CN1926257A - Steel - Google Patents

Abstract

The invention relates to metallurgy, in particular to steels which have a high toughness at negative temperatures, a good weldability, embrittlement and corrosion resistance, a high-temperature resistance and which can be used for oil and gas products pipelines, offshore platforms, welded structures, pressure vessels, different technical devices and the elements thereof operating at a temperature ranging from minus 100 DEG C to plus 450 DEG C. The inventive steel comprises carbon, manganese, silicium, chromium, nickel, vanadium, niobium, titanium, aluminium, calcium, sulphur, phosphorus, nitrogen, copper, stibium, stannum, arsenic and iron and in addition molybdenum at the following component ratio: 0.02 mass % carbon, manganese 0.10-1.8 mass %, 0.06-0.6 mass % silicium, 0.005-0.30 mass % chromium, 0.005-1.0 mass % nickel, 0.01-0.12 mass % vanadium, 0.02-0.10 mass % niobium, 0.01-0.04 mass % titanium, 0.01-0.05 mass % aluminium, 0.0005-0.008 mass % calcium, 0.0005-0.008 mass % sulphur, 0.001-0.012 mass % phosphorus, 0.001-0.012 mass % nitrogen, 0.005-0.25 mass % copper, 0.0001-0.005 mass % stibium, 0.0001-0.007 mass % stannum, 0.0001-0.008 mass % arsenic, 0.0001-0.5 mass % molybdenum, the rest being iron. The total nickel and manganese mass % content is bound with the molybdenum and phosphorus mass % content according to the following equation: Ni + Mn 1 + Mo P CR 0.03.

Description

steel

technical field

The invention relates to the metallurgical industry, in particular to steel with high ductility at low temperature, good weldability, brittleness resistance, corrosion resistance and high temperature heat resistance. This steel can be used to manufacture oil pipelines, natural gas pipelines, product pipelines, offshore platforms, welded structures and high-pressure operating vessels, as well as various equipment and their components that operate at temperatures from -100°C to 450°C.

Background technique

The weight percent composition of known steel is as follows:

Carbon 0.03-0.11

Manganese 0.90-1.80

Silicon 0.06-0.60

Chromium 0.005-0.30

Nickel 0.005-0.30

Vanadium 0.02-0.12

Niobium 0.03-0.10

Titanium 0.010-0.040

Aluminum 0.010-0.055

Calcium 0.001-0.005

Sulfur 0.0005-0.008

Phosphorus 0.0005-0.010

Nitrogen 0.001-0.012

Copper 0.005-0.25

Antimony 0.001-0.005

Tin 0.001-0.007

Arsenic 0.001-0.008

The balance is iron

(Russian Federation Patent No. 2141002, published on November 10, 1999).

The steel has all the properties needed to manufacture oil pipelines, gas pipelines, product pipelines, offshore platforms and other welded structures operating at temperatures from -100°C to 450°C. But this steel does not have sufficient strength properties for the manufacture of the above-mentioned and other products from steel sheets exceeding 20 mm thick. This defect can be eliminated by increasing the hardening characteristics through high alloy content, but the steel shows brittleness.

Contents of the invention

The task of the present invention is to improve the strength properties of steel. The effects of the present invention are as follows: steel plates and billets with a thickness not exceeding 50 mm have the following properties: the yield stress is higher than 550 N/mm ² , the ultimate breaking strength is higher than 620 N/mm ² , and the temperature remains high at temperatures as low as -100°C. Ductility, resistance to brittleness during fabrication and operation, good weldability in factory and open air environments.

From a technical point of view, the desired effect can be achieved because the steel contains carbon, manganese, silicon, chromium, nickel, vanadium, niobium, titanium, aluminum, calcium, sulfur, phosphorus, nitrogen, copper, Antimony, tin, arsenic, iron and further containing molybdenum:

Carbon 0.02-0.11

Manganese 0.10-1.8

Silicon 0.06-0.6

Chromium 0.005-0.30

Nickel 0.005-1.0

Vanadium 0.01-0.12

Niobium 0.02-0.10

Titanium 0.01-0.04

Aluminum 0.01-0.05

Calcium 0.0005-0.008

Sulfur 0.0005-0.008

Phosphorus 0.001-0.012

Nitrogen 0.001-0.012

Copper 0.005-0.25

Antimony 0.0001-0.005

Tin 0.0001-0.007

Arsenic 0.0001-0.008

Molybdenum 0.0001-0.5

The balance is iron

Wherein, the relationship between the total content of nickel and manganese and the content (% by weight) of molybdenum and phosphorus satisfies the following equation:

