CN104004969A - Outer cylinder casting and thermal treatment method for large-size steam turbine - Google Patents
Outer cylinder casting and thermal treatment method for large-size steam turbine Download PDFInfo
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- CN104004969A CN104004969A CN201410236540.XA CN201410236540A CN104004969A CN 104004969 A CN104004969 A CN 104004969A CN 201410236540 A CN201410236540 A CN 201410236540A CN 104004969 A CN104004969 A CN 104004969A
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Abstract
The invention relates to an outer cylinder casting and thermal treatment method for a large-size steam turbine and belongs to the technical field of casting and thermal treatment. The method comprises the following steps: in casting, controlling the mass percentage contents of the components of a cast steel piece, meanwhile controlling the Ceq value to be 0.48-0.54%, subsequently performing surface treatment inside and outside the cast piece, removing floating sand in an oxygen gouging mode, cutting a cast piece riser and a casting system, subsequently performing shot blasting treatment on the cast piece, determining the heat preservation temperature to be AC3+(50-100) DEG C when the cast piece is quenched, performing heat preservation for 7-9 hours, subsequently cooling with water, annealing, discharging outside a furnace, and cooling in air. According to the method, by controlling the contents of the components and the Ceq value, quenching treatment can be performed on the cast piece conveniently, the components of different batches are small in fluctuation range, and the quenching performance is relatively stable; by adopting the method, the hardness difference of the quenched large-size cast steel piece can be reduced, and the hardness difference of a cast piece body is less than or equal to +/-20HB. The method can be used for producing an outer cylinder of a steam turbine with the largest single side length of no less than 3000mm.
Description
Technical field
Patent of the present invention relates to a kind of casting and heat-treating methods, the particularly casting of large-scale steam turbine outer shell and heat treating method.
Background technology
Steam turbine outer shell steel casting is that 600MW is overcritical, the key part of ultra supercritical steam turbine unit.This product manufacture difficulty is very high, and before Wo company, domestic also do not have manufacturer successfully to produce, and also only has in the world Polish Yi Jia steel foundry successfully to produce.This steel casting material is G20Mo5, belongs to low alloy steel.Every cover foundry goods is divided into upper and lower two halves, upper semi-gross weight 24t, largest contours size 5300 * 3400 * 2000mm; Lower semi-gross weight 24.5t, largest contours size 5220 * 3440 * 1482mm.It is 60mm that upper second foundry goods entity 75% be take the wall thickness of upper part, thickest 290mm.This type of outer shell foundry goods is half rotary structure, and main-cylinder wall therefrom divides towards the bias of horizontal integration face flange and reaches more than 9%.
Such product material mechanical property requirements is higher: tensile strength requires 440 ~ 590 MPa, yield strength >=245 MPa, unit elongation >=22%, room temperature ballistic work AKv >=27J, Brinell hardness requires 130 ~ 175HB, and require single foundry goods body to divide equally to detect 5 positions, each position hardness value difference is less than 20HB, in a collection of foundry goods the average hardness value of all foundry goods and the detected result of sample differ can not over ± more than 20HB.This is for large-scale steel-casting, and difficulty is very large; G20Mo5 material is low alloy steel, but the over-all properties of having relatively high expectations, especially impact require high.Adopt traditional normalizing method, impact and be difficult to the stable customer requirement that reaches.For this reason, need to adopt the method for quenching first to meet the requirement of intensity and plasticity and toughness, and then consider the otherness of foundry goods body hardness.And solve this large-scale steel-casting, and the nonhomogeneous hardness of the steel casting especially quenching, pertinent literature is not also introduced.
Summary of the invention
The object of this invention is to provide a kind of large-scale steam turbine outer shell casting and heat treating method, when guaranteeing that steel casting properties meets the demands, can also meet the requirement of foundry goods body nonhomogeneous hardness≤± 20HB.
The object of the present invention is achieved like this: a kind of large-scale steam turbine outer shell casting and heat treating method, is characterized in that comprising the steps:
1), when casting, control the quality percentage composition of each component in steel casting raw material:
C 0.18 ~ 0.22(represents that carbon content is 0.18% ~ 0.22% of total mass, lower same)
Si 0.30~0.58
Mn 0.70~0.90
Cr 0.20~0.29
Mo 0.45~0.58
Ni 0.30~0.38
V 0.02~0.03
Surplus is Fe
Control carbon equivalent Ceq value 0.48% ~ 0.54%, wherein carbon equivalent is calculated as follows simultaneously:
Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15, in formula, C, Mn, Cr, Mo, V, Ni, Cu represent respectively the quality percentage composition of each component, the component content not having is 0;
2) to carrying out surface treatment inside and outside the foundry goods obtaining, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residually, then foundry goods carried out to Shot Blasting;
3), before quench treatment, first determine the phase point temperature AC of this material
3, the holding temperature that foundry goods quenches is defined as AC
3+ (50 ~ 100) ℃, during quenching, are heated to AC with the heat-up rate of 70 ~ 80 ℃/h
3+ (50 ~ 100) ℃, water-cooled after insulation 7 ~ 9h;
4) after quenching, carry out tempering, tempering is heated to 690 ~ 705 ℃ with the heat-up rate of 80 ~ 100 ℃/h, after insulation 7 ~ 9h, slowly cools to below 260 ℃ the air cooling of coming out of the stove with stove with 20 ~ 60 ℃/h.
