CN1141830A - Centrifugal steel-pipe casting method - Google Patents
Centrifugal steel-pipe casting method Download PDFInfo
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- CN1141830A CN1141830A CN 96106565 CN96106565A CN1141830A CN 1141830 A CN1141830 A CN 1141830A CN 96106565 CN96106565 CN 96106565 CN 96106565 A CN96106565 A CN 96106565A CN 1141830 A CN1141830 A CN 1141830A
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Abstract
The method for centrifugal casting steel pipe is mainly characterized by that its pouring rate is controlled at greater than or equal to 20 kg/s; a protecting agent is applied to internal wall in the course of pouring; rotating speed of mould barrel is increased in a certain regulation in 10s from starting of pouring, and after pouring, the rotating speed of the mould barrel is decreased in a certain regulation until the casting is fully solidified. Using said invention can control the equiaxed crystal rate of the product, and can obtain full-fine equiaxed crystal product, so that it can greatly raise the mechanical property of the casting.
Description
The invention belongs to the centrifugal casting field.Mainly be applicable to centrifugal casting steel tube, be specially adapted to the centrifugal casting of heat resisting pipe.
Usually, the metallic article of centrifugal casting, shape, the size of its mechanical property and crystal grain have confidential relation, have the goods of fine isometric crystal grains tissue, and it draws anti-intensity, yield strength and creep strength all to be higher than the goods of thick columnar grain tissue.For heat resisting steel, under common centrifugal casting condition, can only obtain the relatively advanced tissue of column crystal, and, even take heat treatment also can't change the thick state of original crystal grain.For this reason, how controlling grainiess and crystal grain thinning in centrifugal casting is the problem of studying for a long time.
The basic reason that produces thick columnar grain during centrifugal casting be since when cast liquid metal and the frozen metal layer while rotate at a high speed with type tube, be in relative static conditions between the two very soon, the unidirectional cooling grain growth by the type tube wall causes.If can import external force, force not solidified liquid metal convection current, the dendrite of solidification front is fractureed, come off and just can impel equiax crystal to form.Therefore, the key of crystal grain thinning just is to destroy this static relatively state.
In the prior art, the someone has proposed employing electromagnetic field centrifugal casting method refinement goods crystal grain.The essence of this method is to make molten steel centrifugal rotation in electromagnetic field, by the effect of electromagnetic agitation, suppresses growing up of column crystals thereby the dendrite of solidification front is fractureed and form many nucleus, impels the growth of equiax crystal, crystal grain thinning.But there is following shortcoming in this method: investment is big, and power consumption is big, and the cost height in addition, also need be equipped with nonmagnetic thin-walled casting mold etc.Therefore, this method still is difficult to practicality at present, particularly for large-diameter pipe, long tube and thick-walled pipe, and more difficult (" Acta Metallurgica Sinica " 1993, the 29th volume, the 3rd phase; " (casting " 1994, the 10th phase).
In the prior art, adopt the method for periodically-varied type tube rotating speed to come refinement goods crystal grain in addition, (acceleration is 0.8～1.6rpm/s but this method type tube rotation speed change speed is little
2), transformation period short (4～7S) because the inertia of molten metal height, can not obtain the effect (" the tenth international vacuum proceeding " 1989, P334～340 page) of significant crystal grain thinning.
The object of the present invention is to provide a kind of utilization to have centrifugal casting equipment now, can control degree of grain refinement within the specific limits, and the method for economic, easy centrifugal casting steel tube.
At above-mentioned purpose, the present invention is a solidified structure of controlling centrifugal casting steel tube by the method for destroying relative static conditions between liquid metal and the type tube, promptly under the preceding topic of quick cast, unidirectional solidification, under solid-liquid two-phase metal coexisting state, continuously change the rotating speed of type tube with certain rules, the tangential force of utilizing the acceleration in the rotary speed change process that the crystallization forward position is produced, force not frozen metal convection current, thereby suppress the growth of column crystal, impel equiax crystal forming core, grow up, reach the purpose of crystal grain thinning.Its concrete technical application scheme is as follows.
