CN112746176A

CN112746176A - Method for controlling distribution of trace elements in ESR (equivalent series resistance) ingot

Info

Publication number: CN112746176A
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: 2021-05-04
Anticipated expiration: 2040-12-29
Also published as: CN112746176B

Abstract

The invention discloses a method for controlling the distribution of trace elements in an ESR (equivalent series resistance) ingot, which utilizes blanks for controlling different components as electrode ingots, combines the electrode ingots and then carries out ESR refining to control the distribution of the trace elements which are easy to burn and lose in steel or alloy in the length direction so as to reduce the variation degree of the whole components and produce a finished ingot with more uniform distribution of the trace elements.

Description

Method for controlling distribution of trace elements in ESR (equivalent series resistance) ingot

Technical Field

The invention belongs to the technical field of metal smelting, and particularly relates to a method for controlling distribution of trace elements in ESR (equivalent series resistance) ingots.

Background

Vacuum induction melting is essentially a process in which metal is melted by heat generated by passing current through an induction coil under vacuum. The principle is that the vacuum induction smelting furnace is a method for smelting by heating furnace materials by utilizing eddy current generated in a metal conductor by electromagnetic induction under the vacuum condition, and is a complete set of vacuum smelting equipment for melting metals. The method is suitable for scientific research and production units to carry out smelting and casting on nickel-based alloy, special steel, precision alloy, high-temperature alloy, non-ferrous metal and alloy thereof in vacuum or protective atmosphere. It can also be used for smelting and casting rare-earth metals and hydrogen-storing materials. Of note are: firstly, the furnace washing process must ensure that the crucible is fully sintered and the moisture is exhausted, otherwise, the vacuum degree of the later steelmaking stage is not enough and the structure of the cast ingot is influenced. Adding alloy elements in sequence, alloying fully and adding other alloy elements. And thirdly, the flow velocity of the 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 resistance heat generated when current passes through molten slag, and is sequentially solidified into an ingot. The working principle is shown in figure 1, and specifically means that one end of a metal consumable electrode which is connected with a power supply and is produced by vacuum induction melting is immersed in molten slag to melt the end part of the electrode (a large amount of heat is generated when alternating current passes through a high-resistance slag bath), molten metal drops produced by melting pass through the slag bath and drop into a metal molten bath, and then the molten metal drops are continuously cooled by a water-cooled crystallizer and then are condensed into an ingot from bottom to top.

The low-activation ferrite/martensite steel (RAFM) has excellent thermophysical and mechanical properties such as lower radiation swelling and thermal expansion coefficient, higher thermal conductivity and the like, and relatively mature technical foundation. Currently, various countries around the world are developing and studying respective RAFM steels such as Japanese F82H alloy and JLF21 alloy, European EUROFER 97 alloy and U.S. 9Cr-2WVTa alloy, etc.

The strengthening and impurity removing effects of all alloy elements are fully utilized, the comprehensive performance of the alloy is effectively improved, the content of Ta is properly improved, and a large amount of dispersed carbide can be generated, crystal grains can be refined, and the plasticity and toughness of the material are improved by adding the Ta element into the steel. However, metal tantalum has a high melting point, is difficult to melt, has a high affinity with oxygen, is very harsh in melting conditions and melting modes, and is prone to cause compositional variation and burning loss, and at high temperatures, the chemical reaction of elements such as Ta (with the chemical equilibrium formula as follows):

4Ta+5O₂＝2Ta₂O₅

4Al+3O₂＝2Al₂O₃

6Ta+5Al₂O₃＝2Ta₂O₅+10Al

the integral CLAM alloy ingot produced after being smelted by an electric furnace or VIM is subjected to ESR refining, and Ta element added into the ingredients is easy to be oxidized in a high-temperature process to form smelting slag, so that the burning loss of the solute of Ta is formed, particularly the bottom of the ingot is serious. If 0.15% Ta is added during vacuum induction melting, the amount of solid solution remained in the blank is generally less than 0.5% by the melting process such as ESR, so the effect of improving the processing property cannot be achieved. Because metal raw materials such as Ta are expensive, the problem that the addition amount is greatly increased to increase the derivative cost is solved, and the burning loss of the cast ingot close to the bottom is serious, so that the component difference of the upper part and the lower part of the cast ingot is overlarge, and the component requirements of subsequent products are not met.

