Verification method for impurity removal effect of electron beam cold hearth melting

Abstract

The invention relates to the technical field of alloy smelting, and provides a verification method for the inclusion removal effect of electron beam cold hearth smelting, and the verification method is used for quantitatively evaluating the inclusion removal effect and comprises the steps that S1, a base material and an inclusion material are selected; s2, inclusion placement; s3, electron beam cold bed smelting; s4, ingot casting treatment; and S5, inclusion detection and evaluation are conducted, specifically, radiographic inspection is conducted on the whole smelted and machined material one by one, the number of detected inclusion defects is obtained, and the difference value of the number of the detected inclusion defects and the number of the placed inclusions and the percentage of the number of the placed inclusions are the inclusion removal proportion of the electron beam cooling bed under the corresponding smelting technology. The method can be used for evaluating the inclusion removal effect under the electron beam cold hearth smelting furnace and smelting process technology, can quantitatively reflect the technical capability and quality level of different smelting furnaces and smelting processes, and provides powerful help for the aspects of metal material smelting furnace selection, electron beam cold hearth smelting furnace maintenance judgment, smelting process improvement and promotion and the like.

Description

Technical Field

[0001] The invention relates to the technical field of alloy smelting, and in particular to a method for verifying the effect of electron beam cold bed smelting in removing impurities. Background Art

[0002] Electron beam cold hearth furnace melting (EBCHM, EB melting for short) is a vacuum melting equipment that uses the heat generated by electron beam bombardment to melt and purify high-temperature refractory metals under vacuum conditions. It has the characteristics of high temperature, high vacuum, good raw material applicability, and good inclusion removal. In the classification of electron beam cold hearth melting furnaces, according to the structure of the cooling bed, it is divided into straight cooling bed, L-type cooling bed, and C-type cooling bed. According to the structure of the electron gun, it is divided into hot cathode electron gun furnace and cold cathode electron gun furnace. In addition, there are distinctions in feeding methods and crucible ingot shapes.

[0003] The electron beam cooling furnace is equipped with a water-cooled copper bed. The raw materials are melted in the cooling bed and flow to the water-cooled copper crucible. Depending on the position of the electron gun and the structure of the cooling bed, the process design can be separated into different positions such as melting, refining and solidification. Through the electron beam gun scanning the raw materials and the solidified shell, the raw materials melt on the surface of the solidified shell to form a melt. Under the flexible electron beam scanning process in different areas, the melt flows through various areas of the cooling bed and enters the crucible for crystallization. The high superheat and sufficient liquid maintenance time generated by electron beam irradiation cause the impurity elements in the raw materials to sink or float in the form of high and low density inclusions, thereby separating the melt to obtain high-purity, high-uniformity high-quality metal ingots. Therefore, electron beam cold bed melting is widely used in the preparation of rare and refractory metals such as titanium, zirconium, tantalum, and niobium, and is also used for the purification and preparation of high-purity metals. Among the many metals melted in electron beam cold bed melting, titanium is the most widely used one. The production and processing control of titanium smelting is difficult, and it is easy to introduce high and low density inclusions, especially the recycling process of scraps. In view of the fact that electron beam cold bed melting can effectively remove inclusions compared with other melting methods, the industry uses it more for the recycling of titanium residues. In addition, it can also be applied to fields with high requirements for product quality, such as aerospace. Foreign countries use this melting method as a treatment process to reduce the risk of raw material inclusions.

[0004] There are many factors that affect the removal of impurities during smelting, such as the structure of the electron beam cooling hearth furnace, specific production conditions, specific smelting parameters, etc. Under the influence of many factors, the effect of electron beam cooling hearth smelting in removing impurities and how to obtain better quality smelting ingots under different smelting processes are all problems that operators need to face. There is no analytical verification method for the removal effect of inclusions in the prior art. Summary of the invention

[0005] In view of this, the present invention aims to propose a verification method for the removal of inclusions by electron beam cold hearth melting, which is used to compare and analyze the quality of ingots after impurities are removed under different factors, and to provide an effective means for metal material processing equipment selection, process formulation and optimization.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A verification method for electron beam cold bed melting to remove inclusions is used to quantitatively evaluate the inclusion removal effect. The verification method comprises the following steps:

