CN114990344B

CN114990344B - Method for producing high Al alloy by adopting vacuum consumable smelting

Info

Publication number: CN114990344B
Application number: CN202210641835.XA
Authority: CN
Inventors: ***; 王立; 高首磊; 周立新; 谢伟; 曹政; 李林森
Original assignee: Daye Special Steel Co Ltd
Current assignee: Daye Special Steel Co Ltd
Priority date: 2022-06-07
Filing date: 2022-06-07
Publication date: 2023-11-24
Anticipated expiration: 2042-06-07
Also published as: CN114990344A

Abstract

The invention belongs to the field of special alloy smelting, and particularly relates to a method for producing high Al alloy by adopting vacuum consumable smelting. The method sequentially comprises the following steps: preparing a high Al alloy electrode, welding the electrode, consumable remelting, high-temperature diffusion and forging. According to the invention, the beta-phase morphology and the beta-phase size of the high AL alloy are controlled by controlling the smelting speed of the consumable process and introducing helium gas for cooling in the gap between the steel ingot and the crystallizer, so that the aim of improving the uniformity of the product structure is finally achieved. The GH6783 alloy bar produced by the invention has uniform beta-phase structure after being formed, and meets the use requirement.

Description

Method for producing high Al alloy by adopting vacuum consumable smelting

Technical Field

The invention belongs to the field of special alloy smelting, and particularly relates to a method for producing high Al alloy by adopting vacuum consumable smelting.

Background

The solid solubility of Al in the high-temperature alloy is very small and is less than 0.25wt percent, and meanwhile, the melting point of the Al element is very low, so that for the alloy with high Al content, large-area low-melting-point dendrite segregation is very easy to generate in the smelting process, and the uniformity of a precipitated phase of a finished product is influenced when the segregation is serious, and the performance of the finished product is finally influenced.

The GH6783 alloy is an iron-cobalt-nickel based oxidation-resistant low-expansion high-temperature alloy taking niobium, chromium and aluminum as main strengthening elements, contains 5.0% -6.0% of Al, and is a deformation high-temperature alloy with the highest Al content known at present. Because of the existence of a large amount of Al elements in the alloy, a large amount of interdendritic phases and coarse beta phases are generated in the smelting process, so that great difficulty is brought to subsequent production and structural uniformity improvement, and particularly segregation is more serious as the ingot shape is increased. The GH6783 alloy cast ingot produced in the prior art has coarse beta phase precipitation, is difficult to eliminate in the subsequent homogenizing diffusion and forging process, and generally takes longer homogenizing diffusion.

Disclosure of Invention

In the prior art, large-area low-melting-point dendrite segregation and the like in the smelting process of large-ingot high-Al alloy due to high Al content are solved. In view of the above technical drawbacks, it is an object of the present invention to provide a method for producing a high Al alloy by vacuum consumable melting, and it is a second object of the present invention to provide a high Al alloy produced by the method.

In a first aspect, the invention provides a method for producing a high Al alloy by vacuum consumable smelting, comprising the following steps in order: preparing a high Al alloy electrode, welding the electrode, consumable remelting, high-temperature diffusion and forging.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the high Al alloy is GH6783 alloy.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the high Al alloy electrode is produced by a vacuum induction furnace melting process.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the vacuum induction furnace melting process includes the steps of: preparing materials, evacuating, charging, powering, charging, fully melting, stirring, standing, adjusting components and pouring;

preferably, the evacuating step ensures that the vacuum level value is not greater than 30Pa;

preferably, the charging is performed twice by charging the raw materials into the furnace in the sequence of pure metal before intermediate alloy;

preferably, the vacuum degree of the vacuum induction furnace in the refining period is controlled to be 1 Pa-5 Pa, the refining period is more than 90min, and the refining temperature is controlled to be 1500 ℃ to 1550 ℃;

preferably, the feeding is performed in the order of aluminum, titanium and niobium after the refining period is finished;

preferably, the analysis of the gas content in the furnace is performed before the addition of aluminum, ensuring that the oxygen content is less than 15X 10 ^-6 Nitrogen content of less than 20 x 10 ^-6 The temperature in the aluminum adding forehearth is reduced to 1480-1500 ℃, aluminum is added in two batches averagely according to the adding amount, stirring is carried out for 5-10 min after each adding, the adding amount of aluminum is controlled to be 5.7-5.9% of the total mass of the raw materials, the aluminum content of the electrode is stably controlled to be 5.5%, the yield of aluminum is ensured, and the formation of inclusions is reduced; the electrode casting is carried out under vacuum condition, and the casting temperature is 1470 ℃ to 1490 ℃.

