VAR smelting method for preparing pure titanium cast ingot and reducing core inclusions

Abstract

The invention provides a VAR smelting method for preparing a pure titanium cast ingot and reducing core inclusions, and relates to the field of metallurgy, and the VAR smelting method comprises the following steps: according to design components of a target product pure titanium cast ingot, taking sponge titanium as a raw material, adopting a vertical press to press into electrode blocks, stacking a plurality of electrode blocks to prepare an electrode bar with a hole in the core, the electrode bar with the hole in the first step is installed and welded through a vacuum plasma welding box, the center of the welded electrode bar with the hole is blocked, and a consumable electrode is obtained; and the consumable electrode obtained in the second step is subjected to secondary VAR smelting, and the pure titanium cast ingot is obtained. According to the method, the probability of inclusion in the central part in the pure titanium smelting and ingot casting process can be effectively reduced, so that the defects of peeling, wrinkling and the like on the surface of a titanium plate coil are reduced, and help is provided for solving and treating subsequent quality problems.

Description

Technical Field

[0001] The invention relates to the field of metallurgy, and in particular to a VAR smelting method for preparing pure titanium ingots and reducing core inclusions. Background Art

[0002] VAR furnace stands for vacuum consumable arc furnace, which is currently mainly used as one of the equipment for melting titanium and titanium alloys. Compared with traditional melting processes, it has the advantages of high uniformity of ingot composition, low environmental pollution, and good working environment. Therefore, it has been widely used in the production of titanium and titanium alloys.

[0003] Before smelting pure titanium in a VAR furnace, the raw material sponge titanium needs to be pressed into electrode blocks, and then multiple electrode blocks are welded into electrode rods. A vertical press is used to press the electrodes to make electrode rods with holes in the core. This will cause the weld nodule to enter the hole during the welding of the auxiliary electrode and react with the core sponge titanium to form low-density inclusions, which cannot be melted during the smelting process and remain in the ingot.

[0004] There is no patent published yet on the VAR melting method for preparing pure titanium ingots by using vertical pressing electrodes to reduce inclusions in the core. The purpose of the present invention is to reduce inclusions in the core of the ingot and improve the quality of the subsequent titanium coil surface. Summary of the invention

[0005] According to the above technical problem that the existing method for preparing pure titanium has the problem of weld nodules entering the holes and reacting with the core titanium sponge to generate low-density inclusions, a VAR smelting method for preparing pure titanium ingots with reduced core inclusions is provided. The present invention mainly seals the center hole before welding the electrode rod, which can effectively reduce the probability of core inclusions during pure titanium smelting and ingot casting, thereby reducing defects such as peeling and wrinkles on the surface of titanium coils.

[0006] The technical means adopted by the present invention are as follows:

[0007] 1. A VAR smelting method for preparing pure titanium ingots to reduce core inclusions, comprising the following steps:

[0008] Step 1: According to the designed composition of the target product pure titanium ingot, sponge titanium is used as a raw material to press into an electrode block, and multiple electrode blocks are stacked to form an electrode rod with a hole in the center;

[0009] Step 2: using a vacuum plasma welding box to weld the electrode rod with holes in step 1, and sealing the core of the electrode rod with holes after welding to obtain a consumable electrode;

[0010] Step 3: Perform secondary VAR smelting on the consumable electrode obtained in step 2 to obtain a pure titanium ingot.

[0011] Furthermore, the step 2 of sealing the core of the electrode rod with the hole comprises the following steps:

[0012] Step S201, knead and compact the titanium chips and insert them into the electrode rod with a hole at the center, 40 mm below the end face of the center hole, and put the polished rod into the center hole above the titanium chips, so that the upper end face of the polished rod is flush with the upper end face of the electrode rod;

[0013] Step S202: Based on S201, titanium sponge is sprinkled on the electrode rod and coated on the center of the end face of the electrode rod to obtain a consumable electrode.

