CN112680652A - Cr-Mo low-alloy steel plate for pressure vessel and preparation method thereof - Google Patents
Cr-Mo low-alloy steel plate for pressure vessel and preparation method thereof Download PDFInfo
- Publication number
- CN112680652A CN112680652A CN202011146929.7A CN202011146929A CN112680652A CN 112680652 A CN112680652 A CN 112680652A CN 202011146929 A CN202011146929 A CN 202011146929A CN 112680652 A CN112680652 A CN 112680652A
- Authority
- CN
- China
- Prior art keywords
- steel
- rolling
- steel plate
- less
- casting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
The invention discloses a Cr-Mo low-alloy steel plate for a pressure vessel and a preparation method thereof. The steel plate comprises the following components in percentage by mass: c: 0.14 to 0.19%, Si: 0.17-0.35%, Mn: 0.70-0.90%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, Cr: 0.10% -0.25%, Mo: 0.25% -0.35%, Nb: 0.015-0.030%, and the balance of Fe and inevitable impurities. The preparation method of the steel plate is characterized by comprising the following steps: smelting and casting: carrying out primary smelting on molten iron and scrap steel to obtain primary molten steel, and then refining and casting the primary molten steel to obtain a casting blank; rolling and water cooling: heating the casting blank to obtain a hot casting blank, and rolling and cooling the hot casting blank to obtain a steel plate; normalizing heat treatment: and carrying out normalizing heat treatment on the steel plate to obtain the steel plate. The steel grade has the advantages of low added alloy types and content, simple process, easy operation, good strong plasticity, impact toughness, uniformity of performance in the thickness direction and high-temperature mechanical property.
Description
Technical Field
The invention belongs to the technical field of steel plate production, and particularly relates to a Cr-Mo low-alloy high-performance steel plate for a pressure vessel.
Background
The steel for the high-temperature pressure container is an important material applied to high-temperature conditions in industries such as metallurgy, petroleum, chemical engineering and the like, and has good high-temperature strength, creep resistance, corrosion resistance and the like. With the development of national economy of China, the requirements on the working parameters of boilers and pressure vessels are required to be gradually improved based on the consideration of environmental protection and improvement of energy utilization rate, and the performance requirements on the materials are also more strict.
According to incomplete statistics, the country has 1000-4000m3100 seats of a large-scale blast furnace, small blast furnaces with high energy consumption and heavy pollution are gradually eliminated, and the current national standard 'blast furnace ironmaking process design specification' proposesThe working life of the first-generation furnace of the blast furnace can reach more than 15 years. The longevity of the blast furnace and the corollary equipment thereof can save overhaul cost, improve the operation rate and the utility index of the equipment, increase the pig iron yield, reduce the consumption of manpower and material resources and reduce the cost of iron per ton.
The blast furnace and the hot blast stove have complex and harsh use conditions, and mainly show that after cooling equipment and a refractory lining material in the blast furnace and the hot blast stove are damaged in the later period of the furnace service, a furnace shell bears thermal shock load to generate fatigue cracking. If the furnace shell steel is selected randomly, the service life of the blast furnace is short, and after the blast furnace is generally produced and used for several years, intermediate repair and overhaul are required, so that huge economic loss is caused. The blast furnace and the furnace shell steel thereof are in a state without clear specification and feasibility, and the steel types which can be selected by a design institute are very limited according to the actual experience and research results of certain large-scale steel enterprises.
At present, many patents are related to high-performance pressure vessel steel, but the defects of high alloy content, complex process flow, insufficient high-temperature resistance and the like generally exist, and the following patents are briefly introduced:
chinese patent application CN 108425002 discloses a preparation method of a 12Cr2Mo1 hot-rolled container steel plate, the steel plate related to the patent is produced by adopting the processes of controlled rolling, normalizing and tempering, the production flow is more complex than the application, and the heat treatment cost is higher. And the steel plate has insufficient high-temperature performance and cannot meet the service requirement in a high-temperature environment.
Chinese patent publication No. CN 103695782 discloses "steel for a mobile pressure vessel with a tensile strength of 630MPa and a production method thereof", which is added with a plurality of alloying elements such as Ni, V, Ti, Cu, Cr, etc., and has a high production cost, and does not mention high-temperature mechanical properties, and cannot meet the service requirements in a high-temperature environment.
Chinese patent application CN 108149134A discloses a 12Cr2Mo1VR steel plate for a high-temperature pressure container and a production method thereof, the steel plate related to the patent has the advantages that the Cr content is higher than 2.4-2.5%, the Mo content is higher than 0.95-1.05%, V, Ni alloy elements are additionally added, the alloy cost is higher, the production is carried out by adopting a method of twice quenching and once tempering in the production process, the process flow is complex, and the heat treatment cost is higher.
Chinese patent application CN 109112400 discloses a heat-resistant 12Cr1MoVR steel plate for a container and a production method thereof, the steel plate related to the patent has the high Cr content of 0.95-1.10%, V0.15-0.25% with high cost is added, the steel plate related to the patent is produced by adopting a normalizing and tempering heat treatment process, the heat treatment cost is high, and in addition, the high-temperature mechanical property is not mentioned.
Chinese patent application CN 109112421 discloses 'steel 07Cr2AlMoR for pressure vessel and production method thereof', the steel plate related to the patent has a high Cr content of 2.10-2.30%, and the steel plate related to the patent is produced by adopting a normalizing and tempering heat treatment process, the heat treatment process is complex, the cost is high, in addition, the impact power at room temperature is far lower than that of the application, and the high-temperature mechanical property is not mentioned.
