15-5PH stainless steel electrode bar and manufacturing method thereof

Abstract

The invention relates to a 15-5PH stainless steel electrode bar and a preparation method thereof, belongs to the technical field of metal material manufacturing, and solves the problems that in the prior art, 15-5PH stainless steel is high in manufacturing cost, and large shrinkage cavities and cracks are easily formed in the casting process of the electrode bar. The preparation method comprises the following steps: (1) preparing 15-5PH stainless steel liquid through an electric furnace + VOD + LF process; (2) the molten steel is poured in an electrode mold, an electrode bar is obtained, the electrode mold comprises an ingot mold base and an ingot mold located on the ingot mold base, the appearance of the ingot mold is a circular truncated cone with the diameter of the upper bottom face smaller than that of the lower bottom face, an inner cavity of the ingot mold is a circular truncated cone with the diameter of the upper bottom face larger than that of the lower bottom face, and the inner cavity of the ingot mold is a circular truncated cone with the diameter of the upper bottom face larger than that of the lower bottom face; the central axis of the inner cavity coincides with the central axis of the ingot mold. According to the method, low-price metal alloy is adopted as a raw material, and raw material and process selection is expanded; and the special-shaped electrode mold is adopted for pouring, so that the defects of shrinkage cavities, cracking and the like of the electrode bar are avoided, the production cost is reduced, and the product yield is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal material manufacturing, and in particular to a 15-5PH stainless steel electrode rod and a preparation method thereof. Background Art

[0002] The existing 15-5PH stainless steel for aviation generally adopts the smelting process of vacuum induction + vacuum consumable. Since vacuum induction requires the use of pure metal raw materials, the production cost is relatively high; the vacuum induction furnace is generally small, which makes the production process slow; in addition, due to the composition characteristics of 15-5PH stainless steel, the molten steel is prone to segregation. In the process of casting electrode rods using existing electrode molds, deeper shrinkage holes are easily generated at the head of the electrode rod, and it is also easy to crack after the mold is opened.

[0003] Therefore, a new method for preparing 15-5PH stainless steel electrode rods is urgently needed to improve steel production efficiency and reduce production costs. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a 15-5PH stainless steel electrode rod and a preparation method thereof, so as to solve at least one of the problems in the prior art that the manufacturing cost of 15-5PH stainless steel is high and large shrinkage cavities and cracks are easily formed during the casting process of the electrode rod.

[0005] On the one hand, an embodiment of the present invention provides a method for preparing a 15-5PH stainless steel electrode rod, the method comprising:

[0006] (1) Preparing 15-5PH stainless steel liquid by electric furnace smelting + VOD + LF process;

[0007] (2) pouring the molten steel into an electrode mold to obtain an electrode rod, wherein the electrode mold includes an ingot mold base and an ingot mold located on the ingot mold base, the ingot mold shape is a truncated cone with an upper bottom surface diameter smaller than a lower bottom surface diameter, the ingot mold inner cavity is a truncated cone with an upper end diameter larger than a lower end diameter, the central axis of the ingot mold inner cavity coincides with the central axis of the ingot mold outer shape, and the ingot mold inner cavity and the ingot mold outer shape have the same taper.

[0008] Further, calculated according to mass percentage, the elements constituting the 15-5PH stainless steel include: C≤0.070%, Mn≤1.00%, Si≤1.00%, P≤0.030%, S≤0.015%, Cr14.00~15.50%, Ni 3.50~5.50%, Cu 2.50~4.50%, Nb+Ta 5C (5 times the C content)~0.45%, Mo≤0.5%, and the balance is Fe.

[0009] Furthermore, in step (1), the tonnage of the electric furnace is 30 to 60 tons, and the raw material is a metal alloy.

[0010] Furthermore, the process parameters of VOD are: opening temperature 1580±10℃, VCD ultimate vacuum ≤67Pa, overblow 30Nm 3 .

[0011] Furthermore, the process parameters of LF are as follows: refining temperature 1600±10℃, aluminum powder diffusion deoxidation, and white slag holding time 30-40min.

[0012] Furthermore, in step (2), the height of the ingot mold is 3000-4500 mm, and the median diameter of the inner cavity of the ingot mold is 580 mm.

[0013] Furthermore, in step (2), the taper of the ingot mold is 1.1 to 1.25%.

[0014] Furthermore, in step (2), the pouring process parameters are: mold-ingot ratio of 1.0 to 1.3, pouring speed of 0.6 to 0.7 t / min, and pouring temperature of 40 to 50° C. higher than the melting point of the 15-5PH stainless steel.

