CN104004969B - The casting of a kind of Large steam turbine outer shell and heat treating method - Google Patents
The casting of a kind of Large steam turbine outer shell and heat treating method Download PDFInfo
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Abstract
The present invention relates to a kind of Large steam turbine outer shell casting in casting and technical field of heat treatment and heat treating method, when casting, controlling the mass percentage of each component of steel casting; Control Ceq value is 0.48% ~ 0.54% simultaneously; Then, carry out surface treatment to inside and outside foundry goods, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then carry out Shot Blasting to foundry goods; The holding temperature of foundry goods quenching is defined as AC3+(50 ~ 100) DEG C, water-cooled after insulation 7 ~ 9h; After tempering, air cooling of coming out of the stove.In the present invention, by controlling each component concentration and Ceq value, make foundry goods be convenient to quench treatment, very little in each batch of composition fluctuation range, quenching performance is relatively stable; The method can reduce the nonhomogeneous hardness after large-scale steel-casting quenching, foundry goods body nonhomogeneous hardness≤± 20HB.The method can be used for the steam turbine outer shell that the maximum monolateral length of production is not less than 3000mm.
Description
Technical field
Patent of the present invention relates to a kind of casting and heat-treating methods, particularly the casting of Large 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 manufacturing is very difficult, and before my company, domestic also do not have manufacturer successfully to produce, and also only has a steel foundry of Poland successfully to produce in the world.This steel casting material is G20Mo5, belongs to low alloy steel.Often overlap foundry goods and be 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.The wall thickness at upper bottom half cast element entity more than 75% position is 60mm, thickest 290mm.This type of outer shell foundry goods is half rotary structure, and main-cylinder wall therefrom divides the bias towards horizontal integration face flange to reach more than 9%.
Such product material mechanical property requirements is higher: tensile strength requires 440 ~ 590MPa, yield strength >=245MPa, unit elongation >=22%, room temperature impact merit AKv >=27J, Brinell hardness requires 130 ~ 175HB, and requiring that single foundry goods body divides equally detection 5 positions, each position hardness value difference is less than 20HB, and in a collection of foundry goods, the average hardness value of all foundry goods differs can not exceed ± more than 20HB with the detected result of sample.This is for large-scale steel-casting, and difficulty is very large; G20Mo5 material is low alloy steel, but requires higher over-all properties, and especially impact requires high.Adopt traditional normalizing method, impact very difficult stablizing and reach customer requirement.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 solving this large-scale steel-casting, the nonhomogeneous hardness of the steel casting especially quenched, pertinent literature is not also introduced.
Summary of the invention
The object of this invention is to provide the casting of a kind of Large steam turbine outer shell and heat treating method, while guarantee steel casting properties meets the demands, the requirement of foundry goods body nonhomogeneous hardness≤± 20HB can also be met.
The object of the present invention is achieved like this: a kind of Large steam turbine outer shell casting and heat treating method, is characterized in that comprising the steps:
1) when casting, the mass percentage of each component in steel casting raw material is controlled:
C0.18 ~ 0.22(represents that carbon content is 0.18% ~ 0.22% of total mass, lower same)
Si0.30~0.58
Mn0.70~0.90
Cr0.20~0.29
Mo0.45~0.58
Ni0.30~0.38
V0.02~0.03
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 the mass percentage of each component respectively, and the component content do not had is 0;
2) carry out surface treatment to inside and outside the foundry goods obtained, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residual, then Shot Blasting is carried out to foundry goods;
3), before quench treatment, the phase point temperature AC of this material is first determined
3, the holding temperature of foundry goods quenching is defined as AC
3+ (50 ~ 100) DEG C, during quenching, are heated to AC with the heat-up rate of 70 ~ 80 DEG C/h
3+ (50 ~ 100) DEG C, water-cooled after insulation 7 ~ 9h;
4) carry out tempering after quenching, tempering is heated to 690 ~ 705 DEG C with the heat-up rate of 80 ~ 100 DEG C/h, after insulation 7 ~ 9h, slowly cools to less than 260 DEG C, air cooling of coming out of the stove with stove with 20 ~ 60 DEG C/h.
