CN112746176B

CN112746176B - Method for controlling trace element distribution in ESR cast ingot and application thereof

Info

Publication number: CN112746176B
Application number: CN202011591637.4A
Authority: CN
Inventors: 吕亮; 王佳佳; 赵艳梅; 李名言
Original assignee: China Steel Precision Materials Co ltd
Current assignee: China Steel Precision Materials Co ltd
Priority date: 2020-12-29
Filing date: 2020-12-29
Publication date: 2024-03-22
Anticipated expiration: 2040-12-29
Also published as: CN112746176A

Abstract

The invention discloses a method for controlling trace element distribution in ESR cast ingot, which uses blanks with different components as electrode ingot, and performs ESR refining after combination to control trace element distribution in length direction of easy-to-burn trace elements in steel or alloy, so as to reduce variation degree of integral components and produce finished cast ingot with uniform trace element distribution.

Description

Method for controlling trace element distribution in ESR cast ingot and application thereof

Technical Field

The invention belongs to the technical field of metal smelting, and particularly relates to a method for controlling trace element distribution in ESR cast ingots and application thereof.

Background

Vacuum induction melting is essentially the process of melting metal by passing a current under vacuum through the heat generated by an induction coil. The principle is that the vacuum induction smelting furnace is a complete set of vacuum smelting equipment for smelting metal by utilizing electromagnetic induction to generate vortex in a metal conductor to heat furnace burden under the vacuum condition. It is suitable for the production of nickel base alloy, special steel, precise alloy, high temperature alloy, nonferrous metal and their alloy in vacuum or protecting atmosphere. Can also be used for smelting and casting rare earth metals and hydrogen storage materials. Noteworthy are: (1) the furnace cleaning process must enable the crucible to be fully sintered and moisture to be discharged completely, otherwise, the vacuum degree in the later steelmaking stage is not enough and the structure of the cast ingot is affected. (2) The alloying elements must be added in order and after sufficient alloying, other alloying elements are added. (3) The flow rate of molten metal is uniform during casting, so that defects are prevented.

Electroslag remelting is essentially a special metallurgical process in which a metal or alloy is remelted and refined in a water-cooled crystallizer by the resistive heat generated as current passes through the slag and subsequently solidified into an ingot. The working principle is shown in figure 1, specifically, one end of a metal consumable electrode which is produced by vacuum induction smelting and is connected with a power supply is immersed in molten slag to melt the end of the electrode (a large amount of heat is generated when alternating current passes through a high-resistance slag bath), and molten metal drops generated by melting pass through the slag bath to drop into a metal melting pool, and then the molten metal drops are continuously cooled by a water-cooled crystallizer and are condensed into ingots from bottom to top.

The low-activation ferrite/martensite steel (RAFM) has the advantages of low irradiation swelling and thermal expansion coefficient, high thermal conductivity and other excellent thermophysical and mechanical properties, and relatively mature technical basis. Respective RAFM steels such as F82H alloy and JLF alloy in Japan, european EUROFER 97 alloy, and U.S. 9Cr-2WVTa alloy are currently being developed and studied in various countries of the world.

The strengthening and impurity removing effects of each alloy element are fully utilized, the comprehensive performance of the alloy is effectively improved, the content of Ta is properly improved, a large amount of dispersed carbide can be produced by adding the Ta element into steel, grains are refined, and the plasticity and toughness of the material are improved. However, tantalum metal has high melting point, high affinity with oxygen and very severe smelting conditions and modes, and is easy to cause uneven components and burning loss, and chemical reactions of elements such as Ta (chemical equilibrium formula is as follows) at high temperature:

4Ta+5O ₂ ＝2Ta ₂ O ₅

4Al+3O ₂ ＝2Al ₂ O ₃

6Ta+5Al ₂ O ₃ ＝2Ta ₂ O ₅ +10Al

the integral CLAM alloy cast ingot produced by electric furnace or VIM smelting is easy to oxidize in high temperature process by adding Ta element into ingredients in ESR refining process, becomes smelting slag, forms burning loss of Ta solute, and is more serious especially at the bottom of the cast ingot. For example, ta is added in an amount of 0.15% during vacuum induction melting, and the amount of solid solution remaining in the blank is generally less than 0.5% by melting process such as ESR, so that the effect of improving the processing properties cannot be exerted. Because the metal raw materials such as Ta and the like are high in price, the problem that the derivative cost is increased due to the fact that the addition amount is greatly increased, and the burning loss of the ingot near the bottom is serious, the composition difference of the upper part and the lower part of the ingot is overlarge, and the composition requirement of subsequent products is not met.

