Feeding method for zirconium and zirconium alloy finished product cast ingot smelting
By controlling the feeding process of zirconium and zirconium alloy ingots in stages using the VAR method, adjusting the melting current and arc voltage, and optimizing the feeding process of zirconium and zirconium alloy ingots, the problem of unstable riser depth in zirconium ingot melting was solved, and the yield and production efficiency were improved.
Patent Information
- Application Number
- CN202512008334.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-17
AI Technical Summary
In existing technologies, the zirconium ingot smelting and feeding process is inconsistent, resulting in unstable riser depth, unstable yield, and increased production costs.
By controlling the feeding stage of zirconium and zirconium alloy ingots smelted by VAR method in stages, adjusting the smelting current, current drop rate, arc voltage and feeding time, the feeding process in the later stage of smelting is optimized to ensure that the melting rate decreases steadily and the shrinkage depth after solidification is reduced.
It improves the yield of zirconium and zirconium alloy ingots, stabilizes riser depth, reduces material loss, lowers production costs, and is suitable for mass industrial production.
Smart Images
Figure CN121874486A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of zirconium and zirconium alloy preparation technology, specifically relating to a feeding method for smelting zirconium and zirconium alloy finished product ingots. Background Technology
[0002] The VAR process for melting finished zirconium and zirconium alloy ingots is divided into three stages: the arc initiation stage, the stabilization melting stage, and the feeding stage. The feeding stage refers to the process of gradually reducing the melting current (melting rate) in the later stage of melting in order to reduce the depth of shrinkage cavities formed during final solidification and reduce the amount of riser removal, so that the molten pool gradually becomes shallower until solidification ends.
[0003] Typically, due to factors such as cooling water temperature, weighing system, and manual intervention, the melting rate during the feeding process varies under the same process conditions, resulting in inconsistent feeding processes for zirconium ingots. This leads to unstable zirconium ingot riser depth, ultimately causing unstable yield, making material feeding production difficult, and increasing production costs.
[0004] Currently, there is very little research in the industry on the feeding process of zirconium ingot smelting. Although the smelting process specifies the feeding requirements for zirconium ingots smelted using the VAR method, it does not divide the feeding process into stages. It fails to recognize that the "front stage" of the feeding process, which accounts for the first 30-40% of the total feeding time, has a significant impact on the riser depth. Furthermore, there is no reasonable description of the feeding time and the reserved feeding weight. Summary of the Invention
[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a feeding method for smelting zirconium and zirconium alloy finished ingots. This method optimizes the feeding process in the later stages of smelting by controlling the smelting current, current decrease rate, arc voltage, feeding time, and feeding allowance during the feeding stage of VAR (Vacuum-Arc) smelting of zirconium and zirconium alloy finished ingots in stages. This ensures a stable decrease in melting rate, gradually shallowing the molten pool, reducing the depth of concentrated shrinkage cavities after solidification, effectively reducing the amount of ingot head removed, improving the ingot yield, and solving the problems of large differences and unstable riser depth in conventional zirconium and zirconium alloy finished ingot feeding processes.
[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a feeding method for melting zirconium and zirconium alloy finished ingots, characterized in that the method specifically comprises: in the later stage of melting zirconium and zirconium alloy finished ingots using the VAR method, namely the feeding stage, the feeding stage is divided into two stages: a "front stage" and a "back stage". In the "front stage", the melting rate is controlled by controlling the rate of decrease of the melting current, and in the "back stage", the melting rate is adjusted by adjusting the arc voltage to ensure that the melting rate is within a reasonable range and decreases steadily, so that the molten pool gradually becomes shallower; at the same time, the feeding time is calculated and the feeding reserve weight is designed to ensure that the weight of the consumable electrode at the end of the feeding is within the specified range.
