CN103056284B - The application of clay holomorphosis sand modifier, method of modifying and modifier - Google Patents

Abstract

The invention discloses a clay completely regenerated sand modifier, a modification method and the application of the modifier, wherein the modifier is hydrochloric acid with a concentration of 0.05-5mol/L; the modification method includes the following steps: (1) adding A modifier is added to the completely regenerated clay sand, and the modifier accounts for 2-10% of the total mass of the completely regenerated clay sand; (2) After mixing evenly, let it stand for 1-60 minutes; (3) For the mixture after standing Carry out drying treatment so that the moisture content is lower than 0.2%; the modified clay completely reclaimed sand can be used to mix coated sand, hot box sand and cold box sand. The beneficial effect of the present invention is: easy to use, by adding modifier, not only reduces the acid consumption value of completely regenerated clay sand, but also improves the tensile strength of molding sand mixed with it, and improves the casting process of completely regenerated clay sand performance.

Description

Modifier, Modification Method and Application of Modifier for Completely Regenerated Clay Sand

technical field

The invention relates to the casting process performance of completely regenerated clay sand, in particular to a modifier for completely regenerated clay sand, a modification method and the application of the modifier.

Background technique

Machinery manufacturing industry is the pillar industry of our country, and casting is the basic industry of machinery manufacturing industry. The molds used in foundry production are mainly sand molds, ceramic molds, metal molds, plaster molds, etc. Among them, the castings produced by sand casting account for more than 80% of the total output of castings. Sand casting can be divided into clay sand casting, resin sand casting and water glass sand casting according to the different binders used. The clay sand production process has become the most commonly used casting production process in the sand casting method because of its cheap and easy-to-obtain raw materials, easy handling, strong reusability, strong ability to adapt to molding methods, and convenient storage and transportation.

my country is a big country in the production of castings. In 2011, the output of castings reached more than 39 million tons. It is estimated that about 60% of the castings are produced by clay-sand process, and the castings produced by clay-sand process are about 23.4 million tons. According to the statistics of my country's foundry industry, for every ton of casting produced, one ton of waste sand will be discharged, and more than 23.4 million tons of clay waste sand will be discharged every year. Developed countries such as Japan emit 0.22 tons of waste sand per ton of castings produced. Compared with this, under the same casting output, my country's waste sand discharge is 5 times that of Japan and other developed countries. This not only causes a huge waste of resources, but also causes great pollution to the environment. In my country's foundry production, the input of materials and energy accounts for about 55-70% of its output value, and the foundry industry is facing enormous pressure from the environment and energy. In foundry production, a large amount of resources and energy are invested, and excessive environmental pollution poses severe challenges to my country's foundry industry. Therefore, developing green casting technology, strictly controlling environmental pollution in the production process, improving the reusability of old sand, saving limited silica sand resources, reducing production costs, and further increasing the yield of castings have become urgent and arduous tasks for the foundry industry today. . The recycling of old sand is one of the important contents of realizing green casting. Carrying out the research on the complete regeneration technology of clay old sand is an important measure to reduce the cost of castings, improve the quality of castings, reduce environmental pollution and save resources.

In foundry production, part of the clay near the surface of the cavity in the molding sand is baked at high temperature due to the heat of the high-temperature molten metal and loses crystallization water, thereby losing its bonding ability and becoming dead clay. Part of these clays are mixed in the molding sand as powder, and the other part is firmly wrapped on the surface of the sand in the form of a ceramic film, which seriously affects the performance of the molding sand, reducing its air permeability and plasticity, and increasing its brittleness; secondly, In the process of casting production, due to the repeated heating of high-temperature metals, a small part of the sand is broken, and the broken small sand particles are also mixed with the old sand and become part of the dust in the old sand, thus affecting the performance of the molding sand; In addition, a large number of organic and inorganic binder core sands are used in modern foundry production, and the decomposition products of these core sands and chemical binders are also partially mixed into the molding sand; the mixing of coal powder and its substitute pyrolysis products further reduces the clay The activity of the molding sand deteriorates the performance of the molding sand. In order to produce qualified castings, each production enterprise stabilizes the performance of the molding sand by regularly or irregularly discharging part of the old sand and adding new sand at the same time. This part of the discharged clay and old sand cannot be used for foundry production again without regeneration treatment, and can only be treated as solid waste, which not only causes waste of natural resources, but also causes environmental pollution.

The regeneration of old clay sand is to use physical or chemical methods to peel off and remove the inert film and impurities on the surface of the sand grains, so that the sand grains are exposed to the original surface, so that the regenerated sand can reach or approach the performance of new sand. The regeneration of old clay sand can be divided into complete regeneration and incomplete regeneration. When the reclaimed sand is used in the clay sand process, it is not necessary to perform complete regeneration. It is only necessary to reduce the fine powder content of the old sand and improve the particle size distribution of the old sand through regeneration. At this time, the reclaimed sand has a higher mud content than the new sand, and the core sand is mixed with the right The impact on the performance of the molding sand has not been eliminated, and the recycled sand can only be used to mix clay sand; when the recycled sand is used for core making, there are strict requirements on the ignition loss, acid consumption value and mud content of the recycled sand. The old clay sand must be completely regenerated, not only to reduce the mud content of the old sand, but also to completely or mostly eliminate the influence of the mixing of core sand on the performance of the molding sand.