Disclosure of Invention
Aiming at the defects and shortcomings of the prior art, the invention aims to provide a Cr-Mo low-alloy steel plate for containers and a preparation method thereof. The steel grade has the advantages of low added alloy types and content, simple process, easy operation, good strong plasticity, impact toughness, uniformity of performance in the thickness direction, high-temperature mechanical property, high flaw detection quality grade and good surface quality.
The technical scheme adopted by the invention for solving the technical problem is as follows:
the steel plate for the low-alloy pressure container comprises the following components in percentage by mass: c: 0.14 to 0.19%, Si: 0.17-0.35%, Mn: 0.70-0.90%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, Cr: 0.10% -0.25%, Mo: 0.25% -0.35%, Nb: 0.015-0.030%, and the balance of Fe and inevitable impurities.
In the above Cr — Mo low alloy steel sheet for pressure vessels, as a preferred embodiment, the steel sheet has the following composition in mass percent: c: 0.14 to 0.17%, Si: 0.20 to 0.35%, Mn: 0.70-0.90%, P: less than or equal to 0.018%, S: less than or equal to 0.005 percent, Cr: 0.10% -0.25%, Mo: 0.25% -0.35%, Nb: 0.015-0.030%, and the balance of Fe and inevitable impurities; wherein, considering the contribution of the second phase precipitation strengthening of the alloy elements to the high-temperature mechanical property, the content of Cr + Mo satisfies: 0.863C +0.267Mn +2.837Nb is less than or equal to Cr + Mo is less than or equal to 0.975C +0.369Mn +3.405 Nb;
preferably, Cr: 0.15-0.22%, Mo: 0.28-0.3%, Nb: 0.015-0.025%.
Cr: chromium is an element for reducing an austenite region, and carbide can be formed in steel, so that the decomposition of alloy carbide, the diffusion of carbon and the segregation of cementite at a grain boundary can be effectively prevented or slowed down in a high-temperature service environment, but the cold crack sensitivity of steel welding can be improved by adding excessive Cr.
Mo: molybdenum is higher than Mn and Cr in the ability of improving the strength, especially the high-temperature strength, of the steel, and is one of the main elements for enhancing the hydrogen corrosion resistance of the steel. The high-temperature creep strength of the steel can be greatly improved by adding Mo, the toughness of weld metal can be improved by a small amount of Mo, but the hardenability of the steel can be improved by adding excessive Mo, so that the welding cold crack sensitivity of steel is improved; on the other hand, the mechanical property stability of the steel plate after the heat treatment process can be ensured by adding Mo.
Nb: the element niobium is added to promote the grain refinement of the rolled microstructure of the steel plate, the strength and the toughness can be improved simultaneously, the niobium can effectively refine the microstructure by inhibiting austenite recrystallization in the controlled rolling process, and the Nb-containing steel can be rolled at higher temperature to obtain a fine grain structure by separating out a strengthening matrix. However, if the Nb content is too high, a ferrite delta phase or other brittle phases are formed, and the toughness is lowered, resulting in deterioration of hot workability. In the welding process, the segregation and precipitation of niobium atoms can prevent austenite grains from coarsening during heating, ensure that a finer heat-affected zone structure is obtained after welding, and improve the performance of a welding heat-affected zone.
Cr and Mo in the steel improve the interatomic bonding force of matrix metal through solid solution, and when C, N interstitial atoms exist in the matrix of the steel, the intercrossing solid solution strengthening between the solid-dissolved Cr and Mo and the interstitial C, N atoms can greatly improve the solid solution strengthening effect, so that the high-temperature endurance strength of the container steel is improved. The solid solution atoms can also form Coriolis gas clusters with the dislocations, so that the movement of the dislocations is pinned, and the high-temperature strength of the steel is improved. The microalloy carbon and nitride such as Cr, Mo, Nb and the like can also be precipitated in ferrite or at grain boundaries to block dislocation movement, improve the grain boundary bonding force and inhibit excessive growth of grains, so that the endurance strength of the container steel is improved, and the use requirement under the high-temperature condition is met.
A preparation method of a Cr-Mo low-alloy steel plate for pressure vessels comprises the following steps:
smelting and casting: carrying out primary smelting on molten iron and scrap steel to obtain primary smelting molten steel, then refining and casting the primary smelting molten steel to obtain a casting blank, and then slowly cooling the casting blank;
rolling and water cooling: heating the casting blank after slow cooling to obtain a hot casting blank, and rolling and cooling the hot casting blank to obtain a steel plate;
normalizing heat treatment: and carrying out normalizing heat treatment on the steel plate to obtain the Cr-Mo low-alloy steel plate for the pressure vessel.
In the above method for producing a Cr — Mo low-alloy steel sheet for a pressure vessel, as a preferred embodiment, the cast slab is subjected to slow cooling (slow cooling in a slow cooling pit) before the roll water-cooling step, and then the cast slab subjected to slow cooling is heated in the roll water-cooling step; preferably, the slow cooling time is not less than 48 hours, so that the structural stress and the thermal stress generated in the cooling process of the casting blank are sufficiently reduced, the casting blank is prevented from cracking, and finally, a high-quality casting blank raw material with reasonable components is produced.
In the above method for manufacturing a steel sheet for a Cr — Mo low alloy pressure vessel, as a preferred embodiment, in the smelting and casting step, the molten iron is desulfurized by KR pretreatment before the primary smelting.
