CN114635071B - Smelting method of martensite heat-resistant steel - Google Patents
Smelting method of martensite heat-resistant steel Download PDFInfo
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Abstract
The invention relates to a smelting method of novel martensite heat-resistant steel G115 for an advanced ultra-supercritical thermal power generating unit, and belongs to the technical field of heat-resistant steel smelting. The smelting method comprises the process flows of EAF electric furnace smelting, LF refining, VD vacuum treatment, die casting steel ingot, forging steel ingot into a consumable electrode and electroslag remelting, and the produced G115 meets the standards of CSTM 00017-2017, Q/OAPD 2753-2017, Q/OAPD 2253-2017 and the like by accurately controlling the chemical components of steel, strictly controlling the gas content, improving the purity of the steel and greatly improving the segregation of W. Through strict performance evaluation and welding evaluation of related users, G115 produced by the smelting method completely has the condition of engineering application of the ultra-supercritical unit at 630 ℃.
Description
Technical Field
The invention belongs to the technical field of metallurgy, mainly relates to a method for smelting martensite heat-resistant steel, and particularly relates to a method for smelting martensite heat-resistant steel with the model number of G115.
Background
Along with the rapid development of economy, the energy demand is higher and higher, thermal power generation is an important component of energy in China, but a series of environmental pollution problems caused by thermal power generation are more and more serious in conflict with ecological civilization construction and environmental protection concept in China, so that the demand on high-efficiency and low-emission thermal power generating units with high parameters is more and more urgent. The higher the steam temperature and pressure parameters of coal-fired power generation, the lower the coal-fired energy consumption, the less pollutant emissions, but the higher the performance requirements on the material. The P92 used by the 600 ℃ parameter ultra-supercritical unit can not meet the requirements of a higher parameter unit. To build a 630 ℃ ultra-supercritical unit with parameters, the requirement on the high-temperature resistance of the material must reach 650 ℃.
9Cr-3W-3CoVNbCuBN (G115) is a novel martensite heat-resistant steel (Chinese patent CN 103045962B), the heat-resistant steel adopts a composite strengthening principle, the high-temperature long-time aging structure stability, the high-temperature endurance strength and the oxidation resistance of the heat-resistant steel are all greatly higher than P92, the heat-resistant steel is suitable for long-time use under a high-pressure working condition at the temperature below 650 ℃, and comparative research shows that the endurance strength and the oxidation resistance of the G115 at 650 ℃ are superior to the performance of the P92 at 600 ℃. Through system research and development in more than ten years, various problems of G115 in industrial production are solved, more than 500 tons of G115 are successfully manufactured in batches at the present stage, and through performance evaluation and welding evaluation of related users, design units and scientific research institutes, the conditions of engineering application can be completely met, and CSTM standards and enterprise standards such as "martensite heat-resistant steel 08Cr9W3Co3VNbCuBN (G115) seamless steel tube for CSTM 00017-2017 power station", "novel martensite heat-resistant steel 08Cr9W3Co3 VNuBN (G115) tube blank and section bar for Q/OAPD 2753-2017 power station" and novel martensite heat-resistant steel 08Cr9W3Co3VNbCuBN (G115) seamless steel tube for Q/OAPD 2253-2017 power station "are drawn up; at present, G115 produced by people passes the review of the national boiler pressure vessel standardization technical committee, and is the only enterprise with the capability of producing products such as G115 steel pipes, tube blanks, forgings and the like which meet relevant standards.
There are also related studies related to G115 in the prior art, as follows:
the Chinese patent No. CN103045962B is an invention patent of G115, mainly relates to the aspects of component design, strengthening concept, manufacturing method, performance characteristics and the like of G115, and does not relate to a specific smelting method.
Chinese patent CN108998650A relates to a manufacturing method of a G115 large-caliber thick-wall seamless steel tube of a 630 ℃ ultra-supercritical unit, only relates to a tube manufacturing process of the G115 large-caliber thick-wall seamless steel tube, does not have a smelting process, and mainly utilizes the existing G115 tube blank to complete a production process of extruding and manufacturing the tube on a 3.6 ten thousand ton extruding machine.
Chinese patent CN108950148A relates to a method for improving radial structure and performance uniformity of G115 large-caliber thick-wall pipe, but does not relate to a smelting method of G115.
The G115 martensite heat-resistant steel produced by the technology has more problems in industrial mass production and engineering application, for example, in the aspects of component optimization, structure improvement, performance improvement, welding heat influence area microscopic defect solving and the like, the product can not meet the relevant enterprise standard and industry standard, and can not be applied to 630 ℃ ultra-supercritical demonstration power station engineering.
Disclosure of Invention
The invention aims to provide a method for smelting G115 martensite heat-resistant steel, which comprehensively solves a series of problems in industrial mass production and engineering application for the first time.
