SU1266894A1 - Steel - Google Patents

Abstract

The invention relates to steels,: used for the manufacture of pipes and welded installations for processing gases and reactors operating under conditions of contact with hydrogen sulfide-containing media. The purpose of the invention is to improve the processing properties, corrosion resistance, plasticity and toughness. Steel contains, wt%: C 0.15-0.25; Si 0.150, 50; Mp 0.3-0.8; A1 0.02-0.06; Ca 0.0005-0.012; Ti 0.005-0.05; N 0, OO50, 018; Cu 0.05-0.27; Fe rest. Properties of steel: G 485-500 MPa; G; 345-350 MPa; 5-32.5%; 3, 0-22, 1 kgM / cm; the amount of absorbed hydrogen 3.3 7, 1 cm / 100 g; relative area affected by blistering, 1820%; time to failure under load (LKUI 256 MPa 140–320 h; growth rate of sub-cracks 0.2–3.0 mm / s; mass loss 0.1–0.9 mm / year. The microstructure of the welded joint is dense, the amount of rolled metal 3-5 pieces of defects on 1 2 tables tC O) O5 CX) with "4;

Description

126 The invention relates to metal, in particular, to low-alloyed steels used for the manufacture of pipes and welded gas processing plants and reactors operating under conditions of contact with hydrogen sulphide-containing gas and oil condensate when the material is exposed to intense corrosive effects and exposure. The aim of the invention is to improve process plasticity, plasticity, impact toughness and corrosion resistance in hydrogen-sulphate containing materials. Steel is implanted in induction "Techi". The metal was rolled in a hot state, cut blanks of thick Si I Mn I A1 I Ca 1 Ti were cut.

WITH

0,150,500,800,030,00900,035

0,200,370,300,040,00180,027

0,250,150,550,020,01200,005

0,270,520,280,070,00040,004

0,140,140,830,0190,01250,055

0,310,171,00,030,0080,029

Component content, wt.% 6894j with a thickness of 12 mm, which were then subjected to normalization at a temperature. When conducting tests under the technological plasticity of steel, we understood the manufacturability of steel during casting, hot deformation and welding. The standard mechanical properties, the amount of hydrogen absorbed, the rate of general corrosion, the impact strength, the blistering rate, the subcritical rate of crack growth, and the time until the destruction of the hydrogen sulfide-containing medium 15 were determined. Weldability was evaluated by the macrostructure of the welded joint. In tab. 1 shows the composition of the steel; in tab. 2 - their properties. Table 1 The assessment of metal resistance in hydrogen sulfide-containing media was carried out in a test in the high-grade solution of hydrogen sulfide according to the international method NACE TM-01-77. The time to failure was determined by the duration of the test | 1 specimens under a load of 256 MPa. The subcritical crack growth rate was determined by the increase in its length on a sample with a previously applied crack, which is under load in the above solution. The relative area affected by blistering was determined using ultrasound control methods of samples aged in the indicated solution for 96 hours. The amount of absorbed hydrogen was determined by the difference between the hydrogen content in the samples before and after the tests using the method of reductive melting using a gas analyzer Leko. Loss in weight was evaluated by the difference in sample mass before and after testing. In the proposed steel, iron is the base, carbon, silicon, manganese, copper — the main alloying elements, calcium, nitrogen, aluminum, and titanium — the main micro-alloying elements and modifiers. Nitrogen, forming nitride and carbonitride inclusions with the constituent elements, provides for the refinement of the initial austenitic zone. Aluminum in combination with nitrogen and other elements — deoxidizing agents and nitride-forming elements — regulates the phase composition and morphology of non-metallic inclusions, as well as the distribution of nitrogen between the solid solution and nitrides. The elements of the proposed steel form its structure in the processes of crystallization, subsequent cooling of the ingot, hot rolling and heat treatment and, being in a complex interconnection, provide a complex of its high properties. When the carbon content is less than 0.15%, the steel does not have sufficient strength, while if the carbon content is more than 0.25%, the fracture toughness decreases, the growth of subcritical cracks is accelerated, the durability in hydrogen rich environments decreases. Silicon increases the strength of the solid-hardening mechanism and increases the corrosion resistance. When the silicon content is less than 0.15%, the steel does not have sufficient x; strength, and the corrosion films formed on the surface do not have protective properties; - at concentrations greater than 0.50%, brittleness appears and deterioration of resistance in hydrogen sulfide-containing environments occurs, which is not compensated by increasing protection. properties of the film due to the fragility of the matrix. Manganese increases the strength of steel and, due to the binding of sulfur, protects it from red brittleness. Within specified limits, it increases viscosity at low temperatures. When the content of manganese is less than 0.30%, the required level of strength properties is not achieved, when the content is more than 0.80%, the weldability deteriorates, segregation heterogeneity develops, and strechech- are formed. or streaky structures. The formation of streaky structures in combination with the known inclination of phosphorus to segregation leads to an increase in the tendency to blister and step cracking. In the steel of the proposed composition, the lower limit of the copper content of 0.05% is dictated by the requirements of the continuity of the protective film, the upper limit of 0.27% is limited by the deterioration of hot plasticity, embrittlement and decrease in durability in hydrogen rich environments. At higher copper contents, intense growth of subcritical cracks is also observed. Calcium-doped, in quantities less than 0.0005%, is not enough to prevent the formation of plastic sulphides of simple composition and does not provide the required plastic and viscosity properties, processability, or decrease in blistering sensitivity. At concentrations higher than 0.012%, deterioration is observed, which is manifested in low plasticity of the metal, formation of large inclusions and nucleation in corrosive pitting and corrosion corrosion, decrease in viscosity and durability during hydrogen accumulation.

accelerated development of blistering, deterioration of weldability.

A titanium content of less than 0.005% is not enough to achieve the required level of strength, ductility and durability in hydrogen rich environments. When the titanium content is more than 0.05%, large nitrides and sulfides are formed, plastic and viscous properties deteriorate, the tendency to brittle fracture at negative temperatures increases, and the tendency to blistering appears, the workability during rolling and welding deteriorates.

An aluminum content of less than 0.01% is not enough to simultaneously bind nitrogen and oxygen and form the amount of nitrides required to grind grain; its content of more than 0.06% impairs the properties as a result of the formation of large oxygen and nitride inclusions and spindles, sharply reducing the ductility and toughness of steel and being the centers of development of blistering.

A nitrogen content of less than 0.05% is not enough to achieve the required strength properties, and more than 0.018% is impractical because of the deterioration of processability during melting, casting and hot rolling, deterioration of weldability and corrosion resistance.

the occurrence of a tendency to blistering, pitting, and corrosion of corrosion, reducing durability in the water. your environments ..

The data presented in Table 2 show that, compared with the known, steel has a higher complex of technological, corrosion and mechanical properties, which will reduce the cost of products manufactured from it and increase their reliability and durability.

Claims (1)

Invention Formula Steel containing carbon, silicon, manganese, aluminum, titanium, calcium, nitrogen, copper and iron, is so tl that, in order to improve its technological plasticity, increase plastic properties, impact strength and corrosion resistance in hydrogen sulfide containing ere-, dah, it contains components in the following ratio, .may.%: 0.15-0.25 0.15-0.50 0.30-0.80 0.02-0.06 0,0005-0,012 0.005-0.05 0,005-0,018 0.05-0.27 Rest