淬透性增加会进一步增大焊接时的热影响区，降低材料的焊接性能。1. The mechanical stability of austenite stabilized by C element at low temperature is often low, and the increase in hardenability caused by excess C element will further increase the heat-affected zone during welding and reduce the welding performance of the material.
2、通过冷变形细化晶粒和引入位错这种强化方式不适合用于较厚的材料，因此极大地限制了材料的大规模工业化应用。2. The strengthening method of refining grains and introducing dislocations by cold deformation is not suitable for thick materials, thus greatly limiting the large-scale industrial application of materials.
发明内容SUMMARY OF THE INVENTION
鉴于以上所述现有技术的缺点，本发明的目的在于提供一种低温用钢及其热处理工艺，通过成分的科学设计，利用Mn元素在析出过程中的局部偏聚诱导逆相变，改良残余奥氏体与铁素体基体的界面共格性，同时在奥氏体中引入Mn元素浓度梯度，提高残余奥氏体的机械稳定性，制备出一种低温强塑性和韧性兼具的低温用钢，用于解决现有技术中缺乏具有良好的低温强韧性组合且能够用于低温环境下使用的超低碳低镍型低温钢及其制备方法的问题。In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a kind of low-temperature steel and its heat treatment process. The interfacial coherence between austenite and ferrite matrix, and the introduction of Mn element concentration gradient in austenite to improve the mechanical stability of retained austenite, and prepare a low-temperature alloy with both low-temperature strong plasticity and toughness. The steel is used to solve the problem of the lack of ultra-low carbon and low nickel type low temperature steel with good low temperature strength and toughness combination in the prior art and a preparation method thereof.
为实现上述目的及其他相关目的，本发明第一方面提供一种低温用钢，由以下质量百分 比的元素组成：For achieving the above-mentioned purpose and other related purposes, a first aspect of the present invention provides a kind of low-temperature steel, which is made up of the elements of the following mass percentages:
C(碳)：0.005-0.015％；Ni(镍)：1.5-4.5％；Mn(锰)：5.0-10.0％；Al(铝)：1.0-3.0％；Cu(铜)：1.5-3.0％；S(硫)：≤0.004％；P(磷)：≤0.003％；N(氮)：0.003-0.005％；O(氧)：0.0005-0.001％；Ca(钙)：0.0005-0.005％；余量为Fe(铁)。C (carbon): 0.005-0.015%; Ni (nickel): 1.5-4.5%; Mn (manganese): 5.0-10.0%; Al (aluminum): 1.0-3.0%; Cu (copper): 1.5-3.0%; S (sulfur): ≤ 0.004%; P (phosphorus): ≤ 0.003%; N (nitrogen): 0.003-0.005%; O (oxygen): 0.0005-0.001%; Ca (calcium): 0.0005-0.005%; balance For Fe (iron).
上述低温用钢中还包括不可避免的杂质。所述不可避免的杂质是低温用钢在制备过程中不可避免沾染的微量杂质元素。The above-mentioned low temperature steel also includes inevitable impurities. The unavoidable impurities are trace impurity elements that are inevitably contaminated during the preparation process of the low-temperature steel.
优选地，所述低温用钢，由以下质量百分比的元素组成：Preferably, the low temperature steel is composed of the following elements by mass percentage:
C(碳)：0.008-0.012％；Ni(镍)：1.5-3.0％；Mn(锰)：7.0-10.0％；Al(铝)：1.0-2.0％；Cu(铜)：2.0-3.0％；S(硫)：0.001-0.004％；P(磷)：0.001-0.003％；N(氮)：0.003-0.005％；O(氧)：0.0005-0.001％；Ca(钙)：0.0005-0.005％；余量为Fe(铁)。C (carbon): 0.008-0.012%; Ni (nickel): 1.5-3.0%; Mn (manganese): 7.0-10.0%; Al (aluminum): 1.0-2.0%; Cu (copper): 2.0-3.0%; S (sulfur): 0.001-0.004%; P (phosphorus): 0.001-0.003%; N (nitrogen): 0.003-0.005%; O (oxygen): 0.0005-0.001%; Ca (calcium): 0.0005-0.005%; The balance is Fe (iron).
更优选地，所述低温用钢，由以下质量百分比的元素组成：More preferably, the low temperature steel is composed of the following elements by mass percentage:
C(碳)：0.008-0.012％；Ni(镍)：1.5-2.5％；Mn(锰)：7.0-8.0％；Al(铝)：1.5-2.0％；Cu(铜)：2.5-3.0％；S(硫)：0.002-0.004％；P(磷)：0.002-0.003％；N(氮)：0.003-0.005％；O(氧)：0.0005-0.001％；Ca(钙)：0.0005-0.005％；余量为Fe(铁)。C (carbon): 0.008-0.012%; Ni (nickel): 1.5-2.5%; Mn (manganese): 7.0-8.0%; Al (aluminum): 1.5-2.0%; Cu (copper): 2.5-3.0%; S (sulfur): 0.002-0.004%; P (phosphorus): 0.002-0.003%; N (nitrogen): 0.003-0.005%; O (oxygen): 0.0005-0.001%; Ca (calcium): 0.0005-0.005%; The balance is Fe (iron).
