Common-mold pouring and performance-balanced casting method for different castings with large wall thickness difference
By designing pits in the casting mold of large thick parts and adding antimony powder to mix them with molten iron, the problem of unbalanced performance in common mold production of different castings with large wall thickness differences is solved, and the effect of saving mold costs and improving production efficiency is achieved.
Patent Information
- Application Number
- CN202411781972.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-05
- Publication Date
- 2025-03-07
AI Technical Summary
In the casting process, when the common mold of different castings with large wall thickness differences is difficult to achieve performance balance, resulting in slow solidification and cooling speed of thick and large parts, and thin-walled parts are prone to white mouths or high hardness.
By designing a pit at the bottom of the inner gate of the thick and large parts casting mold and adding pure antimony powder to the pit, the antimony powder is evenly mixed with the molten iron by vortex, and the graphite refinement and pearlite content of the casting are adjusted, thereby achieving balanced performance of thick and large parts and thin-walled parts.
The common mold casting of castings with large wall thickness differences is achieved, which saves mold costs, improves production efficiency, reduces mold manufacturing cycle, and simplifies the production scheduling process.
Smart Images
Figure CN119566225A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of casting technology, and in particular relates to a casting method for casting different castings with large wall thickness differences into a common mold and with balanced performance. Background Art
[0002] Iron mold sand coating process molds are expensive and the manufacturing cycle is relatively long. When faced with the need to develop multiple products, for production efficiency and mold cost considerations, it is often desired to arrange different products in the same set of molds. However, castings vary in size and wall thickness, so the solidification and cooling rates of the two are also different, resulting in slow solidification and cooling rates for thick and large parts, causing problems such as coarse graphite and coarse structure, and low pearlite; thin-walled parts solidify and cool quickly, which is prone to white spots or high hardness problems.
[0003] If the contradiction cannot be resolved, the molds can only be opened separately, which has a great impact on production scheduling, mold change efficiency and mold cost. Therefore, an effective method is needed to meet the co-molding requirements of different castings with large wall thickness differences, effectively adjust their respective performance to meet the requirements, and be able to be stably applied. Summary of the invention
[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a casting method for co-molding different castings with large differences in wall thickness and balanced performance. The purpose is to combine the iron mold sand coating process design and smelting technology when co-molding different castings with a wall thickness and weight difference of three to ten times, so as to stably adjust their respective performances to ensure that the technical requirements are met, realize co-molding production, save mold costs, improve production efficiency and reduce costs, thereby solving the problem of uneven performance due to individual differences when different castings with large differences in wall thickness are arranged in the same set of molds for co-casting.
[0005] In order to achieve the above object, the specific scheme of the present invention is as follows:
[0006] A casting method for casting different castings with large wall thickness differences in common mold and balanced performance includes the following steps:
[0007] Step 1: Arrange the mold according to the size and parting scheme of thick and large parts and thin-walled parts, and draw the upper and lower outer molds, upper and lower iron molds;
[0008] Step 2, reducing the thickness of the sand coating layer of the upper and lower iron molds corresponding to the thick and large casting positions in step 1;
[0009] Step 3, designing a protrusion at the gate position of the thick casting of the lower outer mold in step 1, obtaining an upper mold and a lower mold after the molding is completed, forming a pit at the position corresponding to the protrusion of the thick casting of the lower mold, and placing pure antimony powder in the pit;
[0010] Step 4, smelting molten iron according to the alloy composition of the thin-walled casting, pouring the molten iron into the cavity formed by the upper casting mold and the lower casting mold, to obtain thick and large castings and thin-walled castings with balanced performance.
[0011] Furthermore, the wall thickness of the thick and large parts and the thin-walled parts in step 1 differ by three to ten times or more.
[0012] Furthermore, the thickness of the iron mold sand coating layer in step 2 is designed to be thinned to a thickness of 4 to 6 mm.