The high Al alloy electrode is prepared according to the method in the vacuum induction furnace smelting process of the high-aluminum high-temperature alloy GH6783 with the patent number of CN 108531755B.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the chemical composition of the high Al alloy electrode should meet the following specifications in weight percent:

c is less than or equal to 0.03%, si is less than or equal to 0.50%, mn is less than or equal to 0.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, al:5.00% -6.00%, B:0.003 to 0.012 percent, cr:2.50 to 3.50 percent of Ni:26.0 to 30.0 percent, cu is less than or equal to 0.50 percent, ti:0.10 to 0.40 percent of Fe:24.0% -27.0%, nb:2.50 to 3.50 percent, and the balance of Co and unavoidable impurities.

In the above-described method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the electrode diameter dimension of the high Al alloy electrode is Φ420mm to Φ440mm (for example, Φ422mm, Φ424mm, Φ426mm, Φ428mm, Φ430mm, Φ432mm, Φ434mm, Φ436mm, Φ438 mm).

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the step of preparing the high Al alloy electrode and the step of welding the electrode further include a step of electrode flat-end and a step of electrode peeling in order; preferably, the step of flat-head and flat-tail is to cut flat-head and flat-tail and end face shrinkage according to the casting condition of the electrode and the quality of the electrode head and tail; preferably, the electrode peeling step is a glazing step; further preferably, the polishing step is performed on the electrode surface by a processing amount of 3mm to 7mm (e.g., 4mm, 5mm, 6 mm); preferably 5mm.

According to the invention, flat head and tail and end face shrinkage cavity are cut completely according to the casting condition of the electrode and the quality of the head and the tail of the electrode, and finally the prepared electrode has the standard of bright surface, no oxide scale, no defects of macroscopic sand holes, holes and the like, and no shrinkage cavity leakage.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the electrode welding step is: concentrically welding the high Al alloy electrode below the dummy electrode; more preferably, the dummy electrode is a Ni-based dummy electrode.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the consumable remelting is carried out at a melting speed of 2.8kg/min to 3.4kg/min (e.g., 2.9kg/min, 3.0kg/min, 3.1kg/min, 3.2kg/min, 3.3 kg/min); preferably, the consumable remelting is performed with a smelting voltage of 23.0V-24.2V (e.g., 23.2V, 23.4V, 23.6V, 23.8V, 24.0V); preferably, the consumable remelting is performed with a smelting current of 5500A-6200A (e.g., 5600A, 5700A, 5800A, 5900A, 6000A, 6100A); preferably, helium is used for cooling in the consumable remelting step; preferably, the helium gas cooling pressure is 200Pa-500Pa (e.g., 250Pa, 300Pa, 350Pa, 400Pa, 450 Pa).

The invention can ensure that the high Al alloy steel ingot has even and fine beta-phase structure by controlling the melting speed in the consumable remelting step to keep the melting speed between 2.8kg/min and 3.4 kg/min. The helium cooling adopted in the consumable remelting step is realized by introducing helium into the gap between the steel ingot and the crystallizer.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the consumable remelting further includes maintaining for 80min-100min (for example, 82min, 84min, 86min, 88min, 90min, 92min, 94min, 96min, 98 min) in a power-off and vacuum state after the smelting is completed, and then removing ingot for air cooling to obtain a steel ingot; more preferably for 90 minutes in a powered off, vacuum state.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, a step of skinning the steel ingot is further included between the high temperature diffusion and forging steps.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the high temperature diffusion is performed at a temperature of 1150 ℃ -1200 ℃ (e.g. 1160 ℃, 1170 ℃, 1180 ℃, 1190 ℃) for a time of 105h-115h (e.g. 106h, 107h, 108h, 109h, 110h, 111h, 112h, 113h, 114 h); preferably, the high temperature diffusion is at 1180 ℃ for 110 hours.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the steel ingot used for forging has a gauge of phi 400 mm-phi 600mm (e.g., phi 425mm, phi 450mm, phi 475mm, phi 500mm, phi 525mm, phi 550mm, phi 575 mm); more preferably phi 508mm.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, the forging means that the steel ingot is prepared into a bar with the specification of phi 150mm to phi 250mm (such as phi 160mm, phi 170mm, phi 180mm, phi 190mm, phi 200mm, phi 210mm, phi 220mm, phi 230mm, phi 240 mm); more preferably phi 200mm.

