阅读说明：本技术 一种钛合金铸锭起弧建立熔池的方法 (Method for establishing molten pool by titanium alloy ingot striking ) 是由 刘鹏 梁敬凡 王龙周 尚金金 雷强 何永胜 何涛 刘向弘 于 2020-12-16 设计创作，主要内容包括：本发明属于钛合金铸锭熔炼领域,具体涉及一种钛合金铸锭起弧建立熔池的方法。该方法包括以下步骤：S1：将自耗电极装入坩埚中,并置于熔炼设备内,然后对设备进行抽真空处理；S2：将辅助电极及自耗电极在熔炼设备内进行焊接,焊接后开炉清理焊瘤,重新对设备进行抽真空处理；S3：设定冷却水参数和起弧参数,起弧参数包括起弧电流,起弧电流随时间逐步增大,起弧电流上升过程的中部设置台阶电流；S4：打开熔炼设备电源,进行起弧熔炼；S5：关闭电源冷却后出炉。本方法的优势在于：1.可以消除铸锭尾部夹生、冷隔、分层、裂纹等缺陷；2.利于铸锭尾部合金化和均匀化；3.明显降低熔池健全重量。(The invention belongs to the field of titanium alloy ingot smelting, and particularly relates to a method for establishing a molten pool by arcing a titanium alloy ingot. The method comprises the following steps: s1: the consumable electrode is arranged in a crucible and is placed in smelting equipment, and then the equipment is vacuumized; s2: welding the auxiliary electrode and the consumable electrode in a smelting device, opening a furnace to clean welding beading after welding, and vacuumizing the device again; s3: setting cooling water parameters and arc starting parameters, wherein the arc starting parameters comprise arc starting current, the arc starting current is gradually increased along with time, and step current is arranged in the middle of the rising process of the arc starting current; s4: turning on a power supply of smelting equipment to perform arc starting smelting; s5: and (5) discharging the furnace after the power supply is turned off and the furnace is cooled. The method has the advantages that: 1. the defects of entrainment, cold shut, delamination, cracks and the like at the tail part of the cast ingot can be eliminated; 2. the alloying and homogenization of the tail of the cast ingot are facilitated; 3. the sound weight of the molten pool is obviously reduced.)

1. A method for establishing a molten pool by titanium alloy ingot arcing is characterized by comprising the following steps:

s1: the consumable electrode is arranged in a crucible and is placed in smelting equipment, and then the equipment is vacuumized;

s2: welding the auxiliary electrode and the consumable electrode in a smelting device, opening a furnace to clean welding beading after welding, and vacuumizing the device again;

s3: setting cooling water parameters and arc starting parameters, wherein the arc starting parameters comprise arc starting current, the arc starting current is gradually increased along with time, step current is arranged in the middle of the rising process of the arc starting current, and the step current is used for preheating cast ingots;

s4: turning on a power supply of smelting equipment to perform arc starting smelting;

s5: and (5) discharging the furnace after the power supply is turned off and the furnace is cooled.

2. A method of arcing a molten pool of a titanium alloy ingot as set forth in claim 1, wherein the arcing parameters of step S3 are carried out in sequence as follows:

s31: and (3) stabilizing the arc: setting the arcing current to be 4-7kA, the arcing voltage to be 26-28V and the arc stabilizing current to be 2-8A, and keeping for 4-6 min;

s32: an auxiliary stage: setting an arc starting current of 8-12kA, an arc starting voltage of 28-30V and an arc stabilizing current of 2-8A, and keeping for 1-2 min;

s33: preheating the ingot: setting an arc starting current of 8-12kA, an arc starting voltage of 28-30V and an arc stabilizing current of 2-8A, and keeping for 8-15 min;

s34: establishing a molten pool stage 1: setting 20-35kA of arcing current, 32-37V of arcing voltage and 8-25A of arc stabilizing current, and keeping for 1-2 min;

s35: establishing a molten pool stage 2: setting the arcing current to be more than or equal to 20kA, the arcing voltage to be more than or equal to 32V and the arc stabilizing current to be more than or equal to 8A, and keeping the arcing current to be more than or equal to 5 min;

the auxiliary stage and the ingot preheating stage are the step current.