In the present invention, by controlling each component concentration and Ceq value, make foundry goods be convenient to quench treatment, in quenching process, be difficult for hardening crack, make in each batch of composition fluctuation range very littlely, quenching performance is relatively stable simultaneously, and this content range and Ceq value are through a large amount of practice summaries preferred value out.Inside and outside foundry goods, carry out surface treatment and be different from routine techniques means, in prior art, for avoiding casting flaw, often adopt the processing method of large rising head or thick large subsidy, conventional processes flow process is before thermal treatment, to clean out floating sand, cut away rising head and most subsidy, after thermal treatment, then by gouge operation, scab and unnecessary metal are excluded from foundry goods again.By field measurement, contrast, scab is serious, and metal residual after foundry goods subsidy cutting is more, after quenching, removes scab or removes after unnecessary subsidy metal, and the difference in hardness at the position of the non-scab of the hardness under it and foundry goods, nothing subsidy is larger.For this reason, for reducing the impact of this respect, the present invention will clean out all floating sand of foundry goods surfaces externally and internally before foundry goods is heat-treated, and exposes foundry goods body.Casting pressing port and gating system excision is clean; Gouge is removed the part of foundry goods fleshiness, comprises that too much cutting is residual, carries out afterwards Shot Blasting, for nonhomogeneous hardness inside and outside reducing foundry goods performs basis again.During quenching, by temperature increase to transformation temperature above 50 ~ 100 ℃, avoid cast ferrite that part is original in quench cooled process subsequently, because not changing and remain, ferritic existence has soft spots to exist after steel is quenched, thereby affects casting hardness homogeneity; Excess Temperature makes foundry goods oxidation and decarbonization serious, and coarse grains, affects hardness, affects performance.The residual stress that tempering produces in the time of can eliminating workpiece quenching, prevents distortion and cracking; Hardness, intensity, plasticity and the toughness of adjusting workpiece, reach use properties requirement, improves processing characteristics.The method can reduce the nonhomogeneous hardness after large-scale steel-casting quenches, and when guaranteeing that steel casting properties meets the demands, meets the requirement of foundry goods body nonhomogeneous hardness≤± 20HB.The method can be used for producing the steam turbine outer shell that maximum monolateral length is not less than 3000mm.
For guarantee that foundry goods quenches and tempering after hardness even, quench and the interior temperature difference of whole burner hearth during tempering be less than ± 10 ℃.In addition, quenching can be carried out in automatic temperature-controlled quenching tank, during quenching water-cooled, controls water temp within the scope of 20 ° ~ 40 ° C, can guarantee that foundry goods is whole cooling even, finally guarantees that casting hardness is even.
Accompanying drawing explanation
Fig. 1 is component and the Ceq contrast table of each embodiment.
Fig. 2 is foundry goods test block mechanical property contrast table.
Embodiment
The following large-scale steam turbine outer shell of executing in example is the outer shell of steam turbine, and its maximum monolateral length is not less than 3000mm.
Embodiment 1
Large-scale steam turbine outer shell casting and a heat treating method, comprise the steps:
1), when casting, control the quality percentage composition of each component in steel casting raw material:
C 0.20
Si 0.44
Mn 0.85
Cr 0.23
Mo 0.51
Ni 0.33
V 0.025
Surplus is Fe,
Its carbon equivalent Ceq value is 0.52%, and wherein carbon equivalent is calculated as follows
Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15, in formula, C, Mn, Cr, Mo, V, Ni, Cu represent respectively the quality percentage composition of each component, Cu content is 0.
2) to carrying out surface treatment inside and outside the foundry goods obtaining, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residually, then foundry goods carried out to Shot Blasting.
3), before quench treatment, first determine the phase point temperature AC of this material
3, the holding temperature that foundry goods quenches is defined as AC
3+ 50 ℃, in the present embodiment, phase point temperature is 880 ℃, during quenching, with the heat-up rate of 70 ~ 80 ℃/h, is heated to 930 ~ 940 ℃, water-cooled after insulation 7h.