[0008] S1. Selection of matrix material, matrix small sample material and inclusion material;

[0009] S2. Inclusion placement;

[0010] S3. Electron beam cold bed melting;

[0011] S4. Ingot processing;

[0012] S5. Inclusion detection and evaluation,

[0013] The smelted and processed materials are subjected to radiographic inspection area by area to obtain the number of detected inclusion defects. The difference between the number of detected inclusion defects and the number of placed inclusions and the percentage of the number of placed inclusions are the inclusion removal ratio of the electron beam cooling bed under the corresponding smelting process.

[0014] Furthermore, in step S1, the matrix material is selected to have a dense morphology and is tested to have no internal inclusion defects, the matrix small sample material comes from the matrix material, and the inclusion material is selected from at least one of titanium nitride, cemented carbide cutting bits, tungsten needles, and casting mold materials.

[0015] Further, step S2 includes:

[0016] S21. The selected inclusion material is crushed and screened to obtain inclusion particles having a particle size range of 3-15 mm;

[0017] S22. Processing holes on the base small sample material, and cleaning the base small sample after the drilling is completed;

[0018] S23. Place inclusion particles into the holes and use the same material as the matrix small sample to seal and weld them to achieve preliminary fusion of the inclusions and the matrix small sample.

[0019] Furthermore, in step S21, for inclusions of the same type, the particle sizes are kept within the same range, and the range fluctuation is controlled within 5 mm.

[0020] Further, step S3 includes:

[0021] S31. Evenly place a small sample of the matrix containing the inclusion material into the matrix material so that the inclusion enters the melting zone at a relatively uniform speed;

[0022] S32. The electron beam cold hearth melting process adopts the conventional melting process of the electron beam cold hearth furnace to be verified, or the electron beam cold hearth melting process to be verified;

[0023] S33. After the inclusion material is melted, an ingot is obtained, and the melt in the cooling bed molten pool is emptied into a crucible, and subsequent inclusion detection is performed together with the ingot.

[0024] Furthermore, in step S31, no less than 10 inclusions are placed in every 100 kg of the base material, and the total number of inclusions is greater than 50.

[0025] Furthermore, in step S31, different types of inclusion materials are placed separately and melted in sections.

[0026] Furthermore, the inclusion materials include both high-density inclusions and low-density inclusions. The titanium nitride and casting mold materials are low-density inclusions, the number of which is not less than 25, and the cemented carbide cutting bits and tungsten needles are high-density inclusions, the number of which is not less than 25.

[0027] Furthermore, in step S5, the inclusion removal ratio percentage is excellent when it is above 90%, good when it is between 70% and 90%, fair when it is between 50% and 70%, and poor when it is below 50%.

[0028] Compared with the prior art, the verification method for the removal of inclusions by electron beam cold hearth melting described in the present invention has the following advantages: it can be used to evaluate the removal of inclusions under electron beam cold hearth melting furnaces and melting process technologies, and can quantitatively reflect the technical capabilities and quality levels of different melting furnaces and melting processes, and provide powerful assistance for the selection of metal material melting furnaces, maintenance judgment of electron beam cold hearth melting furnaces, and improvement of electron beam cold hearth melting processes. It makes up for the lack of verification and evaluation methods for electron beam melting inclusion removal in the prior art. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with specific embodiments. It should be noted that the data in the following experimental examples are obtained by the inventor through a large number of experiments. Due to space limitations, only a part of them is shown in the specification, and those of ordinary skill in the art can understand and implement the present invention under these data. These embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these changes or modifications also fall within the scope protected by the present application.

[0030] A verification method for the inclusion removal effect of electron beam cold bed melting of the present invention is used for quantitatively evaluating the inclusion removal effect, and comprises the following steps:

[0031] S1. Selection of matrix material, matrix small sample material and inclusion material;

[0032] Specifically, the matrix material is the material to be smelted, and the electron beam cooling furnace type, the smelting material commonly used in the smelting process, or the material to be verified is selected. The matrix material should have a dense shape and be free of internal inclusion defects after inspection such as radiographic testing.

