CN115369304A - Preparation method of stainless steel material and stainless steel material - Google Patents
Preparation method of stainless steel material and stainless steel material Download PDFInfo
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- CN115369304A CN115369304A CN202210998502.2A CN202210998502A CN115369304A CN 115369304 A CN115369304 A CN 115369304A CN 202210998502 A CN202210998502 A CN 202210998502A CN 115369304 A CN115369304 A CN 115369304A
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- 239000010935 stainless steel Substances 0.000 title claims abstract description 136
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 136
- 239000000463 material Substances 0.000 title claims abstract description 99
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- 238000005242 forging Methods 0.000 claims abstract description 87
- 238000000034 method Methods 0.000 claims abstract description 68
- 238000005204 segregation Methods 0.000 claims abstract description 41
- 230000007547 defect Effects 0.000 claims abstract description 31
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 27
- 238000009792 diffusion process Methods 0.000 claims abstract description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 20
- 238000007711 solidification Methods 0.000 claims abstract description 20
- 230000008023 solidification Effects 0.000 claims abstract description 20
- 238000000265 homogenisation Methods 0.000 claims abstract description 19
- 235000011837 pasties Nutrition 0.000 claims abstract description 7
- 238000005096 rolling process Methods 0.000 claims abstract description 7
- 238000003723 Smelting Methods 0.000 claims abstract description 6
- 230000000116 mitigating effect Effects 0.000 claims abstract description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 34
- 239000010959 steel Substances 0.000 claims description 34
- 238000001816 cooling Methods 0.000 claims description 25
- 239000013078 crystal Substances 0.000 claims description 22
- 239000001307 helium Substances 0.000 claims description 14
- 229910052734 helium Inorganic materials 0.000 claims description 14
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 14
- 238000005520 cutting process Methods 0.000 claims description 13
- 239000007789 gas Substances 0.000 claims description 12
- 238000004321 preservation Methods 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 9
- 229910045601 alloy Inorganic materials 0.000 claims description 6
- 239000000956 alloy Substances 0.000 claims description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 238000009826 distribution Methods 0.000 abstract description 6
- 238000005266 casting Methods 0.000 description 13
- 206010040844 Skin exfoliation Diseases 0.000 description 9
- 210000001787 dendrite Anatomy 0.000 description 6
- 230000000087 stabilizing effect Effects 0.000 description 6
- 239000011651 chromium Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000001953 recrystallisation Methods 0.000 description 3
- 206010014970 Ephelides Diseases 0.000 description 2
- 208000003351 Melanosis Diseases 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000007667 floating Methods 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 229910001338 liquidmetal Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000000112 cooling gas Substances 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
- B21J5/002—Hybrid process, e.g. forging following casting
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- 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
- C22B9/04—Refining by applying a vacuum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- 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
- C22B9/16—Remelting metals
- C22B9/20—Arc remelting
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- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
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Abstract
The application provides a preparation method of a stainless steel material and the stainless steel material, which comprises the following steps: step (1): preparing a stainless steel blank by adopting a duplex process of vacuum smelting and vacuum self-consumption, and reducing component segregation by controlling solidification parameters; mitigating compositional segregation via solidification parameter control comprises: controlling the maximum molten pool depth of a pasty zone of the consumable blank by controlling a current-voltage ratio so as to further reduce component segregation and enable the carbon content fraction fluctuation in the stainless steel blank to be within +/-0.015%; step (2): carrying out high-temperature diffusion homogenization treatment on the stainless steel blank to obtain a primary product; and (3): and (3) forging or rolling deformation treatment is carried out on the primary product obtained in the step (2) to obtain the stainless steel material. The preparation method of the stainless steel material and the stainless steel material provided by the application can effectively reduce the segregation degree of the stainless steel, reduce the distribution of inclusions, refine grains and facilitate the control of defects such as holes and high-temperature ferrite.
Description
Technical Field
The application relates to the technical field of stainless steel materials, in particular to a preparation method of a stainless steel material and the stainless steel material.
Background
At present, CSS-42L and Cronidur high-temperature stainless steel are potential materials of new-generation aviation bearing steel due to better high-temperature resistance and corrosion resistance.
However, since these steel alloys have a high content, they tend to have a composition that is not uniform due to serious dendrite segregation during solidification, which not only makes it easy to generate inclusions that are difficult to remove during solidification, but also often causes segregation-type defects such as freckles. And because the Cr element content in the steel is higher, a brittle high-temperature ferrite phase is easily formed in the subsequent high-temperature diffusion and forging processes, so that the blank is easy to crack in the deformation process. The unreasonable forging process not only can cause the phenomena of coarse grains and mixed crystals and reduce the toughness of the material, but also can easily cause the defects of flow instability, microcrack and the like, and the defects are difficult to eliminate in the subsequent heat treatment process, so that the service life can be greatly shortened, and the safety of the material is reduced.
