CN102408242A - Composite ceramic block for hot-rolled walking heating furnace and preparation method thereof - Google Patents

Abstract

The invention relates to a composite ceramic cushion block for a hot rolling stepping heating furnace and a preparation method thereof. The preparation steps are as follows: taking 25-75 wt% of Si powder and 75-25 wt% of SiC powder as raw materials, and taking 3-8 wt% of sintering aid and 3-5 wt% of bonding agent as additives; mixing the raw materials with a sintering aid, drying, uniformly mixing the dried mixed powder with a binding agent, forming, and carrying out isostatic pressing treatment to obtain a biscuit; preserving heat of the biscuit for 1-30 h at 1280-1410 ℃ in nitrogen atmosphere, continuously heating to 1450-1700 ℃ in nitrogen atmosphere, and preserving heat for 3-8 h to obtain a nitriding sintered blank; and impregnating the nitrided and sintered blank with silicon under the conditions that the temperature is 1700-1850 ℃ and the vacuum degree is less than 100Pa, wherein the treatment time is 2-20 hours, and machining the prepared blank. The invention has simple process and low cost, and the product has the characteristics of high temperature resistance, good creep resistance, small heat conductivity coefficient, good thermal shock resistance, wear resistance and high-temperature strength.

Description

Composite ceramic block for hot-rolled walking heating furnace and preparation method thereof

technical field

The invention belongs to the technical field of composite ceramics, and in particular relates to a composite ceramic cushion block for a hot-rolled walking heating furnace and a preparation method thereof.

Background technique

At present, the pads on the water-cooled beams in the walking heating furnace of the hot rolling mill of the metallurgical industry are made of heat-resistant alloy steel. Due to the congenital defects of high thermal conductivity, high-temperature creep and oxidative damage in heat-resistant steel, it is easy to cause being heated Problems such as "deviation" of the steel billet and "water-cooling scar" (black mark) on the contact part with the block, which affect the quality of the rolled material, have become the "bottleneck" problems restricting the production of high-tech steel products such as hot-rolled sheets; at the same time, "water-cooling "Scar" ("black mark") is low in temperature, which reduces the thermoplasticity and ductility of the steel billet, making the steel prone to rolling cracks and producing "waste material", especially for the production of high-grade oriented silicon steel, and for ultra-thin plates even Unable to roll.

In order to solve the problem of "water-cooling scar" (black mark) in the contact part between the heated billet and the block, the method of increasing the heating temperature and prolonging the heating time is usually used at this stage to ensure that the billet achieves proper thermoplasticity and ductility. This method is obvious. There are problems of high energy consumption, large amount of billet ablation, slow production speed and low efficiency, and the heat-resistant steel pads will be "squeezed" and damaged due to high temperature creep, causing the heated billet to "deviate" and affect Normal production of heating furnace. It has become one of the most urgent tasks for the steel rolling industry to develop a new type of ceramic block with good high temperature resistance and creep resistance, low thermal conductivity and high strength as soon as possible to replace the currently used alloy steel block and effectively solve the above problems.

Contents of the invention

The present invention aims to overcome the defects of the prior art: the purpose is to provide a method for preparing a composite ceramic block for a hot-rolled walking heating furnace with simple process and low cost, and the composite ceramic block prepared by the method is resistant to high temperature, It has good creep resistance, small thermal conductivity, good thermal shock resistance, wear resistance and high temperature strength, which can effectively solve the problem of "water cooling scar" at the contact part between the heated billet and the block.