[0014] Furthermore, the specific process of VAR pre-smelting preparation in step 3 includes the following steps:

[0015] Step S301, assemble the crucible and the bottom pad and install them into the smelting station, install the consumable electrode into the crucible and fix it, and seal the furnace to evacuate;

[0016] Step S302, welding the consumable electrode and the auxiliary electrode obtained by evacuating the vacuum in step S301 in a vacuum consumable arc furnace, controlling the vacuum degree before welding to ≤5Pa, the welding current to 3-12kA, the welding voltage to 28-36V, obtaining a primary welding electrode after welding, cooling for more than 45 minutes and then taking it out of the furnace for inspection.

[0017] Furthermore, the specific process of VAR smelting in step 3 includes the following steps:

[0018] Step S311, a layer of titanium sponge is laid on the end of the primary welding electrode to be welded as an arc starter, the electrode rod is lowered, an arc is ignited between the transition electrode and the consumable electrode, and when the two end surfaces are heated and the arc is stable, they are welded tightly together;

[0019] Step S312, start the slide valve pump and the roughing valve in sequence, and after the vacuum degree reaches 10Pa, start the Roots pump;

[0020] Step S313, forming a stable arc between the consumable electrode and the arc starter at the bottom of the crystallizer, increasing the temperature of the arc zone, and forming a molten metal pool at the bottom of the crystallizer;

[0021] Step S314: Keep the arc between the consumable electrode and the molten metal pool stable so that the consumable electrode is continuously melted and solidified into an ingot to obtain a pure titanium ingot.

[0022] Furthermore, two smeltings are carried out in the VAR furnace, the first smelting current is 15-26 kA, the second smelting current is 20-36 kA, and the arc stabilization current is 9-20A.

[0023] Furthermore, the composition of the polished rod material is consistent with that of the electrode rod, and the surface is smooth and free of oxide scale, and the end is flattened.

[0024] Furthermore, in the step 1, the electrode rod diameter φ is 470-820 mm, and the core inner diameter φ is 80-85 mm; the polished rod material is a forged polished rod material, and the specific specification is φ77-83 (±0.5)×40 mm.

[0025] Furthermore, in the step three: 0.5-1 kg of titanium chips, 1 section of polished rod and 0.5-3 kg of titanium sponge are used.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The present invention can effectively reduce the probability of central inclusions during pure titanium smelting and ingot casting, thereby reducing defects such as peeling and wrinkling on the surface of the titanium plate coil, and providing assistance for solving and handling subsequent quality problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 The figure is a flow chart of the method of the present invention.

[0030] Figure 2 It is a schematic diagram of placing plugging materials for an electrode rod with a hole in the center according to the present invention. DETAILED DESCRIPTION

[0031] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0035] like Figure 1-2 As shown, the present invention provides a VAR smelting method for preparing pure titanium ingots to reduce core inclusions. The method can effectively reduce the inclusions in the core of the ingot, improve the quality of the titanium ingot, reduce the subsequent processing plate roll surface defect fee and labor cost, and is suitable for industrial production, comprising the following steps:

[0036] Step 1: According to the designed composition of the target product pure titanium ingot, sponge titanium is used as a raw material to press into an electrode block, and multiple electrode blocks are stacked to form an electrode rod with a hole in the center;

[0037] Step 2: using a vacuum plasma welding box to weld the electrode rod with holes in step 1, and sealing the core of the electrode rod with holes after welding to obtain a consumable electrode;

[0038] The process of sealing the core of an electrode rod with a hole includes the following steps:

[0039] Step S201, knead and compact the titanium chips and insert them into the electrode rod with a hole at the center, 40 mm below the end face of the center hole, and put the polished rod into the center hole above the titanium chips, so that the upper end face of the polished rod is flush with the upper end face of the electrode rod;

[0040] Step S202: based on S201, sponge titanium is sprinkled on the electrode rod and coated on the center of the end surface of the electrode rod to obtain a consumable electrode;

[0041] Use 0.5-1kg of titanium chips, 1 section of polished rod and 0.5-3kg of titanium sponge.

[0042] Step 3: performing secondary VAR smelting on the consumable electrode obtained in step 2 to obtain a pure titanium ingot;

[0043] The specific process of VAR pre-smelting preparation in step 3 includes the following steps:

[0044] Step S301, assemble the crucible and the bottom pad and install them into the smelting station, install the consumable electrode into the crucible and fix it, and seal the furnace to evacuate;

[0045] Step S302, welding the consumable electrode and the auxiliary electrode obtained by evacuating the vacuum in step S301 in a vacuum consumable arc furnace, controlling the vacuum degree before welding to ≤5Pa, the welding current to 3-12kA, the welding voltage to 28-36V, obtaining a primary welding electrode after welding, cooling for more than 45 minutes and then taking it out of the furnace for inspection.

