CN105420454A - Heat treatment method for large heat-resisting high alloy steel castings - Google Patents
Heat treatment method for large heat-resisting high alloy steel castings Download PDFInfo
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Abstract
The invention relates to the technical field of steel casting heat treatment, in particular to a heat treatment method for large heat-resisting high alloy steel castings. The heat treatment method comprises the steps of high temperature diffusion annealing, gating and riser system cutting, normalization air cooling, primary tempering and secondary tempering, wherein carbon arc air gouging finishing is carried out on the surfaces of the castings between the primary tempering step and the secondary tempering step. According to the method, the problem that the large heat-resisting high alloy steel castings made of ZG12Cr9Mo1CoNiVNbNB are easily cracked in the heat treatment process is solved, and the mechanical properties of the steel castings at normal temperature and at high temperature meet the use requirements.
Description
Technical field
The present invention relates to steel casting technical field of heat treatment, particularly a kind of heat treating method of large-scale heat-resisting high alloy cast steel.
Background technology
High heat-resisting high quality steel castings material is ZG12Cr9Mo1CoNiVNbNB, for a kind of heat resistance material, the main flow steel grade that this material will be the high temperature resistant component of following clean and effective ultra supercritical steam turbine, the foundry goods of such material can at 600 ~ 620 DEG C, be on active service for a long time under the extreme condition of 30MPa, high temperature resistant due to material itself, high pressure characteristics, the heat-stable material making its service condition the most advanced comparatively is at present high 30 DEG C, 3MPa, not only can be the efficiency that power generation energy resource enterprise promotes 8 ~ 10%, greatly can also reduce CO2 emissions, the main efficient of current international energy industry development, cleaning material.
Because the alloying element of such material is many, content is high, smelts difficulty greatly, the restriction of welding technique and the high many-sided technology barriers of heat treatment requirements, and manufacturing enterprise of China produces this type of foundry goods at present still very large difficulty.Especially easily split foundry goods for this kind of high quality steel how to carry out the thermal treatment of system and not make foundry goods ftracture, the difficulty that material at high temperature enduring quality requires is met very large while meeting normal temperature performance index, particularly for the steel casting of gross weight 5 ~ 20t, thickest 150 ~ 300mm, not only relevant with smelting technology level, require also very high for the thermal treatment process after steel casting cast, if selection of heat-treatment processes is improper, the property indices of steel casting does not all reach requirement.
Summary of the invention
The present invention is directed to the service requirements of above-mentioned ZG12Cr9Mo1CoNiVNbNB high alloy material steel casting, a kind of heat treating method of large-scale heat-resisting high alloy cast steel is provided, to ensure the mechanical property of the every normal temperature of this material steel casting and high temperature, and prevent from ftractureing in heat treating castings process.
The object of the present invention is achieved like this, a kind of heat treating method of large-scale heat-resisting high alloy cast steel, comprise the steps: 1) high temperature diffusion annealing: after the steel casting after being poured is naturally cooled to 200-150 DEG C in sand mold, carry out shake out knockout, again steel casting entirety is moved in heat treatment furnace and carry out high temperature diffusion annealing, with the heat-up rate of 20 ~ 50 DEG C/h, be warming up to 1050 DEG C ~ 1110 DEG C insulation T time, wherein, soaking time T=D*2min/mm, D value is the maximum value in foundry goods thickest or rising head one-tenth-value thickness 1/10, foundry goods is cooled to the furnace 500 DEG C ~ 550 DEG C more afterwards with the cooling rate of 20 ~ 40 DEG C/h, 4h ~ 8h is to reduce the temperature difference at each position of steel casting in insulation, 2) pouring and riser systems cutting: after high temperature diffusion annealing, steel casting is come out of the stove and carry out covering and heat insulating process by insulating cotton, and expose rising head to be cut and gating system, carry out high-temperature machining, ensure the temperature > 400 DEG C of cutting part simultaneously, 3) normalizing air cooling: the steel casting after cutting is moved into heat treatment furnace, is warming up to AC with the heat-up rate of 20 ~ 50 DEG C/h
3+ (120 ~ 150) DEG C, and be incubated T time, then come out of the stove is cooled to≤Mf in the still air without convection current wind, 4) tempering: the foundry goods after normalizing air cooling is returned heat treatment furnace and is warming up to 640 ~ 670 DEG C with the heat-up rate of 20 ~ 50 DEG C/h, insulation 6h ~ 10h, then come out of the stove after being cooled to 150 ~ 200 DEG C with the cooling rate of 20 ~ 40 DEG C/h, immediately carbon arc air gouging carried out with further pre-shaping step 2 to cast(ing) surface) in cutting part, 5) double tempering: the laggard heat treatment furnace of steel casting surface carbon arc air gouging carries out double tempering, 720 ~ 750 DEG C are warming up to the heat-up rate of 20 ~ 50 DEG C/h, and be incubated 8h ~ 12h, then steel casting is less than 200 DEG C comes out of the stove to be cooled in the cooling rate stove of 20 ~ 40 DEG C/h, in static air, be cooled to room temperature.
