阅读说明：本技术 一种不锈钢复合耐火钢筋及其制造方法 (Stainless steel composite fire-resistant reinforcing steel bar and manufacturing method thereof ) 是由 向勇 黄玲 曾麟芳 李聚良 于 2021-08-06 设计创作，主要内容包括：本发明公开了一种不锈钢复合耐火钢筋,包括：不锈钢耐腐蚀外层、耐火钢钢芯和冶金结合过渡层,不锈钢耐腐蚀外层包覆在耐火钢钢芯外周,不锈钢耐腐蚀外层与耐火钢钢芯组坯后热轧使得两者相互渗透而形成冶金结合过渡层；不锈钢耐腐蚀外层、所述耐火钢钢芯与冶金结合过渡层的厚度之比为1：(10-200)：(0.1-5)。(The invention discloses a stainless steel composite fire-resistant reinforcing steel bar, which comprises: the stainless steel corrosion-resistant outer layer is coated on the periphery of the refractory steel core, and the stainless steel corrosion-resistant outer layer and the refractory steel core are assembled and then are subjected to hot rolling to enable the stainless steel corrosion-resistant outer layer and the refractory steel core to mutually permeate to form a metallurgical bonding transition layer; the thickness ratio of the stainless steel corrosion-resistant outer layer to the steel core to the metallurgical bonding transition layer is 1: (10-200): (0.1-5).)

1. A stainless steel composite refractory rebar, comprising: the steel core structure comprises a stainless steel corrosion-resistant outer layer (1), a refractory steel core (2) and a metallurgical bonding transition layer (3), wherein the stainless steel corrosion-resistant outer layer (1) is coated on the periphery of the refractory steel core (2), and the stainless steel corrosion-resistant outer layer (1) and the refractory steel core (2) are assembled and then are subjected to hot rolling to enable the stainless steel corrosion-resistant outer layer and the refractory steel core to mutually permeate to form the metallurgical bonding transition layer (3); the thickness ratio of the stainless steel corrosion-resistant outer layer (1), the refractory steel core (2) and the metallurgical bonding transition layer (3) is 1: (10-200): (0.1-5).

2. The stainless steel composite refractory steel bar as claimed in claim 1, wherein the stainless steel corrosion-resistant outer layer (1) is made of stainless steel pipe, and 2205, 304, 316 or 316L is selected as the stainless steel material of the stainless steel corrosion-resistant outer layer (1); the thickness of the stainless steel corrosion-resistant outer layer (1) is 0.10mm-2.00mm, and the weight of the stainless steel corrosion-resistant outer layer (1) accounts for 1% -18% of the total weight of the composite fire-resistant reinforcing steel bar.

3. The stainless steel composite refractory according to claim 1, wherein said refractory steel core (2) is made of a refractory steel billet or a low-alloy steel, said refractory steel core (2) having the composition: 0.15-0.25 wt% of C, 0.30-0.55 wt% of Si, 1.25-1.35 wt% of Mn, 0.35-0.75 wt% of Cr, 0.25-0.75 wt% of Mo, 0.3-0.6 wt% of Ni, 0.05-0.15 wt% of Ti and 0.05-0.15 wt% of V, the balance being Fe and inevitable impurities; the diameter of the refractory steel core (2) is 5.00mm-45 mm.

4. The stainless steel composite refractory according to any one of claims 1 to 3, wherein the inner surface of the stainless steel corrosion-resistant outer layer (1) is inwardly protruded with an inverted rib structure (11), the inverted rib structure (11) is formed by hot rolling so that the inner surface of the stainless steel corrosion-resistant outer layer (1) is inwardly extended, and the height of the inward protrusion of the inverted rib structure (11) is 0.01mm to 0.03 mm.

