CN109881089B

CN109881089B - High-strength wear-resistant steel and preparation method thereof

Info

Publication number: CN109881089B
Application number: CN201910124582.7A
Authority: CN
Inventors: 陈颜堂; 李东晖; 孙超; 党军
Original assignee: Nanjing Iron and Steel Co Ltd
Current assignee: Nanjing Iron and Steel Co Ltd
Priority date: 2019-02-19
Filing date: 2019-02-19
Publication date: 2020-10-27
Anticipated expiration: 2039-02-19
Also published as: CN109881089A

Abstract

The invention discloses high-strength wear-resistant steel, which comprises the chemical compositions of, by weight, 0.41-0.59% of C, 0.31-0.58% of Si, 7.1-8.9% of Mn, less than or equal to 0.018% of P, less than or equal to 0.01% of S, 0.25-0.35% of Ti, 3.60-5.60% of Cr, 0.10-0.30% of Zr, and the balance of Fe and inevitable impurities; the microstructure of the steel consists of 10-20% austenite and tempered martensite. Meanwhile, the invention also discloses a preparation method of the wear-resistant steel, which adopts a process route comprising the following steps: converter smelting → ladle furnace refining → die casting → forging → rolling → cooling after rolling → heat treatment. The wear-resistant steel has high yield strength and excellent wear resistance. The use time of the relieving tooth manufactured by the wear-resistant steel can reach more than 220 days.

Description

High-strength wear-resistant steel and preparation method thereof

Technical Field

The invention designs alloy structural steel, and particularly relates to high-strength wear-resistant steel and a preparation method thereof.

Background

The wear-resistant steel is widely applied to building wear structural members such as mining machinery, ball mill lining plates, excavators and railway frog, and has huge annual demand. Wear conditions are generally divided into two types: one is impact wear under high impact loads, such as between a railroad frog and a high speed wheel; the other is that the abrasion of the medium-low load abrasive material, such as shovel teeth of an excavator, and the difference of the types of steel materials adopted by abrasion structural parts under different working conditions is large. The shovel teeth and the like of the traditional excavator are usually built by low-alloy wear-resistant steel plates and are manufactured by high-temperature quenching and low-temperature tempering, the microstructure is single tempered martensite, the hardness is high, but the toughness is low, the shovel teeth are easy to break in the using process, the shovel teeth are frequently replaced, and the service life is short. The high-carbon high-manganese steel is subjected to high-temperature solution treatment (water toughening treatment) to obtain a single austenite structure, has good wear resistance, but has low yield strength, and is easy to deform plastically to lose efficacy in the use process if being manufactured into a shovel tooth of a large mining excavator.

The Chinese invention patent application with the application number of 201711332869.6 discloses a low-alloy medium-manganese wear-resistant steel hot-rolled plate and a preparation method thereof, and the low-alloy medium-manganese wear-resistant steel hot-rolled plate comprises the following components: c: 0.6-0.8%, Si: 0.1-0.2%, Mn: 4.5 to 4.9 percent of the total weight of the composition, and P is less than or equal to0.02%, S is less than or equal to 0.02%, Cr: 3.0-3.5%, Cu: 0.4-1.0%, and the balance of Fe and impurities. The disadvantages of the patent technology are that the content of C in chemical components is high, and carbides (Fe and Mn) are easily formed in grain boundaries in the manufacturing process₃C. Cr series carbide causes crystal boundary brittleness and low yield; on the other hand, the alloy element Cu is added, but the alloy element for inhibiting Cu hot cracking is not added, so that the Cu hot cracking phenomenon is easily generated in the manufacturing process of the steel, the production difficulty is increased, and the manufacturing cost is increased.

Chinese patent application No. 201611226312.X discloses a medium-manganese wear-resistant ball with high hardness and high toughness, which comprises the following components in percentage by weight: c: 3.3-3.7%, Mn: 5.5-6.5%, S less than 0.04%, P less than 0.1%, Si: 3.6-4.6%, Cr: 14.83 to 16.83%, Mo: 0.012-0.018%, V: 0.05-0.09%, W: 0.01-0.02%, Ti: 0.02 to 0.06%, Bi: 0.01-0.03%, rare earth: 0.02-0.045%, Mg: 0.04-0.055%, and the balance of Fe and inevitable impurities. And also provides a preparation method of the medium-manganese wear-resistant ball with high hardness and high toughness. The patent technology provides a typical cast iron material, the alloy elements are complex, the expensive alloy elements such as V, Mo and Bi are provided, and the easily-oxidizable elements such as rare earth and Mg are added, so that the smelting process is not easy to master, the production difficulty is high, and the cost is high. The added Si has high content and serious brittleness tendency, and can not be used for manufacturing the shovel tooth structural part of the excavator.

