CN102211179B - 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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- CN102211179B CN102211179B CN 201010142882 CN201010142882A CN102211179B CN 102211179 B CN102211179 B CN 102211179B CN 201010142882 CN201010142882 CN 201010142882 CN 201010142882 A CN201010142882 A CN 201010142882A CN 102211179 B CN102211179 B CN 102211179B
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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 technique 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.As Typical Representative, wherein crown, lower ring diameter reach more than 10 meters the large-scale water turbine foundry goods (comprising crown, lower ring and blade three class foundry goods) that uses with large hydropower stations such as Three Gorges, and the pour steel amount can reach more than 200 tons and 100 tons.The type foundry goods is huge, and is often large more than several times than middle-size and small-size foundry goods after the thermal stress that each several part produces in the casting process and structural stress are cumulative; Simultaneously since the martensitic stain less steel foundry goods from the casting High-temperature cooling during to room temperature, except the phase transformation of lower temperature generation martensite, other type phase transformation not occuring, because the casting stress that cooling is shunk and the martensitic phase variable expansion causes is very large.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 casting steel 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.
Although large-scale martensitic stain less steel foundry goods is incubated in sandbox to the technique 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 technique can cause the time of foundry goods in sandbox obviously to prolong, lower ring foundry goods in the Hydraulic Turbine Runner of Three Gorges often need to be incubated more than one month in sandbox as example.The long-time insulation of foundry goods in sandbox taken relative stations and Casting Equipment, so that the production efficiency of whole casting factory descends, production capacity is restricted, and enterprise's production cost is significantly improved, and also do not meet the requirement of national energy-saving consumption reduction.
Summary of the invention
The object of the present invention is to provide a kind of hot shake-out technique 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, so that the production efficiency of whole casting factory descends, the problems such as production capacity is restricted, this technique makes the foundry goods hot shake-out become possibility, improve castings production efficient, alleviate simultaneously the stress level in the foundry goods, reduce 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 refers to that castings material is martensitic stain less steel, and the foundry goods gross weight easily produces the foundry goods of larger casting stress more than 5 tons in the casting process.Such as: the foundry goods such as the crown in the common large-scale water turbine runner, lower ring and blade.
Technical scheme of the present invention is:
(1) use the computer simulation means to calculate temperature field and the stress-strain field of large-scale martensitic stain less steel foundry goods cooling procedure in sandbox;
Select technique behind reasonable shakeout temperature and the shake out based on casting temperature field and stress field calculation, 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 is down 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 substantially suitable with its cooling velocity in sandbox with method control foundry goods each several part cooling velocities such as stove cooling or covering insulation materials behind the foundry goods shake out;
(4) foundry goods shake out speed is rapid as far as possible.
The mechanism of hot shake-out technique that the present invention is applied to large-scale martensitic stain less steel foundry goods is as follows:
Molten metal by high temperature during to sub-cooled volume shrink gradually because that foundry goods each several part cooling velocity difference causes shrinking is asynchronous, produce stress and strain owing to the interaction of each several part and the obstruction of outside casting mold simultaneously.For martensite steel, molten steel gets off from High-temperature cooling the process, is in continuous contraction state always, until the martensitic phase height begins, just owing to the martensite phase transformation occuring expand, partial offset shrinks the stress of generation to material.As shown in Figure 1, thermal expansion curve during to low temperature can be found out by High-temperature cooling from martensite steel, 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 occur in the cooling procedure, martensite steel amount of contraction in cooling procedure is larger, can cause larger stress thus.Shrink and the larger 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 occurs is constantly cumulative.
Can find out for above analysis, 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.Larger expansion occurs 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 occured 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 cumulative, 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 restriction and the insulation effect of sandbox behind the shake out, can in the shake out process, produce faster temperature drop, thereby strengthen the temperature difference at foundry goods thickness place, and then cause larger 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 front 50～100 ℃, the martensite phase transformation does not occur 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 larger 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 occur 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.
After foundry goods knockout in rational temperature range is complete, take shove charge substantially suitable 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 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 occuring.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 the safe hot shake-out technique of foundry goods.
The present invention has following beneficial effect:
1. the hot shake-out technique that is applied to large-scale martensitic stain less steel foundry goods that proposes of the present invention, production efficiency that can the large-scale martensite steel-casting of Effective Raise can effectively less its temperature retention time 59% in sandbox as an example of Three Gorges large-scale water turbine runner lower ring foundry goods example;
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, if carry out the temperature control cooling with putting into stove behind the foundry goods shake out, 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;
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, greatly improves the production efficiency of large-scale martensite steel-casting.