[0013] Further, if the thick and large parts and thin-walled parts in step 1 are made of ductile iron, the amount of pure antimony powder added in step 3 is 0.005-0.006% of the weight of the thick and large parts; if the thick and large parts and thin-walled parts in step 1 are made of gray iron, the amount of pure antimony powder added in step 3 is 0.02-0.025% of the weight of the thick and large parts; if the thick and large parts and thin-walled parts in step 1 are made of vermicular iron, the amount of pure antimony powder added in step 3 is 0.015-0.025% of the weight of the thick and large parts; the size of the pit is set according to the volume of the added antimony powder, and the antimony powder volume accumulation thickness is 2-3mm or occupies 1 / 5-1 / 3 of the volume of the pit, and the protrusion is set in an arc shape. .
[0014] The method is applied in preparing a QT700-10 air deflector bracket and high-speed locking parts.
[0015] Furthermore, the alloy components of the deflector support are copper and manganese, and the weight percentages of copper and manganese in the molten iron are 0.3% and 0.28% respectively.
[0016] The method is applied in preparing support seat body and stable retaining frame parts with grade HT250.
[0017] Furthermore, the alloy components of the stabilizing cage are copper, manganese and chromium, and the weight percentages of copper, manganese and chromium are 0.3-0.35%, 0.6-0.7% and 0.15% respectively.
[0018] Advantages of the present invention
[0019] The casting method of the present invention for casting different castings with large wall thickness differences and balanced performance in a common mold has the following advantages:
[0020] (1) The casting method of the present invention is to set a pit at the bottom of the inner gate of the thick and large parts casting mold, and add antimony powder into the pit. During pouring, eddy currents will be generated when the molten iron passes through the pit, and the antimony powder in the pit will be drawn in and mixed evenly, and then enter the casting; under the effect of the addition of antimony element, the casting can achieve the effect of graphite refinement, pearlite content and quality improvement. The method of adding antimony in the casting mold can be applied to the co-molding of thick and large parts and thin-walled parts made of gray iron, ductile iron and vermicular iron. Therefore, co-molding of different castings with wall thickness differences of three to ten times can be achieved, and there is no need to make their own iron mold sand-coated mold tooling separately. The design of the molten iron alloy composition does not need to compromise between thin-walled parts and thick and large parts. It only needs to be designed according to the performance requirements of thin-walled castings. Thin-walled parts and thick and large parts can meet the same grade requirements at the same time, which can achieve the purpose of saving mold costs, improving production efficiency, shortening mold manufacturing cycle, and convenient production scheduling. Even if multiple parts are produced with the same mold, there is no need to consider the mold change time when scheduling production, which makes scheduling easier and improves production efficiency.
[0021] (2) The smelting process of this method is simple. There is no need to adjust different melting processes for different products. Only the thin-walled parts process can be used to cast thin-walled parts and thick-walled parts at the same time, saving adjustment time and smelting energy consumption. This expands the implementation method of the iron mold sand coating process. It is a method that can meet the common mold production of thick and thin-walled parts. It has reference significance for foundry workers. The use of new technologies has played a positive role in the development of iron mold sand coating technology and product development. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 Flow chart of the casting method of the present invention.
[0023] Figure 2 for Figure 1 The schematic diagram of the structure of the upper outer mold for the thin-walled parts and the thick and large parts manufactured by the method is arranged in the same mold.
[0024] Figure 3 for Figure 1 The schematic diagram of the structure of the lower outer mold for the thin-walled parts and the thick and large parts manufactured by the method is arranged in the same mold.
[0025] Figure 4 for Figure 3 An enlarged view of some of the structures of the middle and lower outer mold.
[0026] Figure 5 Schematic diagram of the structure of the upper casting mold.
[0027] Figure 6 Schematic diagram of the structure of the lower casting mold.
[0028] Figure 7 for Figure 6 An enlarged view of some of the structures of the middle and lower molds.
[0029] In the figure:
[0030] 1. Upper outer mold; 2. Lower outer mold; 3. Upper casting mold; 4. Lower casting mold; 5. Thick and large castings; 6. Thin-walled castings; 7. Ingate; 8. Protrusions; 9. Concave pits. DETAILED DESCRIPTION
[0031] The present invention is further explained and illustrated below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that this specific embodiment is not intended to limit the scope of rights of the present invention.