[0015] Furthermore, in step (2), a layer of insulating riser is embedded in the top of the inner cavity of the ingot mold along the circumferential direction, and the height of the insulating riser is 300-350 mm and the thickness is 40-50 mm.

[0016] On the other hand, an embodiment of the present invention provides a 15-5PH stainless steel electrode rod, which is manufactured by the above method.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0018] 1. The present invention adopts the electric furnace + VOD + LF process to reduce the standard requirements of raw materials, improve the efficiency of molten steel smelting, and reduce the manufacturing cost; compared with the existing vacuum induction smelting that requires the use of high-purity pure metal raw materials, the process of the present invention can use low-priced metal alloys as raw materials, and on the basis of ensuring that the element composition of 15-5PH stainless steel meets the requirements, expand the selection of raw materials and processes, improve steel production efficiency, and reduce production costs.

[0019] The present invention adopts a special-shaped electrode mold to cast molten steel, and the structural design of the special-shaped electrode mold is as follows: Figure 1As shown, during the pouring of molten steel, the electrode rod can be cooled and solidified sequentially from the bottom to the head. First, along the direction from the bottom to the head of the electrode mold, the thickness of the ingot mold increases successively, and the bottom with a larger wall thickness quickly cools and solidifies the molten steel to form a thicker chill layer. The ingot mold wall thickness corresponding to the molten steel closer to the head direction decreases successively, and the cross-sectional diameter of the truncated cone occupied by the molten steel increases successively. Both of these designs cause the cooling and solidification speed of the molten steel to decrease successively in the direction from the bottom to the head, and the chill layer formed by the electrode rod becomes thinner successively. Therefore, during the pouring of molten steel, when the lower layer of molten steel solidifies, there is always unsolidified molten steel in the upper layer to supplement the shrinkage cavity that occurs when the lower layer of molten steel solidifies, and in the direction from the bottom to the head, the proportion of liquid phase increases successively, ensuring that there is enough molten steel to supplement the shrinkage, avoiding the occurrence of shrinkage cavity, cracking and other defects in the produced electrode rod, while reducing the production cost, and improving the product yield.

[0020] 2. The present invention achieves the removal of gas elements such as O and N and other impurity elements (such as S, P, etc.) in 15-5PH stainless steel liquid by regulating the specific process operations and process parameters in vacuum oxygen decarburization (COD) and ladle refining (LF), thereby improving the cleanliness of the molten steel and making the temperature and composition of the molten steel uniform.

[0021] 3. The present invention controls the cooling speed of the poured molten steel and the thickness of the chilled layer by adjusting the size of the electrode mold and the pouring process parameters, so as to ensure that during the pouring process of the molten steel, when the lower layer of molten steel solidifies, there is always unsolidified molten steel in the upper layer, which supplements the shrinkage cavities that appear when the lower layer of molten steel solidifies and increases the proportion of the upper liquid phase; in particular, the head portion is kept at the thinnest chilled layer, ensuring a larger proportion of the liquid phase and achieving the final solidification. Compared with the prior art, the electrode rod formed by the method of the present invention may be shorter, but the middle part can be filled.

[0022] 4. In order to make the heat dissipation of the electrode rod head slower during the solidification process, the present invention installs and embeds a layer of insulating cap on the top of the special-shaped electrode mold, further increasing the final liquid phase ratio, making the final steel liquid shrinkage more sufficient, avoiding cracking of the electrode rod, and improving the product yield rate.

[0023] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0025] Figure 1 (a) is a schematic diagram of the structure of the special-shaped electrode die designed by the present invention; (b) is a schematic diagram of the structure of the head riser of the special-shaped electrode die;

[0026] Figure 2 This is an appearance diagram of the 15-5PH stainless steel electrode rod 1 prepared in Example 1;

[0027] Figure 3 It is a schematic diagram of the structure of a traditional electrode mold;

[0028] Figure 4 This is the appearance diagram of the 15-5PH stainless steel electrode rod 7 prepared in Comparative Example 3.

[0029] Reference numerals:

[0030] 1- ingot mold; 2- ingot mold base; 3- insulation riser. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0032] The existing 15-5PH alloy steel materials mostly adopt vacuum induction + vacuum consumable smelting process, among which, vacuum induction smelting must use a relatively small tonnage vacuum induction furnace, use high-purity pure metal, and achieve low gas content in the steel liquid by vacuuming. The process is complicated and costly, which limits the production and application of 15-5PH alloy steel materials. In addition, during the casting process of electrode rods, due to the composition characteristics of 15-5PH stainless steel, the steel liquid is prone to segregation. The use of the commonly used ordinary electrode mold with the same upper and lower diameters is prone to produce deep shrinkage holes at the head of the electrode rod, and it is also easy to crack after the mold is opened.