[0007] The aforementioned feeding method for melting zirconium and zirconium alloy ingots is characterized in that the "preliminary stage" accounts for 30% to 40% of the feeding time, and the "secondary stage" accounts for 60% to 70% of the feeding time. In existing feeding methods, due to unreasonable control of the rate of decrease in melting current, the melting rate often fails to decrease steadily. Based on in-depth research into the feeding process, especially the phenomenon of increased riser depth caused by unstable melting rate decrease in the early stage of feeding, this invention clearly divides the feeding process into stages, precisely defines the time proportions of the "preliminary stage" and "secondary stage," and specifically controls reasonable melting current and decreasing rate to ensure a steady decrease in melting rate in the "preliminary stage" and a reasonable melting rate in the "secondary stage," thus ensuring the smooth progress of the feeding process.
[0008] The above-mentioned feeding method for smelting zirconium and zirconium alloy ingots is characterized in that the "preliminary" process of the feeding stage is as follows: Step 1: At the beginning of feeding, control the melting current to 24kA~35kA, and the inner diameter of the crucible for melting zirconium and zirconium alloy finished ingots to be Ф640mm~Ф920mm; Step 2: In the "preliminary stage" of the feeding phase, control the magnitude and rate of decrease of the smelting current: when the smelting current is 20kA~35kA, the rate of decrease of the smelting current is 2.0kA / min~2.5kA / min; when the smelting current is 10kA~20kA, the rate of decrease of the smelting current is 1.0kA / min~1.5kA / min; when the smelting current is 6kA~10kA, the rate of decrease of the smelting current is 0.1kA / min~0.5kA / min.
[0009] The aforementioned feeding method for melting zirconium and zirconium alloy ingots is characterized in that, in the "later stage" of the feeding phase, the arc voltage is adjusted to 24V~30V, the melting rate is adjusted to 0.2kg / min~1.5kg / min, and the arc stabilizing current is 8A~15A. By adjusting the arc voltage to control the distance between the positive and negative electrodes (i.e., the arc distance) at a reasonable level, combined with adjusting the arc stabilizing current, the arc generated during melting is kept in a "flat" state. This not only maintains the surface temperature of the molten pool, which is beneficial for expanding the molten pool area and improving the surface quality of the ingot, but also facilitates the removal of gaseous impurities. Simultaneously, it allows the remaining self-consuming electrode end face to be flattened until it is completely melted.
[0010] The above-mentioned feeding method for melting zirconium and zirconium alloy ingots is characterized in that, in the "later stage" of the feeding stage, when the melting rate drops below 0.2 kg / min, the arc voltage is increased by 0.5V to 1V. When the melting rate drops too low to below 0.2 kg / min, the arc voltage is increased to ensure that the melting rate gradually decreases during the feeding process.
[0011] The above-mentioned feeding method for smelting zirconium and zirconium alloy finished ingots is characterized in that the calculation formula between the feeding time and the zirconium and zirconium alloy finished ingots is as follows: (1) In formula (1), The feeding time is in minutes; D is the nominal diameter of the ingot in mm.
[0012] The above-mentioned feeding method for melting zirconium and zirconium alloy finished ingots is characterized in that, for zirconium and zirconium alloy finished ingots with a diameter of Ф640mm, the determined feeding allowance weight is 180kg~280kg, and the feeding time is 95min~155min. For zirconium and zirconium alloy finished ingots with a diameter of Ф720mm, the determined feeding allowance is 250kg~350kg, and the feeding time is 120min~180min; For zirconium and zirconium alloy finished ingots with a diameter of Ф820mm, the determined feeding allowance is 300kg~400kg, and the feeding time is 150min~210min; For zirconium and zirconium alloy finished ingots with a diameter of Ф920mm, the determined feeding allowance is 400kg~500kg, and the feeding time is 210min~270min.
