CN100534670C - Fine casting method for super long lower pressure partition guide blade of turbine in stainless steel investment mold - Google Patents

Abstract

The present invention discloses precise investing process of super long low pressure partition guide blade of stainless steel for turbine. Crankled stainless steel guide blade with length up to 960 mm and weight up to 42 kg may be manufactured through investing process. The present invention adopts pre-deforming profiling design and improved investing process and the produced guide blade for 600 KW steam turbo generator has high performance. The investing process includes making wax mold, making shell, smelting and casting, and heat treatment.

Description

The fine casting method of super long lower pressure partition guide blade of turbine in stainless steel investment mold

Technical field:

The present invention is a kind of metal precision casting technology, specifically the hot investment casting of steam turbine overlength low voltage partition plate guide vane.

Technical background:

At present, the thermal power generation unit of China's maximum is 600,000 kilowatts of Turbo-generator Set introducing from US Westinghouse company.Wherein the material of low pressure (LP) cylinder final stage guide vane, mechanical property, chemical composition, surface roughness, physical dimension all have strict demand.It should be the design and the manufacturing of die mould that the frock of full form casting process is prepared.Accompanying drawing one is the structure chart of final stage guide vane, the complexity of its shape, size, molded lines.As can be seen from the figure this blade bending degree is bigger, and thickest is 62 millimeters of φ, only 8 millimeters of lagging edge thinnest parts, and foundry goods reaches and can reach 950 millimeters.US Westinghouse company adopts the precision die forging blank, carries out rubbing down processing then.The steam turbine guide vane that domestic present employing full form casting process is produced is no longer than 500 millimeters, and weight is no more than 10 kilograms.According to external report and the international model casting nd Annual Meeting collection published, and international casting exhibition club interrelated data, the in kind introduction of collecting, MIT and Kubota Corporation once adopted this technology to make the large-size steam turbine guide vane.In Beijing international fair in 1986, model casting stator length of a film 400 millimeter that Japanese Kubota Corporation puts on display.350,000 kilowatts of Steam Turbine that MIT makes are installed in Shanghai Golconda steel mill, and its low pressure (LP) cylinder end two-stage guide vane also is to adopt full form casting process to produce.According to the international technology data searching, the large-size steam turbine guide vane that adopts full form casting process to produce at present has only the flourishing capitalist country of a few industry such as Britain, the U.S., Japan, West Germany.But there are not particulars specifically to introduce ins and outs.

Summary of the invention:

The present invention seeks to disclose a kind of fine casting method of super long lower pressure partition guide blade of turbine in stainless steel investment mold.Adopt full form casting process to produce foundry goods and reach and can reach 950 millimeters, spray weigh more than 42 kilograms the stainless steel crankle guide bucket.Adopt the design of predeformation die mould; The full form casting process method has been carried out than major tuneup, meet the strict designing requirement such as material, mechanical property, chemical composition, surface roughness, physical dimension of 600,000 kilowatts of low pressure (LP) cylinder final stage guide vanes in the Turbo-generator Set fully, reached advanced international level, the guide vane that adopts this process to produce, can save a large amount of raw material, the product percent of pass height obtains favorable economic benefit.

The inventive method is:

1 system wax-pattern

1.1 press shape, size, the molded lines design wax-pattern 1 of steam turbine low-pressure dividing plate guide vane,, add suitable molding allowance by statistical law being difficult to predict and being out of shape not the very position of rule.

1.2 configuration paraffin is got paraffin 50%, stearic acid 50% mixes, and is used for wax-type material.The mould material is stirred into paste, temperature remain on 42～48 (℃), on semi-automatic pressure wax cylinder, suppress.Dwell time 〉=1 hour

1.3, repair blemish, deflashing, burr with the wax-pattern after the moulding.

1.4 assembly welding will be justified rising head 2 and be welded in the maximum blade thickness place, vane end faces connects with process bar 3 by lagging edge place and distance weldering 1/3 place, rising head top.

1.5 with 95% alcohol wash module, do the back and check no dry joint, wax bits, no oil stain.

1.6 module is placed on loose tool 4, on loose tool, repairs wax-pattern.

1.7 the module that welds hangs on the suspender, before the system shell, in lagging edge 5, back of the body arc 1/2nd places will coat rosin, alcoholic solution.

2 system shells

2.1, to select rapidly-dried silica sol for use be binding agent,

2.2 preparation coating

Coating 6 is prepared according to coating

Ground floor is Ludox+zirconium English powder; Dope viscosity 25-30 (S), the sand fineness 100 order second layers are above to be Instant cement+mullite powder, dope viscosity 9-13 (S), sand fineness 10-60 (order)

Each order is counted sand and is screened out the use of caking back with screen pack, is coated with slip and stirs fully, evenly waits for quietly using behind the bubble floating.

