CN112059105B - Coating for thoroughly eliminating defects of reaction layer on surface of ductile iron piece - Google Patents
Coating for thoroughly eliminating defects of reaction layer on surface of ductile iron piece Download PDFInfo
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- CN112059105B CN112059105B CN202010990336.2A CN202010990336A CN112059105B CN 112059105 B CN112059105 B CN 112059105B CN 202010990336 A CN202010990336 A CN 202010990336A CN 112059105 B CN112059105 B CN 112059105B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/20—Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor
Abstract
The invention discloses a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 20-30% of zircon powder, 30-40% of spheroidized mixture, 2-3% of lithium bentonite, 2-3% of thermosetting phenolic resin, 2-4% of auxiliary agent and 25-30% of ethanol, wherein the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the inoculant accounts for 40-60% of the nodulizer by weight. The invention also provides a method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron piece, which comprises the steps of firstly coating the surface of the resin sand mold with the coating once, then brushing the coating once again, and then putting the resin sand mold into a surface drying furnace for drying and then pouring in a box. The invention can neutralize, absorb and shield sulfur elements in resin sand mold and sulfur-containing gas diffused into molten iron, has good supplementary spheroidizing effect on the molten iron, prevents the surface of the ductile iron from sulfurizing defect, thoroughly eliminates the defect of the surface reaction layer of the ductile iron produced by furan resin sand, and improves the surface quality of the ductile iron.
Description
Technical Field
The invention belongs to the technical field of casting coatings, and particularly relates to a coating and a method for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron piece.
Background
Through the development of casting technology for many years, the technology of furan resin sand molding technology used in the casting industry at home and abroad is mature and is most widely applied. The furan resin sand mold process principle is as follows: adding furan resin and a curing agent into the molding sand, uniformly stirring, and reacting the resin and the curing agent to harden the sand mold so as to meet the strength requirement of pouring molten iron. The curing agent is acid liquid, the most economical and best curing agent is sulfonic acid curing agent, the sulfonic acid contains sulfur, and after high-temperature molten iron is poured into the sand mold, the sulfur in the sand (sulfur brought by the curing agent) forms S0 under the action of high temperature2Entering into the surface iron liquid of the cavity S02Reacting with magnesium (Mg) in molten iron: mg + S02And the reaction result is that the effective content of magnesium element in the molten iron on the surface layer of the casting is insufficient, graphite is not spheroidized enough, so that a flaky graphite reaction layer is generated on the surface layer of the ductile iron, and the spheroidization of the surface layer of the casting is declined and even becomes grey cast iron.
Although the furan resin sand molding process is simple and convenient, the cost is low, but the defect of sulfurization or reaction layer which is difficult to overcome exists, especially when the furan resin sand is used for producing the nodular cast iron, the lower surface of the nodular cast iron with thick wall thickness or large heat node can generate the sulfurization defect, namely, the sulfur in the sand mold diffuses into the surface layer of the casting to cause 1-5mm spheroidization recession of the surface layer of the nodular cast iron, and even becomes the flake graphite of grey cast iron, which is also called as the defect of reaction layer or sulfurization. At present, most of domestic casting enterprises do not pay much attention to the defect of the reaction layer existing on the ductile iron part when producing the common ductile iron part, because the common casting does not have obvious symptoms when in use, the internal structure of the material is still compact, and the defect of the surface layer has little influence on the use effect. However, some high-end nodular iron castings and outlet nodular iron castings accepted by our company require measures to be taken to eliminate the defects of the surface reaction layer of the high-end nodular iron castings and control the surface reaction layer of the castings to be less than or equal to 0.30 mm.
Therefore, the most advanced casting coating for preventing sulfur seepage and reaction at home and abroad, such as FOSECO zircon powder shielding type coating in Fushike, OA in Europe or Guangzhou King magnesia powder absorbing type coating and other special shielding type-absorbing type coatings, are poor in using effect; in addition, the adoption of a relatively expensive low-sulfur curing agent reduces the sulfurization content, reduces the thickness of a formed flaky graphite reaction layer, but fundamentally does not solve the defects of the reaction layer and cannot meet the production quality requirement of high-end safety ductile iron pieces.
