CN116179926A - A kind of production method of rare earth wear-resistant GN-14A hot-rolled round steel for mining - Google Patents

Abstract

The invention discloses a production method of mining rare earth wear-resistant GN-14A hot rolled round steel, which comprises the following steelmaking process: the converter adopts double slag operation, and the final alkalinity is controlled according to 2.5; the converter end point control target C is more than or equal to 0.08 percent, and P is less than or equal to 0.020 percent; the VD deep vacuum time is more than or equal to 15min, and the soft blowing time is more than or equal to 20min; the superheat degree is less than or equal to 25 ℃, the casting machine pull speed is less than or equal to 0.55m/min and less than or equal to 0.60m/min; the slow cooling time of the casting blank is more than or equal to 24 hours; the steel rolling process comprises the following steps: the initial rolling temperature is less than or equal to 1020 ℃ and less than or equal to 1050 ℃; the finishing temperature is not less than 780 ℃ and not more than 850 ℃; the temperature of entering the slow cooling pit is more than or equal to 450 ℃ and less than or equal to 550 ℃; the temperature of the slow cooling pit is more than or equal to 50 ℃ and less than or equal to 150 ℃. The structure of the hot rolled round steel prepared by the method is ferrite and pearlite, the class A of inclusions is less than or equal to 1.5, the class B is less than or equal to 1.5, the class C is less than or equal to 1.0, the class D is less than or equal to 1.5, and the austenite grain size is more than or equal to 5.

Description

A kind of production method of rare earth wear-resistant GN-14A hot-rolled round steel for mining

technical field

The invention relates to the field of material metallurgy, in particular to a production method of rare earth wear-resistant GN-14A hot-rolled round steel for mining.

Background technique

With the large-scale and increasing use of semi-autogenous mills at home and abroad, the demand for large-diameter wear-resistant steel balls has gradually increased. In the past, the forming process of large-diameter wear-resistant steel balls was mainly medium-frequency induction heating, air hammer forging Or press extrusion molding, but there are some problems with this heating and molding process. Medium-frequency induction heating: Due to the shape characteristics of the round steel itself, the rapid heating process causes uneven temperature inside and outside the round steel, resulting in uneven austenitization of the round steel, resulting in poor product quality uniformity and unstable quality; air hammer forging: The ambient temperature of the process is high, the labor intensity is high, and the production efficiency is low. The output of a single machine is about 1 ton per hour, which cannot guarantee the uniformity and stability of product quality; and the use of press extrusion does not meet the compression ratio of steel ball forming. As a result, the compactness of the steel ball is poor, and the grains cannot be refined, thus affecting the quality of the steel ball product.

Improving the hardness of grinding balls is the most effective way to reduce wear. The normal wear of the grinding ball is the wear process of the large ball becoming small. Only by maintaining a round shape during the entire wear process and ensuring that the inside and outside of the ball have sufficient hardness and wear resistance can the normal grinding of the ball be guaranteed. effect. If the hardness of the grinding ball is uneven, it will lead to loss of round during the wear process. If the hardness difference between the inside and the outside of the grinding ball is large, and the hardened layer is shallow, the wear of the outer hardened layer will increase sharply; therefore, a good grinding ball The ball should have a small difference in hardness between the inside and outside. The industry standard for grinding balls used in metallurgical mines stipulates that the hardness difference between the surface and core of the grinding ball should not exceed 3HRC. In addition, the refinement of the grinding ball structure and grain is not only conducive to the improvement of strength and hardness, but also conducive to the improvement of toughness, which can reduce the risk of steel ball cracking.

The increase of alloying elements is very beneficial to reduce the hardness difference between the inside and outside of the steel ball and improve the wear resistance of the steel ball, but this will firstly increase the cost of the alloy raw material, and secondly increase the difficulty of production and the complexity of the production process, thus The manufacturing cost will also increase; therefore, it is of great significance to develop a high-quality and low-cost steel for high-grinding balls.

