Sand mold binder for steel casting and preparation and use method thereof

Abstract

The present invention provides a sand mold binder for steel casting and its preparation and use methods, relating to the field of metallurgical casting technology. The sand mold binder for steel casting comprises Part A (sodium silicate, water, rice bran, and an active agent, sodium lauryl sulfate) and Part B (oxalic acid and water). The specific components, by weight, are as follows: Part A: sodium silicate: 40% to 60%; water: 38% to 55%; rice bran: 0.5% to 3%; sodium lauryl sulfate: 0.2% to 1.0%; Part B: oxalic acid: 10% to 20%; water: 80% to 90%. The sand mold binder for steel casting provided by the present invention can effectively inhibit the occurrence of "white frost" powdering and cracking on the sand mold surface; improve the collapsibility, surface strength, and compressive strength of the sand mold; significantly increase the sand mold hardening speed; reduce the cost of sand cleaning in the later stages of casting; and use inexpensive rice bran as a raw material, thereby reducing the cost of sand mold preparation.

Description

Technical field

[0001] The invention belongs to the technical field of metallurgical casting, and in particular relates to a sand mold binder for steel casting and a preparation and use method thereof. [Background Technology]

[0002] The foundry industry requires a large number of sand molds (including sand cores) to complete the casting of liquid metal. Sand molds or sand cores are made primarily of raw sand and can be categorized by the binder used: clay sand molds, water glass sand molds, and phenolic resin sand molds. Clay sand molds were once widely used due to their abundant and inexpensive resources. However, with increasing demands for casting quality, clay sand molds have become increasingly vulnerable to defects such as cracking, sand erosion, sand inclusions, and pores. The subsequent emergence of water glass sand molds and phenolic resin sand molds has offset the shortcomings of clay sand molds and has become widely used. However, from a cost and environmental perspective, phenolic resin sand molds are not only expensive but also generate harmful gases during hardening, drying, and use, leading to their gradual phase-out. Water glass sand molds, with their high strength, excellent refractory properties, ease of operation, favorable working conditions, simple processing and equipment, and low cost, have become the mainstay of casting sand in my country's steel casting production. However, certain problems have been exposed during the use of water glass sand molds. First, the collapsibility is poor, and the cleaning workload of the casting is large, which reduces production efficiency and affects the surface quality of the casting. Second, when the sand mold is placed for more than 48 hours, its surface is prone to "white frost" powdering, which leads to a decrease in the strength of the sand mold and affects the use effect of the sand mold. [Summary of the invention]

[0003] To overcome the shortcomings of the prior art, the present invention provides a sand mold binder for steel casting that can inhibit the appearance of "white frost" powdering and cracking on the sand mold surface, and rapidly harden the sand mold, improve surface strength and compressive strength, and enhance disintegration resistance, as well as a preparation and use method thereof. The technical solutions adopted are as follows:

[0004] A sand mold binder for steel casting, the binder consisting of two parts A and B, wherein part A comprises sodium silicate, water, rice bran, and sodium lauryl sulfate, and part B comprises oxalic acid and water; the specific components of parts A and B are proportioned by weight as follows:

[0005] Part A: Sodium silicate: 40% to 60%; Water: 38% to 55%; Rice bran: 0.5% to 3%; Sodium lauryl sulfate: 0.2% to 1.0%.

[0006] Part B: Oxalic acid: 10% to 20%; Water: 80% to 90%.

[0007] Furthermore, the modulus of the sodium silicate is 3.1 to 3.4.

[0008] Furthermore, the rice bran is in a powdery form with a mesh size of not less than 200.

[0009] Furthermore, the rice bran is one or more of rice bran, corn bran, and wheat bran.

