阅读说明：本技术 一种覆膜砂壳型铁砂负压铸造工艺 (Negative-pressure casting process for precoated sand shell type iron sand ) 是由 于建军 刘建新 姚永奎 于 2020-05-12 设计创作，主要内容包括：本发明涉及一种覆膜砂壳型铁砂负压铸造工艺,属于铸造工艺技术领域。包括制壳、喷涂料、组装、铁砂埋箱、抽真空、浇注、废气净化处理、拆箱、铁砂筛选发明的有益效果是：采用铁砂激冷,能够实现铸件的快速冷却,保证铸件的致密度,提高铸件质量。减少了铸造型砂和粘结剂的使用,减少了铸造废气的产生,改善了铸造环境。(The invention relates to a negative-pressure casting process of precoated sand shell type iron sand, belonging to the technical field of casting processes. The invention comprises the following steps of shell making, paint spraying, assembling, iron sand burying, vacuumizing, pouring, waste gas purification treatment, box dismantling and iron sand screening, and has the beneficial effects that: the adoption of iron sand chilling can realize the rapid cooling of the casting, ensure the density of the casting and improve the quality of the casting. The use of casting molding sand and a binder is reduced, the generation of casting waste gas is reduced, and the casting environment is improved.)

1. The utility model provides a tectorial membrane sand shell type iron sand negative pressure casting process which characterized in that includes system shell, spray coating, equipment, iron sand buries the case, evacuation, pouring, exhaust purification, unpacking, iron sand screening, the process sequence is:

(1) preparing a shell: preparing a shell by using precoated sand, wherein the thickness of the sand shell is 5-8 mm;

(2) spraying a material: spraying a coating on the inner surface of the shell, wherein the coating is a zircon powder water-based coating, and the spraying thickness of the coating is 0.5-1 mm;

(3) assembling: assembling a casting shell mold and a water riser shell mold in a sand box according to a drawing;

(4) burying iron sand in a box: filling iron sand outside the shell mold, compacting, sealing by adopting a plastic film, filling fine iron sand at the position close to the shell mold, and filling coarse iron sand at the position far away from the shell mold;

(5) vacuumizing: connecting the sand box with a vacuumizing device, vacuumizing the sand box, and forming negative pressure in the sand box;

(6) pouring: pouring molten steel into the shell mold, and simultaneously leading out gas generated in the pouring process through vacuum-pumping equipment;

(7) and (3) waste gas purification treatment: purifying the extracted casting waste gas;

(8) unpacking: unpacking and shakeout the cooled casting and sand box;

(9) screening iron sand: and carrying out magnetic separation on the unpacked molding sand and iron sand, screening the magnetic separated iron sand, and warehousing and storing according to the granularity.

2. The negative-pressure casting process of the precoated sand shell type iron sand as claimed in claim 1, wherein the precoated sand adopts molding sand in the following mixture ratio (mass ratio): 12-14% of 70/140-mesh silica sand, 12-14% of 70/140-mesh Baozhu sand, 30-35% of 100/200-mesh silica sand and 30-35% of 100/200-mesh Baozhu sand, wherein the addition amount of the resin is as follows (mass ratio): 2 to 4 percent.

3. The negative-pressure casting process of precoated sand shell type iron sand as claimed in claim 2, wherein during the mixing of the precoated sand, 100/200-mesh silica sand and 100/200-mesh Baozhu sand are added firstly for dry mixing for 1-2 minutes, then 70/140-mesh silica sand and 70/140-mesh Baozhu sand are added for dry mixing for 1-2 minutes, and resin is added.

4. The negative-pressure casting process of the precoated sand shell type iron sand as claimed in claim 1, wherein the grain diameter of the fine iron sand is 1.5-2.5 mm, the grain diameter of the coarse iron sand is 2.5-3.5 mm, and the water content of the iron sand is less than 0.8%.

5. The negative-pressure casting process of the precoated sand shell type iron sand as claimed in claim 1, wherein the thickness of the fine iron sand is 1-1.5 times of the thickness of the casting wall, and the thickness of the coarse iron sand iron is more than 1.5 times of the thickness of the fine iron sand.