本发明中低温用钢的元素组成能够提高镍系铁素体低温钢经济效益及其低温强塑性，其中：The elemental composition of the low-temperature steel in the present invention can improve the economic benefits of the nickel-based ferritic low-temperature steel and its low-temperature strong plasticity, wherein:
添加6％以上Mn元素作为奥氏体稳定元素，从而大幅减少C元素和Ni元素含量；具体的，C元素的减少能够减少通过C元素稳定的奥氏体，提高了奥氏体的稳定性，同时C元素的减少也能保证材料的焊接性能；同时，Ni元素的减少能够大幅降低成本；Adding more than 6% Mn element as austenite stabilizing element, thereby greatly reducing the content of C element and Ni element; specifically, the reduction of C element can reduce the austenite stabilized by C element, improve the stability of austenite, At the same time, the reduction of C element can also ensure the welding performance of the material; at the same time, the reduction of Ni element can greatly reduce the cost;
同时加入适量Al和Cu元素从而引入析出强化效应并且引起Mn元素的局部偏聚，从而起到提高局部逆相变驱动力的作用，更重要的是，基于局部正逆相变的奥氏体记忆效应是优化双相界面共格性的有效途径，从而起到提高残余奥氏体的机械稳定性的作用。At the same time, adding an appropriate amount of Al and Cu elements to introduce the precipitation strengthening effect and cause the local segregation of Mn elements, thereby improving the driving force of local reverse transformation. More importantly, the austenite memory based on local forward and reverse transformation The effect is an effective way to optimize the coherence of the dual-phase interface, thereby improving the mechanical stability of the retained austenite.
上述析出强化是基于Al和Cu元素与Ni元素形成高密度纳米析出相的NiAl和富铜相实现的，析出强化效应进一步提高了材料的强度。The above-mentioned precipitation strengthening is realized based on the NiAl and copper-rich phases in which Al and Cu elements and Ni elements form high-density nano-precipitation phases, and the precipitation strengthening effect further improves the strength of the material.
本发明第二方面提供一种低温用钢的热处理工艺，按配比取各元素组分混合后冶炼，再板坯连铸成铸锭，进行热轧处理，获得的钢锭进行回火预析出后水淬，再依次进行第一次两相区等温后水淬、第二次两相区等温后水淬，以提供所述低温用钢。The second aspect of the present invention provides a heat treatment process for low-temperature steel. The element components are mixed according to the proportions and then smelted, and then slabs are continuously cast into ingots, followed by hot rolling treatment, and the obtained ingots are tempered and pre-precipitated. quenching, and then perform the first two-phase zone isothermal water quenching and the second two-phase zone isothermal water quenching in sequence, so as to provide the low-temperature steel.
优选地，所述冶炼为常规的钢铁冶炼工艺。Preferably, the smelting is a conventional iron and steel smelting process.
优选地，所述板坯连铸为常规的钢铁铸造工艺。Preferably, the slab continuous casting is a conventional steel casting process.
优选地，所述铸锭在热轧处理前需要除锈去油、清洗干净。避免热轧处理过程中的受力 不均现象。Preferably, the ingot needs to be derusted, degreasing and cleaned before the hot rolling treatment. Avoid uneven stress during hot rolling.
优选地，所述热轧处理是将铸锭由初轧温度至终轧温度进行多步热轧后空冷。Preferably, the hot rolling treatment is to perform multi-step hot rolling of the ingot from the preliminary rolling temperature to the final rolling temperature and then air-cool the ingot.
更优选地，所述初轧温度为1150-1250℃。More preferably, the blooming temperature is 1150-1250°C.
更优选地，所述终轧温度为700-800℃。More preferably, the finish rolling temperature is 700-800°C.
更优选地，所述多步热轧包括以下步骤：More preferably, the multi-step hot rolling includes the following steps:
第一步：热轧温度：1150-1250℃，保温时间：115-125分钟；The first step: hot rolling temperature: 1150-1250 ℃, holding time: 115-125 minutes;
第二步：热轧温度：880-970℃，保温时间：65-75分钟；The second step: hot rolling temperature: 880-970 ℃, holding time: 65-75 minutes;
第三步：热轧温度：700-800℃，保温时间：20-30分钟。The third step: hot rolling temperature: 700-800 ℃, holding time: 20-30 minutes.
更优选地，所述多步热轧的每次压下率保持在20-30％。More preferably, each reduction ratio of the multi-step hot rolling is maintained at 20-30%.
所述压下率是锻压和轧制时常用的表示相对变形的参数。当多步轧制压下率尽量维持在一个稳定范围内时，轧制效果较好。The reduction ratio is a commonly used parameter representing relative deformation during forging and rolling. When the multi-step rolling reduction rate is maintained within a stable range as much as possible, the rolling effect is better.
优选地，所述回火的温度为A 1温度至A 1温度以下50-120℃区间，所述A 1为A 1临界点温度，即平衡状态下，奥氏体、铁素体、渗碳体平衡共存的温度。 Preferably, the tempering temperature is in the range from A1 temperature to 50-120 °C below A1 temperature, and A1 is the A1 critical point temperature, that is, in an equilibrium state, austenite, ferrite, carburizing The temperature at which body equilibrium coexists.
更优选地，所述回火的温度为A 1温度至A 1温度以下50-100℃区间。 More preferably, the tempering temperature is in the range of 50-100° C. below the A 1 temperature to the A 1 temperature.
优选地，所述回火的时间为0.5-1.5h。更优选地，所述回火的时间为0.5-1.0h。Preferably, the tempering time is 0.5-1.5h. More preferably, the tempering time is 0.5-1.0h.
优选地，所述第一次两相区等温的等温温度为A 1温度至A 1温度以上20-100℃区间。 Preferably, the isothermal temperature of the first two-phase zone isothermal temperature is in the range of 20-100° C. above the temperature of A 1 to the temperature of A 1 .
进一步优选地，所述第一次两相区等温的等温温度为A 1温度至A 1温度以上50-80℃区间。 Further preferably, the isothermal temperature of the first two-phase zone isothermal temperature is in the range of 50-80° C. above the temperature of A 1 to the temperature of A 1 .
上述A 1温度为620-670℃。 The above - mentioned A1 temperature is 620-670°C.
