A hot rolling method for producing a low-cost low-temperature service pipeline steel L290M

Abstract

The application discloses a hot rolling method for producing low-cost low-temperature pipeline steel L290M, the continuous casting withdrawal speed of the pipeline steel L290M is 1.0-1.2 m / min, and a continuous casting thin slab with a thickness of 40-45 mm is obtained; the process conditions of soaking are as follows: the continuous casting slab is put into a soaking furnace at 1170-1210 DEG C, the cold charging soaking time is 25-50 min, and the hot charging time is 20-45 min; the starting temperature of rolling is 1160-1200 DEG C, and the final rolling temperature is 850+ / -15 DEG C; and the final thickness of the hot-rolled plate is 7.1 mm, the size of granular bainite structure is uniform, and the distribution is good. On the basis of the continuous casting and rolling process, the pipeline steel L290M alloy composition is creatively adjusted in microcosm, the pipeline steel L290M with low cost and low-temperature service can be stably produced, and the quality and competitiveness of the product are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgy, and particularly relates to a hot rolling method for producing low-cost low-temperature service pipeline steel L290M. BACKGROUND

[0002] With the aggravation of global energy consumption, the exploitation of oil and gas energy has extended to the polar region, permafrost, deep sea and desert environment, and therefore, the oil and gas long-distance pipeline engineering puts forward higher requirements for pipeline steel pipes, such as low temperature, large strain, thick wall and high strength. According to research, the Arctic region may contain 30% of the remaining natural gas and 13% of the remaining oil reserves on earth, which is extremely attractive for future energy development.

[0003] At present, drop weight tear test (DWTT) is a key index for testing the low-temperature dynamic tear resistance of pipeline steel, and meeting the index is an important technical difficulty for manufacturing low-temperature service pipeline steel pipes. When the thickness of the pipeline steel increases, the difficulty of meeting the low-temperature DWTT performance will significantly increase.

[0004] Through retrieval, the document with the Chinese patent application number CN 110616383 B discloses a pipeline steel with excellent toughness for-45 DEG C extremely low temperature environment and a manufacturing method thereof. The method is suitable for C: 0.030-0.060%, Si: 0.10-0.30%, Mn: 1.30-1.60%, P≤0.0100%, S≤0.0015%, Ni: 0.40-0.55%, Cr: 0.05-0.20%, Nb: 0.050-0.075%, Ti: 0.008-0.020%, Ca: 0.0010-0.0040%, Al: 0.010-0.050%, B≤0.0005%, N: 0.0010-0.0060%, O≤0.0050%, and the rest is Fe and inevitable impurities. The yield strength of the pipeline steel is greater than or equal to 450 MPa, the tensile strength is greater than or equal to 535 MPa, the elongation is greater than or equal to 18%, the Charpy impact energy at-45 DEG C is greater than or equal to 250 J, and the DWTT fracture shear area rate SA% at-45 DEG C is greater than or equal to 85%. The document has the disadvantage that although the comprehensive performance is excellent and the low-temperature drop weight performance is good, the relative manufacturing cost is increased, which is not conducive to long-term development.

[0005] Through retrieval, the document with the Chinese patent application number CN 112375969 A discloses a production method of-30 DEG C low-temperature toughness pipeline steel. The method is suitable for C 0.06-0.08%; Si 0.10-0.20%; Mn 1.15-1.30%; Alt 0.020-0.050; Ca 0.0010-0.0030%; Nb 0.015-0.025%; Ti 0.005-0.015%; and the balance is Fe and no

[0006] The other residual elements to be avoided are Fe and other trace impurity elements, the yield strength, tensile strength, elongation and yield strength ratio have moderate excess amount and stable control ability, the impact energy at-30 DEG C is stable and has moderate excess amount, which can meet the special needs of the product. The deficiency of the document is that the impact energy at-30 DEG C is basically maintained at about 120J, there is no drop hammer performance description, the content of Nb element is relatively higher than that of the present application, and the market price of titanium element is relatively low, so the relative cost is higher than that of the present application.