[0010] A method for preparing a sand mold binder for steel casting, comprising the following steps:

[0011] Part A:

[0012] Prepare the materials according to the following composition ratios: sodium silicate: 40% to 60%; water: 38% to 55%; rice bran: 0.5% to 3%; sodium lauryl sulfate: 0.2% to 1.0%;

[0013] ① Dissolve anhydrous sodium silicate powder in water to form a viscous liquid with a density of 1.45-1.72 g / cm 3 , then seal and place in an environment of 15-30℃ for 24-36h;

[0014] ② Add 5% to 10% sodium lauryl sulfate aqueous solution to liquid ① and stir evenly;

[0015] ③ putting rice bran into water at 50-80° C. and stirring for 60-100 minutes to obtain a paste, wherein the ratio of rice bran to water in the paste is 1:(3-5) by weight;

[0016] ④Add the paste in ③ to the liquid in ② and stir evenly, then seal and place in an environment of 15-30℃;

[0017] Part B:

[0018] ⑤ Prepare oxalic acid into a 10% to 20% aqueous solution and seal it for later use as an additional regulator.

[0019] Furthermore, the 5% to 10% sodium lauryl sulfate aqueous solution in Part A② is prepared by dissolving sodium lauryl sulfate in water.

[0020] A method for using a sand mold binder for steel casting comprises the following steps: firstly adding part A of the binder to raw sand in an amount of 5% to 10% of the weight of the raw sand; after mixing, adding part B of the binder, an oxalic acid aqueous solution, to the raw sand mixed with the binder in an amount of 0.2% to 1.0% of the weight of the raw sand; and finally, preparing a sand mold or a sand core.

[0021] Beneficial Effects: The sand mold binder provided by this invention effectively inhibits the appearance of "white frost" powdering and cracking on the sand mold surface; increases the sand mold collapse rate from 85% to 98%, reducing the cost of sand cleaning during the later stages of casting; achieves surface strength and compressive strength of 0.5-1.0 MPa and 2.0-3.5 MPa, respectively, and increases the sand mold hardening rate by over 25%. Using inexpensive rice bran as a raw material reduces the cost of sand mold preparation. The technical solution provided by this invention is suitable for use in the production of sand molds for steel casting. [Specific implementation method]

[0022] A sand mold binder for steel casting, comprising part A (sodium silicate, water, rice bran, and an activator, sodium lauryl sulfate) and part B (oxalic acid and water), wherein the specific components of each part are in the following proportions by weight:

[0023] Part A: Sodium silicate: 40% to 60%; Water: 38% to 55%; Rice bran: 0.5% to 3%; Sodium lauryl sulfate: 0.2% to 1.0%.

[0024] Part B: Oxalic acid: 10% to 20%; Water: 80% to 90%.

[0025] The sodium silicate modulus is 3.1 to 3.4, the rice bran is in a powdery form with a mesh size of not less than 200, and the rice bran is one or more of rice bran, corn bran, and wheat bran. The specific preparation method is carried out according to the following steps:

[0026] (1) Put anhydrous sodium silicate powder into a container, then pour water into the container to fully dissolve the sodium silicate into a viscous liquid with a density of 1.45-1.72 g / cm 3 , then seal and place in an environment of 15-30℃ for 24-36h;

[0027] (2) In order to reduce the low-temperature viscosity, facilitate the formation and preparation of the sand mold, and at the same time improve the compressive strength of the sand mold, a 5% to 10% aqueous solution of an active agent, sodium lauryl sulfate, is added to the viscous liquid and stirred evenly;

[0028] (3) putting rice bran into water at 50-80° C. and stirring for 60-100 minutes to obtain a rice bran paste, wherein the ratio of rice bran to water in the paste is 1:(3-5) by weight;

[0029] (4) Add the paste in (3) to the liquid in (2) and stir evenly, then seal and place in an environment of 15-30°C;

[0030] (5) Oxalic acid is prepared into a 10% to 20% aqueous solution and sealed into individual bags, which are then added to the adhesive during use.