The invention is realized by the following technical scheme:
the invention provides a smelting method of martensite heat-resistant steel, which comprises the following steps:
s1, sequentially carrying out electric arc furnace smelting, ladle refining furnace refining, VD vacuum furnace treatment and die casting on raw materials to obtain a steel ingot;
s2, forging the steel ingot to obtain a consumable electrode;
s3, carrying out electroslag remelting on the consumable electrode to obtain an electroslag ingot;
s4, annealing the electroslag ingot at 750-780 ℃ to obtain the martensite heat-resistant steel;
the raw materials in the step S1 comprise metal Cr, metal Co, metal W, metal Nb, metal Cu and pure Fe.
Preferably, in the electric arc furnace smelting in the step S1, argon is used as the inert gas for stirring at the bottom of the electric arc furnace; controlling the content of carbon element not more than 0.04% and the content of phosphorus element not more than 0.003% at the end point; tapping 100% and stopping slag; the oxygen activity of the steel tapping is 1000-1400 ppm; deoxidizing by adopting Al, and adding 0.25-0.35 wt% of aluminum ingot; controlling the tapping temperature to be 1660-1680 ℃.
As a preferred scheme, in the refining of the ladle refining furnace in the step S1, low-carbon lime (the carbon content is lower than 1%) is supplemented in batches by 0.25 to 0.75wt% and added in 1 to 3 batches; deoxidizing the slag surface by using SiFe powder; increasing the stirring force of Ar gas, wherein the Ar gas pressure control is based on the principle that the molten steel does not turn over the slag surface; feeding Al for deoxidation according to the sampling analysis result, wherein the addition amount of Al is less than or equal to 0.035wt%; adding Cr, co, copper plate and ferrotungsten at a temperature not lower than 1600 ℃ in batches, wherein the addition amount of each batch is not more than 0.6 ton; adding 0.10-0.18 wt% of ferroboron according to the analysis result before hoisting, and measuring that the content of boron in the molten steel is 0.012-0.020%; the temperature of the crane ladle is 1680-1720 ℃.
Preferably, in the VD vacuum furnace treatment in the step S1, the vacuum degree is controlled to be 65.0-68.0 Pa, and the holding time is not less than 20min; filling Ar gas to strengthen stirring, wherein the pressure of the Ar gas is 0.20-0.60 Mpa; hydrogen is determined, H is less than or equal to 1.0ppm; controlling the pressure of Ar gas to be supplied to be 0.20-0.40 Mpa before the ladle, and preventing the molten steel from being exposed in the air; temperature of the crane ladle: 1555 to 1565 ℃.
Preferably, in the die casting in the step S1, a protective cover is used to protect a casting nozzle, and argon is used to protect casting during casting, wherein the flow of argon is 2 to 5Nm 3 H; casting by adopting a down-pouring method, and filling Ar into an ingot mold before casting; after finishing the injection, adding the heating agent and the rice ash.
The protective cover is a sealing device communicated with argon, can ensure that molten steel does not contact with air before entering the middle injection pipe after flowing out from the water gap and is always in an argon protective atmosphere, and prevents the molten steel from absorbing oxygen and nitrogen from the air.
As a further preferable scheme, the heat generating agent is at least one of coke, aluminum, silicon and silicon-calcium alloy.
As a preferred scheme, in the forging in the step S2, the heating temperature of the steel ingot is 1140-1180 ℃, the heating rate is 50-100 ℃/h, and the heat preservation time is more than or equal to 8 hours; the forging temperature is 1100 ℃, and the finish forging temperature is 900 ℃; upsetting to 1/2 of the original height, and drawing to form an octagonal body with the diameter of 800-950 mm; upsetting and drawing out once every fire, and upsetting and drawing out at least three times; the forging is carried out for more than three times, the heating temperature is 1140-1180 ℃ after each time of remelting, and the heat preservation time is more than or equal to 3 hours.
Preferably, step S3 isIn the electroslag remelting, before the electroslag remelting, the consumable electrode is peeled until the surface is bright, and the consumable electrode is seen as a natural metal color; adopting Ar gas protective atmosphere; adopts quaternary slag system CaF 2 :Al 2 O 3 CaO, mgO =72%, 18%, 5%; controlling the addition of the quaternary slag system to be 5.0-6.5 wt%; the smelting voltage is 40-55V; the smelting current is 19000-22000A; the melting speed is controlled to be 5.0 to 9.5Kg/min; the flow rate of the cooling water is controlled to be 180-200 m 3 /h。
Preferably, the annealing time in step S4 is not less than 1.5min/mm.
The invention has the beneficial effects that:
the G115 smelting method provided by the invention is a method which can be successfully implemented in industrial mass production, the chemical components, the structures, the performances and the like of the G115 martensite heat-resistant steel smelted according to the method all meet CSTM standards and enterprise standards of 08Cr9W3Co3VNbCuBN (G115) seamless steel tube for CSTM 00017-2017 power station, 08Cr9W3Co3VNbCuBN (G115) seamless steel tube for Q/OAPD 2753-2017 power station, 08Cr9W3Co3VNbCuBN (G115) seamless steel tube for Q/OAPD 2253-2017 power station and the like, and through welding evaluation of users, the problem that the G115 produced by the early G115 smelting method has microscopic defects of a welding heat influence area is solved, and the method has conditions of application in 630 ℃ ultra-critical demonstration engineering.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the invention.