Beneficial effect of the present invention is: because the alloying element kind of large-scale refractory alloy steel casting is many, alloy content is high, and teeming temperature is higher, in sandbox after cooling, foundry goods matrix belongs to martensite as-cast structure easy to crack, interior tissue is bad, there is larger segregation, and unrelieved stress is large, therefore, in method of the present invention, by after foundry goods shake out knockout, directly carry out high temperature diffusion annealing, the position making wall thickness larger and rising head heat penetration, as-cast structure full and uniformization, softening, thus cracking when avoiding follow-up rising head and gating system cutting, and establish good organization foundation for the thermal treatment of lower step, during pouring and riser systems cutting in the present invention, adopt insulating cotton to cover to cast(ing) surface, expose the position of needs cutting, do can prevent from foundry goods heat effects operator from operating can ensureing again casting temperature to be unlikely to reduce too fast like this, to prevent from ftractureing in foundry goods cutting process or after cutting, 3rd) step, in normalizing air cooling, the holding temperature of general steel casting normalizing is at the austenite transition points AC of material
3select between+30 ~ 80 DEG C, but for alloy material of the present invention, alloying element is many, content is high, therefore, adopt higher annealing holding temperature, for ensureing the further homogenizing of cast structure, and allow more alloy carbide first dissolve in austenite as far as possible, to separate out a certain amount of carbide again in follow-up normalizing cooling and drawing process, thus realize solution strengthening and the precipitation strength effect of this material, to ensure finally to obtain good ambient temperature mechanical properties and mechanical behavior under high temperature, and the slow air cooling after normalizing insulation, relatively traditional normalizing furnace is cold, can ensure that the cooling of foundry goods entirety evenly improves again plant factor simultaneously and is also convenient to heat treatment operation, foundry goods is cooled to and is less than M
fthe transformation completely of martensitic stucture can be realized, in of the present invention, double tempering is set, and between double tempering, add carbon arc air gouging to remove the surplus of pouring and riser systems cutting further, carbon arc air gouging is carried out after being arranged in a tempering, be because by a tempering, the residual stress of casting after normalizing can be eliminated, and the high rigidity tissue after softening normalizing, in this case carbon arc air gouging is implemented to high quality steel foundry goods, can prevent foundry goods from ftractureing.After carbon arc air gouging, by second time tempering, eliminate residual stress of casting further, and the hardened layer in softening carbon arc air gouging region, improve cast structure state further, be convenient to the process such as the follow-up processing of foundry goods, welding.
For ease of the cutting of steel casting pouring and riser systems, described step 2) in cutting pouring and riser systems time, leave 10mm ~ 30mm surplus between cut surface and the profile of foundry goods own; The mode of cutting exposed one by one is adopted for multiple position of excision that needs, has often cut behind a position immediately with insulating cotton covering and heat insulating again.
Embodiment
Describe the present invention in detail in particular embodiments below.