5. The stainless steel composite refractory steel according to any one of claims 1 to 3, wherein the outer surface of the stainless steel corrosion-resistant outer layer (1) is provided with an inclined rib structure (12), and the inclined rib structure (12) is welded or riveted on the outer surface of the stainless steel corrosion-resistant outer layer (1); or the inclined rib structure (12) and the stainless steel corrosion-resistant outer layer (1) are of an integrally formed structure; the height of the inclined rib structure (12) protruding out of the surface of the stainless steel corrosion-resistant outer layer (1) is 0.1mm-3.0 mm.

6. The manufacturing method of the stainless steel composite fire-resistant reinforcing steel bar is characterized by comprising the following steps:

firstly, manufacturing a stainless steel pipe serving as a stainless steel corrosion-resistant outer layer (1) and a refractory steel blank serving as a refractory steel core (2) according to a preset size, and performing cleaning treatment for removing impurities and dirt on the inner surface of the stainless steel pipe and the outer surface of the refractory steel blank; then assembling the stainless steel pipe and the refractory steel billet to obtain a stainless steel-refractory steel composite billet;

secondly, placing the assembled stainless steel-refractory steel composite billet into vacuum packaging equipment, vacuumizing the vacuum packaging equipment, removing air between the stainless steel pipe and the refractory steel billet to enable the vacuum degree to be larger than or equal to 0.001MPa, and welding and sealing two ends of the stainless steel-refractory steel composite billet in the vacuum packaging equipment;

step three, heating the welded and sealed stainless steel-refractory steel composite billet to 1050-1150 ℃ in a heating furnace for 1-3 hours to ensure that the internal and external temperatures of the stainless steel-refractory steel composite billet are uniform;

and step four, discharging the heated stainless steel-refractory steel composite billet out of the furnace for hot rolling, controlling the initial rolling temperature to be 1000-1150 ℃, controlling the final rolling temperature to be not lower than 800 ℃, and obtaining the stainless steel composite refractory reinforcing steel bar through a multi-pass hot rolling process according to the designed size and shape.

7. The method of manufacturing according to claim 6, wherein after step four, the stainless steel composite refractory bar produced further comprises a cooling step: and (3) enabling the stainless steel composite refractory steel bar coming out of the hot rolling mill to enter a water tank for water cooling, and controlling the temperature of the stainless steel composite refractory steel bar after the water cooling to be 600-800 ℃.

8. The manufacturing method according to claim 6, wherein in the fourth step, the hot rolling pass of the stainless steel-refractory steel composite billet is 10-18 passes, wherein the rolling pass adopted in the first 4 passes of the hot rolling is elliptical hole-circular hole-elliptical hole-circular hole, and the deformation amount of each hot rolling in the first 4 passes is 5-20%.

9. The manufacturing method according to claim 6, wherein in the first step, the cleaning treatment method for the inner surface of the stainless steel pipe comprises the following steps: removing oxide skin and oil stain on the inner surface by an acid washing method; the cleaning treatment method of the outer surface of the refractory steel billet comprises the following steps: removing oxide skin and impurities on the outer surface by a shot blasting or mechanical processing method; a gap of 0.9-2.5 mm is formed between the stainless steel pipe and the refractory steel billet which are assembled into the stainless steel-refractory steel composite billet.

10. The manufacturing method according to claim 6, wherein in the third step, the stainless steel-refractory steel composite billet is heated in a heating furnace under a weakly oxidizing atmosphere or under the protection of inert gas; if the weak oxidizing atmosphere is adopted, the oxygen volume content of the weak oxidizing atmosphere is equal to or less than 1.5 percent; if the inert gas is adopted for protecting the hot rolling, the inert gas is helium or argon.

Technical Field

The invention relates to the technical field of steel bars and steel bar manufacturing, in particular to a stainless steel composite fire-resistant steel bar and a manufacturing method of the stainless steel composite fire-resistant steel bar.