[0032] like Figures 1 to 7 As shown, the present invention provides a casting method for co-molding different castings with large wall thickness differences and balanced performance, characterized by comprising the following steps:
[0033] Step 1: When designing the iron mold sand coating process, the upper outer mold 1, the lower outer mold 2, the upper iron mold and the lower iron mold are arranged in a common mold according to the size and parting scheme of thick and large parts and thin-walled parts with a wall thickness difference of three to ten times, such as Figure 2 , 3 , 5, and 6. The thick casting 5 pattern in the upper outer mold 1 and the thin-walled casting 6 pattern in the upper outer mold 1 are conventionally arranged.
[0034] Step 2, the conventional thickness of the iron mold sand coating of thick and large castings is 6 to 10 mm, therefore, the thickness of the iron mold sand coating corresponding to the positions of the thick and large castings 5 in the upper and lower iron molds described in step 1 is designed to be thinned to 4 to 6 mm.
[0035] Step 3, design a protrusion 8 at the ingate position of the thick casting 5 of the lower outer mold 1, and the protrusion 8 is set to be an arc shape, such as Figure 3 and Figure 4 As shown. After the molding is completed, the upper mold 3 and the lower mold 4 are obtained, and a pit 9 is formed at the position of the thick casting corresponding to the protrusion 8 in the lower mold 4, and pure antimony powder is placed in the pit 9; if the thick and large parts and thin-walled parts in step 1 are made of ductile iron, the amount of pure antimony powder added is 0.005-0.006% of the weight of the thick and large parts; if the thick and large parts and thin-walled parts in step 1 are made of gray iron, the amount of pure antimony powder added is 0.02-0.025% of the weight of the thick and large parts; if the thick and large parts and thin-walled parts in step 1 are made of vermicular iron, the amount of pure antimony powder added is 0.015-0.025% of the weight of the thick and large parts; the size of the pit is set according to the volume of the antimony powder added, and the antimony powder volume accumulation thickness is 2-3mm or occupies 1 / 5-1 / 3 of the volume of the pit. The size of the pit 9 is set according to the volume of the antimony powder added. The size of the pit 9 is designed so that the antimony powder volume accumulation thickness is 2 to 3 mm or occupies 1 / 5 to 1 / 3 of the volume of the pit 9.
[0036] During pouring, the molten iron flows through the inner gate 7 and the pit 9 in the cavity formed by the upper casting mold 3 and the lower casting mold 4, so that the cross section is enlarged and eddy current is generated, so that the antimony powder in the pit 9 is drawn into the molten iron to be melted and mixed. Antimony has a low melting point, generally 600°C. The casting is filled with molten iron mixed with antimony powder; the two characteristics of antimony in cast iron, graphite refining and pearlite promotion, can significantly improve the graphite grade and structure refinement of thick and large parts, improve the quality and quantity of pearlite, and improve mechanical properties;
[0037] Step 4, smelting molten iron according to the alloy composition of the thin-walled casting 6. Usually, the alloy composition of cast iron is manganese, copper, tin and chromium. There is no need to consider increasing the alloy element content for the thick and large casting 5; pouring the smelted molten iron into the cavity formed by the upper casting mold 3 and the lower casting mold 4 to obtain the thick and large casting 5 and the thin-walled casting 6 with balanced performance.
[0038] The thick and large castings 5 and thin-walled castings 6 with balanced performance are cooled to the unpacking process, and the upper box is directly opened to take out the castings, and then they can be circulated according to the normal circulation process. The thin-walled parts can meet the mechanical performance requirements, and the thick and large parts can also meet the mechanical performance requirements under the condition of very low content of alloy elements such as manganese and copper because of the addition of antimony powder separately.
[0039] The casting method of the above specific embodiment casts different castings with wall thickness differences of three to ten times into a common mold, and the specific settings and specific processes of the parting surface, core head, machining allowance and pouring system of the thin-walled casting 5 and the thick large casting 6 not mentioned in the above casting method are conventional settings in the field, so they are not repeated. The alloy composition design of the molten iron does not need to compromise between the thin-walled casting 5 and the thick large casting 6. It only needs to be designed according to the performance requirements of the thin-walled casting 6. The thin-walled parts and the thick large parts can meet the same grade requirements at the same time, achieving the purpose of saving mold investment, improving production efficiency, and convenient production scheduling. A pit 9 is designed at the bottom of the inner gate 7 of the thick large casting 5, and antimony powder is added to the pit 9. During pouring, eddy currents will be generated when the molten iron passes through the pit 9, and the antimony powder in the pit 9 will be drawn in, and it can be mixed evenly and enter the casting; under the action of the addition of antimony elements, the thick large casting 5 can achieve the effect of graphite refinement, pearlite content and quality improvement.