In the above method for producing a high Al alloy by vacuum consumable melting, as a preferred embodiment, a checking step is further included after the forging step.

In a second aspect, the invention also provides a high Al alloy prepared by the method for producing the high Al alloy by vacuum consumable smelting.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the beta-phase morphology and the beta-phase dimension are controlled by controlling the smelting speed of the consumable process and introducing helium gas for cooling in the gap between the steel ingot and the crystallizer, so that the aim of improving the uniformity of the product structure is finally achieved.

The GH6783 alloy bar produced according to the invention has basically uniform beta-phase structure after being formed, and meets the use requirement.

The high Al alloy steel ingot prepared by the invention has uniform and fine beta-phase structure, is easy to eliminate in subsequent homogenization diffusion, and can shorten the high-temperature diffusion time by more than 50 hours.

Drawings

FIG. 1 is a metallographic structure diagram of the high Al alloy prepared in example 1;

FIG. 2 is a metallographic structure diagram of the high Al alloy prepared in example 2;

FIG. 3 is a metallographic structure diagram of the high Al alloy prepared in example 3;

fig. 4 is a metallographic structure diagram of the high Al alloy prepared in comparative example 1.

Detailed Description

Technical solutions in the embodiments of the present invention will be clearly and completely described below to enable one skilled in the art to practice and reproduce the present invention. All other embodiments, which are derived by a person skilled in the art based on the embodiments of the invention, fall within the scope of protection of the invention.

The following describes in further detail a method of vacuum consumable smelting for suppressing segregation of a high Al alloy by way of example, which is given solely for the purpose of illustrating the invention and is not intended to limit the scope of the invention. The examples provided below may be used as a basis for further modifications and applications by those of ordinary skill in the art and are not intended to limit the scope of the invention in any way.

Example 1, example 2, example 3 and comparative example 1 were performed together:

the production process flow comprises the following steps: preparing high Al alloy electrode, flat end of electrode, electrode peeling, electrode welding, consumable remelting, steel ingot peeling, diffusion, forging and inspection

In the specific production steps (1) to (8), except that the three parameters of smelting rate, smelting voltage and smelting current in the step (5) are different from each other in each example, the steps of example 1, example 2, example 3 and comparative example 1 are the same, and the specific steps are as follows:

(1) preparing a high Al alloy (GH 6783) electrode: preparing materials according to chemical components shown in table 1, vacuumizing, and keeping the vacuum degree not more than 30Pa in the smelting process; charging according to the sequence of pure metal and intermediate alloy; the vacuum degree in the refining period is controlled between 1Pa and 5Pa, the refining period is more than 90min, and the refining temperature is controlled between 1500 ℃ and 1550 ℃; adding aluminum, titanium, niobium and ferroboron, alloying, sampling and analyzing gas, oxygen content is 10.5X10% ^-6 Nitrogen content 15×10 ^-6 The temperature is measured to be 1495 ℃, the metal aluminum is added in two times according to the calculated amount, and the stirring is carried out for 5min after each addition. And casting the phi 420-phi 440mm electrode, wherein the casting temperature is 1480 ℃. The high Al alloy electrode of the embodiment is prepared according to chemical compositions shown in Table 1, and then prepared according to a method in a vacuum induction furnace smelting process of high-aluminum high-temperature alloy GH6783 with a patent number of CN 108531755B, and the diameter size phi 420-phi 440mm of the electrode is prepared;

TABLE 1 (wt%)