The present invention can go up at general centrifugal casting equipment (as horizontal support roller formula centrifugal casting machine) and implement, at first choose type tube according to the specification of the steel pipe of need centrifugal casting, hang up properly coating according to a conventional method, the steel clock material that to pour into a mould simultaneously melts in smelting furnace, when the steel fusing finishes and reaches pouring temperature, begin cast, control casting process by following parameter during cast:
1, control poring rate 〉=20Kg/S.
2, the inwall to liquid metal applies protective agent in casting process.
3, from beginning to be poured into arbitrary moment in 10 seconds, implement promptly to increase continuously the type tube rotating speed, the acceleration of type tube rotation is 10～25rpm/s
2, finish until cast.
4, after cast finishes, reducing the type tube rotating speed immediately continuously, the acceleration of type tube rotation is-0.3～-2.0rpm/s
2, solidify fully until foundry goods.
Adopt centrifugal casting steel tube of the present invention, when pipe thickness 〉=8mm, grain refinement the best.
Now illustrate as follows with regard to above-mentioned technological measure or parameter:
Requiring poring rate 〉=20Kg/S, is in order to finish casting process as early as possible, to prevent that the liquid steel temperature cooling is too fast, so that keep enough thick non-solidification layer.In addition, can avoid producing the bigger temperature difference between hot junction (cup end) and the cold junction, thus the difference of dwindling cold and hot end crystal grain thinning.
Apply protective agent to the liquid metal inwall in the casting process; except the inner surface quality that can improve cast tube, also inwall is played insulation effect, to form the consecutive solidification of molten steel from the outer wall to the inwall; and delayed the time that molten steel is in non-curdled appearance, help more molten metal by refinement.The protective agent that is applied can adopt various existing centrifugal casting protective agents to get final product.
From beginning to be poured into arbitrary moment in 10 seconds, implementing promptly increases the type tube rotary speed continuously, and its acceleration is 10～25rpm/s
2, its role is to make between metal freezing layer and the non-solidification layer be in the relative motion state all the time, thus the growth of inhibition column crystal, so that generate equi-axed crystal.When above-mentioned acceleration less than 10rpm/s
2The time, because dynamics is not enough, grain refinement effect is not remarkable; And work as acceleration greater than 25rpm/s
2The time, intercrystalline is easily produced micro-crack, reduces the service life of product, so during cast the acceleration of type tube with 10～25rpm/s
2Be advisable.
In addition, control increases the time that rotary speed begins, and can control equiaxial crystal ratio, satisfies different use needs.That is to say that from the beginning cast just increases rotary speed immediately, than beginning to pour into a mould the goods equiaxial crystal ratio height that just begins to increase rotary speed after the several seconds.Because high-temperature molten metal one enters type tube, solidify and just begin to carry out, increase rotary speed and begin more early, the molten metal of convection current is just many more, and refinement layer is just thick more.Otherwise the molten metal of pressing close to type tube will solidify earlier, grow up, and forms certain thickness column crystal layer, surpasses just to begin to change rotating speed 10 seconds, because the molten metal that does not coagulate does not reach the refinement purpose very little.
Cast finishes, and reduces the type tube rotating speed immediately, solidifies fully until foundry goods.Its effect also is to make to keep the relative motion state between frozen metal and the non-frozen metal.If it is too fast that the type tube rotating speed reduces, the phenomenon of being scattered may appear in the molten metal of ot-yet-hardened; If it is slow that the type tube rotating speed reduced, then the grain refining effect of ot-yet-hardened layer is not remarkable.For light-wall pipe, can select the bigger acceleration of absolute value certainly, can select the less acceleration of absolute value for the pipe of wall thickness.Facts have proved, cast finish the rotary acceleration of back type tube with-0.3～-2.0rpm/s
2Be advisable.
In above-mentioned change type tube rotary speed process, the acceleration absolute value of selection is tending towards the upper limit, and acceleration is implemented more early, and grain refinement is remarkable more through degree; Opposite it is late more to come into effect acceleration, then will obtain part column crystal layer if be tending towards lower limit, and equiaxial crystal ratio descends.
For the present invention, can select the acceleration of suitable type tube rotation and the time that comes into effect acceleration, so that obtain best effect according to the specification and the purposes of foundry goods goods.
The present invention is applicable to the steel pipe of various wall thickness, but better to the steel pipe effect of wall thickness 〉=8mm.
