CN102211179A - High-temperature shakeout process applied to large-size martensitic stainless steel cast - Google Patents
High-temperature shakeout process applied to large-size martensitic stainless steel cast Download PDFInfo
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- CN102211179A CN102211179A CN2010101428827A CN201010142882A CN102211179A CN 102211179 A CN102211179 A CN 102211179A CN 2010101428827 A CN2010101428827 A CN 2010101428827A CN 201010142882 A CN201010142882 A CN 201010142882A CN 102211179 A CN102211179 A CN 102211179A
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Abstract
The invention relates to the field of casting processes of martensitic casts, in particular to a high-temperature shakeout process for a large-size martensitic stainless steel cast. The high-temperature shakeout process particularly comprises the following steps of: (1) selecting an area with highest cooling speed in the cast, wherein the time of temperature reduced to be higher than a start point of the martensitic phase transformation of a material by 50-100 DEG C is a reasonable shakeout time point; and (2) after the cast is shaken out, controlling the cooling speed of all parts of the cast to be basically equivalent to the cooling speed of the parts of the cast in a sand box by adopting a method for charging a furnace and cooling with the furnace or covering a heat-preserving material and the like. According to the high-temperature shakeout process disclosed by the invention, the sand box occupying time of the cast is shortened by reasonably selecting a shakeout temperature control point and optimally controlling the cooling conditions of the cast after the cast is shaken out, and therefore, production efficiency is enhanced and the internal stress of the cast is ensured to be controlled at a reasonable level without generating the phenomena of overstress, cracking, and the like. The invention can solve the problems of production efficiency reduction, production capacity limiting, and the like of an integral casting factory, which are caused by keeping the temperature of the cast in the sand box for a long time, in the prior art.
Description
Technical field
The present invention relates to martensite cast casting technology field, particularly a kind of hot shake-out technology that is applied to large-scale martensitic stain less steel foundry goods.
Background technology
Along with the development of economic society, increasing large-scale martensitic stain less steel foundry goods is designed, manufactured and uses.Large-scale water turbine foundry goods (comprising crown, following ring and blade three class foundry goods) with the use of large hydropower stations such as Three Gorges is typical case's representative, and wherein crown, following ring diameter reach more than 10 meters, and the pour steel amount can reach more than 200 tons and 100 tons.The type foundry goods is huge, and is often big more than several times than middle-size and small-size foundry goods after thermal stress that each several part produces in the casting process and structural stress add up; When being cooled to room temperature owing to the martensitic stain less steel foundry goods from casting high temperature simultaneously, except that the phase transformation of lower temperature generation martensite, other type phase transformation not taking place, because the casting stress that cooling is shunk and the martensitic phase variable expansion causes is very big.The existence of these stress can cause the foundry goods gross distortion even crackle occur, therefore under traditional processing technology, often take in the large-scale martensite steel-casting casting process foundry goods be incubated in sandbox to whole foundry goods martensite phase transformation end and just begin the knockout shake out, to reduce stress and distortion.
Though large-scale martensitic stain less steel foundry goods is incubated in sandbox to the technology of the knockout shake out of beginning below the material martensite phase transformation end point effectively alleviated the stress accumulation in the foundry goods, but this technology can cause the time of foundry goods in sandbox obviously to prolong, with the following ring foundry goods in the rotary wheel of water turbine of Three Gorges is example, often need be incubated more than one month in sandbox.The long-time insulation of foundry goods in sandbox taken relative stations and Casting Equipment, makes the production efficiency of whole casting factory descend, and production capacity is restricted, and enterprise's production cost is significantly improved, and also do not meet the energy-saving and cost-reducing requirement of country.
