An electroslag remelting method for controlling the burning loss of Al and Ti elements in high-temperature alloy used in ultra-supercritical thermal power generating units

Abstract

The application discloses an electroslag remelting method for controlling Al and Ti element burning loss of high-temperature alloy for ultra-supercritical thermal power generating unit, which comprises the following steps: S1, preparing an electroslag electrode with uniform composition by vacuum induction melting; S2, electroslag melting, which comprises the following steps: S21, electroslag slag preparation: preparing a certain mass of electroslag slag system with components satisfying CaF2:CaO:MgO:Al2O3:TiO2=(48±5) %:(20±5) %:(5±2) %:(22±5) %:(3±2) %, and adding appropriate mass of aluminum particles into the slag system; the application has the beneficial effects that: the application adopts a suitable five-element electroslag slag system to reduce the reaction between active elements and the slag system; the application adds appropriate aluminum particles into the electroslag slag system, so that the aluminum particles react with impurity components SiO2 and FeO in the slag system during electroslag slag period, the burning loss of Al and Ti elements in the ingot is reduced, and the electroslag ingot with the difference between the head and tail of Al and Ti elements being less than or equal to 0.05% is prepared.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-temperature alloy smelting, and particularly relates to an electroslag remelting method for controlling Al and Ti element burn loss of high-temperature alloy for ultra-supercritical thermal power generating unit. BACKGROUND

[0002] With more stringent requirements on high-temperature strength, oxidation resistance and corrosion resistance of key components of 650℃ grade ultra-supercritical coal-fired power generation technology, material research becomes the most important step in the development of ultra-supercritical power generation technology. Compared with traditional heat-resistant steel, the high-temperature alloy for ultra-supercritical thermal power generating unit takes Fe-Ni as a matrix, adds C (0.03%~0.06%), Al+Ti (3%~6%), Cr (17%~21%), Mo (0.2%~0.6%), W (0.2%~0.8%), Co (1.5%~3.0%), B (0.002%~0.008%), and has more excellent performance indexes. Among them, Al and Ti elements can form a strengthening phase with Ni, and have the greatest impact on the alloy. However, in the initial stage of electroslag remelting, the active elements Al and Ti react with unstable oxides in the slag, causing Al and Ti element burn loss at the arc starting end of the electroslag ingot, and leading to performance non-uniformity at the arc starting end and the feeding end of the ingot. Therefore, in order to promote the application of high-temperature alloy for ultra-supercritical thermal power generating unit, a reasonable electroslag remelting method needs to be developed to reduce the burn loss of Al and Ti elements in the ingot.

[0003] The application is mainly used for electroslag remelting of high-temperature alloy for ultra-supercritical thermal power generating unit. In order to ensure uniformity of Al and Ti element composition at the head and tail of the Φ406mm specification ingot used in the application, the main innovations include: (1) using a suitable five-element electroslag system to reduce the reaction of active elements with the slag system; (2) adding a proper amount of aluminum particles to the electroslag system, so that they react with impurity components SiO2 and FeO in the slag system during electroslag remelting, and reduce the burn loss of Al and Ti elements in the ingot. SUMMARY

[0004] The application aims to provide an electroslag remelting method for controlling Al and Ti element burn loss of high-temperature alloy for ultra-supercritical thermal power generating unit, to solve the problems raised in the background technology.

[0005] To achieve the above-mentioned purpose, the application provides the following technical solutions:

[0006] An electroslag remelting method for controlling Al and Ti element burn loss of high-temperature alloy for ultra-supercritical thermal power generating unit, comprising the following steps:

[0007] S1, preparing an electroslag electrode with uniform composition by vacuum induction melting;

[0008] S2, electroslag melting, comprising the following steps:

[0009] S21, preparing slag for electroslag: prepare a certain mass of components to meet the CaF2: CaO: MgO: Al2O3: TiO2= (48±5) %: (20±5) %: (5±2) %: (22±5) %: (3±2) % of the electroslag slag system, and add aluminum particles of a suitable mass to the slag system;

[0010] S22, slag melting stage: initially add a certain amount of slag, and supplement the slag after melting. The power and slag resistance control is used in the slag melting stage to quickly form a liquid slag pool.