优选地，所述第一次两相区等温的等温温度高于所述第二次两相区等温的等温温度30-40℃。更高的第一次两相区等温的等温温度是为了在第二次两相区等温之前获得更多的新鲜马氏体，以优化逆变奥氏体和铁素体基体的界面共格性。Preferably, the isothermal temperature of the first two-phase zone isothermal is higher than the isothermal temperature of the second two-phase zone isothermal temperature by 30-40°C. The higher isothermal temperature of the first two-phase zone isothermal is to obtain more fresh martensite before the second two-phase zone isothermal to optimize the interfacial coherence of the reversed austenite and ferrite matrix .
优选地，所述第一次两相区等温和第二次两相区等温的等温时间均为0.5-1.5h。Preferably, the isothermal time of the first two-phase zone isothermal and the second two-phase zone isothermal time are both 0.5-1.5 h.
更优选地，所述第一次两相区等温和第二次两相区等温的等温时间均为0.5-1.0h。More preferably, the isothermal time of the first two-phase zone isothermal and the second two-phase zone isothermal time are both 0.5-1.0 h.
优选地，所述水淬是将回火或等温处理后的钢锭进行水冷却至室温。上述室温为20-25℃。Preferably, the water quenching is to water-cool the tempered or isothermally treated ingot to room temperature. The above room temperature is 20-25°C.
如上所述，本发明提供的一种析出强化的低温用钢及其热处理工艺，采用多步等温淬火达到预析出-双配分工艺，通过选取合适的等温温度和保温时间，在实现第一步回火得到纳米析出相和Mn元素的局部偏聚，第二步第一次两相区等温得到少量残余奥氏体和新鲜马氏体，第三步第二次两相区等温实现奥氏体逆相变和Mn元素配分，通过纳米析出相和奥氏体的综合效应，得到一种低温强塑性和韧性兼具的节镍型纳米析出强化低温钢。As mentioned above, a kind of precipitation-strengthened low-temperature steel and heat treatment process thereof provided by the present invention adopts multi-step isothermal quenching to achieve pre-precipitation-double-partition process, and by selecting suitable isothermal temperature and holding time, in the first step of reclamation In the second step, a small amount of retained austenite and fresh martensite are obtained by the first two-phase zone isothermal, and the third step is the second two-phase zone isothermal to achieve austenite inversion. Phase transformation and Mn element distribution, through the combined effect of nano-precipitation phase and austenite, obtain a nickel-saving nano-precipitation-strengthened low-temperature steel with both low-temperature strong plasticity and toughness.
其中，第一步预析出一方面通过引入纳米析出相起到析出强化的作用，另一方面借助Mn 元素在析出相附近的富集作用实现Mn元素的局部偏聚。在本发明中，NiAl相和富Cu相的协同析出在提高强度的同时不降低韧性，同时，由于Mn元素与Cu、Ni元素较高的结合焓，因此可实现Mn元素的局部偏聚。除此之外，Mn元素替代部分Ni元素能够显著提高钢的强塑性，并降低成本，提高经济效益。基于第一步引入的Mn元素局部偏聚，第二步第一次两相区等温处理得到的部分残余奥氏体在随后的淬火过程中由于奥氏体稳定元素的不足进一步生成新鲜马氏体，这些新鲜马氏体优化了第三步第二次两相区等温过程中的逆变奥氏体与铁素体基体的界面共格性，从而提高了残余奥氏体的机械稳定性。Among them, the first step of pre-precipitation plays a role of precipitation strengthening by introducing nano-precipitation phase on the one hand, and local segregation of Mn element is realized by the enrichment of Mn element near the precipitation phase on the other hand. In the present invention, the synergistic precipitation of the NiAl phase and the Cu-rich phase increases the strength without reducing the toughness, and at the same time, due to the higher binding enthalpy of Mn element, Cu and Ni elements, local segregation of Mn element can be achieved. In addition, the replacement of some Ni elements by Mn elements can significantly improve the strength and plasticity of steel, reduce costs, and improve economic benefits. Based on the local segregation of Mn elements introduced in the first step, part of the retained austenite obtained by the isothermal treatment of the first two-phase region in the second step will further generate fresh martensite due to the lack of austenite stabilizing elements in the subsequent quenching process. , these fresh martensites optimize the interfacial coherence between the reversed austenite and the ferrite matrix during the isothermal process of the second two-phase region in the third step, thereby improving the mechanical stability of the retained austenite.
本发明提供的低温用钢及其热处理工艺，采用预析出-双配分工艺，在拉伸过程中利用残余奥氏体的TRIP效应和纳米析出相的析出强化，能够制备-196℃温度下屈服强度940-980MPa、抗拉强度1300-1400MPa、延伸率30-40％以及强塑积达到45000-48000MPa％的高强塑性节镍型纳米析出强化低温钢，无需冷变形处理，能够适应大规模生产。The low-temperature steel and the heat treatment process thereof provided by the invention adopt the pre-precipitation-double-partition process, utilize the TRIP effect of the retained austenite and the precipitation strengthening of the nano-precipitate phase in the stretching process, and can prepare the yield strength at a temperature of -196° C. 940-980MPa, 1300-1400MPa tensile strength, 30-40% elongation and 45,000-48,000MPa% high-strength plastic nickel-section nano-precipitation-strengthened low-temperature steel, without cold deformation treatment, can adapt to mass production.
本发明提供的低温用钢及其热处理工艺，采用析出诱导逆相变优化残余奥氏体和铁素体基体的界面共格性，利用残余奥氏体的TRIP效应和NiAl、富铜相等纳米析出颗粒的强化效应，制备获得强塑性和低温韧性兼具的节镍型低温钢，应用成本低，热处理工艺简单，经济适用性强。In the low-temperature steel and its heat treatment process provided by the invention, the precipitation-induced reverse phase transformation is used to optimize the interface coherence between the retained austenite and the ferrite matrix, and the TRIP effect of the retained austenite and the nanometer precipitation of NiAl and copper-rich are utilized. The strengthening effect of particles can prepare nickel-saving low-temperature steel with both strong plasticity and low-temperature toughness, with low application cost, simple heat treatment process and strong economical applicability.