Hang the system shell 2.3 be coated with, be coated with rapidly-dried silica sol on wax-pattern, lagging edge and back of the body arc part are particularly advanced in stucco, and each stucco is wanted evenly, mould crust thickness 15--18MM.

2.4 it is air-dry

Whenever be coated with one deck, air-dry 2----24 hour, natural air drying.

2.5 dewaxing Fu fast dewaxing, steam dewaxing, vapor (steam) temperature 140-160 degree centigrade, pressure 4--5 atmospheric pressure, temperature retention time 10--12 minute are adopted in dewaxing, dewaxing.

2.6 high-temperature roasting

Carry out at roaster, when being warmed up to 800--900 degree centigrade, being incubated and naturally cooling to normal temperature after 2--3 hour.

3. smelting and pouring

3.1 adopting intermediate frequency furnace smelts Austria's body stainless steel.

3.2 with the formwork sandbox of packing into, the shell spacing should be greater than 150MM, with heat-insulating property preferably granularity be that the bauxite sand of φ 3-φ 5 is as the back-up sand material, filling moulding, the sandbox ceramic paste material 7 of sealing up suitable for reading, shell and sandbox roasting process temperature should remain on 850 degrees centigrade, and temperature retention time was more than or equal to 30 minutes

3.3 casting

Tapping temperature should be in the time of 1600 degrees centigrade; During 1580 degrees centigrade of cast temperatures, casting rate 3 Kilograms Per Seconds, the time of unpacking was greater than 5 hours

Adopt inclined casting, with the sandbox certain angle that tilts, make that molten steel is average to be flowed in the shell along lagging edge quietly, then sandbox is erected, shell is filled with, casting process will be finished at 5-8 second.

3.4

The foundry goods that waters, shake out time surrounded the shell of foundry goods and remove with vibrating method more than or equal to 12 hours, with cast gate and the excision of technology head, carried out blasting treatment, sprayed clean foundry goods and carried out 100% surface inspection, and casting flaw mustn't be arranged.

4. heat treatment

The blade and the coupon of each heat lot are handled with stove, avoid the blade stacking distortion, and the blade of coming out of the stove will be put down gently, in order to avoid the distortion of colliding with.When blade is raised to 1040----1100 degree centigrade with furnace temperature in stove; Wait to grill thoroughly back insulation 1 minute/millimeter, air cooling is to normal temperature then.

Description of drawings

Fig. 1 is a wax-pattern structure chart of the present invention;

Fig. 2 is the pressurize loose tool schematic diagram of guide vane wax-pattern of the present invention;

Fig. 3 is casting condition figure of the present invention.

The specific embodiment:

The present invention selects once to suppress the pressure-type structure of single-piece, and the die cavity total shrinkage is 2.5%.Manufacture and design in the process at die mould, according to the characteristics of blade itself, actual conditions such as became uneven are being difficult to predict and are being out of shape not very that the position of rule adds suitable molding allowance.Promptly at the leading edge position that thermal center is relatively concentrated, back of the body arc approaches the position, and the die mould position grinds off part amount relatively.By groping the blade of some, find out the regularity of deformable blade.Calculate each cross section of each blade and detect the light leak value of model relatively, calculate the absolute value of deformation place,, revise the die cavity of die mould in corresponding position to die mould.

Selecting for use of mould material, adopt paraffin and stearic acid low temperature mould material, its proportioning is paraffin+stearic acid: the mould material is stirred into paste, temperature remain on 42～48 (℃), on semi-automatic pressure wax cylinder, suppress.Dwell time is a very important parameters.Find out dwell time 〉=1 of guide vane fusible pattern on mould hour.After obtaining a desirable fusible pattern, the guide vane wax-pattern that makes to be placed on the loose tool for preventing its distortion, see figure two, on loose tool, repair wax-pattern.

After checking, qualified guide vane wax-pattern assembly welding is on rising head.The module that welds hangs on the suspender.Before the system shell, lagging edge is interior, back of the body arc 1/2nd places will coat the rosin alcoholic solution, is in order to increase ADHESION OF PAINTS power.

Traditional handicraft is an alkaline silica sol, is the environmental-friendly water-base product, and is cheap, pH value 9-10.

Make SiO in the Ludox by water evaporates ₂Valence link interconnected after ion shrank, and made the micelle of disperse produce gel, set up strength of coating.Because the speed of water evaporates directly influences the drying time and the dried wet strength of coating, therefore, in use there is certain problem in ordinary silicon colloidal sol.

