Dual-hardness clad steel plate and production method thereof

Abstract

A dual-hardness clad steel plate. One surface of the steel plate is a high-hardness layer, the other surface of the steel plate is a low-hardness layer, and a combination of atoms is achieved between the high-hardness layer and the low-hardness layer by rolling bonding, wherein Mn13 steel is adopted for the low-hardness layer, and the Brinell hardness of the high-hardness layer is greater than 600. Further disclosed is a production method of the dual-hardness clad steel plate, comprising: 1) respectively preparing a high-hardness layer slab and a low-hardness layer slab; 2) assembling: preprocessing combined faces of the slabs, carrying out peripheral welded sealing on joint faces of the slabs, and carrying out vacuumizing treatment on a composite slab after welded sealing; 3) heating; 4) carrying out composite rolling; 5) cooling; and 6) carrying out thermal treatment, wherein the heating temperature is 1050-1100 C., the heating time is 2-3 min/mmslab thickness, and water cooling is performed on the heated slab, and the water temperature is lower than 40 C. The steel plate has different hardness characteristics and good low-temperature toughness.

Claims

1. A dual-hardness clad steel plate, wherein one surface of the dual-hardness clad steel plate is a high hardness layer, and another surface thereof is a low hardness layer, wherein atomic bonding is realized between the high hardness layer and the low hardness layer by rolling, wherein the low hardness layer is Mn13 steel with a Brinell hardness lower than 250, and the high hardness layer has a Brinell hardness of greater than 600, wherein the high-hardness layer comprises the following chemical elements in mass percentage: C: 0.35-0.45%, Si: 0.80-1.60%, Mn: 0.3-1.0%, Al: 0.02-0.06%, Ni: 0.3-1.2%, Cr: 0.30-1.00%, Mo: 0.20-0.80%, Cu: 0.20-0.60%, Ti: 0.01-0.05%, B: 0.001-0.003%, and a balance of iron and unavoidable impurities, and Wherein the low hardness layer comprises the following chemical elements in mass percentage: C: 1.00-1.35%, Si: 0.30-0.90%, Mn: 11.0-19.0%, Al: 0.02-0.06%, and a balance of iron and unavoidable impurities.

2. The dual-hardness clad steel plate according to claim 1, wherein the high-hardness layer has a microstructure of martensite and a small amount of residual austenite.

3. The dual-hardness clad steel plate according to claim 2, wherein a proportion of the residual austenitic phase is less than 1%.

4. The dual-hardness clad steel plate according to claim 1, wherein the low-hardness layer further comprises Mo: 0.90-1.80%.

5. The dual-hardness clad steel plate according to claim 1, wherein the dual-hardness clad steel plate has an impact strength of no less than 50 J at 40 C.

6. The dual-hardness clad steel plate according to claim 1, wherein a thickness ratio of the high-hardness layer to the low-hardness layer is (0.43-3):1.

7. A method of manufacturing the dual-hardness clad steel plate according to claim 1, wherein the method comprises the following steps: a. Preparing a high-hardness layer slab and a low-hardness layer slab respectively; b. Assembling slabs: pre-treating slab faces to be bonded, sealing a periphery around bonded faces of the slabs by welding, and subjecting a weld-sealed composite slab to vacuumizing treatment; c. Heating d. Clad rolling; e. Cooling; f. Heat treatment: a heating temperature for heat treatment is 1050-1100 C.; a heating time is 2-3 min/mmplate thickness; a heated clad plate is water cooled, wherein a water temperature is lower than 40 C., wherein the plate thickness has a unit of mm.

8. The method of manufacturing the dual-hardness clad steel plate according to claim 7, wherein in the step c, a heating temperature is 1130-1250 C., and a heating time is 120-180 min.

9. The method of manufacturing the dual-hardness clad steel plate according to claim 8, wherein in the step d, a finishing rolling temperature is controlled in the range of 850-1000 C.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a photograph showing a metallographic structure of the dual-hardness clad steel plate according to Example A4.

(2) FIG. 2 is an image showing a microstructure of the high-hardness layer in the dual-hardness clad steel plate according to Example A4.