To achieve the above object, the present invention adopts the following technical steps:

(1) Ingredients: 25-75wt% of Si powder and 75-25wt% of SiC powder are used as raw materials, 3-8wt% of the above-mentioned sintering aid and 3-5wt% of the above-mentioned binder are used as admixtures;

Among them: the sintering aid is Y ₂ O ₃ , or a mixture of Y ₂ O ₃ and Al ₂ O ₃ ; the binder is phenolic resin, or polyethylene glycol;

(2) Mixing: mix the raw materials in step (1) and the sintering aid in the admixture according to their respective percentages in a dry method, or mix them with absolute ethanol as a wet mixing medium, and dry them after mixing evenly. A dried mixed powder is obtained;

(3) Molding: mix the binder in the admixture in the step (1) according to its percentage content with the dried mixed powder evenly, and carry out dry pressing molding; get bisque;

(4) Sintering: The green body is first kept in a nitrogen atmosphere at 1280-1410°C for 1-30 hours, then continues to heat up to 1450-1700°C in a nitrogen atmosphere, and keeps it for 3-8 hours to obtain a nitrided sintered body ;

(5) Silicon impregnation treatment: the nitrided sintered compact is subjected to silicon impregnation treatment at a temperature of 1700-1850°C and a vacuum degree of less than 100Pa, and the treatment time is 2-20 hours to obtain a blank;

(6) Machining the blank to prepare a composite ceramic pad for a hot-rolled walking heating furnace.

In the above technical scheme: the purity of Si powder is ≥95wt%, and the particle size is less than 0.1mm; the purity of SiC powder is ≥90wt%, and the particle _size is less than 5mm; the purity of _Y2O3 is ≥95wt%, and the purity of _{Al2O3 is} ≥95wt% ; The particle size of Y ₂ O ₃ and Al ₂ O ₃ is less than 0.005mm; the pressure of dry pressing is 5-20 MPa, and the pressure of isostatic pressing is 50-400 MPa.

Compared with the prior art, the present invention has the following main advantages:

The preparation method is simple in process and low in cost, and the Si ₃ N ₄ -SiC composite ceramic block prepared by high-temperature vacuum impregnated silicon treatment has high temperature resistance, good creep resistance, small thermal conductivity, good thermal shock resistance, and High wear and high temperature strength, can replace Co40 or Co60 heat-resistant alloy steel to make ceramic pads for water-cooled beams of heating furnaces, can meet the requirements of hot rolling production, and can effectively solve the problem of "water cooling" in the contact part between the heated billet and the pad. Scar” (black mark) issue.

Detailed ways

In order to avoid repetition, the technical parameters involved in this specific embodiment are described as follows: the purity of Si powder is ≥95wt%, and the particle size is less than 0.1mm; the purity of SiC powder is ≥90wt%, and the particle size is less than _5mm ; the purity of _Y2O3 ≥95wt%, the purity of Al ₂ O ₃ is ≥95wt%; the particle size of Y ₂ O ₃ and Al ₂ O ₃ is less than 0.005mm; the pressure of dry pressing is 5-20MPa, and the pressure of isostatic pressing is 50-400MPa.

In order to better understand the present invention, the present invention will be further described below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

Example 1

A composite ceramic cushion block for a hot-rolled walking heating furnace and a preparation method thereof. Its preparation steps are as follows:

(1) Ingredients: 25-37wt% Si powder and 63-75wt% SiC powder are used as raw materials, and 3-5wt% _Y2O3 and 3-4wt% polyethylene glycol are added as raw _materials . agent;

(2) Mixing: the raw materials in step (1) and Y ₂ O ₃ are mixed according to their respective percentages with absolute ethanol as a wet mixing medium, and dried after mixing evenly to obtain a dried mixed powder;

(3) Forming: mix the polyethylene glycol in the step (1) according to its percentage content with the dried mixed powder evenly, and carry out dry pressing; then carry out isostatic pressing to the formed mixture to obtain plain Blank;

(4) Sintering: The green body is first kept in a nitrogen atmosphere at 1350-1410 °C for 1-4 hours, and then continues to heat up to 1450-1500 °C in a nitrogen atmosphere, and is kept for 3-4 hours to obtain a nitrided sintered body ;

(5) Silicon impregnation treatment: the nitrided sintered compact is subjected to silicon impregnation treatment at a temperature of 1750-1800°C and a vacuum degree of less than 10Pa, and the treatment time is 15-20 hours to obtain a blank;

(6) Machining the blank to prepare a composite ceramic pad for a hot-rolled walking heating furnace.