Shortcoming is:

Drying time long, wet strength is set up slow and lower, the system shell cycle long.

2. temperature, humidity and the wind speed to environment has strict requirement.Temperature, humidity and change of wind velocity, what can cause investment precoat splits quality problems such as shell, peeling, and the undercapacity of shell directly influences casting quality.

3. wet strength is low, the elevated temperature strength height.The former is unfavorable for operation, and the latter then makes shell cast back collapsibility poor, is unfavorable for shell clearly.

Rapidly-dried silica sol of the present invention is that alkaline water-based Ludox is an environmentally friendly machine, pH value 8.5-10.1.Fast dried principle is that high polymer impels SiO as catalyst by selectable adding high polymer ₂The water balance point of micelle gel improves, and slurry coating is behind coated sand material, and the absorption of sand material impels moisture wherein to exosmose rapidly, makes the moisture of pulp layer reach the equalization point of gel, begins to form gel, sets up wet strength fast.Simultaneously, the high polymer of even dispersion has good drainage performance, impels the moisture in the pulp layer to get rid of fast, evaporate, and further promotes gel, improves wet strength.

Advantage is:

1. increase the elasticity and the wet strength of investment precoat, reduce or to remove surface layer dry too fast and casting structure causes splits quality problems such as shell, peeling.

2. dewatering is good, forms the coating of uniform drying easily.

3. increase the adhesive force of Ludox and refractory powder, increase the adhesion strength and the coated property of slurry and refractory aggregate, increase investment shell intensity, reduce coating and shell thickness.

4. improve the gas permeability of shell.Roasting makes the high polymer volatilization, forms fine exhaust passage in shell, increases gas permeability, reduces the defectives such as misrun of foundry goods to the thin thin place of current.

5. the shell retained strength is low.The volatilization of high polymer has reduced the shell retained strength, easily clear shell.

6. lower to environmental requirement, help the stable of production technology and quality.

7. rapid draing, interlayer drying time 1 ~ 2h.

8. water base, environmentally friendly machine.

9. stable performance, long shelf-life (1 year).

Tasteless during silica sol binder system shell, easy to use, the preparation paint stability is good, and the shell performance is good, but ordinary silicon sol paint rate of drying is slow, and wet strength is low. and system shell cycle length is the subject matter in using.The rapidly-dried silica sol technology generations is for Ludox---silester composite shell technology, not only shell wet strength height, system shell cycle lack, and elevated temperature strength is all low suitable with the silester shell than Ludox with retained strength, the interlayer drying time shorten to 1-2 (h) during the system shell, and on shell performance, system shell speed approaching comprehensively international rapidly-dried silica sol level.

Success of the present invention produce foundry goods for 300,000 kilowatts, 600,000 kilowatts steam turbine low-pressure dividing plate final stages of optimization machine master guide vane, weight is 42 kilograms, casting length is 950 millimeters, the shell length overall, promptly casting length+guide vane rising head is long 1150 millimeters altogether.

The module that assembles forwards system shell operation to and is coated with extension system shell, produces by multilayer rapidly-dried silica sol process for making shell.Each stucco will be noted the module lagging edge down, pays special attention to the stucco of lagging edge, is coated with extension and wants evenly shell thickness requirement 15-18 millimeter.The shell that makes, big after wind 12-24 hour, dewaxing, roasting.Dewaxing still fast dewaxing is adopted in dewaxing, is about 10-12 minute in 4--5 atmospheric pressure, 140 ℃-150 ℃ of holding temperatures, temperature retention time, carries out high-temperature roasting then, and sintering temperature is 850 ℃, and roasting time was more than or equal to 1.5 hours.Blade material is austenitic stainless steel ZG0Cr19Ni9.Can add 50% foundry returns in the smelting process, rising head is when the foundry returns use.Adopt GGW-0.15 type or GW-0.15 controllable silicon intermediate frequency furnace to smelt.With the formwork sandbox of packing into, with heat-insulating property preferably granularity be that the bauxite sand of ∮ 3-∮ 5 is as back-up sand material filling moulding.The sandbox ceramic paste material of sealing up suitable for reading.The batching of ceramic paste material adopts water-glass sand+CO ₂Hardening process is in case sand sand in roaster roasting or inclined casting process flows out.Temperature is controlled at 850 ℃ in shell and the sandbox roasting process.Temperature retention time adopted inclined casting more than or equal to 30 minutes in the molten steel fusion process, and this is the method for comparison key.If so big blade adopts upright the notes, the static pressure head height, molten steel is big to shell bottom impulsive force, waters full shell oppose side wall and also can produce very big expansive force, can cause shell bottom or edge runout and scraps.Be to reduce impact and the expansive force of molten steel to bottom and sidewall, with the sandbox certain angle that tilts, molten steel is flowed in the shell reposefully along lagging edge, then sandbox is erected, shell is filled with, whole casting process will be finished in 5-8 kind second.Tapping temperature is controlled at 1600 ℃, and pouring temperature is controlled at 1580 ℃.