[0033] Therefore, the present invention provides a method for manufacturing a 15-5PH stainless steel electrode rod, the method comprising:

[0034] (1) 15-5PH stainless steel liquid is prepared by electric furnace smelting (EAF) + vacuum oxygen decarburization (VOD) + LF process;

[0035] (2) pouring the molten steel into an electrode mold to obtain an electrode rod, wherein the electrode mold includes an ingot mold base and an ingot mold located on the ingot mold base, the ingot mold shape is a truncated cone with an upper bottom surface diameter smaller than a lower bottom surface diameter, the ingot mold inner cavity is a truncated cone with an upper end diameter larger than a lower end diameter, the central axis of the ingot mold inner cavity coincides with the central axis of the ingot mold outer shape, and the ingot mold inner cavity and the ingot mold outer shape have the same taper.

[0036] In the process of studying the preparation of 15-5PH stainless steel material, the inventor found that: unlike the commonly used vacuum induction + vacuum consumable smelting process, the electric furnace + VOD + LF + vacuum consumable smelting (VAR) process is used to prepare 15-5PH stainless steel material. Large-tonnage (more than 30 tons) electric furnaces can be used to produce more steel in the same time; and low-cost metal alloys can be used as raw materials. The metal is purified and impurities such as S and P are removed through the reaction between the slag on the surface of the molten steel and the molten steel. Then, by removing gas elements such as O and N in VOD, the ladle refining furnace LF further improves the cleanliness of the molten steel, and the electrode rod is obtained by casting in a cooling mold; after cleaning the surface of the electrode rod, vacuum consumable smelting is performed, and finally a consumable ingot is obtained, and then forging hot processing is performed to obtain the required rods, plates, etc.

[0037] Specifically, the metal alloy material used in the method of the present invention can be ferrochrome, ferroniobium, nickel plate, copper plate, ferromolybdenum and alloy high-quality scrap steel.

[0038] Specifically, calculated by mass percentage, the elements constituting the 15-5PH stainless steel include: C≤0.070%, Mn≤1.00%, Si≤1.00%, P≤0.030%, S≤0.015%, Cr 14.00~15.50%, Ni 3.50~5.50%, Cu 2.50~4.50%, Nb+Ta 5C (5 times the C content)~0.45%, Mo≤0.5%, and the balance is Fe.

[0039] Furthermore, calculated by mass percentage, the elements constituting the 15-5PH stainless steel include: C 0.03-0.05%, Mn 0.3-0.8%, Si 0.2-0.7%, P≤0.015%, S≤0.010%, Cr 14.50-15.30%, Ni3.50-5.20%, Cu 2.60-4.40%, Nb+Ta 5C-0.40%, Mo≤0.5%, and the balance is Fe.

[0040] Furthermore, in step (1), the electric furnace used for smelting in the present invention may be an electric arc furnace or / and a non-vacuum induction furnace, with a tonnage of 30 to 60 tons.

[0041] According to a preferred embodiment of the present invention, the electric furnace is a combination of an electric arc furnace and a non-vacuum induction furnace, and has a tonnage of 50 tons.

[0042] Furthermore, during the electric furnace smelting process, the metal is initially purified through the reaction between the slag on the surface of the molten steel and the molten steel to remove impurities such as S and P.

[0043] Furthermore, in order to control the element C in the 15-5PH stainless steel liquid to the target composition, remove H, N and volatile harmful elements, and make the temperature and composition of the molten steel uniform, the present invention adjusts the specific process operation and process parameters of the vacuum oxygen decarburization method (VOD), specifically: under vacuum conditions, argon and oxygen are used for composite blowing, the blowing temperature is 1580±10℃, the VOD limit vacuum is ≤67pa, and the over-blowing is 30Nm 3 .

[0044] According to a preferred embodiment of the present invention, the opening temperature of the VOD of the present invention can be 1570°C, 1575°C, 1580°C, 1585°C, or 1590°C.

[0045] Furthermore, in order to further deoxidize, desulfurize, remove inclusions in the molten steel, adjust the temperature of the molten steel, and provide temperature guarantee for subsequent operations, the present invention adjusts the specific process operations and process parameters in the ladle furnace refining (LF), specifically: refining temperature 1600±10°C, aluminum powder diffusion deoxidation, and maintaining the white slag time for 30 to 40 minutes.

[0046] According to a preferred embodiment of the present invention, the refining temperature of the LF of the present invention may be 1600°C, 1605°C, or 1610°C.

[0047] It should be noted that the casting mold of the electrode rod is called an electrode mold, and its function is to cool the molten steel to form an electrode rod for the subsequent vacuum consumable process.