[0013] Compared with the prior art, the present invention has the following advantages: 1. This invention clearly divides the late-stage feeding stage of zirconium and zirconium alloy ingots smelted by the VAR method and adopts different adjustment methods. Specifically, by reasonably controlling the smelting current and the rate of current decrease, the melting rate in the "front stage" is ensured to decrease steadily. The melting rate is controlled by reasonably controlling the rate of decrease of the smelting current. Combined with adjusting the arc voltage, the melting rate is adjusted to ensure the melting rate in the "back stage" is stable, maintaining a high temperature on the surface of the molten pool and maintaining a temperature gradient in the longitudinal direction. This is conducive to the liquid metal filling the pores generated by solidification shrinkage, making the molten pool depth gradually shallower. This increases the location of concentrated shrinkage cavities generated after solidification and effectively reduces the amount of ingot head to be removed (the shrinkage cavities must be completely removed), thereby steadily and effectively improving the ingot yield.
[0014] 2. In view of the main influence of the "front stage" on the riser depth in the feeding process of zirconium and zirconium alloy finished ingots smelted by VAR method, the present invention improves the stability of the feeding process and the consistency of the riser depth by limiting the smelting current and the corresponding descent rate at different stages in the "front stage", and further improves the yield of finished ingots.
[0015] 3. While controlling the adjustment of each stage during the feeding stage, this invention determines the feeding time and designs the feeding reserve weight according to the size of the finished ingot, ensuring that the weight of the self-consuming electrode at the end of the feeding stage is compliant and ensuring the smooth implementation of the feeding process.
[0016] 4. This invention optimizes the feeding process of large-size zirconium and zirconium alloy ingots by controlling process parameters such as the magnitude and rate of decrease of melting current, melting rate, voltage, feeding time, and feeding allowance during the feeding process of zirconium and zirconium alloy finished ingots smelted by the VAR method. This increases the stability, flexibility, and operability of the feeding process, steadily reduces the riser depth of the ingot, and improves the yield of the ingot. It is applicable to zirconium and zirconium alloys of the same specification but different grades, and has a guiding and reference role for the feeding process of ingots of other specifications and grades.
[0017] 5. This invention effectively controls the feeding process, reduces the influence of human intervention factors, reduces the riser depth, and improves the stability of the ingot riser depth. This helps to reduce material loss, increase the ingot yield, and reduce production costs. Moreover, the control process is simple, easy to implement, and suitable for mass industrial production.
[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0019] Figure 1 This is a trend graph of the melting rate during the feeding process of the R60702 zirconium ingot in Embodiment 1 of the present invention.
[0020] Figure 2This is a trend graph of the melting rate during the feeding process of the R60702 zirconium ingot in Embodiment 2 of the present invention.
[0021] Figure 3 This is a trend graph of the melting rate curve during the feeding process of the R60702 zirconium ingot in Comparative Example 1 of the present invention.
[0022] Figure 4 This is a trend graph of the melting rate during the feeding process of the R60705 zirconium alloy finished ingot in Example 3 of the present invention.
[0023] Figure 5 This is a trend graph of the melting rate during the feeding process of the R60702 zirconium ingot in Embodiment 4 of the present invention. Detailed Implementation
[0024] Example 1 In this embodiment, during the later stage of melting R60702 zirconium ingots with a diameter of 640mm using the VAR method, i.e. the feeding stage, the feeding time is determined to be 125min by formula (1), and the feeding reserve weight is designed to be 210kg. (1) In formula (1), The feeding time is in minutes; D is the nominal diameter of the ingot in mm. In the VAR melting process, feeding begins when the weight of the consumable electrode reaches the pre-replenishment weight of 210 kg. The feeding stage is divided into two parts: the "front stage" and the "back stage." Figure 1 As shown, the specific process of controlling the magnitude and rate of decrease of the smelting current in the "front stage" and controlling the arc voltage and melting rate in the "rear stage" is as follows: Step 1: Control the melting current to 24kA at the start of the feeding process; Step 2: In the "preliminary stage" of the feeding phase, control the magnitude and rate of decrease of the smelting current as follows: when the smelting current is 20kA~24kA, the rate of decrease is 2.0kA / min; when the smelting current is 10kA~20kA, the rate of decrease is 1.0kA / min; when the smelting current is 6kA~10kA, the rate of decrease is 0.1kA / min. The duration of the "preliminary stage" is 40 minutes, accounting for 30% of the feeding time. Step 3: In the "later stage" of the feeding phase, control the melting current decrease rate to 0.05 kA / min, the arc voltage to 24V~27V, the melting rate to 0.2 kg / min~0.8 kg / min, and the arc stabilization current to 8A~15A; when the melting rate drops below 0.2 kg / min, adjust the arc voltage to increase by 0.5V~1V; the "later stage" lasts for 93 minutes, accounting for 70% of the feeding time.
