High-strength gray cast iron diesel engine block without riser casting forming method

Abstract

The application provides a high-strength gray cast iron diesel engine body without riser casting forming method, and belongs to the casting technical field.The method is designed from the parting surface, pouring system, riser, cold iron, scale reduction and smelting process parameters; and comprises the following steps: selection of the parting surface: the diesel engine body adopts a horizontal casting type, the cylinder hole surface is located on the side surface, and the two-opening box casting mode is arranged on the crank hole; pouring system design: an open bottom pouring system with a filter is adopted; riser design: no riser is designed at the highest point of the pouring position of the diesel engine body, only air outlet fins are arranged on the two sides, and an air outlet rod is arranged at the middle large plane position; cold iron design: no cold iron is used at the position with uneven wall thickness of the diesel engine body; scale reduction design: the scale reduction is determined as 1.1%; and smelting process and parameters.The application has relatively high strength and hardness, can improve the shock resistance, wear resistance and heat dissipation performance, and can also reduce the production cost.

Description

Technical Field

[0001] This invention belongs to the field of casting technology, specifically relating to a riserless casting method for high-strength gray cast iron diesel engine blocks. Background Technology

[0002] The engine block is a key component of a diesel engine, primarily serving as a support structure. It houses hundreds of parts, including the crankshaft, connecting rods, cylinder head, and camshaft, making it one of the most critical and complex components in a diesel engine unit. It is typically manufactured using casting. The casting material is generally ordinary QT400-15 ductile iron. However, engine blocks made of ordinary QT400-15 ductile iron, especially in areas with thin walls and numerous hot spots, are prone to shrinkage defects during solidification. While a riser and chill process is commonly used to produce castings, this method suffers from inconsistent quality, high production costs, poor vibration damping, and poor heat dissipation.

[0003] With the development of high-quality products, the engine block, which primarily serves as a supporting base for diesel engines, must not only meet basic material strength and hardness requirements but also consider vibration damping and heat dissipation performance. However, the commonly used QT400-15 material for engine blocks has a high tendency for shrinkage porosity, making the casting process prone to defects such as shrinkage porosity and shrinkage cavities. Although QT400-15 material has relatively high strength, its vibration damping, wear resistance, and heat dissipation performance are not as good as those of HT300 material.

[0004] According to relevant scientific research, under the same conditions, the heat dissipation of flake graphite along its length is 100 times that along its width, while the graphite spheres in ductile iron can be considered to have their width direction as the entire axis. Therefore, using HT300 grade material to cast the engine block offers advantages in casting performance, wear resistance, and vibration damping, resulting in superior overall performance of the diesel engine. Thus, a method for manufacturing the diesel engine block using HT300 grade material needs to be designed. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a riser-free casting method for high-strength gray cast iron diesel engine blocks. The purpose of this invention is to design aspects such as the selection of the casting parting surface, the design of the gating system, the arrangement of chill removal, the control of shrinkage, and the parameters of the smelting composition. This allows for the stable production of HT300 grade engine blocks with controllable internal quality and qualified mechanical properties. These blocks have relatively high strength and hardness. Under the same power and load conditions, engine blocks made of this material can not only improve shock absorption, wear resistance, and heat dissipation performance, but also reduce production costs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A riserless casting method for high-strength gray cast iron diesel engine blocks is proposed. This method primarily addresses the cracking defect in HT300 diesel engine blocks. Taking a specific type of diesel engine block as an example, the casting process is designed from the aspects of parting surface, gating system, risers, chills, scaling, and melting process parameters. The specific steps include:

[0008] 1) Selection of parting surface: The diesel engine block adopts a horizontal casting method with the cylinder bore surface located on the side and the parting surface set on the crankshaft bore. This two-box casting method divides the diesel engine block casting sand box into a lower box and an upper box.

[0009] 2) Gating system design: An open bottom-pouring gating system with a filter is adopted. The open bottom-pouring gating system includes a sprue, a runner, a filter, and an ingate. The sprue is connected to the runner, the runner is connected to the filter, the filter is connected to the ingate, and the ingate is connected to the cavity.

[0010] 3) No riser design: No riser is designed at the highest point of the diesel engine block casting position. Air strips are arranged on both sides and air rods are arranged in the large flat area in the middle.