3. A method of establishing a molten pool for arcing a titanium alloy ingot according to claim 1, wherein said cooling water parameters are: the water inlet temperature is 23-27 ℃, the cooling water flow is 300-.

4. The method of claim 1, wherein the ingot gauge is between 640mm and 920 mm.

5. The method of claim 1, wherein the melting apparatus is a consumable electrode vacuum arc furnace.

6. The method for establishing a molten pool by arcing a titanium alloy ingot according to claim 1, wherein in step S1, vacuum is applied until the vacuum degree is less than or equal to 5Pa and the leak rate is less than or equal to 3.0 Pa/min.

7. The method for establishing a molten pool for arcing a titanium alloy ingot according to claim 1, wherein said welding parameters of step S2 are: the welding current is 4-11 kA, the welding voltage is 24-32V, and the welding time is more than or equal to 5 min.

8. The method for establishing a molten pool by arcing a titanium alloy ingot according to claim 7, wherein said step S2 is performed by re-evacuating to a vacuum degree of 0.8Pa or less and a leak rate of 3.0Pa/min or less.

9. The method of claim 7, wherein said step S4 is performed such that the consumable electrode is maintained at an arc distance of 25-35mm before the arc is melted.

Technical Field

The invention belongs to the field of titanium alloy ingot smelting, and particularly relates to a method for establishing a molten pool by arcing a titanium alloy ingot.

Background

Titanium and titanium alloy have high specific strength, good high temperature performance, excellent corrosion resistance, excellent fatigue performance and other advantages, and are widely applied to the fields of aviation, aerospace, medical treatment, ships and warships and the like. But the price is high, and the titanium alloy becomes one of the main factors for restricting the further application of the titanium and the titanium alloy.

Currently, the most common method for producing titanium alloys is VAR melting, i.e. vacuum consumable arc furnace melting. The VAR smelting process is divided into three stages: an arcing period, a normal smelting period and a heat sealing top period (also called a feeding period). The main purpose of the arc striking period is to stabilize the electric arc and establish a molten pool; the main purpose of the normal smelting period is stable smelting, full alloying and homogenization; the main purpose of the heat capping period is to reduce shrinkage porosity and reduce the amount of head cutting.

In the three stages, the arc starting period and the heat sealing top period belong to unstable processes. In the arc striking period, a molten pool is established by gradually increasing current and voltage; the heat capping period is carried out by gradually reducing the current and the voltage. Therefore, the chemical composition uniformity of the ingot in the arcing period and the heat-seal top period is slightly inferior to that in the normal melting period, and segregation may occur in the case of severe cases.

For titanium and titanium alloy ingots, hot crown technology has been well studied, but very little has been studied for the arcing phase. In actual production, the common defects of the tail of the cast ingot comprise entrainment, delamination, cold shut, cracks and the like, the metallurgical quality of the tail area of the cast ingot is directly influenced, and the tail area of the cast ingot needs to be removed by sawing in serious cases, so that great cost loss is caused.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a method for establishing a molten pool by arcing a titanium alloy ingot.

In order to achieve the purpose, the invention provides the following technical scheme:

a method for establishing a molten pool by titanium alloy ingot arcing comprises the following steps:

s1: the consumable electrode is arranged in a crucible and is placed in smelting equipment, and then the equipment is vacuumized;

s2: welding the auxiliary electrode and the consumable electrode in a smelting device, opening a furnace to clean welding beading after welding, and vacuumizing the device again;

s3: setting cooling water parameters and arc starting parameters, wherein the arc starting parameters comprise arc starting current, the arc starting current is gradually increased along with time, step current is arranged in the middle of the rising process of the arc starting current, and the step current is used for preheating cast ingots;

s4: turning on a power supply of smelting equipment to perform arc starting smelting;

s5: and (5) discharging the furnace after the power supply is turned off and the furnace is cooled.

