CN106636702A - Preparation method for low oxygen content and high alloying nickel-based mother alloy and powder - Google Patents

Abstract

The invention discloses a method for preparing nickel-based master alloy and powder with low oxygen content and high alloying, which belongs to the field of powder metallurgy. The process flow is as follows: firstly, a pure master alloy ingot is prepared by a dual process of vacuum smelting and electroslag remelting. In the process of vacuum smelting, calcium oxide crucible is used, and the master alloy ingot with the designed composition is obtained by pretreating the raw materials, adding carbon blocks for deoxidation during the refining period, and supplementing easily burnt elements at the end of smelting. In the process of electroslag smelting, the conditions for non-metallic inclusions to float up are created by adjusting parameters such as the shape, depth, and viscosity of the slag pool, so that the master alloy is further purified. After peeling the master alloy ingot after electroslag remelting, the master alloy ingot is subjected to high-speed disk grinding and crushing under a protective atmosphere to obtain superfine master alloy powder. The K418 master alloy powder prepared by this method has a particle size of less than 20 μm, an oxygen content of less than 200 ppm, and a sulfur content of less than 20 ppm. After being mixed with carbonyl nickel powder, it can be sintered and densified at a lower temperature, greatly reducing the powder superalloy. Production costs and process energy consumption.

Description

A kind of preparation method of low oxygen content high alloyed nickel-based master alloy and powder

technical field

The invention belongs to the field of powder metallurgy and provides a method for preparing a nickel-based master alloy with low oxygen content and high alloying and powder.

Background technique

The master alloy method is to prepare the alloy elements in the material into highly alloyed fine master alloy powder, then mix the master alloy powder and matrix element powder in a corresponding proportion, and then sinter to form an alloy with uniform composition. This method improves the driving potential of atom migration during sintering by increasing the specific surface area and lattice distortion of the powder, and increasing the chemical composition gradient between the powders. By rationally designing the composition of the master alloy to control the temperature and quantity of the liquid phase during the sintering process, the resistance to particle rearrangement can be further reduced, the sintering activity can be improved, and the sintering temperature can be reduced. This provides a new way to manufacture nickel-based powder superalloys at low cost.

Obtaining high-alloyed nickel-based master alloy powders with low oxygen content is a prerequisite for the preparation of high-performance nickel-based powder superalloys. The content of active elements Cr, Al, Ti and Zr in high alloyed nickel base alloy master alloy is much higher than that of ordinary nickel base superalloy. During the sintering process, impurity oxygen will migrate to the surface and grain boundary of the master alloy powder particles, forming more serious oxide inclusions and greatly reducing the comprehensive mechanical properties of the material. Therefore, the oxygen content of the master alloy powder has an important impact on the product performance . The invention adopts a dual process of vacuum induction smelting and inert atmosphere electroslag smelting to prepare high-alloyed nickel-based alloy master alloy. Vacuum induction melting can effectively control the chemical composition of the alloy and prevent the contact of the highly alloyed nickel-based alloy melt with hydrogen, oxygen and nitrogen in the atmosphere, but the vacuum induction ingot is easily polluted by the refractory crucible and introduces ceramic inclusions. In the process of electroslag remelting, the slag system suitable for nickel-based master alloy remelting is designed, so that the molten alloy droplets pass through the high-temperature and high-activity slag layer drop by drop, providing very good thermodynamics and power for the floating of inclusions It is one of the most effective refining processes to remove non-metallic inclusions and high-efficiency desulfurization in alloys. It can effectively reduce the content of sulfur, remove large-sized foreign inclusions, make the endogenous inclusions diffuse and refine the distribution, and reduce the active elements Al, Burning loss of Ti etc. Under the protection of an inert atmosphere, the desulfurization conditions were improved by continuously adding an equal amount of calcium oxide. In the crushing process of the master alloy ingot, the particle size of the powder is controlled by controlling the crushing atmosphere and the crushing intensity to reduce the oxygen increase in the crushing process. According to the calculation of the phase diagram, the temperature of the liquid phase of the designed master alloy composition is the lowest in the alloy system, which greatly reduces the temperature required for the sintering of the alloy powder.

Contents of the invention

The purpose of the present invention is to provide a low oxygen content high-alloyed high-temperature alloy master alloy and a preparation process of powder. Prepare the master alloy ingot by vacuum induction melting + electroslag remelting process, reduce the oxygen content, sulfur content and the number of inclusions in the master alloy ingot, improve the ingot crushing equipment, and reduce the increased oxygen content in the crushing process.