The Chinese invention with application number of 201510841691.2 has the patent name of 'a coating and a method for improving flaky graphite of an ingate of an austenitic ductile iron piece'; the invention relates to a process for reducing the thickness of high-nickel austenite ductile iron special-shaped graphite, which has the patent name of' 201810523372.0 application, and the invention mainly shields sulfur-containing gas by zircon powder coating, so that the sulfur-containing gas is difficult to enter molten metal through a coating layer, and a flaky graphite reaction layer is prevented from appearing on the surface of a casting; the invention patent with the application number of 201610681533.X is named as "sulphur-seepage-preventing coating for the surface of a wind power ductile iron element produced by furan resin sand", and the invention point is that magnesium oxide in the coating is mainly used for absorbing sulphur from a sand mold, so that the sulphur seepage content and the thickness of flake graphite of a reaction layer are reduced, but the practical effects of the three shielding and absorbing coating patents cannot meet the stable quality requirement of the reaction layer of a high-end safety ductile iron element of less than or equal to 0.30mm, and therefore, a coating and a method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron element need to be researched.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides the coating and the method for thoroughly eliminating the defects of the surface reaction layer of the ductile iron, which have the functions of neutralizing, absorbing and shielding sulfur elements in a resin sand mould and sulfur-containing gas diffused into molten iron, supplement the molten iron with a spheroidizing function, ensure the effective spheroidization of the molten iron, prevent flaky graphite from appearing on the surface of the ductile iron, thoroughly eliminate the defects of the surface reaction layer of the ductile iron produced by furan resin sand, and greatly improve the surface quality and the spheroidization grade of the ductile iron.
The technical scheme adopted by the invention is as follows:
the coating for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron piece comprises the following components in percentage by weight: 20-30% of zircon powder, 30-40% of spheroidized mixture, 2-3% of lithium bentonite, 2-3% of thermosetting phenolic resin, 2-4% of auxiliary agent and 25-30% of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 40-60%; the granularity of the nodulizer and the inoculant is 50-140 meshes; the auxiliary agent is polyvinyl butyral 0.5-1.0%, iron oxide red 2-5%, and defoaming agent 0.3-0.5%.
Further, the particle size of the zircon powder is 200-300 meshes.
Further, the granularity of the lithium bentonite is 300-400 meshes.
Further, the particle size of the iron oxide red is 200-300 meshes.
Further, the nodulizer is rare earth magnesium silicon iron alloy, and the inoculant is low-barium silicon iron alloy.
A method for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) the prepared flow coating paint is subjected to flow coating of resin sand for one time, and ignition and drying are carried out; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
Furthermore, the flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
Further, after the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree specific gravity meter, so that the baume degree of the flow coating paint is ensured to be 45-55, and the baume degree of the brush coating paint is ensured to be 50-60.
Further, the thickness of the dried resin sand mold surface coating layer is 0.6-1.2 mm.
Further, the natural gas passing-through drying furnace is set at the temperature of 120 ℃ and 150 ℃ for drying the resin sand mold, and the drying time is 20-30 minutes.
Compared with the prior art, the invention has the beneficial effects that:
1. the spheroidizing mixture in the coating contains a spheroidizing agent and an inoculant, wherein the spheroidizing agent can neutralize and absorb sulfur elements in a resin sand mold and sulfur-containing gas diffused into molten iron, has a supplementary spheroidizing effect on the molten iron, increases the effective magnesium content in the molten iron, ensures the molten iron to be effectively spheroidized, prevents flaky graphite from appearing on the surface of a ductile iron piece, and thoroughly eliminates the defect of a reaction layer on the surface of the ductile iron piece produced by furan resin sand; the inoculant has the inoculation effect on iron liquid for supplementing spheroidization, and cementite and white cast defects on the surface of the nodular iron piece are prevented, so that the nodulizer in the surface coating of the nodular iron piece is matched with the inoculant, the granularity of the nodulizer and the inoculant is controlled to be proper, the spheroidization effect and the inoculation effect on the surface layer of the nodular iron piece are ensured, and the surface quality and the spheroidization grade of the nodular iron piece are greatly improved.
