WO2023087882A1 - Rare earth-containing nm600 wear-resistant steel plate and preparation method therefor - Google Patents

Abstract

The present invention relates to the technical field of steel production. Disclosed are a rare earth-containing NM600 wear-resistant steel plate and a preparation method therefor. The wear-resistant steel plate comprises the following chemical components and mass percentage: C: 0.21%-0.63%, Mn: 0.20%-1.00%, Si: 0.10%-0.30%, Cr: 0.15%-0.85%, Mo: 0.08%-0.75%, Ni: 0.70%-2.00%, Nb: 0.010%-0.060%, V: 0.010%-0.060%, Ti: 0.010%-0.040%, Alt: 0.020%-0.080%, B: 0.0008%-0.0030%, Ce: 0.0005%-0.0080%, P≤0.010%, S≤0.0020%, O≤0.0020%, N≤0.0040%, and the remainder is iron and unavoidable impurities. By adding a rare earth alloy into low-alloy high-strength wear-resistant steel, low-temperature impact toughness and plasticity are effectively improved without reducing the hardness and strength of the steel plate.

Description

A kind of NM600 wear-resistant steel plate containing rare earth and preparation method thereof technical field

The invention relates to the technical field of iron and steel production, in particular to a rare earth-containing NM600 wear-resistant steel plate and a preparation method thereof.

Background technique

Wear is one of the main forms of failure of mechanical parts. The use failure caused by wear increases the frequency of maintenance and replacement of workpieces, greatly reduces production efficiency, produces quite astonishing economic losses, and even causes equipment and personal accidents. With the rapid development of modern industry, the operating speed of mechanical equipment is getting higher and higher, the speed of friction workpieces is getting faster and faster, and the failure of mechanical parts caused by wear is becoming more and more prominent. In recent years, the research and development of low-alloy high-strength wear-resistant steel in my country has made great progress, and the grades and grades of low-alloy wear-resistant steel developed have been continuously improved. NM360, NM400, NM450, NM500 and other series of low alloy wear-resistant steel. Hardness is an important index to measure the wear resistance of metal materials, and the increase of hardness usually leads to the decrease of toughness and plasticity. How to prepare wear-resistant materials with higher hardness and strength while ensuring excellent plasticity and toughness has become a difficult point in the development of higher-level low-alloy wear-resistant steels.

Contents of the invention

The present invention aims at the above technical problems, overcomes the shortcomings of the prior art, and provides a rare earth-containing NM600 wear-resistant steel plate, whose chemical composition and mass percentage are as follows: C: 0.21%-0.63%, Mn: 0.20%-1.00%, Si : 0.10%-0.30%, Cr: 0.15%-0.85%, Mo: 0.08%-0.75%, Ni: 0.70%-2.00%, Nb: 0.010%-0.060%, V: 0.010%-0.060%, Ti: 0.010 %-0.040%, Alt: 0.020%-0.080%, B: 0.0008%-0.0030%, Ce: 0.0005%-0.0080%, P≤0.010%, S≤0.0020%, O≤0.0020%, N≤0.0040%, I The amount is iron and unavoidable impurities.

The technical scheme further defined in the present invention is:

The aforementioned rare earth-containing NM600 wear-resistant steel plate has the following chemical composition and mass percentage: C: 0.38%-0.40%, Mn: 0.40%-0.50%, Si: 0.20%-0.30%, Cr: 0.20% -0.30%, Mo: 0.10%-0.20%, Ni: 1.00%-1.20%, Nb: 0.010%-0.040%, V: 0.010%-0.040%, Ti: 0.010%-0.040%, Alt: 0.020%-0.050 %, B: 0.0008%-0.0030%, Ce: 0.0010%-0.0030%, P≤0.010%, S≤0.0020%, O≤0.0020%, N≤0.0040%, the balance is iron and unavoidable impurities.

The aforementioned rare earth-containing NM600 wear-resistant steel plate has the following chemical composition and mass percentage: C: 0.41%-0.43%, Mn: 0.50%-0.60%, Si: 0.30%-0.40%, Cr: 0.35% -0.45%, Mo: 0.20%-0.30%, Ni: 1.2%-1.4%, Nb: 0.010%-0.040%, V: 0.010%-0.040%, Ti: 0.010%-0.040%, Alt: 0.020%-0.080 %, B: 0.0008%-0.0030%, Ce: 0.0030%-0.0050%, P≤0.008%, S≤0.0015%, O≤0.0018%, N≤0.0035%, the balance is iron and unavoidable impurities.

