CN107723650A - A kind of casting method of aluminum-iron bimetal for engine block - Google Patents

Abstract

A casting method of aluminum-iron bimetal for engine cylinder belongs to the field of alloy preparation technology, including: preparing vermicular cast iron, decontamination and rust removal of cast iron, surface modification, aluminum alloy refining and chromium addition, mold brushing heat preservation coating, hot dip plating, and casting. Hot dip aluminum plating not only forms an intermediate phase layer on the surface of cast iron, but also adheres to a layer of incompletely solidified aluminum alloy layer on its surface, which is easy to fuse with the cast aluminum alloy during the casting process, forming a complete metallurgical bond, and improving the interface bonding ability and performance of the alloy.

Description

A kind of casting method of aluminum-iron bimetal for engine block

technical field

The invention belongs to the technical field of alloy preparation, and in particular relates to an aluminum-iron bimetallic casting method for engine cylinder blocks.

Background technique

Because composite materials can combine the advantages of different materials, they are playing an increasingly important role in various fields around the world; research on composite materials has also attracted the attention of more and more experts and scholars. The bimetallic composite casting material, because it is synthesized by casting method, has a simple process and low cost, and has great application prospects. However, the contact time of the two metals is short and the cooling speed is fast during the pouring process, which seriously affects the combination of the two. It has also become a bottleneck restricting the production and application of bimetallic composite casting materials. Therefore, how to make bimetallic castings have good combination and performance remains to be further studied.

Contents of the invention

According to the problems existing in the prior art, the present invention provides an aluminum-iron bimetallic casting method for an engine block, aiming at improving the interfacial bonding ability and performance of the alloy.

The present invention adopts following technical scheme:

A method for casting an aluminum-iron bimetallic engine block, comprising the following steps:

Step 1: The cast iron is smelted in a GGW-0.012 intermediate frequency coreless induction furnace, and the vermicular treatment adopts the flushing method, adding 0.6% by weight of vermicular agent and 0.33% by weight of inoculant, and using a plug-in temperature measuring gun Temperature measurement, tapping temperature 1560°C, pouring temperature 1400°C, vermicular graphite cast iron was obtained;

Step 2: Grind the vermicular graphite cast iron with sandpaper to remove the surface oxide layer, place the cast iron in an aqueous solution of sodium oxide with a mass concentration of 15%, soak it at 50°C for 20 minutes, and perform degreasing treatment, and then use a mass fraction of 5% Use hydrochloric acid to pickle and remove rust on the cast iron surface, then dry it and put it in a dry environment for use;

Step 3: Select K ₂ ZrF ₆ aqueous solution with a mass concentration of 4% as the surface modifier, immerse the cast iron in the surface modification, control the immersion temperature at 80-90°C, and control the time at more than 10 minutes, then take it out at a uniform speed, and Dry at 150±5°C, and preheat the cast iron at 200°C-300°C and keep it warm. The preheating temperature is 200°C-300°C;

Step 4: Use a 12KW crucible resistance furnace to melt aluminum alloy at a melting temperature of 700°C ± 20°C, refine with 0.6% by weight of C ₂ Cl ₆ , and after standing for 20 minutes, add 2% by weight to the aluminum alloy melt Chromium, stir evenly with a graphite stirring rod, and keep warm at 700°C;

Step 5: Brush the casting insulation paint on the mold before casting, and preheat the mold after using the paint to 500°C in advance;

Step 6: Dip the cast iron into the aluminum alloy melt to start the hot-dip coating process. The hot-dip coating time is 15 minutes. The hot-dipped cast iron is quickly taken out and fixed in the mold, and the casting is completed within 20 seconds;

Step 7: The cast sample is solution treated at 500°C for 4 hours, and then aged at 200°C for 6 hours.

Preferably, the sandpaper described in step 2 is 400 mesh SiC sandpaper.

Preferably, the casting speed described in step six is 1.5kg/s.

Preferably, the aluminum alloy contains the following components by weight percentage: Si6.5%-7.5%, Mg0.25%-0.45%, Ti0.08%-0.2%, Mn0%-0.1%, and the balance is Al.

Preferably, the cast iron contains the following chemical components in weight percentage: C3.4%-3.6%, Si2.4%-2.6%, Mn0.3%-0.6%, S0%-0.02%, P0%-0.07% , The balance is Fe.

Preferably, the creeping agent is FeSiMg5RE5 creeping agent.

Preferably, the inoculant is Si-Ba inoculant.