DETAILED DESCRIPTION

(3) The dual-hardness clad steel plate and the manufacture method thereof according to the disclosure will be further explained and illustrated with reference to the accompanying drawings and the specific examples. Nonetheless, the explanation and illustration are not intended to unduly limit the technical solution of the disclosure.

Examples A1-A4

(4) The dual-hardness clad steel plates in the Examples were manufactured with the following steps:

(5) (1) Preparing high-hardness layer slabs and low-hardness layer slabs respectively, with the various chemical elements in the high-hardness layer slabs and low-hardness layer slabs being controlled as shown in Table 1;

(6) (2) Assembling slabs:

(7) (2a) the high-hardness layer slabs and low-hardness layer slabs were formed by bloom rolling in light of practical needs, wherein thicknesses of the slabs were determined by a thickness of a final dual-hardness clad steel plate and a thickness ratio of the high-hardness layer slab to the low-hardness layer slab;

(8) (2b) slab faces to be bonded were pre-treated, wherein the bonding faces of the high-hardness layer and low-hardness layer slabs were processed respectively using a miller or planer to remove scales, slag inclusions and similar defects from the slab faces, and then a single face of each slab was cleaned, followed by chamfering four sides of the single face of the slab;

(9) (2c) two cleaned slabs were placed together with cleaned face to cleaned face, and a periphery around the bonded faces of the slabs was sealed by welding;

(10) (2d) a vacuum channel was left at a side of the slab after welding for subjecting the weld-sealed composite slab to vacuumizing treatment;

(11) (3) Heating: a heating temperature was 1130-1250 C., and a heating time was 120-180 min;

(12) (4) Clad rolling, with the finishing rolling temperature being controlled in the range of 850-1,000 C.;

(13) (5) Cooling;

(14) (6) Heat treatment: a heating temperature for the heat treatment was 1050-1100 C.; a heating time was 2-3 min/mmplate thickness; a heated clad plate was water cooled on a roll table or in a water pool, wherein the water temperature was lower than 40 C.

(15) Table 1 lists the mass percentages of the various chemical elements in the high-hardness layers and low-hardness layers of the dual-hardness clad steel plates in Examples A1-A6.

(16) TABLE-US-00001 TABLE 1 (wt %, the balance is Fe and other unavoidable impurities) Thickness ratio of high- hardness Clad plate layer to low- thickness hardness No. Slab C Si Mn Al Ni Cr Mo Cu Ti B (mm) layer A1 I* 0.36 1.55 0.41 0.034 0.40 0.39 0.30 0.40 0.023 0.0015 6.5 2.25/1 II* 1.3 0.80 18 0.035 / / / / / / A2 I 0.38 0.95 0.64 0.047 0.55 0.94 0.55 0.26 0.034 0.0022 8 3/1 II 1.2 0.65 15 0.045 / / 1.2 / / / A3 I 0.40 1.36 0.80 0.038 0.46 0.46 0.28 0.55 0.034 0.0026 15 0.67/1 II 1.1 0.55 13 0.055 / / / / / / A4 I 0.39 1.45 0.95 0.042 0.33 0.76 0.34 0.48 0.015 0.0016 20 0.43/1 II 1.0 0.35 11 0.055 / / / / / / A5 I 0.42 1.45 0.95 0.042 0.33 0.76 0.34 0.48 0.015 0.0016 12 1/1 II 1.0 0.35 11 0.055 / / 0.9 / / / A6 I 0.41 1.45 0.95 0.042 0.33 0.76 0.34 0.48 0.015 0.0016 16 0.6/1 II 1.1 0.55 16 0.038 / / 1.6 / / / *Note: I represents high-hardness layer; II represents low-hardness layer.

(17) Table 2 lists the specific process parameters in the manufacture method for the dual-hardness clad steel plates in Examples A1-A6.

