KR desulfurization stirring paddle casting material and preparation method therefor

Abstract

Provided are a Kanbara Reactor (KR) desulfurization stirring paddle casting material and a preparation method therefor. The casting material consists of a base material and an additive; the base material consists of the following raw materials in weight percentages: M70 sintered mullite 60-80%, flint clay 5-20%, fine powder 5-20%, and pure calcium aluminate cement 1-5%. The percentages of each component of the additive based on the weight of the base material are as follows: water reducing agent 0.05-0.2%, and heat-resistant stainless steel fiber 1-5%. The main raw materials are M70 sintered mullite and a small amount of flint clay so as to ensure good thermal shock resistance; the medium temperature and high temperature strength are controlled at 100-180 MPa so as to ensure good erosion resistance; the content of Al.sub.2O.sub.3 in the casting material is 60-70% so as to ensure good corrosion resistance; the ratio of high temperature strength to medium temperature strength is controlled at 1-1.2, which further improves the thermal shock resistance and peeling resistance of the casting material, thereby extending the service life of the stirring paddle. The casting material is lower in cost and has a good practical furnace usage effect; in addition, a paddle blade has less chance of cracking and peeling, while a bottom portion of the stirring paddle is less eroded, thus the frequency of paddle blade repair is low, and service life is significantly improved.

Claims

1. A casting material for a stirring paddle for KR desulfurization, consisting of a base material of the casting material and additives, wherein the base material of the casting material consists of the following ingredients by weight percentage: 60-80% of M70 sintered mullite, 5-20% of flint clay, 5-20% of micropowder, and 1-5% of pure calcium aluminate cement; and wherein the additives consist of, by weight percentage based on the weight of the base material of the casting material: 0.05-0.2% of a water reducing agent, and 1-5% of a heat-resistant stainless steel fiber.

2. The casting material for a stirring paddle for KR desulfurization according to claim 1, wherein the base material for the casting material has an Al.sub.2O.sub.3 content of 60-70%.

3. The casting material for a stirring paddle for KR desulfurization according to claim 1, wherein the M70 sintered mullite has an Al.sub.2O.sub.3 content of 70% or more.

4. The casting material for a stirring paddle for KR desulfurization according to claim 1, wherein the flint clay has an Al.sub.2O.sub.3 content of 43% or more.

5. The casting material for a stirring paddle for KR desulfurization according to claim 1, wherein the micropowder is a silica micropowder and/or an alumina micropowder.

6. The casting material for a stirring paddle for KR desulfurization according to claim 1, wherein the pure calcium aluminate cement has an Al.sub.2O.sub.3 content of 70% or more.

7. A method for preparing the casting material for a stirring paddle for KR desulfurization according to claim 1 comprising: weighing the base material of the casting material and the additives according to the proportions, and mixing uniformly.

8. The method according to claim 7, wherein the base material for the casting material has an Al.sub.2O.sub.3 content of 60-70%.

9. The method according to claim 7, wherein the M70 sintered mullite has an Al.sub.2O.sub.3 content of 70% or more.

10. The method according to claim 7, wherein the flint clay has an Al.sub.2O.sub.3 content of 43% or more.

11. The method according to claim 7, wherein the micropowder is a silica micropowder and/or an alumina micropowder.

12. The method according to claim 7, wherein the pure calcium aluminate cement has an Al.sub.2O.sub.3 content of 70% or more.

Description

DETAILED DESCRIPTION

(1) The ingredients in the proportions as shown in Table 1 were weighed to obtain the base materials for the casting materials of Examples 1-3 and Comparative Examples 1-5; and then 0.12% of a water-reducing agent (sodium tripolyphosphate) and 3% of 446# heat-resistant stainless steel fiber based on the base materials for the casting materials were added to Examples 1-3 and Comparative Examples 1-5, respectively. After uniform mixing, the casting materials for stirring paddles for KR desulfurization in Examples 1-3 and Comparative Examples 1-5 were obtained, respectively.