The nickel-chromium (Ni-Cr) heat-resistant alloy has excellent high-temperature oxidation resistance, and is used as a structural and component material, wherein the most typical application is 80Ni-20Cr, namely a coil or heating wire for heating, and the alias is called Nichrome (Ni can be used except 19-21% Cr and 0.75-1.6% Si according to the UNS N06003 specification in ASTM B344); the high corrosion resistance of Nichrome makes it useful in the production of mechanical parts and aerospace applications. In addition, the Ni-Cr film has higher resistivity, low temperature resistivity, and excellent anti-sticking property; ni-Cr alloy targets with different composition ratios are widely used in sputtering thin films, microelectronic components, flat panel displays and optical storage media materials.

However, 80Ni-20Cr alloy has a problem of poor ductility in reheat working, forging or rolling at a temperature lower than 1050 ℃ and the product is prone to cracking as shown in FIG. 2.

Therefore, aiming at the problem that the 80Ni-20Cr alloy is not easy to thermally process, the alloy design adjustment of trace element Ce can be generally added, and the addition of a small amount of rare earth elements such as Ce can improve the hot processing property [ F.Cosandey, D.Li, E.Sczerzeme and J.K, tien, metal Trans.A.14A (1983) pp.611-21 ] [ J.Kandra and F.Cosandey, the Effect Of Cerium Additions On The Tensile Ductility Of Nickel-chrome-ceramic Alloys, script metal, 19 (1985) 397 ] (as shown in figure 3) and can improve the high-temperature oxidation resistance of the alloy; however, the Ce content in the solid solution in the general alloy should be 145ppm or more by weight to exert the effect of improving the hot workability. However, if the Ce content exceeds 500ppm by weight, oxides or precipitated phase residues are likely to be formed, and the alloy properties are adversely affected.

However, ce has strong oxidation tendency, so the prior art is smelted by an electric furnace or VIM and then refined by ESR to produce an integral Ni-20Cr alloy cast ingot, wherein Ce element added by ingredients is easy to oxidize in a high-temperature process to become smelting slag, and the melting loss of a solute forming Ce is removed after floating, so that Ce remained in the cast ingot is always lower than 20% of the addition amount, especially the bottom of the cast ingot is more serious. If 200ppm wt.% Ce is added during actual smelting, the solid solution amount remained in the blank is generally less than 30ppm wt.% through smelting processes such as ESR, so that the effect of improving the processing property cannot be exerted. Because the metal raw materials such as Ce and the like are high in price, the problem that the derivative cost is increased due to the fact that the addition amount is greatly increased, and the burning loss of the ingot near the bottom is serious, the composition difference of the upper part and the lower part of the ingot is overlarge, and the composition requirement of subsequent products is not met.

Disclosure of Invention

In order to solve the above problems encountered with martensitic steel and nickel alloy, the present invention proposes a method for performing ESR with a multi-stage combined (preferably 2-5-forging combined) electrode ingot in the longitudinal direction.

The specific technical scheme adopted by the invention is as follows:

the method for controlling the trace element distribution in ESR cast ingot is characterized in that the method utilizes a mode of carrying out ESR refining process by using a combined electrode ingot for controlling components to control the trace element distribution in the length direction of easy-to-burn trace elements in steel or alloy cast ingot so as to reduce the variation degree of the integral components of the cast ingot and produce cast ingot with uniformly distributed trace elements.

Further, the trace elements are Ta, Y, ce, ti, si or Mn, and the target trace elements of ESR output cast ingots are between 50ppm wt.% and 2.0 wt.%.

The above combined electrode ingot can be manufactured by combining 2-10 blanks, and preferably 1-5 blanks are combined to form the electrode ingot.