In the above method for producing a steel sheet for a Cr — Mo low alloy pressure vessel, as a preferred embodiment, in the step of the smelting and casting, the scrap/(molten iron + scrap) is not more than 8 wt.% so as to limit the content of impurity elements which the scrap may bring in.
In the preparation method of the steel plate for the Cr-Mo low-alloy pressure vessel, as a preferred embodiment, in the smelting and casting step, a single slag process which is simple to operate and saves raw materials is adopted for primary smelting, the alkalinity of final slag is controlled to be 3.0-4.0, preferably, a proper gun position and a proper feeding time are controlled in the smelting process of a converter, the purposes of removing more phosphorus and reducing iron loss are achieved, the components and the temperature of molten steel meet the tapping requirements, and slag materials are added 3-4min before the primary smelting endpoint; in order to make the molten steel components and temperature uniform and reduce the iron content in the slag, the terminal gun pressing time is not less than 60 seconds.
In the above method for producing a steel sheet for a Cr — Mo low-alloy pressure vessel, as a preferred embodiment, in the step of smelting and casting, aluminum-manganese-iron deoxidation is added when the primary molten steel is tapped, an alloy is added when the primary molten steel is tapped to one quarter, and the alloy is added when the primary molten steel is tapped to three quarters; preferably, the alloy is added in alignment with the steel stream impact zone; preferably, the alloy is low phosphorus silicomanganese, ferromolybdenum, high chromium, ferroniobium.
In the above method for manufacturing a steel sheet for a Cr — Mo low-alloy pressure vessel, as a preferred embodiment, in the smelting and casting step, the synthetic slag and the pre-melted slag are added from the beginning of feeding 1/2 steel (i.e., the primary molten steel) to 3/4; preferably, the steel releasing time is not less than 4 minutes, so that sufficient time is ensured for deoxidation alloying.
In the above method for producing a steel sheet for a Cr — Mo low-alloy pressure vessel, as a preferred embodiment, in the smelting and casting step, the refining is LF + RH refining; preferably, during the LF refining process, argon is blown and stirred at the bottom in the whole process, aluminum particles and calcium carbide are used for deoxidation and slag regulation, top slag before leaving the station is yellow white slag or white slag, the retention time of the yellow white slag or the white slag is not less than 10 minutes, and the alkalinity of final slag is controlled to be more than 2.5.
In the above method for producing a steel sheet for a Cr — Mo low alloy pressure vessel, as a preferred embodiment, in the smelting and casting step, the molten steel is soft-blown with argon before RH refining is completed after LF refining, so as to promote floating of inclusions while homogenizing molten steel composition and temperature, the time of LF refining is not less than 45min, the soft-blowing time is not less than 5min, preferably, the time of LF refining is 50 to 60min, and the soft-blowing time is 5 to 8 min.
In the above method for producing a steel sheet for a Cr — Mo low alloy pressure vessel, as a preferable embodiment, in the RH refining, the degassing time is more than 5 min; in the RH refining, calcium-aluminum wires are fed for calcification treatment, soft blowing is carried out after the feeding of the calcium-aluminum wires is finished, and the soft blowing time is not less than 10 min.
In the above method for producing a Cr — Mo low alloy steel sheet for a pressure vessel, according to a preferred embodiment, the RH refining is performed for 50 to 60 minutes.
In the above method for producing a steel sheet for a Cr — Mo low-alloy pressure vessel, as a preferred embodiment, in the step of the smelting and casting, in the casting, a full-course protective casting is adopted, a low superheat degree casting is adopted to reduce columnar crystals, reduce segregation of a cast slab and a zonal structure, a first initial-casting furnace superheat degree is controlled to be within 35 ℃, and a second continuous-casting furnace superheat degree is controlled to be within 25 ℃; preferably, a soft reduction technology is adopted at the solidification tail end of the casting blank of the sector section to break solidification bridges generated by the growth of columnar crystals, and meanwhile, the solidification shrinkage of molten steel is compensated, and the center segregation is reduced.
In the above method for producing a steel sheet for a Cr — Mo low alloy pressure vessel, as a preferred embodiment, in the rolling water cooling step, in order to ensure fine austenite grains and to increase the amount of Cr and Mo dissolved in the steel sheet, the heating temperature is set to 1170 to 1250 ℃ (for example, 1180 ℃, 1190 ℃, 1200 ℃, 1210 ℃, 1220 ℃, 1230 ℃ and 1240 ℃), and the heating and holding time is not less than 40min, so that the complete burning of the billet is ensured. Regulating the gas flow and the flame angle to ensure that the billet is completely burnt, the temperature difference of each point is not more than 30 ℃, and the heating rate is not less than 8 cm/min. Preferably, the hot cast billet is subjected to high pressure water dephosphorization before the rolling.
In the above method for producing a Cr — Mo low alloy steel sheet for a pressure vessel, as a preferred embodiment, in the rolling water-cooling step, the rolling includes rough rolling and finish rolling, and descaling is performed in a first pass, a last pass of the rough rolling and a first pass of the finish rolling to prevent scale intrusion; preferably, the rough rolling stage is a high-temperature high-reduction rolling mode in an austenite recrystallization zone, wherein the high-reduction rolling is rolling with a pass reduction rate of not less than 15% after widening rolling in the rough rolling stage on the premise of ensuring the plate shape and thickness precision, and the pass temperature of the high-reduction rolling is between the rough rolling start temperature and the rough rolling finish temperature, preferably 1120-1150 ℃; on one hand, the grains are continuously refined through repeated occurrence of dynamic recrystallization and static recrystallization, on the other hand, the air holes in the casting blank are welded through high pressure, and the coarse dendrites or columnar crystals are crushed, so that the structure is compact, the components are uniform, and the grains are refined.