Further, the arc starting parameters in the step S3 are sequentially performed according to the following steps:

s31: and (3) stabilizing the arc: setting the arcing current to be 4-7kA, the arcing voltage to be 26-28V and the arc stabilizing current to be 2-8A, and keeping for 4-6 min;

s32: an auxiliary stage: setting an arc starting current of 8-12kA, an arc starting voltage of 28-30V and an arc stabilizing current of 2-8A, and keeping for 1-2 min;

s33: preheating the ingot: setting an arc starting current of 8-12kA, an arc starting voltage of 28-30V and an arc stabilizing current of 2-8A, and keeping for 8-15 min;

s34: establishing a molten pool stage 1: setting 20-35kA of arcing current, 32-37V of arcing voltage and 8-25A of arc stabilizing current, and keeping for 1-2 min;

s35: establishing a molten pool stage 2: setting the arcing current to be more than or equal to 20kA, the arcing voltage to be more than or equal to 32V and the arc stabilizing current to be more than or equal to 8A, and keeping the arcing current to be more than or equal to 5 min;

the auxiliary stage and the ingot preheating stage are the step current.

Further, the cooling water parameters are as follows: the water inlet temperature is 23-27 ℃, the cooling water flow is 300-.

Furthermore, the specification of the ingot is phi 640 mm-phi 920 mm.

Further, the smelting equipment is a vacuum consumable electrode furnace.

Further, in step S1, vacuum degree is pumped until the vacuum degree is less than or equal to 5Pa, and leakage rate is less than or equal to 3.0 Pa/min.

Further, the welding parameters of step S2 are: the welding current is 4-11 kA, the welding voltage is 24-32V, and the welding time is more than or equal to 5 min.

Further, in step S2, vacuum is pumped again until the vacuum degree is less than or equal to 0.8Pa and the leakage rate is less than or equal to 3.0 Pa/min.

Further, in the step S4, before arc starting smelting, the arc distance of the consumable electrode is ensured to be 35-35 mm.

Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:

1) the defects of entrainment, cold shut, delamination, cracks and the like at the tail part of the cast ingot can be eliminated;

2) the alloying and homogenization of the tail of the cast ingot are facilitated;

3) the healthy weight of the molten pool is obviously reduced;

4) the method is simple to operate, easy to realize and few in human intervention factors.

Drawings

FIG. 1 is a surface quality map of an ingot of a comparative example of the present invention;

FIG. 2 is a surface quality map of an ingot according to an embodiment of the invention;

FIG. 3 is a graph of the bath health weight of the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

a method for establishing a molten pool by titanium alloy ingot arcing is characterized by comprising the following steps:

s1: the consumable electrode is arranged in a crucible and is placed in smelting equipment, and then the equipment is vacuumized;

s2: welding the auxiliary electrode and the consumable electrode in a smelting device, opening a furnace to clean welding beading after welding, and vacuumizing the device again;

s3: setting cooling water parameters and arc starting parameters, wherein the arc starting parameters comprise arc starting current, the arc starting current is gradually increased along with time, step current is arranged in the middle of the rising process of the arc starting current, and the step current is used for preheating cast ingots;

s4: turning on a power supply of smelting equipment to perform arc starting smelting;

s5: and (5) discharging the furnace after the power supply is turned off and the furnace is cooled.

Further, the arc starting parameters in the step S3 are sequentially performed according to the following steps:

s31: and (3) stabilizing the arc: setting the arcing current to be 4-7kA, the arcing voltage to be 26-28V and the arc stabilizing current to be 2-8A, and keeping for 4-6 min;

s32: an auxiliary stage: setting an arc starting current of 8-12kA, an arc starting voltage of 28-30V and an arc stabilizing current of 2-8A, and keeping for 1-2 min;

s33: preheating the ingot: setting an arc starting current of 8-12kA, an arc starting voltage of 28-30V and an arc stabilizing current of 2-8A, and keeping for 8-15 min;

s34: establishing a molten pool stage 1: setting 20-35kA of arcing current, 32-37V of arcing voltage and 8-25A of arc stabilizing current, and keeping for 1-2 min;

s35: establishing a molten pool stage 2: setting the arcing current to be more than or equal to 20kA, the arcing voltage to be more than or equal to 32V and the arc stabilizing current to be more than or equal to 8A, and keeping the arcing current to be more than or equal to 5 min;

the auxiliary stage and the ingot preheating stage are the step current.