The specific process steps are:

1. Raw material pretreatment: use Ni-50wt.%Cr master alloy, Ni-5wt.%B master alloy, Ni-Mo master alloy, Ni-Nb master alloy, aluminum block, sponge titanium, sponge zirconium and graphite block as Raw materials for smelting have a purity greater than 99.9wt.%. The metal raw materials are pretreated in 5vol.% hydrochloric acid aqueous solution to remove surface oxides. The pretreatment time is 25-35 minutes, then rinsed in alcohol, and treated in an oven at 60°C for 30-90 minutes to dry the raw materials.

2. Vacuum induction melting of master alloy ingots: the pretreated raw materials are compounded according to the composition of the high-alloyed master alloy to obtain mixed raw materials. The mixed raw materials are subjected to vacuum induction melting. The composition of the high alloying master alloy is Ni-9.15Al-19.23Cr-6.62Mo-3.31Nb-1.15Ti-0.15Zr-0.02B-0.18C (weight percentage). The master alloy is smelted in a vacuum induction melting furnace. During the smelting process, a calcium oxide crucible is used, and the power is increased after the furnace charge is melted, so that the temperature of the molten pool rises to 1670°C, and then 2wt.% carbon block is added and kept for 25- 35min. During this process, an electromagnetic stirrer was used to stir the molten pool to fully remove oxygen. Then, 1wt.% Al and Ti and 0.01wt.% B were added and kept for 10min. After that, the temperature was lowered and filled with argon, and the The molten steel is poured into a master alloy ingot.

3. Electroslag remelting of parent alloy ingots: electroslag melting in an inert atmosphere for vacuum induction smelted ingots, the ratio of slag to material is 15-20wt.% CaO, 3-5wt.% Ca, 8-10wt.% CeO, 10-15 wt.% Al ₂ O ₃ , 3-5 wt.% TiO ₂ , the balance CaF ₂ . After the above slag is heated to a molten state, it is poured into a crystallizer, which is a water-cooled copper crucible, and the master alloy consumable electrode rod prepared in step 2 is slowly lowered into the molten slag, and after energization and arcing , adjust the remelting voltage to 30-50V, current 3000-5000A, the self-consumable electrode is slowly melted by resistance heat, the molten steel reacts with the slag, and after purification, crystallizes at the bottom of the crystallizer to obtain a pure, uniform, surface Clean master alloy electroslag ingot.

4. Crushing of master alloy ingots: Remove the oxide skin on the surface of master alloy ingots, and crush them in a high-speed disc mill crushing device with a cooling system and a protective atmosphere. The ratio of the inner diameter of the grinding ring to the diameter of the grinding block is 5 :1. The disc grinding device is shown in Figure 2. The crushed powder is screened to obtain master alloy powder with an average particle size of ≤20 μm.

In the present invention, highly active alloying elements (such as Cr, Ti, Al, Nb, Zr, B, and C) are prepared into a master alloy in advance, and then added to the material in the form of the master alloy instead of the form of individual elements, which is not affected by the alloy Restrictions such as the easy oxidation of elements can effectively avoid the oxidation of active elements and help reduce the oxygen content. The pretreatment of raw materials can effectively reduce the oxidation and impurities generated in the process of raw material procurement and storage, and ensure the high purity of raw materials during smelting. Using Ni-50Cr master alloy, Ni-5B master alloy, Ni-Mo master alloy and Ni-Nb master alloy as smelting raw materials can further reduce the temperature required for alloying, thereby reducing burning loss and oxidation, and ensuring the recovery of alloy elements Yield. At the same time, use the good stability and desulfurization and deoxidation properties of the calcium oxide crucible in the vacuum induction melting process to reduce the oxygen content in the melting process, and further deoxidize through the addition of carbon blocks in the later stage of smelting, and add elements that are easy to burn out before the furnace, ensuring that the mother The alloy content of the alloy is within the required range. Electroslag remelting with inert gas protection is performed on the ingot obtained by vacuum induction melting to further reduce the oxygen and sulfur content in the ingot, reduce inclusions, and purify the ingot. The master alloy ingot has low plasticity and is easy to break, so it is convenient to obtain fine alloy powder. The self-designed high-speed disc grinding device can effectively prevent powder oxidation during the crushing process, and is convenient to obtain master alloy powder with low oxygen content, and finally obtain master alloy powder with oxygen content less than 200ppm and sulfur content less than 20ppm, and its average particle size is below 20μm . Using this master alloy powder to prepare K418 alloy can make the sintering process proceed under the condition of a small amount of liquid phase, which helps to solve the problem of sintering deformation of the product, can improve the dimensional accuracy of the sample, and can significantly reduce the cost of raw material powder and process energy consumption .

During the process, the changes in the impurity content of the master alloy are shown in Table 1.

