NICKEL-FREE LPG MARINE STEEL PLATE AND MANUFACTURING METHOD THEREFOR

Abstract

A nickel-free LPG marine steel plate and a manufacturing method therefor belong to the technical field of high-strength structural steels; the steel plate consists of the following chemical components by mass percentage: 0.18 to 0.24% of C, 0.10 to 0.19% of Si, 16.1 to 18.9% of Mn, less than or equal to 0.012% of P, 0.15 to 0.35% of Mo, 0.10 to 0.25% of RE, and the balance of Fe and inevitable impurities; the steel plate has a yield strength of ≥410 MPa and an impact absorption work of ≥66 J at 150° C., has good low-temperature mechanical properties, can replace 5Ni and 9Ni-based steel, and is used for constructing an LPG storage tank and a relevant structural member at low costs.

Claims

1. A nickel-free LPG marine steel plate, comprising the following chemical components in percentage by mass: C: 0.18-0.24%, Si: 0.10-0.19%, Mn: 16.1-18.9%, P: 0.012%, Mo: 0.15-0.35%, RE: 0.10-0.25%, and the balance Fe and inevitable impurities.

2. The nickel-free LPG marine steel plate according to claim 1, wherein a metallographic structure is a single-phase austenite structure.

3. The nickel-free LPG marine steel plate according to claim 1, wherein in the chemical components in percentage by mass, Mn is 17.1-18.9%.

4. The nickel-free LPG marine steel plate according to claim 1, wherein in the chemical components in percentage by mass, Mo is 0.25-0.35%.

5. A manufacturing method for the nickel-free LPG marine steel plate according to claim 1, comprising processes of electric furnace smelting, vacuum degassing (VD) furnace refining, die casting, rolling, cooling after rolling and tempering, wherein in the rolling process, a 160 mm*1000 mm*2200 mm die casting plate billet is immediately rolled after being uniformly heated and discharged from a furnace, an initial rolling temperature 1100° C., and a finishing temperature 980° C.; in the process of cooling after rolling, the steel plate is rapidly cooled to a room temperature by means of watering; and in the tempering process, the steel plate is tempered at 280-320° C., and heat preservation is conducted for 80-120 min.

6. The manufacturing method according to claim 5, wherein in the electric furnace smelting process, an alloy comprising CaO, scrap steel, MnFe, SiFe and MoFe is charged for electric melting, FeO is added to remove P, and a content of alloying elements is adjusted to a target value.

7. The manufacturing method according to claim 5, wherein in the VD furnace refining process, gas elements comprising O, N and H are removed in vacuum.

8. The manufacturing method according to claim 5, wherein in the die casting process, rare earth wires are fed during casting, and a content of a rare earth element reaches a target value.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present disclosure will be further described in detail below with reference to the embodiments.

[0028] According to the requirements for chemical element components, mass percentages and a production method of the present disclosure, five embodiments are set, namely embodiment 1, embodiment 2, embodiment 3, embodiment 4 and embodiment 5. In order to verify the influence of the chemical components and the mass percentage content as well as the cast billet heating temperature, the finishing temperature and the tempering temperature after finish rolling in the rolling process on performance parameters, three comparative examples, namely comparative example 1, comparative example 2 and comparative example 3, are prepared, and eight batches of steel plates are smelted and rolled.

[0029] The mass percentage content of the chemical components of comparative example 1 is not within the scope of the present disclosure, and technological parameters of a preparation process are within the scope of the present disclosure; the mass percentage content of the chemical components of comparative example 2 is within the scope of the present disclosure, and technological parameters of a preparation process are not within the scope of the present disclosure; and the mass percentage content of the chemical components and technological parameters of a preparation process of comparative example 3 are both not within the scope of the present disclosure. The mass percentages of the chemical element components of the five embodiments and the three comparative examples are shown in Table 1, with the balance being Fe and unavoidable impurities.

TABLE-US-00001 TABLE 1 Chemical component comparison (wt. %) of embodiments and comparative examples of present disclosure Embodiment of present disclosure Comparative example Element 1 2 3 4 5 1 2 3 C 0.21 0.18 0.22 0.24 0.19 0.67 0.23 0.14 Si 0.16 0.14 0.10 0.19 0.172 0.27 0.11 0.31 Mn 18.5 16.1 17.1 17.8 18.9 6.86 17.13 1.45 P 0.011 0.009 0.012 0.011 0.01 0.016 0.011 0.018 Mo 0.26 0.15 0.18 0.35 0.31 0.032 0.17 0.02 RE 0.12 0.21 0.10 0.25 0.19 0.0031 0.13 0.0022

[0030] Production process control parameters and steel plate quality conditions are shown in

TABLE-US-00002 TABLE 2 Table 2 Table of production process control vs. steel plate performance conditions of embodiments of present disclosure and comparative examples Cast billet Impact heating Finishing Tempering Yield energy Serial number of temperature temperature temperature strength at −150° C. steel (° C.) (° C.) (° C.) (MPa) (J) Embodiment 1 1167 1023 307 427 116 of present disclosure Embodiment 2 1200 991 316 410 128 of present disclosure Embodiment 3 1160 980 320 439 66 of present disclosure Embodiment 4 1176 989 297 431 98 of present disclosure Embodiment 5 1185 1012 280 442 188 of present disclosure Embodiment of present disclosure Comparative 1 1182 993 319 316 16 steel Comparative 2 1268 831 457 391 21 steel Comparative 3 1245 902 655 345 34 steel

[0031] As can be seen from Table 1 and Table 2, the steel plates produced according to the chemical components and the mass percentages as well as the rolling temperature controlled in the production process of embodiments 1-5 of the present disclosure have the yield strength of higher than 410 MPa, while the comparative steel plates produced according to the steel component ranges or/and the production processes which are not within the range of the present disclosure of comparative example 1, comparative example 2 and comparative example 3 have the yield strength of lower than 316 MPa.

[0032] The steel plate prepared in embodiment 5 has the yield strength of 442 MPa, impact energy at −150° C. of 188 J, and an excellent comprehensive mechanical property, such that embrittlement cracking may be effectively avoided for when the steel plate is used for manufacturing ultralow-temperature structural parts, safe operation is achieved, and embodiment 5 is the best embodiment.