附图说明Description of drawings
图1显示为本发明中经过预析出和未经预析出的双配分热处理后得到的低温钢扫描显微组织对比图1a、1b，其中，图1a为实施例1中预析出-双配分的低温钢扫描显微组织图；图1b为对比例1中未经预析出的双配分的低温钢扫描显微组织图。Fig. 1 shows the scanning microstructure comparison of low-temperature steel obtained after pre-precipitation and double-partition heat treatment without pre-precipitation in the present invention. Scanning microstructure of steel; Figure 1b is a scanning microstructure of low-temperature steel without pre-precipitation in Comparative Example 1.
图2显示为本发明中经过预析出和未经预析出的双配分热处理后得到的低温钢双相界面共格关***计图2a、2b，其中，图2a为实施例1中预析出-双配分的低温钢双相界面共格关***计图；图2b为对比例1中未经预析出的双配分的低温钢双相界面共格关***计图。Fig. 2 shows the coherence relationship statistics of the dual-phase interface of low-temperature steel obtained after pre-precipitation and double-partition heat treatment without pre-precipitation in the present invention, wherein Fig. 2a shows the pre-precipitation-double-partition in Example 1 Figure 2b is a coherent relationship statistical diagram of the low-temperature steel dual-phase interface without pre-precipitation in Comparative Example 1.
具体实施方式Detailed ways
以下由特定的具体实施例说明本发明的实施方式，熟悉此技术的人士可由本说明书所揭露的内容轻易地了解本发明的其他优点及功效。The embodiments of the present invention are described below by specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.
请参阅图1至图2。须知，本说明书所附图式所绘示的结构、比例、大小等，均仅用以配合说明书所揭示的内容，以供熟悉此技术的人士了解与阅读，并非用以限定本发明可实施的限定条件，故不具技术上的实质意义，任何结构的修饰、比例关系的改变或大小的调整，在不影响本发明所能产生的功效及所能达成的目的下，均应仍落在本发明所揭示的技术内容 得能涵盖的范围内。同时，本说明书中所引用的如“上”、“下”、“左”、“右”、“中间”及“一”等的用语，亦仅为便于叙述的明了，而非用以限定本发明可实施的范围，其相对关系的改变或调整，在无实质变更技术内容下，当亦视为本发明可实施的范畴。See Figures 1 to 2. It should be noted that the structures, proportions, sizes, etc. shown in the drawings in this specification are only used to cooperate with the contents disclosed in the specification, so as to be understood and read by those who are familiar with the technology, and are not used to limit the implementation of the present invention. Restricted conditions, it does not have technical substantive significance, any structural modification, proportional relationship change or size adjustment, without affecting the effect that the present invention can produce and the purpose that can be achieved, should still fall within the present invention. The disclosed technical content must be within the scope of coverage. At the same time, the terms such as "up", "down", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and clarity, and are not used to limit this specification. The implementable scope of the invention, and the change or adjustment of the relative relationship thereof, shall also be regarded as the implementable scope of the present invention without substantially changing the technical content.
须知，下列实施例中未具体注明的工艺设备或装置均采用本领域内的常规设备或装置；所有压力值和范围都是指相对压力。It should be noted that the process equipment or devices that are not specifically noted in the following examples are conventional devices or devices in the art; all pressure values and ranges refer to relative pressures.
此外应理解，本发明中提到的一个或多个方法步骤并不排斥在所述组合步骤前后还可以存在其他方法步骤或在这些明确提到的步骤之间还可以***其他方法步骤，除非另有说明；还应理解，本发明中提到的一个或多个设备/装置之间的组合连接关系并不排斥在所述组合设备/装置前后还可以存在其他设备/装置或在这些明确提到的两个设备/装置之间还可以***其他设备/装置，除非另有说明。而且，除非另有说明，各方法步骤的编号仅为鉴别各方法步骤的便利工具，而非为限制各方法步骤的排列次序或限定本发明可实施的范围，其相对关系的改变或调整，在无实质变更技术内容的情况下，当亦视为本发明可实施的范畴。Furthermore, it should be understood that the mention of one or more method steps in the present invention does not exclude that other method steps may also be present before and after said combined step or that other method steps may be inserted between these expressly mentioned steps, unless otherwise There are descriptions; it should also be understood that the combined connection relationship between one or more devices/devices mentioned in the present invention does not exclude that there may be other devices/devices before and after the combined device/device or explicitly mentioned in these Other devices/devices can be inserted between the two devices/devices unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, rather than limiting the arrangement order of each method step or limiting the scope of the present invention. In the case where the technical content is not substantially changed, it should also be regarded as the scope in which the present invention can be implemented.
以下实施例使用的含碳、镍、锰、铝、铜、硫、磷、氮、氧、钙、铁等元素的原料均可从市场上购买，实现冶炼、板坯连铸、热轧处理、回火、等温处理、水淬等工艺的设备也可从市场上购买获得。The raw materials containing carbon, nickel, manganese, aluminum, copper, sulfur, phosphorus, nitrogen, oxygen, calcium, iron and other elements used in the following examples can be purchased from the market to achieve smelting, continuous slab casting, hot rolling, Equipment for tempering, isothermal treatment, water quenching and other processes can also be purchased from the market.