[0025] In this embodiment, the riser end of the R60702 zirconium ingot was subjected to non-destructive testing using an ultrasonic flaw detector. The results showed that the shrinkage cavity depth at the riser end was 65 mm.
[0026] Example 2 In this embodiment, during the later stage of melting R60702 zirconium ingots with a diameter of 720mm using the VAR method, i.e. the feeding stage, the feeding time is determined to be 135min by formula (1), and the feeding reserve weight is designed to be 280kg. (1) In formula (1), The feeding time is in minutes; D is the nominal diameter of the ingot in mm. In the VAR melting process, feeding begins when the weight of the consumable electrode reaches the pre-reserved weight of 280 kg. The feeding stage is divided into two parts: the "front stage" and the "back stage." Figure 2 As shown, the specific process of controlling the magnitude and rate of decrease of the smelting current in the "front stage" and controlling the arc voltage and melting rate in the "rear stage" is as follows: Step 1: Control the melting current to 29kA at the start of the feeding process; Step 2: In the "preliminary stage" of the feeding phase, the magnitude and rate of decrease of the smelting current are controlled as follows: when the smelting current is 20kA~29kA, the rate of decrease is 2.2kA / min; when the smelting current is 10kA~20kA, the rate of decrease is 1.2kA / min; and when the smelting current is 6kA~10kA, the rate of decrease is 0.2kA / min. The duration of the "preliminary stage" is 47 minutes, accounting for 35% of the feeding time. Step 3: In the "later stage" of the feeding phase, control the melting current decrease rate to 0.05 kA / min, the arc voltage to 25V~28V, the melting rate to 0.4 kg / min~1.0 kg / min, and the arc stabilization current to 8A~15A; when the melting rate drops below 0.2 kg / min, adjust the arc voltage to increase by 0.5V~1V; the "later stage" lasts for 88 minutes, accounting for 65% of the feeding time.
[0027] In this embodiment, the riser end of the R60702 zirconium ingot was subjected to non-destructive testing using an ultrasonic flaw detector. The results showed that the shrinkage cavity depth at the riser end was 80 mm.
[0028] Comparative Example 1 This comparative example is based on the later stage of the VAR method for melting Φ720mm R60702 zirconium ingots, i.e. the feeding stage, with a designed feeding allowance of 280kg. During the VAR melting process, feeding begins when the weight of the consumable electrode reaches the pre-replenishment weight of 280 kg. Figure 3As shown, the specific process is as follows: Step 1: Control the melting current to 29kA at the start of the feeding process; Step 2: During the feeding stage, the magnitude and rate of decrease of the smelting current are controlled as follows: when the smelting current is 20kA~29kA, the rate of decrease of the smelting current is 2.0kA / min; when the smelting current is 10kA~20kA, the rate of decrease of the smelting current is 0.8kA / min; when the smelting current is 6kA~10kA, the rate of decrease of the smelting current is 0.6kA / min; when the smelting current is 4kA~6kA, the rate of decrease of the smelting current is 0.1kA / min; and the feeding time is 110min.
