CN100347326C - Alloy-steel seam-less steel-pipe and production method therefor - Google Patents

Abstract

The invention provides an alloy steel seamless steel pipe, the chemical composition (weight %) of the alloy steel seamless steel pipe is: C≤0.12, Si≤0.30, Mn 0.30～0.60, Cr 4.00～6.00, Cu≤0.20, P <0.025, S<0.020, the balance is Fe. Also provided is a production method of the alloy steel seamless steel pipe. The effect of the invention is that the alloy steel seamless steel pipe material has good thermal stability, good impact toughness, stable permanent plasticity, high thermal strength and corrosion resistance, and its yield strength is not less than 195MPa. Through the use of special heat treatment and straightening process, the mechanical properties, creep resistance strength, high temperature strength and corrosion resistance of the alloy steel seamless steel pipe body can reach the level required by the standard, within the pressure and temperature range of its operation , has sufficient safety margin, and can meet the anti-oxidation and anti-corrosion requirements of the pipe body at the same time. By controlling the geometric dimensions, residual stress, shape deviation and chemical composition of the pipe body, the mechanical properties, high temperature resistance and corrosion resistance of the pipe body can be guaranteed.

Description

A kind of alloy steel seamless steel pipe and its production method

technical field

The invention relates to an alloy steel seamless steel pipe with good high-temperature mechanical properties and corrosion resistance used in pipelines of chemical equipment and power boilers and a production method thereof. The alloy steel pipe not only has high oxidation resistance and high-temperature steam resistance Corrosion performance, but also has good high impact toughness and stable long-lasting plasticity and thermal strength properties.

Background technique

Generally, alloy steel seamless steel pipes are used as furnace tubes for petroleum cracking units, high-temperature superheater tubes, steel tubes for reheaters, heat exchangers for nuclear power plants, boiler pipes, and steam pipes for high-temperature headers. In particular, it is one of the urgently needed products in industries such as power stations, energy and chemical industries, and it is also a product with high added value and high economic benefits. It is used as a superheater, reheater and main steam pipeline in power boilers, and it is also widely used in cracking, sulfur resistance, hydrogenation and other process devices in the petrochemical industry.

At present, my country's alloy steel seamless steel pipe mainly relies on imports. The difficulty of its manufacture lies in: the heat resistance and corrosion resistance caused by the deviation of the chemical composition of the material are low. Straightening and other manufacturing processes are prone to defects such as uneven deformation, cracks, folding, delamination and surface oxidation of alloy steel seamless steel pipes.

Contents of the invention

The purpose of the present invention is to provide a kind of alloy steel seamless steel pipe and its production method, which is suitable for the steel pipe with good high-temperature mechanical properties and corrosion resistance used in the pipelines of chemical equipment and power boilers, so as to meet the needs of thermal power stations, nuclear power plants, etc. High temperature, high pressure and corrosion resistance of steam pipes, superheater pipes, and reheater pipes of power stations, petroleum cracking equipment, and chemical pressure vessels. The alloy steel seamless steel pipe is a T5 steel grade seamless steel pipe, and the production and inspection are carried out according to the ASTM standard of the United States.

In order to achieve the above object, the technical solution adopted by the present invention is to provide a kind of alloy steel seamless steel pipe, the chemical composition (weight%) of the alloy steel seamless steel pipe is: C≤0.12, Si≤0.30, Mn 0.30～0.60, Cr4.00～6.00, Cu≤0.20, P＜0.025, S＜0.020, the balance is Fe.

The production method of the seamless steel pipe comprises the following steps:

Firstly, the alloy steel seamless steel pipe is made of sponge iron and scrap steel as raw materials for steelmaking, melted into molten steel in an electric arc furnace, refined outside the furnace and vacuum degassed to obtain the chemical composition of the alloy steel seamless steel pipe;

Then, it is continuously cast into a circular billet by a continuous casting machine, and the cooled continuous casting billet is heated in a heating furnace at a furnace temperature of 1260-1280°C, and the continuous casting billet is hot-rolled into an alloy steel seamless pipe. After the steel pipe, heat treatment: normalize with a bright normalizing furnace at a temperature of 920-960°C, and temper at a temperature of 680-690°C;

Then, thermal straightening is carried out at a temperature of 500°C-550°C.

