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Hot rolling process capable of improving high-grade thick pipeline steel fracture toughness

A fracture toughness and thick gauge technology, which is applied to the hot rolling process of high-grade steel above X70, thick gauge pipe steel above 15mm, and the hot rolling process of high-grade thick gauge pipeline steel, which can solve the problem of poor stability and poor DWTT performance. ideals etc.

Inactive Publication Date: 2011-09-07
武钢集团有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The technical problem to be solved by the present invention is: aiming at the problems of unsatisfactory DWTT performance and poor stability in the batch production process of high-grade thick-gauge pipeline steel, the present invention provides a hot-rolled process to effectively control DWTT properties, improve fracture toughness, and solve the problem of controlling DWTT properties of X70 and X80 steels above 15mm

Method used

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  • Hot rolling process capable of improving high-grade thick pipeline steel fracture toughness
  • Hot rolling process capable of improving high-grade thick pipeline steel fracture toughness
  • Hot rolling process capable of improving high-grade thick pipeline steel fracture toughness

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0023] The carbon content in the steel slab is 0.05%, the niobium content is 0.06%, the nitrogen content is 0.0040% and other alloy elements, and the produced product requires X70 hot-rolled steel strip with a thickness of 15.9mm.

[0024] The hot rolling process sequentially includes the slab heating section process, hot rolling section process, plate coiling section process and cooling section process. The specific process parameters of each section process are:

[0025] (1) Slab reheating section process: slab heating temperature = T 固溶 +30~80℃, where T 固溶 is the complete solid solution temperature of niobium carbonitride in steel, so the slab reheating temperature is 1180°C;

[0026] (2) The relationship between the time in the furnace and the thickness of the slab is: the total time in the furnace = 1 / 2×t+30~50min, where t is the thickness of the slab in mm; the temperature difference between the upper and lower surfaces of the slab after reheating is ≤ 30°C;

[0027] ...

Embodiment 2

[0032] The difference from Example 1 is that the carbon content in the steel slab is 0.03%, the niobium content is 0.09%, the nitrogen content is 0.0045% and other alloy elements, and the produced product requires a X80 hot-rolled steel strip with a thickness of 18.4mm. The specific process parameters of each process are as follows:

[0033] (1) The slab reheating temperature is 1200°C;

[0034] (2) The rough rolling single pass reduction rate is 21%;

[0035] (3) The final rolling temperature is 830°C;

[0036] (4) The cumulative reduction rate of finishing rolling is 70%;

[0037] (3) The coiling temperature is 450°C;

[0038] (4) The cooling rate is 17°C / s.

[0039] The mechanical properties of the hot-rolled steel strip produced by the method described in Example 2 are shown in Steel 2 in Table 1.

Embodiment 3

[0041] The difference from Example 1 is that the carbon content in the steel slab is 0.05%, the niobium content is 0.06%, the nitrogen content is 0.0050% and other alloy elements, and the produced product requires a X70 hot-rolled steel strip with a thickness of 17.5mm. The specific process parameters of each process are as follows:

[0042] (1) The slab reheating temperature is 1180°C;

[0043] (2) The rough rolling single pass reduction rate is 20%;

[0044] (3) The final rolling temperature is 800°C;

[0045] (4) The cumulative reduction rate of finishing rolling is 71%;

[0046] (3) The coiling temperature is 550°C;

[0047] (4) The cooling rate is 15°C / s.

[0048] The DWTT performance of the hot-rolled steel strip produced by the method described in Example 3 is shown in Steel 3 in Table 1.

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Abstract

The invention provides a hot rolling process capable of improving high-grade thick pipeline steel fracture toughness, sequentially comprising a plate blank reheating section process, a hot rolling section process, a plate reeling section process and a cooling section process, wherein the concrete processing parameters of each process are as follows: in the plate blank reheating section process, the plate blank heating temperature is equal to T solid solution plus 30-80 DEG C, the relation between in-furnace time and blank thickness is that the total in-furnace time is equal to 0.5t plus 30-50min, and the temperature difference of the upper surface and the lower surface after the plate blank is reheated is less than or equal to 30 DEG C; and in the hot rolling section process, the single track down rate in rough rolling is more than or equal to 15%, the accumulated down rate in fine rolling is more than or equal to 70%, and the finished rolling temperature is equal to Ar3 plus 0-60 DEG C, wherein Ar3 is a phase transformation point temperature. By utilizing the hot rolling process provided by the invention, the problem that DWTT (drop weight tear test) control is difficult to carry out on X70 and X80 steel more than 15mm can be effectively solved. The hot rolling process provided by the invention is practical and feasible and produces less loss on a rolling machine, a reeling machine and the like, and the qualifying rate of the DWTT properties of a product can reach up to more than 99%.

Description

technical field [0001] The invention relates to a hot-rolling process, in particular to a hot-rolling process for high-grade and thick-gauge pipeline steel, in particular to a hot-rolling process for high-steel grade above X70 and thick-gauge pipeline steel above 15 mm. Background technique [0002] Oil and natural gas are important strategic materials for the national economy. The growth of energy and structural optimization and adjustment have driven the overall development of the oil and gas industry. After the Second World War, oil and gas transmission pipelines developed rapidly, and the transmission pressure continued to increase. The design working pressure of new natural gas pipelines abroad is above 10MPa. X70 and X80 steel grades have become the general trend of pipeline steel pipe development. [0003] DWTT (Drop Weight Tear Test) performance is an important and necessary indicator for the quality requirements of gas pipeline steel. DWTT uses full-thickness samp...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B21B1/26
Inventor 孔君华郑琳周一中黄为民郭斌刘小国刘有健
Owner 武钢集团有限公司
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