4) after quenching, carry out tempering, tempering is heated to 690 ℃ with the heat-up rate of 80 ℃/h, after insulation 7h, slowly cools to below 260 ℃ the air cooling of coming out of the stove with stove with 20 ℃/h.
Quench and the interior temperature difference of whole burner hearth during tempering be less than ± 10 ℃.Quenching is carried out in automatic temperature-controlled quenching tank, during quenching water-cooled, controls water temp within the scope of 20 ° ~ 40 ° C.
Embodiment 2
Another large-scale steam turbine outer shell casting and heat treating method, its step is as follows:
1), when casting, control the quality percentage composition of each component in steel casting raw material:
C 0.20
Si 0.45
Mn 0.78
Cr 0.25
Mo 0.49
Ni 0.35
V 0.024
Surplus is Fe
Now, carbon equivalent Ceq value is 0.51%, and wherein carbon equivalent calculation formula is with embodiment 1.
2) to carrying out surface treatment inside and outside the foundry goods obtaining, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residually, then foundry goods carried out to Shot Blasting.
3), before quench treatment, first determine the phase point temperature AC of this material
3, in the present embodiment, phase point temperature is 875 ℃, the holding temperature that foundry goods quenches is defined as 975 ℃, during quenching, with the heat-up rate of 80 ℃/h, is heated to 965 ~ 975 ℃, water-cooled after insulation 9h.
4) after quenching, carry out tempering, tempering is heated to 705 ℃ with the heat-up rate of 100 ℃/h, after insulation 9h, slowly cools to below 260 ℃ the air cooling of coming out of the stove with stove with 60 ℃/h.
Quench and the interior temperature difference of whole burner hearth during tempering be less than ± 10 ℃.Quenching is carried out in automatic temperature-controlled quenching tank, during quenching water-cooled, controls water temp within the scope of 20 ° ~ 40 ° C.
Embodiment 3
Large-scale steam turbine outer shell casting and a heat treating method, step is as follows:
1) first cast, when casting, control the quality percentage composition of each component in steel casting raw material:
C 0.18
Si 0. 58
Mn 0.80
Cr 0.23
Mo 0.45
Ni 0. 38
V 0. 03
Surplus is Fe
Carbon equivalent Ceq value is 0.48%, and wherein carbon equivalent calculation formula is with embodiment 1.
2) to carrying out surface treatment inside and outside the foundry goods obtaining, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residually, then foundry goods carried out to Shot Blasting;
3) before quench treatment, first determine the phase point temperature AC3 of this material, the holding temperature that foundry goods quenches is defined as AC
3+ (50 ~ 100) ℃, during quenching, are heated to AC with the heat-up rate of 70 ~ 80 ℃/h
3+ (50 ~ 100) ℃, water-cooled after insulation 8h;
4) after quenching, carry out tempering, tempering is heated to 700 ℃ with the heat-up rate of 90 ℃/h, after insulation 8h, slowly cools to below 260 ℃ the air cooling of coming out of the stove with stove with 40 ℃/h.
Quench and the interior temperature difference of whole burner hearth during tempering be less than ± 10 ℃.Quenching is carried out in automatic temperature-controlled quenching tank, during quenching water-cooled, controls water temp within the scope of 20 ° ~ 40 ° C.
Embodiment 4
For another large-scale steam turbine outer shell casting and heat treating method, be with the difference of embodiment 3:
When casting, control the quality percentage composition of each component in steel casting raw material:
C 0.20
Si 0.30
Mn 0. 90
Cr 0.20
Mo 0.45
Ni 0.30
V 0.02
Surplus is Fe
Its carbon equivalent Ceq value 0.50%.
Embodiment 5
Large-scale steam turbine outer shell casting and a heat treating method, be with the difference of embodiment 1: when casting, control the quality percentage composition of each component in steel casting raw material:
C 0.22
Si 0.40
Mn 0.75
Cr 0.20
Mo 0.45
Ni 0.30
V 0.028
Surplus is Fe
Control carbon equivalent Ceq value 0.50% simultaneously.
Embodiment 6
Large-scale steam turbine outer shell casting and a heat treating method, be with the difference of embodiment 2: when casting, control the quality percentage composition of each component in steel casting raw material:
C 0.21
Si 0.58
Mn 0.90
Cr 0.28
Mo 0.49
Ni 0.32
V 0.026
Surplus is Fe
Carbon equivalent Ceq value is 0. 54%.
