CN113305166B - A kind of bimetal alloy steel composite pipe diameter expansion hot extrusion process - Google Patents

Abstract

A diameter-expanding hot extrusion process for a bimetal alloy steel composite pipe belongs to the technical field of seamless steel pipe forming, and is characterized by comprising the following process steps: 1) normalizing the bimetal as-cast tube blank; 2) expanding and hot extruding the bimetal cast-state tube blank: the extrusion temperature is determined by the inner surface temperature of the inner layer of the tube blank, the extrusion ratio is determined by the wall thickness ratio of the inner layer and the outer layer of the tube blank, and the extrusion speed is determined by the length of the pipe fitting; 3) and (3) quenching and tempering the hot extrusion composite pipe fitting. The invention has the advantages of improving the capability of coordinating plastic deformation of the inner layer and the outer layer, improving the bonding strength of the bonding interface of the inner layer and the outer layer and obtaining the composite pipe fitting with the increased caliber after hot extrusion.

Description

A kind of bimetal alloy steel composite pipe diameter expansion hot extrusion process

technical field

The invention belongs to the technical field of seamless steel pipe forming, and in particular relates to a diameter-expanding hot extrusion process of a bimetal alloy steel composite pipe.

Background technique

Bi-metal alloy steel seamless pipe is a pipe composed of two different metals, which can exert their respective performance characteristics, such as high strength, high toughness, wear resistance and corrosion resistance, etc. The key components in the equipment field are generally manufactured by the hot extrusion process. Before hot extrusion, the tube blank can be in two states of forging and casting. When the two tube blanks before extrusion are both forged, it is The billet is made by upsetting, punching and other processes, and the structure is dense. The two forged billets are assembled and then extruded into a composite pipe fitting. The extrusion process is mainly to ensure the external dimensions of the pipe fittings. Parameter control is relatively easy, but the process is lengthy, material and energy waste is serious, and equipment investment in upsetting and punching processes is huge; when the two tube blanks before extrusion are both as-cast, centrifugal casting or sand casting methods are used. The hollow as-cast tube blanks are made separately, with poor microstructure. The two as-cast tube blanks are fitted and assembled and then extruded into a composite tube. The extrusion process must not only ensure the overall dimensions of the tube, but also improve the The uniformity of the organization and the improvement of mechanical properties, this process has the outstanding advantages of short manufacturing process, saving materials and energy, and saving equipment investment.

Chinese Invention Patent Application No. "201010141598.8" discloses a 20/321H corrosion-resistant bimetallic composite pipe and its manufacturing process, including the following process steps: 1) centrifugal casting to obtain a bimetallic composite pipe blank, when the inner surface of the outer layer 20 steel is When the temperature is cooled to the melting point of the outer layer of molten metal at 50-80°C, the inner layer of 321H stainless steel molten metal begins to be poured. 2) The bimetallic composite tube blank is hot-extruded to make a waste tube, 3) The waste tube is softened and then cold-worked, and then carried out The finished pipe is obtained by heat treatment; in this invention, the inner and outer layers are completely metallurgically fused, and it is not easy to delaminate during use. Chinese Invention Patent Application No. "200910222747.0" discloses a method for preparing a bimetallic seamless steel pipe for an alkali recovery boiler, including the following process steps: 1) Selecting a metallurgically combined bimetallic centrifugal casting composite pipe blank, and performing the first Annealing treatment, the temperature is 1000-1100°C, and the temperature is kept for 20-30h. 2) The heating temperature of the billet before extrusion is 1180-1220°C, and the extrusion is carried out under the condition that the extrusion ratio is greater than 10. 3) The second annealing treatment, The temperature is 780-800°C, the temperature is kept for 2-3 hours, and then air-cooled; the outer metal layer of the composite pipe prepared by the invention is resistant to alkali corrosion, and the inner layer is resistant to high pressure, and will not cause delamination of the two layers of metal after flattening and bending .

When the bimetal alloy steel pipe is manufactured by the above method, there is shear friction at the contact part between the extrusion cylinder and the tube blank during the hot extrusion forming process, the bonding interface performance between the inner and outer layers is weak, the metal deformation is severe, and the coarse oxide particles or alloy elements Segregation will lead to the destruction of the structure, thereby reducing the interface bond strength performance, and the extrusion ratio and extrusion speed are often determined empirically during the hot extrusion process. The performance and quality of the pipe fittings after pressing has an important influence, and the existing technology cannot meet the high-performance and precise manufacturing requirements of this type of bimetal composite pipe with diameter-expanding hot extrusion.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a bimetal alloy steel composite pipe diameter expansion hot extrusion process, which can effectively overcome the shortcomings of the prior art.