Further, the cooling water parameters are as follows: the water inlet temperature is 23-27 ℃, the cooling water flow is 300-.

Furthermore, the specification of the ingot is phi 640 mm-phi 920 mm.

Further, the smelting equipment is a vacuum consumable electrode furnace.

Further, in step S1, vacuum degree is pumped until the vacuum degree is less than or equal to 5Pa, and leakage rate is less than or equal to 3.0 Pa/min.

Further, the welding parameters of step S2 are: the welding current is 4-11 kA, the welding voltage is 24-32V, and the welding time is more than or equal to 5 min.

Further, in step S2, vacuum is pumped again until the vacuum degree is less than or equal to 0.8Pa and the leakage rate is less than or equal to 3.0 Pa/min.

Further, in the step S4, before arc starting smelting, the arc distance of the consumable electrode is ensured to be 35-35 mm.

The principle of the invention is as follows:

1. the self energy of the ingot is improved before the ingot is melted, and the ingot is preheated mainly through a step current stage (namely S3 step); the titanium alloy smelting adopts a high-current low-voltage mode, the ingot casting does not generate a melting phenomenon due to electric arc in a step current action stage, the temperature of the ingot casting is improved along with the stability of the arc light, the heat of the arc light is gradually improved, the energy of the ingot casting is continuously improved, and the aim of preheating the ingot casting is further fulfilled.

2. The arc distance and state are controlled to ensure that the energy of the electric arc uniformly preheats the end face of the ingot (controlled by the arc distance and the arc stabilization). The arc distance is one of the crucial parameters in the smelting process of titanium alloy. The smaller the arc distance is, the smaller the voltage is, the more the arc light is concentrated on the center position of the end surface of the ingot, the easy formation of the phenomenon of coring and melting is not beneficial to the leveling control of the end surface of the ingot, and certain quality hidden danger is caused; the larger the arc distance is, the easier the arc light is to disperse, and even the phenomena of side arc, arc climbing and the like occur, which is not beneficial to safe production; the arc light can be uniformly dispersed on the end surface of the cast ingot by the reasonable arc distance, so that the uniform preheating effect is achieved, the phenomena of arc deflection, arc climbing and the like can be prevented, and the stable spreading of a molten pool is facilitated.

3. The water cooling strength at the initial stage of arc striking is weakened, and supercooling is prevented. Mainly by controlling the cooling water flow, the inlet water temperature and the water pressure. In the process of titanium alloy arc consumable melting, a copper crucible is mainly used as a crystallizer, a red copper base pad with excellent heat conductivity is arranged at the bottom of the copper crucible, and the crucible is placed in a water cooling system for heat exchange, so that the effects of melting and solidifying at the same time are achieved. For the cast ingot arcing process, the bottom water inlet temperature and the water pressure have a decisive role in the cooling effect. According to the crucible cooling result, the bottom of the cast ingot at the arcing stage mainly relates to two processes of convection heat transfer and conduction heat transfer, and according to the Newton cooling formula and the Fourier law, the lower the water inlet temperature is, the lower the water pressure is, the smaller the heat transfer amount is, and the more the heat storage amount is favorable for melting. However, in actual production, heat exchange is too low, and heat storage is increased along with smelting, so that certain potential safety hazards are caused, and proper water inlet temperature, water flow and water pressure are required.