[0029] The riser end of the R60702 zirconium ingot in this comparative example was subjected to non-destructive testing using an ultrasonic flaw detector. The results showed that the shrinkage cavity depth at the riser end was 180 mm.
[0030] Comparing Comparative Example 2 with Example 2 of the present invention, it can be seen that since the feeding process in Comparative Example 2 did not adopt "segmented" control, the shrinkage cavity depth at the riser end of the ingot was relatively large. This indicates that the present invention controls the feeding process of VAR melting in stages to ensure a steady decrease in melting rate, making the molten pool gradually shallower, reducing the shrinkage cavity depth at the riser end, and thus effectively reducing the amount of material removed from the head of the finished ingot.
[0031] Example 3 In this embodiment, during the later stage of melting R60705 zirconium alloy finished ingots with a diameter of 820mm using the VAR method, i.e. the feeding stage, the feeding time is determined to be 177min by formula (1), and the feeding reserve weight is designed to be 340kg. (1) In formula (1), The feeding time is in minutes; D is the nominal diameter of the ingot in mm. In the VAR melting process, feeding begins when the weight of the consumable electrode reaches the pre-replenishment weight of 210 kg. The feeding stage is divided into two parts: the "front stage" and the "back stage." Figure 4 As shown, the specific process of controlling the magnitude and rate of decrease of the smelting current in the "front stage" and controlling the arc voltage and melting rate in the "rear stage" is as follows: Step 1: Control the melting current to 32kA at the start of the feeding process; Step 2: In the "preliminary stage" of the feeding phase, the magnitude and rate of decrease of the smelting current are controlled as follows: when the smelting current is 20kA~32kA, the rate of decrease is 2.3kA / min; when the smelting current is 10kA~20kA, the rate of decrease is 1.4kA / min; and when the smelting current is 6kA~10kA, the rate of decrease is 0.3kA / min. The duration of this "preliminary stage" is 66 minutes, accounting for 37% of the feeding time. Step 3: In the "later stage" of the feeding phase, control the melting current decrease rate to 0.05 kA / min, the arc voltage to 25 V~29 V, the melting rate to 0.4 kg / min~1.2 kg / min, and the arc stabilization current to 8 A~15 A; when the melting rate drops below 0.2 kg / min, adjust the arc voltage to increase by 0.5 V~1 V; the "later stage" lasts for 112 min, accounting for 63% of the feeding time.
[0032] In this embodiment, the riser end of the R60705 zirconium alloy finished ingot was subjected to non-destructive testing using an ultrasonic flaw detector. The results showed that the shrinkage cavity depth at the riser end was 100 mm.
[0033] Example 4 In this embodiment, during the later stage of melting R60702 zirconium ingots with a diameter of 920mm using the VAR method, i.e. the feeding stage, the feeding time is determined to be 218min by formula (1), and the feeding reserve weight is designed to be 420kg. (1) In formula (1), The feeding time is in minutes; D is the nominal diameter of the ingot in mm. In the VAR melting process, feeding begins when the weight of the consumable electrode reaches the pre-replenishment weight of 210 kg. The feeding stage is divided into two parts: the "front stage" and the "back stage." Figure 2 As shown, the specific process of controlling the magnitude and rate of decrease of the smelting current in the "front stage" and controlling the arc voltage and melting rate in the "rear stage" is as follows: Step 1: Control the melting current to 35kA at the start of the feeding process; Step 2: In the "preliminary stage" of the feeding phase, control the magnitude and rate of decrease of the smelting current as follows: when the smelting current is 20kA~35kA, the rate of decrease is 2.5kA / min; when the smelting current is 10kA~20kA, the rate of decrease is 1.5kA / min; when the smelting current is 6kA~10kA, the rate of decrease is 0.5kA / min. The duration of the "preliminary stage" is 90 minutes, accounting for 40% of the feeding time. Step 3: In the "later stage" of the feeding phase, control the melting current decrease rate to 0.05 kA / min, the arc voltage to 26V~30V, the melting rate to 0.3 kg / min~0.5 kg / min, and the arc stabilization current to 8A~15A; when the melting rate drops below 0.2 kg / min, adjust the arc voltage to increase by 0.5V~1V; the "later stage" lasts for 135 minutes, accounting for 60% of the feeding time.