Example 2

A composite ceramic cushion block for a hot-rolled walking heating furnace and a preparation method thereof. Its preparation steps are as follows:

(1) Ingredients: 37-45wt% Si powder and 55-63wt% SiC _powder are used as raw materials, and 3-5wt% _Y2O3 and 3-4wt% polyethylene glycol are added as raw materials. agent;

(2) Mixing: the raw materials in step (1) and Y ₂ O ₃ are mixed according to their respective percentages with absolute ethanol as a wet mixing medium, and dried after mixing evenly to obtain a dried mixed powder;

(3) Forming: mix the polyethylene glycol in the step (1) according to its percentage content with the dried mixed powder evenly, and carry out dry pressing; then carry out isostatic pressing to the formed mixture to obtain plain Blank;

(4) Sintering: first heat the biscuit in a nitrogen atmosphere and at 1350-1410°C for 10-15 hours, then continue to heat up to 1600-1650°C in a nitrogen atmosphere, and keep it for 3-4 hours to obtain a nitrided sintered compact ;

(5) Silicon impregnation treatment: the nitrided sintered compact is subjected to silicon impregnation treatment at a temperature of 1800-1850° C. and a vacuum degree of 30-50 Pa, and the treatment time is 10-15 hours to obtain a blank;

(6) Machining the blank to prepare a composite ceramic pad for a hot-rolled walking heating furnace.

Example 3

A composite ceramic cushion block for a hot-rolled walking heating furnace and a preparation method thereof. Its preparation steps are as follows:

(1) Ingredients: 45-55wt% of Si powder and 45-55wt% of SiC powder are used as raw materials, 5-8wt% of the above-mentioned sintering aid and 3-4wt% of the above-mentioned polyethylene glycol are used as admixtures ; The sintering aid is a mixture of Y ₂ O ₃ and Al ₂ O ₃ with a mass ratio of 1:1;

(2) Mixing: mix the raw materials in step (1) and the sintering aid in the admixture according to their respective percentages with absolute ethanol as the wet mixing medium, and dry after mixing evenly to obtain a dried mixed Powder;

(3) Forming: mix the polyethylene glycol in the step (1) according to its percentage content with the dried mixed powder evenly, and carry out dry pressing; then carry out isostatic pressing to the formed mixture to obtain plain Blank;

(4) Sintering: The green body is first kept in a nitrogen atmosphere at 1350-1410°C for 4-8 hours, and then continues to heat up to 1600-1650°C in a nitrogen atmosphere, and is kept for 6-8 hours to obtain a nitrided sintered body ;

(5) Silicon impregnation treatment: the nitrided sintered compact is subjected to silicon impregnation treatment at a temperature of 1800-1850°C and a vacuum degree of 50-100Pa, and the treatment time is 8-10 hours to obtain a blank;

(6) Machining the blank to prepare a composite ceramic pad for a hot-rolled walking heating furnace.

Example 4

A composite ceramic cushion block for a hot-rolled walking heating furnace and a preparation method thereof. Its preparation steps are as follows:

(1) Ingredients: 55-60wt% Si powder and 40-45wt% SiC powder are used as raw materials, _3-5wt % _Y2O3 and 4-5wt% phenolic resin are used as admixtures;

(2) Mixing: the raw materials in step (1) and Y ₂ O ₃ are mixed according to their respective percentages with absolute ethanol as a wet mixing medium, and dried after mixing evenly to obtain a dried mixed powder;

(3) Molding: the phenolic resin in the step (1) is mixed evenly with the mixed powder after drying according to its percentage content, and then dry-pressed; then the molded mixture is subjected to isostatic pressing to obtain a green body;

(4) Sintering: The green body is first kept in a nitrogen atmosphere at 1350-1410°C for 20-30 hours, then continued to heat up to 1600-1650°C in a nitrogen atmosphere, and kept for 3-5 hours to obtain a nitrided sintered body ;

(5) Silicon impregnation treatment: perform silicon impregnation treatment on the nitrided sintered blank at a temperature of 1700-1750°C and a vacuum degree of less than 10-30Pa, and the treatment time is 15-20 hours to obtain a blank;

(6) Machining the blank to prepare a composite ceramic pad for a hot-rolled walking heating furnace.