Adopt centrifugal casting steel tube of the present invention,, both can obtain the spun cast pipe goods of 100% equiaxial crystal ratio, also can obtain the spun cast pipe goods of any ratio equiaxial crystal ratio, promptly can control equiaxial crystal ratio by controlling above-mentioned cast parameter.
Compared with prior art, the present invention has following advantage:
(1), method is simple, only needs just can realize with the rotary speed that certain rules changes type tube the grain refinement of spun cast pipe goods, the goods of acquisition certain proportion equiaxial crystal ratio.
(2), cost is low, can adopt original centrifugal casting equipment, need not newly added equipment, just can improve the cast tube quality.
(3), can control equiaxial crystal ratio according to customer requirements.
Embodiment
Adopt method of the present invention, on the centrifugal casting machine of horizontal support roller formula, centrifugal casting three groups of totally 5 batches of steel pipes, the steel grade that each group is poured into a mould is consistent with the cast tube specification.In order to contrast, in each group on same equipment, with existing common centre spinning method, the also cast tube of a collection of same steel grade of centrifugal casting and same specification.Table 1 has been enumerated the steel grade and the specification of three groups of 5 crowdes of the present invention and the centrifugal casting of three batches of Comparative Examples institutes.Each batch and the centrifugal casting parameter that Comparative Examples adopted are as shown in table 2.After the demoulding, take a sample from goods, carry out metal lographic examination, observe metallographic structure, measure equiaxial crystal ratio, result of the test is as shown in table 3.
Accompanying drawing 1～8 respectively is the metallograph of embodiment lot number 1,2 and Comparative Examples 1, embodiment lot number 3,4 and Comparative Examples 2, embodiment lot number 5 and Comparative Examples 3.
As can be seen from the results, adopt the inventive method can control the degree of goods grain refinement, namely can obtain the cast tube that whole equiax crystal or equiax crystal account for certain ratio, to satisfy different application target needs.
The cast tube goods that adopt common centre spinning method to pour into a mould, its metallographic structure is essentially thick column crystal.
The steel grade of table 1 embodiment of the invention and Comparative Examples cast tube and specification
Annotate: φ
1Be cast tube external diameter, φ
2Be the cast tube internal diameter, L is a cast tube length.
| The project lot number | Centrifugal casting apparatus | Centrifugal casting steel clock | The cast tube specification | ||
| First group | The present invention | ??1 | The centrifugal casting machine of horizontal support roller formula | ??4Cr28Ni15 | ??φ 1325×φ 2265×L2550 |
| ??2 | The centrifugal casting machine of horizontal support roller formula | ??4Cr28Ni15 | ??φ 1325×φ 2265×L2550 | ||
| Comparative Examples 1 | The centrifugal casting machine of horizontal support roller formula | ??4Cr28Ni15 | ??φ 1325×φ 2265×L2550 | ||
| Second group | The present invention | ??3 | The centrifugal casting machine of horizontal support roller formula | ??3Cr24Ni7N | ??φ 1339×φ 2279×L2500 |
| ??4 | The centrifugal casting machine of horizontal support roller formula | ??3Cr24Ni7N | ??φ 1339×φ 2279×L2500 | ||
| Comparative Examples 2 | The centrifugal casting machine of horizontal support roller formula | ??3Cr24Ni7N | ??φ 1339×φ 2279×L2500 | ||
| The 3rd group | The present invention | ??5 | The centrifugal casting machine of horizontal support roller formula | ??4Cr25Ni20 | ??φ 1100×φ 276×L2500 |
| Comparative Examples 3 | The centrifugal casting machine of horizontal support roller formula | ??4Cr25Ni20 | ??φ 1100×φ 276×L2500 | ||
The centrifugal casting parameter of table 2 embodiment of the invention and Comparative Examples cast tube
| Lot number | Cast | Increase the type tube rotating speed | Reduce the type tube rotating speed | Apply the protective agent situation | |||||
| Total time S | Speed Kg/S | Quicken time started S | Acceleration time S | Acceleration rpm/s 2 | Deceleration time S | Acceleration rpm/s 2 | |||