The heat treating method of large-scale heat-resisting high alloy cast steel of the present invention, comprise the steps: 1) high temperature diffusion annealing: after the large-scale steel-casting after being poured is naturally cooled to 200-150 DEG C in sand mold, carry out shake out knockout, by the sand lump of cast(ing) surface and type bone, chill is removed, then steel casting entirety moves in heat treatment furnace and carries out high temperature diffusion annealing by related pouring and riser systems, with the heat-up rate of 20 ~ 50 DEG C/h, be warming up to 1050 DEG C ~ 1110 DEG C insulation T time, wherein, soaking time T=D*2min/mm, D value is the maximum value in foundry goods thickest or rising head one-tenth-value thickness 1/10, foundry goods is cooled to the furnace 500 DEG C ~ 550 DEG C more afterwards with the cooling rate of 20 ~ 40 DEG C/h, 4h ~ 8h is to reduce the temperature difference at each position of steel casting in insulation, the high temperature diffusion annealing technique of this step can make position that wall thickness is larger and rising head heat penetration, as-cast structure full and uniformization, softening, so that the pouring and riser systems cutting of lower step, 2) pouring and riser systems cutting: after high temperature diffusion annealing, steel casting is come out of the stove and adopt insulating cotton to carry out covering and heat insulating process, prepare cutting, also expose position to be cut one by one during cutting to cut, and build by insulating cotton after having cut a position, carry out the cutting at next position again, ensure the temperature > 400 DEG C of cutting part simultaneously, for preventing the foundry goods body of cutting part from ftractureing simultaneously in cutting, each cutting part leaves 10mm ~ 30mm and cuts surplus, can prevent steel casting from cutting cracking in the cutting technique of this step, 3) normalizing air cooling: the steel casting after cutting is moved into heat treatment furnace, is warming up to AC with the heat-up rate of 20 ~ 50 DEG C/h
3+ (120 ~ 150) DEG C, and be incubated T time, wherein AC
3can calculate and be about 940 DEG C by steel casting alloy material composition according to the present invention, then come out of the stove is cooled to≤M in the still air without convection current wind
f, in the present invention, calculate M
fit is 90 DEG C, to complete the transformation of whole martensitic stucture, 4) tempering: the foundry goods after normalizing air cooling is returned heat treatment furnace and is warming up to 640 ~ 670 DEG C with the heat-up rate of 20 ~ 50 DEG C/h, insulation 6h ~ 10h, the unrelieved stress of further elimination normalizing, and the high rigidity tissue after softening normalizing, then come out of the stove after being cooled to 150 ~ 200 DEG C with the cooling rate of 20 ~ 40 DEG C/h, carry out surperficial carbon arc air gouging immediately with further pre-shaping step 2) in cutting part, 5) double tempering: again enter heat treatment furnace after steel casting surface carbon arc air gouging and carry out double tempering, 720 ~ 750 DEG C are warming up to the heat-up rate of 20 ~ 50 DEG C/h, and be incubated 8h ~ 12h, then steel casting is less than 200 DEG C comes out of the stove to be cooled in the cooling rate stove of 20 ~ 40 DEG C/h, in static air, be cooled to room temperature.Further elimination unrelieved stress, and softening gouge cementation zone, improve the final structural state of allotment foundry goods, is convenient to the process such as the precision work of follow-up steel casting and welding,
Adopt the large-scale steel-casting of heat treating method of the present invention, detected by the production test of reality, foundry goods traditional performance and r all can meet technical requirements very well, and wherein tensile strength Rm is 740 ~ 800MPa, surrender strong Rp
0.2be 520 ~ 580MPa, unit elongation A is 19 ~ 24%, relative reduction in area Z is 40 ~ 55%, and body hardness is 220 ~ 260HB, and the room temperature metal summer is 34 ~ 50J than v-notch ballistic work AKv.Simultaneously under high-temperature and durable detected value three kinds of test temperatures and corresponding load test stress, duration is distributed as 105 ~ 115h, equal conformance with standard requirement, final every mechanical property coincidence rate reaches 100%, all effectively avoids the problem of foundry goods cracking in and after batch heat treating castings process.
Claims (2)
1. the heat treating method of one kind large-scale heat-resisting high alloy cast steel, it is characterized in that, comprise the steps: 1) high temperature diffusion annealing: after the steel casting after being poured is naturally cooled to 200 ~ 150 DEG C in sand mold, carry out shake out knockout, again steel casting entirety is moved in heat treatment furnace and carry out high temperature diffusion annealing, with the heat-up rate of 20 ~ 50 DEG C/h, be warming up to 1050 DEG C ~ 1110 DEG C insulation T time, wherein, soaking time T=D*2min/mm, D value is the maximum value in foundry goods thickest or rising head one-tenth-value thickness 1/10, steel casting is cooled to the furnace 500 ~ 550 DEG C more afterwards with the cooling rate of 20 ~ 40 DEG C/h, 4h ~ 8h is to reduce the temperature difference at each position of steel casting in insulation, 2) pouring and riser systems cutting: after high temperature diffusion annealing, steel casting is come out of the stove and carry out covering and heat insulating process with lagging material, and expose rising head to be cut or gating system one by one, carry out high-temperature machining, ensure that the temperature of cutting part is greater than 400 DEG C all the time simultaneously, 3) normalizing air cooling: the steel casting after cutting is moved into heat treatment furnace, is warming up to AC with the heat-up rate of 20 ~ 50 DEG C/h
3+ (120 ~ 150) DEG C, and be incubated T time, then come out of the stove is cooled to≤M in the still air without convection current wind
f, its M
ffor martensitic stucture transforms temperature completely, 4) tempering: the foundry goods after normalizing air cooling is entered heat treatment furnace and is warming up to 640 ~ 670 DEG C with the heat-up rate of 20 ~ 50 DEG C/h, insulation 6h ~ 10h, then come out of the stove after being cooled to 150 ~ 200 DEG C with the cooling rate of 20 ~ 40 DEG C/h, immediately carbon arc air gouging carried out with further pre-shaping step 2 to cast(ing) surface) in cutting part, 5) double tempering: the laggard heat treatment furnace of steel casting surface carbon arc air gouging carries out double tempering, 720 ~ 750 DEG C are warming up to the heat-up rate of 20 ~ 50 DEG C/h, and be incubated 8h ~ 12h, then steel casting is less than 200 DEG C comes out of the stove to be cooled in the cooling rate stove of 20 ~ 40 DEG C/h, in static air, be cooled to room temperature.
