RU2338797C2 - Tube stock out of ball bearing steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to production of tube stock of 80-180 mm diameter. To facilitate upgraded level of consumer characteristics it is produced out of steel containing wt %: C 0.95-1.05, Mn 0.20-0.40, Si 0.17-0.37, Ni 0.005-0.30, Al 0.005-0.05, V 0.005-0.03, S 0.005-0.020, P 0.005-0.027, Cr 1.30-1.65, N 0.005-0.012, As 0.0001-0.03, Sn 0.0001-0.02, Pb 0.0001-0.01, Zn 0.0001-0.005. iron and unavoidable impurities - the rest at the ratio of: (As+Sn+Pb+5×Zn)≤0.07; 0.30≤(Mn/6+Cr/5)≤0.38, at that it has grain pearlite structure and dimension of actual grain 6-9 points, macrostructure - central porosity, pointed non-uniformity, and sub-shrinking liquation not more, than 2 points in each kind, liquation square and liquation strips not more, than 0.5 point, non-metallic inclusions: pointed sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non-deformed silicates not more than 2.0 points in each kind of inclusions, tensile strength not less, than 590 N/mm², yield point not less, than 390 N/mm², specific elongation not less, than 21%, contraction ratio not less, than 45%, impact resilience KCU not less, than 440 kJ/m², hardness 179-217 HB.

EFFECT: facilitating upgraded level of consumer characteristics.

4 cl, 2 ex

Description

The invention relates to the field of metallurgy, in particular to the production of a tube billet with a diameter of 80 to 180 mm from ball-bearing steel of an increased level of consumer properties and a reduced tendency to various types of brittle fracture.

The closest analogue to the claimed invention is a known tubular billet of ball-bearing steel, hot rolled, annealed, having predetermined parameters of structure, macrostructure, non-metallic inclusions and mechanical properties. (Directory, Modern materials in the automotive industry, Moscow, "Engineering", 1977, p.125-128).

The most important requirement for a billet made of ball-bearing steel is, on the one hand, to ensure uniformity of micro and macrostructure, low content of non-metallic inclusions, and, on the other hand, to provide an increased range of consumer properties.

The objective of the invention is to provide a high level of consumer properties, while ensuring a favorable ratio of strength, ductility and viscosity, a minimum level of anisotropy of mechanical properties, low content of non-metallic inclusions, homogeneous macro and microstructure of rolled products, as well as increased resistance to temper brittleness.

The problem is solved in that the known tubular billet from ball-bearing steel, hot rolled, annealed with a granular perlite structure, having predetermined parameters of non-metallic inclusions, structure, mechanical properties, according to the invention is made of steel containing the following ratio of components in wt.%:

carbon 0.95-1.05 manganese 0.20-0.40 silicon 0.17-0.37 nickel 0.005-0.30 aluminum 0.005-0.05 vanadium 0.005-0.03 sulfur 0.005-0.020 phosphorus 0.005-0.027 chromium 1.30-1.65 nitrogen 0.005-0.012 arsenic 0.0001-0.03 tin 0.0001-0.02 lead 0.0001-0.01 zinc 0.0001-0.005 iron and inevitable impurities rest

when the relations are satisfied: (As + Sn + Pb + 5 × Zn) ≤0.07; 0.30≤ (Mn / 6 + Cr / 5) ≤0.38, the workpiece has a real perlite grain size of 6-9 points, macrostructure: central porosity, point heterogeneity, shrink segregation no more than 2 points for each type, segregation square, segregation strips - not more than 0.5 points, non-metallic inclusions: point sulfides, point oxides, line oxides, brittle silicates, plastic silicates, undeformed silicates - not more than 2.0 points for each type of inclusion. Mechanical properties after annealing: tensile strength of at least 590 N / mm ² yield strength of not less than 390 N / mm ^2, an elongation of at least 21%, contraction ratio is not less than 45%, the toughness KCU not less than 440 kJ / m ^2, hardness 179-217 HB.

As additional impurities, steel contains in wt%: copper - not more than 0.25, molybdenum not more than 0.03, oxygen not more than 0.0015, titanium not more than 0.005.