Claims (1)

1. the fine casting method of a super long lower pressure partition guide blade of turbine in stainless steel investment mold, its processing step is:

One, system wax-pattern

1.1, press shape, size, the molded lines design wax-pattern (1) of steam turbine low-pressure dividing plate guide vane, being difficult to predict and being out of shape not the very position of rule, add suitable molding allowance by statistical law;

1.2, preparation paraffin, get paraffin 50%, stearic acid 50% and mix, be used for wax-type material; Wax-type material is stirred into paste, and temperature remains on 42-48 degree centigrade, suppresses dwell time 〉=1 hour on semi-automatic pressure wax cylinder;

1.3, with the wax-pattern after the moulding, repair blemish, deflashing, burr;

1.4, assembly welding, weld cap mouth (2) is welded in the maximum blade thickness place, vane end faces is positioned at apart from 1/3 place, weld cap mouth top by the lagging edge place, connects with process bar (3);

1.5, with 95% alcohol wash module, do the back and check that no dry joint, wax are considered to be worth doing, no oil stain;

1.6, module is placed on loose tool (4), on loose tool, repair wax-pattern;

1.7, the module that welds hangs on the suspender, before the system shell, in lagging edge (5), back of the body arc 1/2nd places will coat rosin, alcoholic solution;

Two, system shell

2.1, to select fast dried silicon melten gel for use be binding agent;

2.2, the configuration coating

Coating (4) is prepared according to coating;

Ground floor is fast dried silicon melten gel+zirconium English powder, dope viscosity 25-30S, sand fineness 100 orders;

The second layer is above to be fast dried silicon melten gel+mullite powder, dope viscosity 3-13S, sand fineness 10-60 order;

Each order is counted sand and is screened out the use of caking back with screen pack, is coated with slip and stirs fully, evenly waits for quietly using behind the bubble floating;

2.3, be coated with and hang the system shell, on wax-pattern, be coated with fast dried silicon melten gel, lagging edge and back of the body arc part are particularly advanced in stucco, each stucco is wanted evenly, mould crust thickness 15-18mm;

2.4, air-dry

Whenever be coated with one deck, air-dry 2-24 hour, natural air drying;

2.5, dewaxing, dewaxing still fast dewaxing, steam dewaxing, vapor (steam) temperature 140-160 degree centigrade, pressure 4-5 atmospheric pressure, temperature retention time 10-12 minute are adopted in dewaxing;

2.6, high-temperature roasting

Carry out at roaster, be warmed up to 800-900 degree centigrade, be incubated and naturally cool to normal temperature after 2-3 hour;

Three, smelting and pouring

3.1, adopt intermediate frequency furnace that Austria's body stainless steel is smelted;

3.2, with the shell sandbox of packing into, the shell spacing should be greater than 150mm, with heat-insulating property preferably granularity be that the bauxite of φ 3--φ 5mm is as the back-up sand material, filling moulding, sandbox envelope ceramic paste material suitable for reading (7), shell and and sandbox roasting process temperature should remain on 850 degrees centigrade, temperature retention time was more than or equal to 30 minutes;

3.3, the casting

Tapping temperature should be in the time of 1600 degrees centigrade; During 1580 degrees centigrade of cast temperatures, casting rate 3 Kilograms Per Seconds; The time of unpacking was greater than 5 hours;

Adopt uphill casting, with the sandbox certain angle that tilts, make that molten steel is average to be flowed in the shell along lagging edge quietly, then sandbox is erected, shell is filled with, casting process will be finished at 5-8 second;

3.4, the foundry goods that waters, shake out time surrounded the shell of foundry goods and removes with vibrating method more than or equal to 12 hours, with cast gate and the excision of technology head, carried out blasting treatment, sprayed clean foundry goods and carried out 100% surface inspection, and casting flaw mustn't be arranged;

Four, heat treatment

The blade and the coupon of each heat lot are handled with stove, avoid the blade stacking distortion, and the blade of coming out of the stove will be put down gently, in order to avoid the distortion of colliding with; When blade is raised to 1040-1100 degree centigrade with furnace temperature in stove: wait to grill thoroughly back insulation 1 minute.