Contents of the invention

The purpose of the present invention is to provide a production method of rare earth wear-resistant GN-14A hot-rolled round steel for mining. Class ≤1.0 grade, D class ≤1.5 grade, austenite grain size ≥5 grade.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

The invention discloses a production method of rare earth wear-resistant GN-14A hot-rolled round steel for mining. The steelmaking process is as follows: converter-external refining-VD vacuum treatment-continuous casting-slow cooling; the rolling process is: billet casting Heating—high pressure water dephosphorization—Ф850mm blanking machine—Ф700mm×3+Ф550mm×4 continuous rolling mill rolling—sawing (sampling)—slow cooling—nondestructive testing (ultrasonic testing + eddy current/infrared/magnetic flux leakage testing)—inspection - Grinding - bundling - warehousing - delivery; it is characterized in that the technical parameters controlled in the steelmaking process are:

The converter adopts double slag operation, and the terminal alkalinity is controlled according to 2.5;

Converter end point control target C≥0.08%, P≤0.020%;

VD deep vacuum time ≥ 15min, soft blowing time ≥ 20min;

Superheat ≤ 25 ℃, 0.55m/min ≤ caster casting speed ≤ 0.60m/min;

Slab slow cooling time ≥ 24 hours;

The technical parameters controlled in the rolling process are:

1020℃≤rolling temperature≤1050℃;

780℃≤finishing temperature≤850℃;

450°C ≤ entering slow cooling pit temperature ≤ 550°C;

50°C ≤ temperature out of the slow cooling pit ≤ 150°C.

Further, its chemical composition percentage requirements are: C: 0.66-0.68%, Mn: 0.95-1.00%, Si: 0.79-0.89%, Cr: 0.70-0.78%, P: ≤0.025%, S: ≤0.025%, RE: 0.002-0.003%, the rest is iron and unavoidable trace chemical elements.

Further, the as-rolled microstructure is ferrite + pearlite microstructure.

Further, the level of inclusions is class A≤1.5, class B≤1.5, class C≤1.0, class D≤1.5, and the austenite grain size≥5.

The reasons for limiting the main chemical composition are as follows:

C: C is the most effective element to improve the strength of steel. The increase of C content increases the tensile strength and yield strength of steel, but the elongation and impact toughness decrease, and the corrosion resistance will also decrease, and the welding heat affected zone of steel There will also be hardening phenomenon, leading to the generation of welding cold cracks. In order to ensure good comprehensive properties of the round steel, the C element content of the steel of the present invention is designed to be 0.66-0.68%.

Mn: Mn is an important strengthening and toughening element, and the cost is low. With the increase of manganese content, the strength of steel is obviously improved, and the processing performance of steel is improved, while the ductile-brittle transition temperature hardly changes. However, if the manganese content is too high, it will inhibit the transformation of ferrite and affect the yield strength of steel, which is not conducive to the control of yield ratio. The Mn element content of the steel of the invention is designed to be 0.95-1.00%.

Si: Si can improve the intensity of steel, by increasing Si element, can improve the intensity of steel to a certain extent, but along with the further increase of the mass percentage of Si, easily cause martensitic structure in steel, therefore, the present invention In the production method of the rare earth wear-resistant GN-14A hot-rolled round steel for mining, the mass percentage of Si is controlled at 0.79-0.89%.

Cr: Cr can improve the strength, hardness and atmospheric corrosion resistance of steel, and the effect is more significant when other alloying elements are added. Chromium can slow down the decomposition rate of austenite, significantly improve the hardenability of steel, and has a secondary hardening effect, but it also increases the tendency of temper brittleness of steel. However, when the chromium content is too high, it will reduce the toughness of the base material and the heat-affected zone. The Cr element content of the steel of the invention is designed to be 0.70-0.78%.

RE: RE has the function of purification and obvious deterioration in steel. The cleanliness of steel has been continuously improved, and the microalloying effect of rare earth elements has become increasingly prominent. The microalloying of rare earth elements includes the solid solution strengthening of trace rare earth elements, the interaction of rare earth elements with other solute elements and compounds, the existence state (atoms, inclusions or compounds), size, shape and distribution of rare earth elements, especially in the crystal The segregation of the boundary and the influence of rare earth on the steel surface and matrix structure. Therefore, the mass percentage of RE in the production method of rare earth wear-resistant GN-14A hot-rolled round steel for mines described in the present invention is limited to 0.002-0.003%.