[0011] S23, stable melting stage: argon is introduced into the furnace for atmosphere protection in the stable melting stage. The melting rate and slag swing control is used to ensure the stability of the melting.

[0012] S24, hot sealing top stage: power control is used to set the start weight and end weight of the shrinkage, and to reduce the shrinkage hole depth of the electroslag ingot head.

[0013] S25, after the electroslag ingot is melted, it is cooled for a period of time and then taken out of the furnace.

[0014] As preferred, the nominal diameter of the electroslag electrode in step S1 is Ф350 mm, the electrode composition is C (0.03%~0.06%), Al+Ti (3%~6%), Cr (17%~21%), Mo (0.2%~0.6%), W (0.2%~0.8%), Co (1.5%~3.0%), B (0.002%~0.008%), Fe (22%~30%), and the balance is Ni.

[0015] As preferred, the surface of the electroslag electrode in step S1 is polished and dried. The polishing requirement is that the size of the oxide skin on the electrode surface is ≤5 mm, the drying temperature is (100~200) ℃, and the drying time is (4~8) h.

[0016] As preferred, the mass of the electroslag slag system in step S21 is (60~120) kg, the impurity components SiO2 and FeO in the electroslag slag system are ≤0.6% and ≤0.2% respectively, the mass of the aluminum particles is related to the mass of the electroslag slag system, the content of SiO2 and FeO in the electroslag slag system, m (aluminum particles) = (0.5~0.7) * m (mass of the electroslag slag system) * w (SiO2) + (0.2~0.3) * m (mass of the electroslag slag system) * w (FeO), and the particle size of the aluminum particles is ≤5 mm.

[0017] As preferred, a nominal diameter of Ф450 mm of the electroslag crystallizer is selected in step S22, the initial amount of the slag added in the slag melting stage is (20~50) %, and the slag is supplemented within (2~15) min of melting.

[0018] As preferred, the stable melting stage in the step S23 has a melting speed range of (150-300) kg / h and a slag swing range of (0.10-0.90) mohm.

[0019] As preferred, the hot top sealing stage in the step S24 has a feeding start weight of (100-150) kg and a feeding end weight of (20-50) kg.

[0020] As preferred, the post-melting cooling time in the step S25 is (60-150) min.

[0021] As preferred, the Al and Ti element head-to-tail difference of the electroslag ingot is ≤0.05%.

[0022] Compared with the prior art, the present application has the beneficial effects that: the present application adopts a suitable five-element electroslag system, reduces the reaction of active elements with the slag system; the present application adds a proper amount of aluminum particles to the electroslag system, so that the aluminum particles react with the impurity components SiO2 and FeO in the slag system during the electroslag melting period, reduces the burning loss of Al and Ti elements in the ingot, and prepares an electroslag ingot with an Al and Ti element head-to-tail difference of ≤0.05%. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application is an electroslag ingot for supercritical thermal power generating units. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0025] Please refer to Figure 1 The present application provides a technical solution:

[0026] An electroslag remelting method for controlling the burning loss of Al and Ti elements of a high-temperature alloy for supercritical thermal power generating units, comprising the following steps:

[0027] S1, preparing an electroslag electrode with uniform composition by vacuum induction melting;

[0028] S2, electroslag melting, comprising the following steps:

[0029] S21, the slag preparation of electroslag: prepare a certain mass of components to meet the CaF2: CaO: MgO: Al2O3: TiO2= (48±5) %: (20±5) %: (5±2) %: (22±5) %: (3±2) % of the electroslag slag system, and add aluminum particles of a suitable mass to the slag system;

[0030] S22, the slag melting stage: add a certain proportion of slag at the beginning, and supplement the slag after melting, and the power and slag resistance control is used in the slag melting stage to quickly form a liquid slag pool;

[0031] S23, the stable melting stage: argon is introduced into the furnace for atmosphere protection in the stable melting stage, the melting speed and slag swing control are used to ensure the stability of melting;

[0032] S24, the hot sealing top stage: the power control is used, the start weight and the end weight of the shrinkage are set, and the shrinkage hole depth of the electroslag ingot head is reduced;

[0033] S25, the electroslag ingot is taken out of the furnace after being melted and cooled for a period of time.