Another object of the present invention is to provide a method for preparing a rare earth-containing NM600 wear-resistant steel plate, comprising the following steps:

(1) Hot metal pretreatment

Desulfurization of molten iron is pretreated by KR method or injection method, and slag is removed after pretreatment of molten iron to ensure that S in molten iron is ≤ 0.0020%;

(2) Converter smelting

Decarburization, desiliconization, and desulfurization of hot metal are carried out in the top-bottom combined blowing converter, and the tapping temperature is controlled at 1620-1660 °C; after tapping the converter, aluminum is added for deoxidation, and the total oxygen in the molten steel is ≤0.0500%; lime is added in the tapping process of 6.4± 0.3kg/t steel and pre-melted refining slag 2.3±0.3kg/t steel;

(3) LF refining

Lime and quartz sand should be properly supplemented according to the slag condition, and the alkalinity should be controlled at 4.5-6.5; aluminum particles, aluminum powder or aluminum wire should be used for deoxidation, the total oxygen in molten steel should be ≤0.0020%, and the dissolved oxygen should be ≤0.0005%;

(4) RH refining

The holding time of high vacuum degree is ≥25min; after the end of RH, after adding ferroboron or feeding boron wire, the static stirring time is ≥15min;

(5) Continuous casting

Strict argon sealing is implemented for continuous casting long nozzles and submerged nozzles, the casting speed is controlled at 0.70-0.80m/min, carbon-free covering agent is used for the tundish, and high-carbon steel mold slag is used for casting;

(6) Rolling

The continuous casting billet is put into the furnace with a temperature above 150°C, and the cold billet is heated by laying on the bottom and covered by the upper cover or preheated in the table furnace; the heating temperature is 1220±20°C, and the rolling is controlled by two stages. ≤920℃, target final rolling temperature ≥800℃, air cooling after rolling; two-stage cumulative reduction rate ≥40% and ≥50% respectively;

(7) heat treatment

The heating temperature for quenching is 840-950°C, and the time in the furnace is 23-55 minutes; the heating temperature for tempering is 210-280°C, and the time in the furnace is 65-155 minutes.

The above-mentioned preparation method of NM600 wear-resistant steel plate containing rare earth, step (4), vacuum degree ≤ 3.0mbar, use bottom blowing argon to blow off the slag layer before vacuum treatment, then add ferrocerium alloy, or vacuum treatment for 10-20min Add ferro-cerium alloy through the silo, or use bottom-blown argon to blow off the slag layer after vacuum treatment, and then add ferro-cerium alloy.

In the aforementioned method for preparing a rare earth-containing NM600 wear-resistant steel plate, the thickness of the steel plate is 12-30mm.

In the aforementioned method for preparing a rare earth-containing NM600 wear-resistant steel plate, the metallographic structure of the steel plate is acicular martensite.

The beneficial effects of the present invention are:

(1) In the present invention, rare earth alloys are added in the molten steel refining process, and rare earths are used to modify the quality of inclusions in the molten steel, and at the same time cooperate with scientific and reasonable rolling and heat treatment systems to realize the refinement of steel plate grains, so as to improve plasticity and impact toughness purposes;

(2) In the present invention, the basicity of LF refining slag is controlled at 4.5-6.5, so that the refining slag maintains good fluidity and adsorption capacity to inclusions, and minimizes the amount of inclusions in the steel;

(3) In the present invention, the RH high vacuum degree keeping time is more than or equal to 25min, so as to reduce the H content in molten steel, make the inclusions collide and grow up to float, reduce the quantity of inclusions, and improve the purity of molten steel;

(4) In the present invention, the continuous casting long nozzle and the submerged nozzle are strictly argon-sealed, so as to avoid secondary pollution of molten steel and reduce the generation of foreign inclusions;

(5) The rolling in the present invention adopts two-stage controlled rolling. After the first stage of rolling, the temperature is ≤920°C, and the target final rolling temperature is ≥800°C, so as to refine the original grain size of the steel plate and improve the impact toughness of the steel plate.

