Steel pipe fixing and casting method for cast-in slender steel pipe castings

Abstract

A method for fixing and casting a steel pipe of a cast-in slender steel pipe casting comprises: casting a pouring system of the casting to form a pouring system; threading and fixing the steel pipe in a casting cavity, welding positioning steel bars and sleeve-on anti-deformation annular tie bars on the slender steel pipe before threading and fixing, and sleeve-on elongation-protective iron sleeves at both ends of the slender steel pipe to obtain a casting mold structure with a steel pipe fixing structure; batching the materials for preparing the casting, then heating, smelting, spheroidizing, and inoculating, and pouring the obtained molten iron into the casting mold to form the casting. The method of the present application has the advantages that the slender steel pipe is not easy to float, deform or shift, the air in the pre-buried slender steel pipe will not expand and deform instantly under the action of high-temperature molten iron, and the pouring temperature being too high or too low will not cause the steel pipe to melt, delaminate, or leak.

Description

Technical Field

[0001] The present application relates to the technical field of casting, and specifically to a steel pipe fixing and casting method for an inlaid slender steel pipe casting (i.e., including the steel pipe fixing step and the final casting process to form a complete casting method). Background Art

[0002] In order to meet the requirements of high rigidity, high precision, high speed and other product characteristics of high-speed precision presses, the large high-speed running slider casting used in high-speed precision presses is a very critical component in the equipment. The slider casting is produced using the technology of inserting cast steel pipes, in which the steel pipes are mainly used for the flow and transmission of coolant. The specific slider casting is as follows Figure 1 As shown, the slider casting is made of ductile iron QT450-10, with external hub dimensions of 4240mm×1100mm×750mm, weighing 7.1 tons, a thickness of 110mm at the thickest part, and a local thickness of 30mm, with a large difference in wall thickness. Two slender steel pipes with a wall thickness of 8mm and a diameter of Φ40mm×3900mm are cast in it. This product is a thick-section ductile iron product. To meet the production needs of the subsequent press, the steel pipes cast in the slider casting must not be fixed with traditional core supports. The casting must meet the working conditions of 2MPa hydraulic pressure without seepage or leakage, and the thermal deformation of the casting in the longitudinal direction must be ≤0.1mm. However, this casting technology for existing slider castings has the following five technical difficulties:

[0003] (1) Floating tube problem: The tube floats due to the buoyancy of the molten iron and the thermal expansion deformation. The 35mm thick wall of the upper part and the 20mm thick wall of the side of the casting can easily lead to the tube being exposed. Once exposed, the strength and rigidity of the entire casting will inevitably be reduced, and ultimately the service life of the equipment will be affected.

[0004] (2) Delamination problem: If the pouring temperature is too low, the surface treatment of the steel pipe body is not clean, etc., it will cause poor fusion, and there will be a significant gap between the cast pipe and the slider body, which will cause the cooling effect of the casting to be seriously reduced during operation and produce unusual noises, affecting the service life of the equipment;

[0005] (3) Melt pipe problem: If the pouring temperature is too high, the cooling and protection of the steel pipe are not good during pouring, or the pouring system is improperly designed, the molten iron will directly enter the steel pipe, causing the casting pipe to be blocked and unable to pass the cooling liquid, and the casting will be directly scrapped;

[0006] (4) Leakage (sweating): The casting material structure is not dense, the grains are coarse, or the welding quality of the pipe joint is poor, the pouring temperature is too high, and the joint is washed by molten iron, causing the weld to melt and crack, resulting in the coolant leaking along the interlayer between the cast pipe and the slider body, affecting the service life of the equipment;

[0007] (5) Major safety accidents: Under the heat of molten iron, the gas in the steel pipe expands and cannot be discharged, resulting in an explosion. Summary of the Invention

[0008] In response to the above-mentioned deficiencies in the prior art, the present application provides a method for fixing and casting an embedded slender steel pipe casting, which can achieve the goal that the slender steel pipe is not easily floated, deformed or displaced, the air in the pre-buried slender steel pipe will not expand and deform instantly under the action of high-temperature molten iron, and the pouring temperature is too high or too low and will not cause the steel pipe to melt, delaminate, or leak (sweating) problems.

[0009] In order to solve the above technical problems, the technical solution adopted in this application is: a steel pipe fixing and casting method for inlay casting of slender steel pipe casting, the steps comprising:

[0010] (1) Casting process: First, resin sand casting of the gating system is performed to form a gating system suitable for inserting slender steel pipe castings, the gating system including a sprue, a runner vertically connected to the sprue, and a plurality of ingates vertically connected to the runner and communicating with the casting cavity;

[0011] (2) Steel pipe fixing process: The slender steel pipe is inserted and fixed in the casting cavity. Before insertion and fixing, positioning steel bars are welded on the slender steel pipe and anti-deformation annular reinforcement bars are sleeved on the slender steel pipe, and elongation protection iron sleeves are sleeved on both ends of the slender steel pipe; after the elongation protection iron sleeves are sleeved, a second gap is generated between the slender steel pipe and the radial direction, and a reserved space is generated between the steel pipes in the axial direction;