Background

The building steel is one of three main materials of building materials and can be divided into steel for a steel structure and steel bars for a reinforced concrete structure. With the development of economic society, large-scale, large-span and high-rise buildings are continuously emerged, the current building foundation of China still mainly comprises reinforced concrete, and the consumption of ribbed steel bars in the steel for the buildings is the largest. With the emergence of multifunctional building structures such as high-rise, large-span, earthquake-proof, low temperature resistant, fire-resistant and the like, the hot-rolled ribbed steel bar is required to have higher strength, toughness, better weldability and other comprehensive properties.

The microalloying technology is a main technical route for developing high-strength steel bars in various countries in the world, wherein the microalloying technology of vanadium, niobium and titanium becomes a hotspot for developing the high-strength steel bars by using the remarkable technical and economic advantages. By utilizing the pinning effect of fine carbide, nitride or carbonitride formed by vanadium, niobium and titanium in steel, the growth of austenite grains is prevented in the reheating process, the recrystallization of deformed austenite is prevented in the recrystallization controlled rolling process, and the growth of recrystallized austenite grains is delayed, so that the comprehensive performance of the steel bar is obviously improved, and the composite microalloying effect is greater than the sum of a certain element added independently. The vanadium-titanium composite microalloying method has the advantages that vanadium-titanium resources in Panxi areas of China are rich, and the production of the high-strength steel bars by adopting the vanadium-titanium composite microalloying method has important significance for novel urbanization construction and energy conservation and emission reduction of China.

The invention fully utilizes the bimetal composite principle and the composite technology, the outer layer of the steel bar adopts austenitic stainless steel or duplex stainless steel, the core part adopts microalloyed or low-alloy heat-resistant steel core, and the corrosion-resistant heat-resistant high-strength steel bar which has high strength, corrosion resistance, excellent heat resistance, stable performance and easy popularization is developed.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a stainless steel composite fire-resistant reinforcing steel bar and a manufacturing method thereof, wherein the stainless steel composite fire-resistant reinforcing steel bar has the characteristics of high strength, excellent corrosion resistance and heat resistance and stable performance. In order to solve the above problems, the technical solution provided by the present invention is as follows:

the invention relates to a stainless steel composite fire-resistant reinforcing steel bar, which comprises: the stainless steel corrosion-resistant outer layer is coated on the periphery of the refractory steel core, and the stainless steel corrosion-resistant outer layer and the refractory steel core are assembled and then are subjected to hot rolling to mutually permeate to form the metallurgical bonding transition layer; the thickness ratio of the stainless steel corrosion-resistant outer layer to the refractory steel core to the metallurgical bonding transition layer is 1: (10-200): (0.1-5).

Compared with the composite steel bar in the prior art, the stainless steel composite fire-resistant steel bar has the advantages that the structure that the outer layer corrosion-resistant stainless steel and the fire-resistant steel core are combined is adopted, and the outer layer corrosion-resistant stainless steel and the fire-resistant steel core mutually permeate to form the metallurgical bonding transition layer in the hot rolling process, so that each layer can exert the specific performance, namely, the stainless steel composite fire-resistant steel bar has good corrosion resistance and high toughness through the outer layer corrosion-resistant stainless steel pipe, and is suitable for various complex application scenes, such as coastal building construction, key bridge engineering and the like; the stainless steel composite fire-resistant steel bar has high strength, good toughness, good fire-resistant and high-temperature-resistant performances, greatly improved bending resistance and greatly improved strength through the inner fire-resistant steel core; meanwhile, the metallurgical bonding transition layer between the inner layer and the outer layer, namely the contact part of the inner layer and the outer layer is mutually permeated and fused to form an integral structure, so that the stainless steel composite fire-resistant reinforcing steel bar obtains good elongation after breakage, the integral performance of the stainless steel composite fire-resistant reinforcing steel bar is greatly improved, and the standard requirement of the fire-resistant reinforcing steel bar is met.