实施例1Example 1
按配比取含各元素组分混合后冶炼，再板坯连铸成铸锭，各组分由以下质量百分比的元素组成：C：0.008-0.012％；Ni：2.0-3.0％；Mn：6.0-8.0％；Al：1.5-2.0％；Cu：2.5-3.0％；S：≤0.004％；P：≤0.003％；N：0.003-0.005％；O：0.0005-0.001％；Ca：0.0005-0.005％；余量为Fe。将铸锭除锈去油、清洗干净，避免热轧处理过程中的受力不均现象。According to the proportions, the components containing each element are mixed and then smelted, and then slab is continuously cast into an ingot. Each component is composed of the following elements by mass percentage: C: 0.008-0.012%; Ni: 2.0-3.0%; 8.0%; Al: 1.5-2.0%; Cu: 2.5-3.0%; S: ≤0.004%; P: ≤0.003%; N: 0.003-0.005%; O: 0.0005-0.001%; Ca: 0.0005-0.005%; The balance is Fe. Remove rust and oil from the ingot, and clean it to avoid uneven stress during the hot rolling process.
将铸锭进行热轧处理，由初轧温度1200℃至终轧温度750℃进行多步热轧后空冷。多步热轧的步骤为：分别连续在1200、900、750℃温度下，下压率分别为25％、25％、25％，保温时间分别为120、70、30分钟。The ingot is subjected to hot rolling treatment, and is subjected to multi-step hot rolling from a preliminary rolling temperature of 1200 °C to a final rolling temperature of 750 °C, followed by air cooling. The steps of the multi-step hot rolling are as follows: successively at temperatures of 1200, 900 and 750° C., the reduction rates are respectively 25%, 25% and 25%, and the holding times are respectively 120, 70 and 30 minutes.
将热轧处理后的钢锭，在A 1温度以下50-100℃保温0.5-1.0h进行回火预析出，然后水冷至室温进行水淬。再在A 1温度以上50-80℃进行第一次两相区等温保温0.5-1.0h，然后水冷至室温进行水淬。最后进行第二次两相区等温保温0.5-1.5h，第二次两相区等温的等温温度低于第一次两相区等温的等温温度30-40℃，然后水冷至室温进行水淬，获得低温用钢样品1#。上述A 1温度为620-670℃。室温为20-25℃。 The hot-rolled steel ingot is kept at 50-100° C. below the A1 temperature for 0.5-1.0 h for tempering and pre - precipitation, and then water-cooled to room temperature for water quenching. Then, at 50-80°C above the A1 temperature, the first two-phase zone is isothermally held for 0.5-1.0h, and then water-cooled to room temperature for water quenching. Finally, carry out the second two-phase zone isothermal heat preservation for 0.5-1.5h, the isothermal temperature of the second two-phase zone isothermal temperature is lower than that of the first two-phase zone isothermal temperature by 30-40°C, and then water-cooled to room temperature for water quenching, Obtain low temperature steel sample 1#. The above A1 temperature is 620-670 °C. Room temperature is 20-25°C.
实施例2Example 2
按配比取含各元素组分混合后冶炼，再板坯连铸成铸锭，各组分由以下质量百分比的元素组成：C：0.008％；Ni：2.0％；Mn：7.0％；Al：1.5％；Cu：2.0％；S：0.004％；P：0.003％；N：0.003％；O：0.0005％；Ca：0.0005％；余量为Fe。将铸锭除锈去油、清洗干净，避免热轧处理过程中的受力不均现象。According to the proportions, the components containing each element are mixed and then smelted, and then slab is continuously cast into ingots. Each component is composed of the following elements by mass percentage: C: 0.008%; Ni: 2.0%; Mn: 7.0%; Al: 1.5 %; Cu: 2.0%; S: 0.004%; P: 0.003%; N: 0.003%; O: 0.0005%; Ca: 0.0005%; Remove rust and oil from the ingot, and clean it to avoid uneven stress during the hot rolling process.
将铸锭进行热轧处理，由初轧温度1200℃至终轧温度750℃进行多步热轧后空冷。多步热轧的步骤为：分别连续在1150、850、770℃温度下，下压率分别为30％、25％、25％，保温时间分别为115、65、25分钟。The ingot is subjected to hot rolling treatment, and is subjected to multi-step hot rolling from a preliminary rolling temperature of 1200 °C to a final rolling temperature of 750 °C, followed by air cooling. The steps of the multi-step hot rolling are as follows: continuously at temperatures of 1150, 850, and 770° C., the reduction rates are 30%, 25%, and 25%, respectively, and the holding time is 115, 65, and 25 minutes, respectively.
将热轧处理后的钢锭，在A 1温度以下50℃保温1.0h进行回火预析出，然后水冷至室温进行水淬。再在A 1温度以上80℃进行第一次两相区等温保温0.5h，然后水冷至室温进行水淬。最后进行第二次两相区等温保温1.0h，第二次两相区等温的等温温度低于第一次两相区等温的等温温度40℃，然后水冷至室温进行水淬，获得低温用钢样品2#。上述A 1温度为630℃。室温为20-25℃。 The hot-rolled ingot is kept at 50°C below the A1 temperature for 1.0 h for tempering and pre-precipitation, and then water-cooled to room temperature for water quenching. Then, the first two-phase zone isothermal heat preservation was carried out at 80 °C above the A1 temperature for 0.5 h, and then water-cooled to room temperature for water quenching. Finally, the second isothermal temperature in the two-phase zone is carried out for 1.0 h. The isothermal temperature of the second two-phase zone is lower than the isothermal temperature of the first two-phase zone by 40°C, and then water-cooled to room temperature for water quenching to obtain low-temperature steel. Sample 2#. The above - mentioned A1 temperature is 630°C. Room temperature is 20-25°C.
