CN87102390B

CN87102390B - Stronger sulfuric acid-resisting stainless steel

Info

Publication number: CN87102390B
Application number: CN87102390A
Authority: CN
Inventors: 杨长强; 杨薇; 陆世英; 康喜范; 张廷凯
Original assignee: Central Iron and Steel Research Institute
Current assignee: Central Iron and Steel Research Institute
Priority date: 1987-04-01
Filing date: 1987-04-01
Publication date: 1988-01-27
Also published as: CN87102390A

Abstract

The present invention relates to iron base Ni-Cr-Si-Mo-Cu austenite stainless steel which is mainly suitable for high-corrosion environments, such as environments of high-temperature and high-concentration sulfuric acid, etc. On the basis of Mo and Cu compound action, the steel obtains a good anticorrosion property in high-temperature and high-concentration sulfuric acid by controlling the content of Cr and increasing the content of Si. The corrosion rate of the steel is less than 0.01 mm/year in 98 % H2SO4 at the temperature of 100 DEG C. In addition, the stainless steel of the present invention has the advantages of good hot-processing property and cold-processing property and good mechanical property.

Description

Stronger sulfuric acid-resisting stainless steel

The invention belongs to field of alloy steel, is a kind of iron-based Ni-Cr-Si-Mo-Cu austenitic stainless steel.Mainly be applicable to harsh corrosive environments such as high-temperature high concentration sulfuric acid.

Sulfuric acid is the very strong very complicated technology acid of a kind of corrodibility, is industrial important basic material.

In gas washing in SA production, exist the problem of materials of equipment for a long time, particularly require High Temperature High Pressure recently, problem of materials is more outstanding, once uses carbon steel, cast iron and high-class stainless steel etc. in early days.Though these materials have certain solidity to corrosion in the vitriol oil under the low temperature, in the high-concentration sulfuric acid at high temperature, then suffer serious corrosion, so that can not use.At the etching condition of high humidity high-concentration sulfuric acid harshness, two-phase alloys has successively been studied and used in countries in the world (as the Cr25Ni of Japan ₅Mo ₂, Cr ₁₇Ni ₇Si ₄MoCu), austenitic stainless steel is (as the Cr of Sweden ₁₈Ni ₂₅Mo ₅, the Carponter20 of the U.S. and Wortaite, the 306L of West Germany, the Cr of Japan ₂₃Ni ₅₂Si ₄Mo ₄Cu ₄) etc.These materials, even high nickel corrosion-resistant alloy (as composition is Ni50～60%, Cr20～25%, Mo4～6%, the alloy of Cu3～6%), the concentration more than 100 ℃ greater than 93% the vitriol oil in, also have higher corrosion rate, still can not satisfy service requirements.Therefore, high temperature resistant high-concentration sulfuric acid has become problem of materials anxious to be solved in the gas washing in SA production in recent ten years with steel.

1981, a day spy of the present disclosure opened clear 56-93860 and has narrated a kind of high temperature resistant sulfuric acid stainless steel, and its chemical ingredients (weight percent) is: C≤0.10%, Si3.5～5.0%, Cr18.0～29.0%, Ni20.0-45.0%, Mo4.0～9.0%, Cu0.5～3.0%, Mn≤2.0%.The microstructure of this steel is an austenite, have favorable mechanical performance and solidity to corrosion preferably, but still there is following problem in＜DP 〉:

(1) because Si≤5%, so though there is high Mo to add the compound action of Cu, when the temperature of the vitriol oil during greater than 100 ℃, corrosion rate sharply increases, and for example is 100 ℃ 98%H in temperature ₂SO ₄In, its corrosion rate＞0.1 millimeter/year, in the time of 120 ℃, corrosion rate＞0.2 millimeter/year.

(2) contain higher Cr, Mo, Si in the alloy,, need to add a large amount of Ni, make the alloying element total content of alloy reach 80%, cause hot workability relatively poor, and cost increases therefore in order to obtain single-phase austenite structure.

(3) under high Cr, Mo condition, Si content is necessary≤and 5.0%, otherwise, hot workability and mechanical property will be worsened.Yet Si improves alloy corrosion proof important element in high-temperature concentrated sulfuric acid.In this alloy system, Si content is restricted.

The object of the present invention is to provide a kind of excellent corrosion resistance that in high-temperature concentrated sulfuric acid, has, casting easily, the cold and hot working performance is good, is adapted to the sulfuric acid industry development need, and cheap high temperature resistant vitriol oil stainless steel.

In order to satisfy above-mentioned requirements, the present invention has considered Cr, Si, Mo, Cu and the vital role of Ni element in steel, has paid attention to the effect of Si especially.It has been generally acknowledged that, in high Cr, Mo steel, Si content is necessary≤and 5.0%, otherwise, will cause hot workability and mechanical property to worsen.In fact, Si improves steel solidity to corrosion and the most important element of passive film stability in high-temperature concentrated sulfuric acid, Si content should increase along with the raising of vitriol oil temperature, when temperature during greater than 100 ℃, Si content should be greater than 5.5% in the steel under the Cr that is complementary, Mo, Cu content, Si content is higher, and the solidity to corrosion of steel in high-temperature concentrated sulfuric acid better.Cr makes steel easily oxidation in Oxidant, but based on the passive film of Cr, and instability extremely in high-temperature concentrated sulfuric acid will be dissolved rapidly.Si in steel＞5.5%, Cr 〉=7.8%, and add an amount of Mo, Cu, and just can obtain stable passive film, guarantee the solidity to corrosion of steel.Too high Cr content is skimble-skamble for the solidity to corrosion of high-temperature concentrated sulfuric acid; And the Cr height will limit the raising of Si content, if non-raising Si content just must further improve Ni content.And under the high situation of Cr, Mo content, add a large amount of Si, and in the steel fragility phase will appear then, and hot workability and mechanical property are worsened.The present invention makes Si to bring up to more than 5.5%, so that obtain the best solidity to corrosion in high-temperature concentrated sulfuric acid by the lower Cr content of control.Ni is an austenite former, and when Cr is 7.8～9.8%, Si is 5.5～8.0%, and Mo under 1.5～2.5% the situation, only needs to add 16～25%Ni, just can obtain single austenite structure, and it is unhelpful that too high Ni measures solidity to corrosion.In order to obtain the good solidity to corrosion and the stability of passive film, also should add an amount of Mo and Cu.