(2) TABLE-US-00001 TABLE 1 Proportions of the ingredients of the base materials for the casting materials (wt %) Comp. Ex. Comp. Ex. Comp. Ex. Comp. Ex. Comp. Ex. Ingredient Ex. 1 Ex. 2 Ex. 3 1 2 3 4 5 M70 sintered 72 79 75 58.5 40 50 62 50 mullite Flint clay 15  8 10 10 30 / 10 10 Specail grade / / / 10 / 25 / 10 bauxite SiC / / / / 5 / 8 / Andalusite / / / 10 10 10 10 10 Kyanite / / / 3.5 3.5 3.5 3.5 3.5 Micropowder 10 10 12.5 5 8 8 8 13 Pure calcium  3  3 2.5 3 3.5 3.5 3.5 3.5 aluminate cement

(3) In Table 1,

(4) M70 sintered mullite has an Al.sub.2O.sub.3 content of about 70%.

(5) Flint clay has an Al.sub.2O.sub.3 content of about 43%.

(6) The micropowder is a blend of silica micropowder (having a SiO.sub.2 content of about 92% and a particle size of 1 μm) and alumina micropowder (having a Al.sub.2O.sub.3 content of about 99% and a particle size of 3 μm) in a mass ratio of 1:1.

(7) Pure calcium aluminate cement has an Al.sub.2O.sub.3 content of about 70%.

(8) The heat-resistant stainless steel fiber may be 446 # heat-resistant stainless steel fiber, etc.

(9) In the present disclosure, the Al.sub.2O.sub.3 content refers to the weight percentage of Al.sub.2O.sub.3.

(10) Performance tests were performed on the casting materials of Examples 1-3 and Comparative Examples 1-5 for stirring paddles for KR desulfurization. The test results are shown in Table 2.

(11) TABLE-US-00002 TABLE 2 Performance test results of casting materials Comp. Comp. Comp. Comp. Ex. Comp. Ex. Test item Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 3 4 5 Al.sub.2O.sub.3 content in 65.3% 68.2% 66.9% 66.5% 56.2% 71.3% 62.8% 67.9% casting material Medium temperature 124.4 135.6 158.2 83.5 131.7 132.0 156.4 132.0 strength, MPa High temperature 118.5 144.1 173.5 89.1 138.3 149.8 149.1 190.1 strength, MPa Strength ratio 0.95 1.06 1.10 1.07 1.05 1.14 0.95 1.44 Thermal shock Few Few Few More More More More large More large resistance, water small small small small small large cracks, few cracks, few cooling for 35 times cracks cracks cracks cracks cracks cracks spallings spallings Erosion resistance 104 100 103 106 118 106 101 105 index

(12) Table 2 lists the performances of the Examples and Comparative Examples. The intermediate temperature strength and high temperature strength are compressive strength after firing at 1000° C. for 3 hours (inspection standard GB/T 5072.1-1998) and compressive strength after firing at 1400° C. for 3 hours, respectively. The strength ratio is a ratio of the compressive strength after firing at 1400° C. for 3 hours to the compressive strength after firing at 1000° C. for 3 hours. The thermal shock resistance (inspection standard YB/T 2206.2-1998) is determined by observing the cracking of a sample after water cooling from 1100° C. for 35 times. The erosion resistance index is based on Example 2. The larger the value, the worse the erosion resistance.

(13) It can be seen that the comprehensive performances of the Examples were better. Among the Comparative Examples, the medium temperature strength and high temperature strength of Comparative Example 1 were relatively low. The erosion resistance of Comparative Example 2 was poor due to the addition of a relatively large amount of flint clay. The thermal shock resistance of Comparative Example 3 was poor due to a relatively large content of special grade bauxite. Because Comparative Example 4 contained a relatively large amount of SiC, its thermal shock resistance was poor. Due to the unduly large strength ratio, the thermal shock resistance of Comparative Example 5 was also poor.

(14) Examples 1-3 according to the present disclosure improved the comprehensive performances of the casting materials for stirring paddles. Particularly, they had both superior thermal shock resistance, and good resistance to scouring from molten steel and erosion from the desulfurizing agent, thus helpful for extending the service life of the stirring paddles.

(15) The effects of Example 2 in use are compared with that of Comparative Example 2. The results are shown in Table 3.

(16) TABLE-US-00003 TABLE 3 Effects in use in real furnaces Comp. Item Ex. 2 Ex. 2 Cost of casting 8% lower / material Cracking and Little More spalling of blade Bottom erosion of Little More stirring paddle Frequency of Low High blade repair Service life of Increased / stirring paddle by 12%

(17) Compared with Comparative Example 2, the cost of the casting material of Example 2 was reduced by 8%, and the service life of the stirring paddle was increased by 12%.