In the above method for producing a Cr — Mo low alloy steel sheet for a pressure vessel, as a preferred embodiment, in the rolling water cooling step, the finish rolling step is performed by appropriately controlling the metal deformation system and the temperature system, and on the one hand, the second phase precipitated during the deformation process can suppress the recrystallization of austenite and the growth of grains after the recrystallization by pinning; on the other hand, the austenite grains are flattened, the dislocation density is increased, the nucleation part is increased, the energy required for nucleation is provided, and the ferrite grains are sufficiently refined, so that the purpose of improving the strength and toughness of the steel is achieved, therefore, the finish rolling temperature is controlled to be 860 to 980 ℃ (such as 870 ℃, 880 ℃, 890 ℃, 900 ℃, 910 ℃, 920 ℃, 930 ℃, 940 ℃, 960 ℃, 970 ℃), and 800 to 860 ℃ (such as 810 ℃, 820 ℃, 830 ℃, 840 ℃, 850 ℃); in order to ensure the uniformity of the shape and temperature of the steel sheet after cooling, the steel sheet to be water-cooled must be pre-straightened after rolling and before water cooling.
In the above method for producing a Cr — Mo low alloy steel sheet for a pressure vessel, as a preferred embodiment, in the rolling water cooling step, the water cooling step controls an appropriate cooling temperature and cooling rate to suppress static recrystallization, to retain strain energy storage, to increase ferrite nucleation rate, and to refine the structure. After water cooling, the steel plate is subjected to offline stacking and slow cooling, so that residual stress in the steel plate can be released slowly, the content of hydrogen in the steel plate can be greatly reduced, the heat diffusion effect is fully realized, and the internal quality of the steel plate is improved. When the thickness of the rolled steel plate is 6-14 mm, cooling by air; when the thickness of the rolled steel plate is (14-60) mm, the cooling is ACC water cooling, the water inlet temperature is controlled to be 790-810 ℃ (such as 795 ℃, 800 ℃ and 805 ℃), the water outlet temperature is 640-650 ℃, the cooling rate is controlled to be 6-18 ℃/min, and the steel plate is subjected to hot straightening after water cooling.
In the above method for manufacturing a steel sheet for a Cr — Mo low-alloy pressure vessel, as a preferred embodiment, in the normalizing heat treatment step, the steel sheet has poor structure uniformity and unstable performance after undergoing a TMCP process, so that by the normalizing heat treatment, on the one hand, internal stress is eliminated, segregated elements are redistributed uniformly by diffusion, and a banded structure is improved and eliminated; on the other hand, undissolved carbon and nitride in the steel hinder austenite grains from growing and promote nucleation, a uniform ferrite + pearlite structure is obtained, the structure and performance stability of the steel are improved, and meanwhile, dissolved alloy is uniformly precipitated in the cooling process, so that a good strengthening effect is achieved. The temperature of the normalizing heat treatment is 885-905 ℃ (such as 890 ℃, 900 ℃), and the heat preservation time is 4-10 min (such as 5min, 6min, 7min, 8min, 9 min); the normalizing temperature is too high, and austenite grains can be coarsened; the normalizing temperature is too low, and the carbide can not be completely dissolved. Therefore, the normalizing in the temperature of the invention is beneficial to improving the solid solution of alloy elements and the uniformity of the structure; if the heat preservation time is too long, crystal grains can grow up all the time, and coarsening is caused; if the heat preservation time is too short, austenitization is incomplete, and alloy elements cannot be fully dissolved. Preferably, before normalizing heat treatment, the steel plate is subjected to shot blasting treatment on a shot blasting machine after passing surface inspection.
Compared with the prior art, the invention has the following positive effects:
1) the method carries out solid solution strengthening by adding a small amount of Mn element; the Mo element is added to promote the carbide to be greatly separated out at the grain boundary, plays a role in pinning grain boundary sliding and dislocation movement, prevents dislocation disappearance and subgrain growth, and fully exerts good strengthening effect, particularly high-temperature strength, and the Mo element can greatly improve the high-temperature creep strength of the steel; the Cr element is added to effectively prevent carbide decomposition, carbon diffusion and cementite segregation at high temperature, and ensure the high-temperature mechanical property of the steel plate.
2) The high-quality casting blank raw material with uniform components and high purity is produced by the technologies of low-superheat-degree pouring, soft reduction, casting blank slow cooling and the like. Then, carrying out tissue regulation and control through a controlled rolling and controlled cooling process, strictly controlling the heating temperature and the heat preservation time of the plate blank, ensuring that the casting blank is uniformly and thoroughly burnt when the heat preservation is carried out at a high-temperature section, combining thermoplastic deformation, cooling after rolling and solid phase change by matching with a high-pressure TMCP (thermal mechanical control processing) process, fully playing the effects of precipitation strengthening and fine grain strengthening, and obtaining good tissue and performance matching; finally, the number of precipitated phases is increased, and the precipitated phases are fine and uniformly distributed through normalizing. The steel plate with high flaw detection quality grade and good surface quality is obtained by using less alloy content and a simple process, and has the advantages of reasonable matching of strong plasticity, impact toughness, performance uniformity in the thickness direction and high-temperature mechanical property.
