CN112338157A

CN112338157A - Billet solidification forming process

Info

Publication number: CN112338157A
Application number: CN202011084209.2A
Authority: CN
Inventors: 程方波; 龚志翔; 高振波; 汪国才; 汪开忠; 李新; 陶承岗
Original assignee: Maanshan Iron and Steel Co Ltd
Current assignee: Maanshan Iron and Steel Co Ltd
Priority date: 2020-10-12
Filing date: 2020-10-12
Publication date: 2021-02-09

Abstract

The invention discloses a billet solidification forming process, which sequentially comprises the following steps: the method comprises the following steps of ladle casting, tundish casting, primary molding of a crystallizer, casting blank spray cooling, blank drawing straightening, cutting, slow cooling and annealing, wherein electric stirring and stirring are adopted in the primary molding stage of the crystallizer, and electromagnetic stirring is adopted at the initial end and the tail end of a casting flow in the stage from the spray cooling of the casting blank to the blank drawing straightening. The invention can generate

The round billet with the specification has good internal quality, the component uniformity of the casting billet in the central core defect area within the area range of the central point diameter of 60mm is very good, and the distribution conditions of C element, Mn element, Cr element, Mo element and W element are all within the control target range. The high-power inclusions of the rolled tube blank meet the product requirements,delta-ferrite did not appear.

Description

Billet solidification forming process

Technical Field

The invention relates to the technical field of forming of metallurgical industrial production, in particular to a production method of a seamless steel pipe blank P92 steel for an ultra-age generator set in a solidification process.

Background

At present, a high-efficiency, energy-saving and environment-friendly supercritical unit is developed in China, and a P92 pipe blank which is a key material is mainly imported from abroad and only has a small batch of die cast ingots in China to experimentally produce the material. The cast ingot production has the disadvantages of low yield, low purity of the billet, high content of [ H ], serious component segregation, coarse grains and the like. This steel type is a martensitic stainless steel, but due to the existence of segregation of the components, a large amount of δ -ferrite often appears in the metallographic structure.

The delta-ferrite in the steel pipe blank not only influences the toughness, plasticity, strength and welding performance of the rolled steel pipe, but also greatly reduces the fatigue life of the steel pipe. Therefore, the production of P92 billets with uniform and stable components is the key for controlling the structure of the steel pipe and ensuring the service performance of the steel pipe, but at present, a good control method is not provided, so that the quality of the product is difficult to ensure.

Disclosure of Invention

The invention aims to solve the technical problem of realizing a production process method, reducing segregation of components of a casting blank and refining grains by adopting a continuous casting process to replace a die casting process to improve the speed of solidification and forming, promoting the refining of the grains by assisting an electromagnetic stirring effect and reducing the center segregation, shrinkage cavity and crack defects of a blank. The components of the blank are completely avoided from a delta-ferrite area, and are stably controlled in a single martensitic stainless steel area.

In order to achieve the purpose, the invention adopts the technical scheme that: a steel billet solidification forming process sequentially comprises the following steps: the method comprises the following steps of ladle casting, tundish casting, primary molding of a crystallizer, casting blank spray cooling, blank drawing straightening, cutting, slow cooling and annealing, wherein electric stirring and stirring are adopted in the primary molding stage of the crystallizer, and electromagnetic stirring is adopted at the initial end and the tail end of a casting flow in the stage from the spray cooling of the casting blank to the blank drawing straightening.

The casting specification of the primary molding of the crystallizer is

The casting and pulling speed is 0.25-0.60 m/min.

The primary cooling speed in the casting blank spray cooling is as follows: 3000-5500l/min, secondary cooling water ratio: 0.15-0.25L/kg.

The cooling time of slow cooling is more than or equal to 48 hours, and the temperature of casting blank entering slow cooling is more than or equal to 600 ℃.

The parameters of each electromagnetic stirring are 2-15HZ and 200-1000A.

The straightening pressure for straightening the drawing blank is 10-60 t.

The casting blank is P92 steel.

The invention can generate

The round billet with the specification has good internal quality, the component uniformity of the casting billet is very good in the central core defect area within the area range of the central point diameter of 60mm, and the distribution conditions of C element, Mn element, Cr element, Mo element and W element are respectively shown in figures 2-6 and are all within the range of a control target (located in the martensite single area of the structure diagram of the Scheffler stainless steel welding metal). The high-power inclusions of the rolled tube blank meet the product requirements, and delta-ferrite does not appear, as shown in figures 7 and 8.