Table 1 Low oxygen content high alloyed nickel-based master alloy and the impurity content of the master alloy in each process step of the powder

Description of drawings

Figure 1 is a process flow diagram

Figure 2 is a schematic diagram of a high-speed disc mill crushing device.

detailed description

Example 1:

The Ni-50wt.%Cr master alloy, Ni-5wt.%B master alloy, Ni-Mo master alloy, Ni-Nb master alloy with a purity greater than 99.9wt.%, as well as aluminum blocks, sponge titanium, and sponge zirconium, in 5vol .% hydrochloric acid aqueous solution for pretreatment to remove surface oxides. The pretreatment time is 30min. After washing with alcohol, it is dried in an oven at 60°C for 60min. %Ni-9.15wt.%Al-19.23wt.%Cr-6.62wt.%Mo-3.31wt.%Nb-1.15wt.%Ti-0.15wt.%Zr-0.02wt.%B-0.18wt.%C. The raw materials were smelted in a vacuum induction melting furnace. During the smelting process, a ceramic crucible was used, and the power was increased after the furnace material was melted, so that the temperature of the molten pool rose to 1670°C, and then 2wt.% carbon block was added and kept for 30 minutes. During the process, use an electromagnetic stirrer to stir the molten pool to fully remove oxygen, then add 1wt.% Al and Ti and 0.01wt.% B, keep warm for 10 minutes, then cool down, fill with argon, and pour the molten steel Master alloy consumable electrode rod. _The consumable electrode rod is subjected to electroslag smelting under the protection _of an inert _atmosphere . amount of CaF ₂ . After the above slag is heated to a molten state, it is poured into a crystallizer. The consumable electrode rod slowly descends into the molten slag. After the arc is energized, adjust the remelting voltage to 50V and the current 3000A. The consumable electrode is slowly melted by resistance heat, and the molten steel reacts with the slag to purify. Finally, crystallize at the bottom of the crystallizer to obtain a pure, uniform, and smooth surface master alloy electroslag ingot. Afterwards, the skin of the electroslag ingot is removed, and crushed in a high-speed disc mill crushing device with a cooling system and a protective atmosphere. The crushed powder is screened to finally obtain the master alloy powder.

Example 2:

The Ni-50wt.% Cr master alloy, Ni-5wt.% B master alloy, Ni-Mo master alloy, Ni-Nb master alloy with a purity greater than 99.9wt.%, as well as aluminum blocks, sponge titanium, and sponge zirconium, in 5wt .% hydrochloric acid aqueous solution for pretreatment to remove surface oxides. The pretreatment time is 30min. After washing with alcohol, it is dried in an oven at 60°C for 60min. %Ni-9.15wt.%Al-19.23wt.%Cr-6.62wt.%Mo-3.31wt.%Nb-1.15wt.%Ti-0.15wt.%Zr-0.02wt.%B-0.18wt.%C. The raw materials were smelted in a vacuum induction melting furnace. During the smelting process, a ceramic crucible was used, and the power was increased after the furnace material was melted, so that the temperature of the molten pool rose to 1670°C, and then 2wt.% carbon block was added and kept for 30 minutes. During the process, use an electromagnetic stirrer to stir the molten pool to fully remove oxygen, then add 1wt.% Al and Ti and 0.01wt.% B, keep warm for 10 minutes, then cool down, fill with argon, and pour the molten steel Master alloy consumable electrode rod. _The consumable electrode rod is subjected to electroslag smelting under the protection _of an inert _atmosphere . amount of CaF ₂ . After the above slag is heated to a molten state, it is poured into a crystallizer. The consumable electrode rod slowly descends into the molten slag. After the arc is energized, adjust the remelting voltage to 30V and the current 5000A. The consumable electrode is slowly melted by resistance heat, and the molten steel reacts with the slag to purify. Finally, crystallize at the bottom of the crystallizer to obtain a pure, uniform and smooth surface master alloy electroslag ingot. Afterwards, the skin of the electroslag ingot is removed, and crushed in a high-speed disc mill crushing device with a cooling system and a protective atmosphere. The crushed powder is screened to finally obtain the master alloy powder.

Example 3:

The Ni-50wt.% Cr master alloy, Ni-5wt.% B master alloy, Ni-Mo master alloy, Ni-Nb master alloy with a purity greater than 99.9wt.%, as well as aluminum blocks, sponge titanium, and sponge zirconium, in 5wt .% hydrochloric acid aqueous solution for pretreatment to remove surface oxides. The pretreatment time is 30min. After washing with alcohol, it is dried in an oven at 60°C for 60min. %Ni-9.15wt.%Al-19.23wt.%Cr-6.62wt.%Mo-3.31wt.%Nb-1.15wt.%Ti-0.15wt.%Zr-0.02wt.%B-0.18wt.%C. The raw materials were smelted in a vacuum induction melting furnace. During the smelting process, a ceramic crucible was used, and the power was increased after the furnace material was melted, so that the temperature of the molten pool rose to 1670°C, and then 2wt.% carbon block was added and kept for 30 minutes. During the process, use an electromagnetic stirrer to stir the molten pool to fully remove oxygen, then add 1wt.% Al and Ti and 0.01wt.% B, keep warm for 10 minutes, then cool down, fill with argon, and pour the molten steel Master alloy consumable electrode rod. _The consumable electrode rod is subjected to electroslag smelting under the protection _of an inert _atmosphere . amount of CaF ₂ . After the above slag is heated to a molten state, it is poured into a crystallizer. The consumable electrode rod slowly descends into the molten slag. After the arc is energized, adjust the remelting voltage to 45V and the current 3500A. The consumable electrode is slowly melted by resistance heat, and the molten steel reacts with the slag to purify. Finally, crystallize at the bottom of the crystallizer to obtain a pure, uniform, and smooth surface master alloy electroslag ingot. Afterwards, the skin of the electroslag ingot is removed, and crushed in a high-speed disc mill crushing device with a cooling system and a protective atmosphere. The crushed powder is screened to finally obtain the master alloy powder.

Claims (5)

1. the preparation method of a kind of Ni-based foundry alloy of low oxygen content high-alloying and powder, it is characterised in that：

Step one, with Ni-50wt.%Cr intermediate alloys, Ni-5wt.%B intermediate alloys, Ni-Mo intermediate alloys, Ni-Nb in the middle of Alloy, and aluminium block, titanium sponge, sponge zirconium, graphite block, used as raw material, the purity of various raw materials is all higher than 99.9%；Metal raw Material is pre-processed in 5vol.% aqueous hydrochloric acid solutions, removes oxide on surface, and pretreatment time is 25-35min, and alcohol is washed Process at 60 DEG C in an oven after net and dry 30-90min；

Step 2, pretreated raw material carry out dispensing according to the composition of high-alloying foundry alloy, obtain mixed material.Mixing is former Material carries out vacuum induction melting；Ceramic crucible is adopted in fusion process, and it is after furnace charge is melting down plus high-power, make on bath temperature 1670 DEG C are risen to, 2wt.% carbon blocks are added, 25-35min is incubated, magnetic stirrer is stirred molten bath used in fusion process Mix, oxygen is fully removed, be added followed by the Al and Ti and 0.01wt.%B of 1wt.%, be incubated 8-12min, cooling afterwards, Argon gas is filled with, molten steel is poured and is built up foundry alloy consutrode rod；

Step 3, slag charge is heated to after molten condition, in pouring crystallizer into, crystallizer is copper cold-crucible, by step 2 The foundry alloy consutrode rod for preparing is slowly drop down in the slag charge for melting, after the energization starting the arc, adjustment remelting voltage to 30- 50V, electric current 3000-5000A, consutrode is delayed fusing by resistance heat, after the molten steel after fusing and slag charge reaction, purification, is being tied Brilliant device bottom crystal, obtains pure, uniform, any surface finish foundry alloy ESR ingot；Jing after vacuum electroslag remelting, foundry alloy oxygen contains Amount is less than 150ppm, and sulfur content is less than 20ppm；

Step 4, mother alloy ingot surface scale is removed, broken with the worn-off of cooling system and the high-speed disc of protective atmosphere Crushed in device；Powder after to crushing is screened, and obtains master alloy powder.

2. the preparation method of a kind of Ni-based foundry alloy of low oxygen content high-alloying according to claim 1 and powder, it is special Levy and be：The composition of described high-alloying foundry alloy is：Ni-9.15wt.%Al-19.23wt.%Cr-6.62wt.%Mo- 3.31wt.%Nb-1.15wt.%Ti-0.15wt.%Zr-0.02wt.%B-0.18wt.%C；The liquid of nickel-base alloy foundry alloy It is 1135 DEG C mutually to form temperature.

3. the preparation method of a kind of Ni-based foundry alloy of low oxygen content high-alloying according to claim 1 and powder, it is special Levy and be：Slag charge proportioning described in step 3 is 15-20wt.%CaO, 3-5wt.%Ca, 8-10wt.%CeO, 10-15wt.% Al₂O₃, 3-5wt.%TiO₂, surplus CaF₂。

4. the preparation method of a kind of Ni-based foundry alloy of low oxygen content high-alloying according to claim 1 and powder, it is special Levy and be：Mill device described in step 4 is cooled down using cooling water, is protected using high-purity argon gas, grinding ring internal diameter It is 5 with the ratio of grinding block diameter:1.

5. the preparation method of a kind of Ni-based foundry alloy of low oxygen content high-alloying according to claim 1 and powder, it is special Levy and be：The final oxygen content of the master alloy powder described in step 4 is less than 200ppm, and sulfur content is less than 20ppm, is mingled with material Amount is less than 0.002wt.%, average grain diameter≤20 μm of powder particle.