If nickel content 0,005-0,10%, 0,005-0,010 sulfur, phosphorus 0.005-0.015% workpiece has mechanical properties after annealing: tensile strength of at least 590 N / mm ^2, yield stress of not less than 390 N / mm ^2, elongation not less than 24%, relative narrowing not less than 48%, impact strength KCU not less than 550 kJ / m ² , hardness 179-217 HB.

When the nickel content is 0.10-0.30%, sulfur 0.010-0.020, phosphorus 0.015-0.027%, the workpiece has mechanical properties after annealing: temporary tensile strength - not less than 610 N / mm ² , yield strength not less than 410 N / mm ² , elongation of at least 21%, relative contraction of at least 45%, impact strength KCU of at least 440 kJ / m ² , hardness 179-217 HB.

The given combinations of alloying elements (item 1) make it possible to obtain a ferrite-pearlite finely dispersed structure in a finished product with a favorable combination of strength and ductility characteristics, increased hardenability, and increased resistance to various types of brittle fracture.

Carbon is introduced into the composition of this steel in order to ensure a given level of its strength and hardenability. The upper limit of the carbon content (1.05%) is due to the need to ensure the required level of ductility of steel, and the lower - respectively 0.95% - to ensure the required level of strength and hardenability of this steel.

Vanadium is introduced into the composition of this steel in order to provide a finely dispersed, uniform grain structure. In this case, vanadium controls the processes in the lower part of the austenitic region, (determines the tendency to growth of austenite grain, stabilizes the structure during thermomechanical processing, increases the recrystallization temperature and, as a result, affects the nature of the γ-α transformation. The upper limit of the vanadium content is 0.03 % is due to the need to ensure the required level of ductility of steel, and the lower - respectively 0.005% - to ensure the required level of strength of this steel.

Manganese and chromium are used on the one hand as solid solution hardeners, on the other hand, as elements that increase the stability of supercooled austenite of steel. At the same time, the upper level of manganese — 0.40% and chromium — 1.65% is determined by the need to ensure the required level of ductility of steel, and the lower, manganese — 0.20% and chromium — 1.30%, respectively, by the need to provide the required level of strength and hardenability of this steel.

Silicon refers to ferrite-forming elements. The lower limit for silicon - 0.17% due to the technology of deoxidation of steel. A silicon content above 0.37% will adversely affect the ductility characteristics of steel.

Nickel within the specified limits affects the characteristics of hardenability and toughness of steel. In this case, the lower level of nickel content - 0.005%, is determined by the need to ensure a given level of steel viscosity, and the upper level - 0.30% by the need to obtain a martensitic structure during steel quenching (since nickel is an austenitizer).

Aluminum is a strong nitride former and steel deoxidizer. The upper limit of the aluminum content of 0.05% is due to the need to obtain a given level of ductility and toughness of steel, and the lower 0.005 due to issues of manufacturability.

Sulfur determines the level of ductility and machinability by cutting steel. The upper limit (0.020%) is due to the need to obtain a given level of ductility and toughness of steel, and the lower limit (0.005%) is due to issues of manufacturability and machinability.

Phosphorus determines the level of ductility of steel and its tendency to reversible temper brittleness. The upper limit (0.027%) is due to the need to obtain a given level of ductility and toughness of steel, and the lower limit (0.005%) is due to issues of manufacturability.

Nitrogen promotes the formation of nitrides in steel. The upper limit of nitrogen content - 0.012% is due to the need to obtain a given level of ductility and toughness of steel, and the lower limit - 0.005% by issues of manufacturability.

Arsenic, tin, lead and zinc are colored impurities that determine the overall level of ductility of steel and its tendency to manifest reversible temper brittleness during subsequent heat treatment of finished products from the pipe billet under consideration. The lower limit for arsenic, tin, lead and zinc (0.0001% for each element, respectively) is determined by the technology of steel production, and the upper limit (0.03%, 0.02%, 0.01% and 0.005%, respectively) determines the increased the tendency of steel to reversible temper brittleness.

