Method for smelting high-temperature alloy Inconel 625 in consumable vacuum furnace

Abstract

The invention discloses a method for smelting a high-temperature alloy Inconel 625 in a consumable vacuum furnace. In the smelting process, the melting rate of a cast ingot is determined according to a formula (I). According to the method, the stability of the smelting process can be kept, open arc and broken arc can be avoided in the smelting process, so that the stability of the smelting process is kept, and the qualified consumable remelting ingot can be prepared. According to the method, by accurately controlling the melting rate, it is guaranteed that the arc length value is 8-10 mm in the steady-state process, the smelting process can be accurately controlled, the production process is stabilized, the component defects of the head and the tail of the cast ingot can be eliminated, and meanwhile the defects of the dead head of the cast ingot can be avoided.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum furnace smelting, in particular to a method for smelting high-temperature alloy Inconel625 in a vacuum consumable furnace. Background Art

[0002] After the raw materials are smelted in a vacuum induction furnace, the gas contents of [N], [H], and [0] in the ingot are reduced to the lowest, and the internal composition is relatively stable. However, because the raw materials will contact the refractory materials inside the furnace lining during the smelting process, it will cause a certain degree of pollution to the inside of the metal during the smelting process. Therefore, in order to achieve the best internal purity of the metal, it must be remelted for the second time. The methods of secondary remelting include vacuum consumable furnaces, protective atmosphere electroslag furnaces, etc. However, for methods that can significantly improve the internal purity of the metal and reduce the internal gas of the metal, one of the methods with better smelting effect is the vacuum consumable furnace. After the smelting process in the vacuum consumable furnace, due to the slight difference in the uniformity of the internal composition of the ingot and the content of various gases, even with the protection of high vacuum throughout the process, some gases cannot be completely removed and enter the consumable ingot, which in turn has a certain impact on the ingot. At the same time, the instability of parameters such as current and voltage in the initial stage of smelting in the vacuum consumable furnace leads to an increase in the amount of metal elements burned inside the consumable ingot, affecting the uniformity of the composition of the consumable ingot, thereby affecting the quality of the ingot.

[0003] The vacuum consumable furnace mainly relies on the arc length value to control the smelting process during the smelting process, but the control of the arc length value is unstable during the daily smelting process, so that the composition is easily uneven inside the ingot. In addition, the vacuum consumable furnace is easily affected by the pressure and flow rate of the cooling gas (helium) during the smelting process, so it is necessary to control the smelting process. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for smelting high-temperature alloy Inconel625 in a vacuum consumable furnace which can effectively maintain the stability of the smelting process.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: the melting rate of the ingot during the smelting process is carried out according to the following formula (I);

[0006]

[0007] Where: V is the melting rate, kg / min; d is the consumable electrode diameter (which is approximately equal to the ingot diameter when calculated), mm; D is the mold diameter, mm; ρ is the alloy specific gravity, g / cm 3 ; H is the descending height of the consumable electrode, mm / 10min.

[0008] Furthermore, during the smelting process, the vacuum degree of the vacuum consumable furnace is maintained at less than 1 Pa.

[0009] Furthermore, during the smelting process, an arc starting voltage of 20 to 22 V and an arc starting current of 3000 to 4500 A are used for arc starting in the early stage of smelting.

[0010] Furthermore, during the smelting process, the arc length is controlled at 8 to 10 mm.

[0011] The beneficial effect of adopting the above technical solution is that the present invention can maintain the stability of the smelting process, can avoid the occurrence of open arc and broken arc in the smelting process, thereby maintaining the stability of the smelting process, and can prepare qualified consumable remelting ingots. The present invention can accurately control the melting rate to ensure that the arc length value is 8 to 10 mm in the steady state process, and can accurately control the smelting process to achieve a stable production process, eliminate the composition defects at the head and tail of the ingot, and avoid defects at the ingot riser. DETAILED DESCRIPTION

[0012] The present invention is further described in detail below in conjunction with specific implementation modes.