The beneficial effects of the present invention are:

1) There are two purposes for the treatment of hot-dip aluminum plating on the surface of cast iron. The first is to preheat the base metal, and the second is to improve the wettability of the pretreated cast iron. Such an operation is because generally when the surface of the core material melts, it is easier to achieve metallurgical bonding between the core material and the molten metal. Because the core material is preheated and the temperature is higher, it can provide more energy for the metallurgical bonding of the interface: first, preheating reduces its chilling effect on the molten metal and maintains the temperature of the overall material; second, The higher the temperature of the core material, the higher the energy of the atoms, so the ability to get rid of the constraints of metal bonds is enhanced, the ability of atomic diffusion is greatly enhanced, the width of the diffusion layer increases, and the interface bonding strength is also higher. Secondly, the high temperature environment provided by hot-dip aluminum plating can promote the diffusion of atoms, which is more likely to trigger the metallurgical reaction between aluminum and iron and make it form an intermediate phase layer (ie, metallurgical bonding layer) before casting; hot-dip aluminum plating not only makes A mesophase layer is formed on the surface of the cast iron, and a layer of incompletely solidified aluminum alloy is also adhered to the surface, which is easily fused with the cast aluminum alloy during the casting process to form a complete metallurgical bond. When hot-dip plating for 15 minutes, the diffusion is the most sufficient, and the transition zone formed is the widest, about 50um, which effectively improves the interface bonding ability and performance of the alloy.

2) The thermal conductivity of the mold is good, and the temperature drops quickly after casting, so the paint with better heat preservation effect is brushed on the mold before casting.

3) After the addition of chromium, the diffusion level of atoms is obviously promoted, and the transition zone is obviously wider than that of the sample without alloying elements, and the atoms have undergone long-distance diffusion in the region together with other elements in the form of intermetallic compounds or solid solutions. form precipitated.

4) Solution treatment and aging treatment can obviously promote the diffusion of atoms, and the transition zone is obviously widened.

5) The 4% K ₂ ZrF ₆ aqueous solution inhibits the surface oxidation of cast iron and purifies the oxides attached to the surface. After drying, a dense film is formed on the surface, which effectively protects the surface of the substrate. During pouring, as the molten aluminum enters the mold, the protective film on the surface of the cast iron gradually decomposes and exposes the more active substrate surface, which greatly improves the wettability of the molten aluminum and improves the interface properties of the casting.

6) Since vermicular graphite cast iron has the properties of both nodular cast iron and gray cast iron, it has unique uses and is widely used in steel ingot molds, automobile engines, exhaust pipes, glass molds, diesel engine cylinder heads, brake parts, etc. Have good effect. The section sensitivity of vermicular graphite cast iron is much smaller than that of ordinary gray cast iron, so the mechanical properties of its thick and large sections are still relatively uniform. In addition, its wear resistance is better than inoculated cast iron and high phosphorus wear-resistant cast iron. The thermal conductivity and thermal fatigue resistance are much higher than that of ductile iron, which is the outstanding advantage of vermicular graphite iron. Both growth resistance and oxidation resistance are higher than other cast irons. The vermicular rate of the vermicular graphite cast iron prepared by the invention is higher than 85%.

detailed description

The technical solutions in the present invention are clearly and completely described below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

A method for casting an aluminum-iron bimetallic engine block, comprising the following steps:

Step 1: The cast iron is smelted in a GGW-0.012 intermediate frequency coreless induction furnace, and the vermicular treatment adopts the flushing method, adding 0.6% by weight of vermicular agent and 0.33% by weight of inoculant, and using a plug-in temperature measuring gun Temperature measurement, tapping temperature 1560°C, pouring temperature 1400°C, vermicular graphite cast iron was obtained;

Step 2: Grind the vermicular graphite cast iron with sandpaper to remove the surface oxide layer, place the cast iron in an aqueous solution of sodium oxide with a mass concentration of 15%, soak it at 50°C for 20 minutes, and perform degreasing treatment, and then use a mass fraction of 5% Use hydrochloric acid to pickle and remove rust on the cast iron surface, then dry it and put it in a dry environment for use;

Step 3: Select K ₂ ZrF ₆ aqueous solution with a mass concentration of 4% as the surface modifier, immerse the cast iron in the surface modification, control the immersion temperature at 80-90°C, and control the time at more than 10 minutes, then take it out at a uniform speed, and Dry at 150±5°C, and preheat the cast iron at 200°C-300°C and keep it warm. The preheating temperature is 200°C-300°C;

Step 4: Use a 12KW crucible resistance furnace to melt aluminum alloy at a melting temperature of 700°C ± 20°C, refine with 0.6% by weight of C ₂ Cl ₆ , and after standing for 20 minutes, add 2% by weight to the aluminum alloy melt Chromium, stir evenly with a graphite stirring rod, and keep warm at 700°C;

Step 5: Brush the casting insulation paint on the mold before casting, and preheat the mold after using the paint to 500°C in advance;

Step 6: Dip the cast iron into the aluminum alloy melt to start the hot-dip coating process. The hot-dip coating time is 15 minutes. The hot-dipped cast iron is quickly taken out and fixed in the mold, and the casting is completed within 20 seconds;

Step 7: The cast sample is solution treated at 500°C for 4 hours, and then aged at 200°C for 6 hours.

