SE442024B - STOLEN - Google Patents

Description

8 | Out, 5E; 5J1 "0 2 the constructions for example houses or tanks for nuclear reactors and which by weight contains: 0.13 ~ 0.18 1 col 0.17-0.37% silicon 0.3-0.6% manganese 1.7-2, ü 1 chrome 1-1.5% nickel 0.5-0.7 Z molybdenum 0.05-0.12 Z vanadium o, o1-o, o35% aluminum 0.005-0.12% nitrogen 0.11 ~ 0.2 1 copper 0.0035-0.0055% arsenic, while iron makes up the rest.

The steel can also contain a maximum of 0.02 in the form of impurities weight percent phosphorus and not more than 0.02 weight percent sulfur.

This steel exhibits the properties that meet the requirements that in the production of welded houses for nuclear reactors an output of up to 1 million kw. This famous steel exhibits however, an insufficiently high strength to be able to produce set up houses for nuclear reactors with an output exceeding 1 million kW with cross-sectional dimensions of at least 500 mm. This disadvantage can eliminated by increasing the content of alloying elements in and for to increase the steel's so-called bainite heat resistance, which, however, significantly increases the tendency of the steel to become brittle during thermal feelings, ie. in case of delayed cooling after tempering at high temperature temperature and during long holding times for the steel at high temperatures.

The main object of the present invention is to provide such a steel, which exhibits complete bainite heat resistance and high strength and extensibility properties at transverse average dimensions of 500-700 mm for parts with large dimensions of welded housings of nuclear reactors with an output of up to 2 mil- ions kw, which steel retains its resistance to becoming brittle under thermal effects.

This is achieved according to the invention by means of a steel containing carbon, silicon, manganese, chromium, nickel, molybdenum, vanadium, nitrogen, aluminum copper, arsenic, phosphorus, iron, whereby the steel, according to the invention further contains antimony and tin, while all 8005551-0 constituents are present in the steel in the following percentages by weight: 0.13-0.18% col 0.17-0.37 5 silicon 0.3-0.6 l of manganese 1.7-2.5 X chromium 2.1-2.5 Z nickel 0.5-0.7 1 molybdenum 0.05-0.12% vanadium 0.005-0.012% nitrogen 0.01-0.035% aluminum 0.11-0.2 Z copper 0.003-0.008% arsenic 0.003-0.012% phosphorus 0.001-0.005% antimony 0.001-0.0U% tin, while iron constitutes the remainder, whereby the the content of antimony, tin and phosphorus is determined by the the band. V Sn + 2 Sb + BP <0.039% by weight.

All elements and their specified levels contribute to the gets the desired properties. The choice of the upper limit of 0.18% by weight for the carbon content is due to a continued increase of the carbon content of the steel impairs the technical properties of the steel, b1.a. weldability and promotes cold and hot cracking. If coal content is higher than 0.18% by weight, the toughness properties of the steel per deteriorates and its critical brittleness temperature increases.

If the carbon content is lower than 0.13% by weight, the steel will not predetermined strength properties, especially when the article has considerable cross-sectional area, due to the fact that carbon is an element, which increases the strength of the solid solution and contributes to the carbide phase formation.

If the silicon content is lower than 0.17% by weight, the steel is deoxidized not acceptable, whereby a ingot with a leaky structure is obtained. Then the silicon content is higher than 0.37% by weight, the toughness of the steel is reduced at the same time as the steel becomes more likely to become brittle during tempering.

If the manganese content is lower than 0.3% by weight, the steel is deoxidized not fully, at the same time as it has a high sulfur content, because manganese promotes purification of the molten steel by joining it 8005551-0 with sulfur. Manganese sulphide formation helps to reduce steel tendency to hot crack formation during welding. About the manganese content is higher than 0.6% by weight and the chromium content is 1.7-2.5% by weight, the steel becomes brittle, and the steel has low extensibility and becomes prone to embrittlement during tempering.

If the chromium content is lower than '7% by weight, the steel must not so-called consistent bainite heat resistance at thicknesses of 500-700 mm. When chromium content exceeds 2.5% by weight, the technology of the technical properties (machinability) while the toughness of the steel can reduced by the formation of so-called special carbides.