Further, the stainless steel corrosion-resistant outer layer is made of a stainless steel pipe, and 2205, 304, 316 or 316L and the like are selected as stainless steel materials for the stainless steel corrosion-resistant outer layer; the thickness of the stainless steel corrosion-resistant outer layer is 0.10mm-2.00mm, and the weight of the stainless steel corrosion-resistant outer layer accounts for 1% -18% of the total weight of the composite refractory steel bar.

Further, the refractory steel core is made of a refractory steel bar billet or a low alloy steel, and the refractory steel core comprises the following components: 0.15-0.25 wt% of C, 0.30-0.55 wt% of Si, 1.25-1.35 wt% of Mn, 0.35-0.75 wt% of Cr, 0.25-0.75 wt% of Mo, 0.3-0.6 wt% of Ni, 0.05-0.15 wt% of Ti and 0.05-0.15 wt% of V, the balance being Fe and inevitable impurities; the diameter of the refractory steel core is 5.00mm-45 mm.

Furthermore, an inverted rib structure extends inwards from the inner surface of the stainless steel corrosion-resistant outer layer, the inner surface of the stainless steel corrosion-resistant outer layer extends inwards through hot rolling, and the inward extending height of the inverted rib structure is 0.01mm-0.03 mm. Furthermore, the outer surface of the refractory steel core is provided with protrusions or ribs, and the height of the protrusions or ribs protruding out of the surface of the refractory steel core is 0.01mm-0.5 mm.

Further, an inclined rib structure is arranged on the outer surface of the stainless steel corrosion-resistant outer layer, and the inclined rib structure is welded or riveted on the outer surface of the stainless steel corrosion-resistant outer layer; or the inclined rib structure and the stainless steel corrosion-resistant outer layer are of an integrally formed structure; the height of the inclined rib structure protruding out of the surface of the corrosion-resistant outer layer of the stainless steel is 0.1mm-3.0 mm.

The invention discloses a method for manufacturing a stainless steel composite fire-resistant reinforcing steel bar, which comprises the following steps:

firstly, manufacturing a stainless steel pipe serving as a stainless steel corrosion-resistant outer layer and a refractory steel blank serving as a refractory steel core according to a preset size, and performing cleaning treatment for removing impurities and dirt on the inner surface of the stainless steel pipe and the outer surface of the refractory steel blank; and then assembling the stainless steel pipe and the refractory steel billet to obtain the stainless steel-refractory steel composite billet.

And secondly, placing the assembled stainless steel-refractory steel composite billet into vacuum packaging equipment, vacuumizing the vacuum packaging equipment, removing air between the stainless steel pipe and the refractory steel billet to enable the vacuum degree to be greater than or equal to 0.001MPa, and welding and sealing two ends of the stainless steel-refractory steel composite billet in the vacuum packaging equipment.

And step three, heating the welded and sealed stainless steel-refractory steel composite billet to 1050-1150 ℃ in a heating furnace for 1-3 hours to ensure that the internal and external temperatures of the stainless steel-refractory steel composite billet are uniform.

And step four, discharging the heated stainless steel-refractory steel composite billet out of the furnace for hot rolling, controlling the initial rolling temperature to be 1000-1150 ℃, controlling the final rolling temperature to be not lower than 800 ℃, and obtaining the stainless steel composite refractory reinforcing steel bar through a multi-pass hot rolling process according to the designed size and shape.

Further, after the fourth step, the prepared stainless steel composite refractory steel bar further comprises a cooling step: and (3) enabling the stainless steel composite refractory steel bar coming out of the hot rolling mill to enter a water tank for water cooling, and controlling the temperature of the stainless steel composite refractory steel bar after the water cooling to be 600-800 ℃.

Further, in the fourth step, the hot rolling pass of the stainless steel-refractory steel composite billet is 10 to 18 passes, wherein the rolling pass adopted in the first 4 passes of hot rolling is elliptical hole-circular hole-elliptical hole-circular hole, and the deformation amount of each hot rolling in the first 4 passes is 5 to 20 percent.