[0031] Because rice bran contains a certain amount of starch and cellulose, when mixed into a paste in water at 50-80°C, the starch converts to polysaccharides at this temperature. During the sand mold preparation process, the polysaccharides effectively inhibit the "white frost" and powdering of the sand mold surface caused by the presence of moisture in the ingredients. Furthermore, the polysaccharides converted from starch absorb the free water in the cellulose, preventing hydrolysis reactions. The cellulose in rice bran prevents microcracks in the sand mold during hardening and dehydration, improves the surface strength of the sand mold, and prevents sand from encrusting the casting surface during casting. Furthermore, the cellulose in the rice bran paste significantly decreases in strength during the transition from high temperature (1000-1700°C) to low temperature (<500°C), which helps improve the collapsibility of the sand mold after use and reduces the labor intensity of cleaning the casting sand.

[0032] Sodium lauryl sulfate is used as an active agent, which is usually used in cosmetics, detergents, textiles, papermaking, lubrication and pharmaceuticals. Since this active agent is an anionic surfactant, it has strong hydrophobicity and can be beneficial to the discharge of moisture in the sand mold, which helps to improve the drying effect of the sand mold.

[0033] At the same time, it can also reduce the viscosity of the sand material during the sand mold preparation process to facilitate sand mold preparation and improve the compressive strength of the sand mold. It can be applied to the preparation of some sand molds with relatively complex structures.

[0034] Oxalic acid aqueous solution is not allowed to be mixed with the adhesive before use when used in conjunction with the adhesive. This is mainly because after oxalic acid has been in contact with sodium silicate aqueous solution for a long time, the carboxyl functional group COOH in it can easily cause flocculent precipitation in the sodium silicate aqueous solution, and the precipitation reduces the effectiveness of the adhesive.

[0035] When preparing a sand mold, first add binder part A to the raw sand at a rate of 5% to 10% by weight. After mixing, add binder part B, an oxalic acid solution, at a rate of 0.2% to 1.0% by weight. Mix thoroughly before preparing the sand mold or core. At room temperature, the carboxyl groups (COOH) in oxalic acid promote the hydrolysis of sodium silicate, increasing the number of silicate molecules and causing a polycondensation reaction, which hardens the sand mold. During the drying process, oxalic acid decomposes at high temperatures to release CO2, further promoting the hydrolysis of sodium silicate, accelerating the hardening of the sand mold, and rapidly removing moisture from the sand mold, shortening the drying process for hardening.

[0036] Example 1

[0037] A sand mold binder for steel casting, comprising part A (sodium silicate, water, rice bran, and an activator, sodium lauryl sulfate) and part B (oxalic acid and water), wherein the specific components of each part are in the following proportions by weight:

[0038] Part A: Sodium silicate: 45%; Water: 52%; Rice bran: 2.5%; Sodium lauryl sulfate: 0.5%.

[0039] Part B: Oxalic acid: 12%; Water: 88%.

[0040] Wherein, the sodium silicate modulus is 3.15, the rice bran is in a powdery form of 250 meshes, and the rice bran is rice bran. The specific preparation method is carried out according to the following steps:

[0041] (1) Put the anhydrous sodium silicate powder into the container, then pour water into the container to fully dissolve the sodium silicate into a viscous liquid with a density of 1.65g / cm 3 , then seal and place in an environment of 18℃~23℃ for 25h;

[0042] (2) adding a 6% aqueous solution of sodium lauryl sulfate as an active agent to the viscous liquid and stirring the solution uniformly; the 6% aqueous solution of sodium lauryl sulfate is prepared by dissolving 0.5% of sodium lauryl sulfate in part A in water;

[0043] (3) putting rice bran into water at 55° C. to 60° C. and stirring for 70 minutes to obtain a rice bran paste, wherein the ratio of rice bran to water in the paste is 1:3 by weight;

[0044] (4) adding the rice bran paste to the liquid in (2) and stirring evenly, and then sealing and placing in an environment of 15 to 30°C;

[0045] (5) Prepare 12% oxalic acid solution and seal the solution into individual bags.

[0046] When preparing sand molds, add part A of the binder to the raw sand at 6.5% of the weight of the sand used, and mix the sand evenly. Then, add part B of the oxalic acid solution to the mixed raw sand at 0.5% of the weight of the sand used, mix again, and prepare the sand mold.