[0007] According to the search, the document of Chinese patent application No. CN 108467993 B, "a low-temperature pipeline with ultra-wide high toughness hot-rolled thick plate and its production method", the method is suitable for C: 0.030%~0.055%, Si: 0.16%~0.30%, Mn: 1.45%~1.70%, Nb: 0.04%~0.07%, Ti: 0.012%~0.025%, Cr: 0.20%~0.40%, Mo≤0.14%, Ni≤0.20%, Cu≤0.15%, Al≤0.030%, P≤0.010%, S≤0.0015%, O: 0.0005%~0.0020%, N: 0.001%~0.004%, Ca: 0.0010%~0.0045%, Ca / S≥1.8, (Mo+N i+Cr+Cu): 0.30%~0.60%, the rest is Fe and unavoidable impurities. The deficiency of the document is that the transverse yield strength is 485~540MPa, the transverse tensile strength is 610~680MPa, the transverse elongation A50 is greater than or equal to 43%, the-20 DEG C transverse DWTT shear area is greater than or equal to 85%, the overall performance is relatively excellent, but the low-temperature drop hammer temperature only reaches-20 DEG C, while the present application has the overall performance meeting the standard, and the excess amount is larger, and the low-temperature drop hammer temperature is-35 DEG C. SUMMARY

[0008] The purpose of the present application is to provide a hot rolling method for producing low-cost low-temperature service pipeline steel L290M, which aims to meet the impact performance at-30 DEG C and the ultra-low temperature drop hammer performance at-35 DEG C, and improve the comprehensive performance and service performance of the finished strip steel.

[0009] To solve the above technical problems, the present application adopts the following technical scheme:

[0010] The present application is a hot rolling method for producing low-cost low-temperature service pipeline steel L290M, comprising the following steps:

[0011] 1) select pipeline steel L290M, after smelting, pouring into slab, heating to 1190-1220 DEG C, cold charging in furnace time is 165-270 min, hot charging in furnace time is 160-270 min, soaking temperature is 1170-1210 DEG C, cold charging soaking time is 25-50 min, hot charging is 20-45 min, then under the condition of 940 DEG C ± 10 DEG C, rough rolling is carried out;

[0012] 2) the temperature range of finish rolling is 835-865 DEG C, and the cumulative reduction of finish rolling is 80-85 %;Ensure that the finish rolling temperature is 850 DEG C ± 15 DEG C;

[0013] 3) after finish rolling, the slab is cooled to coiling temperature for coiling, and the coiling temperature is 600 DEG C ± 15 DEG C.

[0014] Further, the continuous casting speed is 1.0-1.2 m / min, and the thickness of the continuous casting slab is 230 mm.

[0015] Further, after heating to 1190-1220 DEG C in step 1), the cold charging soaking time is 30-40 min, the hot charging is 30-35 min, and the first pass descaling treatment is carried out.

[0016] Further, the method of laminar flow cooling is used for cooling to the coiling temperature.

[0017] Further, the thickness of the hot-rolled casting slab is 230 mm, the thickness is 40-45 mm after R1 rough rolling and R2 rough rolling, and the thickness is 7.1 mm after finish rolling F1-F7.

[0018] Further, the composition of the pipeline steel L290M is as follows: C: 0.06-0.08 %, Si: 0.10-0.20 %, Mn: 1.10-1.25 %, Nb: 0.005-0.015 %, Ti 0.010-0.020 %, the balance is Fe and other unavoidable impurities, wherein P≤0.013 %, S≤0.005 %, O≤0.005 %.

[0019] Compared with the prior art, the beneficial technical effects of the present application are:

[0020] On the basis of continuous casting and rolling process, the present application creatively adjusts the microstructure of pipeline steel L290M alloy composition, utilizes Nb and Ti elements to inhibit austenite grain growth and promote nucleation during austenite transformation to refine the grain, control the thickness of the core structure and improve the uniformity of the structure. According to the distribution of the structure in different positions of the steel, the consistency and stability of the low-temperature pipeline steel granular bainite structure and performance are evaluated, the low-temperature service pipeline steel L290M can be stably produced, and the quality and competitiveness of the product can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] The application will be further described in connection with the accompanying drawings.

[0022] Figure 1 Microstructure metallographic chart at 1 / 2 of slab 1;

[0023] Figure 2 Microstructure metallographic chart at 1 / 4 of slab 1. DETAILED DESCRIPTION

[0024] The application will be further described in connection with the accompanying drawings.

