DE112011103972T5 - Abrasion-resistant steel, process for producing an abrasion-resistant steel and articles made therefrom - Google Patents

Abstract

Abrasion-resistant steel, consisting in% by weight essentially of: 0.20-0.30% carbon, 0.40-1.25% manganese, maximum 0.05% phosphorus, maximum 0.01% sulfur, 0, 20-0.60% silicon, 0.50-1.70% chromium, 0.20-2.00% nickel, 0.07-0.60% molybdenum, 0.022-0.10% titanium, 0.001-0, 10% boron, 0.027-0.10% aluminum, the rest iron and incidental impurities. The steel may be melted and cast into a steel bar or slab, hot rolled to a desired plate thickness; austenitized at 1650-1700 ° F; water quenched and tempered at 350-450 ° F. The resulting steel plate may have a surface hardness of at least 440 HBW, a centerline hardness of at least 90% of surface hardness, and a transverse toughness at -60 ° F of at least 20 ft-lbs and at room temperature of at least 40 ft-lbs exhibit.

Description

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to an abrasion-resistant steel, and more particularly to an abrasion-resistant steel having a good hardenability, good weldability and high toughness, and a process for producing the same.

Description of the Related Art

Steels used to make tools for the extraction, movement and processing of abrasive materials, such as truck bed liners, bulldozers, chutes and other material handling equipment for the mining industry (coal, hard rock, gold, silver and others), wood and Paper industry, biomass industry, quarries and other similar industries must have a high abrasion and wear resistance and high toughness to avoid breakage. In general, abrasion resistance and wear resistance increase as hardness and hardenability increase, while toughness often decreases with increasing hardness and hardenability. Therefore, it is desirable for steels for these applications to have a combination of high hardness and hardenability and good toughness.

Such steels generally contain significant amounts of alloying elements such as Cr, Ni, Si and Al to achieve the high hardness and hardenability in combination with good toughness, making them costly and difficult to weld.

SUMMARY OF THE INVENTION

The present invention is directed to an abrasion-resistant steel, a method for producing an abrasion-resistant steel plate and an article made therefrom. The steel of the present invention consists essentially in weight%: 0.20-0.30% carbon, 0.40-1.25% manganese, maximum 0.05% phosphorus, maximum 0.01% sulfur, 0, 20-0.60% silicon, 0.50-1.70% chromium, 0.20-2.00% nickel, 0.07-0.60% molybdenum, 0.022-0.10% titanium, 0.001-0, 10% boron, 0.027-0.10% aluminum, the rest iron and incidental impurities. The inventive steel plate may have a hardened martensite microstructure, a surface hardness of at least 440 HBW, a mid-caliper hardness that is at least 90% of the surface hardness, and a transverse to -60 ° F tenacity of at least 20 ft-lbs and at room temperature of at least 40 ft-lbs.

The inventive method for producing the abrasion resistant steel plate of the invention comprises melting and casting a steel ingot or slab of the composition described in detail above, hot rolling the billet or slab to a plate of desired thickness, austenitizing the plate at 1650-1700 ° F, water quenching the plate and tempering the plate at 350-450 ° F.

BRIEF DESCRIPTION OF THE DRAWING (S)

1 Figure 3 shows the Jominy hardenability curves for laboratory melted batches of abrasion resistant steel and a prior art steel;

2A shows the Charpy impact work for longitudinal samples from laboratory-made abrasion-resistant steel plates; and

2 B shows Charpy impact work for transverse samples from laboratory-made abrasion-resistant steel plates.

DESCRIPTION OF THE PREFERRED EMBODIMENT (DE)