[0011] 4) No chill design: No chills are designed in the thick parts of the diesel engine block or in the parts with uneven wall thickness;

[0012] 5) Scale reduction design: The shrinkage tendency of the diesel engine block of HT300 cast iron is greater than that of ordinary ductile iron, so the scale reduction of the diesel engine block is determined to be 1.1%;

[0013] 6) Smelting process and parameters: In this method, the composition ratio of HT300 cast iron by weight is: 29% pig iron + 40% scrap steel + 30% recycled material + 1% carburizer; the alloy composition is controlled as follows: C: 2.9%-3.1%, Si: 1.7%-1.9%, Mn: 0.7%-0.9%, P < 0.1%, S: 0.06%-0.10%, Cu: 0.4%-0.5%, Cr: 0.2%-0.3%. A barium-containing inoculant is used, with an addition amount of 0.6%.

[0014] In step 2) above, the cross-sectional ratio of the open bottom-pouring system is sprue: sprue: ingate = 1:2.1:1.6.

[0015] In step 2) above, the sprue is made of a single Φ100mm ceramic tube, the gating system has a trapezoidal cross section of 80 / 90×100, and the ingate is made of a corresponding number of Φ30 ceramic tubes.

[0016] In step 2) above, the sprue serves as a flow-blocking section. Molten iron flows from the sprue to the runner, passes through a filter, and is dispersed and introduced from the lowest surface of the mold cavity. The pouring time is controlled at about 60-70 seconds, and the pouring temperature is 1360-1370℃.

[0017] In step 3) above, the air outlet plate has a size of 45×13×400mm, and the air outlet rod has a size of Φ20mm.

[0018] Advantages of this invention compared to existing technologies:

[0019] 1. For cast iron grade HT300 bodies, this invention has a strong self-feeding ability due to the precipitation of graphite and the accompanying phase transformation expansion during solidification. Therefore, the tendency of shrinkage cavities and porosity is small. Thus, a riser-free design is adopted at the highest point of the casting pouring position, and only venting plates and venting rods of a certain specification are set. Chills are not used in the thick parts of the casting, which can effectively eliminate the shrinkage defects of the casting. Under the premise of ensuring the strength and rigidity of the body, the vibration damping, wear resistance and heat dissipation of the body are improved, and the casting process is simplified.

[0020] 2. This scheme uses a relatively high pouring temperature of 1360-1370℃, combined with an open bottom pouring system with a filter, so that the pouring time is controlled at about 60-70 seconds, which can effectively reduce the generation of porosity and slag inclusion defects in castings, and the surface quality of castings is good.

[0021] 3. Compared to ordinary QT400-15 material bodies, HT300 material bodies are more prone to cracking. Therefore, by controlling the purity and chemical composition of the smelting raw materials, the material performance is guaranteed.

[0022] 4. The diesel engine block manufactured by this method, through on-site mechanical performance testing and processing verification, showed that the tensile strength of the single casting sample exceeded 330MPa, the average tensile strength of the main body reached 260MPa, and the hardness was 178HB. The internal and external quality met the design requirements of the diesel engine, making the overall operating performance of the diesel engine more excellent. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the parting surface of the diesel engine block in this invention;

[0024] Figure 2 This is a side view of the casting system of the diesel engine block in this invention;

[0025] Figure 3 This is a schematic diagram of the bottom surface of the casting system for the diesel engine block in this invention;

[0026] Figure 4 This is a diagram showing the arrangement of the exhaust plates and exhaust rods of the diesel engine body in this invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0029] Please see Figure 1-4 The embodiments of the present invention are described in detail below.

[0030] Example: A riserless casting method for high-strength gray cast iron diesel engine blocks. This method mainly addresses the defects such as cracking that easily occur in HT300 diesel engine blocks. Taking a certain type of diesel engine block as an example, the block's external dimensions are 2638×968×1274mm, the blank weight is 4970Kg, the molten iron weight is 6100Kg, the main wall thickness is 15mm, and the maximum wall thickness is 108mm. The casting design is carried out from the aspects of parting surface, gating system, risers, chills, shrinkage, and melting process parameters. Specifically, it includes the following steps:

[0031] 1) Selection of parting surface: The diesel engine block 1 adopts a horizontal casting method, with the cylinder bore surface located on the side. This not only simplifies the molding and assembly process but also ensures the accuracy and completeness of the overall dimensions and side shape of the engine block. The parting surface 2 is set at the crankshaft bore in a two-box casting method. (See [reference needed]). Figure 1 As shown, the casting sand box for the diesel engine block 1 is divided into a lower box 3 and an upper box 4. Most of the castings are located in the lower box, which helps to ensure the dimensions and internal quality.