2. The zircon powder is a good coating refractory aggregate, has good thermochemical stability, does not react with metal oxides, and has good solid-phase sintering performance; the zircon powder has good suspension stability in the coating, excellent thixotropy and rheological property, high coating strength, stronger chilling capability on a casting, good sand adhesion resistance, capability of effectively preventing the surface defect of the casting, smooth and easy cleaning of the surface of the casting, better thermal conductivity and convenience for heat conduction of the casting during pouring, and can quickly cool the surface of the casting, isolate the surface of the casting from air, shield volatile reducing gas and sulfur-containing gas in resin and prevent the surface of a ductile iron casting from generating a flaky graphite layer. The granularity of the lithium bentonite is 300-400 meshes, and the lithium bentonite is dispersed in an alcohol-based solution to play a role of a suspending agent, so that other components of the coating can be uniformly dispersed in the coating, and the coating is not precipitated when in use, thereby improving the stability and the brushing property of the coating.
3. The auxiliary agent in the coating improves the coating property, wettability and sintering property of the coating, wherein the polyvinyl butyral (PVB) has good thickening and seepage-proofing effects, and improves the coating property, high-temperature sand-bonding resistance and coating strength of the coating; the added defoaming agent reduces the surface tension of the coating, has strong defoaming and foam inhibition and improves the wettability of the coating; the iron oxide red is doped, so that the sintering stripping performance of the coating is improved, the surface of a casting is smooth, and the defects of air holes and sand sticking of the casting are avoided.
4. The coating disclosed by the invention is good in stability, suspension property, caking property and rheological property, good in flow coating and brush coating effects on resin sand molds, capable of being well attached to the surfaces of the sand molds and capable of controlling the thickness of the attached coating; and (3) carrying out flow coating and brush coating on the sand mould twice, and fully drying the sand mould through a surface drying furnace, so that the thickness and the strength of the coating of the sand mould are ensured, and the surface spheroidization quality of the casting is ensured.
5. The coating is not only suitable for furan resin sand molds and sand cores, but also suitable for phenolic resin sand shell molds and shell cores of high-nickel ductile iron, and thoroughly eliminates the defects of surface reaction layers of ductile iron parts produced by the furan resin sand molds and the sand cores; the thickness of the flake graphite on the surface of the nickelic ductile iron piece produced by the phenolic resin sand shell mould, the shell core and the shell green sand can be controlled to be zero, so that the surface quality and the spheroidization grade of the nickelic ductile iron piece are greatly improved.
Detailed Description
The present invention will be further described with reference to the following examples, which are carried out on the premise of the technical scheme of the present invention and give detailed embodiments and specific operation procedures, but the scope of the present invention is not limited to the following examples.
Example one
The embodiment provides a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 20% of zircon powder, 30% of spheroidized mixture, 2% of lithium bentonite, 2% of thermosetting phenolic resin, 3% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 50%; the granularity of the nodulizer and the inoculant is 50-100 meshes; the auxiliary agent comprises 0.5 percent of polyvinyl butyral, 2.5 percent of iron oxide red and 0.5 percent of defoaming agent.
The particle size of the zircon powder is 250 meshes.
The granularity of the lithium bentonite is 350 meshes.
The granularity of the iron oxide red is 250 meshes.
The nodulizer is 2-6 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg5.5-7.0, RE2.0-2.9, Ca2.0-3.0, Al less than or equal to 1.2 and the balance of iron.
The inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: si70-76, Ca1.0-2.0, Ba1.0-3.0, Al1.0-2.0, and the balance of iron.
The method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
The flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
After the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree proportion instrument, the baume degree of the flow coating paint is ensured to be 49, and the baume degree of the brush coating paint is ensured to be 54.
The thickness of the dried resin sand mold surface coating layer is 0.6 mm.
The natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
Example two
The embodiment provides a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 20% of zircon powder, 35% of spheroidized mixture, 2.5% of lithium bentonite, 2.5% of thermosetting phenolic resin, 3% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 60%; the granularity of the nodulizer and the inoculant is 50-100 meshes; the auxiliary agent comprises 0.5 percent of polyvinyl butyral, 2.5 percent of iron oxide red and 0.5 percent of defoaming agent.
The particle size of the zircon powder is 250 meshes.
The granularity of the lithium bentonite is 350 meshes.
The granularity of the iron oxide red is 250 meshes.
The nodulizer is 2-6 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg5.5-7.0, RE2.0-2.9, Ca2.0-3.0, Al less than or equal to 1.2 and the balance of iron.
The inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: si70-76, Ca1.0-2.0, Ba1.0-3.0, Al1.0-2.0, and the balance of iron.
The method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
The flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
After the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree proportion instrument, the baume degree of the flow coating is ensured to be 50, and the baume degree of the brush coating is ensured to be 55.
The thickness of the dried resin sand mold surface coating layer is 0.8 mm.
The natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
EXAMPLE III
The embodiment provides a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 25% of zircon powder, 30% of spheroidized mixture, 2.5% of lithium bentonite, 2.5% of thermosetting phenolic resin, 3% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 40%; the granularity of the nodulizer and the inoculant is 70-140 meshes; the auxiliary agent comprises 0.5 percent of polyvinyl butyral, 2.5 percent of iron oxide red and 0.5 percent of defoaming agent.
The particle size of the zircon powder is 250 meshes.
The granularity of the lithium bentonite is 350 meshes.
The granularity of the iron oxide red is 250 meshes.
The nodulizer is 2-6 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg5.5-7.0, RE2.0-2.9, Ca2.0-3.0, Al less than or equal to 1.2 and the balance of iron.
The inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: si70-76, Ca1.0-2.0, Ba1.0-3.0, Al1.0-2.0, and the balance of iron.
The method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
The flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
After the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree proportion instrument, so that the baume degree of the flow coating is ensured to be 51, and the baume degree of the brush coating is ensured to be 56.
The thickness of the dried resin sand mold surface coating layer is 1.0 mm.
The natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
Example four
The embodiment provides a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 30% of zircon powder, 30% of spheroidized mixture, 3% of lithium bentonite, 2% of thermosetting phenolic resin, 3% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 50%; the granularity of the nodulizer and the inoculant is 50-100 meshes; the auxiliary agent comprises 0.5 percent of polyvinyl butyral, 2.5 percent of iron oxide red and 0.5 percent of defoaming agent.
The particle size of the zircon powder is 250 meshes.
The granularity of the lithium bentonite is 350 meshes.
The granularity of the iron oxide red is 250 meshes.
The nodulizer is 2-6 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg5.5-7.0, RE2.0-2.9, Ca2.0-3.0, Al less than or equal to 1.2 and the balance of iron.
The inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: si70-76, Ca1.0-2.0, Ba1.0-3.0, Al1.0-2.0, and the balance of iron.
The method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
The flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
After the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree proportion instrument, the baume degree of the flow coating paint is ensured to be 53, and the baume degree of the brush coating paint is ensured to be 58.
The thickness of the dried resin sand mold surface coating layer is 1.0 mm.
The natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
EXAMPLE five
The embodiment provides a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 25% of zircon powder, 35% of spheroidized mixture, 3% of lithium bentonite, 2% of thermosetting phenolic resin, 3% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 50%; the granularity of the nodulizer and the inoculant is 50-100 meshes; the auxiliary agent comprises 0.5 percent of polyvinyl butyral, 2.5 percent of iron oxide red and 0.5 percent of defoaming agent.
The particle size of the zircon powder is 250 meshes.
The granularity of the lithium bentonite is 350 meshes.
The granularity of the iron oxide red is 250 meshes.
The nodulizer is 3-8 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg7.0-9.0, RE2.5-3.5, Ca1.5-2.5, Al less than or equal to 1.2, and the balance of iron.
The inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: si70-76, Ca1.0-2.0, Ba1.0-3.0, Al1.0-2.0, and the balance of iron.
The method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
The flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
After the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree proportion instrument, the baume degree of the flow coating paint is ensured to be 53, and the baume degree of the brush coating paint is ensured to be 58.
The thickness of the dried resin sand mold surface coating layer is 0.9 mm.
The natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
EXAMPLE six
The embodiment provides a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 30% of zircon powder, 40% of spheroidized mixture, 3% of lithium bentonite, 2% of thermosetting phenolic resin, 3% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 50%; the granularity of the nodulizer and the inoculant is 70-140 meshes; the auxiliary agent comprises 0.5 percent of polyvinyl butyral, 2.5 percent of iron oxide red and 0.5 percent of defoaming agent.
The particle size of the zircon powder is 250 meshes.
The granularity of the lithium bentonite is 350 meshes.
The granularity of the iron oxide red is 250 meshes.