[0040] The method of adding antimony into the casting mold can be applied to the co-molding of thick and large castings 5 and thin-walled castings 6 made of gray iron, ductile iron and vermicular iron.
[0041] Experiment 1: Casting test to adjust the thickness of the sand layer to balance the differences in solidification and cooling of different castings
[0042] In the actual iron mold sand coating process, this specific embodiment balances the solidification and cooling differences of different castings by adjusting the thickness of the sand coating layer to conduct casting tests. The sand coating layer of the thick and large casting 5 is thinned, but the minimum can only be about 4mm. If it is thinner, it will affect the integrity and compactness of the sand shot; the thickness of the sand coating layer of the thin-walled casting 6 is appropriately increased, but when it is increased to more than 10-12mm, the cooling is very slow, and the technical advantages of the iron mold sand coating process are lost. According to the production test results, the sand coating layer cannot be infinitely thickened or infinitely thinned. The adjustment range of the sand coating layer is limited. It has a certain effect within the range of 1 to 3 times the difference in the wall thickness of the casting, but beyond this range, adjusting the sand coating layer cannot make the performance of thick and large parts and thin-walled parts meet the requirements.
[0043] Experiment 2: Casting test of adjusting the alloy content of molten iron for co-molding of different castings with large differences in wall thickness
[0044] This specific embodiment also conducts casting tests on different castings with different wall thicknesses by adjusting the alloy content of the molten iron, so that the strength of the thick and large casting 5 is not too low, and the strength and hardness of the thin-walled casting 6 is not too high. However, this adjustment range is very narrow, and the control is very difficult, and sometimes it is impossible to find a balance point.
[0045] Example 1 A certain type of air deflector bracket and high-speed locking parts
[0046] The casting method is used to cast a certain type of air deflector bracket and high-speed locking parts, including the following steps:
[0047] Step 1: When designing the iron mold sand coating process, the upper outer mold, lower outer mold, upper iron mold and lower iron mold are arranged according to the size and parting scheme of the high-speed locking parts and the air deflector bracket. The air deflector bracket has a wall thickness of 20mm and a weight of 25kg; the high-speed locking parts have a wall thickness of 150mm and a weight of 85kg. The grade requirements for both parts are QT700-10.
[0048] Step 2, the iron mold sand coating of the air deflector bracket is set to 8 mm, and the thickness of the iron mold sand coating corresponding to the high-speed locking parts in the upper iron mold and the lower iron mold is designed to be thinned to 4 mm;
[0049] Step 3, designing a protrusion at the gate position of the high-speed locking part of the lower outer mold, and after the molding is completed, a pit is formed at the position of the high-speed locking part corresponding to the protrusion in the lower casting mold, and adding pure antimony powder in the pit according to 0.005-0.006% of the weight of the high-speed locking part, that is, 4.5g of pure antimony powder is placed in the pit;
[0050] Step 4, smelting molten iron according to the alloy composition of the air deflector bracket casting in the upper and lower molds, the weight percentage of the alloy composition is 0.3% copper and 0.28% manganese, and the molten iron is poured into the cavity formed by the upper and lower molds according to the performance requirements of the 20mm air deflector parts to obtain high-speed locking parts and air deflector bracket castings with balanced performance. The obtained air deflector bracket parts have a strength of 730-780MPa and an elongation of 10.5-11.5%; the high-speed locking parts have a strength of 690-715MPa and an elongation of 9.8-11%, both of which meet the performance requirements.