The ratio As + Sn + Pb + 5 × Zn≤0.07 determines the reduced tendency of steel to manifest reversible temper brittleness.

The ratio of 0.30≤Mn / 6 + Cr / 5≤0.38 determines the level of hardenability of steel.

Comparative analysis with the prototype allows us to conclude that the claimed composition is different from the known introduction of new components and ratios:

As + Sn + Pb + 5 × Zn≤0.07; 0.30≤Mn / 6 + Cr / 5≤0.38.

Thus, the claimed technical solution meets the criterion of "novelty."

The analysis of patent and scientific and technical information did not reveal solutions having a similar set of features that would achieve a similar effect - increasing the level of consumer properties, while ensuring a favorable ratio of strength, ductility and viscosity, a minimum level of anisotropy of mechanical properties, a reduced tendency to reversible temper brittleness, low content of non-metallic inclusions, homogeneous macro and microstructure of rolled products.

Therefore, the claimed combination of features meets the criterion of "significant differences".

The following are examples of the implementation of the invention, not excluding others in the scope of the claims. Smelting of three compositions of the investigated steel (chemical composition in wt.%:

Example 1: carbon - 0.99%, manganese - 0.29%, silicon - 0.21%, nickel - 0.09%, aluminum - 0.014%, vanadium - 0.009%, sulfur - 0.009%, phosphorus - 0.016% , chromium - 1.45%, nitrogen - 0.007%, arsenic - 0.010%, tin - 0.008%, lead - 0.006%, zinc - 0.001%

Example 2: carbon - 0.96%, manganese - 0.27%, silicon - 0.28%, nickel - 0.21%, aluminum - 0.016%, vanadium - 0.012%, sulfur - 0.015%, phosphorus - 0.022% , chromium - 1.49%, nitrogen - 0.008%, arsenic - 0.011%, tin - 0.004%, lead - 0.005%, zinc - 0.002% is produced in 150-ton steel arc furnaces using 100% metallized pellets in the charge, which provides a mass fraction of nitrogen before the release from particleboard of not more than 0.003%, as well as a low content of color impurities. The preliminary alloying of the metal with manganese and silicon is carried out in the ladle upon discharge from the particleboard. After the release, the metal was purged with argon through the bottom purge unit, during which the steel was deoxidized by aluminum. After that, the metal enters the integrated steel processing unit (AKOS), where it is possible to heat the metal to the required temperature, purge it with argon through the bottom blowing unit, dosed the necessary ferroalloys and treat the steel with flux-cored wire with various fillers. At AKOS, refining slag is imposed with an additive of lime and fluorspar, slag is deoxidized with granulated aluminum, the metal is alloyed with aluminum to a content of 0.050%, the metal is refined according to the manganese content, and it is heated to a temperature that ensures further processing. After processing at AKOS, the metal is subjected to vacuum treatment at a batch vacuum. During evacuation, a final adjustment of the chemical composition is made. After evacuation, the metal is treated with silico-calcium and transferred to casting. The casting is carried out on radial four-strand UNRS in an ingot 300 × 360 mm in size with a drawing speed of 0.6 ÷ 0.7 m / min, with metal protection from oxidation by using cover slag mixtures in the intermediate ladle and mold, protective tubes, immersion glasses and argon feed. It also provides a low nitrogen and oxygen content and metal purity from non-metallic inclusions. After casting and cutting to a measured length, the continuously cast billets obtained were cooled in controlled cooling furnaces. Hot rolling of long products starts at a temperature of 900-950 ° C and ends at a temperature of 740-850 ° C, with a deformation in the last passes of at least 20%. After the completion of rolling, the billets are annealed and as a result a tube billet ⌀ 140 mm, length - 7200 mm,

For example 1: the structure of granular perlite, the actual grain score 7. Macrostructure: central porosity 2 points, point heterogeneity 1 point, segregation square 1 point, shrink segregation 2 points, segregation strips 1 point. Non-metallic inclusions: point sulfides 1.0 points, point oxides 0.5 points, line oxides 1.0 points, brittle silicates 0.5 points, plastic silicates 0.5 points, non-deformed silicates 1.0 points. Mechanical properties after annealing: tensile strength 615 N / mm ^2, yield stress of 420 N / mm ^2, elongation of 25%, contraction ratio 49%, the toughness KCU 576 kJ / m ^2, hardness 187 HB. As + Sn + Pb + 5 × Zn = 0.029; Mn / 6 + Cr / 5 = 0.338.