[0012] Then the sealing mud strip is placed on the sand mold, and the steel pipe with fixed fixed steel bars, sleeved with anti-deformation annular reinforcement and elongation protection iron sleeve is positioned in the casting mold through the positioning steel bars thereon. After the sealing mud strip is wrapped around the steel pipe, the sand core is lowered and fixed, thereby completing the first line of defense for molten iron to enter the steel pipe; the mixed resin sand is injected into the space between the elongation protection iron sleeve and the casting mold and solidified to complete the sand mold formed by the sealing sand; by controlling the outer diameter of the steel pipe and the radial clearance of the elongation protection iron sleeve to be 0.5mm-1.0mm, the axial length reserved between the two ends of the steel pipe and the elongation protection iron sleeve in the axial direction is 20mm-30mm, and the axial matching length of the steel pipe and the elongation protection iron sleeve that overlaps is 90mm-110mm (the overlapping length of the elongation protection iron sleeve and the steel pipe), thereby establishing a second line of defense for molten iron to enter the steel pipe. Once the molten iron passes through the first line of defense and enters the second line of defense, the molten iron can be immediately solidified, thereby achieving the purpose of preventing the molten iron from entering the steel pipe;

[0013] Obtaining a casting mold structure with a steel pipe fixing structure;

[0014] (3) Preparation and pouring of molten iron: The materials for the casting are mixed, then heated, smelted, spheroidized, and inoculated. The obtained molten iron is poured into a casting mold to form a casting.

[0015] Preferably, the cross section of the sprue in step (1) of the present application is circular, the cross section of the runner is trapezoidal, and the cross section of the ingates is trapezoidal; the cross-sectional area ratio of each component of the gating system is: ΣA 直 ∶ΣA 横 ∶ΣA 内 =1∶1.25∶1.1; through the above settings, it is only necessary to calculate the minimum cross-sectional area ΣA 直 , the cross-sectional areas of the remaining components can be determined.

[0016] Preferably, the pouring system also includes a safety riser, a circular air vent and a flat air vent; the safety riser is vertically arranged on the upper surface of the casting cavity and parallel to the straight gate, the circular air vent is located on the upper end surfaces of the left and right ends of the casting cavity and parallel to the straight gate, and the flat air vent is located at the frame position of the upper surface of the casting cavity and parallel to the straight gate; the above structure can effectively reduce the casting defects of the slider casting with this specific structure of the present application.

[0017] Furthermore, the straight gate is a porcelain tube with an inner diameter of Φ100mm, the upper bottom / lower bottom / height of the cross section of the runner is 40mm / 60mm / 100mm, there are 14 inner gates, and the upper bottom / lower bottom / height of the cross section of the inner gate is 62mm / 64mm / 10mm, there are 8 safety risers, and the inner diameter of the safety riser is Φ100mm, there are 4 circular air vents, and the inner diameter of the circular air vent is Φ16mm, there are 8 flat air vents, and the size of the flat air vent is 40mm×15mm (the length and width of the cross section of the flat air vent lower mouth).

[0018] Preferably, the positioning steel bars described in step (2) of the present application include a vertical rod body welded to the slender steel pipe and a horizontal rod body located at the other end of the vertical rod body. The horizontal rod body is placed in the reserved space of the mold and is fixed on the mold after being filled with resin sand and solidified, thereby realizing the positioning and fixation of the steel pipe.

[0019] Preferably, the anti-deformation annular tie bar described in step (2) of the present application includes an annular portion for fitting with the steel pipe, and a fixing portion for fixing. A first gap is provided between the annular portion and the steel pipe in the radial direction, and the width of one side of the gap is 1.0 mm to 1.5 mm, so that the steel pipe can move along the length direction when it expands due to heat without being hindered by the annular portion. The fixing portion is placed in the reserved space of the mold and is fixed on the mold by filling it with resin sand and then curing it.

[0020] Preferably, the elongation protection iron sleeve in step (2) of the present application is placed in the reserved space of the mold, filled with resin sand, and fixed on the mold after solidification.

[0021] Preferably, the wall thickness of the elongation protection iron sleeve in step (2) of the present application is 5mm~20mm, the inner hole is Φ41mm~Φ42mm, the diameter of the positioning steel bar is Φ10mm~Φ12mm, and the diameter of the anti-deformation annular reinforcement is Φ10mm~Φ12mm.

[0022] This application reserves a certain space on the casting mold to facilitate the installation, position adjustment and positioning of steel bars, anti-deformation annular reinforcement and elongation protection iron sleeves, and then fills the reserved space with resin sand to achieve the solidification and fixation of the components, thereby changing the traditional fixing method of core support and effectively solving the problem of steel pipes easily floating, deforming and shifting during the molten iron pouring process.

[0023] Preferably, in step (2) of the present application, an exhaust hole is provided at the end of the elongation protection iron sleeve, and the exhaust hole is used to lead out the gas in the steel pipe; specifically, a ventilation plastic rope can be pre-buried in the exhaust hole and led to the outside of the mold through the exhaust hole, and ignited in time during pouring, so that the hot gas can be effectively and smoothly discharged to the outside, solving the major safety accidents that are prone to gas explosions; air can also be blown through one of the two exhaust holes to accelerate the air flow, thereby cooling the steel pipe and solving the problem of molten iron entering the melting pipe.

[0024] Preferably, in step (2) of the present application, the surface of the entire steel pipe is shot blasted with fine steel shots of Φ2 to Φ3 for 8 to 10 minutes 3 to 4 hours before use; the above process can remove the oxide layer and oil stains on the surface of the pipe, and at the same time form fine bumps on the surface of the steel pipe, so that the steel pipe and the slider casting body can be fused more tightly, and the delamination problem of the steel pipe can be better solved.