2. the heat treating method of large-scale heat-resisting high alloy cast steel according to claim 1, is characterized in that, described step 2) in cutting pouring and riser systems time, leave 10mm ~ 30mm between cut surface and the profile of foundry goods own and cut surplus; During foundry goods cutting, cover cast(ing) surface by insulating cotton, multiple position needing to excise is adopted to the mode opened insulating cotton one by one and carry out cutting, again cover by insulating cotton immediately after often having cut a position.
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Cited By (9)
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| CN106337108A (en) * | 2015-08-17 | 2017-01-18 | 东风精密铸造安徽有限公司 | Heat treatment method for reducing solder joint hardness of ductile cast iron processing surface |
| CN107931584A (en) * | 2017-10-31 | 2018-04-20 | 中国航发北京航空材料研究院 | A kind of cutting method of the big riser running channel of large-sized high-temperature alloy casting |
| CN108705069A (en) * | 2018-05-29 | 2018-10-26 | 辽宁福鞍重工股份有限公司 | A kind of finishing process of monoblock cast heavy type combustion engine steering frame |
| CN109082513A (en) * | 2018-09-12 | 2018-12-25 | 新乡市长城铸钢有限公司 | A kind of heat treatment process of large size pump case |
| CN110317993A (en) * | 2018-03-29 | 2019-10-11 | 湖北长怡特钢贸易有限公司 | A kind of corrosion resistance Cr14Mo4V plastic die steel |
| CN111534667A (en) * | 2020-05-18 | 2020-08-14 | 杭州汽轮铸锻有限公司 | Vanadium steel casting treatment method |
| CN112045170A (en) * | 2020-08-26 | 2020-12-08 | 共享铸钢有限公司 | Method for preventing large steel casting from cracking |
| CN113441679A (en) * | 2021-05-28 | 2021-09-28 | 共享铸钢有限公司 | Casting method of heat-resistant steel casting |
| CN114921716A (en) * | 2022-03-18 | 2022-08-19 | 中国船舶重工集团公司第七二五研究所 | Cu aging type high-strength cast steel for structure and preparation method thereof |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106337108A (en) * | 2015-08-17 | 2017-01-18 | 东风精密铸造安徽有限公司 | Heat treatment method for reducing solder joint hardness of ductile cast iron processing surface |
| CN107931584A (en) * | 2017-10-31 | 2018-04-20 | 中国航发北京航空材料研究院 | A kind of cutting method of the big riser running channel of large-sized high-temperature alloy casting |
| CN110317993A (en) * | 2018-03-29 | 2019-10-11 | 湖北长怡特钢贸易有限公司 | A kind of corrosion resistance Cr14Mo4V plastic die steel |
| CN108705069A (en) * | 2018-05-29 | 2018-10-26 | 辽宁福鞍重工股份有限公司 | A kind of finishing process of monoblock cast heavy type combustion engine steering frame |
| CN109082513A (en) * | 2018-09-12 | 2018-12-25 | 新乡市长城铸钢有限公司 | A kind of heat treatment process of large size pump case |
| CN111534667A (en) * | 2020-05-18 | 2020-08-14 | 杭州汽轮铸锻有限公司 | Vanadium steel casting treatment method |
| CN111534667B (en) * | 2020-05-18 | 2022-01-18 | 杭州汽轮铸锻有限公司 | Vanadium steel casting treatment method |
| CN112045170A (en) * | 2020-08-26 | 2020-12-08 | 共享铸钢有限公司 | Method for preventing large steel casting from cracking |
| CN112045170B (en) * | 2020-08-26 | 2022-02-22 | 共享铸钢有限公司 | Method for preventing large steel casting from cracking |
| CN113441679A (en) * | 2021-05-28 | 2021-09-28 | 共享铸钢有限公司 | Casting method of heat-resistant steel casting |
| CN114921716A (en) * | 2022-03-18 | 2022-08-19 | 中国船舶重工集团公司第七二五研究所 | Cu aging type high-strength cast steel for structure and preparation method thereof |
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