After heat treatment, the mechanical properties of the alloy steel seamless steel pipe are sampled and prepared according to the requirements of the ASTM standard of the United States, and the indicators achieved by its mechanical properties are as follows:

Yield strength (σS) ≥ 195MPa;

Tensile strength (σb) ≥ 390MPa;

Elongation A%≥22%;

Hardness≤187HB;

Impact energy: the minimum value is calculated according to the American ASTM standard, ≥92J;

Wall thickness deviation: ≤±12.0t% (t is the wall thickness of seamless steel pipe);

Outer diameter deviation: ≤±1.0d% (d is the diameter of seamless steel pipe).

The effect of the invention is that the alloy steel seamless steel pipe material has good thermal stability, good impact toughness, stable permanent plasticity, high thermal strength and corrosion resistance, and its yield strength is not less than 195MPa. Through the use of special heat treatment and straightening process, the mechanical properties, creep resistance strength, high temperature strength and corrosion resistance of the alloy steel seamless steel pipe body can reach the level required by the standard, within the pressure and temperature range of its operation , has sufficient safety margin, and can meet the anti-oxidation and anti-corrosion requirements of the pipe body at the same time. By controlling the geometric dimensions, residual stress, shape deviation and chemical composition of the pipe body, the mechanical properties, high temperature resistance and corrosion resistance of the pipe body can be guaranteed.

Detailed ways

An alloy steel seamless steel pipe and its production method of the present invention will be described with reference to the examples.

An alloy steel seamless steel pipe with high temperature resistance and corrosion resistance, the chemical composition (weight%) of the alloy steel seamless steel pipe is: C≤0.12, Si≤0.30, Mn0.30～0.60, Cr4.00～6.00, Cu≤0.20, P<0.025, S<0.020, the balance is Fe.

The mechanical properties of the alloy steel seamless steel pipe require sampling and sample preparation according to the requirements of the American ASTM standard, and the technical indicators achieved are:

Yield strength (σS) 195MPa;

Tensile strength (σb) ≥ 390MPa;

Elongation A%≥22%;

Hardness≤187HB

Impact energy: the minimum value is calculated according to the American ASTM standard, ≥92J;

Wall thickness deviation: ≤±12.0t% (t is the wall thickness of seamless steel pipe);

Outer diameter deviation: ≤±1.0d% (d is the diameter of seamless steel pipe).

The production method of the above-mentioned seamless steel pipe provided comprises the following steps:

First of all, the alloy steel seamless pipe uses sponge iron and scrap steel as raw materials for steelmaking, and melts it into molten steel in an electric arc furnace. After refining outside the furnace and vacuum degassing, the chemical composition described in the alloy steel seamless pipe is obtained. , Continuous casting into round tube billets.

Then, the circular billet is continuously cast by the continuous casting machine, and the cooled continuous casting billet is heated in the annular heating furnace. Hot piercing at 1200-1240°C, continuous stretching and rolling at a temperature of 1000-1150°C, after constant reducing rolling, cooling, sawing to length, straightening, flaw detection, and inspection, the continuous casting billet After being rolled into alloy steel seamless steel pipe, heat treatment is carried out: normalize with a bright normalizing furnace at a temperature of 920-960°C (to prevent oxidation of the steel pipe surface), and temper at a temperature of 680-690°C.

Then, thermal straightening is carried out at a temperature of 500°C-550°C. Then at a temperature of 500°C-? Thermal straightening at a temperature above ℃, and finally flaw detection.

The normalizing adopts a bright normalizing furnace, and the tempering adopts air cooling.

The implementation process of the present invention is illustrated below through the examples.

Example:

Produce alloy steel seamless steel pipe (Φ114.3 * 13.49mm) according to the composition and method of alloy steel seamless steel pipe, its chemical composition and process parameters are as follows:

The chemical composition (weight %) of the alloy steel seamless steel pipe is: C≤0.12, Si≤0.30, Mn0.30～0.60, Cr 4.00～6.00, Cu≤0.20, P<0.025, S<0.020, and the balance is Fe.