The above-mentioned component control method selects and arranges the electrode under the combined electrode to perform ESR remelting first to have higher trace element content, and the trace element content decreases from the middle section to the head end of the electrode ingot.

The combination of the combined electrode ingots adopts an end face tungsten electrode argon protection welding mode.

In the ESR process, al can be added to inhibit oxidation burning loss, the Al content of 100-600 g (1 t-5 t steel ingot) can be added into the premelting slag, or the Al content can be added in a timing and quantitative manner in the electroslag process, namely 15-55 g/15-30 min, and the addition amount can be increased or decreased appropriately according to the smelting steel grade.

The electrode ingot is smelted and produced by selecting VIM, VOD or electric furnace, and the like, and is combined and subjected to ESR (equivalent series resistance) process to produce the ingot.

The usable composition ranges of the elements of the nickel-base alloy are shown in the following table (%):

the ranges of the usable components of the low-activation martensitic alloy are shown in the following table (%):

the RAFM steel applied by the invention adopts the addition of Ta, V and other elements to replace Mo, nb, ni and other elements in the conventional martensitic steel to design alloy components on the basis of the research of Fe-Cr-W alloy, and reduces the principle of influencing the activated impurity elements and gas content to design the alloy components (except 8.0% -9.0% of Cr,0.3% -0.7% of Mn,1.3% -1.7% of W, some C, V, ta and other elements are additionally added, and the balance is Fe).

Adding alloy design introduction: the nickel alloy applied by the invention is based on the research of Ni-Cr series alloy.

The invention uses the longitudinal multi-stage combination (preferably 2-5 forging combination) electrode ingot to proceed ESR method, the electrode ingot entering ESR is divided into a plurality of component regions, so that the remelting refined part (i.e. near the bottom, with more serious burning loss) of the electrode ingot of ESR has higher Ce and Ta content, the upper half of the electrode ingot of ESR has lighter burning loss, so it can have lower Ce and Ta components. By using the combination of the electrode ingots with different compositions, the ESR ingots produced can have more uniform head and tail compositions, thereby achieving the objective of controlling the composition of the whole ingot, avoiding a large amount of expensive elements which are easy to burn during feeding, and reducing the cost.

Drawings

FIG. 1 is a schematic diagram of the operation of the electroslag remelting furnace described in the background art;

FIG. 2 is a photograph of the full width surface (about 900mm in width) of a prior art high temperature forged 80Ni-20Cr billet after forging.

FIG. 3 shows the reduction of area for the high temperature tensile test corresponding to the addition of Ce element to the 80Ni-20Cr alloy in the background art, which shows that the high temperature processability was improved [ F.Cosandey and J.Kandra, metall.Trans.A,18A (1987) pp.1239-48 ].

FIG. 4 is a schematic diagram showing the addition of Ta element to CLAM steel in example b, followed by two-stage butt welding of 1.5 ton (VIM ingot # 2) and 1.5 ton (VIM ingot # 3) of VIM electrode ingot to form an electrode ingot, and ESR refining.

FIG. 5 is a schematic diagram showing four butt welding of 0.75 ton+ (VIM ingot # 5) 0.75 ton+ (VIM ingot # 6) 0.75 ton+ (VIM ingot # 7) 0.75 ton of VIM electrode ingot to an electrode ingot, followed by ESR refining, by adding Ta element to the CLAM steel and adding Ta element in example c.

FIG. 6 is a schematic diagram showing the addition of Ce element to 80Ni-20Cr alloy in example e, two butt welding of 1.5 ton (VIM ingot # 2) and 1.5 ton (VIM ingot # 3) of VIM electrode ingot to form an electrode ingot, and ESR refining.

FIG. 7 is a schematic diagram showing the three-stage butt welding of 80Ni-20Cr alloy to form an electrode ingot by adding Ce element to (VIM ingot # 4) 1 ton+ (VIM ingot # 5) 1 ton+ (VIM ingot # 6) 1 ton of VIM electrode ingot in example f, followed by ESR refining.

Detailed Description

To facilitate understanding of the present invention, examples are set forth below. It should be apparent to those skilled in the art that the examples are provided only to aid in understanding the present invention and should not be construed as limiting the invention in any way.