| The present invention | ??1 | ????13 | ????43 | Open and water after-acceleration in 5 seconds | ????8 | ????17 | ??306 | ??-0.83 | Add |
| ??2 | ????8 | ????70 | Open and quicken immediately after watering | ????8 | ????21 | ??240 | ??-1.1 | Add | |
| Comparative Examples 1 | ????28 | ????20 | In whole cast and the process of setting, type tube rotating speed no change | Do not add | |||||
| The present invention | ??3 | ????15 | ????38 | Open and water after-acceleration in 8 seconds | ????7 | ????14 | ??300 | ??-0.76 | Add |
| ??4 | ????10 | ????58 | Open and quicken immediately after watering | ????10 | ????13 | ??280 | ??-0.82 | Add | |
| Comparative Examples 2 | ????30 | ????19 | In whole cast and the process of setting, type tube rotating speed no change | Do not add | |||||
| The present invention | ??5 | ????3 | ????23 | Open water after after-acceleration immediately | ????5 | ????24 | ??120 | ??-1.8 | Add |
| Comparative Examples 3 | ????6 | ????11 | In whole cast and the process of setting, type tube rotating speed no change | Do not add | |||||
The metallographic structure of table 3 embodiment of the invention and Comparative Examples cast tube
| Lot number | Grainiess | Equiaxial crystal ratio % | Degree of grain refinement | The corresponding accompanying drawing of metallographic structure photo institute | |
| The present invention | ?1 | The column crystal layer account for 1/6 all the other for equiax crystal | ??84 | The part refinement | Fig. 1 |
| ?2 | Whole equiax crystal | ??100 | All refinements | Fig. 2 | |
| Comparative Examples 1 | The column crystal layer account for 3/4 all the other for equiax crystal | ??25 | Thick | Fig. 3 | |
| The present invention | ?3 | The column crystal layer account for 2/3 all the other for equiax crystal | ??33 | The part refinement | Fig. 4 |
| ?4 | Column crystal appears in the part, and all the other are equiax crystal | ??100 | All refinements | Fig. 5 | |
| Comparative Examples 2 | Whole column crystals | ??0 | Thick | Fig. 6 | |
| The present invention | ?5 | The column crystal layer account for 1/7 all the other for equiax crystal | ??86 | Basic refinement | Fig. 7 |
| Comparative Examples 3 | Column crystal accounts for 5/6, and all the other are equiax crystal | ??16 | Thick | Fig. 8 | |
Claims (2)
1, a kind of method of centrifugal casting steel tube adopts conventional centrifugal casting equipment, it is characterized in that:
(1), pouring molten steel speed 〉=20Kg/S;
(2), in casting process, apply protective agent to the liquid metal inwall;
(3), from beginning to be poured into arbitrary moment in 10 seconds, implement promptly to increase continuously the type tube rotating speed, the acceleration of type tube rotation is 10～25rpm/S
2, finish until cast;
(4), after cast finishes, reduce the type tube rotating speed immediately continuously, the acceleration of type tube rotation be-0.3～-2.0rpm/s
2, solidify fully until foundry goods.
2, method according to claim 1 is characterized in that the thickness of steel pipe 〉=8mm that is cast.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 96106565 CN1141830A (en) | 1996-06-25 | 1996-06-25 | Centrifugal steel-pipe casting method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 96106565 CN1141830A (en) | 1996-06-25 | 1996-06-25 | Centrifugal steel-pipe casting method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1141830A true CN1141830A (en) | 1997-02-05 |
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ID=5119273
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 96106565 Pending CN1141830A (en) | 1996-06-25 | 1996-06-25 | Centrifugal steel-pipe casting method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1093013C (en) * | 2000-03-17 | 2002-10-23 | 刘振凤 | Centrifugal pouring method of steel tube |
| CN101817067A (en) * | 2010-05-06 | 2010-09-01 | 四川三洲川化机核能设备制造有限公司 | Method for producing seamless stainless steel tube by centrifugally pouring hollow billet |
-
1996
- 1996-06-25 CN CN 96106565 patent/CN1141830A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1093013C (en) * | 2000-03-17 | 2002-10-23 | 刘振凤 | Centrifugal pouring method of steel tube |
| CN101817067A (en) * | 2010-05-06 | 2010-09-01 | 四川三洲川化机核能设备制造有限公司 | Method for producing seamless stainless steel tube by centrifugally pouring hollow billet |
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