3) The steel plate obtained by the invention has excellent properties: the upper yield strength is more than 370 MPa; the tensile strength is more than 510 MPa; the elongation after fracture is more than 30 percent; the transverse impact energy at 20 ℃ is above 160J; the transverse stretching at the high temperature of 500 ℃ is over 240MPa, and the reduction of area of the steel plate with the thickness of 40-60 mm in the thickness direction is over 45%.
4) The steel grade can well meet the requirements of high strength and toughness, high temperature resistance, fatigue resistance, excellent z-direction performance and good stability of performance among batches under the high-temperature condition, has high flaw detection quality grade and good surface quality, can be used in a high-temperature environment for a long time, and provides technical support for developing products of boilers and pressure vessels which can be widely applied to various high-temperature environments.
Detailed Description
In order to highlight the objects, technical solutions and advantages of the present invention, the present invention is further illustrated by the following examples, which are presented by way of illustration of the present invention and are not intended to limit the present invention. The technical solution of the present invention is not limited to the specific embodiments listed below, and includes any combination of the specific embodiments.
Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. Unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
1) Smelting and continuous casting: pretreating molten iron entering a converter by KR, primarily smelting the molten iron and self-produced scrap steel in the converter to obtain primarily smelted molten steel, then carrying out LF + RH double refining and casting on the primarily smelted molten steel to obtain a casting blank, and then slowly cooling and cleaning the casting blank;
wherein, after the molten iron desulphurization pretreatment is finished, the slag on the surface of the molten iron is completely removed, and the loading amount of the converter scrap steel is strictly controlled to be not more than 8 wt% as much as possible in consideration of certain impurity elements brought by the scrap steel;
in the converter smelting process, a single slag process is adopted for smelting, and the alkalinity of final slag is controlled within the range of 3.0-4.0; controlling proper gun position and feeding time in the smelting process of the converter, finishing adding slag materials 3 minutes before the end point, and keeping the time of pressing a gun at the end point not less than 60 seconds; deoxidizing by adopting aluminum manganese iron, alloying by adopting low-phosphorus silicomanganese, ferromolybdenum, high chromium and ferroniobium, uniformly adding the alloy when molten steel is discharged to 1/4, finishing adding when the molten steel is discharged to 3/4, and adding the alloy aiming at a steel flow impact area; the synthetic slag and the pre-molten slag are added from beginning to 3/4 when the steel 1/2 is discharged. Strictly performing slag blocking operation during tapping, wherein the steel placing time is not less than 4 minutes;
in the LF refining process, argon is blown at the bottom in the whole process and stirred; aluminum particles and calcium carbide are adopted for slag adjustment and deoxidation, top slag before leaving the station is yellow and white slag or white slag, the retention time of the yellow and white slag or the white slag is not less than 10 minutes, and the alkalinity of final slag is controlled to be more than 2.5; the refining time is not less than 45min, and the soft blowing time is not less than 5 min;
in the RH refining process, chemical temperature rise is avoided, pure degassing time is longer than 5min, if RH needs chemical temperature rise, oxygen blowing is carried out for temperature rise after 3 minutes of station entering and circulation, and the aluminum adding amount is determined according to the oxygen blowing amount; after vacuum treatment, calcium-aluminum wire feeding is carried out calcification treatment, and soft blowing time is not less than 10 minutes after wire feeding is finished; the RH smelting period is controlled to be 50-60 minutes and can be adjusted according to actual conditions;
through the steps, the steel plate with the thickness specification of [6-60] mm can be obtained, and the steel plate comprises the following components: c: 0.14 to 0.19%, Si: 0.17-0.35%, Mn: 0.70-0.90%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, Cr: 0.10% -0.25%, Mo: 0.25% -0.35%, Nb: 0.015 to 0.030 percent of the total mass of the molten steel, and the balance of Fe and inevitable impurities. However, the present invention is not limited thereto, and molten steel having the above composition range may be obtained in other manners.
In the continuous casting process, the casting is protected in the whole process, the superheat degree of a first furnace for casting is controlled within 35 ℃, and the superheat degree of a second furnace for continuous casting is controlled within 25 ℃; and a soft reduction technology is adopted at the solidification tail end of the casting blank at the sector section, and the casting blank is slowly cooled for not less than 48 hours so as to fully reduce the structural stress and the thermal stress generated in the cooling process of the casting blank.
2) Rolling and water cooling:
in the heating process, a continuous casting billet is added into a heating furnace for heating, the soaking time of the casting billet is not less than 40min at 1170-1250 ℃, the thorough burning of the billet is ensured, the temperature difference of each point is not more than 30 ℃, and the heating rate is not less than 8 cm/min; after the casting blank is heated (discharged from a heating furnace), carrying out high-pressure water dephosphorization on the hot casting blank;
in the rolling process, in order to prevent the scale from being pressed in, the first pass and the last pass of rough rolling must be descaled, the first pass of finish rolling must be descaled, and the rest passes are selectively input according to the thickness specification and the temperature control requirement, so that the descaling effect is ensured; the rough rolling adopts a high reduction mode, and the finish rolling initial temperature is controlled to be 860-980 ℃; in order to ensure the uniformity of the shape of the steel plate and the temperature after cooling, pre-straightening of the water-cooled steel plate after rolling must be applied.
In the water cooling process, the steel plate with the thickness of [ 6-14 ] mm is subjected to an air cooling process, the steel plate with the thickness of (14-60) mm is subjected to ACC water cooling after being rolled, the water inlet temperature is 790-810 ℃, the water outlet temperature is 640-650 ℃, the cooling rate is controlled to be about 6 ℃/min, and the steel plate is subjected to hot straightening after water cooling.