Embodiment 7
Large-scale steam turbine outer shell casting and a heat treating method, be with the difference of embodiment 2: when casting, control the quality percentage composition of each component in steel casting raw material:
C 0.19
Si 0.42
Mn 0.70
Cr 0.29
Mo 0. 58
Ni 0.30
V 0.03
Surplus is Fe
Carbon equivalent Ceq value is 0.51%.
The holding temperature that foundry goods quenches is defined as AC
3+ 75 ℃.
In Fig. 1 and Fig. 2, the foundry goods in respectively corresponding each embodiment of part 1 ~ part 7.Each position hardness difference of the body of foundry goods is 16HB to the maximum, the requirement of < ± 20HB, and each foundry goods multiple spot hardness detected value wave pattern is as shown in Figure 1.The every mechanical performance index result of this series products test block is as table 2, and the hardness average of test block and the hardness average of foundry goods body are less than 6HB, all meet the requirements.
The present invention is not limited to above-described embodiment; on the basis of technical scheme disclosed by the invention; those skilled in the art is according to disclosed technology contents; do not need performing creative labour just can make some replacements and distortion to some technical characterictics wherein, these replacements and distortion are all in protection scope of the present invention.
Claims (3)
1. large-scale steam turbine outer shell casting and a heat treating method, is characterized in that comprising the steps:
1), when casting, control the quality percentage composition of each component in steel casting raw material:
C 0.18~0.22
Si 0.30~0.58
Mn 0.70~0.90
Cr 0.20~0.29
Mo 0.45~0.58
Ni 0.30~0.38
V 0.02~0.03
Surplus is Fe
Control carbon equivalent Ceq value is 0.48% ~ 0.54% simultaneously, and wherein carbon equivalent is calculated as follows
Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15, in formula, C, Mn, Cr, Mo, V, Ni, Cu represent respectively the quality percentage composition of each component, the component content not having is 0;
2) to carrying out surface treatment inside and outside the foundry goods obtaining, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residually, then foundry goods carried out to Shot Blasting;
3), before quench treatment, first determine the phase point temperature AC of this material
3, the holding temperature that foundry goods quenches is defined as AC
3+ (50 ~ 100) ℃, during quenching, are heated to AC with the heat-up rate of 70 ~ 80 ℃/h
3+ (50 ~ 100) ℃, water-cooled after insulation 7 ~ 9h;
4) after quenching, carry out tempering, tempering is heated to 690 ~ 705 ℃ with the heat-up rate of 80 ~ 100 ℃/h, after insulation 7 ~ 9h, slowly cools to below 260 ℃ the air cooling of coming out of the stove with stove with 20 ~ 60 ℃/h.
2. a kind of large-scale steam turbine outer shell casting according to claim 1 and heat treating method, is characterized in that: quench and the interior temperature difference of whole burner hearth during tempering be less than ± 10 ℃.
3. a kind of large-scale steam turbine outer shell casting according to claim 1 and treatment process, is characterized in that: quench and carry out in automatic temperature-controlled quenching tank, during quenching water-cooled, control water temp within the scope of 20 ° ~ 40 ° C.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105483341A (en) * | 2015-12-15 | 2016-04-13 | 常熟市汇海机械制造有限责任公司 | Heat treatment technology of large steel casting |
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| CN103993244A (en) * | 2014-05-28 | 2014-08-20 | 北京机电院高技术股份有限公司 | Low-alloy cast steel joint as well as smelting and pouring control method and heat treatment process thereof |
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2014
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| JPS5519304B2 (en) * | 1974-09-30 | 1980-05-24 | ||
| CN102965588A (en) * | 2012-11-29 | 2013-03-13 | 南车戚墅堰机车车辆工艺研究所有限公司 | Low-alloy high-strength cast steel, and smelting and heat treatment method thereof |
| CN103993244A (en) * | 2014-05-28 | 2014-08-20 | 北京机电院高技术股份有限公司 | Low-alloy cast steel joint as well as smelting and pouring control method and heat treatment process thereof |
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| 史学亮等: "600MW高中压外缸的精整", 《金属加工（热加工）》, no. 23, 31 December 2013 (2013-12-31) * |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105483341A (en) * | 2015-12-15 | 2016-04-13 | 常熟市汇海机械制造有限责任公司 | Heat treatment technology of large steel casting |
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Effective date of registration: 20160218 Address after: 750021 the Ningxia Hui Autonomous Region Yinchuan Tongxin economic and Technological Development Zone No. 199 South Street Applicant after: Share cast steel Co., Ltd Address before: 750000, Beijing West Road, Xixia District, the Ningxia Hui Autonomous Region, 550, Yinchuan Applicant before: KOCEL Machinery Co., Ltd. Applicant before: Ningxia Kocel Group Co., Ltd. |
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