[0046] The specific process of secondary VAR smelting includes the following steps:

[0047] Step S311, a layer of turnings of the same type is placed on the end of the primary welding electrode to be welded as an arc starter, the electrode rod is lowered, an arc is ignited between the transition electrode and the consumable electrode, and when the two end faces are heated and the arc is stable, they are welded tightly together;

[0048] Step S312, start the slide valve pump and the roughing valve in sequence, and after the vacuum degree reaches 10Pa, start the Roots pump;

[0049] Step S313, forming a stable arc between the consumable electrode and the arc starter at the bottom of the crystallizer, increasing the temperature of the arc zone, and forming a molten metal pool at the bottom of the crystallizer;

[0050] Step S314: Keep the arc between the consumable electrode and the molten metal pool stable so that the consumable electrode is continuously melted and solidified into an ingot to obtain a pure titanium ingot.

[0051] It also includes the preparation before smelting: ① Check the materials: According to the smelting process sheet, check the titanium material grade TA1 or TA2, the number of electrode sections 18-24, the length 4-5m, the mass 3-10T, and ensure that all parameters meet the requirements; ② Select the crucible: According to the electrode diameter, select a suitable crucible (the crucible diameter is usually 0.05-0.15 meters larger than the electrode). At the same time, ensure that the crucible is well sealed, has no water seepage, and is thoroughly cleaned. ③ Prepare the electrode: Confirm that the auxiliary electrode and the consumable electrode are of the same grade, and weld them firmly under a vacuum environment.

[0052] Melting operation: ① Welding electrode: Lay a layer of titanium sponge as an arc starter on the end of the consumable electrode to be welded, then lower the electrode rod to make an arc between the transition electrode and the consumable electrode. When the two end faces are heated and the arc is stable, weld them tightly together; ② Vacuuming: Open the slide valve pump and the rough pump valve in turn, and turn on the Roots pump after the vacuum is drawn to 10Pa; ③ Arc starting: Form a stable arc between the consumable electrode and the arc starter at the bottom of the crystallizer to increase the arc zone temperature and form a metal molten pool at the bottom of the crystallizer. ④ Normal smelting: Keep the arc between the consumable electrode and the metal molten pool stable so that the consumable electrode continues to melt and solidify into an ingot.

[0053] The primary melting current is 15-26kA, the secondary melting current is 20-36kA, and the arc stabilization current is 9-20A.

[0054] The composition of the polished rod is consistent with that of the electrode rod, and the surface is smooth and free of oxide scale, and the end is flattened.

[0055] In step 1, the electrode rod diameter φ is 470-820 mm, the core inner diameter φ is 80-85 mm; the center rod specification is φ77-83 (±0.5) × 40 mm.

[0056] Example 1: For pure titanium TA1 smelting. In actual production, 9 tons of TA1 were smelted, with the same raw materials, the same smelting process and no abnormalities during the smelting process. Compared with the titanium ingots without the electrode center through the rod, the surface wrinkle defects of the titanium plate coils were reduced by 40.00%, and the peeling defects were reduced by 60.28%.

[0057] Example 2: For pure titanium TA1 smelting. In actual production, 3 tons of TA1 were smelted with the same raw materials, smelting process and no abnormalities during the smelting process. Compared with the titanium ingots without smelting rods, the surface wrinkle defects of the titanium coils using the electrode center rod were reduced by 28.14%, and the peeling defects were reduced by 33.51%.

[0058] Example 3: For pure titanium TA2 smelting. In actual production, 9 tons of TA2 were smelted with the same raw materials, smelting process and no abnormalities during the smelting process. Compared with the titanium ingots without electrode center rod smelting, the surface wrinkle defects of titanium coils were reduced by 36.46% and the peeling defects were reduced by 53.12%.