A smelting method of novel martensite heat-resistant steel G115 comprises the following process flows of:
smelting by an EAF electric furnace, LF refining, VD vacuum treatment and a die-cast steel ingot;
b. forging the steel ingot into a consumable electrode;
c. electroslag remelting;
d. annealing;
according to the smelting method of the G115 martensite heat-resistant steel, the EAF electric furnace smelting process in the step a preferably comprises the following process requirements:
a. the method adopts low-carbon low-nickel raw materials such as metal Co, metal W, metal Nb, metal Cu, metal Cr, pure Fe and the like, and the low carbon and the low nickel are used for ensuring good lasting strength and welding performance;
b. argon is used as inert gas for stirring at the bottom of the electric furnace;
c. the end point control C is less than or equal to 0.04 percent and P is less than or equal to 0.003 percent;
d. tapping 100% and stopping slag;
e. controlling the oxygen activity of the tapping at 1000-1400 ppm;
f. al is adopted for deoxidation, 0.25-0.35 wt% of aluminum ingot is added according to the oxygen activity, the limit is 1200ppm of the oxygen activity, for example, about 0.25wt% of Al is added when the oxygen activity is less than 1200ppm, the oxygen activity is more than 1200ppm, about 0.30wt% of Al is added, but the total amount of Al is not more than 0.35wt%;
g. tapping temperature: 1660-1680 ℃.
According to the smelting method of the G115 martensite heat-resistant steel, the LF refining process in the step a preferably comprises the following process requirements:
a. replenishing low-carbon lime 0.25-0.75% in batches, and adding the low-carbon lime into the mixture for 1-3 batches;
b. SiFe powder is used for deoxidizing the slag surface, and C powder is strictly forbidden;
c. increasing the stirring strength of Ar gas, wherein the pressure of the Ar gas is 0.2-0.8MPa, and the pressure control of the Ar gas takes the principle that the molten steel does not turn over the slag surface;
d. according to the sampling analysis result, feeding Al for deoxidation, wherein the adding amount of Al is less than or equal to 0.035%, when the oxygen activity is more than or equal to 1000ppm and the Al is less than or equal to 0.025%, adding Al, and the final content of Al is less than or equal to 0.035%;
e. adding metal Cr, metal Co, copper plates and ferrotungsten in batches, wherein the adding amount of 40 tons of molten steel in each batch is not more than 0.6 ton (the adding condition is that the temperature is more than or equal to 1600 ℃);
f. before hoisting, adding 0.10-0.1wt8% of ferroboron according to the analysis result until the boron content in the molten steel is measured to be 0.012-0.020 wt%;
g. temperature of the crane ladle: 1680-1720 ℃.
According to the smelting method of the G115 martensite heat-resistant steel, the VD vacuum treatment process in the step a preferably comprises the following process requirements:
a. the vacuum degree is 66.7Pa, and the holding time is more than or equal to 20min;
b. filling Ar gas to strengthen stirring, wherein the pressure of the Ar gas is 0.20-0.60 Mpa;
c. hydrogen is determined, and H is less than or equal to 1.0ppm;
d. the argon supply intensity is strictly controlled before the ladle is hung, the Ar gas pressure is 0.20-0.40 Mpa, the molten steel is not exposed in the air, and the nitrogen increase is prevented;
e. temperature of the crane ladle: 1555-1565 ℃;
according to the smelting method of the G115 martensite heat-resistant steel, preferably, the process of die casting the steel ingot in the step a comprises the following process requirements:
a. a special protective cover is adopted to protect a casting nozzle, argon is used for protecting casting in the casting process, and the flow of the argon is controlled to be 2-5 Nm 3 /h；
b. Casting by a down-pouring method, and filling Ar into an ingot mold before casting;
c. adding a heating agent and rice ash after finishing injection;
according to the smelting method of the G115 martensite heat-resistant steel, preferably, the process of forging the steel ingot into the consumable electrode in the step b comprises the following process requirements:
a. the steel ingot heating temperature is 1140-1180 ℃, the heating rate is 50-100 ℃/h, and the heat preservation time is more than or equal to 8 hours;
b. the open forging temperature is 1100 ℃, and the finish forging temperature is 900 ℃;
c. upsetting to 1/2 of the original height in a special patent upsetting device (see Chinese patent CN 107552699A) in a 6000-ton quick forging machine, and drawing to an octagonal block with a proper diameter of 800-950 mm;
the upsetting device is a disk-shaped device with a handle, the thickness is 500-700 mm, the weight is about 20 tons, the upper surface and the lower surface of a steel ingot are smooth during upsetting, the stress is uniform (the upsetting of 13.5 tons of steel ingots can be completed at one time without moving the steel ingot), and the defects of bending, inclination and the like do not occur.
d. Upsetting and drawing out once every fire, upsetting and drawing out for at least three times together, and fully crushing cast tissues to eliminate large tungsten-rich phase segregation;
e. the forging is carried out for more than three times, the reheating temperature is 1140-1180 ℃ each time, and the heat preservation time is more than or equal to 3 hours (the specific time is determined according to the specification of the intermediate billet).