实施例3Example 3
按配比取含各元素组分混合后冶炼，再板坯连铸成铸锭，各组分由以下质量百分比的元素组成：C：0.01％；Ni：2.5％；Mn：7.0％；Al：2.0％；Cu：2.5％；S：0.004％；P：0.003％；N：0.003％；O：0.0005％；Ca：0.0005％；余量为Fe。将铸锭除锈去油、清洗干净，避免热轧处理过程中的受力不均现象。According to the proportion, the components containing each element are mixed and then smelted, and then slab is continuously cast into ingots. Each component is composed of the following elements by mass percentage: C: 0.01%; Ni: 2.5%; Mn: 7.0%; Al: 2.0 %; Cu: 2.5%; S: 0.004%; P: 0.003%; N: 0.003%; O: 0.0005%; Ca: 0.0005%; Remove rust and oil from the ingot, and clean it to avoid uneven stress during the hot rolling process.
将铸锭进行热轧处理，由初轧温度1200℃至终轧温度750℃进行多步热轧后空冷。多步热轧的步骤为：分别连续在1180、880、760℃温度下，下压率分别为25％、25％、30％，保温时间分别为125、65、30分钟。The ingot is subjected to hot rolling treatment, and is subjected to multi-step hot rolling from a preliminary rolling temperature of 1200 °C to a final rolling temperature of 750 °C, followed by air cooling. The steps of the multi-step hot rolling are as follows: continuously at temperatures of 1180, 880 and 760° C., the reduction rates are respectively 25%, 25% and 30%, and the holding times are respectively 125, 65 and 30 minutes.
将热轧处理后的钢锭，在A 1温度以下80℃保温1.0h进行回火预析出，然后水冷至室温进行水淬。再在A 1温度以上80℃进行第一次两相区等温保温0.5h，然后水冷至室温进行水淬。最后进行第二次两相区等温保温1.0h，第二次两相区等温的等温温度低于第一次两相区等温的等温温度40℃，然后水冷至室温进行水淬，获得低温用钢样品3#。上述A 1温度为620℃。室温为20-25℃。 The hot-rolled steel ingot is kept at 80°C below the A1 temperature for 1.0 h for tempering and pre-precipitation, and then water-cooled to room temperature for water quenching. Then, the first two-phase zone isothermal heat preservation was carried out at 80 °C above the A1 temperature for 0.5 h, and then water-cooled to room temperature for water quenching. Finally, the second isothermal temperature in the two-phase zone is carried out for 1.0 h. The isothermal temperature of the second two-phase zone is lower than the isothermal temperature of the first two-phase zone by 40°C, and then water-cooled to room temperature for water quenching to obtain low-temperature steel. Sample 3#. The above - mentioned A1 temperature is 620°C. Room temperature is 20-25°C.
对比例1Comparative Example 1
按配比取含各元素组分混合后冶炼，再板坯连铸成铸锭，各组分由以下质量百分比的元素组成：C：0.008-0.012％；Ni：2.0-3.0％；Mn：6.0-8.0％；Al：1.5-2.0％；Cu：2.5-3.0％；S：≤0.004％；P：≤0.003％；N：0.003-0.005％；O：0.0005-0.001％；Ca：0.0005-0.005％；余量为 Fe。将铸锭除锈去油、清洗干净，避免热轧处理过程中的受力不均现象。According to the proportions, the components containing each element are mixed and then smelted, and then slab is continuously cast into an ingot. Each component is composed of the following elements by mass percentage: C: 0.008-0.012%; Ni: 2.0-3.0%; 8.0%; Al: 1.5-2.0%; Cu: 2.5-3.0%; S: ≤0.004%; P: ≤0.003%; N: 0.003-0.005%; O: 0.0005-0.001%; Ca: 0.0005-0.005%; The balance is Fe. Remove rust and oil from the ingot, and clean it to avoid uneven stress during the hot rolling process.
将铸锭进行热轧处理，由初轧温度1200℃至终轧温度750℃进行多步热轧后空冷。多步热轧的步骤为：分别连续在1200、900、750℃温度下，下压率分别为25％、25％、25％，保温时间分别为120、60、30分钟。The ingot is subjected to hot rolling treatment, and is subjected to multi-step hot rolling from a preliminary rolling temperature of 1200 °C to a final rolling temperature of 750 °C, followed by air cooling. The steps of the multi-step hot rolling are as follows: continuously at temperatures of 1200, 900 and 750° C., the reduction rates are respectively 25%, 25% and 25%, and the holding times are respectively 120, 60 and 30 minutes.
将热轧处理后的钢锭，在A 1温度以下50-80℃保温0.5-1.0h进行回火预析出，然后水冷至室温进行水淬。再在A 1温度以上50-70℃进行两相区等温保温0.5-1.5h，然后水冷至室温进行水淬，获得低温用钢对比样品1*。上述A 1温度为620-670℃。室温为20-25℃。 The hot-rolled steel ingot is kept at 50-80° C. below the A1 temperature for 0.5-1.0 h for tempering and pre - precipitation, and then water-cooled to room temperature for water quenching. Then, the two-phase zone is isothermally held at 50-70°C above the A1 temperature for 0.5-1.5h , and then water-cooled to room temperature for water quenching to obtain a low-temperature steel comparative sample 1*. The above - mentioned A1 temperature is 620-670°C. Room temperature is 20-25°C.
测试例1Test Example 1
将实施例1中获得的低温用钢样品1#，与对比例1中获得的低温用钢对比样品1*，分别进行常温和低温拉伸实验，具体结果见表1。由表1可知，相较于未进行预析出的低温钢，主要得益于残余奥氏体诱导的TRIP效应以及纳米析出相的协同强化作用，经过预析出-双配分工艺处理后，低温钢的超低温强塑性得到大大提升，能够制备-196℃温度下屈服强度940-980MPa、抗拉强度1300-1400MPa、延伸率30-40％以及强塑积达到49000-63000MPa％的高强塑积节镍型纳米析出强化低温钢。The low-temperature steel sample 1# obtained in Example 1 and the low-temperature steel comparative sample 1* obtained in Comparative Example 1 were subjected to tensile experiments at room temperature and low temperature, respectively. The specific results are shown in Table 1. It can be seen from Table 1 that compared with the low-temperature steel without pre-precipitation, it is mainly due to the TRIP effect induced by retained austenite and the synergistic strengthening effect of the nano-precipitation phase. The ultra-low temperature strength and plasticity have been greatly improved, and it can prepare high-strength-plastic product nickel-type nanometers with a yield strength of 940-980MPa, a tensile strength of 1300-1400MPa, an elongation of 30-40%, and a strong-plastic product of 49000-63000MPa% at -196℃. Precipitation strengthened low temperature steel.