[0048] The inventors found during the pouring of 15-5PH stainless steel liquid that the cooling process of the electrode mold is crucial to the formation of the electrode rod. When pouring 15-5PH stainless steel liquid using the currently commonly used ordinary electrode mold with the same upper and lower diameters, due to its composition characteristics, the molten steel is prone to segregation, and deep shrinkage holes are easily produced at the head of the electrode rod, and it is also easy to crack after the mold is opened.

[0049] It should be noted that due to the high alloy composition of 15-5PH (>25%), the solid-state specific gravity of the molten steel formed successively during the cooling process is very different, which is easy to form segregation; the existing electrode mold has a large height-to-diameter ratio of up to 5.86, and the head that finally solidifies lacks timely replenishment of liquid molten steel, which is easy to form shrinkage cavities; in addition, a solid quenching layer is formed on the outer layer of the electrode during the solidification process. If the quenching layer of the molten steel at the head is thicker, there will not be enough molten steel to compensate for the shrinkage in the final shrinkage compensation process, resulting in larger shrinkage cavities and cracks.

[0050] In view of the above problems, the inventors have designed a new type of special-shaped electrode mold, the structure of which is as follows: Figure 1As shown; the shape of the electrode mold ingot mold is a frustum that is small on the top and large on the bottom, and the inner cavity of the electrode mold ingot mold is a frustum that is large on the top and small on the bottom. The purpose of this is to allow the bottom to cool quickly, while the head retains relatively more molten steel for the final shrinkage compensation; the diameter of the electrode rod head obtained by casting is larger, the proportion of liquid phase in the solidification process is large, and the shrinkage compensation will be more sufficient.

[0051] Specifically, in the present invention, in step (2), the central axis of the inner cavity of the ingot mold coincides with the central axis of the outer shape of the ingot mold and has the same taper to achieve uniformity in the cooling and solidification process of the poured molten steel.

[0052] Furthermore, in the actual production process, depending on the process conditions and equipment capabilities, in step (2), the height of the ingot mold is generally 3000 mm to 4500 mm. If the ingot mold is too low, the cast electrode rod will be too small and an electrode rod of sufficient weight will not be obtained; if the ingot mold is too high, the shape of the electrode rod will be unsatisfactory and demolding will be difficult.

[0053] According to a preferred embodiment of the present invention, the heights of the ingot molds are 3000 mm, 3500 mm, 4000 mm, and 4500 mm, respectively.

[0054] It should be noted that in order to control the cooling rate of the poured molten steel to decrease successively from the bottom to the head, to ensure that the electrode rods are cooled and solidified sequentially from the bottom to the head during the molten steel pouring process, and to ensure that when the lower layer of molten steel solidifies, there is always unsolidified molten steel in the upper layer to supplement the shrinkage holes that appear when the lower layer of molten steel solidifies, the thickness of the ingot mold decreases successively from the bottom to the head, and under the condition of the same taper, the overall thickness of the ingot mold will increase with the increase of the ingot mold height.

[0055] It should be noted that in order to prevent cracks from appearing on the electrode rod after demoulding, the present invention controls the mold-ingot ratio (electrode mold weight / steel ingot weight) during the molten steel pouring process.

[0056] Specifically, the mold-ingot ratio in the process of pouring molten steel of the present invention is 1.0 to 1.3, such as 1.0, 1.12, 1.15, 1.18, 1.2, 1.23, 1.25, 1.28, 1.3. The material constituting the electrode mold can be ductile iron or gray cast iron, which is conducive to keeping the cavity from deforming during use. If the mold-ingot ratio is too small, the solidification time will be prolonged and the cast structure will be seriously segregated. If the mold-ingot ratio is too large, the casting will be discontinuous due to rapid solidification.

[0057] Furthermore, the material of the electrode mold of the present invention is ductile iron.

[0058] It should be noted that in order to meet the requirements of the consumable electrode on the internal quality, the present invention needs to control the taper of the electrode mold ingot mold.

[0059] Specifically, the taper of the electrode mold ingot mold of the present invention is 1.1-1.25%, such as 1.1%, 1.12%, 1.14%, 1.15%, 1.16%, 1.17%, 1.18%, 1.19%, 1.20%, 1.21%, 1.22%, 1.23%, 1.24%, 1.25%. If the taper is too small, it will cause demoulding difficulties. If the taper is too large, it will cause a large amount of electrode surface treatment, increasing the loss of metal materials.