According to the smelting method of the G115 martensite heat-resistant steel, the process of electroslag remelting in the step c preferably comprises the following process requirements:
a. before electroslag remelting, the surface of a consumable electrode is treated, for example, the consumable electrode is peeled until the surface is bright, the consumable electrode is natural, and the consumable electrode cannot be blackened and blued to prevent the increase of boron burning loss;
b. adopting Ar gas protective atmosphere to prevent nitrogen increase in the electroslag remelting process;
c. adopts quaternary slag system CaF 2 :Al 2 O 3 MgO =72%, 18%, 5%, which is helpful for the stabilization of electroslag process, the removal of non-metallic inclusion, the elimination of tungsten-rich phase bulk segregation, the improvement of surface quality, and can ensure the components, inclusion, micro segregation of steel and the surface quality of steel ingot to reach the optimum state;
d. according to different ingot types, the slag amount is controlled to be 5.0-6.5%;
e. the smelting voltage is 40-55V;
f. the smelting current is 19000-22000A;
g. controlling the melting speed to be 5.0-9.5 Kg/min according to different ingot types;
h. the cooling water is boiled to the maximum, and the flow of the cooling water is controlled to be 180-200 m 3 And/h, rapid forced water cooling can reduce component segregation and promote impurity redistribution, and the slag crust on the surface of the electroslag ingot can be solidified into thin and uniform slag crust due to forced water cooling, so that the surface quality of the electroslag ingot is better.
According to the smelting method of the G115 martensite heat-resistant steel, the process of electroslag remelting in the step d preferably comprises the following process requirements:
and (3) after the electroslag ingot is demoulded, the electroslag ingot enters a furnace and exits the furnace within 4 hours, the annealing temperature is 750-780 ℃, the annealing time is determined according to the size of the ingot (the annealing time is determined according to the speed of not less than 1.5 min/mm), the furnace is cooled to be below 100 ℃, and the electroslag ingot is discharged from the furnace and cooled by air.
Example 1
The embodiment provides a smelting method of novel martensite heat-resistant steel G115, which comprises the following process flows of:
s1, sequentially carrying out smelting on the raw materials in an electric arc furnace of 40 tons, refining in a ladle refining furnace, treating in a VD (vacuum distillation) vacuum furnace and die casting to obtain 3 steel ingots of 13.5 tons;
wherein, during smelting in an electric arc furnace, the raw materials adopt low-carbon low-nickel raw materials such as metal Cr, pure Fe and the like; argon is used for stirring inert gas at the bottom of the electric arc furnace; controlling the content of carbon element not more than 0.04% and the content of phosphorus element not more than 0.003% at the end point; tapping 100% of slag is blocked; the oxygen activity of the steel tapping is 1000-1400 ppm; al is adopted for deoxidation, and 0.25 to 0.35 percent of aluminum ingot is added according to the oxygen activity; target temperature: 1660 to 1680 ℃;
when refining in a ladle refining furnace, adding low-carbon lime 0.25-0.75 wt% per batch in batches according to slag conditions, and adding 1-3 batches; siFe powder for deoxidizing slag surface; increasing the stirring force of Ar gas, wherein the Ar gas pressure control is based on the principle that the molten steel does not turn over the slag surface; feeding Al for deoxidation according to the sampling analysis result, wherein the addition amount of Al is less than or equal to 0.035wt%; adding Cr, co, copper plate and ferrotungsten at a temperature not lower than 1600 ℃ in batches, wherein the addition amount of each batch is not more than 0.6 ton; adding 0.10-0.18% of ferroboron according to the analysis result before hoisting, and measuring the boron content in the molten steel to be 0.012-0.020%; the temperature of the ladle is 1680-1720 ℃.
When the vacuum is processed in a VD vacuum furnace, the vacuum degree is 66.7Pa, and the holding time is more than or equal to 20min; filling Ar gas to strengthen stirring, wherein the pressure of the Ar gas is 0.20-0.60 Mpa; hydrogen is determined, H is less than or equal to 1.0ppm; controlling the pressure of Ar gas to be 0.20-0.40 Mpa before the ladle is hung so as not to expose the molten steel in the air; temperature of the crane ladle: 1555 to 1565 ℃.
During the die casting time, a special protective cover is adopted to protect a casting nozzle, and argon is used for protection casting in the casting process, wherein the argon flow is 2-5 Nm 3 H; casting by using a bottom pouring method, wherein a steel ingot is cast before castingFilling Ar into the mould; after finishing the injection, adding the heating agent and the rice ash.