The invention discloses a high-carbon medium-manganese wear-resistant steel and a manufacturing method of a hot rolled plate in Chinese patent application No. 201510711213. The wear-resistant steel comprises the following chemical components in percentage by weight: c: 1.0-1.2%, Si is less than or equal to 0.3%, Mn: 5.0-7.0%, P < 0.02%, S < 0.02%, Cr: 1.5-2.5%, Mo: 0.2-0.8%, V: 0.1-0.3%, Ti is less than or equal to 0.1%, Al: 0.03-0.08%, and the balance of Fe and inevitable impurities. The manufacturing steps of the wear-resistant steel hot rolled plate comprise steel making, continuous casting, heating by a heating furnace, hot rolling and heat treatment. The hot rolled plate has a water toughening temperature of 950-1050 ℃ and a water toughening termination temperature of below 200 ℃. The microstructure obtained by toughening water at 950-1050 ℃ in the patented technology is fully austenitic, the tensile strength is greater than 700MPa, but the yield strength is low, deformation is easy to occur in the using process, and the quenching tooth cannot be used for manufacturing the relieving tooth of an excavator, particularly the relieving tooth of a large mine excavator, and the yield strength is high and the wear resistance is good.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects of the prior art, the invention provides the high-strength wear-resistant steel which has higher yield strength and excellent wear resistance.

The invention also aims to provide a preparation method of the high-strength wear-resistant steel.

The technical scheme is as follows: the chemical composition of the high-strength wear-resistant steel comprises, by weight, 0.41-0.59% of C, 0.31-0.58% of Si, 7.1-8.9% of Mn, less than or equal to 0.018% of P, less than or equal to 0.01% of S, 0.25-0.35% of Ti, 3.60-5.60% of Cr, 0.10-0.30% of Zr, and the balance of Fe and inevitable impurities; the microstructure of the steel consists of 10-20% austenite and tempered martensite.

The principle of the main control alloy elements is explained as follows:

c (carbon): adding a certain content of alloy element C, after quenching and low-temperature tempering, dissolving a part of C in a ferrite matrix to form solid solution strengthening, and generating fine precipitated phase carbide in the low-temperature tempering process to form dispersion strengthening, so that the yield strength of the wear-resistant steel is more than or equal to 695 MPa. The addition of C has the other effect of expanding an austenite area, and a part of high-temperature austenite can be stably kept to room temperature, so that the impact energy of the wear-resistant steel at the temperature of minus 40 ℃ is more than or equal to 48J. If the content of the added C is less than 0.41 percent, the strengthening effect is insufficient, and the yield strength is difficult to reach the expectation; if the C content is more than 0.59%, the toughness is lowered. Therefore, the content of C is set to 0.41-0.59%.

Mn (manganese): mn in the steel can stabilize a high-temperature austenite structure and reduce the austenite transformation temperature. By adopting the manufacturing method of the patent application, 10-20% of austenite can be inhibited from being converted into polygonal ferrite, so that high-temperature austenite is stabilized to room temperature, and good impact toughness is obtained. If the Mn content is less than 7.1%, the capability of stabilizing high-temperature austenite is insufficient, the tempered martensite content is too high, and the toughness is low; if the Mn content is more than 8.9%, the room-temperature austenite structure is excessively generated and the strength is low, so that the Mn content is set to a range of 7.1 to 8.9%.

P (phosphorus): p is a harmful element, and the toughness of the steel is rapidly deteriorated when the content of P is high, so that the content of P is limited to be less than or equal to 0.018 percent, and if the content of P is controlled to be too low, the cost of the smelting process is high.

S (sulfur): s is a harmful element and reacts with Mn in steel to form a harmful inclusion MnS, which sharply reduces the low-temperature impact toughness of the steel, so that the lower the S content is, the better the S content is, but if the S content is controlled to be too low, the desulfurization cost is greatly increased, and the S content is preferably controlled to be less than or equal to 0.01%.