The minimum nickel content of 2.1% by weight contributes to the steel getting consistent heat resistance at large cross-sectional areas and the desired ones the strength and toughness properties. If the nickel content is higher than 2.5% by weight, the steel can have so-called reversible tempering brittle heat, which impairs the weldability of the steel.

The lower limit of 0.05% by weight for the vanadium content in the steel contributes to the steel being deoxidized and degassed acceptably as well gets nice primary and secondary structure, and the steel becomes more resistant to a decrease in the strength of the steel during tempering. Va- Nadine carbide formation helps to reduce the tendency of steel to grain growth at high temperatures. Then the vanadium content is higher than 0.12% by weight, increases the probability of cracking when pad heating after welding.

If the molybdenum content is less than 0.5% by weight, the steel may be versatile tarnish embrittlement at the same time as it can be less constantly against the steel's strength decreasing during tempering. If molybdenum content exceeds 0.7% by weight, the strength of the steel heat properties and weldability. IN If the nitrogen content is lower than 0.005% by weight, the steel gets fine-grained structure because nitrogen by bonding to aluminum forms aluminum minium nitrides, which prevent the grains from growing. When nitrogen content is higher than 0.012% by weight, the steel and on articles of welds made from this steel may be prone to aging due to the formation and thermal impact: If the aluminum content is less than 0.01% by weight, it is deoxidized 8005551-0 the steel not fully. Neither is nitrogen bound in this case aluminum nitrides completely. When the aluminum content is higher than 0.035% by weight, the steel can be contaminated by aluminas, which adversely affects the toughness and extensibility of the steel. IN The lower limits for copper, arsenic and phosphorus content are of the process technical possibilities in steel production, the upper limits for the levels of copper, arsenic and phosphorus is consistent with the fact that the steel must have a sufficiently high toughness.

As pointed out above, the steel of the invention has a higher nickel content. content (2.1-2.5% by weight) compared to the known steel thereof blows with a nickel content of 1-1.5% by weight. The high nickel content contributes to increasing the heat resistance and strength properties of the steel per at thicknesses of 500-700 mm and to increase its impact resistance and reduce the steel's tendency to brittle fracture. That according to the present invention proposed steel contains an additional 0.001-0.005 weight percent antimony and 0.001-0.00ü weight percent tin, wherein it The total content of antimony, tin and phosphorus is determined by the relationship Sn + 2 Sb + BP ¿0.039% by weight, which - apart from the presence of said amount of nickel, which increases the heat resistance of the steel but adversely affects the resistance of steel to brittleness by thermal impact - makes it possible to maintain the steel high resistance to brittleness during tempering and prolonged chemical effects during operation by reducing it by seg- ring of s.k. gorophilic elements caused the degree of attenuation in the bonding force between individual grains. About the content of antimony, tin and phosphorus become higher than the upper ones, through said relationship limits, the grain boundaries of the steel can be significantly weakened by equilibrium sagging under thermal impact, which can increase the steel prone to embrittlement. The factors, which stand at Sn, Sb and P in the context above, reflects the degree of impact of these basic substances on the brittleness of steel.

The process for producing the steel is, technologically, easy to implement and implemented in the following ways.

The steel is produced in alkaline and acidic martin furnaces or in alkaline arc furnaces.

Phosphorus, antimony and tin-free were used as the mission material soosss1-o 6 scrap steel, special cast iron, ferroalloys (for example ferrous chromium, ferrovanadine, ferromolybdenum, ferro-silicon) and pure metals (manganese, nickel and aluminum). The process technology for steel effect in martin ovens includes the following process steps: 'g - steel scrap, cast iron, lime and iron ore are introduced into a base oven and causes its mission material to melt, - additional iron ore and lime to be introduced into the melt are introduced cooking, - the melting, defecoration and melting of the molten metal are carried out avsvavlíng, formed slag is renewed, the molten metal is drained into an acidic martin furnace, - the boiling and heating of the molten metal are continued, which is then alloyed, the steel thus produced is deoxidized.