[0034] In this embodiment, the riser end of the R60702 zirconium ingot was subjected to non-destructive testing using an ultrasonic flaw detector. The results showed that the shrinkage cavity depth at the riser end was 110 mm.
[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.
Claims
1. A feeding method for smelting zirconium and zirconium alloy ingots, characterized in that, The method is as follows: In the later stage of smelting zirconium and zirconium alloy ingots using the VAR method, namely the feeding stage, the feeding stage is divided into two stages: "front stage" and "back stage". In the "front stage", the melting rate is controlled by controlling the rate of decrease of the smelting current. In the "back stage", the melting rate is adjusted by adjusting the arc voltage to ensure that the melting rate is within a reasonable range and decreases steadily, so that the molten pool gradually becomes shallower. At the same time, the feeding time is calculated and the feeding reserve weight is designed to ensure that the weight of the self-consumable electrode at the end of the feeding is within the specified range.
2. The feeding compensation method for smelting zirconium and zirconium alloy ingots according to claim 1, characterized in that, The "front segment" accounts for 30% to 40% of the compensation time, and the "back segment" accounts for 60% to 70% of the compensation time.
3. The feeding compensation method for smelting zirconium and zirconium alloy finished product ingots according to claim 1, characterized in that, The "preliminary" process of the compensation stage is as follows: Step 1: At the beginning of feeding, control the melting current to 24kA~35kA, and the inner diameter of the crucible for melting zirconium and zirconium alloy finished ingots to be Ф640mm~Ф920mm; Step 2: In the "preliminary stage" of the feeding phase, control the magnitude and rate of decrease of the smelting current: when the smelting current is 20kA~35kA, the rate of decrease of the smelting current is 2.0kA / min~2.5kA / min; when the smelting current is 10kA~20kA, the rate of decrease of the smelting current is 1.0kA / min~1.5kA / min; when the smelting current is 6kA~10kA, the rate of decrease of the smelting current is 0.1kA / min~0.5kA / min.
4. The feeding compensation method for smelting zirconium and zirconium alloy finished product ingots according to claim 1, characterized in that, During the "later stage" of the feeding phase, the arc voltage is adjusted to 24V~30V, the melting rate is adjusted to 0.2kg / min~1.5kg / min, and the arc stabilizing current is 8A~15A.
5. The feeding compensation method for smelting zirconium and zirconium alloy finished product ingots according to claim 1, characterized in that, In the "later stage" of the feeding phase, when the melting rate drops below 0.2 kg / min, the arc voltage is increased by 0.5V to 1V.
6. The feeding compensation method for smelting zirconium and zirconium alloy finished product ingots according to claim 1, characterized in that, The formula for calculating the feeding time and the finished zirconium and zirconium alloy ingots is as follows: （1） In formula (1), The feeding time is in minutes; D is the nominal diameter of the ingot in mm.
7. The feeding compensation method for smelting zirconium and zirconium alloy ingots according to claim 6, characterized in that, For zirconium and zirconium alloy finished ingots with a diameter of Ф640mm, the determined feeding allowance is 180kg~280kg, and the feeding time is 95min~155min; For zirconium and zirconium alloy finished ingots with a diameter of Ф720mm, the determined feeding allowance is 250kg~350kg, and the feeding time is 120min~180min; For zirconium and zirconium alloy finished ingots with a diameter of Ф820mm, the determined feeding allowance is 300kg~400kg, and the feeding time is 150min~210min; For zirconium and zirconium alloy finished ingots with a diameter of Ф920mm, the determined feeding allowance is 400kg~500kg, and the feeding time is 210min~270min.