[0025] Preferably, in step (3) of the present application, the materials for preparing the casting are batched and then heated and smelted, specifically: (3.1) weighing the following raw materials in mass percentage: 35-45% pig iron, 30-35% scrap steel, 20-35% recycled material, and recarburizer: 0.7-1.2% of the total amount of pig iron, scrap steel, and recycled material; (3.2) placing all the pig iron and scrap steel into a smelting furnace, and then adding a recarburizer of 0.7-1.2% of the total amount of the formula; heating to melt the charge, and adding FeSi75-C ferrosilicon after the charge is melted, the amount of ferrosilicon added is 0.6-0.8% of the total mass of the pig iron, scrap steel and recycled material, to obtain raw iron liquid, and continuing to heat the raw iron liquid to 1440-1480°C; the composition and mass percentage of the raw iron liquid obtained are C 3.50%-3.65%, Si 1.40%~1.55%, Mn0.15%~0.25%, P≤0.04%, S≤0.022%, and the rest is iron.

[0026] Preferably, the spheroidizing and inoculating in step (3) of the present application are specifically as follows: (3.3) spheroidizing is performed by the flushing method, a spheroidizing agent is first added to the spheroidizing dam on one side of the spheroidizing bag and compacted, and then an inoculant with a particle size of 3-8 mm is added and compacted; the spheroidizing agent is a rare earth magnesium alloy, and the mass percentage of the elements thereof is Mg 5.0% to 6.0%, RE 1.0% to 2.0%, Si 42% to 46%, Ca 2.2% to 2.8%, and Al ≤ 1.2%. The spheroidization reaction time is controlled to be completed within 180 seconds, the absorption rate of magnesium and rare earth is improved, the desulfurization effect is enhanced, and the amount of spheroidizer added is correspondingly reduced. The amount of spheroidizer added is controlled between 1.2% and 1.3%, thereby controlling the residual rare earth content and residual magnesium content in the molten iron to a lower range, the residual rare earth content is controlled to be 0.004% to 0.010%, and the residual magnesium content is 0.030% to 0.040%; the amount of inoculant added is 0.5% to 0.8% of the mass of the original molten iron, the inoculant is a silicon-barium inoculant, and the mass percentage of the elements thereof is Si 69% to 74%, Ca 0.5% to 2.0%, Ba 1.5% to 2.5%, Al .2% to 2.5%, S ≤ 0.02%, and the balance is iron; the composition and mass percentage of the obtained molten iron are C 3.40% to 3.50%, Si 2.35% to 2.65%, Mn 0.15%~0.25%, P≤0.04%, S 0.008-0.012%, CE=4.25-4.35, and the rest is iron.

[0027] Preferably, in step (3) of the present application, the molten iron is poured into the casting mold, specifically: (3.4) the molten iron is skimmed and allowed to stand, and when the temperature drops to 1290°C-1350°C, the molten iron is poured into the casting mold to form a casting; while pouring, inoculating with inoculant powder, the addition amount is 0.10%-0.12%, the inoculant powder is a silicon-barium inoculant, and the mass percentage of the elements thereof is Si 69%-74%, Ca 0.5%-2.0%, Ba 1.5%-2.5%, Al.2%-2.5%, S≤0.02%, and the balance is iron; after the casting is cooled, the ductile iron slider casting of the present invention is obtained.

[0028] Preferably, the recarburizer described in the present application is a recarburizer with an element mass percentage of C ≥ 98%, S ≤ 0.05%, N ≤ 0.01%, ash ≤ 0.3%, volatile matter ≤ 0.3%, and a particle size of 0.5-3 mm, such as the DC series recarburizer (DC-(1-4) type recarburizer) produced by Dansheng Industrial (Shanghai) Co., Ltd. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the slider casting of this application.

[0030] Figure 2Schematic diagram of the cross-section of the slider casting.

[0031] Figure 3 Figure 2 A partial enlarged view of .

[0032] As shown in the attached figure: a. Casting body, b. Steel pipe.

[0033] Figure 4 Schematic diagram of the structure of the steel pipe fixing structure of the cast-in steel pipe body casting of the present application.

[0034] Figure 5 Schematic diagram of the structure of the anti-deformation annular reinforcement combined with the steel pipe in this application.

[0035] Figure 6 Partial cross-sectional view of the casting mold of this application.

[0036] Figure 7 Schematic diagram of the structure of the pouring system of this application.

[0037] Figure 8 Top view of the gating system of this application.

[0038] As shown in the attached figure: 1. Steel pipe body, 2. Positioning steel bars, 2.1. Vertical rod body, 2.2. Horizontal rod body, 3. Anti-deformation annular reinforcement, 3.1. Annular part, 3.2. Fixed part, 4. Elongation protection iron sleeve, 4.1. First straight cylinder part, 4.2. Second straight cylinder part, 5. First gap, 6. Second gap, 7. Reserved space, 8. Vent hole, 9. Sand mold, 10. Direct sprue, 11. Horizontal runner, 12. Casting cavity, 13. Ingate, 14. Sealing mud strip, 15. Sand core, 16. Sealing sand mold, 17. Safety riser, 18. Round vent, 19. Flat vent.