C

Si

Mn

P

S

Al

B

≤0.03

≤0.50

≤0.015

≤0.005

5.00～6.00

0.003～0.012

TABLE 1 (follow-up) (wt%)

Cr

Ni

Cu

Ti

Fe

Nb

Co

2.50～3.50

26.0～30.0

≤0.50

0.10～0.40

24.0～27.0

2.50～3.50

Allowance of

(2) Electrode flat head and flat tail: the flat head and the flat tail are carried out according to the casting condition of the electrode and the quality of the head and the tail of the electrode, and the shrinkage cavity of the end face is cut completely;

(3) electrode peeling: polishing the electrode, wherein the machining amount of the electrode surface is about 5mm, and cleaning the electrode surface;

(4) electrode welding: concentrically welding the prepared high Al alloy (GH 6783) electrode below the Ni-based dummy electrode;

(5) vacuum consumable remelting smelting: cooling by helium, controlling smelting speed to be 2.8-3.4kg/min, smelting voltage to be 23.0-23.2V, smelting current to be 5500A-6200A, powering off after smelting, keeping for 90min in a vacuum state, and cooling by air after ingot removal to obtain GH6783 steel ingot, wherein the specification is phi 508mm;

(6) diffusion: adopting a unified high-temperature diffusion process to carry out high-temperature diffusion on the GH6783 steel ingot, wherein the high-temperature diffusion temperature is 1180 ℃, the high-temperature diffusion time is 110 hours, sampling and analyzing C, si, al, ti, nb at the head and the tail of the steel ingot after the diffusion is finished, and turning the surface of the steel ingot for forging production after the components are qualified;

(7) forging: forging and producing GH6783 alloy phi 508mm ingots by adopting a uniform forging process to produce phi 200mm bars;

(8) and (3) checking: high-power tissue uniformity evaluation was performed on phi 200mm bars.

Example 1

GH6783 alloy is prepared, electrode ingot type phi 430+/-10 mm is remelted into phi 508mm ingot by self consumption, and the furnace number is 1420157N.

The production steps are as described in the above (1) to (8), wherein the step (5) is specifically:

(5) vacuum consumable remelting smelting, wherein the smelting speed is 2.8kg/min, the smelting voltage is 23.0V, the current is 5500A, and the helium pressure is 200Pa.

The chemical composition of the head and tail of the steel ingot obtained in the step (6) of the example is shown in Table 2

Table 2 (wt.%)

Element(s)	C	Si	Al	Ti	Nb
						Steel ingot head	0.010	0.05	5.42	0.21	3.16
Tail of steel ingot	0.011	0.04	5.34	0.20	3.13

The high-power metallographic structure diagram of the bar with the specification of phi 200mm prepared by the embodiment is shown in fig. 1, and as can be seen from fig. 1, the bar forged by the steel ingot prepared by the embodiment has uniform structure and can meet the use requirement.

Example 2

GH6783 alloy, electrode ingot type phi 430+/-10 mm, consumable remelting into phi 508mm ingot with the furnace number of 1420158N

(5) vacuum consumable remelting smelting, wherein the smelting speed adopted in smelting is 3.2kg/min, the smelting voltage is 23.5V, and the current is 6000A. The helium pressure was 400Pa.

The chemical compositions of the head and tail of the ingot obtained in step (6) of this example are shown in table 3.

TABLE 3 (wt%)

Element(s)	C	Si	Al	Ti	Nb
						Steel ingot head	0.008	0.05	5.56	0.25	3.11
Tail of steel ingot	0.010	0.04	5.53	0.24	3.07

The high-power metallographic structure diagram of the bar with the specification of phi 200mm prepared by the embodiment is shown in fig. 2, and as can be seen from fig. 2, the bar forged by the steel ingot prepared by the embodiment has uniform structure and can meet the use requirement.

Example 3

GH6783 alloy, electrode ingot type phi 430+/-10 mm, consumable remelting into phi 508mm ingot with the furnace number of 1420159N

(5) vacuum consumable remelting smelting, wherein the smelting speed adopted in smelting is 3.4kg/min, the smelting voltage is 24.2V, and the current is 6200A. Helium pressure was 500pa.

The chemical compositions of the head and tail of the ingot obtained in step (6) of this example are shown in table 4.