The various raw materials of the present invention may be obtained commercially unless specifically stated; or prepared according to methods conventional in the art. Unless defined or otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any method and material similar or equivalent to those described may be used in the methods of the present invention.

Next, an ESR ingot of 3 tons of CLAM and an ESR ingot of 3 tons of 80Ni-20Cr will be described. 1. ESR ingot of 3 ton CLAM

The ESR ingot of 3 tons of CLAM is used to meet the component control requirement that the Ta component of the whole ingot is controlled to be 0.05-0.18%.

Comparative example a

In the conventional direct smelting mode, ESR refining was performed in a single monolithic (VIM ingot # 1) electrode ingot of 3 tons, and the test batch amounts and the head and tail compositions of the ingots are shown in tables 1 and 2, respectively.

Example b

As shown in FIG. 4, the electrode ingot was formed by butt welding two sections of 1.5 ton (VIM ingot # 2) and 1.5 ton (VIM ingot # 3) of VIM electrode ingot, and ESR refining was performed, wherein the ingredient Ta content of the bottom VIM ingot #2 was relatively higher than that of the VIM ingot #3, and the head and tail compositions of the ingots were also shown in Table 1 and Table 2, respectively.

Example c

As shown in FIG. 5, the four-stage butt welding of 0.75 ton+ (VIM ingot # 4) 0.75 ton+ (VIM ingot # 5) 0.75 ton+ (VIM ingot # 6) 0.75 ton (VIM ingot # 7) to an electrode ingot was performed, and the ESR refining was performed, wherein the amount of Ta (wt.%) was as the near-bottom VIM ingot #4> VIM ingot #5> VIM ingot #6> VIM ingot #7, and the head and tail compositions of the ingots were also shown in tables 1 and 2, respectively.

TABLE 1 Table of the input raw materials (%) of examples and comparative examples for producing CLAM alloy ingots according to the present invention

CLAM	C	Mn	Fe	Cr	W	V	Ta
								Standard Min	0.08	0.4	Remainder of the process	8.5	1.3	0.15	0.05
Standard Max	0.12	0.5	Remainder of the process	9.5	1.5	0.25	0.18
								VIM #1 formulation	0.1	0.46	Remainder of the process	8.75	1.42	0.2	0.196
VIM #2 formulation	0.1	0.46	Remainder of the process	8.75	1.42	0.2	0.196
								VIM #3 formulation	0.1	0.46	Remainder of the process	8.75	1.42	0.2	0.135
VIM #4 formulation	0.1	0.46	Remainder of the process	8.75	1.42	0.2	0.196
								VIM #5 formulation	0.1	0.46	Remainder of the process	8.75	1.42	0.2	0.135
VIM #6 formulation	0.1	0.46	Remainder of the process	8.75	1.42	0.2	0.115
								VIM #7 formulation	0.1	0.46	Remainder of the process	8.75	1.42	0.2	0.115

TABLE 2 comparison of Ta content and uniformity in examples and comparative examples for producing CLAM alloy ingots according to the present invention

2. ESR ingot of 3 ton 80Ni-20Cr

With an ESR ingot of 3 tons of 80Ni-20Cr, the control requirement of the Ce component of the whole ingot is controlled to be 150-400ppm wt.%.

Comparative example d

In the conventional direct smelting mode, ESR refining was performed in a single monolithic (VIM ingot # 1) electrode ingot of 3 tons, and the test batch amounts and the head and tail compositions of the ingots are shown in tables 3 and 4, respectively.

Example e

As shown in FIG. 6, the electrode ingot was formed by two butt welding of (VIM ingot # 2) 1.5 ton+ (VIM ingot # 3) 1.5 ton VIM electrode ingot, and ESR refining was performed, wherein the content of Ce in the ingredients of the bottom VIM ingot #2 was relatively higher than that of the ingredients of the VIM ingot #3, and the head and tail ingredients of the ingots are shown in Table 3 and Table 4, respectively.