Drawings

The following is a brief description of the contents of each figure in the description of the present invention:

FIG. 1 is a flow chart of a billet solidification forming process;

FIG. 2 is a distribution diagram of C element in a casting blank

FIG. 3 is a distribution diagram of Mn element in a casting blank

FIG. 4 is a distribution diagram of Cr element in a casting blank

FIG. 5 is a distribution diagram of Mo element in casting blank

FIG. 6 is a distribution diagram of element W in a cast slab

Fig. 7 and 8 are metallographic structure diagrams of two samples of P92 steel pipes.

Detailed Description

The following description of the embodiments with reference to the drawings is provided to describe the embodiments of the present invention, and the embodiments of the present invention, such as the shapes and configurations of the components, the mutual positions and connection relationships of the components, the functions and working principles of the components, the manufacturing processes and the operation and use methods, etc., will be further described in detail to help those skilled in the art to more completely, accurately and deeply understand the inventive concept and technical solutions of the present invention.

The billet solidification forming process is shown in figure 1 and sequentially comprises ladle casting, tundish casting, primary forming of a crystallizer, casting blank spray cooling, casting blank electromagnetic stirring, tail end electromagnetic stirring, billet drawing straightening, cutting, slow cooling and annealing. Namely, a crystallizer electromagnetic stirrer is required to be arranged in a crystallizer at the initial molding stage of the crystallizer, a casting flow section is arranged between the casting blank spray cooling and the blank drawing straightening, and casting flow electromagnetic stirrers are arranged at the beginning end and the tail end of the casting flow section to realize three-section electromagnetic stirring (M-EMS + S-EMS + F-EMS).

In order to further improve the effect of the solidification forming process of the P92 blank, a round billet continuous casting machine is adopted for casting, so that the solidification speed of the P92 steel is rationalized, and the specific parameters are as follows:

casting specification:

casting and pulling speed: 0.25-0.60 m/min;

primary cooling speed: 3000-5500 l/min;

secondary cooling specific water amount: 0.15-0.25L/kg;

casting blank slow cooling temperature: more than or equal to 600 ℃;

slow cooling time: the time is more than or equal to 48 hours;

an electric stirring process: 2-15HZ 200-1000A;

straightening pressure: 10-60 t;

by the process, the component segregation of the steel billet can be reduced, the delta-ferrite in the structure is eliminated, three sections of electromagnetic stirring (M-EMS + S-EMS + F-EMS) are adopted to stir the solidification process of the casting blank, the center segregation, shrinkage cavity and crack defects of the casting blank are reduced, the continuous casting process is adopted to replace a die casting process, the core part loosening and shrinkage cavity defects of the casting blank are avoided by the casting blank slow cooling process, cracks are expanded in the cooling process, and the component stability control of the casting blank in a single martensite area is effectively realized.

The invention has been described above with reference to the accompanying drawings, it is obvious that the invention is not limited to the specific implementation in the above-described manner, and it is within the scope of the invention to apply the inventive concept and solution to other applications without substantial modification.

Claims

1. A steel billet solidification forming process sequentially comprises the following steps: ladle casting, pouring basket casting, crystallizer preliminary shaping, casting blank spray cooling, throwing straightening, cutting, slow cooling, annealing, its characterized in that: and in the primary forming stage of the crystallizer, electric stirring and stirring are adopted, and the casting blank is sprayed and cooled to the casting flow starting end and the casting flow tail end in the billet drawing and straightening stage and is stirred electromagnetically.

2. The steel billet solidification forming process according to claim 1, wherein: the casting specification of the primary molding of the crystallizer is

The casting and pulling speed is 0.25-0.60 m/min.

3. The steel billet solidification forming process according to claim 1, wherein: the primary cooling speed in the casting blank spray cooling is as follows: 3000-5500l/min, secondary cooling water ratio: 0.15-0.25L/kg.

4. The steel billet solidification forming process according to claim 1, wherein: the cooling time of slow cooling is more than or equal to 48 hours, and the temperature of casting blank entering slow cooling is more than or equal to 600 ℃.

5. The steel billet solidification forming process according to claim 1, wherein: the parameters of each electromagnetic stirring are 2-15HZ and 200-1000A.

6. The steel billet solidification forming process according to claim 1, wherein: the straightening pressure for straightening the drawing blank is 10-60 t.

7. The steel billet solidification forming process according to claim 1, wherein: the casting blank is P92 steel.