The object of the present invention is achieved in this way, and it is characterized in that comprising the following processing steps:

(1) Normalizing treatment of bimetallic as-cast tube blanks: the normalizing temperature is 880-900 °C, and after reaching the preset holding time _t1 , air-cooled to room temperature with a blower, _t1 is determined by the outer wall thickness _b01 and inner wall thickness of the tube blank. The layer thickness b ₀₂ is determined, t ₁ =(2.2～2.8)×(b ₀₁ +b ₀₂ ), the unit of t ₁ is min, and the unit of b ₀₁ and b ₀₂ is mm;

(2) Hot extrusion of bimetallic as-cast tube blank with diameter expansion: as shown in Figure 2, 3 is the outer layer of bimetallic pipe fittings forgings, 4 is the inner layer of bimetallic pipe fittings forgings, 5 is extrusion rod, 6 is extrusion cylinder , 7 is the extrusion punch, the extrusion temperature T is determined by the inner surface temperature of the inner layer of the tube blank, and the extrusion starts when T = 1180 ~ 1220 ° C, and the extrusion ratio λ is determined by the ratio of the inner and outer wall thickness of the tube blank , λ=(15～18)×b ₀₁ /b ₀₂ ; the extrusion speed v is determined by the pipe length L, v=(1.1～1.8)×10 ^-2 ×L, the unit of L is mm; At room temperature, a bimetallic composite pipe fitting with expanded diameter and hot extrusion was obtained, as shown in Figure 3;

(3) Quenching and tempering treatment of hot extrusion composite pipe fittings: the quenching temperature is 850～870℃, the quenching holding time t ₂ is determined by the outer wall thickness b ₁ and inner wall thickness b ₂ of the pipe fitting, t ₂ =(4.2～4.8) ×(b ₁ +b ₂ ), water cooled to room temperature after reaching t ₂ ; the tempering temperature is 580～600℃, and the tempering holding time t ₃ is determined by b ₁ and b ₂ , t ₃ =(5.5～7.5)×( b ₁ +b ₂ ), air-cooled to room temperature after reaching t ₃ , the units of t ₂ and t ₃ are both min, and the units of b ₁ and b ₂ are mm;

The advantages and beneficial effects of the invention are as follows: according to the geometric size of the tube blank, the extrusion temperature, extrusion ratio and extrusion speed in the hot extrusion process are quickly and accurately determined, and the extrusion temperature is determined by the inner surface temperature of the inner layer of the tube blank. The pressure temperature and the large extrusion ratio can improve the coordinated plastic deformation ability of the inner and outer layers, and improve the bonding strength performance of the bonding interface between the inner and outer layers.

Description of drawings

Fig. 1 is the dimension identification drawing of bimetallic as-cast tube blank;

Fig. 2 is a schematic diagram of hot extrusion of bimetal as-cast tube blank with diameter expansion;

Fig. 3 is the dimension identification diagram of the bimetallic composite pipe fitting after hot extrusion;

In the figure: 1—Bimetallic tube blank outer layer 2—Bimetallic tube blank inner layer 3—Bimetallic pipe fitting forging outer layer 4—Bimetallic pipe fitting forging inner layer 5—Extrusion rod 6—Extrusion cylinder 7—Extrusion convex mold;

D ₀ - the outer diameter of the bimetallic tube blank, _{d0 - the inner diameter of the bimetallic tube blank, L 0 -} the length of the bimetallic tube blank, b ₀₁ - the outer wall thickness of the bimetallic tube blank, b ₀₂ - the bimetallic tube The inner wall thickness of the billet, D—the outer diameter of the bimetallic pipe fitting forging, d—the inner diameter of the bimetallic pipe fitting forging, L _— the length of the bimetallic pipe fitting forging, b1 _— the outer wall thickness of the bimetallic pipe fitting forging, b2 - The inner wall thickness of bimetallic pipe fittings forgings.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

Fig. 1 is the size identification diagram of the bimetal as-cast tube blank, Fig. 3 is the size identification diagram of the bimetal composite pipe fitting forging after diameter expansion hot extrusion, namely a kind of bimetal composite diameter expansion hot extrusion of the present invention pipe fittings.