Summary of the invention
The object of the present invention is to provide a kind of hot shake-out technology that is applied to large-scale martensitic stain less steel foundry goods, solve the long-time insulation of foundry goods in sandbox that exists in the prior art and taken relative stations and Casting Equipment, make the production efficiency of whole casting factory descend, problems such as production capacity is restricted, this technology makes the foundry goods hot shake-out become possibility, improve castings production efficient, alleviate the stress level in the foundry goods simultaneously, reduce the distortion and the tearing tendency of foundry goods, realize the efficient and high-quality unification of castings production.
Among the present invention, large-scale martensitic stain less steel foundry goods is meant that castings material is a martensitic stain less steel, and the foundry goods gross weight easily produces the foundry goods of big casting stress more than 5 tons in the casting process.For example: foundry goods such as the crown in the common large-scale water turbine runner, following ring and blade.
Technical scheme of the present invention is:
(1) simulation means that uses a computer calculates the temperature field and the stress-strain field of large-scale martensitic stain less steel foundry goods cooling procedure in sandbox;
Based on technology behind casting temperature field and stress field calculating reasonable shakeout temperature of selection and the shake out, realize reducing large-scale martensite steel-casting and take sandbox and station time, enhance productivity.
(2) choose the fastest zone of cooling velocity in the foundry goods, this regional temperature reduces to that to be higher than 50～100 ℃ of moment of material martensite phase transformation starting point be reasonable shake out time point;
(3) to take shove charge suitable substantially with its cooling velocity in sandbox behind the foundry goods shake out with method control foundry goods each several part cooling velocities such as stove cooling or covering insulation materials;
(4) foundry goods shake out speed is rapid as far as possible.
The mechanism of hot shake-out technology that the present invention is applied to large-scale martensitic stain less steel foundry goods is as follows:
Molten metal is shunk gradually by high temperature volume when the sub-cooled, because that foundry goods each several part cooling velocity difference causes shrinking is asynchronous, produces stress and strain owing to the interaction of each several part and the obstruction of outside casting mold simultaneously.At martensite steel, molten steel cools down from high temperature the process, is in continuous contraction state always, begins until the martensitic phase height, and just owing to the martensite phase transformation takes place expand, partial offset shrinks the stress of generation to material.As shown in Figure 1, thermal expansion curve when martensite steel is cooled to low temperature by high temperature as can be seen, material was in contraction state always before being cooled to Ms point (martensite phase transformation starting point), with respect to other steel grade that pearlite or bainitic transformation take place in the cooling procedure, martensite steel amount of contraction in cooling procedure is bigger, can cause big stress thus.Shrink and the bigger state of amount of contraction in the last dullness that directly is in of martensite phase transformation just because of martensite steel, so the stress of foundry goods each several part before the martensite phase transformation takes place constantly adds up.
At above analysis as can be seen, the maximum stress of martensite steel foundry goods often appears at its martensite phase transformation starting point eve, because the accumulation amount of contraction that this moment should the zone reaches maximum.Bigger expansion takes place in martensite phase transformation meeting subsequently, and offsets part stress.If therefore the hot shake-out temperature of martensite steel is chosen in the foundry goods generation martensitic transformation temperature interval, this moment, the martensite phase transformation partly took place in foundry goods, form intensity and the higher martensitic structure of hardness, compatible deformation ability between the foundry goods each several part, can cause martensite transformation stress and shake out stress to add up, easily cause the foundry goods cracking; If shakeout temperature can not realize the purpose that the castings production cycle is shortened after being chosen in foundry goods martensite phase transformation end; Before the martensite phase transformation in slow zone begins if shakeout temperature is chosen in foundry goods cooling, this moment, whole casting temperature was higher, because foundry goods lacks the restriction and the insulation effect of sandbox behind the shake out, can in the shake out process, produce temperature drop faster, thereby strengthen the temperature difference at foundry goods thickness place, and then cause big stress.