Example 1

In this example, which is a control group, a conventional method is used to establish a molten pool for a phi 720mm titanium alloy ingot:

s1: preparing a TC4 titanium alloy consumable electrode with the diameter of phi 640 mm;

s2: the consumable electrode in the step S1 is put into a crucible with the diameter of 720mm for smelting ingots with the diameter of 720mm, and the gap between the crucibles is ensured to be more than or equal to 30 mm;

s3: evacuating until the vacuum degree is less than or equal to 5Pa and the leakage rate is less than or equal to 3.0 Pa/min;

s4: carrying out furnace welding in a vacuum consumable arc furnace, wherein the welding current is 7kA, the welding voltage is 25V, and the welding time is 10 min;

s5: checking a furnace, and cleaning floating ash and splashing generated in the welding process;

s6: re-evacuating until the vacuum degree is less than or equal to 0.8Pa and the leakage rate is less than or equal to 1.0 Pa/min;

s7: the water pressure is not controlled and default values are used. Generally 0.5 plus or minus 0.1 MPa;

s8: setting the temperature of inlet water to 20 ℃ and the actual temperature to 18-22 ℃;

s9: setting the water flow at 800L/min, wherein the actual water flow is 700L/min-900L/min;

s10: the arcing process was entered as follows:

step (ii) of	Time/min	current/kA	voltage/V	Arc stabilization/A
					1	4	6	27	10
2	1	30	34	15
					3	10	30	34	15

S11: turning on a power supply of the equipment, controlling the arc distance to be 24mm +/-0.5 mm, and carrying out arc starting smelting until the smelting is finished; and (5) turning off the power supply, cooling for at least 6.0h, and discharging.

Example 2

In this embodiment, the method of the present invention is used to establish a molten pool for a titanium alloy ingot with a diameter of 640 mm:

s1: preparing a TC4 titanium alloy consumable electrode with the diameter of phi 560 mm;

s2: the consumable electrode in the step S1 is put into a crucible with the diameter of phi 640mm for smelting cast ingots with the diameter of phi 640mm, and the gap between the crucibles is ensured to be more than or equal to 30 mm;

s3: evacuating until the vacuum degree is less than or equal to 5Pa and the leakage rate is less than or equal to 3.0 Pa/min;

s4: carrying out furnace welding in a vacuum consumable arc furnace, wherein the welding current is 8kA, the welding voltage is 26V, and the welding time is 8 min;

s5: checking a furnace, and cleaning floating ash and splashing generated in the welding process;

s6: re-evacuating until the vacuum degree is less than or equal to 0.8Pa and the leakage rate is less than or equal to 1.0 Pa/min;

s7: setting the pressure of cooling water to 0.5MPa, wherein the actual pressure needs to reach 0.5 +/-0.05 MPa;

s8: setting the temperature of inlet water to 25 ℃ and the actual temperature to 23-27 ℃;

s9: setting the water flow to be 500L/min, wherein the actual water flow is 300-700L/min;

s10: the arcing process was entered as follows:

s11: turning on a power supply of the equipment, adjusting the stroke of the electrode rod within 1min, ensuring the arc distance to be about 25mm, and carrying out arc starting smelting until the smelting is finished; and (5) turning off the power supply, cooling for at least 4.0h, and discharging.

Example 3

In this embodiment, the method of the present invention is used to establish a molten pool for a phi 720mm titanium alloy ingot:

s1: preparing a TC4 titanium alloy consumable electrode with the diameter of phi 640 mm;

s2: the consumable electrode in the step S1 is put into a crucible with the diameter of 720mm for smelting ingots with the diameter of 720mm, and the gap between the crucibles is ensured to be more than or equal to 30 mm;

s3: evacuating until the vacuum degree is less than or equal to 5Pa and the leakage rate is less than or equal to 3.0 Pa/min;

s4: carrying out furnace welding in a vacuum consumable arc furnace, wherein the welding current is 13kA, the welding voltage is 34V, and the welding time is 7 min;

s5: checking a furnace, and cleaning floating ash and splashing generated in the welding process;

s6: re-evacuating until the vacuum degree is less than or equal to 0.8Pa and the leakage rate is less than or equal to 1.0 Pa/min;

s7: setting the pressure of cooling water to 0.5MPa, wherein the actual pressure needs to reach 0.5 +/-0.05 MPa;

s8: setting the temperature of inlet water to 27 ℃, and the actual temperature to 23-27 ℃;

s9: setting the water flow to 700L/min, wherein the actual water flow is 300-700L/min;

s10: the arcing process was entered as follows:

s11: turning on a power supply of the equipment, adjusting the stroke of an electrode rod within 1min, ensuring that the arc distance is about 35mm, and carrying out arc starting smelting until the smelting is finished; and (5) turning off the power supply, cooling for at least 6.0h, and discharging.