3) Normalizing heat treatment:
in the normalizing process, shot blasting treatment is carried out on the steel plate after the steel plate is qualified through surface inspection on a shot blasting machine, the normalizing temperature is controlled to be 885-905 ℃, and the heat preservation time is controlled to be 4-10 min.
The chemical compositions of the examples of the invention are shown in table 1; the smelting process parameters of the embodiments of the invention are shown in Table 2; the rolling process parameters of the examples of the invention are shown in table 3; the room temperature tensile test of each example of the invention was carried out in accordance with EN ISO 6892-1:2016, the high temperature tensile test was carried out in accordance with EN ISO 6892-2:2018, the impact test was carried out in accordance with EN ISO 148-1:2016, and the reduction of area test was carried out in accordance with EN 10164-. The normalizing temperature and the heat preservation time are controlled to be different, the mechanical property test is carried out, and the test result is shown in table 6.
TABLE 1 chemical composition (wt%) of steels of examples of the present invention
TABLE 2 smelting Process parameters of steels of examples of the present invention
TABLE 3 Rolling Water-Cooling and Heat treatment Process parameters for steels of examples of the invention
TABLE 4 mechanical Properties of steels of examples of the invention
TABLE 5Z-Direction and high temperature Properties of steels according to examples of the invention
TABLE 6 mechanical properties of different normalizing process parameters of steels according to examples of the invention
In the above Table 6, the same process for preparing the steel sheets having a thickness of 40mm in tables 1 to 3 was carried out for the examples except that the normalizing temperature and time were varied.
Intercepting full thickness metallographic specimen on the 40mm steel sheet of following this application production, corroding in 4% nitric acid alcohol after polishing, polishing the sample, observe the tissue form of its different thickness positions department under the metallographic microscope, can know that the steel sheet thickness direction tissue of this application production is ferrite + pearlite, and the size is tiny, the distribution is even, and tissue banding grade is lower, and the ideal tissue is the prerequisite of assurance ability.
In conclusion, the steel plate for the pressure container has the advantages of high strength and toughness, high temperature resistance, fatigue resistance, excellent z-direction performance, high requirements on structural uniformity in the thickness direction and good stability of performance among batches, high flaw detection quality level and good surface quality, relatively low alloy cost, simple process and easiness in operation. The Cr-Mo low-alloy high-performance steel plate for the pressure vessel is suitable for being applied to boilers and pressure vessel products working in a high-temperature environment.
The method can be realized by upper and lower limit values and interval values of intervals of process parameters (such as temperature, time and the like), and embodiments are not listed.
Conventional technical knowledge in the art can be used for the details which are not described in the present invention.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. The steel plate for the Cr-Mo low-alloy pressure container is characterized by comprising the following components in percentage by mass: c: 0.14 to 0.19%, Si: 0.17-0.35%, Mn: 0.70-0.90%, P: less than or equal to 0.020%, S: less than or equal to 0.008 percent, Cr: 0.10% -0.25%, Mo: 0.25% -0.35%, Nb: 0.015-0.030%, and the balance of Fe and inevitable impurities.
2. The steel sheet for a Cr-Mo low alloy pressure vessel as claimed in claim 1, wherein the steel sheet has a composition, in terms of mass percent, of: c: 0.14 to 0.17%, Si: 0.20 to 0.35%, Mn: 0.70-0.90%, P: less than or equal to 0.018%, S: less than or equal to 0.005 percent, Cr: 0.10% -0.25%, Mo: 0.25% -0.35%, Nb: 0.015-0.030%, and the balance of Fe and inevitable impurities; wherein the mass content of Cr + Mo satisfies the following formula: 0.863C +0.267Mn +2.837 Nb-Cr + Mo-0.975C +0.369Mn +3.405Nb, wherein each element in the formula represents the mass content of the corresponding element in the steel plate;
preferably, Cr: 0.15-0.22%, Mo: 0.28-0.3%, Nb: 0.015-0.025%.
3. A method for producing a Cr-Mo low alloy steel sheet for pressure vessels as claimed in claim 1 or 2, comprising:
smelting and casting: carrying out primary smelting on molten iron and scrap steel to obtain primary molten steel, and then refining and casting the primary molten steel to obtain a casting blank;
rolling and water cooling: heating the casting blank to obtain a hot casting blank, and rolling and cooling the hot casting blank to obtain a steel plate;
normalizing heat treatment: and carrying out normalizing heat treatment on the steel plate to obtain the Cr-Mo low-alloy steel plate for the pressure vessel.
4. The method for producing a steel sheet for a Cr-Mo low alloy pressure vessel according to claim 3, comprising: before the rolling water cooling step, slowly cooling the casting blank, and then heating the slowly cooled casting blank in the rolling water cooling step; preferably, the slow cooling time is not less than 48 hours.