S2, carrying out three-time upsetting, drawing and forging on the steel ingot obtained in the step S1 in a 6000-ton quick forging machine to obtain a consumable electrode rod with phi 840;
wherein the steel ingot heating temperature is 1140-1180 ℃, the heating rate is 50-100 ℃/h, and the heat preservation time is more than or equal to 8 hours; the open forging temperature is 1100 ℃, and the finish forging temperature is 900 ℃; a6000-ton quick forging machine adopts a special patent upsetting device (see Chinese patent CN107552699A, a manufacturing method of a large-scale upsetting device), upsetting is carried out to 1/2 of the original height, and then the machine is drawn out to an octagonal with the diameter of 800-950 mm; upsetting and drawing out once per fire, and upsetting and drawing out for at least three times; forging for more than three times, and carrying out remelting and heating at 1140-1180 ℃ each time for more than or equal to 3 hours.
S3, carrying out electroslag remelting on the consumable electrode to obtain an electroslag ingot with phi of 1000;
before electroslag remelting, peeling the consumable electrode until the surface is bright and the natural color of metal is seen; adopting Ar protective atmosphere; adopts quaternary slag system CaF 2 :Al 2 O 3 CaO, mgO =72%, 18%, 5%; the slag amount is 5.0-6.5%; the smelting voltage is 40-55V; the smelting current is 19000-22000A; the melting speed is controlled to be 5.0 to 9.5Kg/min; and (5) cooling water is boiled to the maximum, and water cooling is rapidly forced.
And S4, annealing the electroslag ingot at 770 ℃ for 25h to obtain the martensite heat-resistant steel.
The chemical compositions of the martensitic heat-resistant steels obtained in this example are shown in table 1, the low magnification test results are shown in table 2, and the inclusion rating results are shown in table 3. The mechanical properties of the large-caliber pipe formed by forging and hot extrusion of the electroslag ingot through the pipe billet are shown in table 4, and the tensile property and the impact property of the large-caliber pipe are far higher than the standard requirements.
Example 2
The embodiment provides a smelting method of novel martensite heat-resistant steel G115, which comprises the following process flows of:
s1, sequentially carrying out 40-ton electric arc furnace smelting, ladle refining, VD vacuum furnace treatment and die casting on the raw materials to obtain 3 steel ingots of 13.5 tons;
wherein, during smelting in an electric arc furnace, the raw materials adopt low-carbon and low-nickel raw materials such as metal Cr, pure Fe and the like; argon is used for stirring inert gas at the bottom of the electric arc furnace; controlling the content of carbon element not more than 0.04% and the content of phosphorus element not more than 0.003% at the end point; tapping 100% and stopping slag; the oxygen activity of the steel tapping is 1000-1400 ppm; al is adopted for deoxidation, and 0.25 to 0.35 percent of aluminum ingot is added according to the oxygen activity; target temperature: 1660-1680 ℃;
when refining in a ladle refining furnace, adding low-carbon lime 0.25-0.75%/batch in batches according to slag conditions, and adding 1-3 batches; siFe powder for deoxidizing slag surface; increasing the stirring force of Ar gas, wherein the Ar gas pressure control is based on the principle that the molten steel does not turn over the slag surface; feeding Al for deoxidation according to the sampling analysis result, wherein the addition amount of Al is less than or equal to 0.035%; adding Cr, co, copper plate and ferrotungsten at a temperature not lower than 1600 ℃ in batches, wherein the addition amount of each batch is not more than 0.6 ton; adding 0.10-0.18% of ferroboron according to the analysis result before hoisting, and measuring that the content of boron in the molten steel is 0.012-0.020%; the temperature of the ladle is 1680-1720 ℃.
When the vacuum is processed in a VD vacuum furnace, the vacuum degree is 66.7Pa, and the holding time is more than or equal to 20min; filling Ar gas to strengthen stirring, wherein the pressure of the Ar gas is 0.20-0.60 Mpa; hydrogen is determined, and H is less than or equal to 1.0ppm; controlling the pressure of Ar gas to be 0.20-0.40 Mpa before the ladle is hung so as not to expose the molten steel in the air; temperature of the crane ladle: 1555 to 1565 ℃.
During the die casting time, a special protective cover is adopted to protect a casting nozzle, and argon is used for protection casting in the casting process, wherein the argon flow is 2-5 Nm 3 H; casting by a down-pouring method, and filling Ar into an ingot mold before casting; after finishing the injection, adding the heating agent and the rice ash.
S2, carrying out three-time upsetting, drawing and forging on the steel ingot obtained in the step S1 in a 6000-ton quick forging machine to obtain a consumable electrode bar with phi 720;
wherein the steel ingot heating temperature is 1140-1180 ℃, the heating rate is 50-100 ℃/h, and the heat preservation time is more than or equal to 8 hours; the forging temperature is 1100 ℃, and the finish forging temperature is 900 ℃; a6000-ton quick forging machine adopts a special patent upsetting device (see Chinese patent CN107552699A, a manufacturing method of a large-scale upsetting device), upsetting is carried out to 1/2 of the original height, and then the machine is drawn out to an octagonal with the diameter of 800-950 mm; upsetting and drawing out once every fire, and upsetting and drawing out at least three times; forging for more than three times, and carrying out remelting and heating at 1140-1180 ℃ each time, wherein the heat preservation time is more than or equal to 3 hours.