Example 4

In this embodiment, the method of the present invention is used to establish a molten pool for a titanium alloy ingot with a diameter of 920 mm:

s1: preparing a TC4 titanium alloy consumable electrode with the diameter of phi 850 mm;

s2: the consumable electrode in the step S1 is put into a crucible with the diameter of phi 920mm for smelting ingots with the diameter of phi 920mm, and the gap between the crucibles is ensured to be more than or equal to 30 mm;

s3: evacuating until the vacuum degree is less than or equal to 5Pa and the leakage rate is less than or equal to 3.0 Pa/min;

s4: carrying out furnace welding in a vacuum consumable arc furnace, wherein the welding current is 7kA, the welding voltage is 27V, and the welding time is 9 min;

s5: checking a furnace, and cleaning floating ash and splashing generated in the welding process;

s6: re-evacuating until the vacuum degree is less than or equal to 0.8Pa and the leakage rate is less than or equal to 1.0 Pa/min;

s7: setting the pressure of cooling water to 0.5MPa, wherein the actual pressure needs to reach 0.5 +/-0.05 MPa;

s8: setting the temperature of inlet water at 23 ℃ and the actual temperature at 23-27 ℃;

s9: setting the water flow to 300L/min, wherein the actual water flow is 300-700L/min;

s10: the arcing process was entered as follows:

s11: turning on a power supply of the equipment, adjusting the stroke of the electrode rod within 1min, ensuring the arc distance to be about 30mm, and carrying out arc starting smelting until the smelting is finished; and (5) turning off the power supply, cooling for at least 6.0h, and discharging.

As shown in FIG. 1, which is a graph of an ingot obtained by melting a titanium alloy with a diameter of 720mm in the conventional method in example 1, and FIG. 2 is a graph of an ingot obtained by melting a titanium alloy with a diameter of 720mm in the conventional method in example 2, it can be seen that the bottom of a finished ingot obtained by the conventional arc starting method (example 1) is always provided with obvious cold shut and even bottom cracks. The invention realizes the functions of stabilizing arc light, preheating cast ingots and perfecting a molten pool by controlling parameters such as current, voltage, arc stabilization, time, water flow, water inlet temperature, arc distance and the like in the arcing period, reduces perfecting weight of the molten pool, improves bottom quality of the cast ingots, and is more beneficial to alloying and homogenization.

FIG. 3 is a graph of bath sound weight, showing that the bath is lighter in weight, reducing material loss and reducing cost using the present invention.

As shown in Table 1, the uniformity of the chemical composition of the bottom of the ingot after the titanium alloy with the diameter of 720mm is smelted in example 2, the chemical composition test results of 9 positions in the ingot are shown in the table, the last column is the range value which is the difference value between the maximum value and the minimum value of each component and is an index for evaluating the uniformity, and the range values of Al element and V element are both 0.05, so that the chemical composition of the bottom of the ingot after the method is adopted is uniform, and the metallurgical quality is improved.

Table 1 ingot bottom chemical composition uniformity/wt.% of the invention

Position of	Al	V	Ti
				1	6.68	4.41	Base body
2	6.69	4.41	Base body
				3	6.69	4.38	Base body
4	6.68	4.36	Base body
				5	6.71	4.40	Base body
6	6.67	4.38	Base body
				7	6.66	4.39	Base body
8	6.71	4.41	Base body
				9	6.69	4.38	Base body
Extreme difference	0.05	0.05	Base body