If shakeout temperature is set in the fastest zone of foundry goods cooling rate and is cooled to the martensitic phase height and begins preceding 50～100 ℃, the martensite phase transformation does not take place in other zone of foundry goods on the one hand, plastic deformation ability is stronger, and the shake out process can be fallen stress release by compatible deformation; This moment, the foundry goods bulk temperature was lower on the other hand, can not produce very fast temperature drop in the shake out process, the temperature difference between the foundry goods each several part can not increase, and then can not cause than big thermal (temperature difference) stress, simultaneously constantly during shake out in the foundry goods integrated stress little, shake out stress can not produce accumulative action with the internal stress of foundry goods own; 50～100 ℃ temperature nargin can guarantee that the martensite phase transformation does not take place at foundry goods cooling rate very fast position more than the martensitic phase height in the shake out process in addition, avoids external force and transformation stress stack in the shake out process.
When foundry goods after knockout finishes in the rational temperature interval, take shove charge suitable substantially with its cooling velocity in sandbox with method control foundry goods each several part cooling velocities such as stove cooling or covering insulation materials, can effectively reduce because of foundry goods is exposed under the normal air cooling environment and cause the each several part temperature difference, and then prevent that the defective of thermal (temperature difference) stress and distortion from taking place.Therefore, adopt that the present invention proposes be chilled to more than the martensite phase transformation starting point 50～100 ℃ in the fastest zone of foundry goods cooling velocity the time begin shake out, the shake out process as far as possible rapidly, to reduce the direct temperature difference of shake out process medium casting each several part, behind the shake out foundry goods is carried out the temperature control cooling simultaneously, can realize carrying out smoothly foundry goods safety hot shake-out technology.
The present invention has following beneficial effect:
1. the hot shake-out technology that is applied to large-scale martensitic stain less steel foundry goods that proposes of the present invention, can effectively improve the production efficiency of large-scale martensite steel-casting, with Three Gorges large-scale water turbine runner down the ring foundry goods be that example can effectively less its temperature retention time 59% in sandbox;
2. the hot shake-out temperature system of selection of the present invention's proposition can be widely used in the martensite steel-casting, and simple to operate.Simultaneously,, can realize cooling off and the merging of martensite steel foundry goods softening annealing process behind the shake out, further reduce the production cycle, reduce cost if carry out the temperature control cooling with putting into stove behind the foundry goods shake out;
3. the hot shake-out process of the present invention's use is fit to actual industrial production, is easy to obtain works approval, and is applied in part producer, improves the production efficiency of large-scale martensite steel-casting greatly.
Description of drawings
Fig. 1 martensite steel cooling procedure thermal expansion curve.
Fig. 2 Three Gorges 700MW level rotary wheel of water turbine ring is down poured into a mould the sectional view and the representative points present position schematic diagram of Temperature Distribution when finishing.
Fig. 3 is ring mid point 1,2 two temperature of point and the equivalent stress of putting 1 place curve over time down.
The following ring shake out Temperature Distribution constantly that Fig. 4 sets by the inventive method.
The following ring shake out equivalent stress distribution constantly that Fig. 5 sets by the inventive method.
Fig. 6 (a) encircles the equivalent stress distribution when being cooled to 100 ℃ in sandbox down.
Equivalent stress distribution when stove is chilled to 100 ℃ behind 370 ℃ of shake outs of ring under Fig. 6 (b).
The specific embodiment
Present embodiment is an example with ring casting process under the 700MW level of Three Gorges, and the material of following ring is the ZG06Cr13Ni4Mo martensitic stain less steel, and the hot shake-out technology that is applied to large-scale martensitic stain less steel foundry goods is as follows:
(1) uses conventional computer simulation means, calculate the temperature field and the stress-strain field of large-scale martensitic stain less steel foundry goods cooling procedure in sandbox;
In the present embodiment, the detailed process of calculating large-scale martensitic stain less steel foundry goods temperature field of cooling procedure in sandbox is as follows: the temperature field of encircling in casting process is down calculated the initial value that calculate as casting solidification process temperature field in the temperature field when at first extracting ring cast end down based on Procast casting Finite Element Simulation Software; The interface heat exchange coefficient (this coefficient is obtained by the inverse operation then of actual measurement temperature) between foundry goods and sand mold and the warming plate etc. and the thermal physical property parameter (being obtained by actual measurement) of martensitic stain less steel rationally are set; Use finite element analysis method that calculating is found the solution in the temperature field of whole foundry goods, and result of calculation is carried out post processing, write down the temperature variation curve of each computing node and the variations in temperature cloud atlas of whole foundry goods.