Si (silicon): the alloy element Si can form solid solution strengthening to improve the yield strength of the steel, but the Si content is too high to promote the C in the steel to graphitize and reduce the toughness of the steel, so the Si content in the steel is set to be in the range of 0.31-0.58%.

Ti (Ti) and Ti (CN) fine particles generated by the reaction of Ti and C, N in steel effectively prevent the movement of grain boundary and inhibit the growth of crystal grains, and can refine cast crystal grains and structures and improve the production manufacturability. Ti partially dissolved in the matrix has the function of stabilizing austenite, so that the room-temperature austenite content reaches the expectation. However, if the content of heat-generating Ti is too high, the formed Ti (CN) precipitates tend to grow and lose the effect of refining grains, so that the Ti content in the steel is set in the range of 0.25 to 0.35%.

Cr (chromium): adding proper amount of Cr as alloy element to wear-resistant steel to form Cr series carbide, such as Cr₇C₃，Cr₂₃C₆、Cr₃C and the like, and the hardness is improved and the wear resistance is enhanced by dispersing and distributing the C and the like in the matrix. If the Cr content is less than 3.6%, the precipitated phases formed are insufficient to provide the intended dispersion strengthening effect. If the Cr content is more than 5.6%, the formed precipitated phase is easily coarsened and the strengthening effect is lost, so that the Cr content is set in the range of 3.60 to 5.60%.

Zr (zirconium): adding proper amount of Zr alloy element can react with C in steel to produce nanometer level second phase ZrC and other carbide, and this can refine crystal grain and structure. In addition, the heat conductivity coefficient of Zr is nearly 3 times that of Mn, and another important purpose of adding Zr is to improve the fluidity of medium and high manganese steel in the casting process, improve the production process performance and improve the ingot casting quality. If the Zr content is lower than 0.10 percent, the fluidity of the molten steel is not improved; above 0.30%, the production cost is significantly increased, and the content of Zr is set in the range of 0.10 to 0.30% because Zr is a relatively expensive alloying element.

Wherein the yield strength of the steel is more than or equal to 695MPa, the Brinell hardness is more than or equal to 375HBW, and the impact energy at-40 ℃ is more than or equal to 48J.

In a preferred embodiment, the chemical composition contains, in mass percent, 0.59% of C, 0.51% of Si, 8.9% of Mn, 0.012% of P, 0.007% of S, 0.272% of Ti, 4.7% of Cr, 0.30% of Zr, and the balance Fe and inevitable impurities.

The preparation method of the high-strength wear-resistant steel adopts the following process routes: converter smelting → ladle furnace refining → die casting → forging → rolling → cooling after rolling → heat treatment.

Specifically, the preparation method comprises the following steps:

(1) loading molten iron, scrap steel, MnFe and TiFe alloy materials into a top-bottom combined blown converter for smelting; adding CaO and FeO to remove P; blowing oxygen for decarburization; adding SiFe for deoxidation;

(2) refining in a ladle furnace, electrifying and heating, and adding a desulfurizing agent to remove sulfur; adjusting the content of the alloy elements to a control range;

(3) die casting into steel ingots;

(4) heating the die-cast steel ingot to 1180-1240 ℃, forging the die-cast steel ingot into a slab size of a wide and thick plate production line capable of rolling into a material, wherein the finish forging temperature is more than or equal to 900 ℃;

(5) heating temperature of the plate blank: 1160-1220 ℃, and the heat preservation time is more than or equal to 4 hours;

(6) continuously rolling to the size of a finished steel plate, wherein the rolling temperature is more than or equal to 900 ℃;

(7) cooling after rolling: air cooling to room temperature after rolling;

(8) quenching: quenching temperature: and (2) at 950-1070 ℃, and keeping the temperature for a period of time: 60-120 min; and (3) cooling: immersing in water and quenching to room temperature;

(9) tempering: tempering temperature: 178-368 ℃, heat preservation time: 90-196 min; and (3) cooling: and air-cooling to room temperature.

Has the advantages that: the high-strength wear-resistant steel is refined by adopting a ladle furnace after being smelted by the converter through reasonable component design, the steel quality is purified, and the components are easy to control. The steel plate is continuously rolled to the size of a finished steel plate once, so that the production efficiency is high. After quenching and tempering heat treatment, the microstructure of the steel grade consists of 10-20% of austenite and tempered martensite, has good obdurability matching, the yield strength is more than or equal to 695MPa, and the impact energy is-40 ℃ KV₂Not less than 48J, and Brinell hardness not less than 375 HBW. The steel plate is adopted to build easily-worn structural members such as shovel teeth and crusher toothed plates of large-scale mining excavators, and the service life of the steel plate is prolonged by more than 50% compared with that of traditional wear-resistant steel.