[0013] The method for smelting high temperature alloy Inconel625 in a vacuum consumable furnace adopts the following steps:

[0014] (1) Prepare the ingots required for smelting: The consumable electrode is required to be sawn at the head and tail, the surface of the ingot is polished, and the ingot and the dummy electrode are intermittently welded using welding rods of the same material to ensure that they meet the smelting requirements. After the ingot is polished, the black spots on its surface must be less than 2mm and the depth must be less than 1mm; at the same time, the composition deviation range of each element at the head, tail, and middle of the consumable electrode must be less than 1%.

[0015] The composition of the ingot is (wt): C≤0.01%, Si≤0.1%, Mn≤0.05%, S≤0.002%, P≤0.004%, Ni≥63%, Cr 21.5%-23.0%, Mo 8.80%-9.50%, Al≤0.40%, Nb+Ta3.65%-4.15%, Ti≤0.40%, Fe≤0.25%, Cu≤0.07%, and the balance is Fe and unavoidable impurities.

[0016] (2) Cleaning of key equipment before production and whether various gases can meet production needs: The copper base plate and crystallizer used in the smelting process must be polished clean, and the standard is that there are no impurities and other debris visible to the naked eye on the surface of the equipment; at the same time, the gas pressure, pipeline patency and other indicators must be verified, and the gas pressure and flow rate must be tested to see if they meet the requirements, so as to ensure that the smelting process is normal and reliable.

[0017] In order to fully inspect the operating status of the equipment before production, it is necessary to fully debug the equipment, including various valves, cameras, etc.; at the same time, the vacuum degree in the vacuum consumable furnace chamber must be pumped to below 1 Pa, and the leakage rate must be tested to be no more than 0.05 Pa per hour, which is qualified.

[0018] (3) After the ingot and the dummy electrode are welded, the two together form the consumable electrode ingot used for smelting. At the same time, it is placed in a crystallizer and assembled before smelting. The melting rate of the ingot during the smelting process is carried out according to the following formula (I);

[0019]

[0020] Where: V is the melting rate, kg / min; d is the consumable electrode diameter, which is approximately equal to the ingot diameter in calculation, mm; D is the mold diameter, mm; ρ is the alloy specific gravity, g / cm 3 ; H is the descending height of the consumable electrode, mm / 10min. During the smelting process, the vacuum degree of the vacuum consumable furnace is maintained at less than 1 Pa.

[0021] The smelting process includes arc starting period, steady state period and feeding period. The following are the smelting process parameters of φ300mm and φ450mm crystallizers. Table 1 is the smelting parameters of φ300mm crystallizer, and Table 2 is the smelting parameters of φ450mm crystallizer;

[0022] Table 1: Melting parameters of φ300mm crystallizer

[0023] Voltage / V Current / A Melting rate / kg / min Arc length / mm Smelting time Arcing period 21～22 3000～4500 0 15～20 55～65 Steady state 22～23 4000～5000 2.7～2.8 8～10 120～160 Compensation period 19～20 2000～3000 1.5～2 10～15 70～90

[0024] Table 2: Melting parameters of φ450mm crystallizer

[0025] Voltage / V Current / A Melting rate / kg / min Arc length / mm Smelting time Arcing period 21～23 3000～4500 0 10～20 50～60 Steady state 23～24 5000～6000 4～5.5 8～10 130～170 Compensation period 20～21 2500～3500 2～3 10～15 80～100

[0026] During the smelting process, the consumable ingot is directly placed on the copper bottom plate, and the arc is started between the ingot and the copper bottom plate. During the smelting process, the molten pool is always kept in a shallow and flat state. At the same time, a current power supply mode with a droplet short-circuit control level of 9 to 12 is adopted, and the arc length value is controlled at 8 to 10 mm, which belongs to a short arc operation mode, which is conducive to improving the internal quality of the consumable ingot. The feeding period is carried out by a smelting method with gradually decreasing power.

[0027] (4) After smelting, according to the process requirements, the cooling time of the consumable ingot in the crystallizer must meet the cooling time of φ300 mm ingot for more than 2 hours and the cooling time of φ450 mm ingot for more than 3 hours, and then demolding is carried out.