[0060] According to a preferred embodiment of the present invention, in step (2), when the mold-ingot ratio is 1.25 and the taper is 1.1%, when the ingot mold height is 3600 mm, the thickness of the ingot mold from the head to the bottom increases from 80 mm to 120 mm. If the bottom of the ingot mold is too thin, the quenching layer formed at the bottom after pouring the molten steel is too thin, and the rapid cooling of the bottom molten steel cannot be achieved. The cooling and solidification time of the bottom molten steel is prolonged, which easily leads to confusion in the cooling and solidification sequence of the electrode rod from the bottom to the head. The upper molten steel that solidifies first cannot supplement the shrinkage cavity that appears when the lower molten steel solidifies, causing cracks in the electrode rod; if the head of the ingot mold is too thick, the quenching layer formed at the head after pouring the molten steel is too thick, resulting in a decrease in the proportion of liquid phase, affecting the final molten steel shrinkage compensation.

[0061] According to a preferred embodiment of the present invention, the special-shaped electrode mold of the present invention is used to pour molten steel. During the molten steel pouring process, the electrode rod can be cooled and solidified sequentially from the bottom to the head, and in the direction from the bottom to the head, the quenching layer formed on the electrode rod becomes thinner and the proportion of liquid phase increases, thereby ensuring that there is enough molten steel to compensate for shrinkage, avoiding defects such as shrinkage cavities and cracks in the produced electrode rod, and improving the product yield while reducing production costs.

[0062] It should be noted that in order to improve the solid quenching layer formed on the outer layer of the electrode rod during the solidification of the molten steel as a whole and prevent the electrode rod from cracking, the present invention needs to limit the process parameters during the casting process.

[0063] Specifically, in step (2), the pouring process parameters are as follows: the pouring speed is 0.6-0.7 t / min, and the temperature is 40-50° C. above the melting point of 15-5PH stainless steel, wherein the melting point of 15-5PH stainless steel is 1466±5° C. If the pouring temperature is too high, the chill layer will be thin and the steel ingot will be prone to thermal cracking. If the pouring temperature is too low, the inclusions will not be fully removed and short or irregular lengths will be likely to appear.

[0064] According to a preferred embodiment of the present invention, the pouring speeds may be 0.6 t / min, 0.62 t / min, 0.64 t / min, 0.66 t / min, 0.68 t / min, and 0.7 t / min, respectively; and the temperatures may be 1500° C. and 1510° C., respectively.

[0065] The present invention controls the cooling speed of the poured molten steel and the thickness of the chilled layer by adjusting the size of the electrode mold and the pouring process parameters, so as to ensure that during the pouring process of the molten steel, when the lower layer of molten steel solidifies, there is always unsolidified molten steel in the upper layer, which supplements the shrinkage holes that appear when the lower layer of molten steel solidifies and increases the proportion of the upper liquid phase; in particular, the head portion is kept at the thinnest chilled layer, ensuring a larger proportion of the liquid phase and achieving the final solidification. Compared with the prior art, the electrode rod ingot body formed by the method of the present invention will not have cracks, and the internal structure is dense, which fully meets the quality requirements of consumable remelting for consumable electrodes.

[0066] It should be noted that in order to make the heat dissipation of the electrode rod head slower during the solidification process, the present invention installs and embeds a layer of insulating riser on the top of the special-shaped electrode mold, further increasing the final liquid phase ratio, making the final molten steel shrinkage more sufficient, avoiding shrinkage holes in the electrode rod, and improving the product yield rate.

[0067] Specifically, in step (2), a layer of insulating riser is embedded in the top of the inner cavity of the ingot mold along the circumferential direction, the height of the insulating riser is 350-400 mm, the thickness is 40-50 mm, and the thickness of the insulating riser is consistent.

[0068] The invention also discloses a 15-5PH stainless steel electrode rod, which is made by the method.

[0069] Specifically, calculated by mass percentage, the elements constituting the 15-5PH stainless steel include: C≤0.070%, Mn≤1.00%, Si≤1.00%, P≤0.030%, S≤0.015%, Cr 14.00~15.50%, Ni 3.50~5.50%, Cu 2.50~4.50%, Nb+Ta 5C (5 times the C content)~0.45%, Mo≤0.5%, and the balance is Fe.

[0070] Furthermore, calculated by mass percentage, the elements constituting the 15-5PH stainless steel include: C 0.03-0.05%, Mn 0.3-0.8%, Si 0.2-0.7%, P≤0.015%, S≤0.010%, Cr 14.50-15.30%, Ni3.50-5.20%, Cu 2.60-4.40%, Nb+Ta 5C-0.40%, Mo≤0.5%, and the balance is Fe.

[0071] The 15-5PH stainless steel electrode rod prepared by the above method has a truncated cone shape, a height of 3500-4000 mm (such as 3500 mm, 3570 mm, 3670 mm, 3680 mm, 3700 mm), and no macroscopic defects such as cracks and shrinkage cavities on the surface. Figure 2 shown.