Therefore, how to provide a method for preparing a stainless steel material and a stainless steel material, which can effectively reduce the segregation degree of stainless steel and reduce the distribution of inclusions, is a problem that needs to be solved by those skilled in the art.
Disclosure of Invention
Therefore, the technical problem to be solved by the present application is to provide a method for preparing a stainless steel material and a stainless steel material, which can effectively reduce the segregation degree of stainless steel and reduce the distribution of inclusions.
In order to solve the above problems, the present application proposes a method for preparing a stainless steel material, comprising the steps of:
step (1): preparing a stainless steel blank by adopting a duplex process of vacuum smelting and vacuum self-consumption, and reducing component segregation by controlling solidification parameters; mitigating compositional segregation via solidification parameter control comprises: controlling the maximum molten pool depth of a pasty zone of the consumable blank by controlling a current-voltage ratio so as to further reduce component segregation and enable the carbon content fraction fluctuation in the stainless steel blank to be within +/-0.015%;
step (2): carrying out high-temperature diffusion homogenization treatment on the stainless steel blank to obtain a primary product;
and (3): and (3) forging or rolling deformation treatment is carried out on the primary product obtained in the step (2) to obtain the stainless steel material.
Further, the method for controlling the maximum depth of the molten pool in the mushy zone of the consumable blank by controlling the current-voltage ratio comprises the following steps:
and controlling the current-voltage ratio between 260 and 320A/V to ensure that the maximum molten pool depth of the pasty zone of the consumable blank is less than 250mm, thereby reducing the component segregation.
Further, during the step (1), cooling helium gas is introduced, and the pressure of the cooling helium gas is between 0.2 and 1.5 kpa.
Further, riser cutting and/or peeling treatment is carried out on the stainless steel blank; for a steel ingot with a length of 1-1.5m, a crucible with a diameter of 0.4-0.6m is used. After the vacuum self-consumption is finished, the cutting size of a dead head of the stainless steel blank is more than or equal to 0.15m; and/or the peeling thickness of the stainless steel blank is more than or equal to 15mm;
and/or, in the step (1), the preparation of the stainless steel blank by adopting a vacuum smelting and vacuum consumable duplex process comprises the following steps: adopting a consumable blank with the weight of 1t-3t in the vacuum consumable process; preferably, 1-1.5t of high-temperature stainless steel consumable blank is adopted in the vacuum consumable process;
further, the primary product is a uniform structure without high-temperature ferrite;
further, step (2): the method for carrying out high-temperature diffusion homogenization treatment on the stainless steel blank to obtain a primary product comprises the following steps:
adding pre-deformation treatment before high-temperature diffusion, wherein the temperature of the pre-deformation treatment is more than or equal to 1000 ℃, and the deformation is less than or equal to 30%;
and/or, carrying out high-temperature heat preservation on the stainless steel blank at the temperature of more than or equal to 1120 ℃, preferably, the temperature of the high-temperature heat preservation is 1120-1230 ℃; and/or the high-temperature heat preservation time is 10-25h.
Furthermore, the average size of crystal grains of the stainless steel material is less than or equal to 15 mu m, and the size of hole defects of the stainless steel material is less than or equal to 10 mu m; the maximum size of the inclusions in the stainless steel material is less than or equal to 5 mu m.
Further, in the step (3): the forging or rolling deformation treatment of the primary product obtained in the step (2) comprises the following steps:
performing multiple-fire forging deformation treatment on the primary product, wherein upsetting and drawing out are alternately performed in the multiple-fire forging deformation treatment;
further, in the multiple-fire forging deformation treatment, the temperature of the start forging is not lower than 1100 ℃, and preferably, the temperature of the start forging is 1100-1200 ℃.
Further, in the process of multi-fire forging deformation treatment, the total forging ratio of the blank is more than or equal to 7; and/or the deformation of the last heating time is more than or equal to 50 percent;
and/or in the process of multi-fire forging deformation treatment, the temperature of finish forging is not lower than 950 ℃; and/or, during the multiple-fire forging deformation treatment, the strain rate is not higher than 0.1s -1 。
Further, the preparation method of the stainless steel material also comprises the following steps:
after the step (4): and (4) heating the stainless steel material obtained in the step (3) to 780-950 ℃, preserving heat for 2-5 hours, and then cooling to room temperature in air.
According to still another aspect of the present application, there is provided a stainless steel material, which is prepared by the above-mentioned stainless steel material preparation method; the fluctuation of the carbon content fraction of the stainless steel material is within +/-0.015 percent, the maximum size of inclusions in the stainless steel material is less than or equal to 5 mu m, the size of grains at the 1/2 radius part of the stainless steel material is less than or equal to 15 mu m, and the size of hole defects of the stainless steel material is less than or equal to 10 mu m; the stainless steel material is free of high-temperature ferrite.