The process adaptability of clay completely regenerated sand for mixing various binder type (core) sands mainly depends on the casting process performance when it is used to mix type (core) sand. In recent years, there have been many researches on the method of complete regeneration of old clay sand at home and abroad. For example, the technical route of high-temperature roasting + mechanical regeneration + micro-powder separation is adopted in China, which contains water glass sand, coated sand, self-setting resin sand, The old clay sand of cold box sand and hot box sand is regenerated, and the particle size does not change significantly, the particle shape is more rounded, and the fine powder content is lower than that of the same kind of new sand, but the acid consumption value (10-25) is higher The clay completely regenerates the sand. Due to the high acid consumption value of fully regenerated clay sand, when using fully regenerated clay sand to mix core sand, its overall casting process performance is lower than that of new sand. How to improve the foundry performance of completely reclaimed clay sand is an important problem to be solved in the field of clay used sand regeneration.

Contents of the invention

In order to reduce the acid consumption value of completely regenerated clay sand and improve its casting process performance, the invention provides a modifier, a modification method and an application of the modifier for completely regenerated clay sand.

In order to achieve the purpose of the above invention, the present invention provides a modifier for fully regenerated clay sand, wherein the modifier is hydrochloric acid with a concentration of 0.05-5 mol/L.

The concentration of the hydrochloric acid may further preferably be 0.5-3 mol/L.

In order to achieve the above-mentioned purpose of the invention, the present invention provides a method for modifying clay completely reclaimed sand utilizing the above-mentioned modifying agent, wherein the modification method comprises the following steps:

(1) Add modifiers to the completely regenerated clay sand, and the modifier accounts for 2-10% of the total mass of the completely regenerated clay sand;

(2) After mixing evenly, let it stand for 1-60 minutes;

(3) Dry the mixture after standing to keep the moisture content below 0.2%.

Wherein, when the completely regenerated clay sand is used for mixing coated sand, in the step (1), the addition amount of the modifier is 2-8%.

Wherein, when the completely regenerated clay sand is used for mixing hot box sand, in the step (1), the addition amount of the modifier is 4-10%.

Wherein, when the completely regenerated clay sand is used for mixing cold core box sand, in the step (1), the addition amount of the modifier is 4-10%.

Wherein, the moisture content in the step (3) is preferably lower than 0.1%.

In order to achieve the purpose of the above invention, the present invention also provides an application of the above-mentioned modifier, wherein, after the modifier is used to modify the completely regenerated clay sand, it can be used for mixing coated sand, thermal core Box sand and cold box sand.

The beneficial effects brought by the technical solution provided by the embodiment of the present invention are: easy to use, by adding a modifier, not only the acid consumption value of the completely regenerated clay sand is reduced, but also the tensile strength of the molding sand is improved, and the clay completeness is improved. Foundry process performance of recycled sand.

Detailed ways

The present invention will be further described below in conjunction with the examples.

Example 1 Clay is fully reclaimed sand modified and used to mix coated sand

An embodiment of the present invention provides a modifier for fully regenerated clay sand, wherein the modifier is hydrochloric acid with a concentration of 0.9 mol/L.

The embodiment of the present invention also provides a method for modifying clay completely regenerated sand using the modifier described above, wherein the modification method includes the following steps:

(1) Weigh 3000g of completely regenerated clay sand, add 150g of modifier to it, the modifier is 0.9mol/L hydrochloric acid;

(2) After mixing evenly, let it stand for 30 minutes;

(3) Dry the mixture after standing to make the water content lower than 0.1%, and obtain the completely regenerated sand of modified clay with an acid consumption value of 3.

Take new sand, fully regenerated clay sand and the modified clay fully regenerated sand of this embodiment, and mix the coated sand according to the same process ratio and process parameters. Put the "8" tensile sample mold into an electric constant temperature blast drying oven and heat it to 232°C, then take out the sample mold, add the prepared coated sand into the mold, and put the mold back into the drying oven to keep warm 3min, then take out the sample and test the hot state tensile strength of the sample within 15s, after cooling to room temperature, test the tensile strength at room temperature at 1h, the test results are shown in Table 1.

Table 1 Comparison table of foundry process performance when mixing coated sand

Sand properties new sand recycled sand Modified recycled sand Hot tensile strength/MPa 0.9 0.36 1.15 1h tensile strength/MPa 1.84 1.44 2.08

From the data in Table 1, it can be seen that compared with new sand and unmodified clay completely regenerated sand, the hot tensile strength and 1h tensile strength was significantly improved.