In the present embodiment, the detailed process of calculating large-scale martensitic stain less steel foundry goods stress-strain field of cooling procedure in sandbox is as follows: at first the stress-strain diagram under this martensitic stain less steel different temperatures is measured and analyzed, and relevant parameter is imported Procast software; At different this structure simulation model of the material selection under the different temperatures; Use Procast software to find the solution, calculate at each and go on foot the temperature of at first calculating each node place, then calculate the stress value at this some place, and calculate the strain value at this some place according to selected constitutive model; Result of calculation is carried out post processing, calculate the equivalent stress at each point place, equivalent strain and each principal stress and shearing stress, and record each point stress-strain state.
(2) choose suitable shake out time point according to temperature field result of calculation
With ring casting process under the 700MW level of Three Gorges is example, Figure 2 shows that down the sectional view of Temperature Distribution when the ring cast finishes, choose down two key points encircling in the casting process according to following ring structure analysis and calculating: it is the fastest that point 1 (point1) locates cooling velocity, and it is the slowest that point 2 (point2) locate cooling velocity.
Fig. 3 has write down and has put 1,2 two temperature of point and the equivalent stress of putting 1 place over time, as can be seen, the stress of putting 1 place increases gradually along with the carrying out of cooling, and left and right sides stress reaches maximum behind the cooling 400h, after keeping a period of time, descend along with the reduction of temperature.When point 1 stress value reached maximum, its corresponding temperature was about 300 ℃, just is in the martensite phase transformation starting point of this material.Then along with temperature continues to descend, the part shrinkage stress is offset in the martensitic phase variable expansion, impels this some place stress value to descend.
According to principle of the present invention, the moment that the temperature at selected element 1 place is reduced to 370 ℃ (present embodiment is for being higher than 70 ℃ of this material martensitic phase heights) is reasonable shake out time point.The Temperature Distribution cloud atlas that Fig. 4 encircles for this reason at present, the temperature at this time point 1 place is lower than a little 2 temperature as can be seen, and the temperature of putting 2 places is about about 420 ℃.Equivalent stress distribution cloud atlas during Fig. 5 encircles for this reason at present, putting 1 zone of living in as can be seen has certain stress to have about 330MPa; And put 2 zones of living in because temperature is higher, the contraction cumulant is less and have plastic deformation ability preferably, so stress herein is very little, has only tens MPas.Therefore select this time point shake out, foundry goods internal stress value is less, and foundry goods is comparatively safe.
(3) rational shake out aftertreatment technology is set
When foundry goods after knockout finishes in the rational temperature interval, take shove charge suitable substantially with its cooling velocity in sandbox with methods such as stove cooling or covering insulation material (present embodiment be pack into temperature be in 370 ℃ the stove) control foundry goods each several part cooling velocity with the stove cooling, can effectively reduce because of foundry goods is exposed under the normal air cooling environment and cause the each several part temperature difference, and then prevent that the defective of thermal (temperature difference) stress and distortion from taking place.
Fig. 6 (a) and (b) be respectively down the ring foundry goods and in sandbox, be cooled to 00 ℃ and the equivalent stress distribution figure when down ring cools to 100 ℃ with the furnace behind 370 ℃ of shake outs.With respect to the low temperature shake out, the hot shake-out technology of cooling off with stove behind 370 ℃ of shake outs is through the cold situation that can make final casting internal stress value be lower than the low temperature shake out of control stove subsequently as can be seen.