Furthermore, the content of carbon in the stainless steel material is less than or equal to 0.15wt%, the content of chromium element is more than 13wt%, and the content of total alloy is more than 30wt%.
According to the preparation method of the stainless steel material and the stainless steel material, coordinated regulation and control are performed through a series of technologies such as high-homogeneity consumable blank solidification, high-temperature diffusion homogenization and multi-fire-number cross forging, composition segregation is controlled, inclusions are reduced, fine and uniform grains of the obtained material are guaranteed, and high-temperature ferrite and holes are avoided. After the treatment, the obtained stainless steel material has the carbon content fraction fluctuation within +/-0.015 percent, the maximum size of the inclusions is less than or equal to 5 mu m, and the number of the inclusions in unit area is not more than 5/mm 2 The average size of crystal grains at 1/2 radius is less than or equal to 15 mu m, the maximum size of hole defects is less than or equal to 10 mu m, and high-temperature delta-ferrite is not found in the structure. The method can effectively reduce the segregation degree of the stainless steel, reduce the distribution of inclusions, and is favorable for controlling defects such as holes and high-temperature ferrite.
Drawings
FIG. 1 shows the element enrichment and inclusion throwing path of the solidification front of example 1;
FIG. 2 is the high temperature diffusion and forging deformation of example 1;
FIG. 3 is a statistical chart of inclusions in steel bar of phi 60mmCSS-42L of example 1;
FIG. 4 is a graph showing the grain size of a 60mm diameter CSS-42L steel bar of example 1;
FIG. 5 is a structural drawing of a steel bar of phi 60mm CSS-42L in example 1.
Detailed Description
Referring to fig. 1 to 5 in combination, a method for preparing a stainless steel material includes the following steps:
step (1): preparing a stainless steel blank by adopting a vacuum smelting and vacuum consumable duplex process, and reducing component segregation by controlling solidification parameters; mitigating compositional segregation via solidification parameter control comprises: controlling the maximum molten pool depth of a pasty zone of the consumable blank by controlling a current-voltage ratio so as to further reduce component segregation and enable the carbon content fraction fluctuation in the stainless steel blank to be within +/-0.015%;
step (2): carrying out high-temperature diffusion homogenization treatment on the stainless steel blank to obtain a primary product;
and (3): and (3) forging or rolling deformation treatment is carried out on the primary product obtained in the step (2) to obtain the stainless steel material.
The method controls the maximum molten pool depth by controlling the current-voltage ratio, the proper molten pool depth and the full molten pool shape are favorable for discharging gas in the molten pool and feeding liquid metal, and the smaller mushy zone is favorable for reducing the segregation degree of steel. That is, the present application can control the degree of alloy segregation by controlling the current-voltage ratio.
The application also discloses some embodiments, and the method for controlling the maximum molten pool depth of the consumable blank mushy zone by controlling the current-voltage ratio comprises the following steps:
and controlling the current-voltage ratio between 260 and 320A/V to ensure that the maximum molten pool depth of the pasty zone of the consumable blank is less than 250mm, thereby reducing the component segregation.
The current-voltage ratio is 260-320A/V, so that the maximum molten pool depth of a consumable blank mushy zone is less than 250mm, the segregation degree of steel can be effectively reduced, the control of defects such as looseness and air holes is facilitated, and the discharge of gas in the molten pool and the feeding of liquid metal can be promoted while low segregation is considered. After the treatment of the step (1), the fluctuation of the carbon mass fraction is within +/-0.015 percent.
The application also discloses some embodiments, during the step (1), cooling helium gas is introduced, and the pressure is between 0.2 and 1.5 kpa. The introduction of cooling helium gas can reduce dendrite arms and remove relatively dense inclusions. Specifically, the primary dendrite arms and the secondary dendrite arms can be reduced by introducing cooling helium gas, the pitch of the primary dendrite arms is 980 mu m at most, and the pitch of the secondary dendrite arms is 145 mu m at most after introducing the helium gas; meanwhile, the cooling gas is introduced to reduce component segregation and shorten the growth time of the inclusions, thereby being beneficial to removing the inclusions with higher relative density. Reach the purpose of refining the dendritic crystal through letting in cooling helium in this application, and this application can also be through letting in cooling helium control and alleviate the segregation, get rid of the higher inclusion of relative density.