The process technology for steelmaking in arc furnaces includes the following steps: scrap steel and electrode waste are loaded into an oven and brought to melt, - the melt is added with lime, fluorspar and iron ore, after which you performs the boiling and dephosphorization of the molten metal, ¿ the molten metal is heated, oxidation slag is renewed (the old slag is removed and manufactures the new one from lime and fluorspar) and introduces some the fermentation elements (Ni, Mo), deoxidize the steel and slag using ferro-silicon and ferro-silicon manganese x - the steel is alloyed and then finally deoxidized by aluminum I nium.

The invention is further elucidated below in the following exemplary embodiment.

Example 1 A steel is produced, which in percentage by weight contains: 0.13 1 col 0.17 Z silicon 0.3 Z manganese 1.7 1 chrome 2.1 1 nickel 0.5 Z molybdenum 7 8005551-0 0.05 Z vanadium 0.005 2 nitrogen 0.01 5 aluminum 0.11% copper 0.003 1 arsenic 0.012% phosphorus 0.001% antimony 0.001% tin, while iron makes up the rest.

The steel is produced in a basic arc furnace. Starting materials res of armco steel, electrode waste and ferroalloys with low content of pollutants.

The mission material, ie. armco steel and electrode waste are invested in an oven, is melted and heated to a temperature of 155000. After melting is complete, iron ore and lime are added.

The oxidizing slag formed is carefully mixed with the melt the steel. The slag is then removed from the oven at a temperature of 1550-156000 and re-feeds iron ore, lime, nickel and the ferro molybdenum in the furnace vessel, after which the steel is cooked until the carbon content is equal to 0.13% by weight. Oxidation type The gene is then removed from the oven and lime, fluorspar, are added, aluminum, ferro-silicon, ferromanganese, ferrochrome and ferrovanadine.

The molten steel is then heated to a temperature of 1630 ° C. 166000 and drained from the oven. The steel is cast in such a way that handles large ingots with a ratio between the height of the ingot and its diameter equal to 1.03: 1.

Examples 2-6 Table 1 shows the compositions of the steel produced by a procedure similar to that described in Example 1.

Table 2 lists the mechanical properties of the present invention. the present invention proposed the steel (Examples 1-6) and the known the steel with a nickel content of 1-1.5% by weight after the optimum the heat treatment.

Table 2 shows that the steel according to the invention has higher strength, extensibility and toughness than the known steel with a nickel 1-1.5% by weight and also has a lower critical embrittlement temperature, whereby its resistance to becoming Qm fifi t v 0005551-0 8 with delayed cooling and during long holding times for the steel at high temperatures are not lower than that of the known steel, which consistency is measured by an increase in the critical embrittlement the temperatures.