[0059] Example 4: For pure titanium TA2 smelting. In actual production, 3 tons of TA2 were smelted with the same raw materials, smelting process and no abnormalities during the smelting process. Compared with the titanium ingots without smelting rods, the surface wrinkle defects of the titanium coils using the electrode center rod were reduced by 21.26%, and the peeling defects were reduced by 18.35%.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A VAR smelting method for preparing pure titanium ingots to reduce core inclusions, characterized in that: The following steps are involved: Step 1: According to the designed composition of the target product pure titanium ingot, sponge titanium is used as a raw material to press into an electrode block, and multiple electrode blocks are stacked to form an electrode rod with a hole in the center; Step 2: using a vacuum plasma welding box to weld the electrode rod with holes in step 1, and sealing the core of the electrode rod with holes after welding to obtain a consumable electrode; Step 3: Perform secondary VAR smelting on the consumable electrode obtained in step 2 to obtain a pure titanium ingot.

2. The VAR smelting method for preparing pure titanium ingots to reduce core inclusions according to claim 1, characterized in that: The step 2 of sealing the core of the electrode rod with holes comprises the following steps: Step S201, knead and compact the titanium chips and insert them into the electrode rod with a hole at the center, 40 mm below the end face of the center hole, and put the polished rod into the center hole above the titanium chips, so that the upper end face of the polished rod is flush with the upper end face of the electrode rod; Step S202: Based on S201, titanium sponge is sprinkled on the electrode rod and coated on the center of the end face of the electrode rod to obtain a consumable electrode.

3. The VAR smelting method for preparing pure titanium ingots with reduced core inclusions according to claim 1, characterized in that: The specific process of VAR pre-smelting preparation in step 3 includes the following steps: Step S301, assemble the crucible and the bottom pad and install them into the smelting station, install the consumable electrode into the crucible and fix it, and seal the furnace to evacuate; Step S302, welding the consumable electrode and the auxiliary electrode obtained by evacuating the vacuum in step S301 in a vacuum consumable arc furnace, controlling the vacuum degree before welding to ≤5Pa, the welding current to 3-12kA, the welding voltage to 28-36V, obtaining a primary welding electrode after welding, cooling for more than 45 minutes and then taking it out of the furnace for inspection.

4. The VAR smelting method for preparing pure titanium ingots with reduced core inclusions according to claim 3, characterized in that: The specific process of VAR smelting in step 3 includes the following steps: Step S311, a layer of titanium sponge is laid on the end of the primary welding electrode to be welded as an arc starter, the electrode rod is lowered, an arc is ignited between the transition electrode and the consumable electrode, and when the two end surfaces are heated and the arc is stable, they are welded tightly together; Step S312, start the slide valve pump and the roughing valve in sequence, and after the vacuum degree reaches 10Pa, start the Roots pump; Step S313, forming a stable arc between the consumable electrode and the arc starter at the bottom of the crystallizer, increasing the temperature of the arc zone, and forming a molten metal pool at the bottom of the crystallizer; Step S314: Keep the arc between the consumable electrode and the molten metal pool stable so that the consumable electrode is continuously melted and solidified into an ingot to obtain a pure titanium ingot.

5. The VAR smelting method for preparing pure titanium ingots with reduced core inclusions according to claim 4, characterized in that: Two melting processes are carried out in the VAR furnace, the first melting current is 15-26kA, the second melting current is 20-36kA, and the arc stabilization current is 9-20A.

6. The VAR smelting method for preparing pure titanium ingots with reduced core inclusions according to claim 2, characterized in that: The composition of the polished rod material is consistent with that of the electrode rod, and the surface is smooth and free of oxide scale, and the end is flattened.

7. The VAR smelting method for preparing pure titanium ingots with reduced core inclusions according to claim 1, characterized in that: In the step 1, the electrode rod diameter φ is 470-820 mm, and the core inner diameter φ is 80-85 mm; the polished rod material is a forged polished rod material, and the specific specification is φ77-83 (±0.5)×40 mm.

8. The VAR smelting method for preparing pure titanium ingots with reduced core inclusions according to claim 1, characterized in that: In the step 3, 0.5-1 kg of titanium chips, 1 section of polished rod and 0.5-3 kg of titanium sponge are used.

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