阅读说明：本技术 一种恒熔速电渣炉自动补缩工艺 (Automatic feeding process of electroslag furnace with constant melting speed ) 是由 王文洋 王晓飞 黄开元 翟文进 张宇 林志强 于 2021-08-05 设计创作，主要内容包括：本发明涉及一种恒熔速电渣炉自动补缩工艺,补缩阶段以瞬时熔化率的变化为控制中心,实际补缩时间不固定,根据补缩重量到达节点来具体确定。所述补缩过程共分为5个阶段,其中1、3阶段为功率递减阶段,2、4阶段为功率保持阶段,补缩的主要过程为第2和第4阶段,第5阶段为保温阶段,所述第1和第3阶段的具体时间并不固定,第2和第4阶段保持所用的时间为10min。避免了传统补缩方法存在的功率降低时,由于热量累积导致的熔化率不降或者反而升高的现象,保证达到补缩目的。(The invention relates to an automatic feeding process of a constant melting speed electroslag furnace, wherein the feeding stage takes the change of instantaneous melting rate as a control center, the actual feeding time is not fixed, and the actual feeding time is specifically determined according to the arrival node of feeding weight. The feeding process is divided into 5 stages, wherein the stages 1 and 3 are power decreasing stages, the stages 2 and 4 are power maintaining stages, the main feeding process is the stages 2 and 4, the stage 5 is a heat preservation stage, the specific time of the stages 1 and 3 is not fixed, and the time for maintaining the stages 2 and 4 is 10 min. The phenomenon that the melting rate is not reduced or is increased instead due to heat accumulation when the power is reduced in the traditional feeding method is avoided, and the feeding purpose is ensured.)

1. An automatic feeding process of an electroslag furnace with constant melting speed is characterized in that: the feeding stage takes the change of the instantaneous melting rate as a control center, the total time range of the whole feeding stage is t = 7-10 v, the unit is min, wherein v is the set melting rate of the normal remelting stage, the unit of the melting rate is kg/min, and the time when the actual feeding stage is finished is specifically determined by the weight of the consumable electrode residual disc reaching the weight of a preset residual disc;

the whole feeding process is artificially divided into 5 stages, wherein the 1 st feeding stage and the 3 rd feeding stage are power decreasing stages, the 2 nd feeding stage and the 4 th feeding stage are power maintaining stages, the main processes of feeding are the 2 nd feeding stage and the 4 th feeding stage, and the 5 th feeding stage is a heat preservation stage; after entering a feeding stage from a normal smelting stage, the voltage and the current are reduced at different rates according to different stages;

the starting time of the 2 nd feeding stage and the 4 th feeding stage is respectively related to the change condition of the melting rate, when the real-time melting rate is reduced to the range of 0.80-0.70 times of the remelting set melting rate, the 2 nd feeding stage starts, and the time for keeping is 10 min; when the real-time melting rate is reduced to the range (0.40-0.30) times of the remelting set melting rate, starting the feeding stage 4, and keeping the time for 10 min; the specific time of the 1 st feeding stage and the 3 rd feeding stage is not fixed, and feeding enters the 2 nd feeding stage and the 4 th feeding stage only when the melting rate reaches a preset value;

the selection of the melting rate multiplying factor of the interval range of the 2 nd feeding stage and the 4 th feeding stage is related to the rate of the reduction of the former melting rate, when the melting rate is reduced more quickly, the upper limit value of the range is selected by the melting rate multiplying factor, otherwise, the lower limit value of the range is selected.

Technical Field

The invention belongs to the technical field of electroslag metallurgy, and particularly relates to an automatic feeding process of a constant-melting-speed electroslag furnace, which avoids the phenomenon that the melting rate is not reduced or is increased instead due to heat accumulation when the power is reduced in the traditional feeding method, and ensures the feeding purpose.

Background

Electroslag remelting is a secondary refining technology, and is a remelting and recasting process which is carried out in a copper water-cooled crystallizer and has slag participating in chemical and physical reactions. In the later stage of electroslag smelting, when a metal molten pool is converted from a liquid phase into a solid phase, the volume of the metal molten pool is contracted by about 3-6%, and if the contracted volume is not supplemented by molten steel in time, an electroslag ingot shrinkage cavity is formed. The defects of looseness, segregation and the like caused by shrinkage cavities often cause quality problems of cracking, strip defects and the like at the riser end of the electroslag ingot in the forging process, simultaneously reduce the forging utilization rate and greatly influence the product quality and the production cost.

The traditional electroslag feeding method has two types, namely manual feeding and automatic feeding, and both feeding methods realize the shallow of a metal molten pool by decreasing power to achieve the purpose of feeding. The decrement of power is completed through the control of secondary current and secondary voltage. However, in actual electroslag operation, the same power does not mean the same amount of melting rate and the same depth of the molten metal bath due to the difference in the amount of heat accumulated in the slag bath and the molten metal bath. This results in unstable feeding quality of the dead head end of the electroslag ingot. By the same feeding method, the shrinkage cavity defect of the electroslag ingot riser with good feeding control can be controlled to be less than 50mm, the shrinkage cavity defect of the electroslag ingot riser with poor feeding control can reach about 200mm, and the quality level difference is very obvious.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide the automatic feeding process of the constant melting speed electroslag furnace, which is stable in operation and good in feeding quality.