[0033] The matrix small sample material is from the matrix material, preferably in a regular shape such as a plate or a rod. Further, the matrix small sample material is selected or processed into a plate with a thickness of 20-30mm, a width of 40-70mm, and a length of 400-2000mm, or a rod with a diameter of 25-40mm and a length of 400-2000mm.

[0034] The inclusion material is selected from the types that are common in the matrix material and have the risk of introduction, including at least one of titanium nitride (type A), carbide cutting bit (type B), tungsten needle (type C), and casting mold material (type D). In order to improve the accuracy of the inclusion effect, the inclusion material is selected from at least three of the above four types, and covers both high-density inclusions and low-density inclusions. More specifically, the inclusion material is granular, which is convenient for inclusion placement, and the inclusion is pre-introduced into the matrix small sample material.

[0035] The preparation method of titanium nitride is to use grade 0-2 sponge titanium with a particle size of 1-3mm, and heat it on a mesh belt furnace with nitrogen. The heating temperature is 750-900℃, the mesh belt transmission speed is 0.2-1.2mm / s, and the time of passing through the heating zone is 45-70min. The scraper rotating above the mesh belt makes the height of the sponge titanium particles not exceed 5mm. The cemented carbide cutting head is made of common WC material on the market. The tungsten needle is selected from the tungsten needle used in the common argon arc welding gun, and is cut and processed into uniform particles of 2-5mm in size, with a clean and pollution-free surface. The casting mold materials include graphite, zirconium oxide, yttrium oxide, etc., and mechanical crushing and screening are used to obtain uniform particles of 2-5mm in size.

[0036] S2. Inclusion placement;

[0037] S21. The selected inclusion material is crushed and screened to obtain inclusion particles with a particle size range of 3-15 mm. For the same type of inclusions, the particle size is kept in the same range, and the range fluctuation is controlled within 5 mm;

[0038] S22. Processing holes on the small sample material of the base, and cleaning the small sample of the base after the holes are completed to avoid the introduction of impurities;

[0039] Specifically, the interval between the holes is 30-150mm. The interval between the holes will affect the number of inclusions entering the smelting per unit time, and the interval between the holes is determined according to the smelting furnace type and process. For example, the interval between the holes for a straight small cooling bed EB furnace can be 80-150mm, and the interval between the holes for a C-type and L-type large cooling bed EB furnace can be 30-100mm.

[0040] The processed holes are selected from any one of drilling blind holes and cutting through holes; in the present invention, the size of the processed holes is not specifically limited, as long as the inclusion particles can be placed in the holes.

[0041] S23. Place inclusion particles into the holes, and use the same material as the matrix small sample to seal and weld them together, so as to achieve preliminary fusion of the inclusions and the matrix small sample;

[0042] When welding, a welding method with a large penetration depth, such as plasma welding, is used to weld the inclusion placement position. The welding current is 650-750A, the welding time is 20-35s, and the penetration depth reaches more than 10mm, achieving preliminary fusion of the inclusion and the matrix small sample material.

[0043] S3. Electron beam cold bed melting;

[0044] S31. Evenly place a small sample of the matrix containing the inclusion material into the matrix material, so that the inclusions enter the melting zone at a relatively uniform speed, that is, the number of inclusions entering the melting zone in consecutive intervals is basically the same;

[0045] Specifically, the matrix sample containing inclusions placed in the matrix material is determined according to the structure and feeding method of the electron beam cooling furnace. In principle, no less than 10 inclusions are placed in every 100kg of matrix material, and the total number of inclusions is greater than 50. The accuracy of the detection is ensured by a higher number of inclusions. Different types of inclusion materials are placed separately and melted in sections. Among them, the number of low-density inclusions (type A, type D) is not less than 25, and the number of high-density inclusions (type B, type C) is not less than 25.