[0047] The hardening time of the sand mold prepared by the above method varies according to the size of the sand mold. Taking the sand mold of castings of 1 to 2 tons as an example, the average hardening time of the original binder is 210 minutes, and the average hardening time after using the present binder is 160 minutes, which is about 30% shorter than the original hardening time. After CO2 hardening, the room temperature compressive strength can reach 2.85MPa. After the hardened sand mold is placed for 72 hours, there is no white frost, powdering or cracking on the surface. The residual strength of the sand mold at room temperature after casting is low, which is 0.88MPa, and the disintegration is good. The labor intensity of sand cleaning of castings is reduced.

[0048] Example 2

[0049] A sand mold binder for steel casting, comprising part A (sodium silicate, water, rice bran, and an activator, sodium lauryl sulfate) and part B (oxalic acid and water), wherein the specific components of each part are in the following proportions by weight:

[0050] Part A: Sodium silicate: 50%; Water: 48%; Rice bran: 1.7%; Sodium lauryl sulfate: 0.3%.

[0051] Part B: Oxalic acid: 15%; Water: 85%.

[0052] The sodium silicate modulus is 3.35, the rice bran is in a 300-mesh powder, and the rice bran is a mixed bran of rice and corn, each accounting for 50%. The specific preparation method is carried out according to the following steps:

[0053] (1) Put the anhydrous sodium silicate powder into the container, then pour water into the container to fully dissolve the sodium silicate into a viscous liquid with a density of 1.55g / cm 3 , then seal and place at 20℃~25℃ for 30h;

[0054] (2) adding an 8% aqueous solution of sodium lauryl sulfate as an active agent to the viscous liquid and stirring the solution uniformly; the 8% aqueous solution of sodium lauryl sulfate is prepared by dissolving 0.3% of sodium lauryl sulfate in part A in water;

[0055] (3) putting rice bran into water at 60° C. to 70° C. and stirring for 80 minutes to obtain a rice bran paste, wherein the ratio of rice bran to water in the paste is 1:3.5 by weight;

[0056] (4) adding the rice bran paste to the liquid in (2) and stirring evenly, and then sealing and placing in an environment of 15 to 30°C;

[0057] (5) Prepare 15% oxalic acid solution and seal the solution into individual bags.

[0058] When preparing sand molds, add part A of the binder to the raw sand at 7.5% of the weight of the sand used, and mix the sand evenly. Then, add part B of the oxalic acid solution to the mixed raw sand at 0.7% of the weight of the sand used, mix again, and prepare the sand mold.

[0059] The hardening time of the sand mold prepared by the above method varies according to the size of the sand mold. Taking the sand mold with a casting of 3 to 5 tons as an example, the average hardening time of the original binder is 520 minutes. After using the present binder, the average hardening time is 390 minutes, which is about 25% shorter than the original hardening time. After CO2 hardening, the room temperature compressive strength can reach 2.65MPa. After the hardened sand mold is placed for 72 hours, there is no white frost, powdering or cracking on the surface. The residual strength of the sand mold at room temperature after casting is low, which is 0.85MPa. The collapsibility is good, and the labor intensity of sand cleaning of the casting is reduced.

[0060] Example 3

[0061] A sand mold binder for steel casting, comprising part A (sodium silicate, water, rice bran, and an activator, sodium lauryl sulfate) and part B (oxalic acid and water), wherein the specific components of each part are in the following proportions by weight:

[0062] Part A: Sodium silicate: 55%; Water: 42%; Rice bran: 2.6%; Sodium lauryl sulfate: 0.4%.

[0063] Part B: Oxalic acid: 18%; Water: 82%.