The nodulizer is 3-8 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg7.0-9.0, RE2.5-3.5, Ca1.5-2.5, Al less than or equal to 1.2, and the balance of iron.
The inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: si70-76, Ca1.0-2.0, Ba1.0-3.0, Al1.0-2.0, and the balance of iron.
The method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
The flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
After the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree proportion instrument, the baume degree of the flow coating paint is ensured to be 55, and the baume degree of the brush coating paint is ensured to be 60.
The thickness of the dried resin sand mold surface coating layer is 0.8 mm.
The natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
EXAMPLE seven
The embodiment provides a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 25% of zircon powder, 40% of spheroidized mixture, 3% of lithium bentonite, 2% of thermosetting phenolic resin, 3% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 40%; the granularity of the nodulizer and the inoculant is 70-140 meshes; the auxiliary agent comprises 0.5 percent of polyvinyl butyral, 2.5 percent of iron oxide red and 0.5 percent of defoaming agent.
The particle size of the zircon powder is 250 meshes.
The granularity of the lithium bentonite is 350 meshes.
The granularity of the iron oxide red is 250 meshes.
The nodulizer is 3-8 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg7.0-9.0, RE2.5-3.5, Ca1.5-2.5, Al less than or equal to 1.2, and the balance of iron.
The inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: si70-76, Ca1.0-2.0, Ba1.0-3.0, Al1.0-2.0, and the balance of iron.
The method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
The flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
After the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree specific gravity meter, so that the baume degree of the flow coating paint is ensured to be 52, and the baume degree of the brush coating paint is ensured to be 57.
The thickness of the dried resin sand mold surface coating layer is 1.1 mm.
The natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
Example eight
The embodiment provides a coating for thoroughly eliminating the defects of a reaction layer on the surface of a ductile iron member, which comprises the following components in percentage by weight: 30% of zircon powder, 35% of spheroidized mixture, 3% of lithium bentonite, 2% of thermosetting phenolic resin, 3% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 60%; the granularity of the nodulizer and the inoculant is 70-140 meshes; the auxiliary agent comprises 0.5 percent of polyvinyl butyral, 2.5 percent of iron oxide red and 0.5 percent of defoaming agent.
The particle size of the zircon powder is 250 meshes.
The granularity of the lithium bentonite is 350 meshes.
The granularity of the iron oxide red is 250 meshes.
The nodulizer is 3-8 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg7.0-9.0, RE2.5-3.5, Ca1.5-2.5, Al less than or equal to 1.2, and the balance of iron.
The inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: si70-76, Ca1.0-2.0, Ba1.0-3.0, Al1.0-2.0, and the balance of iron.
The method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member comprises the following steps:
1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
4) and finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming.
The flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer.
After the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree proportion instrument, the baume degree of the flow coating paint is ensured to be 53, and the baume degree of the brush coating paint is ensured to be 58.
The thickness of the dried resin sand mold surface coating layer is 1.2 mm.
The natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
The coating of the first to eighth embodiments is applied to the furan resin sand molding of a security balance weight block ductile iron member with a larger thermal node phi of 80mm, the performance of the coating of each embodiment is monitored, and after the casting iron liquid is molded, a casting body is taken to perform surface flake graphite reaction layer and spheroidization grade detection, so that the following table is obtained:
as can be seen from the above table, the coating of the invention has good suspension stability, coating rheological property and supplementary spheroidization effect, and the thickness of the obtained reaction layer and graphite layer can be thoroughly eliminated, so that the original flaky graphite layer which can reach 1-5mm is controlled to be 0-160 mu m; the control of the particle sizes of a nodulizer and an inoculant of a nodulizing mixture in the coating is particularly critical, and the supplement of the nodulizing effect is not facilitated when the particle sizes are too large or too small; too thin or too thick a coating layer thickness is not good for coating and supplementing the spheroidizing effect.
The fifth example has the best effect, the suspension stability of the coating and the rheological property of the coating are better, the spheroidizing mixture of the rare earth magnesium silicon iron spheroidizing agent with the granularity of 50-100 meshes and the grain size of 3-8 and the supplementary spheroidizing effect of the coating with the thickness of 0.9mm are the best, the thicknesses of the reaction layer and the flake graphite layer are zero, the spheroidization grade is the best grade 1, the quality of the casting is the highest, and the adhesion effect and the supplementary spheroidizing effect of the coating to the surface of the sand mold are the best.