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

However, the 80Ni-20Cr alloy has a problem of poor ductility in the reheating process, and the product is easily cracked as shown in FIG. 2 when forging or rolling is performed at a temperature lower than 1050 ℃.

Therefore, in order to solve The problem that 80Ni-20Cr alloy is not easy to be hot-worked, alloy design adjustment Of trace element Ce can be generally added, and The addition Of a small amount Of rare earth element such as Ce can improve The hot-working property Of 80Ni-20Cr alloy [ F.Cosandey, D.Li, E.Sczer zeme and J.K, Tien, Metal Trans.A.14A (1983) pp.611-21 ], [ J.Kandra and F.Cosandey, The efficiency Of center additives On The Tensile Dual Of Nickel-Chromium-center Alloys, script metals, 19(1985)397 ] (as shown in FIG. 3), and can improve The high-temperature oxidation resistance Of The alloy; however, the solid solution Ce content in the alloy is usually not less than 145ppm by weight, so that the hot workability is improved. However, if the Ce content exceeds 500ppmw t.%, oxide formation or precipitated phase residue is likely to occur, which adversely affects the alloy properties.

However, Ce has a strong oxidation tendency, so in the prior art, an electric furnace or VIM is used for melting and then ESR refining is performed to produce an integral Ni-20Cr alloy ingot, wherein Ce added in the ingredients is easily oxidized in a high-temperature process to form a melting slag material, and the melting loss of the solute forming Ce is removed after floating, so that Ce remaining in the ingot is often less than 20% of the addition amount, especially the bottom of the ingot is serious. If 200ppm wt.% of Ce is added during practical melting, the solid solution amount remained in the blank is generally less than 30ppm wt.% after the melting process such as ESR, so the effect of improving the processing property cannot be exerted. Because metal raw materials such as Ce are expensive, the problem that the addition amount is greatly increased to increase the derivative cost is solved, and the burning loss of the cast ingot close to the bottom is serious, so that the component difference of the upper part and the lower part of the cast ingot is overlarge, and the component requirement of subsequent products is not met.

Disclosure of Invention

In view of the above-mentioned problems encountered with martensitic steels and nickel alloys, the present invention proposes a method for ESR of an electrode ingot assembled in longitudinal multi-stages, preferably assembled by 2-stage-5 forging.

The invention adopts the following specific technical scheme:

the method for controlling the distribution of trace elements in the ESR ingot is characterized in that the method utilizes a combined electrode ingot with controlled components to carry out an ESR refining process to control the distribution of the trace elements which are easy to burn and lose in the steel or alloy ingot in the length direction so as to reduce the variation degree of the overall components of the ingot and produce the ingot with uniformly distributed trace elements.

Further, the trace element is Ta, Y, Ce, Ti, Si or Mn, and the target trace element of ESR produced ingot is between 50ppm wt.% and 2.0 wt.%.

The assembled electrode ingot can be assembled by 2-10 sections of blanks and then ESR process is performed, wherein 1-5 sections of blanks are preferably assembled into the electrode ingot.

In the above-mentioned component control method, the electrode that is first ESR-remelted under the combined electrode is selected and arranged to have higher trace element content, and the content of trace element content decreases from the middle section to the head end of the electrode ingot.

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

In the ESR process, Al can be added to inhibit oxidation and burning loss, 100 g-600 g (1 t-5 t steel ingot) of Al can be added into premelting slag, or the Al can be added in fixed time and quantity in the electroslag process, namely 15 g-55 g/15 min-30 min, and the adding quantity can be properly increased and decreased according to the type of steel to be smelted.

The electrode ingot is produced by smelting in a VIM, VOD or electric furnace mode, and is combined to produce an ingot by an ESR process.