5. The method of manufacturing a steel sheet for a Cr-Mo low alloy pressure vessel according to claim 3, wherein in the step of the smelting and casting, the molten iron is desulfurized using KR pretreatment before the primary smelting;
preferably, the steel scrap/(molten iron + steel scrap) is less than or equal to 8 wt.%;
preferably, the primary smelting is carried out by adopting a single slag process, the alkalinity of final slag is controlled to be 3.0-4.0, and the slag charge is added 3-4min before the primary smelting end point;
preferably, the terminal gun pressure time is not less than 60 seconds;
preferably, aluminum, manganese and iron are added for deoxidation when the primary molten steel is placed, an alloy is added when the primary molten steel is discharged to one quarter, and the alloy is added when the primary molten steel is discharged to three quarters; preferably, the alloy is added in alignment with the steel stream impact zone; preferably, the alloy is low-phosphorus silicomanganese, ferromolybdenum, high-chromium, ferroniobium;
preferably, the synthetic slag and the pre-melted slag are added from beginning to 3/4 when the primary molten steel 1/2 is put in; preferably, the time for the preliminary smelting of molten steel is not less than 4 minutes.
6. The method for producing a steel sheet for a Cr-Mo low alloy pressure vessel as claimed in claim 3, wherein in the step of the smelting casting, the refining is LF + RH refining;
preferably, during the LF refining process, argon is blown and stirred at the bottom in the whole process, aluminum particles and calcium carbide are used for deoxidation and slag adjustment, top slag before the top slag is taken out of a station is yellow white slag or white slag, the retention time of the yellow white slag or the white slag is not less than 10 minutes, and the alkalinity of final slag is controlled to be more than 2.5;
preferably, soft argon blowing is carried out on the molten steel before RH refining is carried out after LF refining is finished, the time of LF refining is not less than 45min, the soft blowing time is not less than 5min, preferably, the time of LF refining is 50-60min, and the soft blowing time is 5-8 min;
preferably, in the RH refining, the degassing time is greater than 5 min; in the RH refining, calcium-aluminum wires are fed for calcification treatment, soft blowing is carried out after the feeding of the calcium-aluminum wires is finished, and the soft blowing time is not less than 10 min; more preferably, the RH refining time is 50 to 60 minutes;
preferably, in the casting, the whole-process protection casting is adopted, the superheat degree of a first furnace for casting is controlled within 35 ℃, and the superheat degree of a continuous casting furnace is controlled within 25 ℃; preferably, a soft reduction technology is adopted at the solidification end of the casting blank of the sector section.
7. The method for producing a steel sheet for a Cr-Mo low-alloy pressure vessel as claimed in claim 3, wherein in the rolling water-cooling step, the heating temperature is 1170-1250 ℃, the heating holding time is not less than 40min, and the heating rate is not less than 8 min/cm; preferably, the hot cast billet is subjected to high pressure water dephosphorization before the rolling.
8. The method for manufacturing a steel sheet for a Cr-Mo low alloy pressure vessel as claimed in claim 3, wherein in the rolling water cooling step, the rolling comprises a rough rolling and a finish rolling stage, preferably, the rough rolling stage is a rolling mode in which an austenite recrystallization zone is subjected to a large reduction; the pass reduction rate of the large reduction rolling is not less than 15 percent;
preferably, the initial rolling temperature of the finish rolling stage is controlled to be 860-980 ℃, and the final rolling temperature of the finish rolling stage is controlled to be 800-860 ℃;
preferably, the steel sheet to be water-cooled is subjected to pre-straightening after rolling and before water-cooling.
9. The method for producing a steel sheet for a Cr-Mo low alloy pressure vessel as claimed in claim 3, wherein in the rolling water cooling step, when the thickness of the steel sheet obtained after rolling is [6 to 14] mm, the cooling is air cooling; when the thickness of the rolled steel plate is 14-60 mm, the cooling is ACC water cooling, the water inlet temperature is controlled to be 790-810 ℃, the water outlet temperature is controlled to be 640-650 ℃, the cooling rate is controlled to be 6-18 ℃/min, and the steel plate is subjected to heat straightening after water cooling.
10. The method for producing a steel sheet for a Cr-Mo low-alloy pressure vessel as claimed in claim 3, wherein in the normalizing heat treatment step, the normalizing heat treatment temperature is 885 to 905 ℃ and the holding time is 4 to 10 min;
preferably, before the normalizing heat treatment, shot blasting is performed on the rolled steel plate on a shot blasting machine after the surface of the rolled steel plate is qualified.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011146929.7A CN112680652A (en) | 2020-10-23 | 2020-10-23 | Cr-Mo low-alloy steel plate for pressure vessel and preparation method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011146929.7A CN112680652A (en) | 2020-10-23 | 2020-10-23 | Cr-Mo low-alloy steel plate for pressure vessel and preparation method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112680652A true CN112680652A (en) | 2021-04-20 |
Family
ID=75447249
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011146929.7A Pending CN112680652A (en) | 2020-10-23 | 2020-10-23 | Cr-Mo low-alloy steel plate for pressure vessel and preparation method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112680652A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113604748A (en) * | 2021-08-18 | 2021-11-05 | 宝武集团鄂城钢铁有限公司 | Thick-specification weather-resistant corrosion-resistant Cr-series alloy steel plate and production method thereof |
