CN112760566A

CN112760566A - Novel high-strength corrosion-resistant 316L alloy

Info

Publication number: CN112760566A
Application number: CN202011559012.XA
Authority: CN
Inventors: 刘哲; 黄剑进
Original assignee: Shanghai Aeronautical Materials & Structures Testing Co ltd
Current assignee: Shanghai Aeronautical Materials & Structures Testing Co ltd
Priority date: 2020-12-25
Filing date: 2020-12-25
Publication date: 2021-05-07

Abstract

The invention discloses a novel high-strength corrosion-resistant 316L alloy which comprises the following chemical components that on the basis of standard chemical components of the 316L alloy, the content of carbon atoms is increased to 0.035-0.040%, and vanadium and titanium are added. The added alloy elements are common alloy elements, so that the cost is low, and the improved alloy cost has no obvious change; while improving the mechanical property of 316L alloy material, M₂₃C₆Phase and M₇C₃The precipitation amount is not greatly increased, so that the corrosion resistance of the alloy can be ensured.

Description

Novel high-strength corrosion-resistant 316L alloy

Technical Field

The invention belongs to the technical field of alloys, and particularly relates to a novel high-strength corrosion-resistant 316L alloy.

Background

The austenitic 316L alloy stainless steel is widely applied to the fields of chemical industry, petroleum, household and the like because of good processing performance and excellent corrosion resistance, and is one of the most widely used stainless steels with the largest output at present.

The 316L alloy is austenitic stainless steel developed by adding molybdenum element to 304L alloy, and the standard chemical composition (GB-T20878-:

TABLE 1, 316L alloy Standard chemical compositions

The 316L alloy has more excellent intergranular corrosion resistance, stress corrosion resistance and chloride corrosion resistance than the 304L alloy. Although the strength of the 316L alloy is improved to a certain extent compared with that of the 304L alloy, the strength of the alloy is still relatively lower compared with other stainless steels, and the yield strength is required to be more than or equal to 177MPa and the tensile strength is required to be more than or equal to 480MPa at room temperature, so that the use and development of the 316L alloy are restricted. Therefore, the mechanical property of the alloy is improved while the corrosion resistance of the alloy is not greatly influenced, the alloy has important significance for subsequent use and development of 306L alloy, and is particularly widely used in a service environment with less strict requirement on corrosion resistance but certain requirement on alloy strength.

For 316L alloy, if the carbon content in the alloy is too high, supersaturated carbon atoms are separated out by combining with chromium atoms in a matrix in the service process to form M₂₃C₆The phases, which form chromium-poor regions near grain boundaries, reduce the corrosion resistance of the alloy, possibly resulting in intergranular corrosion leading to material failure accidents, and thus reducing the carbon content can significantly improve the corrosion resistance of the alloy. However, the mechanical property of the alloy is reduced due to the reduction of the content of the carbon element, so that the strength of the 316L alloy cannot meet the service requirement, and the use scene is limited. Therefore, the method for obtaining the corrosion-resistant alloy with good corrosion resistance and high strength by adjusting the content of the alloy elements is simple, low in cost, strong in operability and high in economical efficiency and practicability in engineering application.

Disclosure of Invention

The invention aims to optimize the chemical components of the 316L alloy aiming at the limitations of the current 316L alloy in the aspects of mechanical properties such as strength and the like by combining the content range of the standard chemical components of the 316L alloy, thereby improving the mechanical properties of the 316L alloy on the premise of ensuring excellent corrosion resistance.

In order to achieve the purpose, the invention adopts the following technical scheme:

the chemical composition of the novel high-strength corrosion-resistant 316L alloy is that on the basis of the standard chemical composition of the 316L alloy, the content of carbon atoms is increased to 0.035-0.040%, and vanadium and titanium are added.

According to a preferred embodiment of the present invention, the content of the vanadium element is 0.05 ± 0.01%, and the content of the titanium element is 0.05 ± 0.01%.

The novel 316L alloy with high strength and corrosion resistance has the following beneficial effects:

1. the added alloy elements are common alloy elements, the cost is lower, and the improved alloy cost has no obvious change.

2. M is capable of improving mechanical property of 316L alloy material₂₃C₆Phase and M₇C₃The precipitation amount is not greatly increased, so that the corrosion resistance of the alloy can be ensured.

3. The grain size of the 316L alloy is refined, and the influence of the second phase precipitation of the alloy on the plasticity and toughness of the alloy can be counteracted to a certain extent by the fine-grain strengthening effect while the mechanical property is ensured.

Drawings

FIG. 1 is a metallographic photograph of the alloy of example 1.

FIG. 2 is a metallographic photograph of the alloy of example 2.

FIG. 3 is a metallographic photograph of the alloy of example 3.

FIG. 4 is a metallographic photograph of the alloy of example 4.

FIG. 5 is a metallographic photograph of the alloy of example 5.

FIG. 6 shows the results of the corrosion resistance tests of the alloys of examples 1, 2, 4 and 5, in which the abscissa is the value of the electrode passing current on the logarithmic scale and the ordinate is the electrode potential.