S3, carrying out electroslag remelting on the consumable electrode to obtain an electroslag ingot with phi of 900;
before electroslag remelting, peeling the consumable electrode until the surface is bright and the natural color of metal is seen; adopting Ar protective atmosphere; adopts quaternary slag system CaF 2 :Al 2 O 3 CaO, mgO =72%, 18%, 5%; the slag amount is 5.0-6.5%; the smelting voltage is 40-55V; the smelting current is 19000 to 22000A; the melting speed is controlled to be 5.0 to 9.5Kg/min; and (5) cooling water is boiled to the maximum, and water cooling is rapidly forced.
And S4, annealing the electroslag ingot at 770 ℃ for 23 hours to obtain the martensite heat-resistant steel.
The chemical compositions of the martensitic heat-resistant steels obtained in this example are shown in table 1, the low-magnification test results are shown in table 2, and the inclusion rating results are shown in table 3. The mechanical properties of the large-caliber pipe formed by forging and hot extrusion of the electroslag ingot through the pipe billet are shown in table 4, and the tensile property and the impact property of the large-caliber pipe are far higher than the standard requirements.
Example 3
The embodiment provides a smelting method of novel martensite heat-resistant steel G115, which comprises the following process flows of:
s1, sequentially carrying out 40-ton electric arc furnace smelting, ladle refining, VD vacuum furnace treatment and die casting on the raw materials to obtain 3 steel ingots of 13.5 tons;
wherein, during smelting in an electric arc furnace, the raw materials adopt low-carbon low-nickel raw materials such as metal Cr, pure Fe and the like; argon is used for stirring inert gas at the bottom of the electric arc furnace; controlling the content of carbon element not more than 0.04% and the content of phosphorus element not more than 0.003% at the end point; tapping 100% of slag is blocked; the oxygen activity of the steel tapping is 1000-1400 ppm; al is adopted for deoxidation, and 0.25 to 0.35 percent of aluminum ingot is added according to the oxygen activity; target temperature: 1660-1680 ℃;
when refining in a ladle refining furnace, adding low-carbon lime 0.25-0.75%/batch in batches according to slag conditions, and adding 1-3 batches; siFe powder for deoxidizing slag surface; increasing the stirring force of Ar gas, wherein the Ar gas pressure control is based on the principle that the molten steel does not turn over the slag surface; feeding Al for deoxidation according to the sampling analysis result, wherein the addition amount of the Al is less than or equal to 0.035%; adding Cr, co, copper plate and ferrotungsten at a temperature not lower than 1600 ℃ in batches, wherein the addition amount of each batch is not more than 0.6 ton; adding 0.10-0.18% of ferroboron according to the analysis result before hoisting, and measuring that the content of boron in the molten steel is 0.012-0.020%; the temperature of the ladle is 1680-1720 ℃.
When the VD is processed in a vacuum furnace, the vacuum degree is 66.7Pa, and the holding time is more than or equal to 20min; charging Ar gas to strengthen the stirring, wherein the pressure of the Ar gas is 0.20-0.60 Mpa; hydrogen is determined, and H is less than or equal to 1.0ppm; controlling the pressure of Ar gas to be 0.20-0.40 Mpa before the ladle is hung so as not to expose the molten steel in the air; temperature of the crane ladle: 1555 to 1565 ℃.
During the die casting time, a special protective cover is adopted to protect a casting nozzle, and argon is used for protection casting in the casting process, wherein the argon flow is 2-5 Nm 3 H; casting by adopting a down-pouring method, and filling Ar into an ingot mold before casting; after finishing the injection, adding the heating agent and the rice ash.
S2, carrying out three-time upsetting, drawing and forging on the steel ingot obtained in the step S1 in a 6000-ton quick forging machine to obtain a consumable electrode bar with phi 720;
wherein the steel ingot heating temperature is 1140-1180 ℃, the heating rate is 50-100 ℃/h, and the heat preservation time is more than or equal to 8 hours; the forging temperature is 1100 ℃, and the finish forging temperature is 900 ℃; a6000-ton quick forging machine adopts a special patent upsetting device (see Chinese patent CN107552699A, a manufacturing method of a large-scale upsetting device), upsetting is carried out to 1/2 of the original height, and then the machine is drawn out to an octagonal with the diameter of 800-950 mm; upsetting and drawing out once every fire, and upsetting and drawing out at least three times; forging for more than three times, and carrying out remelting and heating at 1140-1180 ℃ each time, wherein the heat preservation time is more than or equal to 3 hours.
S3, carrying out electroslag remelting on the consumable electrode to obtain an electroslag ingot of phi 1200;
before electroslag remelting, peeling the consumable electrode until the surface is bright and the natural color of metal is seen; adopting Ar protective atmosphere; adopts quaternary slag system CaF 2 :Al 2 O 3 CaO, mgO =72%, 18%, 5%; the amount of slag is5.0 to 6.5 percent; the smelting voltage is 40-55V; the smelting current is 19000-22000A; the melting speed is controlled to be 5.0 to 9.5Kg/min; and (5) cooling water is boiled to the maximum, and water cooling is rapidly forced.