Table 4 (wt.%)

Element(s)	C	Si	Al	Ti	Nb
						Steel ingot head	0.009	0.04	5.61	0.23	3.06
Tail of steel ingot	0.010	0.04	5.59	0.24	3.09

The high-power metallographic structure diagram of the bar with the specification of phi 200mm prepared by the embodiment is shown in fig. 3, and as can be seen from fig. 3, the bar forged by the steel ingot prepared by the embodiment has uniform structure and can meet the use requirement.

Comparative example 1

The comparative example was essentially the same as the example procedure, except that during the vacuum consumable process, a melt rate of 3.7kg/min was used.

As shown in FIG. 4, it can be seen from FIG. 4 that after the melting speed is increased, coarse β -phase structures are precipitated in the steel ingot prepared according to the high-temperature diffusion process of example 1, and the steel ingot cannot meet the use requirement, and the high-temperature diffusion time is prolonged by at least 60 hours based on the high-temperature diffusion process of example 1.

The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims

1. The method for producing the high Al alloy by adopting vacuum consumable smelting is characterized by comprising the following steps in sequence: preparing a high Al alloy electrode, welding the electrode, consumable remelting, high-temperature diffusion and forging;

the diameter size of the electrode of the high Al alloy electrode is phi 420 mm-phi 440mm;

the melting speed adopted by the consumable remelting is 2.8kg/min-3.4kg/min; consumable remelting adopts smelting voltage of 23.0V-24.2V; consumable remelting adopts a smelting current of 5500A-6200A; helium is adopted for cooling in the consumable remelting step; the cooling pressure of helium is 200Pa-500Pa;

the high-temperature diffusion temperature is 1150-1200 ℃ and the time is 105-115 hours;

the chemical components of the high Al alloy electrode are calculated according to the weight percentage and accord with the following regulations:

c is less than or equal to 0.03%, si is less than or equal to 0.50%, mn is less than or equal to 0.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, al:5.00% -6.00%, B:0.003% -0.012%, cr:2.50 to 3.50 percent of Ni:26.0 to 30.0 percent, cu is less than or equal to 0.50 percent, ti:0.10 to 0.40 percent of Fe:24.0% -27.0%, nb:2.50 to 3.50 percent, and the balance of Co and unavoidable impurities.

2. The method of claim 1, wherein the step of preparing a high Al alloy electrode and the step of welding the electrode are sequentially followed by a step of flat-end electrode and a step of electrode peeling.

3. The method of claim 2, wherein the step of flattening the butt comprises flattening the butt and end face shrinkage cavity cutting according to the casting condition of the electrode and the mass of the head and the tail of the electrode.

4. The method of claim 2, wherein the electrode skinning step is a vehicle lighting.

5. The method of claim 4, wherein the polishing step is performed on the electrode surface in an amount of 3mm to 7mm.

6. The method of claim 5, wherein the polishing step is performed with a 5mm finish on the electrode surface.

7. The method of claim 1, wherein the electrode welding step is: and concentrically welding the high Al alloy electrode below the false electrode.

8. The method of claim 7, wherein the dummy electrode is a Ni-based dummy electrode.

9. The method of claim 1, wherein the consumable remelting further comprises maintaining the consumable ingot in a powered-off, vacuum state for 80-100 min after the smelting is completed, and then removing the ingot for air cooling to obtain the steel ingot.

10. The method of claim 9, wherein the holding is performed for 90 minutes in a powered off, vacuum state.

11. The method of claim 1, further comprising a step of scalping the ingot between the high temperature diffusion and forging steps.

12. The method of claim 1, wherein the high temperature diffusion is at 1180 ℃ for 110 hours.

13. The method of claim 1, wherein the ingot gauge used for forging is phi 400-phi 600mm.

14. The method of claim 13, wherein the ingot gauge used for forging is phi 508mm.

15. The method of claim 13, wherein the forging is to prepare the steel ingot into bars with a specification of phi 150-phi 250 mm.

16. The method of claim 15, wherein the forging means preparing the ingot to a gauge Φ200mm.

17. The method of claim 1, further comprising a verification step after the forging step.

18. A high Al alloy prepared by the method of any one of claims 1-17.