[0034] Further, in step S1, the nominal diameter of the electroslag electrode is Ф350mm, the electrode composition is C (0.03%~0.06%), Al+Ti (3%~6%), Cr (17%~21%), Mo (0.2%~0.6%), W (0.2%~0.8%), Co (1.5%~3.0%), B (0.002%~0.008%), Fe (22%~30%), and the balance is Ni.

[0035] Further, in step S1, the surface of the electroslag electrode is polished and dried, the polishing requirement is that the size of the oxide skin on the electrode surface is ≤5mm, the drying temperature is (100~200)℃, and the drying time is (4~8)h.

[0036] Further, in step S21, the mass of the electroslag slag system is (60~120)kg, the impurity components SiO2 and FeO in the electroslag slag system are ≤0.6% and ≤0.2% respectively; the mass of the aluminum particles is related to the mass of the electroslag slag system, the content of SiO2 and FeO in the electroslag slag system, m (aluminum particles) = (0.5~0.7) * m (mass of the electroslag slag system) * w (SiO2) + (0.2~0.3) * m (mass of the electroslag slag system) * w (FeO), and the particle size of the aluminum particles is ≤5mm.

[0037] Further, in step S22, an electroslag crystallizer with a nominal diameter of Ф450mm is selected, the initial amount of slag added in the slag melting stage is (20~50)%, and the slag is supplemented within (2~15)min of melting.

[0038] Further, the stable melting stage in step S23 has a melting rate range of (150-300) kg / h and a slag swing range of (0.10-0.90) mohm.

[0039] Further, the hot sealing top stage in step S24 has a feeding start weight of (100-150) kg and a feeding end weight of (20-50) kg.

[0040] Further, the post-melting cooling time in step S25 is (60-150) min.

[0041] Further, the electric-shielded ingot Al and Ti element head-to-tail difference is ≤0.05%.

[0042] Embodiment

[0043] S1, according to the composition requirements of high-temperature alloy for ultra-supercritical thermal power generating unit, C: 0.04%, Al: 2.1%, Ti: 2.2%, Cr: 17.5, Mo: 0.3%, W: 0.5%, Co: 2%, B: 0.003%, Fe: 25%, and the balance of Ni, 3000 kg of raw materials are weighed. A vacuum induction furnace is used to prepare an electric-shielded electrode with a nominal diameter of Φ350 mm through melting, refining and pouring. The electric-shielded electrode is removed from the oxide skin to the smooth surface of the electrode by using an automatic grinding machine. The ground electric-shielded electrode is placed in a drying box and dried at a temperature of 150°C for 5h.

[0044] S2, electric-shielded melting, including the following steps:

[0045] S21, electric-shielded slag preparation: 50 kg of electric-shielded slag with components of CaF2: CaO: MgO: Al2O3: TiO2=48%:20%:5%:22%:3% is prepared, and 0.3 kg of aluminum particles with a particle size of ≤5 mm is added to the slag system.

[0046] S22, slag melting stage: a nominal diameter of Φ406 mm of electric-shielded crystallizer is selected, 20% of the slag amount is initially added, and after 2 min of melting, the slag is added, the power and slag resistance control is used in the slag melting stage to quickly form a liquid slag pool.

[0047] S23, stable melting stage: the stable melting stage has a melting rate range of 200 kg / h and a slag swing of 0.6 mohm, argon gas is introduced into the furnace for atmosphere protection to ensure the stability of the melting.

