CN102230137A

CN102230137A - Austenitic heat-resistant stainless steel and processing method thereof

Info

Publication number: CN102230137A
Application number: CN2011101657017A
Authority: CN
Inventors: 张智丹; 刘焕安; 欧阳明辉
Original assignee: XUANDA INDUSTRIAL GROUP Co Ltd
Current assignee: XUANDA INDUSTRIAL GROUP Co Ltd
Priority date: 2011-06-20
Filing date: 2011-06-20
Publication date: 2011-11-02

Abstract

The invention relates to austenitic stainless steel, and in particular relates to austenitic heat-resistant stainless steel and a processing method thereof. The austenitic heat-resistant stainless steel is characterized by comprising the following elements by mass percentage: 0.25-0.45% of carbon, 0.5-2% of silicon, 0.5-2% of manganese, 23-27% of chromium, 6-10% of nickel, 0.15-0.3% of nitrogen, 0.1-0.5% of rare-earth (RE) elements and the balance of iron. The austenitic heat-resistant stainless steel obtained by the processing method has the advantages of good high-temperature oxidation resistance, good carburizing resistance, good sulfurization corrosion resistance and lowered production cost.

Description

Austenite heat-resistance stainless steel and working method thereof

Technical field

The present invention relates to a kind of austenitic stainless steel, particularly a kind of austenite heat-resistance stainless steel and working method thereof.

Background technology

Austenitic stainless steel is meant the stainless steel that has austenite structure at normal temperatures.Contain in the steel that Cr is about 18%, about 0.1% o'clock of Ni 8% ~ 10%, C, have stable austenite structure.Austenitic chromium nickel stainless steel comprises famous 18Cr-8Ni steel and increases Cr, Ni content on this basis and add the high Cr-Ni Series Steel that elements such as Mo, Cu, Si, Nb, Ti grow up.This type of austenitic stainless steel is widely used in industrial sectors such as metallurgy, electric power, oil, chemical industry, as the boiler burner in fuel-burning power plant, heat-resistant pieces such as high temperature regulation and control butterfly valve in the sulphur-burning sulphuric acid system.These high temperature steel component at high temperature with oxidizing gas (O ₂, H ₂O, CO ₂, SO ₂Deng) when contact, oxidizing reaction can take place, to work-ing life of industrial production and component all producing adverse influence,, could satisfy the requirement of its use properties so require material to have good high-temperature intensity and high temperature oxidation resistance.The heat-resistant and wear-resistant material that is widely used in industries such as metallurgy, electric power, mine, building materials at present is 4Cr25Ni20, and this steel exists 900～1200 ℃Between show good thermotolerance and oxidation-resistance.But because its nickel content height, cost is higher.Under current international nickel valency goes up by swift and violent situation, develop a kind of low nickel, high temperature steel has bigger economic and social benefit cheaply.

Summary of the invention

Deficiency at prior art exists the invention provides a kind of have good high-temperature oxidation-resistance, anti-carburizing and anti-sulphur corrosion ability, austenite heat-resistance stainless steel that reduces production costs and working method thereof.

For achieving the above object, the invention provides following technical scheme: a kind of austenite heat-resistance stainless steel, it is characterized in that: include carbon, silicon, manganese, chromium, nickel, nitrogen and rare earth element, each component is by mass percentage: carbon: 0.25～0.45%, silicon: 0.5～2%, manganese: 0.5～2%, chromium: 23～27%, nickel: 6～10%, nitrogen: 0.15～0.3%, rare earth element: 0.1～0.5%, and surplus is an iron.

In such scheme, form the stable and fine and close Cr of one deck on the surface of steel ₂O ₃, SiO ₂Film, can be firm be attached to metallic surface, thereby protect metal to avoid the oxidation of high-temperature gas and the corrosion of medium effectively.Replenish the austenitic heat-resistance steel of alloying simultaneously with elements such as silicon, nitrogen and rare earths, have higher high temperature strength and structure stability and resistance to thermal shocks; Especially have good high-temperature oxidation-resistance, anti-carburizing and anti-sulphur corrosion ability; Maximum operation (service) temperature is 1200 ℃ 900～1200 ℃Its salient features surpasses traditional high temperature steel; Have good hot workability, can produce products such as plate, rod; And precious metal element significantly reduces, and reduced the cost of material.