In the present invention, by controlling each component concentration and Ceq value, foundry goods is made to be convenient to quench treatment, not easily hardening crack in quenching process, make in each batch of composition fluctuation range very little, quenching performance is relatively stable, and this content range and Ceq value are through a large amount of practice summaries preferred value out simultaneously.Carry out surface treatment inside and outside foundry goods 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 cleans out floating sand before thermal treatment, cut away rising head and most subsidy, after thermal treatment, then by gouge operation, scab and unnecessary metal are excluded from foundry goods again.Contrasted by field measurement, scab is serious, and metal residual after foundry goods subsidy cutting is more, after quenching, removes scab or after removing unnecessary subsidy metal, the hardness it under and the non-scab of foundry goods, larger without the difference in hardness at the position of subsidizing.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 are excised clean; The part of foundry goods fleshiness removed by gouge, comprises too much cutting and remains, carry out Shot Blasting more afterwards, for inside and outside reduction foundry goods, nonhomogeneous hardness performs basis.During quenching, by more than temperature increase to transformation temperature 50 ~ 100 DEG C, the cast ferrite avoiding part original, in quench cooled process subsequently, remains because not changing, ferritic existence has soft spots to exist after steel is quenched, thus affects casting hardness homogeneity; Temperature is too high, and make foundry goods oxidation and decarbonization serious, coarse grains, affects hardness, affects performance.The residual stress that tempering produces when can eliminate workpiece quenching, prevents distortion and cracking; Adjust the hardness of workpiece, intensity, plasticity and toughness, reach use properties requirement, improve processing characteristics.The method can reduce the nonhomogeneous hardness after large-scale steel-casting quenching, while ensureing that steel casting properties meets the demands, meets the requirement of foundry goods body nonhomogeneous hardness≤± 20HB.The method can be used for the steam turbine outer shell that the maximum monolateral length of production is not less than 3000mm.
Even for ensureing the hardness after foundry goods Quench and temper, in the whole burner hearth during Quench and temper temperature difference be less than ± 10 DEG C.In addition, quenching can be carried out in automatic temperature-controlled quenching tank, and during quenching water-cooled, control water temp, within the scope of 20 ° ~ 40 ° C, can ensure the cooling of foundry goods entirety evenly, and final guarantee 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 steam turbine outer shell executed in example is the outer shell of steam turbine, and its maximum monolateral length is not less than 3000mm.
Embodiment 1
The casting of a kind of Large steam turbine outer shell and heat treating method, comprise the steps:
1) when casting, the mass percentage of each component in steel casting raw material is controlled:
C0.20
Si0.44
Mn0.85
Cr0.23
Mo0.51
Ni0.33
V0.025
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 the mass percentage of each component respectively, and Cu content is 0.
2) carry out surface treatment to inside and outside the foundry goods obtained, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residual, then Shot Blasting is carried out to foundry goods.
3), before quench treatment, the phase point temperature AC of this material is first determined
3, the holding temperature of foundry goods quenching is defined as AC
3+ 50 DEG C, in the present embodiment, phase point temperature is 880 DEG C, during quenching, is heated to 930 ~ 940 DEG C with the heat-up rate of 70 ~ 80 DEG C/h, water-cooled after insulation 7h.
4) carry out tempering after quenching, tempering is heated to 690 DEG C with the heat-up rate of 80 DEG C/h, after insulation 7h, slowly cools to less than 260 DEG C, air cooling of coming out of the stove with stove with 20 DEG C/h.
In whole burner hearth during Quench and temper the temperature difference be less than ± 10 DEG C.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
The casting of another Large steam turbine outer shell and heat treating method, its step is as follows:
1) when casting, the mass percentage of each component in steel casting raw material is controlled:
C0.20
Si0.45
Mn0.78
Cr0.25
Mo0.49
Ni0.35
V0.024
Surplus is Fe
Now, carbon equivalent Ceq value is 0.51%, and wherein carbon equivalent calculation formula is with embodiment 1.
2) carry out surface treatment to inside and outside the foundry goods obtained, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residual, then Shot Blasting is carried out to foundry goods.
3), before quench treatment, the phase point temperature AC of this material is first determined
3, in the present embodiment, phase point temperature is 875 DEG C, and the holding temperature of foundry goods quenching is defined as 975 DEG C, during quenching, is heated to 965 ~ 975 DEG C with the heat-up rate of 80 DEG C/h, water-cooled after insulation 9h.
4) carry out tempering after quenching, tempering is heated to 705 DEG C with the heat-up rate of 100 DEG C/h, after insulation 9h, slowly cools to less than 260 DEG C, air cooling of coming out of the stove with stove with 60 DEG C/h.
In whole burner hearth during Quench and temper the temperature difference be less than ± 10 DEG C.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
The casting of a kind of Large steam turbine outer shell and heat treating method, step is as follows:
1) first casting, when casting, controlling the mass percentage of each component in steel casting raw material:
C0.18
Si0.58
Mn0.80
Cr0.23
Mo0.45
Ni0.38
V0.03
Surplus is Fe
Carbon equivalent Ceq value is 0.48%, and wherein carbon equivalent calculation formula is with embodiment 1.