Example 5

A composite ceramic cushion block for a hot-rolled walking heating furnace and a preparation method thereof. Its preparation steps are as follows:

(1) Ingredients: 25-37wt% of Si powder and 63-75wt% _of SiC powder are used as raw materials, and 5-8wt% of _Y2O3 and 3-4wt% of the above-mentioned raw materials are added as polyethylene glycol agent;

(2) Mixing: the raw materials in step (1) and Y ₂ O ₃ are mixed according to their respective percentages with absolute ethanol as a wet mixing medium, and dried after mixing evenly to obtain a dried mixed powder;

(3) Forming: mix the polyethylene glycol in the step (1) according to its percentage content with the dried mixed powder evenly, and carry out dry pressing; then carry out isostatic pressing to the formed mixture to obtain plain Blank;

(4) Sintering: The green body is first kept in a nitrogen atmosphere at 1350-1410°C for 10-15 hours, then continued to heat up to 1650-1700°C in a nitrogen atmosphere, and kept for 5-8 hours to obtain a nitrided sintered body ;

(5) Silicon impregnation treatment: perform silicon impregnation treatment on the nitrided sintered blank at a temperature of 1750-1800°C and a vacuum degree of less than 30-50Pa, and the treatment time is 15-20 hours to obtain a blank;

(6) Machining the blank to prepare a composite ceramic pad for a hot-rolled walking heating furnace.

Example 6

A composite ceramic cushion block for a hot-rolled walking heating furnace and a preparation method thereof. Its preparation steps are as follows:

(1) Ingredients: 25-28wt% of Si powder and 72-75wt% of SiC powder are used as raw materials, 5-8wt% of _the above-mentioned _Y2O3 sintering aid and 3-4wt% of the above-mentioned polyethylene glycol Alcohol is an admixture;

(2) Mixing: the raw materials in step (1) and Y ₂ O ₃ are mixed according to their respective percentages with absolute ethanol as a wet mixing medium, and dried after mixing evenly to obtain a dried mixed powder;

(3) Forming: mix the polyethylene glycol in the step (1) according to its percentage content with the dried mixed powder evenly, and carry out dry pressing; then carry out isostatic pressing to the formed mixture to obtain plain Blank;

(4) Sintering: The green body is first kept in a nitrogen atmosphere at 1350-1410 °C for 15-20 hours, and then continues to heat up to 1500-1600 °C in a nitrogen atmosphere, and is kept for 3-5 hours to obtain a nitrided sintered body ;

(5) Silicon impregnation treatment: the nitrided sintered compact is subjected to silicon impregnation treatment at a temperature of 1700-1750°C and a vacuum degree of less than 10Pa, and the treatment time is 5-8 hours to obtain a blank;

(6) Machining the blank to prepare a composite ceramic pad for a hot-rolled walking heating furnace.

Example 7

A composite ceramic cushion block for a hot-rolled walking heating furnace and a preparation method thereof. Its preparation steps are as follows:

(1) Ingredients: 60-75wt% of Si powder and 25-40wt% of SiC powder are used as raw materials, 5-8wt% of the above-mentioned sintering aid and 3-4wt% of the above-mentioned phenolic resin are used as admixtures; The sintering aid is a mixture of Y ₂ O ₃ and Al ₂ O ₃ with a mass ratio of 1:1;

(2) Mixing: dry mixing the raw materials and sintering aids in step (1) according to their respective percentages to obtain mixed powder;

(3) Molding: the phenolic resin in the step (1) is uniformly mixed with the mixed powder according to its percentage content, and then dry-pressed; then the molded mixture is subjected to isostatic pressing to obtain a green body;