$\frac{\mathrm{<span\; class="notranslate">\; Ni</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; mn</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Mo</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.03</span>}$

The stated limits of nickel, manganese, molybdenum and phosphorus in this steel, supported by the listed constituent levels, provide improved hardenability, low temperature (down to -100°C) High strength values and ductility, while eliminating embrittlement during the manufacture and use of products made from this steel plate.

Detailed ways

Table 1 shows the chemical composition of the three-heat steel of the present invention, and the composition of the known steel is used as a comparison. The composition was chosen to evaluate the contribution of molybdenum and nickel to the strength of the steel plate.

All runs were performed in a vacuum induction furnace. The charge consists of Amco iron with nickel, iron-molybdenum alloy, copper and other charges depending on the composition. When the required vacuum is reached in the furnace, the charge begins to melt. After complete melting, the metal is heated to 1630-1650°C to degas the charge, add the required predetermined amount of manganese, iron-vanadium alloy and ferroniobium alloy to the molten pool, and then add deoxidizer (iron-silicon alloy, aluminum and iron-titanium alloy ).

When the molten steel temperature reaches the desired level (1560-1580°C), the degassed metal flows directly from the melting furnace into the mold. Molded ingots are cooled in a mold under atmospheric pressure (rather than vacuum).

A total of 12 heats of test smelting were carried out in the vacuum induction furnace. The metal chemical composition of all heats was analyzed, and on the basis of the results, 3 heats were selected with an equivalent carbon content of 0.37.

The equivalent carbon content is determined according to the following formula:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; eq</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; mn</span>}}{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; Cr</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Mo</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Nb</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Ti</span>}}{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; Ni</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Cu</span>}}{\mathrm{<span\; class="notranslate">\; 15</span>}}$

Table 2 shows the properties of these heats, compared to a heat of known composition (with an equivalent carbon content of 0.37). The results obtained show that the new steel grade with the above composition has the required strength properties for a 50mm cross-section, as well as high ductility at low temperatures. The ratios of the total nickel and manganese content to the molybdenum and phosphorus concentrations for heats 1, 2, and 3 were 0.01, 0.0057, and 0.0064 (ie, less than 0.03), respectively.

Table 1 Comparison of the chemical composition of the steel from the third heat and the composition of the known steel

Table 2 Properties of steel in each heat of Table 1 Stoves Cross section (mm) Ultimate breaking strength (N/mm ² ) Yield stress (N/mm ² ) Ductility-brittle transition temperature (°C) 1 20/50 836/687 706/583 -90/-100 2 20/50 807/712 683/600 -90/-100 3 20/50 767/675 650/566 -90/-100 Heats of known steel 20/50 621/528 528/449 -80/-30

Claims (1)

1. A steel containing carbon, manganese, silicon, chromium, nickel, vanadium, niobium, titanium, aluminium, calcium, sulfur, phosphorus, nitrogen, copper, antimony, tin, arsenic and iron, characterized in that it also contains molybdenum, The percentage by weight of each composition is as follows: Carbon 0.02-0.11 Manganese 0.10-1.8 Silicon 0.06-0.6 Chromium 0.005-0.30 Nickel 0.005-1.0 Vanadium 0.01-0.12 Niobium 0.02-0.10 Titanium 0.01-0.04 Aluminum 0.01-0.05 Calcium 0.0005-0.008 Sulfur 0.0005-0.008 Phosphorus 0.001-0.012 Nitrogen 0.001-0.012 Copper 0.005-0.25 Antimony 0.0001-0.005 Tin 0.0001-0.007 Arsenic 0.0001-0.008 Molybdenum 0.0001-0.5 The balance is iron Wherein, in weight percent, the relationship between the total content of nickel and manganese and the content of molybdenum and phosphorus satisfies the following equation: $\frac{\mathrm{<span\; class="notranslate">\; Ni</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; mn</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Mo</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.03</span>}<span\; class="notranslate">\; .</span>$