CN115627421A - Continuous casting method for eliminating net cracks of Ni-free 09CrCuSb steel casting blank - Google Patents

Abstract

The invention relates to a continuous casting method for eliminating net cracks of a Ni-free 09CrCuSb steel casting blank. The steel comprises the following chemical components, by weight, 0.06% -0.10% of C, 0.20% -0.35% of Si, 0.45% -0.60% of Mn, 0.020% or less of P, 0.010% or less of S, 0.80% -1.00% of Cr, 0.25% -0.35% of Cu, and 0.04% -0.10% of Sb; the key process steps are as follows: (1) When molten steel flows into a crystallizer from a tundish, controlling the water quantity of the crystallizer within 158 to 160t/h, and adopting the electromagnetic stirring parameters of the crystallizer to be 450A current and 3Hz frequency; (2) When a casting blank continuously cast from the crystallizer enters a secondary cooling chamber, the secondary cooling specific water amount is 1.19 to 1.21; (3) And controlling the blank temperature range of the casting blank to be 1100-1200 ℃ when the casting blank pulled out from the secondary cooling chamber enters a withdrawal and straightening machine. The method realizes the elimination of the net cracks on the surface and the corners of the casting blank, improves the quality of the casting blank and greatly reduces the probability of the occurrence of rolled rotten steel.

Description

Continuous casting method for eliminating net cracks of non-Ni 09CrCuSb steel casting blank

Technical Field

The invention belongs to the technical field of metallurgy, and relates to a continuous casting method for eliminating net cracks of a non-Ni 09CrCuSb steel casting blank.

Background

The 09CrCuSb steel contains Cr, cu and Sb elements, and the elements are easy to react firstly to form a passive film on the surface of the steel in the service process of a sulfuric acid environment to prevent the corrosion reaction from proceeding, so the 09CrCuSb steel has excellent sulfuric acid low-temperature dew point corrosion resistance and is widely applied to the manufacture of equipment such as coal-fired boilers, oil-fired boilers, coolers, evaporators and the like. However, the 09CrCuSb steel contains Cr, cu and Sb elements, particularly Cu elements, so that a casting blank is easy to generate a net crack defect in the continuous casting process. In order to eliminate the network cracks, ni is generally added to steel to combine Ni — Cu to form a high-melting-point composite phase, thereby reducing free Cu in the steel, suppressing Cu segregation to grain boundaries, and eliminating the network cracks. And if Ni is added, the production cost of the 09CrCuSb steel can be greatly increased.

Disclosure of Invention

The invention aims to provide a continuous casting method for eliminating net cracks of a Ni-free 09CrCuSb steel casting blank, which can inhibit the precipitation of Cu on the surface layer of the casting blank, greatly improve the plasticity of the casting blank, and eliminate the net cracks on the surface and the corner of the casting blank so as to improve the quality of the casting blank.

The technical scheme of the invention is as follows:

the continuous casting method for eliminating the net cracks of the non-Ni 09CrCuSb steel casting blank comprises the following steps of (by weight percent) C =0.06% -0.10%, si =0.20% -0.35%, mn =0.45% -0.60%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, cr =0.80% -1.00%, cu =0.25% -0.35%, and Sb =0.04% -0.10%; the key process steps are as follows:

(1) When molten steel flows into the crystallizer from the tundish, controlling the water quantity of the crystallizer within 158 to 160t/h, and electromagnetically stirring the crystallizer for 450A at a frequency of 3Hz;

(2) When the casting blank continuously cast from the crystallizer reaches a secondary cooling chamber, the secondary cooling specific water amount is 1.19 to 1.21;

(3) And controlling the blank temperature range of the casting blank to be 1100-1200 ℃ when the casting blank pulled out from the secondary cooling chamber enters a withdrawal and straightening machine.

The steel continuous casting process flow and principle are as follows: the molten steel flows to a crystallizer from the tundish, and a casting blank with a certain thickness of an initial blank shell is formed in the crystallizer at a certain drawing speed through cooling of water of the crystallizer, stirring of electromagnetic stirring of the crystallizer, and lubrication and heat transfer of covering slag; in the process of drawing, the casting blank is drawn out from the crystallizer into a secondary cooling chamber, and the temperature of the casting blank is further reduced under the cooling action of secondary cooling water in the secondary cooling chamber; the casting blank pulled out from the secondary cooling chamber is straightened into a casting blank in the horizontal direction through the blank drawing and straightening functions of the withdrawal and straightening machine; the casting blank in the horizontal direction is cut into a continuous casting blank through the fixed length cutting of the flame cutter. The key process steps are as follows: the forming stage of a primary blank shell in a crystallizer, the cooling stage of a casting blank in a secondary cooling chamber and the drawing and straightening stages of the casting blank when the casting blank passes through a withdrawal and straightening machine.