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

on the basis of research on Fe-Cr-W alloy, the RAFM steel applied by the invention adopts the addition of elements such as Ta and V to replace elements such as Mo, Nb, Ni and the like in the conventional martensitic steel to design the alloy components, and designs the alloy components on the principle of reducing the content of impurity elements and gases influencing activation (except 8.0-9.0% of Cr, 0.3-0.7% of Mn and 1.3-1.7% of W, additionally adding some elements such as C, V, Ta and the like, and the balance of Fe). The nickel alloy applied by the invention is based on the research of Ni-Cr series alloy.

The present invention provides a method for performing ESR on an electrode ingot assembled in multiple stages in the longitudinal direction (preferably, assembled by 2-5 forging), which divides the electrode ingot entering into ESR into multiple component sections, so that the portion of the electrode ingot of ESR that is first subjected to remelting refining (i.e. near the bottom, generally having more serious burning loss) has higher Ce and Ta contents, and the upper half portion of the electrode ingot of ESR generally has less burning loss, so as to have lower Ce and Ta components. By using the above-mentioned multi-stage electrode ingot assembly with different components, the produced ESR ingot has more uniform components at the head and tail, so as to achieve the purpose of controlling the components of the whole ingot, and avoid the high-price elements that are easily burned and damaged by a large amount of material, and reduce the cost.

Drawings

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

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

FIG. 3 is a graph showing the reduction of area in the high temperature tensile test of the 80Ni-20Cr alloy of the background art with Ce added thereto, which shows that the high temperature processing properties can be improved [ F.Cosandey and J.Kandra, Metal.Trans.A, 18A (1987) pp.1239-48 ].

FIG. 4 is a schematic view showing ESR refining of an electrode ingot produced by two-stage welding of a VIM electrode ingot of 1.5 ton (VIM ingot #2) and 1.5 ton (VIM ingot #3) in example b by adding Ta element to CLAM steel.

FIG. 5 is a schematic diagram showing ESR refining of VIM electrode ingots in example c, in which the CLAM steel is added with Ta element and Ta element is added, and the four-stage butt welding is performed on the VIM electrode ingots, wherein the four-stage butt welding is performed on the VIM electrode ingots, and the four-stage butt welding is performed on the VIM electrode ingots, wherein the VIM electrode ingots are 0.75 ton + (VIM ingot #5)0.75 ton + (VIM ingot #6)0.75 ton + (VIM ingot # 7).

FIG. 6 is a schematic view showing ESR refining of an 80Ni-20Cr alloy in example e, in which Ce is added to the alloy, and the alloy is subjected to two-stage welding to form an electrode ingot from a VIM electrode ingot (VIM ingot #2) of 1.5 ton + (VIM ingot #3) of 1.5 ton.

FIG. 7 is a schematic view showing that in example f, an electrode ingot is formed by three-stage butt welding of an 80Ni-20Cr alloy in which Ce is added to the alloy (VIM ingot #4)1 ton + (VIM ingot #5)1 ton + (VIM ingot #6)1 ton, and then ESR refining is performed.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the purpose of facilitating understanding of the present invention and should not be construed as specifically limiting the present invention.

Unless otherwise specified, various starting materials of the present invention are commercially available; or prepared according to conventional methods in the art. Unless defined or indicated otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention.

Next, a description will be given of ESR ingots of 3 tons of CLAM and ESR ingots of 3 tons of 80Ni-20 Cr. 1. ESR ingot of 3 tons CLAM

The ESR ingot of 3 tons CLAM is used to achieve the requirement of controlling the Ta component of the whole ingot to 0.05% -0.18%.

Comparative example a

Conventional direct smelting was carried out using 3 tons of single monolithic (VIM ingot #1) electrode ingot ESR refining, and the amounts of the ingredients tested and the head and tail components of the ingot are shown in tables 1 and 2, respectively.

Example b

As shown in FIG. 4, electrode ingots were produced by two-stage butt welding of a VIM electrode ingot of (VIM ingot #2)1.5 ton + (VIM ingot #3)1.5 ton, and then ESR refining was performed, wherein the amount of Ta in the material of the bottom VIM ingot #2 was relatively higher than that of the material of the VIM ingot #3, and the head and tail components of the ingots were also shown in tables 1 and 2, respectively.