Example 1

This embodiment provides a bimetal alloy steel composite pipe diameter expansion hot extrusion process. The outer layer is set to be pipeline steel X65, the inner layer is stainless steel 304L, and the dimensions of the bimetal as-cast tube blank are: outer diameter D=820mm, inner diameter d = 60mm, length L = 700mm, outer wall thickness b ₀₁ = 200mm, inner wall thickness b ₀₂ = 180mm; the dimensions of the hot extrusion bimetal composite pipe fittings are: outer diameter D = 1200mm, inner diameter d = 900mm, Length L=790mm, outer layer wall thickness b ₁ =40, inner layer wall thickness b ₂ =35mm; the forming process steps are:

(1) Normalizing treatment of bimetallic as-cast tube blank: the normalizing temperature is 880°C, and the preset holding time t ₁ =2.2×(200+180)=836min is reached, and then air-cooled to room temperature by a blower;

(2) Hot extrusion of bimetallic as-cast tube blank with diameter expansion: as shown in Figure 2, 3 is the outer layer of bimetallic pipe fittings forgings, 4 is the inner layer of bimetallic pipe fittings forgings, 5 is extrusion rod, 6 is extrusion cylinder , 7 is the extrusion punch, the extrusion temperature is determined by the inner surface temperature of the inner layer of the tube blank T = 1180 ° C, the extrusion ratio λ = 15 × 200/180 = 16.7, the extrusion speed v = 1.1 × 10 ^-2 × 790 = 8.69mm/s, air-cooled to room temperature after extrusion, and the obtained bimetal composite diameter-expanded hot extrusion pipe has the dimensions of outer diameter D = 1200 mm, inner diameter d = 900 mm, length L = 790 mm, and outer wall thickness b ₁ = 40 , the inner wall thickness b ₂ =35mm, as shown in Figure 3;

(3) Quenching and tempering treatment of hot extrusion composite pipe fittings: the quenching temperature is 850°C, the quenching holding time is t ₂ =4.2×(40+35)=315min, and after reaching t ₂ , the water is cooled to room temperature, and the tempering temperature is 580° C. Fire holding time t ₃ =5.5×(40+35)=412min, and air-cooled to room temperature after reaching t ₃ .

Example 2

This embodiment provides a bimetallic alloy steel composite pipe diameter expansion hot extrusion process. The outer layer is pipeline steel X65, the inner layer is stainless steel 304L, and the bimetal as-cast tube blank size is: outer diameter D=820mm, inner diameter d = 60mm, length L = 700mm, outer wall thickness b ₀₁ = 200mm, inner wall thickness b ₀₂ = 180mm; the dimensions of the hot-extruded bimetallic composite pipe are: outer diameter D = 1200mm, inner diameter d = 900mm, Length L=790mm, outer layer wall thickness b ₁ =40, inner layer wall thickness b ₂ =35mm; the forming process steps are:

(1) Normalizing treatment of bimetallic as-cast tube blanks: the normalizing temperature is 890°C, and after reaching the preset holding time t ₁ =2.5×(200+180)=950min, blower is used to cool to room temperature;

(2) Hot extrusion of bimetallic as-cast tube blank with diameter expansion: as shown in Figure 2, 3 is the outer layer of bimetallic pipe fittings forgings, 4 is the inner layer of bimetallic pipe fittings forgings, 5 is extrusion rod, 6 is extrusion cylinder , 7 is the extrusion punch, the extrusion temperature is determined by the inner surface temperature of the inner layer of the tube blank T = 1200 ° C, the extrusion ratio λ = 16 × 200/180 = 17.7, the extrusion speed v = 1.5 × 10 ^-2 × 790 =11.85mm/s, air-cooled to room temperature after extrusion, and the obtained bimetal composite diameter-expanded hot extrusion pipe has the dimensions of outer diameter D = 1200 mm, inner diameter d = 900 mm, length L = 790 mm, and outer wall thickness b ₁ = 40 , the inner wall thickness b ₂ =35mm, as shown in Figure 3;

(3) Quenching and tempering treatment of hot extrusion composite pipe fittings: the quenching temperature is 860°C, the quenching and holding time t ₂ =4.5×(40+35)=337min, and after reaching t ₂ , the water is cooled to room temperature, and the tempering temperature is 590° C. Fire holding time t ₃ =6.5×(40+35)=487min, and air-cooled to room temperature after reaching t ₃ .