Further, in the step one, the cleaning treatment method of the inner surface of the stainless steel pipe comprises the following steps: removing oxide skin and oil stain on the inner surface by an acid washing method; the cleaning treatment method of the outer surface of the refractory steel billet comprises the following steps: removing oxide skin and impurities on the outer surface by a shot blasting or mechanical processing method; a gap of 0.9-2.5 mm is formed between the stainless steel pipe and the refractory steel billet which are assembled into the stainless steel-refractory steel composite billet.

Further, in the third step, when the stainless steel-refractory steel composite billet is heated in the heating furnace, the stainless steel-refractory steel composite billet is heated in a weak oxidizing atmosphere or under the protection of inert gas; if the weak oxidizing atmosphere is adopted, the oxygen volume content of the weak oxidizing atmosphere is equal to or less than 1.5 percent; if the inert gas is adopted for protecting the hot rolling, the inert gas is helium or argon.

The stainless steel composite fire-resistant reinforcing steel bar and the manufacturing method thereof have the beneficial effects that:

by adopting the structure that the outer layer corrosion-resistant stainless steel and the refractory steel core are combined, and the outer layer corrosion-resistant stainless steel and the refractory steel core are mutually permeated to form a metallurgical bonding transition layer in the hot rolling combination process, each layer can play the specific performance, namely, the stainless steel composite refractory reinforcing steel bar has good corrosion resistance and high toughness through the outer layer corrosion-resistant stainless steel pipe, and is suitable for various complex application scenes, such as coastal building construction, key bridge engineering and the like; the stainless steel composite fire-resistant steel bar has high strength, good toughness, good fire-resistant and high-temperature-resistant performances, greatly improved bending resistance and greatly improved strength through the inner fire-resistant steel core; meanwhile, the metallurgical bonding transition layer between the inner layer and the outer layer, namely the contact part of the inner layer and the outer layer is mutually permeated and fused to form an integral structure, so that the stainless steel composite fire-resistant reinforcing steel bar obtains good elongation after breakage, the integral performance of the stainless steel composite fire-resistant reinforcing steel bar is greatly improved, and the standard requirement of the fire-resistant reinforcing steel bar is met.

By adopting the creative manufacturing method, firstly, the assembled stainless steel-refractory steel composite billet is placed into vacuum packaging equipment and vacuumized, and then the two ends of the stainless steel-refractory steel composite billet are welded and sealed, namely, the outer layer and the inner core are in a vacuum state, and no oxygen is arranged in the space and the gap between the outer layer and the inner core, so that the surfaces of the inner layer and the outer layer can not be oxidized in the heating and hot rolling processes of the stainless steel-refractory steel composite billet, the metallurgical bonding between the inner layer and the outer layer is better and firmer, and the overall performance after hot rolling is better. Secondly, the stainless steel-refractory steel composite billet with two sealed ends is heated in a weak oxidizing atmosphere or under the protection of inert gas, so that the outer layer of the stainless steel-refractory steel composite billet is prevented from being oxidized in the heating process, namely the outer layer of the stainless steel pipe is oxidized, and the corrosion resistance of the outer layer of the stainless steel is protected. Thirdly, the beginning rolling temperature and the end rolling temperature of the hot rolling are controlled, namely the whole hot rolling process is controlled within a certain temperature range, so that the shape change of the stainless steel-refractory steel composite billet can reach the preset requirement during the hot rolling and the metallurgical bonding between the outer layer and the inner layer is better.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic cross-sectional view of a first form of the stainless steel composite refractory reinforcing bar of the present invention;

FIG. 2 is a schematic cross-sectional view of a second form of the stainless steel composite refractory reinforcing bar of the present invention;

FIG. 3 is a schematic cross-sectional view of a third form of the stainless steel composite refractory reinforcing bar of the present invention;

fig. 4 is a schematic structural diagram of the stainless steel composite fire-resistant steel bar of the present invention.