The abrasion resistant steel of the present invention consists essentially in weight%: 0.20-0.30% carbon, 0.40-1.25% manganese, maximum 0.05% phosphorus, maximum 0.01% sulfur, 0 , 20-0.60% silicon, 0.50-1.70% chromium, 0.20-2.00% nickel, 0.07-0.60% molybdenum, 0.022-0.10% titanium, 0.001-0 10% Boron, 0.027-0.10% aluminum, the rest iron and incidental impurities. It may consist more narrowly in weight% essentially of: 0.22-0.26% carbon, 0.70-0.90% manganese, maximum 0.025% phosphorus, maximum 0.003% sulfur, 0.20-0.40 % Silicon, 0.80-1.00% chromium, 0.40-0.60% nickel, 0.07-0.15% molybdenum, 0.022-0.04% titanium, 0.001-0.003% boron, 0.027-0 , 06% aluminum, the rest iron and accidental impurities. And nominally the composition in weight% may consist essentially of: 0.24% carbon, 0.80% manganese, maximum 0.010% phosphorus, maximum 0.003% sulfur, 0.25% silicon, 0.90% chromium, 0, 50% nickel, 0.10% molybdenum, 0.03% titanium, 0.0015% boron, 0.035% aluminum, the balance iron and incidental impurities.

The ranges for each alloying element have been chosen to provide the necessary hardness and hardenability while maintaining good weldability. The lower limit for each alloying element is necessary to achieve the desired hardness and the upper limit is necessary to ensure good weldability. In addition, Cr + Mn + Mo can be minimally equal to 1.4%, and / or Ni + Si + Cr can be minimally equal to 1.4%, and / or Cr + Si can be at least equal to 1% to ensure that necessary hardness and hardenability are achieved in order to achieve good wear resistance.

The steel can be melted and poured into ingots or slabs. During melting and casting, the steel may be cold rolled, desulphurized, vacuum degassed and treated for sulfide form control according to conventional methods known in the art. The desulfurization and / or sulfide form control can be used to reduce the amount of large sulfide inclusions that can contribute to reducing toughness by acting as crack nucleation sites.

The steel can then be hot rolled to a plate of 1 inch or less in thickness. Cross rolls can be used to improve the toughness in the transverse direction. The steel plate may be held for a minimum of 24 hours prior to the heat treatment to vent any hydrogen from the melting and / or hot rolling processes from the steel plate.

The steel plate may be austenitized at 1650-1700 ° F for a minimum of 30 minutes per inch of thickness, quenched with water and then tempered at 350-450 ° F for a minimum of 1 hour per inch thickness to form a microstructure of hardened martensite. Austenitizing for times greater than 1 hour per inch thick can result in grain growth and / or loss of notched impact strength, and annealing times exceeding 2 hours per inch thick can result in deleterious surface oxidation.

The resulting steel plate may have a surface hardness of at least 440 HBW, a center thickness hardness that is at least 90% of the surface hardness, a longitudinal yield strength of 1200 MPa or more, a longitudinal tensile strength of 1450 MPa or more, and a transverse toughness at -60 ° F of at least 20 ft-lbs and at room temperature of at least 40 ft-lbs. The steel may also have a surface hardness of 440-514 HBW.

Three steel batches (A, B, C) were melted in a 45 kg (100 lb) vacuum induction furnace. Each batch was poured from above into iron molds to produce one billet per batch measuring approximately 125 by 125 by 360 mm (5 x 5 x 14 in). The three steel batches had compositions shown in Table 1, with Lot C representing the inventive steel. Table 1

A 1-1 / 2-inch (37 mm) thick disc was cut from the bottom of each billet with a saw to provide material for as-cast Jominy curability tests. The disks were normalized at 1650 ° F (900 ° C) and a ASTM A255 standard Jominy sample was worked out of each disc. The Jominy samples were austenitized at 1650 ° F (900 ° C) and finally quenched. The Jominy hardenability curves for the three laboratory batches are in 1 shown. As compared with the abrasion-resistant steel of the prior art, the inventive steel has a higher initial hardness and lower hardenability as intended. It can be seen that the three laboratory batches have different degrees of hardenability. This is because lots A and B contain only 0.0006 and 0.0008% B, respectively, compared to lot C, which has 0.0015% B.

The remainder of the ingots were conditioned, then reheated at 2250 ° F (1230 ° C) in an electric oven with a nitrogen blanket atmosphere. The ingots from batches A and B were rolled into 3/8 inch (9.6 mm) thick plates, and the billet from batch C was rolled into a 3/4 inch (19 mm) thick plate.