Example 2 Completely modified clay regenerated sand and applied to mixed hot box sand

An embodiment of the present invention provides a modifier for fully regenerated clay sand, wherein the modifier is hydrochloric acid with a concentration of 1.1 mol/L.

The embodiment of the present invention also provides a method for modifying clay completely regenerated sand using the modifier described above, wherein the modification method includes the following steps:

(1) Weigh 3000g of completely regenerated clay sand, add 180g of modifier to it, the modifier is 1.1mol/L hydrochloric acid;

(2) After mixing evenly, let it stand for 22 minutes;

(3) Dry the mixture after standing to make the water content lower than 0.2%, and obtain the completely regenerated sand of modified clay with an acid consumption value of 3.5.

Take new sand, completely regenerated clay sand and completely regenerated clay sand modified in this embodiment, respectively, and mix hot core box sand according to the same process ratio and process parameters. Immediately after the sand is produced, add the "8" tensile sample mold, and then put it into a DGG-9070B type electric heating constant temperature blast drying oven that has been kept at 260°C for heating and curing. The curing time is 270s. The hot-state tensile strength of the cured hot core box sample was tested within 15s, and the normal temperature tensile strength was tested 1h after cooling to room temperature. The test results are shown in Table 2.

Table 2 Casting process performance comparison table when mixing hot core box sand

Sand properties new sand recycled sand Modified recycled sand Hot tensile strength/MPa 1.56 0.67 1.82 1h tensile strength/MPa 1.88 1.54 2.2

From the data in Table 2, it can be seen that compared with new sand and unmodified clay completely regenerated sand, the thermal state tensile strength of hot core box sand mixed with clay completely regenerated sand modified by the modifier of the present invention is and 1h tensile strength were significantly improved.

Example 3 Modification of fully regenerated sand with clay and application to mixed core box sand

An embodiment of the present invention provides a modifier for fully regenerated clay sand, wherein the modifier is hydrochloric acid with a concentration of 2.7 mol/L.

The embodiment of the present invention also provides a method for modifying clay completely regenerated sand using the modifier described above, wherein the modification method includes the following steps:

(1) Weigh 3000g of completely regenerated clay sand, add 210g of modifier to it, the modifier is 2.7mol/L hydrochloric acid;

(2) After mixing evenly, let it stand for 46 minutes;

(3) Dry the mixture after standing to make the water content lower than 0.2%, and obtain the completely regenerated sand of modified clay with an acid consumption value of 4.

Take new sand, completely regenerated clay sand and modified clay completely regenerated sand respectively, and mix cold core box sand according to the same process ratio and process parameters. Immediately after the sand is produced, the "8" sample is made in the cold box mold, and then put into the cold box sand sample preparation device to solidify. The initial tensile strength and 1h tensile strength tests were performed on the solidified cold box sand "8" sample respectively, and the test results are shown in Table 3.

Table 3 Casting process performance comparison table when mixing cold core box sand

Sand properties new sand recycled sand Modified recycled sand Initial tensile strength/MPa 0.96 0.78 1.44 1h tensile strength/MPa 1.58 1.29 1.91

From the data in Table 3, it can be seen that compared with new sand and unmodified clay completely regenerated sand, the initial tensile strength of cold box sand mixed with clay completely regenerated sand modified by the modifier of the present invention is and 1h tensile strength were significantly improved.

In a word, by adopting the modifying agent of the embodiment of the present invention, the acid consumption value of the completely regenerated clay sand is reduced, and the casting process performance of the completely regenerated clay sand is improved.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (6)

1. a clay holomorphosis sand method of modifying, is characterized in that, described method of modifying comprises the following steps:

(1) in clay holomorphosis sand, add modifier, described modifier accounts for the 2-10% of clay holomorphosis sand gross mass;

(2) rear standing 1-60min is mixed;

(3) to leave standstill after compound carry out drying process, make its moisture lower than 0.2%;

Wherein, described modifier is the hydrochloric acid of 2.7-5mol/L concentration.

2. method of modifying according to claim 1, is characterized in that, the concentration of described hydrochloric acid is 2.7-3mol/L.

3. method of modifying according to claim 1, is characterized in that, when described clay holomorphosis sand is used for mixed precoated sand processed, in described step (1), the addition of described modifier is 2-8%.

4. method of modifying according to claim 1, is characterized in that, when described clay holomorphosis sand heats core box sand for mixing, in described step (1), the addition of described modifier is 4-10%.

5. method of modifying according to claim 1, is characterized in that, when described clay holomorphosis sand is used for mixed refrigeration core box sand, in described step (1), the addition of described modifier is 4-10%.

6. the method for modifying according to claim 1-5 any one, is characterized in that, the moisture in described step (3) is lower than 0.1%.