Detailed ways

Example 1

A method for preparing a rare earth-containing NM600 wear-resistant steel plate provided in this embodiment, the specific steps are as follows:

The KR method is used to pretreat the molten iron for desulfurization and slag removal. The mass fraction of S in the molten iron after pretreatment is 0.0016%. Decarburization, desiliconization, and desulfurization of molten iron are carried out in a top-bottom combined blowing converter, and the tapping temperature is 1646°C. Aluminum is added for deoxidation after the converter is tapped, and the mass fraction of total oxygen in the molten steel is 0.0470%. Lime 6.4±0.3kg/t steel and pre-melted refining slag 2.3±0.3kg/t steel are added in the tapping process. The alkalinity of the LF refining process is controlled at 5.4, and aluminum grain deoxidation is used. The mass fraction of total oxygen in the LF outbound molten steel is 0.0020%, and the mass fraction of dissolved oxygen is 0.0005%. Before the vacuum treatment in the RH refining process, use bottom blowing argon to blow off the slag layer, and then add ferrocerium alloy. The high vacuum degree (≤3.0mbar) is kept for 26 minutes. After the RH is finished, ferroboron is added, and the static stirring time is 18 minutes. The continuous casting long nozzle and submerged nozzle are strictly argon-sealed, the casting speed is controlled at 0.70-0.80m/min, the tundish adopts carbon-free covering agent, and the casting adopts high-carbon steel mold slag. The continuous casting billet is put into the furnace with temperature at 150°C, and the cold billet is heated with a lower bed and a upper cover or preheated in a desktop furnace. The heating temperature is 1220±20°C, and the rolling adopts two-stage controlled rolling. After the first stage of rolling, the temperature is raised to 860°C, and the target final rolling temperature is 800°C. After rolling, it is air-cooled. The cumulative reduction rates of the two stages are 60% and 70% respectively. Heat treatment: The quenching heating temperature is 840°C, and the furnace time is 23 minutes; the tempering heating temperature is 210°C, and the furnace time is 65 minutes.

The chemical composition of the steel plate is shown in Table 1, and the mechanical properties of the steel plate measured by the national standard test method are shown in Table 2.

Example 2

A method for preparing a rare earth-containing NM600 wear-resistant steel plate provided in this embodiment, the specific steps are as follows:

The injection method is used to pretreat the molten iron for desulfurization and slag removal, and the mass fraction of S in the molten iron after pretreatment is 0.0019%. Decarburization, desiliconization, and desulfurization of molten iron are carried out in a top-bottom combined blowing converter, and the tapping temperature is 1628°C. After the converter is tapped, aluminum is added for deoxidation, and the mass fraction of total oxygen in the molten steel is 0.0420%. Lime 6.4±0.3kg/t steel and pre-melted refining slag 2.3±0.3kg/t steel are added in the tapping process. The alkalinity of the LF refining process is controlled at 6.5, and aluminum powder is used for deoxidation. The mass fraction of total oxygen in the LF outbound molten steel is 0.0018%, and the mass fraction of dissolved oxygen is 0.0003%. During the RH refining process, the high vacuum degree (≤3.0mbar) is maintained for 28 minutes, and the vacuum treatment is 17 minutes to add ferrocerium alloy through the silo. After the end of RH, ferroboron is added, and the static stirring time is 17 minutes. The continuous casting long nozzle and submerged nozzle are strictly argon-sealed, the casting speed is controlled at 0.70-0.80m/min, the tundish adopts carbon-free covering agent, and the casting adopts high-carbon steel mold slag. The continuous casting billet is put into the furnace with temperature at 160°C, and the cold billet is heated by laying on the bottom and covering it or preheating in a desktop furnace. The heating temperature is 1220±20°C, and the rolling adopts two-stage controlled rolling. After the first stage of rolling, the temperature is raised to 880°C, and the target final rolling temperature is 810°C. After rolling, it is air-cooled. The cumulative reduction rates of the two stages are 60% and 70% respectively. Heat treatment: The quenching heating temperature is 890°C, and the furnace time is 47min; the tempering heating temperature is 240°C, and the furnace time is 98min.

The chemical composition of the steel plate is shown in Table 1, and the mechanical properties of the steel plate measured by the national standard test method are shown in Table 2.