The sandpaper described in step 2 is 400 mesh SiC sandpaper.

The casting speed described in step six is 1.5kg/s.

The aluminum alloy contains the following components by weight percentage: Si6.5%-7.5%, Mg0.25%-0.45%, Ti0.08%-0.2%, Mn0%-0.1%, and the balance is Al.

The cast iron contains the following chemical components in weight percentage: C3.4%-3.6%, Si2.4%-2.6%, Mn0.3%-0.6%, S0%-0.02%, P0%-0.07%, balance For Fe.

The described vermicular agent is FeSiMg5RE5 vermicular agent.

The inoculant is Si-Ba inoculant.

Claims (7)

1. a casting method of aluminum-iron bimetal for engine block, is characterized in that, comprises the following steps: Step 1: The cast iron is smelted in a GGW-0.012 intermediate frequency coreless induction furnace, and the vermicular treatment adopts the flushing method, adding 0.6% by weight of vermicular agent and 0.33% by weight of inoculant, and using a plug-in temperature measuring gun Temperature measurement, tapping temperature 1560°C, pouring temperature 1400°C, vermicular graphite cast iron was obtained; Step 2: Grind the vermicular graphite cast iron with sandpaper to remove the surface oxide layer, place the cast iron in an aqueous solution of sodium oxide with a mass concentration of 15%, soak it at 50°C for 20 minutes, and perform degreasing treatment, and then use a mass fraction of 5% Use hydrochloric acid to pickle and remove rust on the cast iron surface, then dry it and put it in a dry environment for use; Step 3: Select K ₂ ZrF ₆ aqueous solution with a mass concentration of 4% as the surface modifier, immerse the cast iron in the surface modification, control the immersion temperature at 80-90°C, and control the time at more than 10 minutes, then take it out at a uniform speed, and Dry at 150±5°C, and preheat the cast iron at 200°C-300°C and keep it warm. The preheating temperature is 200°C-300°C; Step 4: Use a 12KW crucible resistance furnace to melt aluminum alloy at a melting temperature of 700°C ± 20°C, refine with 0.6% by weight of C ₂ Cl ₆ , and after standing for 20 minutes, add 2% by weight to the aluminum alloy melt Chromium, stir evenly with a graphite stirring rod, and keep warm at 700°C; Step 5: Brush the casting insulation paint on the mold before casting, and preheat the mold after using the paint to 500°C in advance; Step 6: Dip the cast iron into the aluminum alloy melt to start the hot-dip coating process. The hot-dip coating time is 15 minutes. The hot-dipped cast iron is quickly taken out and fixed in the mold, and the casting is completed within 20 seconds; Step 7: The cast sample is solution treated at 500°C for 4 hours, and then aged at 200°C for 6 hours. 2. A method for casting an aluminum-iron bimetallic engine block according to claim 1, characterized in that: the sandpaper described in step 2 is 400 mesh SiC sandpaper. 3. The casting method of aluminum-iron bimetallic for engine block according to claim 1, characterized in that: the casting speed in step 6 is 1.5kg/s. 4. A method for casting an aluminum-iron bimetallic engine block according to claim 1, wherein the aluminum alloy contains the following components in weight percent: Si6.5%-7.5%, Mg0.25 %-0.45%, Ti0.08%-0.2%, Mn0%-0.1%, and the balance is Al. 5. The casting method of an aluminum-iron bimetal for an engine block according to claim 1, wherein said cast iron comprises the following chemical components in weight percent: C3.4%-3.6%, Si2.4 %-2.6%, Mn0.3%-0.6%, S0%-0.02%, P0%-0.07%, and the balance is Fe. 6. A method for casting an aluminum-iron bimetallic engine block according to claim 1, characterized in that: said vermicular agent is FeSiMg5RE5 vermicular agent. 7. The casting method of an aluminum-iron bimetallic engine block according to claim 1, characterized in that: said inoculant is a Si-Ba inoculant.