The application also discloses some embodiments, riser cutting and/or skinning are performed on the stainless steel blank; this application can guarantee the homogeneity of composition through rising head cutting and skinning processing, avoids forging in-process fracture to improve the utilization ratio of material. The peeling treatment can remove the light impurities on the columnar surface of the cast ingot, and the riser cutting can remove the light impurities floating on the upper surface of the cast ingot and the position of the cast ingot close to the upper surface with the maximum segregation. After the treatment, the average size of the inclusions in the obtained stainless steel blank is 3 mu m, the maximum size of the inclusions is not more than 5 mu m, and the number of the inclusions in unit area is not more than 5/mm 2 ；
The present application also discloses some embodiments, during step (1), for ingots with a length of 1-1.5m, crucibles with a diameter of 0.4-0.6m are used. After the vacuum self-consumption is finished, the cutting size of a dead head of the stainless steel blank is more than or equal to 0.15m, and/or the peeling thickness is more than or equal to 15mm, so that the material uniformity can be ensured, and the utilization rate can be improved.
And/or, during step (1): the preparation method of the stainless steel blank by adopting the duplex process of vacuum smelting and vacuum self-consumption comprises the following steps: adopting a consumable blank with the weight of 1t-3t in the vacuum consumable process; preferably, 1-1.5t of high-temperature stainless steel consumable blank is adopted in the vacuum consumable process. The consumable process comprises three stages of arc striking, arc stabilizing and arc extinguishing, and the segregation degree of steel can be effectively reduced, the distribution of inclusions is reduced, and the defects such as porosity and air holes can be favorably controlled by controlling solidification parameters including current-voltage ratio, cooling strength and riser cutting and skinning.
In summary, the segregation of the inclusions and components is controlled in three aspects, and the segregation degree of the alloy is controlled by controlling the current-voltage ratio and enhancing the cooling strength in the solidification process; then after solidification, directly cutting off the position with the largest segregation through riser cutting and removing light inclusions floating on the surface; finally, peeling off the skin to remove the light impurities on the side surface.
The application also discloses some embodiments, the primary product is a homogeneous structure without high temperature ferrite; the primary product obtained in the step (1) is a high-temperature stainless steel low-segregation double-vacuum blank, and is further combined with pre-deformation treatment, so that the diffusion channel of elements is increased, and the probability of high-temperature ferrite due to local Cr element enrichment is reduced. Meanwhile, the temperature and time of high-temperature diffusion homogenization treatment are accurately controlled, so that the high-temperature delta-ferrite in a thermodynamic equilibrium state is avoided, and the cracking probability in forging is reduced.
The present application also discloses some embodiments, step (2): the method for carrying out high-temperature diffusion homogenization treatment on the stainless steel blank to obtain the primary product further comprises the following steps:
adding pre-deformation treatment before high-temperature diffusion, wherein the temperature of the pre-deformation treatment is more than or equal to 1000 ℃, and the deformation is less than or equal to 30%;
and/or, the stainless steel blank is subjected to high-temperature heat preservation at the temperature of more than or equal to 1120 ℃ so as to achieve the purpose of more uniform distribution of interdendritic components.
Preferably, the temperature of the high-temperature heat preservation is 1120-1230 ℃; avoid the high temperature ferrite caused by overhigh temperature.
And/or the high-temperature heat preservation time is 10-25h. And (3) the blank obtained after the treatment of the step (2), namely the primary product, does not contain high-temperature delta ferrite.
The application also discloses some embodiments, the average size of crystal grains of the stainless steel material is less than or equal to 15 mu m, and the stainless steel material has no instability defects such as holes, cracks and the like; the maximum size of the inclusions in the stainless steel material is less than or equal to 5 mu m.
The application also discloses some embodiments, in step (3): the forging or rolling deformation treatment of the primary product obtained in the step (2) comprises the following steps:
performing multi-fire cross forging deformation treatment on the primary product; upsetting and drawing out are alternately carried out in the multiple-fire forging deformation treatment; in the multi-fire-number cross forging deformation treatment, a thermal deformation mode based on the cooperative control of deformation temperature, strain rate and deformation amount is utilized to obtain the high-temperature stainless steel material with fine and uniform crystal grains and no instability defects such as microcracks, and the average size of the crystal grains of the material treated in the step (3) is less than or equal to 15 microns and no instability defects such as holes and microcracks exist.
The application also discloses some embodiments, in the multi-fire cross forging deformation treatment, the temperature of the initial forging is not lower than 1100 ℃, and preferably, the temperature of the initial forging is 1100-1200 ℃. The forging temperature can not be too low, the forging temperature is too low, microcracks and flow instability can be easily formed, dynamic recrystallization can not completely occur, mixed crystal tissues are easily formed, the subsequent performance is not good, but the forging temperature can not be too high, the forging temperature is too high, local overheating is easily formed to form high-temperature ferrite, the high-temperature ferrite is easy to crack, the subsequent use is not good, and meanwhile, the high forging temperature can further enable the crystal grains after the dynamic recrystallization is completed to further grow, so that the strength and the toughness of the steel plate are reduced. The above temperature range is an optimum forging temperature.