[0072] Through consumable remelting verification, the process melting rate temperature and product inspection index of the 15-5PH stainless steel electrode rod prepared by the method of the present invention meet the quality requirements of the stainless steel. In this field, the present invention is the first to produce 15-5PH stainless steel material through the EAF+VOD+LF-VAR single vacuum process. Compared with the existing high-cost vacuum induction + vacuum consumable smelting process, the material properties are kept at the same level and the production cost is reduced.

[0073] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0074] The material of the electrode mold in the embodiment and the comparative example is ductile iron.

[0075] Example 1

[0076] The method for preparing a 15-5PH stainless steel electrode rod 1 comprises:

[0077] (1) according to the proportion, alloy raw materials including ferrochrome, ferroniobium, nickel plate, copper plate, ferromolybdenum and high-quality scrap steel are used to prepare 15-5PH stainless steel liquid 1 through electric furnace smelting + VOD + LF process;

[0078] Among them, the electric furnace smelting process parameters are: oxygen C ≥ 0.05%, P ≤ 0.003%;

[0079] VOD process parameters: opening temperature 1580℃, ultimate vacuum 65pa, overblow 30Nm 3 ;

[0080] LF process parameters: refining temperature 1600℃, aluminum powder diffusion deoxidation, white slag holding time 35min;

[0081] After testing, according to the calculation of mass percentage, the elements constituting the 15-5PH stainless steel liquid 1 include: C 0.035%, Mn 0.63%, Si 0.36%, P≤0.015%, S≤0.001%, Cr 14.75%, Ni 4.96%, Cu 3.4%, Nb+Ta0.30%, Mo 0.3%, the balance is Fe, and the impurity content is controlled within the required range;

[0082] (2) The molten steel obtained in step (1) is poured into a special-shaped electrode mold at a pouring temperature of 1510° C. and a pouring speed of 0.6 t / min to obtain a 15-5PH stainless steel electrode rod 1, wherein the structural schematic diagram of the special-shaped electrode mold is as shown in Figure 1 As shown in (a), the height is 3600 mm, the taper of the ingot mold inner cavity and the ingot mold outer shape is 1.1%, and the mold-to-ingot ratio is 1.25.

[0083] After measurement, the height of the 15-5PH stainless steel electrode rod 1 is 3500mm. After observation, the appearance of the 15-5PH stainless steel electrode rod 1 is visually inspected without cracks, and no shrinkage cavity is found after the head is sawed 300mm. Figure 2 shown.

[0084] Example 2

[0085] The 15-5PH stainless steel electrode rod 2 was prepared in the same manner as in Example 1, except that:

[0086] In step (2), the molten steel obtained in step (1) is poured into a special-shaped electrode mold, and the height of the special-shaped electrode mold is 4000 mm.

[0087] After testing, calculated based on mass percentage, the elements constituting 15-5PH stainless steel liquid 2 include: C 0.036%, Mn 0.66%, Si 0.37%, P≤0.015%, S≤0.001%, Cr 14.65%, Ni 4.90%, Cu 3.35%, Nb+Ta 0.30%, Mo 0.21%, and the balance is Fe. The impurity content is controlled within the required range.

[0088] After measurement, the height of the 15-5PH stainless steel electrode rod 2 is 3700 mm; after observation, the 15-5PH stainless steel electrode rod 2 has no cracks in visual inspection, and no shrinkage cavity is found after the head is sawed 320 mm.

[0089] Example 3

[0090] The 15-5PH stainless steel electrode rod 3 was prepared in the same manner as in Example 2, except that:

[0091] In step (1), VOD process parameters: opening temperature 1570°C, VCD ultimate vacuum 65pa, overblow 30Nm 3 ;

[0092] LF process parameters: refining temperature 1610℃, aluminum powder diffusion deoxidation, white slag holding time 40min; 15-5PH stainless steel liquid 3 is obtained by smelting;

[0093] After testing, calculated based on mass percentage, the elements constituting 15-5PH stainless steel liquid 3 include: C 0.037%, Mn 0.67%, Si 0.38%, P≤0.015%, S≤0.001%, Cr 14.70%, Ni 4.92%, Cu 3.35%, Nb+Ta 0.30%, Mo 0.20%, and the balance is Fe. The impurity content is controlled within the required range.

[0094] In step (2), a layer of heat-insulating riser is embedded in the top of the inner cavity of the special-shaped electrode mold along the circumferential direction, and the height of the heat-insulating riser is 300 mm and the thickness is 40 mm. Figure 1 As shown in (b), after casting, a 15-5PH stainless steel electrode rod 3 is obtained.