In Example 2: granular perlite structure, real grain score 7. Macrostructure: central porosity 1.5 points, point heterogeneity 1.5 points, segregation square 1 point, shrink segregation 1.5 points, segregation strips 0.5 points. Non-metallic inclusions: point sulfides 1.5 points, point oxides 0.5 points, line oxides 0.5 points, brittle silicates 1.0 points, plastic silicates 0.5 points, undeformed silicates 1.0 points. Mechanical properties after annealing: temporary tensile strength 617 N / mm ² , yield strength 401 N / mm ² , elongation 21%, relative narrowing 46%, impact strength KCU 455 kJ / m ² , hardness 209 HB.

As + Sn + Pb + 5 × Zn = 0.034; Mn / 6 + Cr / 5 = 0.343

The introduction of ball-bearing steel tubular billets into production provides an increase in the level of consumer properties, with a favorable ratio of strength, ductility and toughness, a reduced tendency to reversible temper brittleness, and increased hardenability.

Claims (4)

1. A hot-rolled tubular billet made of ball-bearing steel annealed with a granular perlite structure, having predetermined parameters of non-metallic inclusions, structure, mechanical properties, characterized in that it is made of steel containing the following ratio of components, wt.%: carbon 0.95-1.05 manganese 0.20-0.40 silicon 0.17-0.37 nickel 0.005-0.30 aluminum 0.005-0.05 vanadium 0.005-0.03 sulfur 0.005-0.020 phosphorus 0.005-0.027 chromium 1.30-1.65 nitrogen 0.005-0.012 arsenic 0.0001-0.03 tin 0.0001-0.02 lead 0.0001-0.01 zinc 0.0001-0.005 iron and inevitable impurities  rest, when fulfilling the relations: (As + Sn + Pb + 5 × Zn) ≤0.07; 0.30≤ (Mn / 6 + Cr / 5) ≤0.38, at the same time, it has a real perlite grain size of 6–9 points, a macrostructure by central porosity, point heterogeneity, shrink segregation of not more than 2 points for each species, a liquidation square, liquidation strips of not more than 0.5 points, non-metallic inclusions by point sulfides, oxides point, stitch oxides, silicates brittle ductile silicates, silicates undeformed not more than 2.0 points for each species, a tear resistance of less than 590 N / mm ² yield strength of not less than 390 N / mm ^2, the relative extension not less than 21%, relative narrowing not less than 45%, impact strength KCU not less than 440 kJ / m ² , hardness 179-217 HB. 2. The pipe billet according to claim 1, characterized in that the steel contains as inevitable impurities, wt%: copper no more than 0.25, molybdenum no more than 0.03, oxygen no more than 0.0015, titanium no more than 0.005. 3. The tube stock according to claim 1 or 2, characterized in that when the content in steel, wt.%: Nickel 0.005-0.10, sulfur 0.005-0.010, phosphorus 0.005-0.015, it has a temporary tensile strength of at least 590 N / mm ² , yield strength not less than 390 N / mm ² , elongation not less than 24%, relative narrowing not less than 48%, impact strength KCU not less than 550 kJ / m ² , hardness 179-217 HB. 4. The tube stock according to claim 1 or 2, characterized in that when the content in steel, wt.%: Nickel 0.10-0.30, sulfur 0.010-0.020, phosphorus 0.015-0.027 it has a temporary tensile strength of at least 610 N / mm ^2, yield stress of not less than 410 N / mm ^2, an elongation of at least 21%, relative narrowing of at least 45%, toughness KCU least 440 kJ / m ^2, hardness HB 179-217.