[0025] The following examples are used to describe the application in more detail, which are only the description of the best mode of the application, and do not have any limitation on the scope of the application. Figure 1 Figure 2 The hot-rolled casting slab thickness of example 1 is 230mm, after R1 rough rolling and R2 rough rolling, the thickness is 40-45mm, and after F1-F7 finishing rolling, the thickness is 7.1mm, and the microstructure metallographic chart at 1 / 2 of finished product thickness is as shown in

[0026] Example 1

[0027] The composition of L290M used in the embodiment of the application is as follows in percentage by weight: C: 0.06-0.08%, Si: 0.10-0.20%, Mn: 1.10-1.25%, Nb: 0.005-0.015%, Ti 0.010-0.020%, and the balance of Fe and other inevitable impurities, wherein P≤0.013%, S≤0.005%, O≤0.005%.

[0028] The heating temperature in the embodiment of the application is 1190-1220℃, the cold charging time in the furnace is 165-270min, the hot charging time in the furnace is 160-270min, the soaking temperature is 1170-1210℃, the cold charging soaking time is 25-50min, and the hot charging is 20-45min.

[0029] The opening rolling temperature in the embodiment of the application is 1160-1200℃, and the cumulative reduction of rough rolling is 80-85%.

[0030] The cumulative reduction of finishing rolling in the embodiment of the application is 80-85%, and the finishing rolling final rolling temperature is ensured at 850±15℃.

[0031] The coiling temperature in the embodiment of the application is 600±15℃.

[0032] ​The intermediate blank thickness is 40-45 mm, and the finished product thickness is 7.1 mm in the embodiment of the application.

[0033] The laminar flow cooling method is used for cooling to the coiling temperature in the embodiment of the application.

[0034] The performance result fully meets the standard requirement, and the-35 ℃ drop hammer performance is stable in the embodiment of the application.

[0035] Table 1 L290M performance distribution

[0036]

[0037] The above-described embodiments are only used to describe the preferred modes of the application, and do not limit the scope of the application. Without departing from the design spirit of the application, various modifications and improvements of the technical solutions of the application made by those skilled in the art shall fall within the protection scope determined by the claims of the application.

Claims

1. A hot rolling method for producing a low-cost low-temperature service pipeline steel L290M, characterized in that: The method comprises the following steps: 1) selecting pipeline steel L290M, smelting and casting into a slab, heating to 1190-1220℃, cold charging in the furnace for 165-270min, hot charging in the furnace for 160-270min, soaking temperature 1170-1210℃, cold charging soaking time 25-50min, hot charging soaking time 20-45min, then rough rolling at 940±10℃; 2) the temperature range of finish rolling is 835-865℃, the cumulative reduction of finish rolling is 80-85%, and the finish rolling final rolling temperature is ensured to be 850±15℃; 3) the slab after finish rolling is cooled to the coiling temperature for coiling, and the coiling temperature is 600±15℃; The pipeline steel L290M comprises the following components in percentage by weight: C: 0.06-0.08%, Si: 0.10-0.20%, Mn: 1.10-1.25%, Nb: 0.005-0.015%, Ti: 0.010-0.020%, and the balance of Fe and other inevitable impurities, wherein P≤0.013%, S≤0.005%, and O≤0.005%.

2. The method of hot rolling of low-cost low-temperature service pipeline steel L290M according to claim 1, characterized in that: The continuous casting withdrawal speed is 1.0-1.2m / min, and the continuous casting slab with a thickness of 230mm is obtained.

3. The method of hot rolling of low-cost low-temperature service pipeline steel L290M according to claim 1, characterized in that: After heating to 1190-1220℃ in step 1), the cold charging soaking time is 30-40min, the hot charging time is 30-35min, and the first pass descaling treatment is performed.

4. The method of hot rolling of low-cost low-temperature service pipeline steel L290M according to claim 1, characterized in that: The method of laminar flow cooling is adopted for cooling to the coiling temperature.

5. The method of hot rolling of low-cost low-temperature service pipeline steel L290M according to claim 1, characterized in that: The hot-rolled slab has a thickness of 230mm, the thickness is 40-45mm after R1 rough rolling and R2 rough rolling, and the thickness is 7.1mm after finish rolling F1-F7.

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