Example c

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

TABLE 1 ingredient table of raw materials (%) for examples and comparative examples of CLAM alloy ingots produced by the present invention

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

TABLE 2 comparison of Ta content and uniformity of CLAM alloy ingots produced according to the present invention

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

The ESR ingot of 3 tons of 80Ni-20Cr is used to achieve the control requirement of Ce component of the whole ingot controlled at 150-400ppm wt.%.

Comparative example d

Conventional direct smelting was carried out using 3 tons of single-piece (VIM ingot #1) electrode ingot ESR refining, and the amounts of the ingredients tested and the head and tail components of the ingot were as shown in tables 3 and 4, respectively.

Example e

As shown in FIG. 6, electrode ingots were produced by two-stage butt welding of a VIM electrode ingot of (VIM ingot #2)1.5 ton + (VIM ingot #3)1.5 ton, and then ESR refining was performed, wherein the content of Ce in the bottom VIM ingot #2 blend was relatively higher than that in VIM ingot #3, and the head and tail components of the ingots were also shown in tables 3 and 4, respectively.

Example f

As shown in FIG. 7, electrode ingots were butt-welded in three stages from (VIM ingot #4)1 ton + (VIM ingot #5)1 ton + (VIM ingot #6)1 ton of VIM electrode ingots, and then ESR refining was performed, wherein the amount (wt.%) of Ce added was such that the amounts of the near-bottom VIM ingot #4> VIM ingot #5> VIM ingot #6, and the head and tail components of the ingots were as shown in tables 3 and 4, respectively.

TABLE 3 ingredient table of raw material (wt.%) for example and comparative example for producing 80Ni-20Cr alloy ingot by the present invention

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

TABLE 4 Ce content and uniformity comparison of the examples and comparative examples of 80Ni-20Cr alloy ingots produced by the present invention

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

Claims

1. The method for controlling the distribution of trace elements in the ESR ingot is characterized in that the method utilizes a combined electrode ingot with controlled components to carry out an ESR refining process to control the distribution of the trace elements which are easy to burn and lose in the steel or alloy ingot in the length direction so as to reduce the variation degree of the overall components of the ingot and produce the ingot with uniformly distributed trace elements.

2. The method of controlling the trace element distribution in an ESR ingot as in claim 1, wherein the trace element is Ta, Y, Ce, Ti, Si or Mn, and the target trace element for ESR-produced ingots is between 50ppm wt.% and 2.0 wt.%.

3. The method of claim 1, wherein the combined electrode ingot is assembled into an ESR ingot from 2 to 10 segments, preferably from 1 to 5 segments.

4. The method of claim 1, wherein the composition control is performed by selecting an electrode having a higher content of trace elements that is disposed below the combined electrode and ESR remelting first, and the content of trace elements decreases from the middle portion to the tip of the electrode ingot.

5. The method for controlling distribution of trace elements in an ESR ingot as recited in claim 1, wherein said modular electrode ingot is assembled by end-face tig welding.

6. The method for controlling the distribution of trace elements in ESR ingots according to claim 1, wherein Al is added to suppress oxidation burning loss in the ESR process, wherein the amount of Al added to the pre-melted slag is 100 g-600 g, or the Al is added in a fixed amount at regular time during the electroslag process, i.e. 15 g-55 g/15 min-30 min, and the amount of Al added can be properly increased or decreased according to the type of steel being melted.

7. The method for controlling distribution of trace elements in ESR ingot as recited in claim 1, wherein the electrode ingot is produced by melting using VIM, VOD or electric furnace, and combined with ESR to produce ingot.

8. The method for controlling the distribution of trace elements in ESR ingot as set forth in claim 1, wherein the nickel-based alloy has the following composition ranges (%):

。

9. the method for controlling the distribution of trace elements in ESR ingot as recited in claim 1, wherein the low activation martensite alloy has the following composition ranges (%):

。