[0046] The inclusion material of the present application is first welded into the holes in the matrix small sample material to achieve preliminary fusion of the inclusion and the matrix small sample, and then the inclusion is placed in the matrix material in the form of the matrix small sample material containing the inclusion. This not only makes the inclusion distribution uniform, but also is closer to the actual inclusion state, thereby improving the accuracy of verification.

[0047] S32. The electron beam cold hearth melting process adopts the conventional melting process of the electron beam cold hearth furnace to be verified, or the electron beam cold hearth melting process to be verified;

[0048] S33. After the inclusion material is melted, an ingot is obtained, and the melt in the cooling bed molten pool is emptied into a crucible, and subsequent inclusion detection is performed together with the ingot.

[0049] S4. Ingot processing;

[0050] Specifically, the ingot segments containing the smelted inclusion materials and the ingot segments of the finished emptying parts are cut off, and processed into a shape and thickness size suitable for radiographic inspection by any method of slitting, heating forging or rolling, and surface treatment is performed;

[0051] S5. Inclusion detection and evaluation.

[0052] The whole material after smelting and processing is subjected to radiographic inspection area by area to obtain the number of detected inclusion defects. The difference between the number of detected inclusion defects and the number of placed inclusions and the percentage of the number of placed inclusions are the inclusion removal ratio of the electron beam cooling bed under the corresponding smelting process. The inclusion removal ratio percentage is defined as above 90% as excellent, 70%-90% as good, 50%-70% as fair, and below 50% as poor. At the same time, based on the number of defects of high-density inclusions and low-density inclusions detected, the high-density inclusion removal ratio and the low-density inclusion removal ratio are calculated to evaluate the removal effects of high-density inclusions and low-density inclusions, respectively.

[0053] The difference between the number of detected inclusion defects of a certain type and the number of placed inclusions of this type and the percentage of the number of placed inclusions of this type are the removal ratio of this type of inclusions in the electron beam cooling hearth furnace under the corresponding smelting process.

[0054] The verification method of the electron beam cold hearth melting effect of the present invention can be used to evaluate the removal effect of inclusions under the electron beam cold hearth melting furnace and melting process technology, and can quantitatively reflect the technical capabilities and quality levels of different melting furnaces and melting processes, and concretize and standardize the ability of the electron beam cold hearth melting furnace to remove inclusions, and provide powerful assistance for the selection of metal material melting furnaces, the maintenance judgment of electron beam cold hearth melting furnaces, and the improvement and promotion of electron beam cold hearth melting processes. It makes up for the lack of verification and evaluation methods for electron beam melting inclusion removal in the prior art. At the same time, the present invention also helps to improve the quality of electron beam melting ingots, and promotes the development and application of short-process electron beam melting ingots. The present invention has the characteristics of clear and definite verification process, standardized implementation, reliable verification effect, and a wide range of applications.

[0055] Example 1

[0056] S1. Selection of matrix material, matrix small sample material and inclusion material;

[0057] Pure titanium TA1 material is selected as the base material, and the raw material form is 0.5-25mm plate scraps, weighing 590kg. After X-ray flaw detection, there are no inclusion defects inside.

[0058] A plate with a thickness of 20-25 mm, a width of 40-50 mm, and a length of 500-1000 mm is selected from the selected matrix materials as a small matrix sample material to carry inclusions and add to the raw materials to be smelted.

[0059] Titanium nitride (type A), carbide cutting bits (type B) and tungsten needles (type C) were selected as inclusion materials. Titanium nitride was prepared by heating grade 0 titanium sponge with a particle size of 1-3 mm at 750°C in a mesh belt furnace with nitrogen. The mesh belt transmission speed was 0.5 mm / s, the time of passing through the heating zone was 50 min, the height of the titanium sponge particles did not exceed 5 mm, and the N content was detected to be 2.8%. The carbide cutting bits and tungsten needles were cut into uniform particles of 5 mm in size, and the surface was pickled.

[0060] S2. Inclusion placement;

[0061] Holes were cut and processed on the small sample material of the base material with a hole spacing of 30 mm, and then pickled and dried.