[0039] Figure 9 Metallographic structure diagram of the casting obtained in Example 1.

[0040] Figure 10 Metallographic structure diagram of the casting obtained in Example 2. DETAILED DESCRIPTION

[0041] The present application is further described in detail below through examples, but the present application is not limited to the following examples.

[0042] The present application provides a method for fixing and casting a steel pipe of a cast-in slender steel pipe casting, comprising the following steps:

[0043] (1) Casting process: First, resin sand casting of the pouring system is performed to form a pouring system suitable for inserting and casting slender steel pipe castings. The pouring system includes a sprue and a runner vertically connected to the sprue. The runner is vertically connected to a plurality of inner gates connected to the casting cavity; the pouring system is embedded in a casting mold formed by resin sand, and space is reserved in the casting mold in advance for the steel pipe fixing structure to provide space for subsequent position adjustment of the steel pipe and final position fixation;

[0044] Specifically, as attached Figure 6-8 As shown, the pouring system of the present application forms a complete casting mold by combining the shaping of the sand mold with the casting cavity and the steel pipe (the pouring system and the casting cavity formed by the accumulation of resin sand form a complete casting mold, providing support for the pouring of the casting). The casting mold includes a sand mold 9, and a pouring system formed by the sand mold 9 (resin sand is combined with the gate, runner, etc. to form a complete pouring system); the pouring system includes a straight gate 10, a horizontal runner 11 vertically connected to the straight gate 10, and a plurality of inner gates 13 connected to the casting cavity 12 are vertically connected to the horizontal runner 11, and the extension direction of the horizontal runner 11 is parallel to the length direction of the casting cavity 12; the steel pipe b is located in the casting cavity and is fixed in the casting mold by the sand mold 9.

[0045] As a preferred embodiment, the cross section of the sprue 10 of the present application is circular, the cross section of the runner 11 is trapezoidal, and the cross section of the ingate 13 is trapezoidal; the cross-sectional area ratio of the above components in the gating system is: ΣA 直 ∶ΣA 横 ∶ΣA 内 =1∶1.25∶1.1; through the above settings, it is only necessary to calculate the minimum cross-sectional area ΣA 直 , the cross-sectional areas of the remaining components can be determined.

[0046] As attached Figure 7-8 As shown, the pouring system described in the present application also includes a safety riser 17, a circular air vent 18 and a flat air vent 19; the safety riser 17 is vertically arranged on the upper surface of the casting cavity 12 and parallel to the straight gate 10, the circular air vent 18 is located on the upper end surfaces of the left and right ends of the casting cavity 12 and parallel to the straight gate 10, and the flat air vent 19 is located at the frame position of the upper surface of the casting cavity 12 and parallel to the straight gate 10; the above structure can effectively reduce the casting defects of the slider casting with this specific structure of the present application, ensure the effective solidification of the molten iron during the casting process, timely shrinkage compensation, and prevent the generation of slag inclusions.

[0047] As attached Figure 7-8As shown, as a preferred embodiment, the straight gate described in the present application is a porcelain tube with an inner diameter of Φ100mm, the upper bottom / lower bottom / height of the cross section of the runner is 40mm / 60mm / 100mm, there are 14 ingates, and the upper bottom / lower bottom / height of the cross section of the ingates are 62mm / 64mm / 10mm, there are 8 safety risers, and the inner diameter of the safety riser is Φ100mm, there are 4 circular air vents, and the inner diameter of the circular air vent is Φ16mm, there are 8 flat air vents, and the size of the flat air vent is 40mm×15mm (the length and width of the cross section of the flat air vent lower mouth, the upper mouth can be set to the size of the lower mouth; the upper mouth can be set to 60mm×35mm, the flat air vent is a flat cylindrical structure with a larger upper part and a smaller lower part and a rectangular cross section), the above-mentioned safety riser 17, circular air vent 18 and flat air vent 19 are fixed on the casting cavity in a uniformly distributed manner.

[0048] Specifically, as attached Figure 8 As shown, the direct pouring gate 10 of the present application is located in the middle of the cross runner 11, and the inner gate 13 is evenly distributed on the cross runner 11 on both sides of the direct pouring gate 10, and the inner gate 13 is connected to the side of the casting cavity 12 near the bottom, so that the molten iron enters the casting system relatively smoothly, reducing the casting defects of the casting.

[0049] The above-mentioned pouring system of the present application will not cause molten iron to directly enter the steel pipe, and therefore will not cause the casting pipe to be blocked and the cooling liquid to be unable to pass, and the casting to be directly scrapped.

[0050] (2) Steel pipe fixing process: The slender steel pipe is inserted and fixed in the casting cavity. Before insertion and fixing, positioning steel bars are welded on the slender steel pipe and anti-deformation annular reinforcement bars are sleeved on the slender steel pipe, and elongation protection iron sleeves are sleeved on both ends of the slender steel pipe; after the elongation protection iron sleeves are sleeved, a second gap is generated between the slender steel pipe and the radial direction, and a reserved space is generated between the steel pipes in the axial direction;

