Welding wire for modified 9Cr-1Mo steel, and submerged-arc welding material

Inactive Publication Date: 2005-11-24
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] The present invention has been accomplished in view of those problems encountered with the prior art, and it is an object of the invention to provide a wel

Problems solved by technology

The above-mentioned prior art, however, has the following problems.
Thus, in some welding processes in other countries, the PWHT temperature is intended to be set to 760° C. for the purpose of improving the creep rupture strength and toughness, and the PWHT temperature is often increased until the actual temperature reaches 780° C. In this case, a problem of the Acl transformation temperature for a deposited metal arises.
Concretely, when the PWHT is carried out at a temperature above the Acl transformation temperature of the deposited metal, phase transformation occurs in the deposited metal, resulting in a danger that the creep rupture strength may be significantly degraded.
Furthermore, as

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Example

EXAMPLE

[0068] Now, effects of the examples according to the invention will be explained by comparing with comparative examples, which depart from the scope of the invention. First, the welding wires with compositions shown in the following Tables 1 and 2 were used as first examples of the invention. A sample steel plate with a composition shown in Table 3, and having a thickness of 20 mm, a groove angle of 45 degrees, and a root gap of 13 mm, was welded using each of the above-mentioned welding wires in the submerged arc welding process under a condition shown in the following Table 4. The toughness and creep rupture strength of each of the thus-obtained weld metals were evaluated. The following Table 5 shows a composition of a combination flux. The combination flux was obtained by granulating flux raw materials and a water glass as a binder, sintering them at 500 to 550° C. for one hour, so that the content of 10×48 mesh grains in the whole flux was 70% by mass or more. Note that ...

Example

[0082] As shown in the above Tables 6 and 7, in the wire of the comparative example No. W1, the C content was less than that covered by the scope of the invention. Thus, the strength of the wire was insufficient, and the creep rupture time did not satisfy a predetermined requirement of performance. In the wire of the comparative example No. W2, the C content exceeded that covered by the scope of the invention, thus leading to occurrence of hot cracking in the radiographic testing. In the wire of the comparative example No. W3, since the Si content was less than that covered by the scope of the invention, the deposited metal lacked deoxidation, and the toughness of the weld metal did not satisfy the predetermined requirement of performance. In the wire of the comparative example No. W4, since the Si content exceeded that covered by the scope of the invention, the δ-ferrite remained in the weld metal, and the toughness did not satisfy the predetermined requirement of performance. In t...

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Abstract

A welding wire for a modified 9Cr-1Mo steel is provided which comprises C: 0.070 to 0.150% by mass, Si: more than 0.15% by mass, but not more than 0.30% by mass, Mn: not less than 0.30% by mass, but less than 0.85% by mass, Ni: 0.30 to 1.20% by mass, Cr: 8.00 to 13.00% by mass, Mo: 0.30 to 1.40% by mass, V: 0.03 to 0.40% by mass, Nb: 0.01 to 0.15% by mass, N: 0.016 to 0.055% by mass, P: not more than 0.010% by mass, S: not more than 0.010% by mass, Cu: less than 0.50% by mass, Ti: not more than 0.010% by mass, Al: less than 0.10% by mass, B: less than 0.0010% by mass, W: less than 0.10% by mass, Co: less than 1.00% by mass, and O: not more than 0.03% by mass, wherein the total amount of Mn and Ni being not more than 1.50%. The welding wire provides good toughness without degradation of creep rupture strength even at the PWHT temperature of 760° C. or above.

Description

FIELD OF THE INVENTION [0001] The present invention relates to welding wires for welding modified 9Cr-1Mo steels, which are used for various types of heat-resistant and pressure-resistant piping, including a boiler for power generation, a turbine, and the like. More particularly, the invention relates to welding wires for modified 9Cr-1Mo steels, which are used for performing a submerged arc welding (SAW) process of the modified 9Cr-1Mo steel, and / or a tungsten inert gas (TIG) welding process thereof, and to welding materials comprising the combination of the welding wire and a flux. BACKGROUND OF THE INVENTION [0002] A modified 9Cr-1Mo steel (hereinafter referred to as “Mod.9Cr-1Mo steel”) is made of a 9Cr-1Mo steel with Nb and V added thereto. For example, the modified 9Cr-1Mo steel is SA387Gr.91, or SA213Gr.T91, which is specified in the American Society for Testing and Materials (ASTM) Specification / American Society of Mechanical Engineers (ASME) Specification, X10CrMoVNb9-1, wh...

Claims

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Application Information

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IPC IPC(8): B23K35/30B23K35/362C22C38/48
CPCB23K35/0255B23K35/3086B23K35/3605B23K2203/04C22C38/48C22C38/04C22C38/44C22C38/46C22C38/02B23K26/34B23K2103/04B23K2103/05B23K2103/18B23K9/167B23K9/18
Inventor YAMASHITA, KENHARA, NORIYUKIMURAKAMI, TOSHIOHATANO, HITOSHI
Owner KOBE STEEL LTD
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