And the effect of the various element manipulated variables in the such scheme is as follows:

Carbon is controlled at 0.25～0.45%: carbon is to enlarge the austenitic area element, and is very big to the performance impact of steel.Carbon can and element (as Cr, Ti, WDeng) form carbide, be the principal element that guarantees hot strength.The too high meeting of carbon content causes material plasticity, toughness and intensity to descend significantly, the machining difficulty, and welding easily cracks.For the over-all properties of material, carbon is controlled at 0. 25～0.45%.

Adding chromium is controlled at 23～27%: chromium is the one of the chief elements of resistance to high temperature oxidation and resistance to high temperature corrosion in the high temperature steel, and can improve hot strength of heat resistant steel.When chrome content is enough high in the steel, can form one deck densification in its surface Cr ₂ O ₃Film, this oxide film can stop corrosive gasess such as oxygen, sulphur, nitrogen to spread in steel to a certain extent, also can hinder metal ion to external diffusion.Along with the increase of chromium amount, the antioxidant property of steel improves.Definite through testing, with Cr content be 23～27%.

Nickel is one of alloying element important in the high temperature steel, and it mainly acts on is to promote and the stable austenite tissue, guarantees that steel has high-temperature oxidation resistance and good processing properties preferably.Consider austenite elements such as having added carbon, manganese, nitrogen, the add-on of nickel is 6～10%

Silicon can be in high chromium steel surface forms the silicon oxide densification oxidation film layer, it with Cr ₂ O ₃Be that main compact oxidation layer is resisted the oxidation to steel jointly, thereby increased the resistance of oxidation of steel.But silicone content is too high, will significantly reduce the plasticity and the toughness of steel, the too high weldability that also reduces steel of silicone content.So silicone content is controlled at 0.5～2%.

Manganese belongs to the austenite element, also can increase the solubleness of nitrogen in steel, thereby plays stable austenite in nitrogenous steel.But too high levels can impair antioxidant property and reduce creeping limit, is defined as through experiment 0.5～2%.

Nitrogen is similar a bit as effect and the carbon of alloy element in Austenitic high temperature steel.Nitrogen can enlarge the austenite phase region, and is also stronger than carbon to austenitic stabilization.Nitrogen can improve steel hardenability, reduces the superheated susceptivity of steel, can also strengthen the stability of carbide simultaneously.Along with nitrogen content increases, the room temperature strength of steel and hot strength improve, and unit elongation and yield tensile ratio significantly reduce; Ferrite content obviously reduces, and the nitride amount of separating out increases, the obvious refinement of the grain fineness number of steel.But nitrogen in steel too high levels, steel ingot surface in forging process is easy to crack, thereby its surface quality of remarkably influenced.According to experiment, suitable between nitrogen content should control 0.15%～0.3% in the high temperature steel.

Rare earth element has more significantly effect to the antioxidant property that improves high temperature steel.The oxide compound of rare earth element can increase the sticking power between matrix metal and the oxide film, because rare earth oxide has " pinning " effect to matrix metal.Rare earth lanthanum and cerium can reduce Cr ₂O ₃Volatility, improve the composition of oxide compound, become more stable (Cr, La) ₂O ₃Oxide film.Rare earth element is good desulfurization getter in the steel also, can remove other (as arsenic, antimony, bismuth etc.) detrimental impurity, can improve the shape and the distribution of steel inclusion, thereby improve the quality and the resistance toheat of steel.Rare earth element is too much, can play the effect of polluting molten steel, so the add-on of rare earth element is controlled at 0.1～0.5%.

The present invention processes the amplification technical scheme that adopts: processing can adopt hammer cogging to add rolling mode, wherein opens and forges 1120 ℃～1150 ℃ of temperature, and final forging temperature is 950 ℃～1200 ℃; Start rolling temperature is 1160 ℃～1200 ℃, and finishing temperature is 1000 ℃～1200 ℃.

The further technical scheme of working method is: stainless solid solution temperature is 1150 ℃～1200 ℃, and the type of cooling after the solution treatment is water-cooled or air cooling.

Below in conjunction with accompanying drawing the present invention is further described.

Description of drawings

Fig. 1 be in the embodiment of the invention high-temperature oxidation resistance with 25-20The comparison diagram of high temperature steel;

Fig. 2 amplifies 40 times steel cast structure metallograph 1 in the embodiment of the invention;

Fig. 3 amplifies 100 times steel cast structure metallograph 2 in the embodiment of the invention.