The application also discloses some embodiments, in the multi-fire cross forging deformation treatment process, the total forging ratio of the blank is more than or equal to 7, so that the deformation of all parts of the whole blank is uniform; and/or the deformation of the last fire is more than or equal to 50 percent; dynamic recrystallization needs to reach this critical amount of deformation to completely occur, otherwise mixed crystal structure is easily formed, which is detrimental to subsequent performance. And/or in the process of multi-fire cross forging deformation treatment, the temperature of finish forging is not lower than 950 ℃; and/or, during the multiple-fire cross-forging deformation process, the strain rate is not higher than 0.1s -1 。
The present application can prevent flow instability and microcracking caused by too low finish forging temperature and too high strain rate by adopting the finish forging temperature and strain rate. By means of cooperative control of deformation temperature, strain rate and deformation in the multi-fire forging process, the hole type micro defects can be healed while grains are refined, and the hole type micro defects are eliminated, namely the maximum size of the hole type micro defects in the prepared material is smaller than or equal to 10 microns.
After the treatment of the step (3), the average size of crystal grains at the 1/2 radius part of the obtained forged material is less than or equal to 15 mu m, and the maximum size of the hole defects is less than or equal to 10 mu m. The crystal grains of the high-temperature stainless steel are fine and uniform and have no instability defects such as micro-cracks.
The application also discloses some embodiments, and the preparation method of the stainless steel material further comprises the following steps:
after the step (4): and (4) heating the stainless steel material obtained in the step (3) to 780-950 ℃, preserving heat for 2-5 hours, and then cooling to room temperature. Can prevent the stainless steel from separating Cr along the grain boundary 23 C 6 Increasing the intergranular corrosion tendency. The cooling mode can adopt air cooling.
The application provides some embodiments and discloses a stainless steel material, which is prepared by the preparation method of the stainless steel material; the fluctuation of the carbon content fraction of the stainless steel material is within +/-0.015 percent; the maximum size of the inclusions in the stainless steel material is less than or equal to 5 mu m, and the number of the inclusions in unit area is not more than 5/mm 2 (ii) a The size of crystal grains at 1/2 radius of the stainless steel material is less than or equal to 15 mu m; the size of the hole defect of the stainless steel material is less than or equal to 10 mu m; and no instability defects such as high-temperature ferrite, microcrack and the like exist.
1. The stainless steel material is high-temperature stainless steel, the carbon content of the stainless steel material is less than or equal to 0.15wt%, and the chromium content of the stainless steel material is>13wt% and the total alloy content is more than 30wt%. Due to the existence of ultrahigh alloy elements, the steel has high molten steel viscosity, large pasty zone, long local solidification time, developed dendritic crystal and serious micro segregation, so that not only are inclusions which are difficult to remove easily generated in the solidification process, but also segregation defects such as freckles and the like often occur. The high chromium element simultaneously causes high temperature delta-ferrite to be easily formed in the high temperature diffusion process, and is not beneficial to subsequent uniform deformation. In order to solve the problem of the commonality, the method carries out synergistic regulation and control through a series of technologies such as high-homogeneity consumable blank solidification, high-temperature diffusion homogenization, multi-fire forging deformation and the like so as to achieve the aims that the carbon content fraction fluctuation of the high-temperature stainless steel material is within +/-0.015 percent, the maximum size of inclusions is less than or equal to 5 mu m, and the number of inclusions in unit area is not more than 5/mm 2 The average size of crystal grains at the 1/2 radius is less than or equal to 15 mu m, the maximum size of hole defects is less than or equal to 10 mu m, and high-temperature delta-ferrite is not found in the structure, so that the cleaning and homogenization of the high-temperature stainless steel are promoted.
This application is through control current-voltage ratio, strengthen cooling strength and reasonable rising head cutting and take off the skin and come control to alleviate the composition segregation, refines dendritic crystal, reduces the inclusion, has guaranteed the casting blank quality on the one hand, and on the other hand has improved material utilization, has reduced the material cost.
According to the method, through controlling the parameters of high-temperature diffusion homogenization of the casting blank, a brittle high-temperature delta-ferrite phase is eliminated, and the cracking probability in subsequent deformation is reduced.
According to the method, the grain size of the obtained material is ensured to be fine and uniform, and the defects of flow instability, microcrack and the like are avoided at the same time through a thermal deformation mode based on the cooperative control of the deformation temperature, the strain rate and the deformation.