The outstanding characteristics and the obvious effects of the invention are mainly reflected in that:

1) The 09CrCuSb steel contains Cr, cu and Sb elements, particularly Cu elements, so that a casting blank is easy to generate a net crack defect in the continuous casting process. In order to eliminate the network cracks, a method of adding Ni to steel is generally used, in which Ni — Cu is combined to form a high-melting-point composite phase, and free Cu in the steel is reduced, thereby suppressing the segregation of Cu to the grain boundary and eliminating the network cracks. And if Ni is added, the production cost of the 09CrCuSb steel can be greatly increased. The invention has the prominent characteristics that: ni is not added in the smelting process of 09CrCuSb steel, and the elimination of the net cracks on the surface and the corners of the casting blank is realized by improving the plasticity of the casting blank and inhibiting the precipitation of Cu on the surface layer of the casting blank in the continuous casting process.

2) According to industrial test verification, on the premise that the 09CrCuSb steel is not added with Ni, continuous casting parameters including crystallizer water amount of 158 to 160t/h, crystallizer electromagnetic stirring current of 450A, frequency of 3Hz and secondary cooling specific water amount of 1.19 to 1.21 are adopted, and when a temperature range of a withdrawal and straightening machine blank is 1100 to 1200 ℃, an off-line surface pickling result of a continuous casting blank shows that net cracks on the surface and the corner of the casting blank are eliminated, the defect of rolled rotted steel is reduced, and customer satisfaction is increased.

3) The invention eliminates the reticular cracks of the casting blank on the premise of not adding Ni in the 09CrCuSb steel, improves the quality of the casting blank, reduces the production cost of the 09CrCuSb steel and develops a new process for producing the 09CrCuSb steel product.

Detailed Description

The invention will be further described with reference to the following practical examples.

Example 1:

industrial tests were carried out on a 4-machine 4-strand continuous casting machine of a steel mill, the test steel grade being 09CrCuSb, the chemical composition of the steel being, by weight, C =0.08%, si =0.22%, mn =0.46%, P =0.014%, S =0.008%, cr =0.82%, cu =0.27%, sb =0.08%. Comparing the surface quality of the cast billet under the conditions of the original continuous casting process and the newly developed continuous casting process. The results show that: when the water quantity of the crystallizer is 160t/h, the electromagnetic stirring current of the crystallizer is 450A, the frequency is 3Hz, the secondary cooling specific water quantity is 1.20 and the blank temperature of a withdrawal and straightening unit is 1113 ℃, the net cracks of the continuous casting billet are eliminated, and under the condition of the original continuous casting technological parameters, the net cracks exist on the surface and the corner of the continuous casting billet.

Example 2:

the industrial test was carried out on a 4-machine 4-strand continuous casting machine of Hunan steel mill, the test steel grade was 09CrCuSb, and the steel had a chemical composition of, by weight, C =0.07%, si =0.21%, mn =0.48%, P =0.011%, S =0.006%, cr =0.91%, cu =0.31%, and Sb =0.06%. Comparing the surface quality of the cast blank under the original continuous casting process and the newly developed continuous casting process. The results show that: when the continuous casting parameters adopt the crystallizer water amount of 159t/h, the crystallizer electromagnetic stirring current of 450A, the frequency of 3Hz, the secondary cooling specific water amount of 1.19 and the billet temperature of a withdrawal and straightening unit of 1165 ℃, the reticular cracks of the continuous casting billet are eliminated, and under the condition of the original continuous casting technological parameters, the reticular cracks exist at the corners of the continuous casting billet.

Example 3:

the 4-machine 4-strand continuous casting machine of the Hunan steel mill is subjected to industrial tests, the test steel grade is 09CrCuSb, and the chemical compositions of the steel in percentage by weight are C =0.09%, si =0.32%, mn =0.50%, P =0.014%, S =0.003%, cr =0.81%, cu =0.26%, and Sb =0.07%. Comparing the surface quality of the cast blank under the original continuous casting process and the newly developed continuous casting process. The results show that: when the water quantity of the crystallizer is 158t/h, the electromagnetic stirring current of the crystallizer is 450A, the frequency is 3Hz, the secondary cooling specific water quantity is 1.21 and the blank temperature of a withdrawal and straightening unit is 1139 ℃ in continuous casting parameters, the net cracks of the continuous casting blank are eliminated, and under the condition of the original continuous casting process parameters, the net cracks exist on the face part and the corner part of the continuous casting blank.

Claims (1)

1. A continuous casting method for eliminating net cracks of a non-Ni 09CrCuSb steel casting blank is characterized by comprising the following steps: the steel comprises the following chemical components, by weight, 0.06% -0.10% of C, 0.20% -0.35% of Si, 0.45% -0.60% of Mn, 0.020% or less of P, 0.010% or less of S, 0.80% -1.00% of Cr, 0.25% -0.35% of Cu, and 0.04% -0.10% of Sb; the key process steps are as follows:

(1) When molten steel flows into the crystallizer from the tundish, controlling the water quantity of the crystallizer within 158 to 160t/h, and electromagnetically stirring the crystallizer for 450A at a frequency of 3Hz;

(2) When the casting blank continuously cast from the crystallizer reaches a secondary cooling chamber, the secondary cooling specific water amount is 1.19 to 1.21;

(3) And controlling the blank temperature range of the casting blank to be 1100-1200 ℃ when the casting blank pulled out from the secondary cooling chamber enters a withdrawal and straightening machine.