[0051] Embodiment 2: A support seat and a stable retaining frame
[0052] The above casting method is used to cast a support seat body and a stable retainer part, including the following steps:
[0053] Step 1: When designing the iron mold sand coating process, the upper outer mold, lower outer mold, upper iron mold and lower iron mold are arranged according to the size and parting scheme of the support seat body part and the stable retainer. The support seat body part has a wall thickness of 60-80mm and a weight of 90kg; the stable retainer has a wall thickness of 10-15mm and a weight of 8kg. The grade requirements for both parts are HT250.
[0054] Step 2, setting the iron mold sand coating of the stabilizing retainer to 8 mm; then the thickness of the iron mold sand coating corresponding to the position of the supporting seat body parts in the upper casting mold and the lower casting mold is designed to be thinned to 4 mm;
[0055] Step 3, designing a protrusion at the gate position of the support seat body part of the lower outer mold, and after the molding is completed, a pit is formed at the position of the support seat body part corresponding to the protrusion in the lower casting mold, and pure antimony powder is added into the pit according to 0.02-0.025% of the weight of the support seat body part, that is, 22.5g of pure antimony powder is placed in the pit;
[0056] Step 4, smelting molten iron according to the alloy composition of the stable cage casting in the casting mold, the alloy composition and weight percentage are 0.3-0.35% copper, 0.6-0.7% manganese and 0.15% chromium, and designed according to the performance requirements of the 15mm stable cage parts, pouring the molten iron in the cavity formed by the upper casting mold and the lower casting mold to obtain a support seat body part and a stable cage body casting with balanced performance, and cooling and solidifying. The strength of the obtained support seat body part is 235-260MPa, and the strength of the stable cage part is 255-285MPa, both of which meet the performance requirements.
Claims
1. A casting method for casting different castings with large wall thickness differences in common mold and balanced performance, characterized in that: The steps include: Step 1: Arrange the mold according to the size and parting scheme of thick and large parts and thin-walled parts, and draw the upper and lower outer molds, upper and lower iron molds; Step 2, reducing the thickness of the sand coating layer of the upper and lower iron molds corresponding to the thick and large casting positions in step 1; Step 3, designing a protrusion at the gate position of the thick casting of the lower outer mold in step 1, obtaining an upper mold and a lower mold after the molding is completed, forming a pit at the position corresponding to the protrusion of the thick casting of the lower mold, and placing pure antimony powder in the pit; Step 4, smelting molten iron according to the alloy composition of the thin-walled casting, pouring the molten iron into the cavity formed by the upper casting mold and the lower casting mold, to obtain thick and large castings and thin-walled castings with balanced performance.
2. The method according to claim 1, characterized in that: The wall thickness of the thick and large parts and the thin-walled parts described in step 1 differ by three to ten times.
3. The method according to claim 1, characterized in that: In step 2, the thickness of the iron mold sand coating layer is designed to be thinned to a thickness of 4 to 6 mm.
4. The method according to claim 1, characterized in that: If the thick and large parts and thin-walled parts in step 1 are made of ductile iron, the amount of pure antimony powder added in step 3 is 0.005-0.006% of the weight of the thick and large parts; if the thick and large parts and thin-walled parts in step 1 are made of gray iron, the amount of pure antimony powder added in step 3 is 0.02-0.025% of the weight of the thick and large parts; if the thick and large parts and thin-walled parts in step 1 are made of vermicular iron, the amount of pure antimony powder added in step 3 is 0.015-0.025% of the weight of the thick and large parts; the size of the pit is set according to the volume of the added antimony powder, and the antimony powder volume accumulation thickness is 2-3 mm or occupies 1 / 5-1 / 3 of the volume of the pit, and the protrusion is set to an arc shape.
5. Application of the method as claimed in claim 1 in the preparation of a shroud bracket and high-speed locking parts with a brand number of QT700-10.
6. The use according to claim 5, characterized in that: The alloy components of the deflector support are copper and manganese, and the weight percentages of copper and manganese in the molten iron are 0.3% and 0.28% respectively.
7. Application of the method as claimed in claim 1 in the preparation of support seat bodies and stabilizing cage parts with a grade of HT250.
8. The use according to claim 7, characterized in that: The alloy components of the stable retainer are copper, manganese and chromium, and the weight percentages of copper, manganese and chromium are 0.3-0.35%, 0.6-0.7% and 0.15% respectively.