Detailed Description

Hereinafter, the present invention will be described in further detail by smelting and rolling and heat-treating eight batches of steel sheets.

Specifically, five batches of steel plates were prepared according to the chemical element composition, mass percentage and production method requirements of the present invention, which are examples 1-5, respectively. Meanwhile, in order to verify the influence of the chemical components, the mass percentage content, the temperature in the rolling and heat treatment process, the time range and other parameters on the performance and the service life, three batches of steel plates are also prepared as comparative examples, namely comparative examples 1 to 3.

Wherein, the mass percentage contents of the chemical components of the comparative example 1 are out of the scope of the invention, and the technological parameters of the preparation process are in the scope of the invention; the chemical components of comparative example 2 were contained in the range of the present invention by mass, the process parameters of the preparation process were not contained in the range of the present invention, and the chemical components of comparative example 3 were not contained in the range of the present invention by mass and the process parameters of the preparation process were not contained in the range of the present invention. The chemical element composition weight percentages of five examples and three comparative examples are shown in table 1, with the balance being Fe and unavoidable impurities.

TABLE 1 comparison of chemical compositions (wt%) of inventive and comparative examples

The production process control parameters, steel plate properties, service life and the like are shown in Table 2.

TABLE 2 Table of the properties and applications of the steel sheets in the control of the production process of the examples and comparative examples

As can be seen from tables 1 and 2, the yield strength of the steel plate produced by the chemical components and mass percentages of the steel plate in the examples 1 to 5 and the rolling, heat treatment temperature, tempering time and the like controlled by the production process is higher than 695MPa, the impact energy at minus 40 ℃ is higher than 48J, and the Brinell hardness of the steel plate is higher than 375 HBW. While the steel composition ranges or/and production processes of comparative 1, comparative 2 and comparative 3 are not within the scope of the present invention, the yield strength of the produced comparative steel plate is lower than 518MPa, the impact energy at-40 ℃ is lower than 41J, and the Brinell hardness is lower than 342 HBW. Among them, the example using the least number of days was improved by 50% from the comparative example using the most number of days. The failure modes of the examples were all wear failures and replaced, while the comparative relieved tooth failure modes were fracture, yield deformation + wear, wear + fracture failures.

Furthermore, it can be seen that the impact energy of the steel plate prepared in example 5 at-40 ℃ reaches 220J, the Brinell hardness is 401HBW, the comprehensive mechanical property is excellent, and the service life of the manufactured relieving reaches 227 days, which is the best example.

Claims

1. The high-strength wear-resistant steel is characterized by comprising, by weight, 0.41-0.59% of C, 0.31-0.58% of Si, 7.1-8.9% of Mn, less than or equal to 0.018% of P, less than or equal to 0.01% of S, 0.25-0.35% of Ti, 3.60-5.60% of Cr, 0.10-0.30% of Zr, and the balance of Fe and inevitable impurities; the microstructure of the steel consists of 10-20% of austenite and tempered martensite;

the preparation method of the high-strength wear-resistant steel comprises the following steps:

(3) die casting into steel ingots;

(7) cooling after rolling: air cooling to room temperature after rolling;

2. The high-strength wear-resistant steel according to claim 1, wherein the steel has a yield strength of 695MPa or more, a Brinell hardness of 375HBW or more, and an impact energy of 48J or more at-40 ℃.

3. The high-strength wear-resistant steel according to claim 1, wherein the chemical composition contains, in mass%, 0.59% C, 0.51% Si, 8.9% Mn, 0.012% P, 0.007% S, 0.272% Ti, 4.7% Cr, 0.30% Zr, and the balance Fe and inevitable impurities.

4. A method for producing a high strength wear resistant steel according to any one of claims 1-3, characterized in that the process route comprises: converter smelting → ladle furnace refining → die casting → forging → rolling → cooling after rolling → heat treatment; the method comprises the following steps:

(3) die casting into steel ingots;

(7) cooling after rolling: air cooling to room temperature after rolling;