Embodiment

The present invention is a kind of austenite heat-resistance stainless steel, include carbon, silicon, manganese, chromium, nickel, nitrogen and rare earth element, each component is by mass percentage: carbon: 0.25～0.45%, silicon: 0.5～2%, manganese: 0.5～2%, chromium: 23～27%, nickel: 6～10%, nitrogen: 0.15～0.3%, rare earth element: 0.1～0.5%, and surplus is an iron.

With the medium-frequency induction furnace three stove steel of casting, its chemical ingredients is as shown in table 1:

Table 1 is enumerated the proportioning of three groups of different masies within the scope of the present invention

?

C

Cr

Ni

Si

Mn

N

RE

Fe

NO.1

0.33

26.20

8.62

1.50

1.23

0.21

0.42

Surplus

NO.2

0.38

25.98.

8.40

1.43

1.30

0.17

0.44

Surplus

NO.3

0.35

26.13

8.51

1.61

1.28

0.19

0.40

Surplus

After the stove smelting steel became ESR ingot, forging rolling became the bar of Φ 50.Forging temperature is 1130 ℃, and rolling temperature is 1170 ℃, and solid solution temperature is 1180 ℃, water-cooled after the solution treatment.

Bar after the solution treatment is carried out sampling analysis, and mechanical property, tensile strength test experimentize by metal material at high temperature stretching experiment method GB/T4338-2006, the results are shown in Table 2.Table 3 is comparisons of hot strength of the present invention and 4Cr25NI20 high temperature steel hot strength.

Bar after the solution treatment is carried out sampling analysis, oxidation resistance test GB/T13303-91 carries out, and sample is 60mm * 30mm, insulation 500h in oxidizing atmosphere (placing brown iron oxide in the stove), measure sample oxidation weight gain speed, test-results such as Fig. 1.

Bar after the solution treatment is carried out sampling analysis, the optical microstructure of its as cast condition such as Fig. 2, shown in Figure 3.As can be seen, its as-cast structure matrix is an austenite, and a spot of ferrite and be netted carbide is distributing on it.Austenitic matrix makes steel have good high-temperature oxidation resistance, and carbide has guaranteed steel intensity at high temperature.

Table 2 high temperature steel mechanical behavior under high temperature of the present invention

Test temperature, ℃	σ _b ，? MPa	δ，? %
			500	559	30.4
600	516	28.8
			700	432	20.2
800	326	12.2
			900	220	13.0
1000	130	17.0
			1100	65	37.0
1200	31	30.2

Table 3 hot strength of the present invention with 4Cr25Ni20The high temperature steel comparison ( σ b, MPa)

Steel grade	900℃	1000℃	1100℃	1200℃
					The present invention	220	130	65	31
4Cr25Ni20	157	101	---	---

Can see that by table 2, table 3 and Fig. 1 high temperature steel of the present invention has ratio 25-20The high hot strength of tradition high temperature steel.High-temperature oxidation resistance especially 1200 ℃Antioxidant property is far superior to traditional high temperature steel 4Cr25Ni20Experimental results show that high temperature steel manufacturing of the present invention 1200 ℃The heat-resistant pieces such as valve plate, valve shaft and trip bolt of high temperature regulation and control butterfly valve are respond well very successful.This high temperature steel not only can be used for making high temperature regulation and control butterfly valve and can be applied to other hot environment, decreases gate valve etc. as Coal Chemical Industry with heat resistant and wear resistant.

Claims

1. austenite heat-resistance stainless steel, it is characterized in that: include carbon, silicon, manganese, chromium, nickel, nitrogen and rare earth element, each component is by mass percentage: carbon: 0.25～0.45%, silicon: 0.5～2%, manganese: 0.5～2%, chromium: 23～27%, nickel: 6～10%, nitrogen: 0.15～0.3%, rare earth element: 0.1～0.5%, and surplus is an iron.

2. the working method of an austenite heat-resistance stainless steel, it is characterized in that: processing can adopt hammer cogging to add rolling mode, wherein opens and forges 1120 ℃～1150 ℃ of temperature, and final forging temperature is 950 ℃～1200 ℃; Start rolling temperature is 1160 ℃～1200 ℃, and finishing temperature is 1000 ℃～1200 ℃.

3. the working method of austenite heat-resistance stainless steel according to claim 2, it is characterized in that: stainless solid solution temperature is 1150 ℃～1200 ℃, and the type of cooling after the solution treatment is water-cooled or air cooling.