Example 3

This embodiment provides a bimetal alloy steel composite pipe diameter expansion hot extrusion process. The outer layer is set to be pipeline steel X65, the inner layer is stainless steel 304L, and the dimensions of the bimetal as-cast tube blank are: outer diameter D=820mm, inner diameter d = 60mm, length L = 700mm, outer wall thickness b ₀₁ = 200mm, inner wall thickness b ₀₂ = 180mm; the dimensions of the hot extrusion bimetal composite pipe fittings are: outer diameter D = 1200mm, inner diameter d = 900mm, Length L=790mm, outer wall thickness b ₁ =40, inner wall thickness b ₂ =35mm; the forming process steps are:

(1) Normalizing treatment of bimetallic as-cast tube blanks: the normalizing temperature is 900°C, and after reaching the preset holding time t ₁ =2.8×(200+180)=1064min, use a blower to air-cool to room temperature;

(2) Hot extrusion of bimetallic as-cast tube blank with diameter expansion: as shown in Figure 2, 3 is the outer layer of bimetallic pipe fittings forgings, 4 is the inner layer of bimetallic pipe fittings forgings, 5 is extrusion rod, 6 is extrusion cylinder , 7 is the extrusion punch, the extrusion temperature is determined by the inner surface temperature of the inner layer of the tube blank T = 1220 ° C, the extrusion ratio λ = 18 × 200/180 = 20, the extrusion speed v = 1.8 × 10 ^-2 × 790 =14.22mm/s, air-cooled to room temperature after extrusion, and the obtained bimetal composite diameter-expanded hot extrusion pipe has dimensions of outer diameter D = 1200mm, inner diameter d = 900mm, length L = 790mm, and outer wall thickness b ₁ = 40 , the inner wall thickness b ₂ =35mm, as shown in Figure 3;

(3) Quenching and tempering treatment of hot extrusion composite pipe fittings: the quenching temperature is 870°C, the quenching and holding time is t ₂ =4.8×(40+35)=360min, and after reaching t ₂ , the water is cooled to room temperature, and the tempering temperature is 600° C. Fire holding time t ₃ =7.5×(40+35)=562min, and air-cooled to room temperature after reaching t ₃ .

Claims (1)

1. A diameter-expanding hot extrusion process for a bimetal alloy steel composite pipe is characterized by comprising the following process steps:

(1) normalizing the bimetal as-cast tube blank: the normalizing temperature is 880-900 ℃, and the preset heat preservation time t is reached ₁ Then air-cooled to room temperature by a blower t ₁ From the outer wall thickness b of the tube blank ₀₁ And inner layer wall thickness b ₀₂ Determination of t ₁ ＝(2.2～2.8)×(b ₀₁ +b ₀₂ )，t ₁ Unit is min, b ₀₁ And b ₀₂ The unit is mm;

(2) expanding and hot extruding the bimetal cast-state tube blank: the extrusion temperature T is determined by the inner surface temperature of the inner layer of the tube blank, the extrusion is started when T is 1180-1220 ℃, the extrusion ratio lambda is determined by the ratio of the wall thickness of the inner layer and the wall thickness of the outer layer of the tube blank, and lambda is (15-18) x b ₀₁ /b ₀₂ (ii) a The extrusion speed v is determined by the length L of the pipe, and v is (1.1-1.8) multiplied by 10 ^-2 The unit of the L is mm, and the bimetal composite pipe fitting is subjected to air cooling to room temperature after extrusion is finished to obtain an expanded-diameter hot-extruded bimetal composite pipe fitting;

(3) thermal refining treatment of the hot extrusion composite pipe fitting: the quenching temperature is 850-870 ℃, and the quenching heat preservation time t ₂ From the wall thickness b of the outer layer of the pipe ₁ And inner layer wall thickness b ₂ Determination of t ₂ ＝(4.2～4.8)×(b ₁ +b ₂ ) To reach t ₂ Cooling the mixture to room temperature by water; the tempering temperature is 580-600 ℃, and the tempering heat preservation time t ₃ B is formed by ₁ And b ₂ Determination of t ₃ ＝(5.5～7.5)×(b ₁ +b ₂ ) To reach t ₃ Post air cooling to room temperature t ₂ And t ₃ Units are min, b ₁ And b ₂ In mm.

Images