The panels were then heat treated to simulate milling. They were austenitized at a temperature of 1650 ° F (900 ° C) for 30 minutes / inch thickness, followed by water quenching by agitation in cold water. The panels were then annealed at 400 ° F (205 ° C) for 30 minutes / inch thickness and air cooled.

Measurements of Brinell hardness (HBW) were made on both surfaces of the three plates. Round 0.350 inch (9 mm) tensile specimens were made from plate C in both the longitudinal and transverse directions. Flat tensile specimens were prepared from panels A and B and tested in the longitudinal direction. All experiments were done twice.

Charpy V notched specimens were prepared in both the longitudinal and transverse directions. For plates A and B, the thickness of the Charpy samples was 7.5 mm, while 10.0 mm samples were machined out of plate C in full size. The Charpy transition curves were measured by testing samples in triplicate at -60, -40, 0, 40, 72, and 212 ° F (-51, -40, -18, 4, 22, and 100 ° C).

The hardness of the three plates is shown in Table 2. The hardness values on opposite surfaces of each plate were the same. Plates A and B did not achieve the target minimum hardness of 440 HBW. However, the C plate of the inventive composition achieved an average hardness of 460 HBW which is well above the minimum 440 HBW set point. Table 2 Plate thickness (mm) Plate thickness (in.) HBW values Average HBW Plate A 9.6 3.8 440, 440, 442 441 Plate B 9.6 3.8 428, 435, 438 434 Plate C 19 3.4 456, 460, 460, 460, 461, 462 460

The tensile properties of the three panels are shown in Table 3. The plates A and B had substantially the same tensile properties. The longitudinal yield strength of plate C is the same as that of the thinner plates of about 1210 MPa (176 ksi). However, in accordance with the higher hardness of the plate C, its tensile strength is higher by about 100 MPa (15 ksi). The yield strength of the plate C is higher in the transverse direction than in the longitudinal direction, while the tensile strength in both directions is approximately the same. Although the plates A and B have a higher elongation than the plate C, which is expected due to their lower hardness, the reduction in the area value of the plate C is higher than in the plates A and B, which provides an adequate toughness to pull for the inventive steel displays. Table 3 direction Stretch limit tensile strenght Elongation% RA% MPa ksi MPa ksi Plate A L 1223 177.6 1496 217.2 15.7 43.0 Plate B L 1214 176.2 1488 216.0 16.3 41.3 Plate C L 1210 175.7 1584 229.9 8.7 45.0 Plate C T 1330 193.1 1600 232.2 9.3 54.3

The Charpy impact test results are shown in Table 4 and in the 2A and 2 B shown. To compare the values of the thinner plates A and B with the values for the plate C, the absorbed energy values of the "fullness equivalent" were calculated, as by ASTM A370 recommended by dividing the measured energies of the 7.5 mm thick samples by 0.75. It will be in 2 both the raw data and the "full-scale equivalent" values are shown. Consistent with the high hardness of the steels, the Charpy samples showed low percent shear at all test temperatures. The full-size equivalent data for the three plates have substantially the same values in the longitudinal and transverse directions, although the transversal absorbed energies were, as expected, slightly lower than the longitudinal ones.

Although the invention has been described in detail for purposes of illustration, based upon what is presently considered to be the most practical and preferred embodiments, it is to be understood that such details are intended for the sole purpose and that the invention is not limited to the disclosed embodiments On the contrary, it is intended to cover modifications and equivalent arrangements which are within the spirit and scope of the appended claims. Table 4

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• ASTM A255 standard Jominy sample [0016]
• ASTM A370 [0023]

Claims (22)