(4) Sintering: The green body is first kept in a nitrogen atmosphere at 1280-1350°C for 5-10 hours, then continued to heat up to 1600-1550°C in a nitrogen atmosphere, and kept for 5-8 hours to obtain a nitrided sintered body ;

(5) Silicon impregnation treatment: the nitriding sintered blank is subjected to silicon impregnation treatment under the conditions of a temperature of 1800-1850°C and a vacuum degree of 50-100Pa, and the treatment time is 2-5 hours to obtain a blank;

(6) Machining the blank to prepare a composite ceramic pad for a hot-rolled walking heating furnace.

This specific embodiment has simple process and low cost, and the Si ₃ N ₄ -SiC composite ceramic block prepared by high-temperature vacuum impregnated silicon treatment has high temperature resistance, good creep resistance, small thermal conductivity, good thermal shock resistance, With the characteristics of wear resistance and high temperature strength, it can replace Co40 or Co60 heat-resistant alloy steel to make ceramic pads for water-cooled beams in heating furnaces, which can meet the requirements of hot rolling production, and can effectively solve the problem of contact between the heated billet and pads. Water cooling scar" (black mark) problem.

Claims (6)

1. a hot rolling walking beam furnace is characterized in that adopting following steps with the preparation method of composite ceramics cushion block:

(1) batching: with the Si powder of 25～75wt% and the SiC powder of 75～25wt% is raw material, is admixture with the sintering aid of above-mentioned raw materials 3～8wt% and the wedding agent of above-mentioned raw materials 3～5wt%; Wherein: sintering aid is Y ₂O ₃, or be Y ₂O ₃And Al ₂O ₃Mixture; Wedding agent is resol or is polyoxyethylene glycol;

(2) batch mixing: is that the wet mixing medium mixes with the raw material in the step (1) and the sintering aid in the admixture with dry mixed or with the absolute ethyl alcohol by separately percentage composition, carries out drying after mixing, and makes dried mixed powder;

(3) moulding: the wedding agent in the admixture in the step (1) is mixed by its percentage composition and dried mixed powder, carry out dry-pressing formed; Mixture with moulding waits static pressure to handle again, makes biscuit;

(4) sintering: biscuit is incubated 1～30h at nitrogen atmosphere with under 1280～1410 ℃ of conditions earlier, under nitrogen atmosphere, continues to be warmed up to 1450 ℃～1700 ℃ again, insulation 3～8h makes nitridation sintered base;

(5) oozing stain silicon handles: with nitridation sintered base temperature be 1700～1850 ℃ with the condition of vacuum tightness less than 100Pa under ooze stain silicon and handle, the treatment time is 2～20 hours, makes blank;

(6) blank is carried out mechanical process, make the hot rolling walking beam furnace and use the composite ceramics cushion block.

2. hot rolling walking beam furnace according to claim 1 is characterized in that the purity >=95wt% of described Si powder with the preparation method of composite ceramics cushion block, and granularity is less than 0.1mm.

3. hot rolling walking beam furnace according to claim 1 is characterized in that the purity >=90wt% of described SiC powder with the preparation method of composite ceramics cushion block, and granularity is less than 5mm.

4. hot rolling walking beam furnace according to claim 1 is characterized in that described Y with the preparation method of composite ceramics cushion block ₂O ₃Purity>=95wt%, Al ₂O ₃Purity>=95wt%; Y ₂O ₃And Al ₂O ₃Granularity less than 0.005mm.

5. hot rolling walking beam furnace according to claim 1 is characterized in that with the preparation method of composite ceramics cushion block described dry-pressing formed pressure is 5～20MPa, and the pressure that waits static pressure to handle is 50～400MPa.

6. use the composite ceramics cushion block according to each described hot rolling walking beam furnace in the claim 1～5 with the prepared hot rolling walking beam furnace of the preparation method of composite ceramics cushion block.