Example f

As shown in FIG. 7, the electrode ingot was formed by three butt welding of (VIM ingot # 4) 1 ton+ (VIM ingot # 5) 1 ton+ (VIM ingot # 6) 1 ton of VIM electrode ingot, and ESR refining was performed, wherein the amount of Ce (wt.%) was found to be about the bottom VIM ingot #4> VIM ingot #5> VIM ingot #6, and the head and tail compositions of the ingots were also shown in Table 3 and Table 4, respectively.

Table 3. Table of the ingredients of the input raw materials (wt.%) of examples and comparative examples for producing 80Ni-20Cr alloy ingots according to the present invention

80Ni20Cr	C	Si	Mn	Ni	Cr	Fe	Al	Ce
									Standard Min	0	0.75	0	Remainder of the process	20	0	0	145ppm
Standard Max	0.08	1.60	0.6	Remainder of the process	23	1.0	0.5	450ppm
									VIM #1 formulation	0.05	0.97	0.1	Remainder of the process	21	0.05	0.12	800ppm
VIM #2 formulation	0.05	0.97	0.1	Remainder of the process	21	0.05	0.12	880ppm
									VIM #3 formulation	0.05	0.97	0.1	Remainder of the process	21	0.05	0.12	500ppm
VIM #4 formulation	0.05	0.97	0.1	Remainder of the process	21	0.05	0.12	880ppm
									VIM #5 formulation	0.05	0.97	0.1	Remainder of the process	21	0.05	0.12	500ppm
VIM #6 formulation	0.05	0.97	0.1	Remainder of the process	21	0.05	0.12	420ppm

TABLE 4 comparison of Ce content and uniformity for the examples and comparative examples of producing 80Ni-20Cr alloy ingots according to the present invention

From the above comparison, it can be confirmed that the method of ESR using the combined electrode ingot of the present invention can achieve the effects of reducing the total amount of trace elements to be added (lower average trace elements to be added) and increasing the uniformity of components of the whole ingot (small difference between trace elements at the head and tail), and assist the ingot to hit the target region of trace elements to be cast (to achieve the qualification of components).

Claims

1. The method uses a combined electrode ingot for controlling components to perform ESR refining process to control the distribution of trace elements easy to burn in steel or alloy ingot in the length direction so as to reduce the variation degree of the whole components of the ingot and produce an ingot with uniformly distributed trace elements; the method is characterized in that the method for carrying out ESR refining process by using the combined electrode ingot of the control components comprises the following steps:

the electrode ingot is divided into a plurality of component sections in the longitudinal direction, the remelted and refined part of the electrode ingot has higher trace element content, and the upper half part of the electrode ingot has lower trace element component.

2. The method of controlling trace element distribution in ESR ingot of claim 1, wherein the trace element is Ta, Y, ce, ti, si or Mn and the target trace element of ESR yield ingot is between 50ppm wt.% and 2.0 wt.%.

3. The method of claim 1, wherein the combined electrode ingot is formed by combining 2-10 blanks.

4. The method of claim 1, wherein the composition control means selects electrodes under the combined electrode to be subjected to ESR remelting first to have higher trace element contents, and the trace element contents decrease from the middle section to the head end of the electrode ingot.

5. The method for controlling trace element distribution in ESR ingot according to claim 1, wherein the combination of combined electrode ingots is end face tungsten argon shielded welding.

6. The method for controlling trace element distribution in ESR ingot according to claim 1, wherein the addition of Al in the ESR process can inhibit oxidation burning loss, and the addition of Al in the amount of 100 g-600 g can be adopted in the premelting slag, or the addition can be adopted in the electroslag process in a timing and quantitative manner, namely 15 g-55 g/15 min-30 min, and the addition amount can be properly increased or decreased according to the smelting steel types.

7. The method for controlling trace element distribution in ESR ingot according to claim 1, wherein said electrode ingot is produced by smelting in VIM, VOD or electric furnace, and combining them to produce ingot by ESR process.

8. Use of the method according to claim 1, in ingots of nickel-base alloys, characterized in that the nickel-base alloys have the following table of the usable composition ranges (%):

9. use of the method according to claim 1 for the casting of low-activation martensitic alloy ingots, wherein the low-activation martensitic alloy has the following table of usable composition ranges (%):