[0028] Embodiment 1-5:

[0029] (1) The high-temperature alloy Inconel625 electrode was smelted in a vacuum induction furnace. Its diameter was φ220 mm. The electrode shrinkage hole diameter was required to be ≤ 1 / 3 of the electrode diameter. The ingot surface was polished and welded with a dummy electrode. The smelting equipment used was a 1.5-ton vacuum consumable furnace.

[0030] (2) Assemble the crystallizer, the diameter of which is φ300 mm; after a vacuum test, confirm that there is no leakage; install the crystallizer into the work station before smelting, the vacuum degree is <1 Pa, and confirm that the leakage rate during the process is less than 0.05 Pa, which meets the process requirements.

[0031] (3) During the smelting process, observe the arc light in the crystallizer through the detection screen to avoid arc extinguishing, open arc, impurities in the electrode sticking to the crystallizer, etc. The diameter d of the consumable remelting Inconel625 electrode is φ220mm, and the density ρ of Inconel625 is 8.4×10 3 kg / m 3 , the consumable electrode descending height H is 41.28mm / 10min, substituted into formula (Ⅰ):

[0032]

[0033] The melting rate v was calculated to be 2.85 kg / min.

[0034] Through strictly designed current and voltage parameters, and droplet short-circuit control, the level of droplet short-circuit adopted in Examples 1 to 5 is 8 to 12, and other parameters are basically kept in a stable state. The following Table 3 shows various actual parameters in the examples;

[0035] Table 3: Various actual parameters in various embodiments

[0036]

[0037] (4) After the smelting process is completed, the cooling time of the ingot in the crystallizer meets the process requirements, thereby ensuring that the demolding process is safe and reliable.

[0038] (5) The obtained consumable ingots were tested. The content values ​​of the elements at the head and tail of the vacuum consumable ingots tested in each embodiment are shown in Table 4;

[0039] Table 4: Content values ​​of elements detected at the head and tail of vacuum consumable ingots in various embodiments

[0040]

[0041]

[0042] (6) In the smelting process of the above-mentioned implementation cases 1-5, the theoretical value calculated by the melting rate and the actual value displayed by the computer in the actual process are not much different. When the droplet short circuit is controlled at 8 stages, the molten pool depth is likely to be too deep, which leads to defects such as deep shrinkage holes at the riser during the shrinkage compensation process; when the droplet short circuit is controlled at 12 stages, the process fluctuation is likely to be more frequent, the arc length value is large, and the molten pool depth is too deep, which is likely to cause defects such as slag grooves on the surface of the ingot, which also does not meet the smelting requirements; according to the melting rate calculated by this method, when the droplet short circuit is controlled at 9-11 stages, the smelting process is stable. The arc length measurement during the smelting process also verifies that the melting rate is relatively reasonable, can fully meet the requirements of the smelting process, and the ingot quality is good.

Claims

1. A method for smelting high-temperature alloy Inconel625 in a vacuum consumable furnace, characterized in that: The melting rate of the ingot during the smelting process is carried out according to the following formula (I): Where: V is the melting rate, kg / min; d is the consumable electrode diameter, mm; D is the mold diameter, mm; ρ is the alloy specific gravity, g / cm 3 ; H is the descending height of the consumable electrode, mm / 10min.

2. The method for smelting high-temperature alloy Inconel625 in a vacuum consumable furnace according to claim 1, characterized in that: During the smelting process, the vacuum degree of the vacuum consumable furnace is maintained at less than 1 Pa.

3. The method for smelting high-temperature alloy Inconel625 in a vacuum consumable furnace according to claim 1, characterized in that: In the smelting process, an arc starting voltage of 20 to 22 V and an arc starting current of 3000 to 4500 A are used for arc starting in the early stage of smelting.

4. The method for smelting high-temperature alloy Inconel625 by using a vacuum consumable furnace according to claim 1, 2 or 3, characterized in that: During the smelting process, the arc length is controlled at 8 to 10 mm.

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