[0051] Specifically, the steel pipe fixing process of the present application obtains a steel pipe fixing structure as shown in the attached Figure 4-6As shown, the structure includes a steel pipe body 1 arranged in a casting a (or it can be said to be arranged in a casting cavity), the steel pipe body 1 is provided with a positioning steel bar 2 and an anti-deformation annular tie bar 3, and both ends of the steel pipe body 1 are fitted with an elongation protection iron sleeve 4; one end of the positioning steel bar 2 is welded to the steel pipe body, and the other end is connected to the casting mold by filling resin sand for solidification (the casting mold of the present application includes a sand mold for constructing a casting system, and a steel pipe fixing structure pre-embedded in the sand mold, which together constitute a complete casting mold for casting to obtain a casting. On the basis of the completion of the design of the steel pipe fixing structure and the casting system of the present application , the step of performing sand filling molding to obtain a casting is a conventional sand filling molding step in the industry); one end of the anti-deformation annular tie bar 3 is provided with an annular portion 3.1, and the annular portion 3.1 is fitted on the steel pipe body 1 and a first gap 5 is provided between the annular portion 3.1 and the outer diameter of the steel pipe body 1, and the other end of the anti-deformation annular tie bar 3 is connected to the casting by filling resin sand and solidifying; a second gap 6 is provided between the elongation protection iron sleeve 4 and the outer diameter of the steel pipe body 1, and a reserved space 7 is provided axially between the two ends of the steel pipe body 1 and the elongation protection iron sleeve 4, and the elongation protection iron sleeve 4 is connected to the casting by filling resin sand and solidifying. In the process of forming the casting, the present application reserves space in advance for the positioning steel bars, anti-deformation annular reinforcement and elongation protection iron sleeve for fixing to the casting. After the fixing part enters the appropriate position, the reserved space is filled with resin sand and solidified to fix the position of the positioning steel bars, anti-deformation annular reinforcement and elongation protection iron sleeve in the casting, thereby fixing the position of the steel pipe, thereby minimizing the impact of the subsequent molten iron pouring process on the steel pipe.

[0052] As attached Figure 4 As shown, the positioning steel bar 2 described in this application includes a vertical rod body 2.1 welded to the steel pipe body and a horizontal rod body 2.2 located at the other end of the vertical rod body. The horizontal rod body 2.2 is used to be placed in the reserved space of the mold and fixed on the mold after being filled with resin sand and solidified, so as to realize the positioning and fixation of the steel pipe body; the specific vertical rod body is perpendicular to the steel pipe body, and the horizontal rod body is vertically connected to the end of the vertical rod body. The end is placed in the reserved space of the mold and filled with resin sand to achieve position positioning.

[0053] As attached Figure 4-5As shown, the anti-deformation annular tie bar 3 described in the present application includes an annular portion 3.1 for fitting with the steel pipe body, and a fixing portion 3.2 for fixing. A first gap 5 is provided between the annular portion 3.1 and the outer diameter of the steel pipe body, and the single side of the gap is 1.0mm to 1.5mm (i.e., the width of the gap is 1.0mm to 1.5mm); the fixing portion 3.2 is placed in the reserved space of the mold and fixed to the mold after being filled with resin sand and solidified; the specific fixing portion includes a vertical portion perpendicular to the steel pipe body and a horizontal portion perpendicular to the vertical portion. With the above structure, the gap between the reserved annular portion and the radial direction of the steel pipe facilitates the movement of the steel pipe along the length direction when it expands due to heat, so that it is not hindered by the annular portion.

[0054] As a preferred embodiment of the present application, the wall thickness of the elongation protection iron sleeve 4 described in the present application is 5mm~20mm, the inner hole position is Φ41mm~Φ42mm, the diameter of the positioning steel bar 2 is Φ10mm~Φ12mm, and the diameter of the anti-deformation annular reinforcement 3 is Φ10mm~Φ12mm.

[0055] After obtaining the above steel pipe fixing structure, the steel pipe fixing structure and the pouring system are combined and sand casting is performed together to obtain the casting mold of the slider casting. Figure 6 As shown, first place the sealing mud strip 14 on the sand mold 9, and the steel pipe b with the anti-deformation annular reinforcement 3 and the elongation protection iron sleeve 4 inserted is positioned in the mold by the positioning steel bar 2. After the sealing mud strip 14 is wrapped around the steel pipe b, the sand core 15 (a structure for forming the internal shape of the casting) is lowered and fixed, thus completing the first line of defense for molten iron to enter the steel pipe; the mixed resin sand is injected into the reserved space between the elongation protection iron sleeve 4 and the mold and solidified to complete the sealing sand mold 16; by controlling the outer diameter of the steel pipe and the radial clearance of the elongation protection iron sleeve to be 0.5mm-1.0mm (the second Gap 6), the axial length reserved between the two ends of the steel pipe and the elongation protection iron sleeve is 20mm~30mm (L), the axial fitting length of the steel pipe and the elongation protection iron sleeve is 90mm~110mm (the overlapping length between the elongation protection iron sleeve and the steel pipe after they are fitted together), which establishes a second line of defense for molten iron to enter the steel pipe. Once the molten iron passes through the first line of defense and enters the second line of defense, the molten iron can be solidified immediately (the gap is small, the axial fitting length is long, the amount of molten iron entering is small, the solidification is fast, and it will not enter the inside of the steel pipe), thereby achieving the purpose of preventing molten iron from entering the steel pipe. In addition, the gas in the steel pipe can be led out through two exhaust holes. A ventilation plastic rope can be pre-buried in the exhaust hole and led to the outside of the mold through the exhaust hole. It can be ignited in time during pouring, so that the hot gas can be discharged effectively and smoothly to the outside, solving the major safety accidents that are prone to gas explosions. Air can also be blown through one of the two exhaust holes to speed up the air flow, thereby cooling the steel pipe and solving the problem of molten iron entering the melting pipe.