Example 3

A method for preparing a rare earth-containing NM600 wear-resistant steel plate provided in this embodiment, the specific steps are as follows:

The KR method is used to pretreat the molten iron for desulfurization and slag removal. The mass fraction of S in the molten iron after pretreatment is 0.0017%. Decarburization, desiliconization, and desulfurization of molten iron are carried out in a top-bottom combined blowing converter, and the tapping temperature is 1660°C. After the converter is tapped, aluminum is added for deoxidation, and the mass fraction of total oxygen in the molten steel is 0.0480%. Lime 6.4±0.3kg/t steel and pre-melted refining slag 2.3±0.3kg/t steel are added in the tapping process. The alkalinity of the LF refining process is controlled at 4.5, and aluminum wire is used for deoxidation. The mass fraction of total oxygen in the LF outbound molten steel is 0.0017%, and the mass fraction of dissolved oxygen is 0.0003%. During the RH refining process, the high vacuum degree (≤3.0mbar) is maintained for 25 minutes. After the vacuum treatment is completed, the slag layer is blown away by bottom blowing argon, and then the ferrocerium alloy is added. After the RH is completed, ferroboron is added, and the static stirring time is 20 minutes. The continuous casting long nozzle and submerged nozzle are strictly argon-sealed, the casting speed is controlled at 0.70-0.80m/min, the tundish adopts carbon-free covering agent, and the casting adopts high-carbon steel mold slag. The continuous casting billet is put into the furnace with temperature at 150°C, and the cold billet is heated with a lower bed and a upper cover or preheated in a desktop furnace. The heating temperature is 1220±20°C, and the rolling adopts two-stage controlled rolling. After the first stage of rolling, the temperature is 920°C, and the target final rolling temperature is 830°C. After rolling, it is air-cooled. The cumulative reduction rates of the two stages are 40% and 50% respectively. Heat treatment The heating temperature for quenching is 950°C, and the time in the furnace is 55min; the heating temperature for tempering is 280°C, and the time in the furnace is 155min. The composition of the prepared steel plate is shown in Table 1, and the mechanical properties of the steel plate measured by the national standard test method are shown in Table 2.

The chemical composition of the steel plate is shown in Table 1, and the mechanical properties of the steel plate measured by the national standard test method are shown in Table 2.

Table 1 Embodiment 1-3 steel plate composition

Example	C(%)	Si(%)	Mn(%)	Cr(%)	Mo(%)	Ni(%)	Nb(%)	V(%)
1	0.21	0.23	0.20	0.15	0.47	2.00	0.010	0.010
2	0.63	0.30	1.00	0.85	0.75	0.70	0.060	0.021
3	0.41	0.10	0.55	0.58	0.08	1.76	0.037	0.060
Example	Ti(%)	Alt(%)	B(%)	P(%)	S(%)	T.O(%)	N(%)	Ce(%)
1	0.020	0.080	0.0030	0.006	0.0008	0.0005	0.0038	0.0005
2	0.010	0.056	0.0008	0.005	0.0012	0.0008	0.0035	0.0037
3	0.040	0.020	0.0013	0.005	0.0009	0.0008	0.0033	0.0080

Table 2 Example 1-3 steel plate mechanical properties

It can be seen from the above examples that the tensile strength of the rare earth-containing NM600 wear-resistant steel plate with a thickness of 12-30mm prepared by the present invention is ≥1800MPa, yield strength is ≥1550MPa, elongation is ≥13.0%, and surface hardness is ≥580HB, -20 ℃ impact ≥ 21J. Under the condition of the same thickness (12mm), with the increase of rare earth content in the steel plate, the elongation after fracture and the impact energy at -20°C are significantly improved, and the toughness and plasticity are enhanced, while the strength and hardness indicators do not decrease. When the thickness of the steel plate increases, the strength, hardness and ductility and plasticity indicators can also be maintained at a considerable level.

In addition to the above-mentioned embodiments, the present invention can also have other implementations. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims (7)