表1低温钢预析出-双配分前后力学性能对比表Table 1 Comparison of mechanical properties of low temperature steel before and after pre-precipitation-double partitioning
Figure PCTCN2021078443-appb-000001
Figure PCTCN2021078443-appb-000001
注：其中√代表已处理，/代表未处理Note: √ means processed, / means not processed
测试例2 Test case 2
将实施例1中获得的低温用钢样品1#，与对比例1中获得的低温用钢对比样品1*，分别进行X射线衍射实验对残余奥氏体含量进行测量，具体结果见表2。并对两种样品采用扫描电镜进行组织表征，具体结果见图1a、1b。The content of retained austenite was measured by X-ray diffraction experiments on the low-temperature steel sample 1# obtained in Example 1 and the low-temperature steel comparative sample 1* obtained in Comparative Example 1. The specific results are shown in Table 2. The two samples were characterized by scanning electron microscopy, and the specific results are shown in Figures 1a and 1b.
由表2可知，经过预析出-双配分工艺处理之后，低温钢的残余奥氏体含量维持在43.3-45.6％，未经过预析出工艺处理的低温钢中残余奥氏体含量为42.7-44.9％，两者残余奥氏体含量几乎相同。两种工艺下相同奥氏体含量所带来的不同力学性能主要取决于双相界面共格关系的调控，从而影响了奥氏体在相变过程中所诱导的TRIP效应，经过预析出-双配分工艺处理的低温钢中的奥氏体具有更高机械稳定性，因此低温下强塑性更好。It can be seen from Table 2 that after the pre-precipitation-double partition process, the residual austenite content of the low-temperature steel is maintained at 43.3-45.6%, and the residual austenite content of the low-temperature steel without the pre-precipitation process is 42.7-44.9% , the retained austenite content of the two is almost the same. The different mechanical properties brought by the same austenite content under the two processes mainly depend on the regulation of the coherent relationship of the dual-phase interface, which affects the TRIP effect induced by the austenite during the phase transformation. The austenite in the low temperature steel treated by the partition process has higher mechanical stability, so the strong plasticity at low temperature is better.
表2 低温钢预析出-双配分前后残余奥氏体含量对比表Table 2 Comparison of retained austenite content before and after pre-precipitation-double partitioning of low temperature steel
样品sample 回火tempered 配分allotment 再配分redistribution 奥氏体含量(％)Austenite content (%)
1#1# √√ √√ √√ 43.3-45.643.3-45.6
1*1* // √√ √√ 42.7-44.942.7-44.9
注：其中√代表已处理，/代表未处理Note: √ means processed, / means not processed
由图1a、1b可知，经过预析出-双配分工艺处理后的组织兼具残余奥氏体、铁素体(回火马氏体)和纳米析出相，且晶粒尺寸得到了有效细化，经过多步热处理之后，纳米析出相弥散分布于基体中，起到了有效的强化作用。未经预析出工艺处理的低温钢组织与前者类似，基体组织均为回火马氏体和纳米析出相的复相组织。It can be seen from Figures 1a and 1b that the structure treated by the pre-precipitation-double partition process has both retained austenite, ferrite (tempered martensite) and nano-precipitated phases, and the grain size is effectively refined, After multi-step heat treatment, the nano-precipitate phase is dispersed in the matrix, which plays an effective strengthening role. The microstructure of the low-temperature steel without pre-precipitation process is similar to the former, and the matrix structure is a complex structure of tempered martensite and nano-precipitated phase.
测试例3Test case 3
将实施例1中获得的低温用钢样品1#，与对比例1中获得的低温用钢对比样品1*，分别进行电子背散射衍射(EBSD)界面取向关***计分析，具体结果见图2a、2b。由图2a、2b可知，在经过预析出-双配分工艺后，奥氏体/铁素体双相界面关系得到了优化，大多呈共格关系，而未经过预析出工艺处理的低温钢存在大量奥氏体与基体呈半共格甚至非共格关系。The low-temperature steel sample 1# obtained in Example 1 and the low-temperature steel comparative sample 1* obtained in Comparative Example 1 were subjected to a statistical analysis of the interface orientation relationship by electron backscatter diffraction (EBSD). The specific results are shown in Figure 2a, 2b. It can be seen from Figures 2a and 2b that after the pre-precipitation-double partition process, the austenite/ferrite dual-phase interface relationship is optimized, and most of them are in a coherent relationship, while there are a lot of low-temperature steels without pre-precipitation process. Austenite and matrix are semi-coherent or even incoherent.
综上所述，本发明提供的一种析出强化的低温用钢及其热处理工艺，能够得到一种低温强塑性和韧性兼具的节镍型纳米析出强化低温钢，应用成本低，无需冷变形处理，热处理工艺简单，经济适用性强。所以，本发明有效克服了现有技术中的种种缺点而具高度产业利用价值。To sum up, the precipitation-strengthened low-temperature steel and its heat treatment process provided by the present invention can obtain a nickel-saving nano-precipitation-strengthened low-temperature steel with both low-temperature strong plasticity and toughness, with low application cost and no need for cold deformation Treatment, the heat treatment process is simple, and the economical applicability is strong. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.