6. The negative-pressure casting process of the precoated sand shell type iron sand as claimed in claim 1, wherein the degree of vacuum pumping is 0.02-0.04 MPa.

Technical Field

The invention relates to a negative-pressure casting process of precoated sand shell type iron sand, belonging to the technical field of casting processes.

Background

Sand casting is a traditional manufacturing method, and a plurality of factors of large amount of waste sand generated due to poor surface quality of castings are replaced by a plurality of novel casting methods. The high surface precision of the castings can be ensured by the casting of the iron mold coated with the precoated sand, the compactness of the castings can be ensured by the chilling action of the iron mold, but the iron mold is only suitable for the production of large-batch castings due to the high manufacturing cost of the iron mold, and the treatment of harmful gas generated during the pouring of the precoated sand is also an important factor for restricting the application of the precoated sand. The lost foam negative pressure casting has the advantages of simple and easy mold making and the like, but the defects of insufficient casting and serious surface oxidation are easily caused by a large amount of smoke generated during casting, and a large amount of toxic smoke is generated during the melting of lost foam particles to cause environmental pollution. Therefore, a novel casting process needs to be invented, the casting is compact, the used molding sand is less, and waste gas is reduced during casting.

Disclosure of the invention

The invention aims to solve the technical problem of providing a precoated sand shell type iron sand negative pressure casting process, which realizes compact casting, uses less molding sand and reduces waste gas during casting.

The technical scheme of the invention is as follows:

the utility model provides a tectorial membrane sand shell type iron sand negative pressure casting process, includes system shell, spray coating, equipment, iron sand buries the case, evacuation, pouring, exhaust purification, unpacking, iron sand screening, and the process steps is:

(1) preparing a shell: preparing a shell by using precoated sand, wherein the thickness of the sand shell is 5-8 mm;

(2) spraying a material: spraying a coating on the inner surface of the shell, wherein the coating is a zircon powder water-based coating, and the spraying thickness of the coating is 0.5-1 mm;

(3) assembling: assembling a casting shell mold and a water riser shell mold in a sand box according to a drawing;

(4) burying iron sand in a box: filling iron sand outside the shell mold, compacting, sealing by adopting a plastic film, filling fine iron sand at the position close to the shell mold, and filling coarse iron sand at the position far away from the shell mold;

(5) vacuumizing: connecting the sand box with a vacuumizing device, vacuumizing the sand box, and forming negative pressure in the sand box;

(6) pouring: pouring molten steel into the shell mold, and simultaneously leading out gas generated in the pouring process through vacuum-pumping equipment;

(7) and (3) waste gas purification treatment: purifying the extracted casting waste gas;

(8) unpacking: unpacking and shakeout the cooled casting and sand box;

(9) screening iron sand: and carrying out magnetic separation on the unpacked molding sand and iron sand, screening the magnetic separated iron sand, and warehousing and storing according to the granularity.

The precoated sand is prepared from molding sand in the following proportion by mass: 12-14% of 70/140-mesh silica sand, 12-14% of 70/140-mesh Baozhu sand, 30-35% of 100/200-mesh silica sand and 30-35% of 100/200-mesh Baozhu sand, wherein the addition amount of the resin is as follows (mass ratio): 2 to 4 percent.

When the precoated sand is mixed, 100/200-mesh silica sand and 100/200-mesh Baozhu sand are added firstly and are mixed for 1-2 minutes, then 70/140-mesh silica sand and 70/140-mesh Baozhu sand are added and are mixed for 1-2 minutes, and resin is added.

The grain size diameter of the fine iron sand is 1.5-2.5 mm, the grain size diameter of the coarse iron sand is 2.5-3.5 mm, and the water content of the iron sand is less than 0.8%.

The thickness of the fine iron sand is 1-1.5 times of the thickness of the casting wall, and the thickness of the coarse iron sand is more than 1.5 times of the thickness of the fine iron sand.

The vacuum degree is 0.02-0.04 MPa.

The invention has the beneficial effects that: the adoption of iron sand chilling can realize the rapid cooling of the casting, ensure the density of the casting and improve the quality of the casting. The use of casting molding sand and a binder is reduced, the generation of casting waste gas is reduced, and the casting environment is improved.

Examples

The present invention will be described in further detail with reference to specific examples.