CN114107780B - Smelting process for improving strength of maraging stainless steel - Google Patents
Smelting process for improving strength of maraging stainless steel Download PDFInfo
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- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
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- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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Abstract
The invention discloses a smelting process for improving the strength of maraging stainless steel, which comprises the working procedures of smelting in a vacuum induction furnace, forging before electroslag and electroslag remelting in protective atmosphere; the smelting process of the vacuum induction furnace comprises the following steps: putting raw materials of Fe, cr, ni and Mo into an induction furnace, adding the raw materials of Cu, si, mn, V, nb and C after the materials are completely melted in the furnace, adding the raw materials of Ti and Al after the materials are completely melted again, tapping after molten steel is completely melted and uniform, and casting into steel ingots; the electroslag pre-forging process comprises the following steps: heating the steel ingot and forging the steel ingot into a round bar; the protective atmosphere electroslag remelting process comprises the following steps: and adding the round bar steel ingot and the pre-melted slag into an electroslag furnace for electroslag remelting. The process has the effects of refining the grain size and purifying the grain boundary, and the material strength is improved together; so that the Ti and Al easily-consumed elements can be stably controlled in the required component range in the process; the obtained product has the characteristic of high strength, and is suitable for medical instruments such as medical suture needles and the like.
Description
Technical Field
The invention relates to a smelting process of stainless steel, in particular to a smelting process for improving the strength of maraging stainless steel.
Background
The maraging stainless steel is high-strength stainless steel strengthened by superposing two strengthening effects of low-carbon martensitic transformation strengthening and aging strengthening, has the advantages of high strength, good plasticity and toughness, good anti-overaging property, corrosion resistance, easiness in processing, good thermal stability and the like, is fully applied to the fields of aerospace, instrument molds and the like, and has good development prospect.
The prior medical instruments mainly adopt chromium-containing martensitic steels AISI420 and 300 series austenitic stainless steels, but the materials can not completely meet the requirements of some medical instruments, such as suture needles, dental files, reaming files and fine bone drills. Although the chromium-containing martensitic steel has good workability in the as-supplied state, its toughness is poor. Austenitic stainless steels, on the other hand, need to be delivered in the cold worked state in order to achieve the required strength, resulting in poor workability when working the final product.
Disclosure of Invention
The invention aims to provide a smelting process for improving the strength of maraging stainless steel, and the product can be used as steel for medical instruments.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the method comprises the working procedures of smelting in a vacuum induction furnace, forging before electroslag and remelting in protective atmosphere electroslag;
the smelting process of the vacuum induction furnace comprises the following steps: putting raw materials of Fe, cr, ni and Mo into an induction furnace, adding the raw materials of Cu, si, mn, V, nb and C after the materials are completely melted in the furnace, adding the raw materials of Ti and Al after the materials are completely melted again, tapping after molten steel is completely melted and uniform, and casting into steel ingots;
the electroslag pre-forging process comprises the following steps: heating the steel ingot and forging the steel ingot into a round bar;
the protective atmosphere electroslag remelting process comprises the following steps: adding a round bar steel ingot and premelting slag into an electroslag furnace, and carrying out electroslag remelting; the pre-melted slag comprises the following main components in percentage by weight: 22 to 22.5 weight percent of CaO and Al 2 O 3 20.5wt%～211wt%、MgO 2.5wt%～3wt%、TiO 2 2 to 2.5 weight percent, and the balance of CaF 2 (ii) a And adding TiO with the weight of 5-7% of the pre-melted slag 2 2.0-3.0% of MgO and Al particles;
the maraging stainless steel comprises the following components in percentage by mass: less than or equal to 0.02 percent of C, 11.0 to 13.0 percent of Cr, 8.0 to 10.0 percent of Ni, 4.0 to 5.0 percent of Mo, 1.5 to 2.5 percent of Cu, 0.5 to 1.2 percent of Ti, 0.15 to 0.5 percent of Al, 0.3 to 0.5 percent of Si, 0.3 to 0.5 percent of Mn, less than or equal to 0.3 percent of V, less than or equal to 0.3 percent of Nb, and the balance of Fe and inevitable impurities.
In the smelting process of the vacuum induction furnace, molten steel is tapped at the temperature of 1500-1550 ℃, and the pouring temperature is 1480-1500 ℃.
In the pre-electroslag forging process, the heating temperature is 1160-1180 ℃, the heat preservation time is not less than 4 hours, and the final forging temperature is more than or equal to 850 ℃.