[0095] The measurement shows that the height of the 15-5PH stainless steel electrode rod 3 is 3680 mm. The observation shows that the 15-5PH stainless steel electrode rod 3 has no cracks in visual inspection, and no shrinkage cavity is found after the head is sawed 310 mm.

[0096] Example 4

[0097] The 15-5PH stainless steel electrode rod 4 was prepared in the same manner as in Example 2, except that:

[0098] Change the VOD process parameters in step (1): opening temperature 1580℃, VCD ultimate vacuum 65pa, overblow 30Nm 3 .

[0099] LF process parameters: refining temperature 1610℃, aluminum powder diffusion deoxidation, white slag holding time 30min.

[0100] After testing, according to the calculation of mass percentage, the elements constituting 15-5PH stainless steel liquid 4 include: C 0.032%, Mn 0.60%, Si 0.32%, P≤0.015%, S≤0.001%, Cr 14.58%, Ni 4.90%, Cu 3.3%, Nb+Ta0.30%, Mo 0.22%, the balance is Fe, and the impurity content is controlled within the required range;

[0101] After casting, a 15-5PH stainless steel electrode rod 4 is obtained.

[0102] After measurement, the height of the 15-5PH stainless steel electrode rod 4 is 3670 mm. After observation, the 15-5PH stainless steel electrode rod 4 has no cracks in visual inspection, and no shrinkage cavity is found after the head is sawed 320 mm.

[0103] Example 5

[0104] The 15-5PH stainless steel electrode rod 5 was prepared in the same manner as in Example 1, except that:

[0105] The temperature of the molten steel pouring in step (2) is changed to 1510° C. and the pouring speed is changed to 0.7 t / min to obtain a 15-5PH stainless steel electrode rod 5;

[0106] After measurement, the height of the 15-5PH stainless steel electrode rod 5 is 3500 mm; after observation, the 15-5PH stainless steel electrode rod 5 has no cracks in visual inspection, and no shrinkage cavity is found after the head is sawed 300 mm.

[0107] Comparative Example 1

[0108] (1) According to the proportion, pure metal raw materials with a purity of more than 99.5% are used, including: pure metal Fe, pure metal Ni, pure metal Cr, electrode carbon (pure C), pure metal Mo, pure metal Cu, pure metal Nb, pure Mn and pure Si, and a vacuum induction method is used to prepare 15-5PH stainless steel liquid 6, and the specific operation is: the vacuum degree during the vacuum refining period meets ≤5Pa, and the holding time is ≥60min; the electromagnetic stirring time is not less than 20min; the full melting temperature is 1500°C;

[0109] After testing, according to the calculation of mass percentage, the elements constituting 15-5PH stainless steel liquid 6 include: C 0.037%, Mn 0.66%, Si 0.36%, P≤0.015%, S≤0.001%, Cr 14.77%, Ni 4.95%, Cu 3.35%, Nb+Ta 0.30%, Mo 0.14%, the balance is Fe, and the impurity content is controlled within the required range;

[0110] (2) Using a conventional electrode mold to cast the molten steel 6 obtained in step (1), wherein the structure and size parameters of the conventional electrode mold are as follows: Figure 3 As shown, the same casting process parameters as those in step (2) of Example 1 are used: the casting temperature is 1510° C., the casting speed is 0.6 t / min, and a 15-5PH stainless steel electrode rod 6 is obtained.

[0111] After measurement, the height of 15-5PH stainless steel electrode rod 6 is 3500mm; after observation, the appearance of 15-5PH stainless steel electrode rod 6 has many cracks, and deep shrinkage holes are still found after sawing 1500mm at the head. Figure 4 As shown, unqualified.

[0112] Comparative Example 2

[0113] The 15-5PH stainless steel electrode rod 7 was prepared by the same method as in Example 1, except that the electric furnace smelting process parameters in step (1) were changed, and the VOD process parameters were: opening temperature 1560°C, VOD ultimate vacuum 65Pa, overblow 30Nm 3 , and obtain 15-5PH stainless steel liquid 7.

[0114] After testing, calculated based on mass percentage, the elements constituting 15-5PH stainless steel liquid 7 include: C 0.080%, Mn 0.66%, Si 0.36%, P 0.035%, S 0.025%, Cr 14.77%, Ni 4.95%, Cu 3.55%, Nb+Ta0.35%, Mo 0.14%, and the balance is Fe. The impurity contents of P and S are not within the required range.

[0115] After the casting process in step (2), a 15-5PH stainless steel electrode rod 7 is finally obtained.