For the above reasons, the present invention proposes a kind of novel high temperature resistant vitriol oil, and the stainless steel of less expensive, its concrete chemical ingredients (weight percent) is: C trace～0.03%, Cr7.80～9.80%, Ni16.0～25.0%, Si5.5～8.0%, Mo1.5～2.5%, Cu0.8～1.8%Mn≤0.80%, surplus is Fe.

The present invention can adopt high frequency and medium-frequency induction furnace, vacuum induction furnace, electric arc furnace, external refining stove (VOD, AOD method) to smelt.Hot-work can be adopted forging or rolling, and opening forging (or open rolling) temperature is 900～1150 ℃, and finish-forging (or finish to gauge) temperature is greater than 800 ℃.According to taking all factors into consideration tissue, solidity to corrosion and mechanical property, the solid solubility temperature of this steel can be controlled in 1080～1130 ℃ of scopes, and the type of cooling adopts air cooling, water-cooled.This steel can be produced foundry goods, sheet material, bar, silk, steel band etc.

The present invention opens clear 56-93860 with the spy of Japan and compares, and Cr, Mo content greatly reduce, and only is its 1/2～1/4; Si content significantly improves, and near its 2 times, Ni content obviously reduces, and only is its 1/2.Although the total content of alloying element of the present invention is significantly less than the spy and opens clear 56-93860, cost is low, and solidity to corrosion is far superior to it.The present invention is at 98%H ₂SO ₄In, corrosion rate＜0.01 under 100 ℃ of temperature millimeter/year, 1/10 of clear 56-93860 is only opened for special in corrosion rate≤0.05 millimeter/year under 130 ℃ of temperature, and promptly solidity to corrosion has improved more than 10 times.Corrosion proof concrete data can see Table 2 and table 3.

The present invention also has good cold and hot working performance except having excellent high temperature resistance vitriol oil corrosive nature, can produce goods such as foundry goods, sheet material, bar, silk or band.Simultaneously, also has excellent mechanical property.After this steel cold and hot working was become a useful person, through under 1100 ℃ of temperature, after the thermal treatment of water-cooled was carried out in insulation in 30 minutes, its room-temperature mechanical property can reach: σ _b＞55 kilograms/millimeter ², σ _{α 2}＞24 kilograms/millimeter ², δ＞40%, ψ＞50%.

In sum, the present invention is the comparatively ideal material that is applicable in the harsh corrosive medium of high-temperature concentrated sulfuric acid, has broad application prospects.

Embodiment

The chemical ingredients scope that sets according to the present invention has been smelted 5 stove steel on vacuum induction furnace, its concrete chemical ingredients sees Table 1.After 5 stove steel poured into 10 kilogram weight ingots respectively, forging rolling became the bar of 20 millimeters of φ and 4 * 25 millimeters bar, and the forging rolling Heating temperature is 1100 ℃.Forge the solution treatment 30 minutes under 1100 ℃ of temperature of good rod, bar, and water-cooled.Test portion after treatment is processed into standard corrosion sample, then respectively at 98%H ₂SO ₄And 93%H ₂SO ₄In carry out accelerated corrosion test, test is to carry out in taking back the special glass tap web bottle that revolves condenser, test temperature has been selected 90,100,120 and 130 ℃.Test-results is listed table 2 and table 3 in.Table 4 is the test-results of mechanical property.

In order to contrast, present embodiment has also been smelted the similar contrast grade of steel of Japan, the U.S., West Germany, five countries of the Soviet Union and Sweden simultaneously, after hot-work and thermal treatment, with sample of the present invention, carries out accelerated corrosion test simultaneously.The condition of smelting, hot-work, thermal treatment and the corrosion test etc. of contrast grade of steel, all just the same with the present invention, and carry out simultaneously.The concrete chemical ingredients of contrast grade of steel is listed table 1 in, and its solidity to corrosion is listed table 2 and table 3 in.

Table 1 the present invention and the chemical ingredients that contrasts grade of steel

Alloy number		Heat treating regime	σ _ｂKilogram/millimeter ²	σ _α２Kilogram/millimeter ^２	δ%	ψ%
							The present invention	2	1100 ℃ of 30 fens water-cooleds	75.2	26.2	47.9	58.3
5	76.3	25.8	46.8	57.6

Claims

1, a kind of stronger sulfuric acid-resisting stainless steel is characterized in that chemical ingredients (weight %) by C trace～0.03%, Cr7.80～9.80%, and Ni16.0～25.0%, Si5.5～8.0%, Mo1.5～2.5%, Cu0.8～1.8%, Mn≤0.80% surplusly is that Fe forms.