Description of drawings
Fig. 1 martensite steel cooling procedure thermal expansion curve.
Sectional view and the representative points present position schematic diagram of Temperature Distribution when the ring cast finishes under the 700MW level rotary wheel of water turbine of Fig. 2 Three Gorges.
Ring mid point 1,2 two temperature of point and the equivalent stress of putting 1 place curve over time under Fig. 3.
The lower ring shake out Temperature Distribution constantly that Fig. 4 sets by the inventive method.
The lower ring shake out equivalent stress distribution constantly that Fig. 5 sets by the inventive method.
Equivalent stress distribution when the lower ring of Fig. 6 (a) is cooled to 100 ℃ in sandbox.
Equivalent stress distribution when stove is chilled to 100 ℃ behind 370 ℃ of shake outs of the lower ring of Fig. 6 (b).
The specific embodiment
The present embodiment encircles casting process as example under the 700MW level of Three Gorges, the material of lower ring is the ZG06Cr13Ni4Mo martensitic stain less steel, and the hot shake-out technique that is applied to large-scale martensitic stain less steel foundry goods is as follows:
(1) uses conventional computer simulation means, calculate 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: based on Procast casting Finite Element Simulation Software the temperature field of lower ring in casting process calculated, at first extract lower ring and pour into a mould the initial value that calculate as casting solidification process temperature field in the temperature field when finishing; Interface heat exchange coefficient (this coefficient is obtained by the then inverse operation 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 the method for finite element that calculating is found the solution in the temperature field of whole foundry goods, and result of calculation is carried out post processing, record 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 inputted Procast software; For 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 Nodes, 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 Calculated Results of Temperature Field
Under the 700MW level of Three Gorges, encircle casting process as example, Figure 2 shows that the sectional view of Temperature Distribution when lower ring cast finishes, choose two key points in the lower ring casting process according to lower ring structure analysis and calculation: 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 recorded and has put 1,2 two temperature of point and the equivalent stress of putting 1 place over time, can find out, 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 down to 370 ℃ (the 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 can find out that the temperature at this time point 1 place is lower than a little 2 temperature, puts the temperature at 2 places about about 420 ℃.Equivalent stress distribution cloud atlas during Fig. 5 encircles for this reason at present can find out that a little 1 zone of living in has certain stress to exist, approximately 330MPa; And put 2 zones of living in because temperature is higher, the contraction cumulant is less and have preferably plastic deformation ability, so stress herein is very little, only has 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
After foundry goods knockout in rational temperature range is complete, take shove charge substantially suitable with its cooling velocity in sandbox with the methods such as stove cooling or covering insulation material (the present embodiment be pack into temperature be with the stove cooling in 370 ℃ the stove) control foundry goods each several part cooling velocity, can effectively reduce because 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 occuring.
Fig. 6 (a) and (b) be respectively the equivalent stress distribution figure of lower ring foundry goods when in sandbox, being cooled to 00 ℃ and lower ring and behind 370 ℃ of shake outs, cooling to 100 ℃ with the furnace.Can find out with respect to the low temperature shake out, the hot shake-out technique 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.
This shake out technique can effectively shorten foundry goods and take founder's bit time approximately 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 technique that is applied to large-scale martensitic stain less steel foundry goods, it is characterized in that, use the computer simulation means to calculate temperature field and the stress-strain field of 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 is down 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 hot shake-out technique that is applied to large-scale martensitic stain less steel foundry goods claimed in 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 hot shake-out technique that is applied to large-scale martensitic stain less steel foundry goods claimed in claim 1, it is characterized in that, calculate technique behind selection shakeout temperature and the shake out based on casting temperature field and stress-strain field.
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Families Citing this family (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 |
| CN103128268B (en) * | 2013-01-17 | 2015-10-14 | 中国科学院金属研究所 | For the method for low temperature shake out in large extra thick plate blank |
| CN104874775B (en) * | 2015-04-23 | 2017-01-04 | 共享铸钢有限公司 | A kind of quick method for cleaning of large-scale martensitic stain less steel foundry goods |
| 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 |
| 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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| 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 |
| 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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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| 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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