1. A NM600 wear-resistant steel plate containing rare earth, characterized in that its chemical composition and mass percentage are as follows: C: 0.21%-0.63%, Mn: 0.20%-1.00%, Si: 0.10%-0.30%, Cr: 0.15% -0.85%, Mo: 0.08%-0.75%, Ni: 0.70%-2.00%, Nb: 0.010%-0.060%, V: 0.010%-0.060%, Ti: 0.010%-0.040%, Alt: 0.020%-0.080 %, B: 0.0008%-0.0030%, Ce: 0.0005%-0.0080%, P≤0.010%, S≤0.0020%, O≤0.0020%, N≤0.0040%, the balance is iron and unavoidable impurities.
2. A rare earth-containing NM600 wear-resistant steel plate according to claim 1, characterized in that its chemical composition and mass percentage are as follows: C: 0.38%-0.40%, Mn: 0.40%-0.50%, Si: 0.20%- 0.30%, Cr: 0.20%-0.30%, Mo: 0.10%-0.20%, Ni: 1.00%-1.20%, Nb: 0.010%-0.040%, V: 0.010%-0.040%, Ti: 0.010%-0.040% , Alt: 0.020%-0.050%, B: 0.0008%-0.0030%, Ce: 0.0010%-0.0030%, P≤0.010%, S≤0.0020%, O≤0.0020%, N≤0.0040%, the balance is iron and unavoidable impurities.
3. A rare earth-containing NM600 wear-resistant steel plate according to claim 1, characterized in that its chemical composition and mass percentage are as follows: C: 0.41%-0.43%, Mn: 0.50%-0.60%, Si: 0.30%- 0.40%, Cr: 0.35%-0.45%, Mo: 0.20%-0.30%, Ni: 1.2%-1.4%, Nb: 0.010%-0.040%, V: 0.010%-0.040%, Ti: 0.010%-0.040% , Alt: 0.020%-0.080%, B: 0.0008%-0.0030%, Ce: 0.0030%-0.0050%, P≤0.008%, S≤0.0015%, O≤0.0018%, N≤0.0035%, the balance is iron and unavoidable impurities.
4. A method for preparing a rare earth-containing NM600 wear-resistant steel plate according to claim 1, characterized in that it is applied to any one of claims 1-3, comprising the following steps:

   (1) Hot metal pretreatment

   Desulfurization of molten iron is pretreated by KR method or injection method, and slag is removed after pretreatment of molten iron to ensure that S in molten iron is ≤ 0.0020%;

   (2) Converter smelting

   Decarburization, desiliconization, and desulfurization of molten iron are carried out using a top-bottom combined blowing converter, and the tapping temperature is controlled at 1620-1660 °C; after tapping the converter, aluminum is added for deoxidation, and the total oxygen in the molten steel is ≤0.0500%; lime is added in the tapping process of 6.4± 0.3kg/t steel and pre-melted refining slag 2.3±0.3kg/t steel;

   (3) LF refining

   Lime and quartz sand should be properly supplemented according to the slag condition, and the alkalinity should be controlled at 4.5-6.5; aluminum particles, aluminum powder or aluminum wire should be used for deoxidation, the total oxygen in molten steel should be ≤0.0020%, and the dissolved oxygen should be ≤0.0005%;

   (4) RH refining

   High vacuum maintenance time ≥ 25min; After RH is over, after adding ferroboron or feeding boron wire, the static stirring time is ≥ 15min;

   (5) Continuous casting

   Strict argon sealing is implemented for continuous casting long nozzles and submerged nozzles, the casting speed is controlled at 0.70-0.80m/min, carbon-free covering agent is used for the tundish, and high-carbon steel mold slag is used for casting;

   (6) Rolling

   The continuous casting billet is put into the furnace with a temperature above 150°C, and the cold billet is heated by laying on the bottom and covered by the upper cover or preheated in the table furnace; the heating temperature is 1220±20°C, and the rolling is controlled by two stages. ≤920℃, target final rolling temperature ≥800℃, air cooling after rolling; two-stage cumulative reduction rate ≥40% and ≥50% respectively;

   (7) heat treatment

   The heating temperature for quenching is 840-950°C, and the time in the furnace is 23-55 minutes; the heating temperature for tempering is 210-280°C, and the time in the furnace is 65-155 minutes.
5. The preparation method of a rare earth-containing NM600 wear-resistant steel plate according to claim 4, characterized in that: in the step (4), the vacuum degree is ≤ 3.0mbar, and the slag layer is blown off by bottom blowing argon before vacuum treatment and then added Ferro-cerium alloy, or vacuum treatment for 10-20min to add ferro-cerium alloy through the silo, or use bottom blowing argon gas to blow off the slag layer after vacuum treatment and then add ferro-cerium alloy.
6. A method for preparing rare earth-containing NM600 wear-resistant steel plate according to claim 4, characterized in that: the thickness of the steel plate is 12-30mm.
7. A method for preparing rare earth-containing NM600 wear-resistant steel plate according to claim 4, characterized in that: the metallographic structure of the steel plate is acicular martensite.