2. According to the method, through low segregation of the self-consuming casting blank, high-temperature diffusion homogenization and multiple-fire forging deformation treatment, the generation of instability defects such as microcracks can be effectively reduced, and the service life and the safety stability are improved. The reasonable high-temperature homogenization parameters can improve component segregation caused in the solidification process and improve the uniformity of components. And then the micro defects left in the solidification process can be further healed through forging treatment with multiple fire times, and meanwhile, the grains are fine and uniform.
3. The method is suitable for high-quality preparation of pipes and bars such as bearing steel, gear steel and die steel. The method for improving the purity and homogenization of the high-temperature stainless steel finally enables bars or pipes such as bearing steel, gear steel, die steel and the like to meet the requirements of high speed, high temperature, corrosion, large load harsh working conditions and high fatigue life service performance. The application provides an effective method for improving the internal quality of high-temperature stainless steel such as CSS-42L and Cronidur.
The high-temperature stainless steel obtained by the method is compact in matrix, fine and uniform in crystal grains, can be used for manufacturing parts in the fields of aviation, aerospace, tools, dies, gears and the like, and has the advantages of long service life, high temperature resistance, high reliability and the like.
Examples
Example 1
The embodiment of the method for preparing the high-temperature stainless steel bar comprises the following specific preparation steps:
1) Preparing a high-temperature stainless steel low-segregation double-vacuum consumable blank: the cast-state blank is prepared by adopting double vacuum, the material of the steel ingot is CSS-42L steel, the consumable ingot is 1.5t, the length of the steel ingot is 1.5m, the diameter of a crucible is 0.4m, the current-voltage ratio is controlled at 320A/V in the arc stabilizing stage, cooling helium is introduced, the pressure intensity is 0.2kpa, a dead head is cut by 0.25m, the peeling is 15mm, the average size of inclusions of the obtained casting blank is 3 mu m, the size of the maximum inclusion is 5 mu m, and the fluctuation of the carbon content fraction is within +/-0.008%.
2) And (3) blank high-temperature diffusion homogenization treatment: pre-deforming the casting blank at 1000 ℃ and 10% of deformation, and then preserving heat at 1120 ℃ for 25h to enable inter-dendritic component distribution to be more uniform.
3) Multiple-fire cross forging deformation cogging treatment: in the forging process, a two-heading two-drawing process is adopted to realize cross deformation, the initial forging temperature is 1100 ℃, the forging ratio of the whole blank is 7, the last hot forging ratio is 2, the final forging temperature is 950 ℃, and the forging strain rate is 0.1s -1 Heating the stainless steel material to 950 ℃, preserving the heat for 2 hours, and then air-cooling to room temperature. The average size of crystal grains at the 1/2 radius of the bar is 8 mu m, the size of the hole defect is less than 10 mu m, and high-temperature ferrite and microcracks do not exist.
Example 2
The embodiment of the method for preparing the high-temperature stainless steel bar comprises the following specific preparation steps:
1) Preparing a high-temperature stainless steel low-segregation double-vacuum consumable blank: the cast-state blank is prepared by double vacuum, the material of the steel ingot is CSS-42L steel, the consumable ingot is 1.6t, the length of the steel ingot is 1m, the diameter of a crucible is 0.5m, the current-voltage ratio at the arc stabilizing stage is controlled to be about 280A/V, cooling helium is introduced, the pressure intensity is 1.5kpa, a riser is cut by 0.18m, the peeling is 18mm, the average size of inclusions of the obtained casting blank is 2 mu m, the size of the maximum inclusion is 5 mu m, and the fluctuation of the carbon content fraction is within +/-0.009%.
2) And (3) blank high-temperature diffusion homogenization treatment: pre-deforming the casting blank at 1000 ℃ and 10% deformation, and then preserving heat at 1170 ℃ for 16h to ensure that the intercrystalline components are distributed more uniformly.
3) Multiple fire cross forging deformationBlank treatment: in the forging process, a two-heading two-drawing process is adopted to realize cross deformation, the initial forging temperature is 1150 ℃, the forging ratio of the whole blank is 8, the last hot forging ratio is 3, the final forging temperature is 950 ℃, and the forging strain rate is 0.1s -1 Heating the stainless steel material to 780 ℃ and preserving the heat for 5 hours, and then cooling the stainless steel material to room temperature in air. The average size of crystal grains at the 1/2 radius of the bar is 12 mu m, the size of hole defects is less than 10 mu m, and high-temperature ferrite and microcracks do not exist.
