Ultrafine-grain steel pipe and process for manufacturing the same

A manufacturing method and steel pipe technology, applied in metal rolling and other directions, can solve the problems of complicated process and reduced elongation

Inactive Publication Date: 2002-04-10
KAWASAKI STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the elongation of high-strength steel pipes increased by this method is reduced, so deep processing should be avoided. In the case of deep processing, intermediate annealing is required during processing, and then tempering or quenching and tempering heat treatment
However, heat treatment such as intermediate annealing complicates the process

Method used

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  • Ultrafine-grain steel pipe and process for manufacturing the same
  • Ultrafine-grain steel pipe and process for manufacturing the same
  • Ultrafine-grain steel pipe and process for manufacturing the same

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0141] The raw steel pipes with the chemical composition shown in Table 1 were heated to the temperature shown in Table 2 with induction heating coils, and then the product tubes were made into the product tubes with the rolling conditions shown in Table 2 by a tension reducer with 3-roll structure. The solid-phase pressure-welded steel pipes shown in Table 2 used steel pipes produced by preheating a 2.6 mm thick hot-rolled strip steel to 600°C, and then forming continuously with a plurality of forming rolls to obtain open pipes, followed by , use induction heating to preheat the two edges of the open tube to 1000°C, and then use induction heating to heat the two edges to 1450°C in the unmelted temperature zone, and use extrusion rollers to butt solid phase pressure welding to form φ42.7mm× 2.6mm thick steel pipe. In addition, as the seamless steel pipe, a seamless steel pipe obtained by heating a continuous casting slab and rolling by a Mannesmann mandrel method was used.

...

Embodiment 2

[0150] The raw steel pipes with the chemical composition shown in Table 3 were heated to the temperature shown in Table 4 with induction heating coils, and then the product tubes were made by using a 3-roll tension reducer according to the rolling conditions shown in Table 4. The manufacturing method of the raw material steel pipe is the same as in Example 1.

[0151] The tensile properties, impact impact properties and structures of these product tubes were investigated in the same manner as in Example 1, and the results are shown in Table 4.

[0152] As can be seen from Table 4, the examples of the present invention (No. 2-1~No. 2-3, No. 2-6~No. 2-8, No. 2-10~No. 2-14) in the scope of the present invention obtain ductility and strength Well-balanced steel pipe. Not only the tensile strength is high at high strain rates, but also the shock absorption energy for impact resistance is high. In contrast, Comparative Examples No. 2-4, No. 2-5, and No. 2-9, which are outside the ...

Embodiment 3

[0156] Raw steel pipes with the chemical composition shown in Table 5 were heated to the temperature shown in Table 6 with induction heating coils, and then processed into product pipes by tension reduction with 3-roll structure according to the rolling conditions shown in Table 6. The steel pipe used as the raw material in this example is a φ110 mm×4.5 mm thick steel pipe made of a hot-rolled steel sheet produced by controlled rolling and controlled cooling.

[0157] The tensile properties, impact impact properties, structure and sulfide stress corrosion cracking resistance of these product pipes were investigated, and the results are shown in Table 6. Similar to Example 1, the measurement of tensile properties used JIS No. 11 test piece. In addition, considering the size effect of the test piece, the value of the elongation is calculated according to E1=E1O×((aO / a)) 0.4 (In the formula, E1O: measured elongation, aO: 292mm 2 , a: area of ​​test piece (mm 2 )) Calculated c...

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Abstract

A steel pipe containing fine ferrite crystal grains, which has excellent toughness and ductility and good ductility-strength balance as well as superior collision impact resistance, and a method for producing the same are provided. A steel pipe containing super-fine crystal grains can be produced by heating a base steel pipe having ferrite grains with an average crystal diameter of di (mum), in which C, Si, Mn and Al are limited within proper ranges, and if necessary, Cu, Ni, Cr and Mo, or Nb, Ti, V, B, etc. are further added, at not higher than the Ac3 transformation point, and applying reducing at an average rolling temperature of thetam (DEG C) and a total reduction ratio Tred (%) within s temperature range of from 400 to Ac3 transformation point, with di, thetam and Tred being in a relation satisfying a prescribed equation.

Description

field of invention [0001] The present invention relates to a steel pipe with ultra-fine grain, high strength, high toughness, high ductility and excellent impact resistance against collision and its manufacturing method. Background of the invention [0002] In order to improve the strength of steel, it is common practice to add alloying elements such as Mn and Si or to further conduct heat treatments such as controlled rolling, controlled cooling, quenching and tempering, or to add precipitation hardening elements such as Nb and V. However, not only high strength but also good ductility and toughness are required for steel materials, and therefore there has been an urgent need for a steel material with a balanced improvement in strength, ductility, and toughness for a long time. [0003] Grain refinement is one of the few important means by which strength, ductility and toughness can be improved simultaneously. The methods of grain refinement include: prevent the coarsening...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D8/10
CPCC21D8/10C21D2201/00
Inventor 丰冈高明依藤章西森正德板谷元晶桥本裕二冈部能知金山太郎森田正彦松冈才二田中伸树古君修比良隆明
Owner KAWASAKI STEEL CORP
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