The figures are labeled as follows:

1-a stainless steel corrosion resistant outer layer; 2-a refractory steel core; 3-metallurgical bonding transition layer; 11-inverted rib structure; 12-a diagonal rib structure; 21-protrusions or ribs.

Detailed Description

In order to make the technical solutions in the embodiments of the present invention better understood and make the above objects, features, and advantages of the present invention more comprehensible, specific embodiments of the present invention are described below with reference to the accompanying drawings.

It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example one

Referring to fig. 1 to 4, a stainless steel composite refractory steel bar of the present embodiment includes: the stainless steel corrosion-resistant outer layer 1, the refractory steel core 2 and the metallurgical bonding transition layer 3 are assembled, the stainless steel corrosion-resistant outer layer 1 is coated on the periphery of the refractory steel core 2, and the stainless steel corrosion-resistant outer layer 1 and the refractory steel core 2 are subjected to hot rolling to mutually permeate to form the metallurgical bonding transition layer 3; the thickness ratio of the stainless steel corrosion-resistant outer layer 1 to the refractory steel core 2 to the metallurgical bonding transition layer 3 is 1: (10-200): (0.1-5). Wherein, the stainless steel corrosion-resistant outer layer 1 is made of a stainless steel pipe, and the refractory steel core 2 is made of a refractory steel billet. Preferably, the outer surface of the refractory steel core 2 has protrusions or ribs 21, the protrusions or ribs 21 protruding from the surface of the refractory steel core 2 by a height of 0.01mm to 0.5 mm.

As a preferred embodiment, the stainless steel corrosion-resistant outer layer 1 is made of a stainless steel pipe, and 2205, 304, 316 or 316L and the like are selected as stainless steel materials for the stainless steel corrosion-resistant outer layer 1; the thickness of the stainless steel corrosion-resistant outer layer 1 is 0.10mm-2.00mm, and the weight of the stainless steel corrosion-resistant outer layer 1 accounts for 1% -18% of the total weight of the composite refractory steel bar.

The fire-resistant steel core 2 is made of fire-resistant steel bar billets or low alloy steel, and the fire-resistant steel core 2 comprises the following components: 0.15-0.25 wt% of C, 0.30-0.55 wt% of Si, 1.25-1.35 wt% of Mn, 0.35-0.75 wt% of Cr, 0.25-0.75 wt% of Mo, 0.3-0.6 wt% of Ni, 0.05-0.15 wt% of Ti and 0.05-0.15 wt% of V, the balance being Fe and inevitable impurities; the diameter of the refractory steel core 2 is 5.00mm-45 mm.

Further preferably, the inner surface of the stainless steel corrosion-resistant outer layer 1 is provided with an inverted rib structure 11 extending inwards, the inverted rib structure 11 is formed by hot rolling so that the inner surface of the stainless steel corrosion-resistant outer layer 1 extends inwards, and the height of the inward extending inverted rib structure 11 is 0.01mm-0.03 mm. The outer surface of the stainless steel corrosion-resistant outer layer 1 is provided with an inclined rib structure 12, and the inclined rib structure 12 is welded or riveted on the outer surface of the stainless steel corrosion-resistant outer layer 1; or the inclined rib structure 12 and the stainless steel corrosion-resistant outer layer 1 are of an integrally formed structure; the height of the inclined rib structure 12 protruding out of the surface of the stainless steel corrosion-resistant outer layer 1 is 0.1mm-3.0 mm.

Example two

The manufacturing method of the stainless steel composite fire-resistant reinforcing steel bar of the embodiment comprises the following steps:

firstly, manufacturing a stainless steel pipe serving as a stainless steel corrosion-resistant outer layer 1 and a refractory steel blank serving as a refractory steel core 2 according to a preset size, and performing cleaning treatment for removing impurities and dirt on the inner surface of the stainless steel pipe and the outer surface of the refractory steel blank; and then assembling the stainless steel pipe and the refractory steel billet to obtain the stainless steel-refractory steel composite billet.