Table 1 Chemical composition of the steel according to the invention, in weight percent Example C Mn Si Cr Ni Mo V N 1 0.13 0.30 0.17 1.7 2.1 0.5 0.05 0.005 2 0.15 0.05 0.27 2.1 2.3 0.6 0.09 0.009 3 0.18 0.60 0.37 2.5 2.5 0.7 0.12 0.012 - 0 0.16 0.38 0.29 1.75 2.2 0.66 0.07 0.006 5 0.18 0.51 0.19 1.91 2.12 0.52 0.10 0.006 6 0.15 0.58 0.20- 2.0 2.0 0.50 0.05 0.010 Example Al Cu As P Sb Sn Sn + 2Sb + 3P 1 0.01 0.11 0.003 0.012 0.001 0.001 0.039 2 0.022 0.16 0.005 0.010 0.002 0.000 0.038 3 0.035 0.20 0.008 0.009 0.005 0.002 0.039 0 0.03 0.12 0.007 0.008 0.000 0.000 0.036 5 0.013 0.10 0.008 0.011 0.002 0.002 0.039 6 0.018 0.13 0.000 0.007 0.007 0.002 0.029 0.029 9 8005551-0 Table 2 Mechanical properties of steel Smidestyckets Vårmebehand- Prov- Memn fi ska qgmsmqær cross-sectional ratio Steel dimension countries tempera- --9¿à-ïï-lL- - mm tur ° C kp / mm 1 2 3 11 5 6 According to the Austenitise the invention 650 ring at 56 66 900 C cooling 20 Example 1 zooocvh 3: EE tempering at §§ 6s0 ° c 550 Fä 57 Austenitise- 6 call at 59 _2 2 650 9oogc; ky1ning 20 66 70 âgâögágng at 550 go go 650 ° C Austenitise- 6 rin at 5 71 5 650 9oošc; ky1ning 20 E? ïš 2 ° C / h Su 65 tempering at 350 650OC -5-6 E? M 600 iïšše fi ääise- 20 gå 2% 900 DEG C. cooling 2 ° C H9 57 tempering at 350 - - Austenitise- _. 61 70 rin at 20 - 5 650 šggšcskylning Eï 73 C 6 tempering at 350 and 5 65 ° C 52 56 Austenitise- . . 60 72 rin at 20 -E 6 709 900šC, cooling so 7 15o ° c / n us 58 tempering at 350 ÉÜ 65 650 ° C 8005551-0 10 1 2 3 '4 5 6 The Ausšenitization we 20 fl to 57 known 650 900 C; cooling 150 C / h; 55 Éï steel tempering at 650 ° C 350 äš §Q - 55 Note: For the steel according to the invention, the numerator and clean the lowest resp. highest properties, determined by guidance of the test results for different test bodies of the steel with given composition. For the known steel, the numerator and denominator indicate the lowest resp. maximum characteristics determined by test results for test specimens with limits of constituents within the area of resp. levels in the steel of the highest quality.

Tk is determined on the basis of 50% of the viscous component in the fracture tet. ' 8005551-0 11 n? Y 'Û-V: ï-ågånâm ä fi relšnšrp water _m <_ad water with eftçr- k _m running in running followedJaxïxde following posture 1 -E-a water o ° hole v1d v1d 1 | 00 ° C during a cm 2 10 / h 350 C for a time of 10000 h time of 1000 h 7 8 9 10 11 12 13 _29 79 å9: 59 íâ 9 19 22 ïï 23 -39 19 0 15 1_6. 19 19 17 73 20 12 99 19 11.2. _19 9 12 21 70 20 -35 22 0 18 lay 55 lä 17 37 19 1§ 6M 16 -52 gg Q 15 19 67 ï8 ïïï 25 0 20 15 59 13 is 61 20 12 lå 19 '”° lå 9 19 21 75 22 ïíí 25 0 20 lä 99 lå 17 70 19 19 97. _19 _55 ä 9 ä 20 71 20 IE5 30 15 25 15 and 15 18 EB 17 17 go 11 -35 15 0 15 50 70 20 ïïö ÉÜ ïñ 20 16 6H 15 15 EE 18 1_6. 60 _19 '_12 29 _9 J. 19 EB 15 0 50 10 22 ~ _9 15 59 13

Claims (1)

8005551-0 12 Claims Steel consisting of carbon, silicon, manaane, chromium, nickel, molybdenum, vanadium, nitrogen, aluminum, copper, arsenic, phosphorus and iron, kneaded in that it further contains antimony ocn_tenn, all parts of which are included in the following __ contents in weight percent: "i" o, 13lo, 18 1 carbon 0,17-0,37 S silicon _ 0,3-0,6 1 manganese j _.-1,7-2 , 5 $ .chrom 2,1 ~ 2,5 i nickel --0,5-0,7 à molybaen »-j 0,05-0,12 $ vanadin o, oo5-o, o12 1 nitrogen" f- = 0.01-0.035 5 aluminum _1 '6.11-0.2 5 copper 0.00} f0.008'1'arSeník „" Å o, oo3-o, o12 I phosphorus 0.001-0.005 Z antimony 0.001-0, 00Ä 1 tin 'the rest iron, whereby the total content of antimony, tin in and.fosTor is given by the relation sn + 2 sn "+ §¿r (-0.039 viknpèoeenp.