上述实施例仅例示性说明本发明的原理及其功效，而非用于限制本发明。任何熟悉此技术的人士皆可在不违背本发明的精神及范畴下，对上述实施例进行修饰或改变。因此，举凡所属技术领域中具有通常知识者在未脱离本发明所揭示的精神与技术思想下所完成的一切等效修饰或改变，仍应由本发明的权利要求所涵盖。The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

  1. 一种低温用钢，由以下质量百分比的元素组成：A low temperature steel, consisting of the following elements by mass percentage:
    C：0.005-0.015％；Ni：1.5-4.5％；Mn：5.0-10.0％；Al：1.0-3.0％；Cu：1.5-3.0％；S：≤0.004％；P：≤0.003％；N：0.003-0.005％；O：0.0005-0.001％；Ca：0.0005-0.005％；余量为Fe。C: 0.005-0.015%; Ni: 1.5-4.5%; Mn: 5.0-10.0%; Al: 1.0-3.0%; Cu: 1.5-3.0%; S:≤0.004%; P:≤0.003%; N: 0.003 -0.005%; O: 0.0005-0.001%; Ca: 0.0005-0.005%; the balance is Fe.
  2. 根据权利要求1所述的一种低温用钢，其特征在于，所述低温用钢，由以下质量百分比的元素组成：A kind of low temperature steel according to claim 1, is characterized in that, described low temperature steel is made up of the following elements by mass percentage:
    C：0.008-0.012％；Ni：1.5-3.0％；Mn：7.0-10.0％；Al：1.0-2.0％；Cu：2.0-3.0％；S：≤0.004％；P：≤0.003％；N：0.003-0.005％；O：0.0005-0.001％；Ca：0.0005-0.005％；余量为Fe。C: 0.008-0.012%; Ni: 1.5-3.0%; Mn: 7.0-10.0%; Al: 1.0-2.0%; Cu: 2.0-3.0%; S:≤0.004%; P:≤0.003%; N: 0.003 -0.005%; O: 0.0005-0.001%; Ca: 0.0005-0.005%; the balance is Fe.
  3. 根据权利要求1-2任一所述的一种低温用钢的热处理工艺，按配比取各元素组分混合后冶炼，再板坯连铸成铸锭，进行热轧处理，获得的钢锭进行回火预析出后水淬，再依次进行第一次两相区等温后水淬、第二次两相区等温后水淬，以提供所述低温用钢。According to the heat treatment process of a kind of low-temperature steel according to any one of claims 1-2, each element component is mixed and smelted according to the proportion, and then the slab is continuously cast into an ingot, which is subjected to hot rolling treatment, and the obtained ingot is recycled. Water quenching after fire pre-precipitation, followed by the first two-phase zone isothermal water quenching and the second two-phase zone isothermal post-water quenching in order to provide the low-temperature steel.
  4. 根据权利要求3所述的一种低温用钢的热处理工艺，其特征在于，所述热轧处理是将铸锭由初轧温度至终轧温度进行多步热轧后空冷；所述初轧温度为1150-1250℃；所述终轧温度为700-800℃。The heat treatment process for low-temperature steel according to claim 3, wherein the hot rolling treatment is to perform multi-step hot rolling on the ingot from the preliminary rolling temperature to the final rolling temperature and then air-cool; the preliminary rolling temperature is 1150-1250°C; the finishing rolling temperature is 700-800°C.
  5. 根据权利要求4所述的一种低温用钢的热处理工艺，其特征在于，所述多步热轧包括以下步骤：A kind of heat treatment process of low temperature steel according to claim 4, is characterized in that, described multi-step hot rolling comprises the following steps:
    第一步：热轧温度：1150-1250℃，保温时间：115-125分钟；The first step: hot rolling temperature: 1150-1250 ℃, holding time: 115-125 minutes;
    第二步：热轧温度：880-970℃，保温时间：65-75分钟；The second step: hot rolling temperature: 880-970 ℃, holding time: 65-75 minutes;
    第三步：热轧温度：700-800℃，保温时间：20-30分钟3002The third step: hot rolling temperature: 700-800 ℃, holding time: 20-30 minutes 3002
  6. 根据权利要求3所述的一种低温用钢的热处理工艺，其特征在于，所述回火的温度为A 1温度至A 1温度以下50-120℃区间。 The heat treatment process for low-temperature steel according to claim 3 , wherein the tempering temperature is in the range of 50-120°C below the A1 temperature to the A1 temperature.
  7. 根据权利要求3所述的一种低温用钢的热处理工艺，其特征在于，所述回火的时间为0.5-1.5h。The heat treatment process for low temperature steel according to claim 3, wherein the tempering time is 0.5-1.5h.
  8. 根据权利要求3所述的一种低温用钢的热处理工艺，其特征在于，所述第一次两相区等温的等温温度为A 1温度至A 1温度以上20-100℃区间。 The heat treatment process for low-temperature steel according to claim 3, wherein the isothermal temperature of the first two - phase zone isothermal temperature ranges from the A1 temperature to 20-100°C above the A1 temperature.
  9. 根据权利要求3所述的一种低温用钢的热处理工艺，其特征在于，所述第一次两相区等温的等温温度高于所述第二次两相区等温的等温温度30-40℃。The heat treatment process for low-temperature steel according to claim 3, wherein the isothermal temperature in the first two-phase zone is higher than the isothermal temperature in the second two-phase zone by 30-40°C .
  10. 根据权利要求3所述的一种低温用钢的热处理工艺，其特征在于，所述第一次两相区等温和第二次两相区等温的等温时间均为0.5-1.5h。The heat treatment process for low-temperature steel according to claim 3, wherein the isothermal time of the first two-phase zone isothermal temperature and the second two-phase zone isothermal temperature are both 0.5-1.5 h.
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