(18) TABLE-US-00002 TABLE 2 Step (4) Step (3) Finishing Step (6) Heating rolling Heating Water cooling temperature Heating time temperature temperature Heating time temperature No. ( C.) (min) ( C.) ( C.) (min) ( C.) A1 1250 120 850 1050 19.5 20 A2 1250 180 880 1060 24 22 A3 1200 120 960 1080 38 25 A4 1150 150 980 1090 40 30 A5 1140 160 950 1075 30 24 A6 1230 140 1000 1060 45 28

(19) The dual-hardness clad steel plates in the above Examples were sampled for various mechanical properties tests. The relevant mechanical properties obtained in the tests are listed in Table 3. Meanwhile, the samples of the dual-hardness clad steel plates were subjected to shooting tests. The results of the tests are listed in Table 4.

(20) Table 3 lists the parameters of the relevant mechanical properties of the dual-hardness clad steel plates in Examples A1-A4.

(21) TABLE-US-00003 TABLE 3 Brinell hardness Brinell hardness Impact strength of high-hardness of low-hardness of clad steel plate No. layer (HB10/3000) layer (HB10/3000) KV2 (40 C.)/J A1 613 217 60 A2 618 230 54 A3 620 210 90 A4 630 210 210 A5 620 223 80 A6 615 235 190 Note: The impact samples for test plates in A1 and A2 had a size of 5 10 55 mm; and the impact samples for test plates in A3-A6 had a size of 10 10 55 mm. The position of an impact sample in a test plate in a direction of the cross-section along thickness was as follows: a sample was taken from the low-hardness layer side of a steel plate; a layer of 1 mm was removed from the steel plate surface; and then a longitudinal impact sample was machined. In the table, HB10/3000 represents a Brinell hardness value measured under a 3000 kg load using an indenter of 10 mm in diameter.

(22) As can be seen from Table 3, each of the high-hardness layers of the dual-hardness clad steel plates in Examples A1-A6 has a Brinell hardness>613 HB; and each of the low-hardness layers has a Brinell hardness<250 HB. This indicates that the two surfaces of a clad steel plate in each example have different hardnesses, and this clad steel plate has two different hardness features at the same time. In addition, each of the dual-hardness clad steel plates in Examples A1-A6 has an impact strength KV2 (40 C.)>50 J. This indicates that the clad steel plates in the above examples have good low-temperature toughness.

(23) Table 4 lists the shooting test results of the dual-hardness clad steel plates in Examples A1-A4.

(24) TABLE-US-00004 TABLE 4 Shooting distance Shooting No. Bullet type (m) velocity (m/s) Result A1 M16 automatic rifle, 30 981/985/983 Not shot 5.56 45 through A2 M16 automatic rifle, 30 986/986/985 Not shot 5.56 45 through A3 M16 automatic rifle, 10 984/985/983 Not shot 5.56 45 through A4 M16 automation rifle, 10 986/984/987 Not shot 5.56 45 through A5 M16 automatic rifle, 10 976/981/982 Not shot 5.56 45 through A6 M16 automatic rifle, 10 971/975/973 Not shot 5.56 45 through

(25) As can be seen from Table 4, when the same type of bullets were used to shoot the steel plates in Examples A1-A6 from different shooting distances at substantially the same shooting velocity, none of the dual-hardness clad steel plates in Examples A1-A6 were shot through. This indicates that the steel plates in Examples A1-A6 have good bullet-proof performance, and its bullet resistance meets the FB5 standard in EN.1063.

(26) FIG. 1 shows a metallographic structure of the dual-hardness clad steel plate according to Example A4. In addition, FIG. 2 shows a microstructure of the high-hardness layer in the dual-hardness clad steel plate according to Example A4.

(27) As can be seen from FIG. 1, this dual-hardness clad steel plate has a high-hardness layer and a low-hardness layer, wherein the upper layer is the high-hardness layer whose microstructure is martensite and a small amount of residual austenite; wherein the lower layer is the low-hardness layer whose microstructure is purely austenite. As can be seen from FIG. 2, nearly all of the microstructure of the high-hardness layer is martensite, with a proportion of the residual austenitic phase being lower than 1%.

(28) It is to be noted that there are listed above only specific examples of the invention. Obviously, the invention is not limited to the above examples. Instead, there exist many similar variations. All variations derived or envisioned directly from the disclosure of the invention by those skilled in the art should be all included in the protection scope of the invention.