[0062] Place the inclusion material into the hole, put two inclusions in each hole along the feeding direction, put titanium nitride inclusions first, then carbide and tungsten needle inclusions, and use TA1 material for plugging. Use plasma welding to weld the inserted position so that the inclusion material and the matrix small sample can be initially fused. The number of titanium nitride inclusions placed is 80, and the number of carbide inclusions placed is 40.

[0063] S3. Electron beam cold bed melting;

[0064] The small sample of matrix material containing inclusions is evenly placed into the matrix material unit material box, with its length direction consistent with the feeding direction of the material box, so that the inclusions enter the melting zone at a relatively uniform speed.

[0065] It is intended to verify the effect of electron beam cold bed melting process in removing inclusions at high melting rate. The melting rate is 1200-1300Kg / h and the electron beam pattern is adjusted accordingly.

[0066] After the matrix material containing inclusions is melted, it enters the emptying step to empty the melt in the cooling bed into the crucible.

[0067] S4. Ingot processing;

[0068] The ingot segments containing the melted inclusion materials and the ingot segments at the end of the emptying part were cut off, the cut size was 192×1280×670mm, and hot-rolled into 5 plates of 50×1290×515mm, and the surface was polished.

[0069] S5. Inclusion detection and evaluation.

[0070] The plate obtained in step S4 was subjected to radiographic inspection piece by piece and area by area, and a total of 9 low-density inclusion defects and 5 high-density inclusion defects were detected. Accordingly, the inclusion removal ratio of the electron beam cooling hearth furnace under the high-speed smelting process was 88%, and the inclusion removal effect was good.

[0071] Example 2

[0072] S1. Selection of matrix material, matrix small sample material and inclusion material;

[0073] TC4 titanium alloy material is selected as the matrix material, and the raw material form is the frame and runner scraps of the casting, with a weight of 515kg. After X-ray flaw detection, there is no inclusion defect inside. Graphite is selected as the inclusion material.

[0074] Among the selected matrix materials, a rod with a diameter of 30 mm and a length of 500-8000 mm is selected as a small matrix sample to carry inclusions and add to the raw materials to be smelted.

[0075] The inclusion materials include carbide cutting heads (type B), tungsten needles (type C), and graphite (type D). Carbide cutting heads and tungsten needles are cut into uniform particles of 4 mm in size and pickled on the surface. Graphite is crushed and screened to select particles with a particle size of 3-5 mm.

[0076] S2. Inclusion placement;

[0077] Holes were cut and processed on the small sample material of the base material with a hole spacing of 50 mm, and then pickled and dried.

[0078] Place the inclusion material into the processed hole, three per hole along the feeding direction, first place the cemented carbide and tungsten needle inclusions, and then place the graphite inclusions. Use TC4 material for plugging, and use plasma welding to weld the insertion position, so that the inclusion material and the matrix small sample can be initially fused. Specifically, 100 graphite inclusions, 20 cemented carbide inclusions, and 20 tungsten needle inclusions are placed.

[0079] S3. Electron beam cold bed melting;

[0080] The small matrix sample containing the inclusion material is evenly placed in the matrix material unit material box, with its length direction consistent with the feeding direction of the material box, so that the inclusions enter the melting zone at a relatively uniform speed.

[0081] It is intended to verify the inclusion removal effect of titanium alloy under the conventional electron beam cold bed melting process. The conventional electron beam cold bed melting process can be set by the operator according to the empirical value. Specifically, the current of the electron beam cold bed melting process is 7-10A, and the scanning time is 50-800 milliseconds.

[0082] After the matrix material containing inclusions is melted, it enters the emptying step to empty the melt in the cooling bed into the crucible.

[0083] S4. Ingot processing;

[0084] The ingot segments containing the melted inclusion materials and the ingot segments at the end of the emptying part were cut off, the cut size was 191×1080×658mm, and hot-rolled into 4 plates of 50×1090×606mm, and the surface was polished.

[0085] S5. Inclusion detection and evaluation.

[0086] The plate obtained in step S4 was subjected to radiographic inspection piece by piece and area by area, and a total of 10 low-density inclusion defects and 0 high-density inclusion defects were detected. Accordingly, the inclusion removal ratio of the electron beam cooling furnace under conventional smelting process was 93%, and the inclusion removal effect was excellent.