[0048] S24, hot top sealing stage: the hot top sealing stage time is set to 5 min→10 min→15 min→20 min→25 min→30 min, the power is set to 85%→72%→63%→55%→46%→35%, the weight of the feeding is 110 kg, and the weight of the feeding end is 40 kg, so as to reduce the shrinkage cavity depth of the head of the electroslag ingot.

[0049] S25, after cooling for 90 min, the electroslag ingot is discharged, and the preparation of the electroslag ingot with a nominal diameter of Φ406 mm is completed; the composition of the sample taken from the head and tail of the electroslag ingot is detected, and the result is shown in Table 1.

[0050] Table 1 Composition of the electroslag ingot for an ultra-supercritical thermal power unit

[0051]

[0052] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. An electroslag remelting method for controlling the loss of Al and Ti elements of a high-temperature alloy used in an ultra-supercritical thermal power unit, characterized by, It comprises the following steps: S1, preparing an electric-shaft electrode with uniform components by vacuum induction smelting; S2, electric-shaft smelting, comprising the following steps: S21, electric-shaft slag preparation: preparing a certain mass of electric-shaft slag system with components satisfying CaF2:CaO:MgO:Al2O3:TiO2=(48±5)%:(20±5)%:(5±2)%:(22±5)%:(3±2)%, and adding aluminum particles with a proper mass into the slag system; S22, slag melting stage: adding a certain proportion of slag initially, and adding slag after smelting, and adopting power and slag resistance control to quickly form a liquid slag pool in the slag melting stage; S23, stable smelting stage: blowing argon into the furnace to protect the atmosphere in the stable smelting stage, and adopting melting speed and slag swing control to ensure the stability of smelting; S24, hot sealing top stage: adopting power control, setting the starting weight and the end weight of feeding, and reducing the shrinkage hole depth of the head of the electric-shaft ingot; S25, taking out the furnace after the electric-shaft ingot is smelted and cooled for a period of time; In step S1, the nominal diameter of the electric-shaft electrode is Ф350mm, and the components of the electrode are C 0.03%-0.06%, Al+Ti 3%-6%, Cr 17%-21%, Mo 0.2%-0.6%, W 0.2%-0.8%, Co 1.5%-3.0%, B 0.002%-0.008%, Fe 22%-30%, and the balance is Ni; In step S1, the surface of the electric-shaft electrode is polished and dried, the polishing requirement is that the size of the oxide skin on the electrode surface is ≤5mm, the drying temperature is 100-200°C, and the drying time is 4-8h; In step S21, the mass of the electric-shaft slag system is 60-120kg, the impurity components SiO2 and FeO in the electric-shaft slag system are ≤0.6% and ≤0.2% respectively, the mass of the aluminum particles is related to the mass of the electric-shaft slag system and the content of the impurity components SiO2 and FeO in the electric-shaft slag system, the mass of the aluminum particles m=(0.5-0.7)*mass of the electric-shaft slag system*w(SiO2)+(0.2-0.3)*mass of the electric-shaft slag system*w(FeO), wherein w is the mass content of SiO2 / FeO in the slag system, and the particle size of the aluminum particles is ≤5mm; In step S22, a electric-shaft crystallizer with a nominal diameter of Ф450mm is selected, and the initial amount of slag added in the slag melting stage is (20-50)%, and the slag is added in (2-15)min; In step S23, in the stable smelting stage, the melting speed ranges from 150 to 300kg / h, and the slag swing ranges from 0.10 to 0.90mohm.

2. The method according to claim 1, wherein the method is characterized in that, In step S24, in the hot sealing top stage, the starting weight of feeding is 100-150kg, and the end weight of feeding is 20-50kg.

3. The method according to claim 1, wherein the method is characterized by, In step S25, the cooling time after smelting is (60-150)min.

4. The method according to claim 1, wherein the method is characterized in that, In the electric-shaft ingot, the head-to-tail difference of Al and Ti elements is ≤0.05%.

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