Example 3
The embodiment prepares a high-temperature stainless steel bar, and the specific preparation steps are as follows:
1) Preparing a high-temperature stainless steel low-segregation double-vacuum consumable blank: the cast-state blank is prepared by double vacuum, the material of the steel ingot is CSS-42L steel, the consumable ingot is 1t, the length of the steel ingot is 1m, the diameter of the crucible is 0.4m, the current-voltage ratio at the arc stabilizing stage is controlled to be about 260A/V, and cooling helium gas is introduced, and the pressure intensity is 1.33kpa. Cutting a dead head by 0.15m, peeling by 15mm, wherein the average size of inclusions in the obtained casting blank is 2 mu m, the maximum size of the inclusions is 4 mu m, and the fluctuation of the carbon content fraction is within +/-0.012%.
2) And (3) blank high-temperature diffusion homogenization treatment: pre-deforming the casting blank at 1000 deg.c and 8% deformation amount, and maintaining at 1230 deg.c for 10 hr to make the interdendritic components distributed homogeneously.
3) Multiple-fire cross forging deformation cogging treatment: in the forging process, a two-heading two-drawing process is adopted to realize cross deformation, the initial forging temperature is 1200 ℃, the forging ratio of the whole blank is 9, the last hot forging ratio is 4, the final forging temperature is 950 ℃, and the forging strain rate is 0.1s -1 Heating the stainless steel material to 900 ℃, preserving the heat for 3 hours, and then cooling the stainless steel material to room temperature in air. The average size of crystal grains at the 1/2 radius of the bar is 14 mu m, the size of hole defects is less than 10 mu m, and high-temperature ferrite and microcracks do not exist.
Example 4
The embodiment of the method for preparing the high-temperature stainless steel bar comprises the following specific preparation steps:
1) Preparing a high-temperature stainless steel low-segregation double-vacuum consumable blank: the method is characterized in that a double-vacuum casting blank is adopted to prepare an as-cast blank, the material of a steel ingot is CSS-42L steel, the consumable ingot is 3t, the length of the steel ingot is 1.3m, the diameter of a crucible is 0.6m, the current-voltage ratio in an arc stabilizing stage is controlled at 320A/V, cooling helium gas is introduced, the pressure intensity is 1.33kpa, a dead head is cut by 0.25m, peeling is 21mm, the average size of inclusions of the obtained casting blank is 3 mu m, the size of the maximum inclusions is 5 mu m, and the fluctuation of the carbon content fraction is within +/-0.008%.
2) And (3) blank high-temperature diffusion homogenization treatment: pre-deforming the casting blank at 1050 ℃ and 30% deformation, and then preserving heat at 1150 ℃ for 25h to ensure that the intercrystalline components are distributed more uniformly.
3) Multiple-fire cross forging deformation cogging treatment: in the forging process, a two-heading two-drawing process is adopted to realize cross deformation, the initial forging temperature is 1100 ℃, the forging ratio of the whole blank is 9, the last hot forging ratio is 4, the final forging temperature is 980 ℃, and the forging strain rate is 0.05s -1 Heating the stainless steel material to 800 ℃, preserving the heat for 5 hours, and then air-cooling to room temperature. The average size of crystal grains at the 1/2 radius of the bar is 8 mu m, the size of the hole defect is less than 10 mu m, and high-temperature ferrite and microcracks do not exist.
Comparative example 1
The method is basically the same as the preparation method of the embodiment 1, except that the current-voltage ratio in the arc stabilizing stage is 220A/V, the final bearing steel bar is detected, the fluctuation of the carbon content is more than +/-0.025 percent, and inclusions with the size of more than 5 mu m are found, but the average size of grains at the 1/2 radius of the bar is 13 mu m, the size of hole defects is less than 10 mu m, and high-temperature ferrite and microcracks are not found.
Comparative example 2
Basically the same preparation method as that of the embodiment 2 is carried out, except that the casting blank is subjected to heat preservation at the high temperature of 1270 ℃ for 16 hours before forging, the final bearing steel bar is detected to have the carbon content fluctuation of about +/-0.01 percent, the average inclusion size is 2 mu m, the maximum inclusion size is 5 mu m, but the average grain size at the radius of 1/2 of the bar is 28 mu m, and 15 mu m microcracks and high-temperature ferrite are found.
Comparative example 3
Basically the same procedure as in example 3 was followed, except that the finish forging temperature was 850 ℃ and the final hot forging ratio was 4, the final bearing steel bar was examined to have a fluctuation in carbon content of about. + -. 0.013%, an average inclusion size of 3 μm, a maximum inclusion size of 5 μm, and high temperature ferrite was not found, and the average grain size at 1/2 radius of the bar was 15 μm, but microcracks of 20 μm were found.
According to an embodiment of the application, a stainless steel material is provided, and the stainless steel material is prepared by the preparation method of the stainless steel material.
It is readily understood by a person skilled in the art that the advantageous ways described above can be freely combined, superimposed without conflict.
The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed. The foregoing are only preferred embodiments of the present application, and it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present application, and these modifications and variations should also be considered as the protection scope of the present application.
