JPS60238452A - Cr-mo steel for pressure vessel - Google Patents

Abstract

PURPOSE:To improve remarkably the toughness of a high strength Cr-Mo steel as well as the resistance to SR cracking and erosion by hydrogen by extremely reducing the amount of S in the steel contg. a little Si, V and Nb as essential components. CONSTITUTION:The composition of the high strength Cr-Mo steel for a pressure vessel is composed of, by weight, 0.08-0.18% C, <0.1% Si, 0.05-1% Mn, 2-5% Cr, 0.8-1.5% Mo, 0.2-0.5% V, 0.005-0.05% Nb, <0.001% S and the balance Fe with inevitable impurities.

Description

[Detailed Description of the Invention] (Technical Field) The technical content described in this book is particularly applicable to operations in high-temperature, high-pressure hydrogen atmospheres such as oil refining plants, petrochemical plants, and coal liquefaction plants. The present invention proposes an Or-Mo steel for pressure vessels that has improved corrosion resistance and hydrogen corrosion resistance.

(Background Technique WI) Or-MofIA is often used as a material for equipment in the above-mentioned plants operated in a high temperature, high pressure hydrogen atmosphere.

In these plants, there is a trend to increase operating conditions at high temperatures and high pressures and to increase the size of equipment in order to improve efficiency, and Or-MOtA with excellent high wettability is becoming necessary.

(Conventional technology WI) In order to increase high-temperature strength, it is effective to add precipitation-strengthening elements.
, Nb addition, and V addition is shown in JP-A-55-82752%.

Also, these elements have a low resistance to reaction with hydrogen.
J Lehner standing - φ closing table is i - Kisaki ☆ Guha ↓ ★ Mountain ・ It also has the effect of increasing resistance to material deterioration, that is, hydrogen erosion.

However, elements such as V and Nb form carbonitrides and exhibit precipitation strengthening, which deteriorates toughness and weldability.

Therefore, with the conventional method of simply adding these elements, there is still room for improvement in terms of overall properties such as strength, toughness, weldability, and hydrogen corrosion resistance. It was necessary to stably improve the overall characteristics by improving the characteristics of the
- S in high strength Cr-Mo steel based on Nb
It has been found that the toughness, SR cracking resistance and hydrogen attack resistance can be significantly improved by significantly reducing the . Based on this knowledge, it is an object of the present invention to comprehensively improve the above-mentioned properties.

(Structure of the Invention) This invention has a weight ratio of 0±0.08 to 0.18: less than 0.10 vt ratio, Mn: 0.05 to 1. OWt sound Or: g, o ~ s, o wt 5 M0j 0.8 ~ 1.5vrt Sorry V + '0.20 ~ 0.50 wt % and ab
: 0.0ofi ~ 0.050 vrt* including 8
: Less than 0.0010 wt noise, with the remainder being Fo and impurities.This is an Or-Mo steel for pressure vessels that has excellent toughness, SR cracking resistance, and hydrogen corrosion resistance.

First, the reason why the composition range of the high-strength Or-Mo steel is limited in this invention is as follows.

0: A minimum content of 0.08% is necessary to ensure strength, but since it deteriorates toughness and weldability, the content should be 0.18% or less.

Si: increases tensile strength, but degrades creep rupture strength, resistance to fire and embrittlement, and resistance to hydrogen corrosion7'1
It was set to be less than 1.101.

・Mn: Minimum 0.0 to improve hardenability and strength
5% is necessary, but it increases the susceptibility to tempering brittleness, so 1. It was set to be less than Os.

Or = At least 2.0% is necessary to improve strength, oxidation resistance, and hydrogen corrosion resistance, but it is set to 5.016 or less because it reduces creep rupture strength.

M. = At least 0.8% is necessary to increase strength, but since it deteriorates weldability and toughness, it is set to a coefficient of 1.5 or less.

V: Minimum o, go% is necessary to increase high temperature strength.
□, but it deteriorates the toughness and weldability, so 0.50
% or less.

1(b!) 0.005-0.050% addition is required to increase high temperature strength without increasing SR cracking susceptibility.

If the lifting platform is less than 0.005%, the above effects cannot be obtained, and o,
Even if added in excess of o5o*, no significant increase in high-temperature strength can be expected, and the toughness, especially the HAZ toughness, deteriorates. Also, during the production of large steel ingots, huge Nb carbonitrides crystallize and deteriorate the toughness.

L LI n) tr 'L 7r 'kTh t--
) J shi & +j −/ tk mackerel E; &# M
71L ``e'', it is preferable to add a larger amount of 1 to steel containing a large amount of Or, which is easily oxidized.

S: It has long been known that reducing S will improve toughness ◇However, conventional research on S has only been conducted up to about 0.0014, so it is unclear what kind of effect will appear when S is further reduced. Met.

In this regard, V, high strength Or- containing Nb.

As a result of research using steel, it was found that reducing S to less than 0.0010% can significantly improve toughness, suppress SR cracking, which is a particular problem with high-strength steel, and improve hydrogen corrosion resistance. It turned out that.

The Or-Mom for pressure vessels of this invention is manufactured through the following steps.

Steel ingot ◆ Hot rolled or hot forged ↓ Normalized, quenched, normalized, green quenched, or normalized, green quenched, green quenched, tempered - The steel of this invention can be made by hot rolling or hot forging. After processing by inter-forging or both, pre-treatments such as normalizing and tempering are performed as necessary, and finally tempering treatments such as normalizing, tempering and tempering, and quenching and tempering are carried out. It has excellent properties when subjected to the manufacturing process normally applied to steel materials for pressure vessels.

Next, examples of the present invention will be listed and their performance will be compared with conventional steel.

(Example) The test steel shown in Table 1 was tested under the following conditions, and the results are also listed in Table 1.

695℃X1hSR ↓ SR cracking test (section cracking rate) - The invented steel has high strength and is excellent in toughness, SR cracking resistance, and hydrogen erosion resistance.

(Effects of the Invention) According to the present invention, there is provided an Or-M for pressure vessels. This results in significant improvements in the toughness, SR cracking resistance, and hydrogen corrosion resistance of the steel.

Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] 1-0: 0.08-0.18 wt ratio Si' less than 0-10 wt% Mn: O, T15-1.0 Wtl Cr72.0-5. Owt s M. =0.8~1.5wt% V: 0.20~o, 5wt and Nb! 0.
005~0.05o wt@ including S j O,00
An Or-Mo steel for pressure vessels having a weight of less than 10 Wt 1, with the balance consisting of Fe and impurities, and excellent in toughness, SR cracking resistance, and hydrogen corrosion resistance.