The innovation of the invention is to reasonably control the content of C and Cr elements and add RE elements, control the size of inclusions and the cleanliness of steel through the steelmaking process, and control the microstructure transformation and grain size in the hot-rolled state through the steel rolling process to obtain hardness and Wear-resistant hot-rolled round steel with matching toughness.

Compared with prior art, beneficial technical effect of the present invention:

1) The as-rolled structure is ferrite + pearlite structure, which has high strength and toughness and is easy to follow-up processing of high wear-resistant steel balls;

2) The size of inclusions is controlled through the steelmaking process to improve the wear resistance of steel balls.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a low-magnification photo of hot-rolled round steel hot acid.

Detailed ways

The present invention will be further described through specific examples below, and the examples are only for the purpose of explanation, and the protection scope of the present invention is not limited to the examples.

The present invention is further described below:

Table 1 is the chemical composition and weight percentage content list of each embodiment of the present invention;

Tables 2 and 3 are a list of steelmaking and steel rolling process control parameters in each embodiment of the present invention;

Table 4 shows the size of inclusions in various examples of the present invention.

Chemical composition and weight percent content (%) of the embodiment of table 1

Example C Si mn P S Cr RE 1 0.67 0.82 0.98 0.018 0.010 0.73 0.0022 2 0.67 0.82 0.97 0.019 0.009 0.72 0.0025 3 0.68 0.85 0.97 0.018 0.008 0.71 0.0028

The main parameters of the steelmaking process of the embodiment of table 2

The rolling process parameter of table 3 embodiment

The inclusion size of each embodiment of table 4

Example Class A Class B Class C Class D 1 1.0 1.0 0.5 1.0 2 1.5 1.0 0.5 1.0 3 1.5 1.0 0.5 1.0

As can be seen from Table 1, Table 2, Table 3, and Table 4, the mine-use rare earth wear-resistant GN-14A hot-rolled round steel prepared by the present invention meets the technical requirements.

The above-mentioned embodiments are only to describe the preferred mode of the present invention, and are not intended to limit the scope of the present invention. Variations and improvements should fall within the scope of protection defined by the claims of the present invention.

Claims (4)

1. A production method of rare earth wear-resistant GN-14A hot-rolled round steel for mining, its steelmaking process is: converter-outside refining-VD vacuum treatment-continuous casting-slow cooling; steel rolling process is: billet casting Heating—high pressure water dephosphorization—Ф850mm blanking machine—Ф700mm×3+Ф550mm×4 continuous rolling mill rolling—sawing—slow cooling—nondestructive testing—inspection—grinding—bundling—storage—delivery; its characteristics That is, the technical parameters controlled in the steelmaking process are: The converter adopts double slag operation, and the terminal alkalinity is controlled according to 2.5; Converter end point control target C≥0.08%, P≤0.020%; VD deep vacuum time ≥ 15min, soft blowing time ≥ 20min; Superheat ≤ 25 ℃, 0.55m/min ≤ caster casting speed ≤ 0.60m/min; Slab slow cooling time ≥ 24 hours; The technical parameters controlled in the rolling process are: 1020℃≤rolling temperature≤1050℃; 780℃≤finishing temperature≤850℃; 450°C ≤ entering slow cooling pit temperature ≤ 550°C; 50°C ≤ temperature out of the slow cooling pit ≤ 150°C. 2. The production method of rare earth wear-resistant GN-14A hot-rolled round steel for mining according to claim 1, characterized in that, its chemical composition percentage requirements are: C: 0.66-0.68%, Mn: 0.95-1.00%, Si: 0.79-0.89%, Cr: 0.70-0.78%, P: ≤0.025%, S: ≤0.025%, RE: 0.002-0.003%, and the rest are iron and unavoidable trace chemical elements. 3. the production method of rare earth wear-resistant GN-14A hot-rolled round steel for mining according to claim 1, characterized in that, the rolled microstructure is ferrite+pearlite microstructure. 4. The production method of rare-earth wear-resistant GN-14A hot-rolled round steel for mining according to claim 3, characterized in that the inclusions are grade A ≤ 1.5, B ≤ 1.5, C ≤ 1.0, Class D ≤ grade 1.5, austenite grain size ≥ grade 5.

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