Detailed Description

The novel 316L alloy with high strength and corrosion resistance of the present invention will be described in further detail with reference to the following examples. It should be understood that the following examples are illustrative only and are not intended to limit the scope of the present invention.

Aiming at the limitation of the mechanical properties such as strength and the like of the current 316L alloy, the invention optimizes the chemical components of the alloy by combining the content range of the standard chemical components of the 316L alloy so as to improve the mechanical properties of the 316L alloy on the premise of ensuring excellent corrosion resistance.

The precipitated phase in the 316L alloy is mainly M₂₃C₆Phase and M₇C₃The amount of phases, which precipitate depends mainly on the carbon content of the alloy. As carbon atoms are interstitial solid solution atoms, the solubility in iron is low, the alloy strength is higher when the content of the carbon element is higher, but M is formed by the carbon atoms combined with chromium atoms in a matrix₂₃C₆Phase and M₇C₃The phase may cause chromium-poor regions in the alloy, resulting in a decrease in the corrosion resistance of the alloy.

After long-term research, the inventor finds that titanium element and vanadium element with stronger bonding force with carbon atoms are added while carbon atoms in 316L alloy are increased, titanium carbonitride and vanadium carbonitride can be formed, so that the influence of the increase of the carbon elements on the corrosion resistance of the alloy can be reduced while the strength of the alloy is improved.

In the following examples, the novel 316L alloy with high strength and corrosion resistance is prepared by a method known in the prior art of vacuum smelting and electroslag remelting, and belongs to a conventional method in the technical field. The innovation point of the invention is to optimize the chemical composition of the alloy, not the preparation method, and therefore the preparation method is not described in detail.

In the context of the present invention, the numerical values of the chemical composition are mass percent contents.

Examples 1 to 5

316L alloy is prepared by the conventional vacuum smelting and electroslag remelting method according to the chemical composition listed in Table 2. The carbon content in example 1 was compared with the standard chemical composition of the 316L alloy.

TABLE 2 chemical composition (w/w%)

Fig. 1 to 5 are metallographic photographs of the alloys obtained in examples 1 to 5, respectively, and it can be seen from the metallographic photographs that the size of the alloy crystal grains gradually decreases with the increase of the carbon element content, and the effect of refining the crystal grains is more remarkable.

Carrying out heat treatment on the alloy materials obtained in the embodiments 1-5, wherein the heat treatment mode is 1050 ℃ multiplied by 30min, and carrying out water cooling after solid solution; the tensile strength, yield strength and elongation after fracture of the material were then tested, respectively, and the results are shown in table 3 below:

TABLE 3 mechanical Property test results

Examples	Tensile strength	Yield strength	Elongation after fracture
				1	498MPa	342MPa	35.5％
2	552MPa	402MPa	36.0％
				3	583MPa	421MPa	38.0％
4	601MPa	443MPa	33.5％
				5	589MPa	418MPa	26.5％

From the results in table 3, it can be seen that, as the carbon content gradually increases, the alloy strength is significantly different, the mechanical properties of the alloy are greatly improved, and the ductility and toughness of the alloy are reduced to some extent, but the reduction is small, and the comprehensive properties of the alloys of examples 2 to 4 are slightly better than or equal to those of the alloy of example 1 except for example 5.

The alloys of examples 1, 2, 4 and 5 were tested for corrosion resistance by electrochemical workstation in 3.5% NaCl solution at 30 deg.C, and the polarization curves are shown in FIG. 6.

The inflection point of the alloy current, where there is no significant change in the polarization curve but the voltage increases rapidly and the current changes with the voltage, is called pitting potential. The high and low pitting potentials of the alloy indicate that the alloy has weak pitting corrosion resistance, the higher the pitting potential is, the more corrosion resistance the alloy is under the condition is, and the pitting potentials of the four alloy components are shown in Table 4.

TABLE 4 results of corrosion Performance test

Examples	Potential for pitting
		1	1068mV
2	1058mV
		4	983mV
5	830mV

As is clear from the results shown in FIG. 6 and Table 4, the corrosion resistance of each alloy was reduced with the gradual increase of the carbon content, but when the C content was not more than 0.040%, the reduction of the corrosion resistance of the alloy was small, and the alloys (examples 2 and 4) still had good corrosion resistance. When the C content reached 0.045%, the corrosion resistance of the alloy (example 5) was significantly reduced.

Claims

1. The novel 316L alloy with high strength and corrosion resistance is characterized in that the chemical composition of the alloy is that on the basis of the standard chemical composition of the 316L alloy, the content of carbon atoms is increased to 0.035-0.040%, and vanadium and titanium are added.

2. The high strength corrosion resistant novel 316L alloy according to claim 1, wherein the content of vanadium element is 0.05 ± 0.01%.

3. The new 316L alloy, high strength and corrosion resistance, according to claim 1, wherein said ti is present in an amount of 0.05 ± 0.01%.