[0032] 2) Gating system design: An open bottom gating system 5 with a filter is adopted. The open bottom gating system 5 includes a sprue 6, a runner 7, a filter 8 and an ingate 9. The sprue 6 is connected to the runner 7, the runner 7 is connected to the filter 8, the filter 8 is connected to the ingate 9, and the ingate 9 is connected to the cavity.

[0033] Preferably, the cross-sectional ratio of the open bottom-pouring system 5 is sprue: gutter: ingate = 1:2.1:1.6.

[0034] For the diesel engine in this embodiment, the sprue 6 is made of a single Φ100mm ceramic tube, the runner 7 has a trapezoidal cross-section of 80 / 90mm × 100mm, and the ingate 9 is made of 18 Φ30mm ceramic tubes. (See reference...) Figure 2 and 3 As shown, the sprue 6 serves as a flow-blocking section. Molten iron flows from the sprue 6 to the grate 7, passes through the filter 8, and is dispersed and introduced from the lowest surface of the mold cavity. The pouring time is controlled at approximately 60-70 seconds, and the pouring temperature is 1360-1370℃. The molten iron is introduced from the lowest point of the mold cavity, and combined with the open ingate, the molten iron level rises smoothly, which helps reduce porosity and slag inclusions caused by turbulent flow.

[0035] In this method, a relatively high pouring temperature of 1360-1370℃, combined with an open bottom pouring system with a filter, allows the pouring time to be controlled at around 60-70 seconds, which can effectively reduce the generation of porosity and inclusion defects in castings, resulting in good surface quality of castings.

[0036] 3) Riser-free design: Due to the change in the material of the engine body, the liquid and solid solidification shrinkage mode has changed. The upper wall thickness of the engine body is relatively thin and does not require a large amount of liquid to replenish the shrinkage. It only needs to be able to release gas and solidify quickly. Therefore, no riser is designed at the highest point of the casting position of the diesel engine body 1. Only gas venting plates 10 are arranged on both sides and gas venting rods 11 are arranged in the middle large flat position.

[0037] For the diesel engine block in this embodiment, the exhaust vanes 10 are 18 in number, each measuring 45×13×400mm, and the exhaust rods 11 are Φ20mm in size. (See also...) Figure 4 As shown.

[0038] 4) No chill design: No chills are designed in the parts of the diesel engine block with a wall thickness of 1 or in the parts with uneven wall thickness.

[0039] Previously, numerous chills were placed in areas with thick or uneven wall thickness to balance the solidification rate of these thicker sections. This new method eliminates the need for traditional chills, significantly reducing the production costs of raw materials required for chill manufacturing. Furthermore, the absence of chills improves both the surface quality of the castings and production efficiency.

[0040] For cast iron grade HT300 castings, the precipitation of graphite during solidification, accompanied by phase transformation and expansion, results in a strong self-feeding ability, thus minimizing the tendency for shrinkage cavities and porosity. A riser-free design must be adopted at the highest point of the casting pouring position, with only venting plates and venting rods of a certain size installed. Chills should not be used in thick sections of the casting to effectively eliminate shrinkage defects.

[0041] 5) Dimensioning design: The casting manual states that the shrinkage rate of cast iron ranges from 0.8% to 1.3%. Based on the wall thickness, shape, and structure of the casting, and considering that the shrinkage tendency of the diesel engine block 1 made of HT300 cast iron is greater than that of ordinary ductile iron, the shrinkage of the diesel engine block 1 was determined to be 1.1%. Subsequent inspection of the casting dimensions showed that the 1.1% shrinkage was appropriate.