[0087] In Example 1-2, the verification method of the electron beam cold hearth melting of the present invention is illustrated by taking titanium alloy as an example. The present invention is not only applicable to the electron beam cold hearth melting of titanium and titanium alloys, but also applicable to the evaluation and verification of the inclusion removal effect in the electron beam melting of refractory metals such as zirconium, nickel, and tungsten, and provides an analytical verification method for the degree of inclusion removal, which is conducive to clarifying the effect of metal melting to remove inclusions under different electron beam cold hearth melting furnaces or different production conditions, and exploring how to obtain better quality electron beam cold hearth melting ingots under different melting processes.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for verifying the effect of electron beam cold bed melting on removing inclusions, characterized in that: For quantitative evaluation of inclusion removal effect, the verification method comprises the following steps: S1. Selection of matrix material, matrix small sample material and inclusion material; S2. Inclusion placement; S3. Electron beam cold bed melting; S4. Ingot processing; S5. Inclusion detection and evaluation, The smelted and processed materials are subjected to radiographic inspection area by area to obtain the number of detected inclusion defects. The difference between the number of detected inclusion defects and the number of placed inclusions and the percentage of the number of placed inclusions are the inclusion removal ratio of the electron beam cooling bed under the corresponding smelting process.

2. The method for verifying the effect of electron beam cold hearth melting on removing inclusions according to claim 1, characterized in that: In step S1, the matrix material is selected to have a dense morphology and is tested to have no internal inclusion defects. The matrix small sample material comes from the matrix material, and the inclusion material is selected from at least one of titanium nitride, cemented carbide cutting bits, tungsten needles, and casting mold materials.

3. The method for verifying the effect of electron beam cold hearth melting in removing inclusions according to claim 1, characterized in that: Step S2 includes: S21. The selected inclusion material is crushed and screened to obtain inclusion particles having a particle size range of 3-15 mm; S22. Processing holes on the base small sample material, and cleaning the base small sample after the drilling is completed; S23. Place inclusion particles into the holes and use the same material as the matrix small sample to seal and weld them to achieve preliminary fusion of the inclusions and the matrix small sample.

4. The method for verifying the effect of electron beam cold hearth melting on removing inclusions according to claim 3, characterized in that: In step S21, for the same type of inclusions, the particle size is kept within the same range, and the range fluctuation is controlled at 5 mm.

5. The method for verifying the effect of electron beam cold hearth melting on removing inclusions according to claim 1, characterized in that: Step S3 includes: S31. Evenly place a small sample of the matrix containing the inclusion material into the matrix material so that the inclusion enters the melting zone at a relatively uniform speed; S32. The electron beam cold hearth melting process adopts the conventional melting process of the electron beam cold hearth furnace to be verified, or the electron beam cold hearth melting process to be verified; S33. After the inclusion material is melted, an ingot is obtained, and the melt in the cooling bed molten pool is emptied into a crucible, and subsequent inclusion detection is performed together with the ingot.

6. The method for verifying the effect of electron beam cold hearth melting on removing inclusions according to claim 5, characterized in that: In step S31, no less than 10 inclusions are placed in every 100 kg of the base material, and the total number of inclusions is greater than 50.

7. The method for verifying the effect of electron beam cold hearth melting on removing inclusions according to claim 5, characterized in that: In step S31, different types of inclusion materials are placed separately and melted in sections.

8. The method for verifying the effect of electron beam cold hearth melting in removing inclusions according to claim 2, characterized in that: The inclusion materials include both high-density inclusions and low-density inclusions. The titanium nitride and casting mold materials are low-density inclusions, the number of which is not less than 25. The cemented carbide cutting bits and tungsten needles are high-density inclusions, the number of which is not less than 25.

9. The method for verifying the effect of electron beam cold hearth melting on removing inclusions according to claim 1, characterized in that: In step S5, the inclusion removal ratio percentage is excellent when it is above 90%, good when it is between 70% and 90%, fair when it is between 50% and 70%, and poor when it is below 50%.