[0116] After measurement, the height of the 15-5PH stainless steel electrode rod 7 is 3500mm; after observation, the 15-5PH stainless steel electrode rod 7 has no cracks in visual inspection, and no obvious shrinkage hole is found after the head is sawed 350mm.

[0117] Comparative Example 3

[0118] A 15-5PH stainless steel electrode rod 8 is prepared by the same method as in Example 1, except that in step (1), the LF process parameters are: refining temperature 1620°C, aluminum powder diffusion deoxidation, and white slag holding time 30 to 40 minutes to obtain 15-5PH stainless steel liquid 8.

[0119] After testing, calculated based on mass percentage, the elements that make up 15-5PH stainless steel liquid 8 include: C 0.020%, Mn 0.06%, Si 0.03%, P 0.005%, S 0.0010%, Cr 14.07%, Ni 4.95%, Cu 2.55%, Nb+Ta0.20%, Mo 0.12%, and the balance is Fe. The contents of elements such as Cr and Cu are lower than the lower limit of the material composition range and are not within the required range.

[0120] After the casting process in step (2), a 15-5PH stainless steel electrode rod 8 is finally obtained.

[0121] The height of the 15-5PH stainless steel electrode rod 8 was measured to be 3500 mm. After visual inspection, the appearance of the 15-5PH stainless steel electrode rod 8 was found to be free of cracks, and no obvious shrinkage holes were found after the head was sawed off by 360 mm.

[0122] Comparative Example 4

[0123] A 15-5PH stainless steel electrode rod 9 is prepared by the same method as in Example 1, except that the temperature of the molten steel pouring in step (2) is changed to 1530° C. and the pouring speed is changed to 0.6 t / min, thereby obtaining a 15-5PH stainless steel electrode rod 9;

[0124] Upon observation, the 15-5PH stainless steel electrode rod 9 was found to have cracks in its appearance. After sawing the head to 1000mm, deep shrinkage holes were still found, indicating that it was unqualified.

[0125] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for manufacturing a 15-5PH stainless steel electrode rod, characterized in that: The method comprises: (1) Preparing 15-5PH stainless steel liquid by electric furnace smelting + VOD + LF process; (2) pouring the molten steel into an electrode mold to obtain an electrode rod, wherein the electrode mold includes an ingot mold base and an ingot mold located on the ingot mold base, the ingot mold shape is a truncated cone with an upper bottom surface diameter smaller than a lower bottom surface diameter, the ingot mold inner cavity is a truncated cone with an upper end diameter larger than a lower end diameter, the central axis of the ingot mold inner cavity coincides with the central axis of the ingot mold outer shape, and the ingot mold inner cavity and the ingot mold outer shape have the same taper.

2. The manufacturing method according to claim 1, characterized in that: Calculated by mass percentage, the elements constituting the 15-5PH stainless steel include: C≤0.070%, Mn≤1.00%, Si≤1.00%, P≤0.030%, S≤0.015%, Cr14.00~15.50%, Ni 3.50~5.50%, Cu2.50~4.50%, Nb+Ta 5C~0.45%, Mo≤0.5%, and the balance is Fe.

3. The manufacturing method according to claim 1, characterized in that: In step (1), the tonnage of the electric furnace is 30 to 60 tons, and the raw material is a metal alloy.

4. The manufacturing method according to claim 1, characterized in that: VOD process parameters: opening temperature 1580±10℃, VCD ultimate vacuum ≤67pa, overblow 30Nm 3 .

5. The manufacturing method according to claim 1, characterized in that: The process parameters of LF are as follows: refining temperature 1600±10℃, aluminum powder diffusion deoxidation, and white slag keeping time 30-40min.

6. The manufacturing method according to claim 1, characterized in that: In step (2), the height of the ingot mold is 3000-4500 mm, and the median diameter of the inner cavity of the ingot mold is 580 mm.

7. The manufacturing method according to claim 1, characterized in that: In step (2), the taper of the ingot mold is 1.1 to 1.25%.

8. The manufacturing method according to claim 1, characterized in that: In step (2), the pouring process parameters are: mold-ingot ratio of 1.0 to 1.3, pouring speed of 0.6 to 0.7 t / min, and pouring temperature of 40 to 50° C. higher than the melting point of the 15-5PH stainless steel.

9. The manufacturing method according to claim 1, characterized in that: In step (2), a layer of insulating riser is embedded in the top of the inner cavity of the ingot mold along the circumferential direction, and the height of the insulating riser is 300-350 mm and the thickness is 40-50 mm.

10. A 15-5PH stainless steel electrode rod, characterized in that: The electrode rod is made by the method according to any one of claims 1 to 9.

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