In the protective atmosphere electroslag remelting process, al particles are added in three batches, namely, the Al particles are uniformly mixed with premelting slag, added in the electroslag smelting process and added before feeding.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: the method adopts the method of increasing the content of a key strengthening element Ti and adding a certain amount of V and Nb elements, which play roles in refining the grain size and purifying the grain boundary and realize the improvement of the material strength together; in the process of electroslag remelting in protective atmosphere, a proper amount of TiO is added into premelting slag 2 MgO and Al particles, thereby enabling Ti and Al easily-consumed elements to be stably controlled in a required component range in the process; according to the invention, fe-Cr-Ni is used as a matrix, mo, cu, ti, al, si, mn, V and Nb are used as reinforcing elements, and the obtained product has the characteristic of high strength through the control of a smelting process, and is suitable for medical instruments such as medical suture needles and the like.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments.
The smelting process for improving the strength of the maraging stainless steel comprises the working procedures of smelting in a vacuum induction furnace, forging before electroslag and electroslag remelting in protective atmosphere; the process of each procedure is as follows:
(1) The maraging stainless steel comprises the following components in percentage by mass: less than or equal to 0.02 percent of C, 11.0 to 13.0 percent of Cr, 8.0 to 10.0 percent of Ni, 4.0 to 5.0 percent of Mo, 1.5 to 2.5 percent of Cu, 0.5 to 1.2 percent of Ti, 0.15 to 0.5 percent of Al, 0.3 to 0.5 percent of Si, 0.3 to 0.5 percent of Mn, less than or equal to 0.3 percent of V, less than or equal to 0.3 percent of Nb, and the balance of Fe and inevitable impurities. Among the above components, ti is preferably 1.1 to 1.2%, V is preferably 0.15 to 0.25% by weight, and Nb is preferably 0.15 to 0.25% by weight.
(2) Preparing materials: the burden calculation and the accurate weighing of the charging amount of the furnace burden are carried out correctly, a small amount of refining slag is paved at the bottom of the furnace, all pure iron, nickel plates, metal chromium and ferromolybdenum are added, and a small amount of refining slag is added at the top of the furnace according to the sequence of pure iron-alloy-pure iron. The cloth should: the lower part is compact and the upper part is loose. The raw materials of other alloy elements Cu, si, mn, V, nb and C are loaded into a first vacuum hopper, and the raw materials of Ti and Al are loaded into a second vacuum hopper.
(3) Smelting in a vacuum induction furnace: and ensuring the vacuum induction degree of the smelting furnace in the smelting process, performing electric melting, adding the alloy in the first vacuum induction furnace after the charging in the furnace is completely melted, adding the alloy in the second vacuum hopper after the charging in the furnace is completely melted again, tapping at the molten steel temperature of 1500-1550 ℃, and casting into round ingots at the casting temperature of 1480-1500 ℃.
(4) Forging before electroslag: heating by an electric furnace, keeping the temperature at 1160-1180 ℃ for not less than 4h, forging after heat preservation, keeping the temperature at the final forging temperature at more than or equal to 850 ℃ for 30-40 min during each heating, and forging into round bars with matched sizes according to the requirements of electroslag equipment.
Preferably, in the forging procedure, the heating temperature is 1170-1180 ℃, the heat preservation time is 4-4.5 h, and the finish forging temperature is controlled at 850-880 ℃.
(5) Electroslag remelting in protective atmosphere: adding a round bar steel ingot and pre-melted slag into an electroslag furnace, and carrying out electroslag remelting; selecting the corresponding pre-melted slag main components according to the components of the cast ingot as follows: 22 to 22.5wt% CaO, 20.5 to 21wt% Al 2 O 3 、2.5wt%～3wt%MgO、2wt%～2.5wt%TiO 2 The balance being CaF 2 (ii) a Preferably CaF 2 51wt%、CaO 22wt%、Al 2 O 3 21wt%、MgO 2.5wt%、TiO 2 2wt%. In order to better protect the contents of elements Ti and Al, the pre-melted slag is improved as follows: tiO with the weight of 5-7 percent of the pre-melted slag is additionally added on the basis of the total amount of the original pre-melted slag 2 2.0-3.0% of MgO and a certain amount of Al particles, preferably 6% of TiO 2 And 2.5% of MgO. The Al particles are added in three batches, and one part of the Al particles is uniformly mixed with the premelting slag, and the weight of the Al particles is 0.15 to 0.25 percent of the weight of the original premelting slag, preferably 0.2 percent; one part is added with the round bar steel ingot with the weight of 0.15-0.25 percent, preferably 0.2 percent, in the electroslag smelting process; the last batch is added with the weight of 0.3-0.5 percent of the weight of the original premelting slag before feeding, and the weight is preferably 0.4 percent. The full process ensures the sufficiency of the protective atmosphere argon.