| CN116024483A (en) * | 2022-12-30 | 2023-04-28 | 江苏群达机械科技有限公司 | Low-alloy high-strength Cr-Mo steel material and preparation method thereof |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102345066A (en) * | 2011-10-21 | 2012-02-08 | 莱芜钢铁集团有限公司 | Steel used for pressure container and preparation method thereof |
| KR20170075135A (en) * | 2015-12-22 | 2017-07-03 | 주식회사 포스코 | Steel plate for pressure vessel having high strength and method for manufacturing the same |
| CN107177783A (en) * | 2017-07-21 | 2017-09-19 | 东北大学 | A kind of Ultra-fine Grained martensite ferrite dual phase steel being distributed with bimodal ferrite crystal grain and its production technology |
| JP2020019976A (en) * | 2018-07-30 | 2020-02-06 | 日本製鉄株式会社 | Seamless steel pipe for hot forging |
| CN111004978A (en) * | 2020-01-02 | 2020-04-14 | 鞍钢股份有限公司 | Low-alloy high-temperature-resistant pressure vessel steel plate and production method thereof |
-
2020
- 2020-10-23 CN CN202011146929.7A patent/CN112680652A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102345066A (en) * | 2011-10-21 | 2012-02-08 | 莱芜钢铁集团有限公司 | Steel used for pressure container and preparation method thereof |
| KR20170075135A (en) * | 2015-12-22 | 2017-07-03 | 주식회사 포스코 | Steel plate for pressure vessel having high strength and method for manufacturing the same |
| CN107177783A (en) * | 2017-07-21 | 2017-09-19 | 东北大学 | A kind of Ultra-fine Grained martensite ferrite dual phase steel being distributed with bimodal ferrite crystal grain and its production technology |
| JP2020019976A (en) * | 2018-07-30 | 2020-02-06 | 日本製鉄株式会社 | Seamless steel pipe for hot forging |
| CN111004978A (en) * | 2020-01-02 | 2020-04-14 | 鞍钢股份有限公司 | Low-alloy high-temperature-resistant pressure vessel steel plate and production method thereof |
Non-Patent Citations (3)
| Title |
|---|
| 俞海明: "《电炉钢水的炉外精炼技术》", 31 August 2010, 冶金工业出版社 * |
| 曹阳等: "热风炉用新型容器钢板的试制开发", 《山东冶金》 * |
| 王雅贞等: "《氧气顶吹转炉炼钢工艺与设备》", 31 March 1983, 冶金工业出版社 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113604748A (en) * | 2021-08-18 | 2021-11-05 | 宝武集团鄂城钢铁有限公司 | Thick-specification weather-resistant corrosion-resistant Cr-series alloy steel plate and production method thereof |
| CN113604748B (en) * | 2021-08-18 | 2022-05-13 | 宝武集团鄂城钢铁有限公司 | Thick-specification weather-resistant corrosion-resistant Cr alloy steel plate and production method thereof |
| CN116024483A (en) * | 2022-12-30 | 2023-04-28 | 江苏群达机械科技有限公司 | Low-alloy high-strength Cr-Mo steel material and preparation method thereof |
| CN116024483B (en) * | 2022-12-30 | 2023-09-15 | 江苏群达机械科技有限公司 | Low-alloy high-strength Cr-Mo steel material and preparation method thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112048665B (en) | Steel plate for polar region ocean engineering and preparation method thereof | |
| CN107385353B (en) | A kind of ocean platform special thickness EH36 steel plate of 250mm and preparation method thereof | |
| CN105861941A (en) | Ultra-thick steel plate for hydrogen-contacting equipment and preparation method of ultra-thick steel plate | |
| CN112981239B (en) | Quenched and tempered low-carbon alloy steel and manufacturing method thereof | |
| CN109136738A (en) | A kind of high-strength low-temperature-resistant Ship Structure steel plate and preparation method thereof | |
| CN113846260B (en) | Production method of high-strength steel plate for engineering machinery | |
| CN109338215A (en) | One kind 8~25mm thickness low yield strength ratio tank car high strength steel plate and its manufacturing method | |
| CN107937807A (en) | 770MPa grades of low-welding crack-sensitive pressure vessel steels and its manufacture method | |
| WO2022228216A1 (en) | Steel for high-temperature carburized gear shaft and manufacturing method for steel | |
| CN114277314A (en) | Corrosion-resistant high-strength steel plate for high heat input welding ocean engineering and preparation method thereof | |
| CN110029268A (en) | A kind of low-temperature pressure container 09MnNiDR steel plate and manufacturing method for protecting center portion low-temperature flexibility | |
| CN112680652A (en) | Cr-Mo low-alloy steel plate for pressure vessel and preparation method thereof | |
| CN113862446B (en) | Production method of X70 pipeline steel with high heating temperature | |
| CN111996462B (en) | Longitudinal variable-thickness ultrahigh-strength ship board and production method thereof | |
| CN115786812B (en) | 9Ni steel plate for large-thickness low-yield-ratio LNG storage tank and production method thereof | |
| CN115747657B (en) | HY950CF steel plate for high-strength hydroelectric engineering and production method thereof | |
| WO2024001078A1 (en) | 80 mm thick 690 mpa-grade ultra-high strength and toughness marine steel plate and preparation method therefor | |
| CN115074630B (en) | FH36 grade ocean engineering steel with high ductility and manufacturing method | |
| CN114875331B (en) | 610 MPa-grade thick steel plate with excellent core fatigue performance and production method thereof | |
| CN114058960B (en) | High-strength high-toughness easy-welding nano steel with thickness of 25-60 mm and thickness of 1000MPa and preparation method thereof | |
| CN114480809A (en) | 500 MPa-grade crack arrest steel plate and production method thereof | |
| CN110964978B (en) | Steel plate for engineering machinery and preparation method thereof | |
| RU2816465C1 (en) | Steel sheet for use in marine construction in polar regions and method of its production | |
| CN115386802B (en) | Non-quenched and tempered steel for 10.9-grade large-specification wind power bolts and production method thereof | |
| CN116377328B (en) | X60 steel plate and manufacturing method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20210420 |