[0064] The sodium silicate modulus is 3.34, the rice bran is in a powdery form of not less than 350 meshes, and the rice bran is a mixed bran of rice bran, corn bran, and wheat bran, each accounting for one-third. The specific preparation method is carried out according to the following steps:

[0065] (1) Put anhydrous sodium silicate powder into a container, then pour water into the container to fully dissolve the sodium silicate into a viscous liquid with a density of 1.52 g / cm 3 , then sealed and placed in an environment of 25-30℃ for 32h;

[0066] (2) adding a 9% aqueous solution of sodium lauryl sulfate as an active agent to the viscous liquid and stirring the solution uniformly; the 9% aqueous solution of sodium lauryl sulfate is prepared by dissolving 0.4% of sodium lauryl sulfate in part A in water;

[0067] (3) putting rice bran into water at 70° C. to 75° C. and stirring for 90 minutes to obtain a rice bran paste, wherein the ratio of rice bran to water in the paste is 1:4 by weight;

[0068] (4) adding the rice bran paste to the liquid in (2) and stirring evenly, and then sealing and placing in an environment of 15 to 30°C;

[0069] (5) Prepare oxalic acid into an 18% aqueous solution and seal the solution into individual bags.

[0070] When preparing sand molds, add the binder to the raw sand at 8% of the weight of the sand used, and mix the sand evenly. Then, add oxalic acid solution to the mixed raw sand at 0.8% of the weight of the sand used, mix again, and prepare the sand mold.

[0071] The hardening time of the sand mold prepared by the above method varies according to the size of the sand mold. Taking the sand mold with a casting of 0.5 to 1 ton as an example, the average hardening time of the original binder is 110 minutes. After using the present binder, the average hardening time is 72 minutes, which is about 35% shorter than the original hardening time. After CO2 hardening, the room temperature compressive strength can reach 2.76MPa. After the hardened sand mold is placed for 72 hours, there is no white frost, powdering or cracking on the surface. The residual strength of the sand mold at room temperature after casting is low, which is 0.82MPa, and the collapsibility is good. The labor intensity of cleaning the casting sand is reduced.

Claims

1. A sand mold binder for steel casting, characterized in that: The binder consists of two parts, A and B. Part A includes sodium silicate, water, rice bran, and sodium lauryl sulfate, and part B includes oxalic acid and water. The specific components of parts A and B are proportioned by weight as follows: Part A: Sodium silicate: 40%-60%; Water: 38%-55%; Rice bran: 0.5%-3%; Sodium lauryl sulfate: 0.2%-1.0%; Part B: Oxalic acid: 10%-20%; Water: 80%-90%; First, add part A of the binder to the raw sand in an amount of 5% to 10% of the weight of the raw sand. After mixing, add part B of the binder, an oxalic acid aqueous solution, to the raw sand mixed with the binder in an amount of 0.2% to 1.0% of the weight of the raw sand. After mixing, the preparation of the sand mold or sand core is completed.

2. The sand mold binder for steel casting according to claim 1, characterized in that The modulus of the sodium silicate is 3.1 to 3.

4.

3. The sand mold binder for steel casting according to claim 1, characterized in that: The rice bran is in a powdery form with a mesh size of not less than 200.

4. The sand mold binder for steel casting according to claim 3, characterized in that: The rice bran is one or more of rice bran, corn bran and wheat bran.

5. A method for preparing the sand mold binder for steel casting according to claim 1, characterized in that: Includes the following: Part A: According to sodium silicate: 40% to 60%; Water: 38% to 55%; Rice bran: 0.5%-3%; Sodium lauryl sulfate: 0.2% to 1.0% component ratio for preparation; ① Dissolve anhydrous sodium silicate powder in water to form a viscous liquid with a density of 1.45-1.72 g / cm 3 , then seal and place in an environment of 15-30℃ for 24-36h; ② Add 5% to 10% sodium lauryl sulfate aqueous solution to liquid ① and stir evenly; ③ Put rice bran into water at 50-80°C and stir for 60-100 minutes to obtain a paste, wherein the ratio of rice bran to water in the paste is 1:(3-5) by weight; ④Add the paste in ③ to the liquid in ② and stir evenly, then seal and place in an environment of 15-30℃; Part B: ⑤ Prepare oxalic acid into a 10% to 20% aqueous solution and seal it for later use as an additional regulator.

6. The method for preparing a sand mold binder for steel casting according to claim 5, wherein: The 5% to 10% sodium lauryl sulfate aqueous solution in Part A② is prepared by dissolving sodium lauryl sulfate in water.