(6) Mechanical properties: the maraging stainless steel is obtained without adopting the smelting process and by adopting the smelting process for improving the strength; then forged and rolled to be a wire rod with the diameter of 5.5 mm, and the tensile strength of the wire rod is 720 MPa-765 MPa.
Examples 1 to 6: the smelting process for improving the strength of the maraging stainless steel is specifically as follows.
(1) Smelting in a 50kg vacuum induction furnace and forging before electroslag: the specific process parameters of the examples using the above process are shown in table 1.
Table 1: technological parameters of vacuum induction furnace smelting and electroslag pre-forging
(2) Electroslag remelting in protective atmosphere: principal constituent of premelting slag and TiO 2 The amounts of MgO and Al particles added are shown in Table 2.
Table 2: principal Components (wt%, g) of the premelted slag
The addition ratio of Al particles in table 2 is illustrated in example 1, and is: 0.2 percent of the weight of the original premelting slag, 0.2 percent of the round bar steel ingot and 0.4 percent of the weight of the original premelting slag.
(3) The chemical composition of the maraging stainless steel obtained in each example is shown in table 3.
Table 3: chemical composition (wt%) of the obtained maraging stainless steel
(4) The tensile strength of the maraging stainless steel wire rod of phi 5.5 obtained in each example is shown in Table 4.
Table 4: tensile strength (MPa) of the obtained maraging stainless steel wire rod phi 5.5
Claims (3)
1. A smelting process for improving the strength of maraging stainless steel is characterized by comprising the following steps: the method comprises the working procedures of smelting in a vacuum induction furnace, forging before electroslag and remelting in protective atmosphere electroslag;
the smelting process of the vacuum induction furnace comprises the following steps: putting raw materials of Fe, cr, ni and Mo into an induction furnace, adding the raw materials of Cu, si, mn, V, nb and C after the materials are completely melted in the furnace, adding the raw materials of Ti and Al after the materials are completely melted again, tapping after molten steel is completely melted and uniform, and casting into steel ingots;
the electroslag pre-forging process comprises the following steps: heating the steel ingot and forging the steel ingot into a round bar;
the protective atmosphere electroslag remelting process comprises the following steps: adding a round bar steel ingot and premelting slag into an electroslag furnace, and carrying out electroslag remelting; the pre-melted slag comprises the following main components in percentage by weight: 22 to 22.5 weight percent of CaO and Al 2 O 3 20.5wt%～21wt%、MgO 2.5wt%～3wt%、TiO 2 2 to 2.5 weight percent, and the balance of CaF 2 (ii) a And adding TiO with the weight of 5-7% of the pre-melted slag 2 2.0-3.0% of MgO and Al particles; the Al particles are added in three batches, and one part of the Al particles is uniformly mixed with the premelting slag, and the weight of the Al particles is 0.15-0.25% of the weight of the original premelting slag; one part of the slag is added in the electroslag smelting process,the weight of the round bar steel ingot is 0.15-0.25 percent; the last batch is added before feeding, and the weight of the last batch is 0.3 to 0.5 percent of the weight of the original premelting slag;
the maraging stainless steel comprises the following components in percentage by mass: less than or equal to 0.02 percent of C, 11.0 to 13.0 percent of Cr, 8.0 to 10.0 percent of Ni, 4.0 to 5.0 percent of Mo, 1.5 to 2.5 percent of Cu, 0.5 to 1.2 percent of Ti, 0.15 to 0.5 percent of Al, 0.3 to 0.5 percent of Si, 0.3 to 0.5 percent of Mn, less than or equal to 0.3 percent of V, less than or equal to 0.3 percent of Nb, and the balance of Fe and inevitable impurities.
2. The smelting process for improving the strength of maraging stainless steel according to claim 1, wherein the smelting process comprises the following steps: in the smelting process of the vacuum induction furnace, molten steel is tapped at the temperature of 1500-1550 ℃, and the pouring temperature is 1480-1500 ℃.
3. The smelting process for improving the strength of maraging stainless steel according to claim 1 or 2, characterized in that: in the forging process before electroslag, the heating temperature is 1160-1180 ℃, the heat preservation time is not less than 4h, and the final forging temperature is not less than 850 ℃.
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