[0042] 6) Smelting Process and Parameters: Unlike ductile iron, gray cast iron undergoes sequential solidification, resulting in good casting performance and less susceptibility to shrinkage defects. The challenge lies in achieving high strength. Therefore, designing a reasonable batching method and alloy composition ratio is crucial for achieving high strength. In this method, the batching method for HT300 cast iron is: 29% pig iron + 40% scrap steel + 30% recycled material + 1% carburizer; the alloy composition is controlled as follows: C: 2.9%-3.1%, Si: 1.7%-1.9%, Mn: 0.7%-0.9%, P < 0.1%, S: 0.06%-0.10%, Cu: 0.4%-0.5%, Cr: 0.2%-0.3%. A barium-containing inoculant is used, added at 0.6%.

[0043] This invention addresses aspects such as the selection of casting parting surfaces, gating system design, chill removal arrangement, scaling control, and smelting composition parameters. It enables the stable production of HT300 grade machine bodies with controllable internal quality and qualified mechanical properties. These machine bodies possess relatively high strength and hardness. Under the same power and load conditions, machine bodies made of this material not only improve shock absorption, wear resistance, and heat dissipation performance but also reduce production costs.

[0044] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0045] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for casting a high-strength gray cast iron diesel engine block without risers, characterized in that: This method primarily addresses the cracking issue inherent in the HT300 diesel engine block, focusing on casting design aspects such as the parting line, gating system, risers, chills, shrinkage, and melting process parameters. Specifically, it includes the following steps: 1) Selection of parting surface: The diesel engine body (1) adopts horizontal casting, the cylinder bore surface is located on the side, and the parting surface (2) is set on the crankshaft hole. The two-box casting method divides the casting sand box of the diesel engine body (1) into the lower box (3) and the upper box (4). 2) Gating system design: An open bottom gating system (5) with a filter is adopted. The open bottom gating system (5) includes a sprue (6), a runner (7), a filter (8) and an ingate (9). The sprue (6) is connected to the runner (7), the runner (7) is connected to the filter (8), the filter (8) is connected to the ingate (9), and the ingate (9) is connected to the cavity. 3) No riser design: No riser is designed at the highest point of the casting position of the diesel engine body (1), and gas strips (10) are arranged on both sides, and gas rods (11) are arranged in the middle large plane position; 4) No chill design: No chills are designed in the parts of the diesel engine body (1) where the wall thickness is thick or where the wall thickness is uneven; 5) Scale reduction design: The shrinkage tendency of the diesel engine block (1) made of HT300 cast iron is greater than that of ordinary ductile iron. Therefore, the scale reduction of the diesel engine block (1) is determined to be 1.1%. 6) Smelting process and parameters: In this method, the composition ratio of HT300 cast iron by weight is: 29% pig iron + 40% scrap steel + 30% recycled material + 1% carbon raiser; the alloy composition is controlled as follows: C: 2.9%-3.1%, Si: 1.7%-1.9%, Mn: 0.7%-0.9%, P < 0.1%, S: 0.06%-0.10%, Cu: 0.4%-0.5%, Cr: 0.2%-0.3%; a barium-containing inoculant is used, with an addition amount of 0.6%.

2. The method for riserless casting of high-strength gray cast iron diesel engine block according to claim 1, characterized in that: In step 2) above, the cross-sectional ratio of the open bottom-pouring system (5) is sprue: sprue: ingate = 1:2.1:1.

6.

3. The method for riserless casting of high-strength gray cast iron diesel engine block according to claim 2, characterized in that: In step 2) above, the sprue (6) is made of a Φ100mm ceramic tube, the gating system (7) is a trapezoidal cross section of 80 / 90mm×100mm, and the ingate (9) is made of a corresponding number of Φ30mm ceramic tubes.

4. The method for riserless casting of high-strength gray cast iron diesel engine block according to claim 3, characterized in that: In step 2) above, the sprue (6) serves as a flow-blocking section. Molten iron flows from the sprue (6) to the grate (7), passes through the filter (8), and is dispersed and introduced from the lowest surface of the cavity. The pouring time is controlled at about 60-70 seconds, and the pouring temperature is 1360-1370℃.

5. The method for riserless casting of high-strength gray cast iron diesel engine block according to claim 1, characterized in that: In step 3) above, the air outlet plate (10) adopts a specification of 45×13×400mm, and the air outlet rod (11) adopts a specification of Φ20mm.

Images