And S4, annealing the electroslag ingot at 770 ℃ for 30h to obtain the martensite heat-resistant steel.
The chemical compositions of the martensitic heat-resistant steel obtained in this example are shown in table 1, the low-magnification test results are shown in table 2, and the inclusion rating results are shown in table 3. The mechanical properties of the large-caliber pipe formed by forging and hot extrusion of the electroslag ingot through the pipe billet are shown in table 4, and the tensile property and the impact property of the large-caliber pipe are far higher than the standard requirements.
Example 4
The embodiment provides a smelting method of novel martensite heat-resistant steel G115, which comprises the following process flows of:
s1, sequentially carrying out smelting on the raw materials in an electric arc furnace of 40 tons, refining in a ladle refining furnace, treating in a VD (vacuum distillation) vacuum furnace and die casting to obtain 3 steel ingots of 13.5 tons;
wherein, during smelting in an electric arc furnace, the raw materials adopt low-carbon low-nickel raw materials such as metal Cr, pure Fe and the like; argon is used for stirring inert gas at the bottom of the electric arc furnace; controlling the content of carbon element not more than 0.04% and the content of phosphorus element not more than 0.003% at the end point; tapping 100% and stopping slag; the oxygen activity of the steel tapping is 1000-1400 ppm; al is adopted for deoxidation, and 0.25 to 0.35 percent of aluminum ingot is added according to the oxygen activity; target temperature: 1660 to 1680 ℃;
when refining in a ladle refining furnace, adding low-carbon lime 0.25-0.75%/batch in batches according to slag conditions, and adding 1-3 batches; siFe powder for deoxidizing slag surface; increasing the stirring force of Ar gas, wherein the Ar gas pressure control is based on the principle that the molten steel does not turn over the slag surface; feeding Al for deoxidation according to the sampling analysis result, wherein the addition amount of the Al is less than or equal to 0.035%; adding Cr, co, copper plate and ferrotungsten at a temperature not lower than 1600 ℃ in batches, wherein the addition amount of each batch is not more than 0.6 ton; adding 0.10-0.18% of ferroboron according to the analysis result before hoisting, and measuring that the content of boron in the molten steel is 0.012-0.020%; the temperature of the crane ladle is 1680-1720 ℃.
When the vacuum is processed in a VD vacuum furnace, the vacuum degree is 66.7Pa, and the holding time is more than or equal to 20min; charging Ar gas to strengthen the stirring, wherein the pressure of the Ar gas is 0.20-0.60 Mpa; hydrogen is determined, H is less than or equal to 1.0ppm; controlling the pressure of Ar gas to be 0.20-0.40 Mpa before the ladle is hung so as not to expose the molten steel in the air; temperature of the crane ladle: 1555 to 1565 ℃.
In the die casting time, a special protective cover is adopted to protect a casting nozzle, and argon is used for protection casting in the casting process, wherein the flow of the argon is 2-5 Nm 3 H; casting by adopting a down-pouring method, and filling Ar into an ingot mold before casting; after finishing injection, the heating agent and the rice ash are added.
S2, carrying out three-time upsetting, drawing and forging on the steel ingot obtained in the step S1 in a 6000-ton quick forging machine to obtain a consumable electrode rod with phi of 500;
wherein the steel ingot heating temperature is 1140-1180 ℃, the heating rate is 50-100 ℃/h, and the heat preservation time is more than or equal to 8 hours; the open forging temperature is 1100 ℃, and the finish forging temperature is 900 ℃; a6000-ton quick forging machine adopts a special patent upsetting device (see Chinese patent CN107552699A, a manufacturing method of a large-scale upsetting device), upsetting is carried out until the height is 1/2 of the original height, and then drawing out to form an octagonal block with the diameter of 800-950 mm; upsetting and drawing out once every fire, and upsetting and drawing out at least three times; forging for more than three times, and carrying out remelting and heating at 1140-1180 ℃ each time, wherein the heat preservation time is more than or equal to 3 hours.
S3, carrying out electroslag remelting on the consumable electrode to obtain an electroslag ingot with a diameter phi of 660;
before electroslag remelting, peeling the consumable electrode until the surface is bright and the natural color of metal is seen; adopting Ar protective atmosphere; adopts quaternary slag system CaF 2 :Al 2 O 3 CaO, mgO =72%, 18%, 5%; the slag amount is 5.0-6.5%; the smelting voltage is 40-55V; the smelting current is 19000 to 22000A; the melting speed is controlled to be 5.0 to 9.5Kg/min; and (5) cooling water is boiled to the maximum, and water cooling is rapidly forced.
And S4, annealing the electroslag ingot at 770 ℃ for 16h to obtain the martensite heat-resistant steel.
The chemical compositions of the martensitic heat-resistant steels obtained in this example are shown in table 1, the low-magnification test results are shown in table 2, and the inclusion rating results are shown in table 3. The mechanical properties of the large-caliber pipe formed by forging and hot extrusion of the electroslag ingot through the pipe billet are shown in table 4, and the tensile property and the impact property of the large-caliber pipe are far higher than the standard requirements.