[0056] As attached Figure 6 As shown, the end of the elongation protection iron sleeve 4 described in the present application is provided with an exhaust hole 8, and the exhaust hole 8 is used to lead the gas in the steel pipe body 1 out; specifically, a ventilation plastic rope can be pre-buried in the exhaust hole 8 and led to the outside of the mold through the exhaust hole, and ignited in time during pouring, so that the hot gas is effectively and smoothly discharged to the outside, solving the major safety accidents that are prone to gas explosions; air can also be blown through one of the two exhaust holes and exhausted from the other exhaust hole, thereby accelerating the air flow, and also achieving the cooling of the steel pipe and solving the problem of molten iron entering the melting pipe of the steel pipe;

[0057] Obtaining a casting mold structure with a steel pipe fixing structure;

[0058] (3) Preparation and pouring of molten iron: The materials for the casting are mixed, then heated, smelted, spheroidized, and inoculated. The obtained molten iron is poured into a casting mold to form a casting.

[0059] The molding processes of the molds of this application are all conventional processes in the industry. The innovation of this application lies in the method of setting up the fixed structure of the steel pipe in the mold, the method of setting up the pouring system, and the proportioning, spheroidization, inoculation and pouring casting methods of the molten iron components, which are combined with each other to form a complete casting method.

[0060] Specifically, the specific embodiment of the slider casting of the present application using the specific steel pipe fixing method of the present application is as follows:

[0061] Example 1

[0062] (1) Weigh the following raw materials in mass percentage: pig iron 40%, scrap steel 35%, recycled materials 25%, and recarburizer: 0.9% of the total amount of pig iron, scrap steel, and recycled materials; the recarburizer is the DC series recarburizer (DC-(1-4) type recarburizer) produced by Dansheng Industrial (Shanghai) Co., Ltd.;

[0063] (2) All the pig iron and scrap steel are placed in a smelting furnace, and then a carburizer with a total weight of 0.8% is added; the furnace charge is heated to melt, and after the furnace charge is completely melted, FeSi75-C ferrosilicon is added, and the amount of ferrosilicon added is 0.65% of the total weight of the pig iron, scrap steel and recycled materials to obtain molten iron, which is further heated to 1450°C; the composition and mass percentage of the obtained molten iron are C 3.50%, Si 1.46%, Mn 0.20%, P 0.027%, S 0.017%, and the remainder is iron;

[0064] (3) The spheroidization is carried out by the flushing method. The spheroidizing agent is first added to the spheroidizing dam on one side of the spheroidizing bag and compacted. Then, the inoculant with a particle size of 3 to 8 mm is added and compacted.

[0065] The spheroidizing agent is a rare earth magnesium alloy, whose element weight percentage is Mg 5.2%, RE 1.5%, Si 42%, Ca 2.3%, and Al 0.72%. The amount of spheroidizing agent added is 1.25% (of the total amount of the original iron liquid), and the spheroidizing reaction time is 120 seconds.

[0066] The amount of inoculant added is 0.75% of the total mass of the original iron liquid. The inoculant is a silicon-barium inoculant, and its element mass percentages are Si 70%, Ca 1.26%, Ba 2.34%, Al 1.33%, S 0.02%, and the balance is iron.

[0067] The composition and mass percentage of the obtained iron liquid are C 3.46%, Si 2.44%, Mn 0.20%, P 0.027%, S0.0094%, CE=4.27, and the rest is iron;

[0068] (4) The molten iron is skimmed and allowed to stand. When the temperature drops to 1300°C, the molten iron is poured into a mold to form a casting. Simultaneously with the pouring, an inoculant is added in an amount equal to 0.10% of the total mass of the base iron. The composition and mass percentage of the inoculant are Si 70%, Ca 1.26%, Ba 2.34%, Al 1.33%, and S 0.02%. After the casting cools, the ductile iron slider casting of the present invention is obtained.

[0069] Table 1 Mechanical properties of cast test blocks

[0070]

[0071]

[0072] Table 2 Metallographic structure of the cast test block

[0073] project Spheroidization rate Graphite size Metallographic structure (see Figure 9 ) Standard value ≥90％ 4～7 High spheroidization rate, graphite size meets requirements

[0074] The metallographic structure of the casting obtained in Example 1 is shown in the attached Figure 9 shown.

[0075] Example 2

[0076] (1) Weigh the following raw materials in mass percentage: 35% pig iron, 35% scrap steel, 30% recycled material, and a recarburizer: 1.0% of the total amount of pig iron, scrap steel, and recycled material; the recarburizer is a DC series recarburizer (DC-(1-4) type recarburizer) produced by Dansheng Industrial (Shanghai) Co., Ltd.;

[0077] (2) All the pig iron and scrap steel are placed in a smelting furnace, and then a carburizer of 1.0% of the total formula is added; the furnace charge is heated to melt, and after the furnace charge is completely melted, FeSi75-C ferrosilicon is added, and the amount of ferrosilicon added is 0.64% of the total mass of the pig iron, scrap steel and recycled materials to obtain raw iron liquid, and the raw iron liquid is further heated to 1480°C; the composition and mass percentage of the raw iron liquid obtained are C 3.55%, Si 1.50%, Mn 0.23%, P 0.024%, S 0.019%, and the remainder is iron;

[0078] (3) The spheroidization is carried out by the flushing method. The spheroidizing agent is first added to the spheroidizing dam on one side of the spheroidizing bag and compacted, and then the inoculant with a particle size of 3-8 mm is added and compacted.