Claims (10)
1. The preparation method of the stainless steel material is characterized by comprising the following steps:
step (1): preparing a stainless steel blank by adopting a duplex process of vacuum smelting and vacuum self-consumption, and reducing component segregation by controlling solidification parameters; the mitigating compositional segregation via solidification parameter control comprises: controlling the maximum molten pool depth of a pasty zone of the consumable blank by controlling a current-voltage ratio so as to further reduce component segregation, so that the fluctuation of the carbon content fraction in the stainless steel blank is within +/-0.015 percent;
step (2): carrying out high-temperature diffusion homogenization treatment on the stainless steel blank to obtain a primary product;
and (3): and (3) forging or rolling deformation treatment is carried out on the primary product obtained in the step (2) to obtain the stainless steel material.
2. A method of manufacturing a stainless steel material according to claim 1, wherein said controlling a current to voltage ratio to control a consumable billet mush zone maximum weld puddle depth comprises the steps of:
the current-voltage ratio is controlled between 260-320A/V, so that the maximum molten pool depth of the consumable blank mushy zone is less than 250mm.
3. The method for preparing a stainless steel material according to claim 1, wherein during step (1), cooling helium gas is fed, and the pressure of the cooling helium gas is between 0.2 and 1.5 kpa.
4. The method for preparing a stainless steel material according to claim 1, wherein the stainless steel blank is subjected to riser cutting and/or skinning;
further, in the step (1), for the steel ingot with the length of 1-1.5m, the diameter of the crucible is 0.4-0.6m; after the vacuum self-consumption is finished, cutting a dead head of the stainless steel blank to a size of more than or equal to 0.15m; and/or the peeling thickness of the stainless steel blank is more than or equal to 15mm;
and/or, a consumable blank with the weight of 1t-3t is adopted in the vacuum consumable process; preferably, 1-1.5t of high-temperature stainless steel consumable blank is adopted in the vacuum consumable process.
5. A method of manufacturing a stainless steel material according to claim 1, wherein the primary product is a homogeneous structure without high temperature ferrite;
and/or, the step (2): the method comprises the following steps of carrying out high-temperature diffusion homogenization treatment on the stainless steel blank to obtain a primary product:
adding pre-deformation treatment before high-temperature diffusion, wherein the temperature of the pre-deformation treatment is more than or equal to 1000 ℃, and the deformation is less than or equal to 30%;
and/or, carrying out high-temperature heat preservation on the stainless steel blank at the temperature of more than or equal to 1120 ℃, preferably, the high-temperature heat preservation temperature is 1120-1230 ℃; and/or the high-temperature heat preservation time is 10-25h.
6. A method of producing a stainless steel material according to claim 1, characterized in that the average size of the grains of the stainless steel material is ≤ 15 μ ι η; the size of the holes of the stainless steel material is less than or equal to 10 mu m; the maximum size of inclusions in the stainless steel material is less than or equal to 5 mu m.
7. The method for preparing a stainless steel material according to claim 1, wherein in the step (3): the forging or rolling deformation treatment of the primary product obtained in the step (2) comprises the following steps:
performing multiple-fire forging deformation treatment on the primary product, wherein upsetting and lengthening are performed alternately in the multiple-fire forging deformation treatment;
further, in the multiple-fire forging deformation treatment, the initial forging temperature is not lower than 1100 ℃, and preferably, the initial forging temperature is 1100-1200 ℃.
8. The method for preparing a stainless steel material according to claim 7, wherein during the multiple-fire forging deformation treatment, the total forging ratio of the blank is not less than 7; and/or the deformation of the last fire is more than or equal to 50 percent;
and/or in the process of the multiple-fire forging deformation treatment, the temperature of finish forging is not lower than 950 ℃; and/or, during the multiple-fire forging deformation treatment, the strain rate is not higher than 0.1s -1 。
9. The method for preparing a stainless steel material according to claim 1, further comprising the steps of:
after the step (4): heating the stainless steel material obtained in the step (3) to 780-950 ℃, preserving heat for 2-5 hours, and then air-cooling to room temperature.
10. A stainless steel material, characterized in that it is produced by the method of manufacturing a stainless steel material according to any one of claims 1-8; the fluctuation of the carbon content fraction of the stainless steel material is within +/-0.015 percent, the maximum size of inclusions in the stainless steel material is less than or equal to 5 mu m, the size of crystal grains at the 1/2 radius part of the stainless steel material is less than or equal to 15 mu m, and the size of hole defects of the stainless steel material is less than or equal to 10 mu m; the stainless steel material is free of high-temperature ferrite;
and/or the stainless steel material contains less than or equal to 0.15wt% of carbon, more than 13wt% of chromium element and more than 30wt% of total alloy.
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