Sponge iron and scrap steel are used as raw materials for steelmaking, melted into molten steel in an electric arc furnace, refined outside the furnace and vacuum degassed to obtain the above chemical composition, and continuously cast into round billets. The cooled continuous casting slab is heated in the ring heating furnace, the furnace temperature is 1260-1280°C, the temperature is 1250-1260°C for heat centering, the temperature is 1200-1240°C for hot piercing, the temperature is 1000-1150°C Continuous extension rolling, after fixed diameter rolling, cooling, fixed-length sawing, straightening, flaw detection, heat treatment: normalize with a bright heat treatment furnace at a temperature of 920-960°C (to prevent surface oxidation of the steel pipe), Temper at 680-690°C, then heat sizing at 580-610°C, heat straightening at 500-550°C, and finally flaw detection.

After heat treatment, the mechanical properties of the alloy steel seamless steel pipe can reach the following indicators:

Yield strength (σS) 425MPa;

Tensile strength (σb) ≥ 550MPa;

Elongation A%≥23%;

Hardness≤185HB

Impact energy: the minimum value is calculated according to the American ASTM standard, ≥107J;

Wall thickness deviation: ≤±(3.5～6)% (d is the diameter of seamless steel pipe);

Outer diameter deviation: ≤±0.50% (t is the wall thickness of seamless steel pipe).

The alloy steel seamless steel pipe has been successfully applied experimentally in a boiler factory in Heilongjiang Province, and the application effect is very good.

The invention relates to an alloy steel seamless steel pipe with good high-temperature mechanical properties and corrosion resistance used in pipelines of chemical equipment and power boilers and a production method thereof. The alloy steel pipe not only has high oxidation resistance and high-temperature steam resistance Corrosion performance, but also has good high impact toughness and stable long-lasting plasticity and thermal strength properties. Generally, it is used as the steam pipe of petroleum cracking plant furnace pipe, high temperature superheater pipe, reheater steel pipe, nuclear power plant heat exchanger, boiler pipe and high temperature header.

Claims (4)

1. An alloy steel seamless steel pipe with high temperature resistance and corrosion resistance, characterized in that: the chemical composition (weight %) of the alloy steel seamless steel pipe is: C≤0.12, Si≤0.30, Mn 0.30～0.60, Cr 4.00～6.00, Cu≤0.20, P<0.025, S<0.020, the balance is Fe. 2. The alloy steel seamless steel pipe with high temperature resistance and corrosion resistance according to claim 1, characterized in that: the mechanical properties of the alloy steel seamless steel pipe meet the technical indicators of sampling and sample preparation according to the requirements of the American ASTM standard for: Yield strength (σS) 195MPa; Tensile strength (σb) ≥ 390MPa; Elongation A%≥22%; Hardness≤187HB; Impact energy: the minimum value is calculated according to the American ASTM standard, ≥92J; Wall thickness deviation: ≤±12.0t%, where t is the wall thickness of the seamless steel pipe; Outer diameter deviation: ≤±1.0d%, where d is the diameter of the seamless steel pipe. 3. A production method of alloy steel seamless steel pipe according to claim 1, said production method comprising the following steps: Firstly, the alloy steel seamless steel pipe is made of sponge iron and scrap steel as raw materials for steelmaking, melted into molten steel in an electric arc furnace, refined outside the furnace and vacuum degassed to obtain the chemical composition of the alloy steel seamless steel pipe; Then, it is continuously cast into a circular billet by a continuous casting machine, and the cooled continuous casting billet is heated in a heating furnace at a furnace temperature of 1260-1280°C, and the continuous casting billet is hot-rolled into an alloy steel seamless pipe. After the steel pipe, heat treatment: normalize with a bright normalizing furnace at a temperature of 920-960°C, and temper at a temperature of 680-690°C; Then, thermal straightening is carried out at a temperature of 500°C-550°C. 4. The method according to claim 3, characterized in that: bright normalizing furnace is used for normalizing, and air cooling is used for tempering.