This shake out technology can effectively shorten foundry goods, and to take founder's bit time about 59%, also can obviously not increase internal stress and distortion in the foundry goods simultaneously, can obviously improve the production efficiency of foundry goods.
Claims (3)
1. hot shake-out technology that is applied to large-scale martensitic stain less steel foundry goods, it is characterized in that, temperature field and stress-strain field according to large-scale martensitic stain less steel foundry goods cooling procedure in sandbox, choose the fastest zone of cooling velocity in the foundry goods, this regional temperature reduces to that to be higher than 50～100 ℃ of moment of material martensite phase transformation starting point be reasonable shake out time point.
2. according to the described hot shake-out technology that is applied to large-scale martensitic stain less steel foundry goods of claim 1, it is characterized in that, to take shove charge with stove cooling or covering insulation material method control foundry goods each several part cooling velocity behind the foundry goods shake out, make it suitable with its cooling velocity in sandbox.
3. according to the described hot shake-out technology that is applied to large-scale martensitic stain less steel foundry goods of claim 1, it is characterized in that, calculate technology behind selection shakeout temperature and the shake out based on casting temperature field and stress field.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102921932A (en) * | 2012-11-21 | 2013-02-13 | 宁夏共享集团有限责任公司 | High-temperature shakeout process method of large-scale Bainite steel casting |
| CN103128268A (en) * | 2013-01-17 | 2013-06-05 | 中国科学院金属研究所 | Method used for medium and low temperature mold dismantling of large-scale extra-thick plate blank |
| CN104874775A (en) * | 2015-04-23 | 2015-09-02 | 共享铸钢有限公司 | Rapid cleaning method for large martensitic stainless steel castings |
| CN109014148A (en) * | 2018-08-16 | 2018-12-18 | 共享铸钢有限公司 | A kind of hot shake-out method of two-phase stainless steel large-sized steel-casting |
| CN110039003A (en) * | 2019-05-30 | 2019-07-23 | 安徽应流集团霍山铸造有限公司 | A kind of manufacturing method of large size martensitic stain less steel casting |
| CN112045170A (en) * | 2020-08-26 | 2020-12-08 | 共享铸钢有限公司 | Method for preventing large steel casting from cracking |
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| CN1597180A (en) * | 2004-08-02 | 2005-03-23 | 中国科学院金属研究所 | Integral easting method of cast steel supporting roller |
| CN101185966A (en) * | 2007-12-25 | 2008-05-28 | 二重集团（德阳）重型装备股份有限公司 | Large-scale steel casting production technology and slowly cooling device thereof |
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| US4895605A (en) * | 1988-08-19 | 1990-01-23 | Algoma Steel Corporation | Method for the manufacture of hardened railroad rails |
| CN1212189A (en) * | 1997-05-29 | 1999-03-31 | 于西纳公司 | Process for manufacturing thin strip of ferritic stainless steel, and thin strip thus obtained |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102921932A (en) * | 2012-11-21 | 2013-02-13 | 宁夏共享集团有限责任公司 | High-temperature shakeout process method of large-scale Bainite steel casting |
| CN103128268A (en) * | 2013-01-17 | 2013-06-05 | 中国科学院金属研究所 | Method used for medium and low temperature mold dismantling of large-scale extra-thick plate blank |
| CN104874775A (en) * | 2015-04-23 | 2015-09-02 | 共享铸钢有限公司 | Rapid cleaning method for large martensitic stainless steel castings |
| CN109014148A (en) * | 2018-08-16 | 2018-12-18 | 共享铸钢有限公司 | A kind of hot shake-out method of two-phase stainless steel large-sized steel-casting |
| CN110039003A (en) * | 2019-05-30 | 2019-07-23 | 安徽应流集团霍山铸造有限公司 | A kind of manufacturing method of large size martensitic stain less steel casting |
| 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 |
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