2) carry out surface treatment to inside and outside the foundry goods obtained, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residual, then Shot Blasting is carried out to foundry goods;
3) before quench treatment, first determine the phase point temperature AC3 of this material, the holding temperature of foundry goods quenching is defined as AC
3+ (50 ~ 100) DEG C, during quenching, are heated to AC with the heat-up rate of 70 ~ 80 DEG C/h
3+ (50 ~ 100) DEG C, water-cooled after insulation 8h;
4) carry out tempering after quenching, tempering is heated to 700 DEG C with the heat-up rate of 90 DEG C/h, after insulation 8h, slowly cools to less than 260 DEG C, air cooling of coming out of the stove with stove with 40 DEG C/h.
In whole burner hearth during Quench and temper the temperature difference be less than ± 10 DEG C.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 the casting of another Large steam turbine outer shell and heat treating method, be with the difference of embodiment 3:
When casting, control the mass percentage of each component in steel casting raw material:
C0.20
Si0.30
Mn0.90
Cr0.20
Mo0.45
Ni0.30
V0.02
Surplus is Fe
Its carbon equivalent Ceq value 0.50%.
Embodiment 5
The casting of a kind of Large steam turbine outer shell and heat treating method, be with the difference of embodiment 1: when casting, and controls the mass percentage of each component in steel casting raw material:
C0.22
Si0.40
Mn0.75
Cr0.20
Mo0.45
Ni0.30
V0.028
Surplus is Fe
Control carbon equivalent Ceq value 0.50% simultaneously.
Embodiment 6
The casting of a kind of Large steam turbine outer shell and heat treating method, be with the difference of embodiment 2: when casting, and controls the mass percentage of each component in steel casting raw material:
C0.21
Si0.58
Mn0.90
Cr0.28
Mo0.49
Ni0.32
V0.026
Surplus is Fe
Carbon equivalent Ceq value is 0.54%.
Embodiment 7
The casting of a kind of Large steam turbine outer shell and heat treating method, be with the difference of embodiment 2: when casting, and controls the mass percentage of each component in steel casting raw material:
C0.19
Si0.42
Mn0.70
Cr0.29
Mo0.58
Ni0.30
V0.03
Surplus is Fe
Carbon equivalent Ceq value is 0.51%.
The holding temperature of foundry goods quenching is defined as AC
3+ 75 DEG C.
In Fig. 1 and Fig. 2, the foundry goods in the corresponding each embodiment of part 1 ~ part 7 difference.Body each position hardness difference of foundry goods is 16HB to the maximum, the requirement of < ± 20HB, and each foundry goods multiple spot hardness determination value wave pattern 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 to some technical characteristics wherein to replace and distortion, these are replaced and are out of shape all in protection scope of the present invention.
Claims (1)
1. the casting of Large steam turbine outer shell and a heat treating method, is characterized in that comprising the steps:
1) when casting, the mass percentage of each component in steel casting raw material is controlled:
C0.18~0.22
Si0.30~0.58
Mn0.70~0.90
Cr0.20~0.29
Mo0.45~0.58
Ni0.30~0.38
V0.02~0.03
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 the mass percentage of each component respectively, and the component content do not had is 0;
2) carry out surface treatment to inside and outside the foundry goods obtained, adopt gouge to exclude floating sand, excision casting pressing port and casting system, then, exclude foundry goods fleshiness part and cut residual, then Shot Blasting is carried out to foundry goods;
3), before quench treatment, the phase point temperature AC of this material is first determined
3, the holding temperature of foundry goods quenching is defined as AC
3+ (50 ~ 100) DEG C, during quenching, are heated to AC with the heat-up rate of 70 ~ 80 DEG C/h
3+ (50 ~ 100) DEG C, water-cooled after insulation 7 ~ 9h; Quenching is carried out in automatic temperature-controlled quenching tank, during quenching water-cooled, controls water temp within the scope of 20 ~ 40 DEG C; In whole burner hearth during quenching the temperature difference be less than ± 10 DEG C;
4) quenching after carry out tempering, tempering is heated to 690 ~ 705 DEG C with the heat-up rate of 80 ~ 100 DEG C/h, insulation 7 ~ 9h after, slowly cool to less than 260 DEG C with stove with 20 ~ 60 DEG C/h, air cooling of coming out of the stove, in the whole burner hearth during tempering temperature difference be less than ± 10 DEG C.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
-
2014
- 2014-05-30 CN CN201410236540.XA patent/CN104004969B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
Non-Patent Citations (2)
| Title |
|---|
| 600MW高中压外缸的精整;史学亮等;《金属加工（热加工）》;20131231(第23期);全文 * |
| 蒸汽-燃气联合循环机组高中压外缸铸件研发;张立文等;《第十届中国铸造协会年会会刊（论文篇）》;20121231;全文 * |
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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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