Table 1 chemical composition of each example, balance iron (wt.%)
TABLE 2 Low power test results for each example
| Generally loose | Center porosity | Ingot type segregation | Point segregation | Other defects visible to the eye | |
| Example 1 | 0.5 | 0 | 0 | 0 | 0 |
| Example 2 | 0.5 | 0 | 0 | 0 | 0 |
| Example 3 | 0.5 | 0 | 0 | 0 | 0 |
| Example 4 | 0.5 | 0 | 0 | 0 | 0 |
TABLE 3 Inclusion rating of each example
TABLE 4 mechanical properties of the examples
Therefore, the invention is not limited to the specific embodiments, but rather, all changes and modifications that can be made without departing from the spirit and scope of the invention are intended to be embraced by the appended claims.
Claims (3)
1. A smelting method of G115 martensite heat-resistant steel is characterized by comprising the following steps:
s1, sequentially carrying out electric arc furnace smelting, ladle refining furnace refining, VD vacuum furnace treatment and die casting on raw materials to obtain a steel ingot;
s2, forging the steel ingot to obtain a consumable electrode;
s3, carrying out electroslag remelting on the consumable electrode to obtain an electroslag ingot;
s4, annealing the electroslag ingot at 750-780 ℃ to obtain the martensite heat-resistant steel;
the raw materials in the step S1 comprise metal Cr, metal Co, metal W, metal Nb, metal Cu and pure Fe,
in the electric arc furnace smelting in the step S1, stirring the electric arc furnace by adopting argon; the content of carbon element is controlled to be not more than 0.04wt% and the content of phosphorus element is controlled to be not more than 0.003wt% at the end point; tapping 100% of slag is blocked; the oxygen activity of the steel tapping is 1000-1400 ppm; al is adopted for deoxidation, and 0.25 to 0.35 percent of aluminum ingot is added; controlling the tapping temperature to be 1660-1680 ℃;
in the refining of the ladle refining furnace in the step S1, low-carbon lime is added in 1 to 3 batches, and the weight percentage of the low-carbon lime is 0.25 to 0.75 percent per batch; deoxidizing the slag surface by using SiFe powder; deoxidizing by adopting Al, and controlling the adding amount of the Al to be less than or equal to 0.035%; adding Cr, co, copper plate and ferrotungsten at a temperature not lower than 1600 ℃ in batches, wherein the addition amount of each batch is not more than 0.6 ton; adding ferroboron 0.10-0.18 wt% before hoisting to reach boron content in molten steel 0.012-0.020 wt%; the temperature of the crane ladle is 1680-1720 ℃;
in the VD vacuum furnace treatment in the step S1, the vacuum degree is 65.0-68.0 Pa, and the holding time is more than or equal to 20min; charging Ar gas and stirring, controlling Ar gas pressure to be 0.20-0.60 Mpa; hydrogen is determined, H is less than or equal to 1.0ppm; controlling the pressure of Ar gas to be 0.20-0.40 Mpa before the ladle is hung so as to avoid the molten steel from being exposed in the air; temperature of the crane ladle: 1555-1565 ℃;
in the die casting in the step S1, a protective cover is adopted to protect a casting nozzle, and argon is used for protecting casting in the casting process, wherein the flow of the argon is 2-5 Nm 3 H; casting by a down-pouring method, and filling Ar into an ingot mold before casting; after finishing injection, adding a heating agent and rice ash; the protective cover is a sealing device which is communicated with argon,
in the forging step S2, the steel ingot heating temperature is 1140-1180 ℃, the heating rate is 50-100 ℃/h, and the heat preservation time is more than or equal to 8 hours; the forging temperature is 1100 ℃, and the finish forging temperature is 900 ℃; upsetting to 1/2 of the original height, and drawing to form an octagonal plate with the diameter of 800-950 mm; upsetting and drawing out once every fire, and upsetting and drawing out at least three times; forging for more than three times, wherein the temperature is 1140-1180 ℃ when the steel is returned to the furnace and the heat preservation time is more than or equal to 3 hours;
in the electroslag remelting in the step S3, before the electroslag remelting, the surface of the consumable electrode is treated; ar gas is adopted as protective atmosphere; adopts quaternary slag system CaF 2 :Al 2 O 3 CaO, mgO =72%, 18%, 5%; controlling the slag amount to be 5.0-6.5 wt%; the smelting voltage is 40-55V; the smelting current is 19000-22000A; the melting speed is controlled to be 5.0 to 9.5Kg/min; the flow rate of the cooling water is controlled to be 180-200 m 3 /h，
The G115 martensite heat-resistant steel smelted according to the method has the condition of ultra-supercritical demonstration engineering application at 630 ℃.
2. The method of smelting a G115 martensitic heat-resistant steel as claimed in claim 1, wherein the exothermic agent is at least one of coke, aluminum, silicon and a silicon-calcium alloy.
3. A method of smelting a martensitic heat-resistant steel as claimed in claim 1, characterized in that said annealing time in step S4 is not less than 1.5min/mm.
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