[0079] The spheroidizing agent is a rare earth magnesium alloy, whose element weight percentage is Mg 5.2%, RE 1.5%, Si 42%, Ca 2.3%, and Al 0.72%. The spheroidizing agent addition amount is 1.3%, and the spheroidizing reaction time is 110 seconds.

[0080] The amount of inoculant added is 0.72% of the mass of the original iron liquid. The inoculant is a silicon-barium inoculant, and its element mass percentages are Si 70%, Ca 1.26%, Ba 2.34%, Al 1.33%, S 0.02%, and the balance is iron.

[0081] The composition and mass percentage of the obtained iron liquid are C 3.49%, Si 2.50%, Mn 0.23%, P 0.024%, S0.010%, CE=4.32, and the rest is iron;

[0082] (4) The molten iron is skimmed and allowed to stand. When the temperature drops to 1340°C, the molten iron is poured into a mold to form a casting. Simultaneously with the pouring, an inoculant is added in an amount of 0.12% of the total mass of the original molten iron. The composition and mass percentage of the inoculant are Si 70%, Ca 1.26%, Ba 2.34%, Al 1.33%, and S 0.02%. After the casting is cooled, the ductile iron slider casting of the present invention is obtained.

[0083] Table 3 Mechanical properties of cast test blocks

[0084] project Tensile strength (MPa) Yield strength (MPa) Elongation (%) Hardness (HB) Remark Standard value ≥390 ≥260 ≥8.0 140～190 Customer Standards Measured value 400 274 10.5 150 Product Testing

[0085] Table 4 Metallographic structure of the cast test block

[0086] project Spheroidization rate Graphite size Metallographic structure (see Figure 10 ) Standard value ≥90％ 4～7 High spheroidization rate, graphite size meets requirements

[0087] The metallographic structure of the casting obtained in Example 2 is shown in the attached Figure 10 shown.

Claims

1. A method for fixing and casting a steel pipe for a slender steel pipe casting, characterized in that: include: (1) Casting process: First, resin sand casting of the gating system is performed to form a gating system suitable for inserting slender steel pipe castings, the gating system including a sprue, a runner vertically connected to the sprue, and a plurality of ingates vertically connected to the runner and communicating with the casting cavity; (2) Steel pipe fixing process: The slender steel pipe is inserted and fixed in the casting cavity. Before insertion and fixing, positioning steel bars are welded on the slender steel pipe and anti-deformation annular reinforcement bars are sleeved on the slender steel pipe, and elongation protection iron sleeves are sleeved on both ends of the slender steel pipe; after the elongation protection iron sleeves are sleeved, a second gap is generated between the slender steel pipe and the radial direction, and a reserved space is generated between the steel pipes in the axial direction; Then, the sealing mud strip is placed on the sand mold, and the steel pipe fixed with fixed steel bars, sleeved with anti-deformation annular reinforcement and elongation protection iron sleeve is positioned in the casting mold through the positioning steel bars thereon. After the sealing mud strip is wrapped around the steel pipe, the sand core is lowered and fixed, thus completing the first line of defense against molten iron entering the steel pipe; the mixed resin sand is injected into the space between the elongation protection iron sleeve and the casting mold and solidified to complete the sand sealing and form a sand-sealed sand mold; by controlling the outer diameter of the steel pipe and the radial clearance of the elongation protection iron sleeve to 0.5mm-1.0mm, the axial length reserved between the two ends of the steel pipe and the elongation protection iron sleeve in the axial direction is 20mm-30mm, and the axial matching length of the steel pipe and the elongation protection iron sleeve overlapping is 90mm-110mm, thus establishing the second line of defense against molten iron entering the steel pipe; Obtaining a casting mold structure with a steel pipe fixing structure; (3) Preparation and pouring of molten iron: The materials for the casting are mixed, then heated, smelted, spheroidized, and inoculated. The obtained molten iron is poured into a casting mold to form a casting.

2. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 1, characterized in that: In step (1), the cross section of the sprue is circular, the cross section of the runner is trapezoidal, and the cross section of the ingates is trapezoidal; the cross-sectional area ratio of each component of the gating system is: ΣA 直 ∶ΣA 横 ∶ΣA 内 =1∶1.25∶1.

1.

3. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 1, characterized in that: The pouring system also includes a safety riser, a round gas outlet and a flat gas outlet; the safety riser is vertically arranged on the upper surface of the casting cavity and parallel to the straight gate, the round gas outlet is located on the upper end surfaces of the left and right ends of the casting cavity and parallel to the straight gate, and the flat gas outlet is located at the frame position of the upper surface of the casting cavity and parallel to the straight gate.

4. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 3, characterized in that: The sprue is a porcelain tube with an inner diameter of Φ100mm. The upper bottom / lower bottom / height of the cross section of the runner is 40mm / 60mm / 100mm. There are 14 ingates, and the upper bottom / lower bottom / height of the cross section of the ingates are 62mm / 64mm / 10mm. There are 8 safety risers, and the inner diameter of the safety risers is Φ100mm. There are 4 circular air vents, and the inner diameter of the circular air vents is Φ16mm. There are 8 flat air vents, and the size of the flat air vents is 40mm×15mm.

5. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 1, characterized in that: The positioning steel bars described in step (2) include a vertical rod body welded to the slender steel pipe and a horizontal rod body located at the other end of the vertical rod body. The horizontal rod body is placed in the reserved space of the mold and fixed on the mold after being filled with resin sand and solidified, thereby realizing the positioning and fixation of the steel pipe.

6. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 1, characterized in that: The anti-deformation annular tie bar described in step (2) includes an annular portion for fitting with the steel pipe and a fixing portion for fixing, a first gap is provided between the annular portion and the steel pipe in radial direction, and the single-side width of the first gap is 1.0 mm to 1.5 mm; the fixing portion is placed in the reserved space of the mold and is fixed on the mold after being filled with resin sand and solidified; the elongation protection iron sleeve described in step (2) is placed in the reserved space of the mold and is fixed on the mold after being filled with resin sand and solidified.

7. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 1, characterized in that: The wall thickness of the elongation protection iron sleeve described in step (2) is 5mm~20mm, the inner hole is Φ41mm~Φ42mm, the diameter of the positioning steel bar is Φ10mm~Φ12mm, and the diameter of the anti-deformation annular reinforcement is Φ10mm~Φ12mm.

8. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 1, characterized in that: The end of the elongation protection iron sleeve described in step (2) is provided with an exhaust hole, and the exhaust hole is used to lead out the gas in the steel pipe; in step (2), the surface of the entire steel pipe is shot blasted with fine steel shots of Φ2mm to Φ3mm for 8 to 10 minutes 3 to 4 hours before use.

9. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 1, characterized in that: In step (3), the materials for preparing the casting are batched and then heated and smelted, specifically: (3.1) weighing the following raw materials in mass percentage: 35-45% pig iron, 30-35% scrap steel, 20-35% recycled material, and recarburizer: 0.7-1.2% of the total amount of pig iron, scrap steel, and recycled material; (3.2) placing all the pig iron and scrap steel into a smelting furnace, and then adding a recarburizer of 0.7-1.2% of the total amount of the formula; heating to melt the charge, and adding FeSi75-C ferrosilicon after the charge is melted, the amount of ferrosilicon added is 0.6-0.8% of the total mass of the pig iron, scrap steel and recycled material, to obtain raw iron liquid, and continuing to heat the raw iron liquid to 1440-1480°C; the composition and mass percentage of the obtained raw iron liquid are C 3.50%-3.65%, Si 1.40%~1.55%, Mn0.15%~0.25%, P≤0.04%, S≤0.022%, and the rest is iron.

10. The method for fixing and casting a steel pipe of a cast-in slender steel pipe according to claim 9, characterized in that: The spheroidization and inoculation in step (3) are specifically as follows: (3.3) the spheroidization is carried out by the flushing method, the spheroidizing agent is first added to the spheroidizing dam on one side of the spheroidizing bag and compacted, and then the inoculant with a particle size of 3-8 mm is added and compacted; the spheroidizing agent is a rare earth magnesium alloy, and the mass percentage of the elements is Mg 5.0% to 6.0%, RE 1.0% to 2.0%, Si The invention relates to a novel molten iron melt comprising a molten iron melt and a molten iron melt having a molten iron content of 42% to 46%, Ca 2.2% to 2.8%, and Al ≤ 1.2%. The spheroidization reaction time is controlled to be completed within 180s, thereby improving the absorption rate of magnesium and rare earth, enhancing the desulfurization effect, and correspondingly reducing the amount of spheroidizer added, the amount of spheroidizer added is controlled between 1.2% and 1.3%, thereby controlling the residual rare earth content and residual magnesium content in the molten iron to a lower range, the residual rare earth content is controlled between 0.004% and 0.010%, and the residual magnesium content is 0.030% to 0.040%. The amount of inoculant added is 0.5 to 0.8% of the mass of the original molten iron. The inoculant is a silicon-barium inoculant, and the mass percentages of the elements thereof are Si 69% to 74%, Ca 0.5% to 2.0%, Ba 1.5% to 2.5%, Al.2% to 2.5%, S ≤ 0.02%, and the balance is iron. The composition and mass percentages of the obtained molten iron are C 3.40% to 3.50%, Si 2.35%~2.65%, Mn 0.15%~0.25%, P≤0.04%, S 0.008-0.012%, CE=4.25-4.35, the rest is iron; In step (3), the molten iron is poured into the casting mold, specifically: (3.4) the molten iron is skimmed and allowed to stand, and when the temperature drops to 1290°C-1350°C, the molten iron is poured into the casting mold to form a casting; while pouring, the molten iron is inoculated with inoculant powder, the addition amount of which is 0.10%-0.12%, the inoculant powder is a silicon-barium inoculant, and the mass percentage of the elements thereof is Si 69%-74%, Ca 0.5%-2.0%, Ba 1.5%-2.5%, Al.2%-2.5%, S≤0.02%, and the balance is iron; after the casting is cooled, a ductile iron slider casting is obtained; The recarburizer has the following elements: C≥98%, S≤0.05%, N≤0.01%, ash≤0.3%, volatile matter≤0.3%, and a particle size of 0.5-3 mm.

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