Abrasion-resistant steel, consisting in% by weight essentially of: 0.20-0.30% carbon, 0.40-1.25% manganese, maximum 0.05% phosphorus, maximum 0.01% sulfur, 0, 20-0.60% silicon, 0.50-1.70% chromium, 0.20-2.00% nickel, 0.07-0.60% molybdenum, 0.022-0.10% titanium, 0.001-0, 10% boron, 0.027-0.10% aluminum, the rest iron and incidental impurities. Abrasion-resistant steel according to claim 1, wherein the surface hardness is at least 440 HBW and the hardness in the middle of the thickness is at least 90% of the surface hardness. Abrasion-resistant steel according to claim 1, wherein the microstructure consists of hardened martensite. An abrasion-resistant steel according to claim 1, wherein the transverse toughness at -60 ° F is at least 20 ft-lbs and at room temperature is at least 40 ft-lbs. Abrasion-resistant steel according to claim 1, wherein the surface hardness is at least 440 HBW. Abrasion-resistant steel according to claim 5, wherein the surface hardness is between 440-514 HBW. Abrasion-resistant steel according to claim 1, consisting in weight% essentially of: 0.22-0.26% carbon, 0.70-0.90% manganese, maximum 0.025% phosphorus, maximum 0.003% sulfur, 0.20 -0.40% silicon, 0.80-1.00% chromium, 0.40-0.60% nickel, 0.07-0.15% molybdenum, 0.022-0.04%, 0.001-0.003% boron, 0.027-0.06% aluminum, the rest iron and incidental impurities. Abrasion-resistant steel according to claim 1, consisting in weight% substantially of: 0.24% carbon, 0.80% manganese, maximum 0.010% phosphorus, maximum 0.003% sulfur, 0.25% silicon, 0.90% chromium , 0.50% nickel, 0.10% molybdenum, 0.03% titanium, 0.0015% boron, 0.035% aluminum, the balance iron and incidental impurities. An abrasion resistant steel according to claim 1, wherein the steel has been austenitized at 1650-1700 ° F, quenched with water and tempered at 350-450 ° F. An abrasion-resistant steel according to claim 1, wherein Cr + Mn + Mo is at least 1.4%. An abrasion-resistant steel according to claim 1, wherein Ni + Si + Cr is at least 1.4%. The abrasion resistant steel of claim 1, wherein Cr + Si is at least 1%. Method for producing an abrasion-resistant steel plate, comprising the following steps: a) Melting and casting of a steel ingot or slab consisting in% by weight essentially of: 0.20-0.30% carbon, 0.40-1.25% manganese, maximum 0.05% phosphorus, maximum 0.01% sulfur, 0.20-0.60% silicon, 0.50-1.70% chromium, 0.20-2.00% nickel, 0.07-0.60% molybdenum, 0.022-0, 10% titanium, 0.001-0.10% boron, 0.027-0.10% aluminum, balance iron and incidental impurities; b) hot rolling the billet or slab to the desired thickness; c) austenitizing the plate at 1650-1700 ° F; d) water quenching of the plate; and e) Tempering the plate at 350-450 ° F. The process of claim 13, wherein during the melting and casting step, the steel is cold rolled, desulfurized, vacuum degassed, treated for sulfide form control, or a combination thereof. The method of claim 13, wherein transverse rolling is used during the hot rolling step. The method of claim 13, wherein the microstructure is hardened martensite. The method of claim 13, wherein the transverse toughness at -60 ° F is at least 20 ft-lbs and at room temperature is at least 40 ft-lbs. The method of claim 13, wherein the surface hardness is at least 440 HBW and the hardness in the middle of the thickness is at least 90% of the surface hardness. The method of claim 13, wherein the steel in weight% consists essentially of: 0.22-0.26% carbon, 0.70-0.90% manganese, 0.025% phosphorus maximum, 0.003% sulfur maximum, 0, 20-0.40% silicon, 0.80-1.00% chromium, 0.40-0.60% nickel, 0.07-0.15% molybdenum, 0.022-0.04% titanium, 0.001-0.003% Boron, 0.027-0.06% aluminum, the remainder iron and incidental impurities. The method of claim 13, wherein the steel in weight% consists essentially of: 0.24% carbon, 0.80% manganese, at most 0.010% phosphorus, at most 0.003% sulfur, 0.25% silicon, 0.90% Chromium, 0.50% nickel, 0.10% molybdenum, 0.03% titanium, 0.0015% boron, 0.035% aluminum, the balance iron and incidental impurities. Abrasion resistant article made of the abrasion resistant steel of claim 1. An abrasion resistant article according to claim 21 wherein the microstructure is hardened martensite and the surface hardness is at least 440 HBW.

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