In order to solve the above problems, the technical solution of the present invention is realized as follows:

an automatic feeding process of an electroslag furnace with a constant melting speed is characterized in that the change of an instantaneous melting rate is taken as a control center in a feeding stage, the total time range of the whole feeding stage is t = 7-10 v, the unit is min, v is a set melting rate of a normal remelting stage, the unit of the melting rate is kg/min, and the time for finishing the actual feeding stage is specifically determined by the weight of a consumable electrode residual disc reaching the weight of a preset residual disc;

the whole feeding process is artificially divided into 5 stages, wherein the 1 st feeding stage and the 3 rd feeding stage are power decreasing stages, the 2 nd feeding stage and the 4 th feeding stage are power maintaining stages, the main processes of feeding are the 2 nd feeding stage and the 4 th feeding stage, and the 5 th feeding stage is a heat preservation stage. After entering a feeding stage from a normal smelting stage, the voltage and the current are reduced at different rates according to different stages;

the starting time of the 2 nd feeding stage and the 4 th feeding stage is respectively related to the change condition of the melting rate, when the real-time melting rate is reduced to the range of 0.80-0.70 times of the remelting set melting rate from the normal melting speed, the 2 nd feeding stage starts, and the time for keeping is 10 min; when the real-time melting rate is reduced to the range (0.40-0.30) times of the remelting set melting rate, starting the feeding stage 4, and keeping the time for 10 min; the specific time of the 1 st feeding stage and the 3 rd feeding stage is not fixed, and feeding enters the 2 nd feeding stage and the 4 th feeding stage only when the melting rate reaches a preset value.

The selection of the melt rate multiplier factor for the interval between feeding stages 2 and 4 is related to the rate at which its previous melt rate decreases. When the melting rate is decreased rapidly, the upper limit value of the range is selected by the melting rate multiplying factor, and the lower limit value of the range is selected otherwise.

The technical scheme of the invention has the following positive effects:

the automatic feeding process of the electroslag furnace with the constant melting speed takes the change of the melting rate as a control center, and the difference of current and voltage in each stage is ignored artificially.

The automatic feeding process of the electroslag furnace with the constant melting speed avoids the phenomenon that the melting rate is not reduced or is increased instead due to heat accumulation when the power is reduced in the traditional feeding method, and ensures that a metal melting pool can be gradually shallow.

In the automatic feeding process of the electroslag furnace with the constant melting speed, the 2 nd feeding stage keeps the melting speed of the consumable electrode slightly lower than the solidification speed of a metal molten pool, and at the stage, the molten pool is relatively deep, and a metal solid-liquid line moves upwards slowly, so that the generation of an electroslag hidden shrinkage cavity is favorably prevented.

According to the automatic feeding process of the electroslag furnace with the constant melting speed, the feeding stage 4 is kept under the condition of a lower melting rate, so that feeding metal liquid is conveniently controlled not to be excessive, the normal thickness of a consumable electrode retaining disc is ensured, and deep open shrinkage holes are prevented from being generated by electroslag.

The specific implementation mode is as follows:

example 1: an automatic feeding process of an electroslag furnace with constant melting speed selects a 42CrMoA steel type, and the specification of an ingot type is as follows: 7.6 ton, crystallizer: Φ 790/830mm, quantity: 3, slag system: CaF₂:Al₂O₃CaO =65:30:5, slag amount: 300kg, the specification of the consumable electrode is phi 600mm die casting blank, and the set melting rate of the normal electroslag remelting stage is 9.5 kg/min.

And theoretically calculating the theoretical total time of the electroslag remelting feeding stage to be 67-95 min according to t = 7-10 v.

When the real-time melting rate is reduced to the range of (0.80-0.70) times of the set melting rate of remelting, the range of the melting rate at the beginning of the feeding stage 2 is 7.6-6.6 kg/min, and the range of the melting rate at the beginning of the feeding stage 4 is 3.8-2.8 kg/min according to theoretical calculation. The melting rate at the start of the 2 nd feeding stage was set to 7kg/min, and the melting rate at the start of the 4 th feeding stage was set to 3.5 kg/min.

After entering the feeding stage, along with the reduction of power, when the real-time melting rate is reduced to 7kg/min, the feeding stage 2 starts, the current and the voltage are kept unchanged for 10 minutes, then the power is continuously reduced, when the real-time melting rate is reduced to 3.5kg/min, the feeding stage 4 starts, the current and the voltage are kept unchanged for 10 minutes, and then the feeding stage 5 enters the heat preservation stage.

The ultrasonic flaw detection conditions of the 42CrMoA slag ingot after annealing and discharging are as follows: .

Ultrasonic flaw detection result of table 142 CrMoA electroslag ingot

Furnace number	Ingot mould	Ultrasonic flaw detectionResults
			8A2118	7.6t	The shrinkage cavity of a riser is less than or equal to 30mm through ultrasonic flaw detection
8A2119	7.6t	The shrinkage cavity of a riser is less than or equal to 30mm through ultrasonic flaw detection
			8A2120	7.6t	The shrinkage cavity of a riser is less than or equal to 30mm through ultrasonic flaw detection

From the above table, it can be seen that: the process of the invention is adopted to carry out electroslag feeding, and after an electroslag ingot product is annealed and discharged from a furnace, ultrasonic flaw detection is carried out on the electroslag ingot product, shrinkage cavities of a riser are all less than or equal to 30mm, and compared with the product produced by the traditional feeding process, the shrinkage cavities are shallow and have stable quality.