The other components in the coating of the invention have the following functions: the lithium bentonite has a suspension effect, prevents the paint from precipitating, and has an auxiliary high-temperature bonding effect; the thermosetting phenolic resin mainly plays a role in bonding and is matched with polyvinyl butyral (PVB) thermoplastic high polymer, so that the bonding force of the phenolic resin can be improved; polyvinyl butyral (PVB) has good thickening and seepage-proofing effects, and the defoaming agent has defoaming and foam-inhibiting effects and improves the wettability of the coating; the iron oxide red enables the sintering stripping performance of the coating layer to be better, and the surface smoothness of the casting is improved; ethanol is the carrier. Because the iron oxide red is added into the paint, the color of the prepared paint is brownish red.
The coating of the technical scheme of the invention can be used in the production of nodular iron castings produced by all furan resin sand molds and sand cores, the quality of the castings can be improved by common mechanical nodular iron castings, high-end wind power nodular iron castings, low-temperature rail transit nodular iron castings and outlet nodular iron castings can easily meet the technical requirements of users, the surface layer of the nodular iron castings after sand blasting cleaning has no reaction layer and sulfurization defect, the surface reaction layer defect of the nodular iron castings is thoroughly eliminated, the waste loss of the castings is greatly reduced, and the coating has high practical value. In addition, the coating is also suitable for producing the high nickel ductile iron parts by using phenolic resin sand shell molds, shell cores and shell green sand, the thickness of the flake graphite on the surface of the high nickel ductile iron can be controlled to be zero, and the quality of the high nickel ductile iron parts is greatly improved.
The above-mentioned embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and therefore, all equivalent changes made by the contents of the claims of the present invention should be included in the claims of the present invention.
Claims (1)
1. The coating for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron piece comprises the following components in percentage by weight: 25% of zircon powder, 35% of spheroidized mixture, 3% of lithium bentonite, 2% of thermosetting phenolic resin, 3.5% of auxiliary agent and the balance of ethanol; the spheroidized mixture is a mixture of a nodulizer and an inoculant, and the weight proportion of the inoculant in the nodulizer is 50%; the granularity of the nodulizer and the inoculant is 50-100 meshes; the auxiliary agent is polyvinyl butyral 0.5%, iron oxide red 2.5%, and defoaming agent 0.5%;
the granularity of the zircon powder is 250 meshes;
the granularity of the lithium bentonite is 350 meshes;
the granularity of the iron oxide red is 250 meshes;
the nodulizer is 3-8 rare earth magnesium-silicon-iron alloy, and comprises the following components in percentage by weight: si43-47, Mg7.0-9.0, RE2.5-3.5, Ca1.5-2.5, Al less than or equal to 1.2 and the balance of iron;
the inoculant is low-barium ferrosilicon alloy and comprises the following components (wt%: 70-76 parts of Si, 1.0-2.0 parts of Ca, 1.0-3.0 parts of Ba, 1.0-2.0 parts of Al and the balance of iron;
the method for thoroughly eliminating the defects of the reaction layer on the surface of the ductile iron member by using the coating comprises the following steps:
(1) preparing a coating according to the coating components and the weight percentage of each component, and uniformly stirring;
(2) coating the prepared flow coating paint on the surfaces of the upper sand mould and the lower sand mould of resin sand once, and igniting and drying; brushing the upper sand mold and the lower sand mold by using the brushing coating once, and igniting and drying;
(3) keeping the resin sand coated with the paint in an upper sand mold and a lower sand mold for a certain time through a natural gas through type drying furnace for thorough drying;
(4) finally, adding a pouring cup after the dried resin sand is subjected to upper and lower sand mould moulding, and pouring molten iron for forming;
the flow coating is carried out by adopting a closed flow coating machine, and the brush coating is stirred by adopting a vacuum stirrer;
after the paint is uniformly stirred, the baume degree of the paint solution is measured by using a baume degree proportion instrument, the baume degree of the flow coating is ensured to be 53, and the baume degree of the brush coating is ensured to be 58;
the thickness of the dried resin sand mold surface coating layer is 0.9 mm;
the natural gas passing-through drying furnace is used for drying the resin sand mold at the set temperature of 120-150 ℃ for 20-30 minutes.
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