And step two, placing the assembled stainless steel-refractory steel composite billet into vacuum packaging equipment, vacuumizing the vacuum packaging equipment, removing air between the stainless steel pipe and the refractory steel billet to enable the vacuum degree to be greater than or equal to 0.001MPa, and welding and sealing two ends of the stainless steel-refractory steel composite billet in the vacuum packaging equipment.

And step three, heating the welded and sealed stainless steel-refractory steel composite billet in a heating furnace to 1050-1150 ℃ for 1-3 hours to ensure that the internal and external temperatures of the stainless steel-refractory steel composite billet are uniform.

And step four, discharging the heated stainless steel-refractory steel composite billet out of the furnace for hot rolling, controlling the initial rolling temperature to be 1000-1150 ℃, controlling the final rolling temperature to be not lower than 800 ℃, and obtaining the stainless steel composite refractory reinforcing steel bar through a multi-pass hot rolling process according to the designed size and shape.

As a preferred embodiment, after the fourth step, the prepared stainless steel composite refractory steel bar further comprises a cooling step: and (3) putting the stainless steel composite refractory steel bar coming out of the hot rolling mill into a water tank for water cooling, and controlling the temperature of the stainless steel composite refractory steel bar after the water cooling to be 600-800 ℃.

Further preferably, in the fourth step, the hot rolling pass of the stainless steel-refractory steel composite billet is 10 to 18 passes, wherein the rolling pass adopted in the first 4 passes of the hot rolling is elliptical hole-circular hole-elliptical hole-circular hole, and the deformation amount of each hot rolling in the first 4 passes is 5 to 20 percent.

In the first step, the cleaning treatment method of the inner surface of the stainless steel pipe comprises the following steps: removing oxide skin and oil stain on the inner surface by an acid washing method; the cleaning treatment method of the outer surface of the refractory steel billet comprises the following steps: removing oxide skin and impurities on the outer surface by a shot blasting or mechanical processing method; a gap of 0.9mm-2.5mm is formed between the stainless steel pipe and the refractory steel billet which are assembled into the stainless steel-refractory steel composite billet.

In the third step, when the stainless steel-refractory steel composite billet is heated in a heating furnace, the stainless steel-refractory steel composite billet is heated in a weak oxidizing atmosphere or under the protection of inert gas; if the weak oxidizing atmosphere is adopted, the oxygen volume content of the weak oxidizing atmosphere is equal to or less than 1.5 percent; if the inert gas is adopted for protecting the hot rolling, the inert gas is helium or argon.

EXAMPLE III

Referring to fig. 1 to 4, in the stainless steel composite fire-resistant steel bar and the manufacturing method thereof of the present embodiment, the stainless steel corrosion-resistant outer layer 1 is 304 stainless steel, and the chemical composition (wt.%) of the fire-resistant steel core 2 is C: 0.24, Si: 0.55, Mn: 1.25, Cr: 0.55, Mo: 0.35, Ni: 0.35, Ti: 0.08, V: 0.08, and the balance of Fe and inevitable impurities.

Firstly, removing an oxide layer, impurities and oil stains on the inner wall of a 304 stainless steel pipe by adopting acid washing treatment, and removing defects of surface oxidation, slag inclusion and the like of a refractory steel billet by adopting a turning method; the refractory steel billet is sleeved into the 304 stainless steel tube by a hydraulic device.

Then, transferring the sleeved stainless steel-refractory steel composite billet into vacuum packaging equipment, vacuumizing to remove air in a gap between the stainless steel pipe and the refractory steel billet, wherein the vacuum degree is greater than or equal to 0.001 MPa; and welding and packaging two ends of the vacuumized stainless steel-refractory steel composite billet by using a plasma or electron beam welding machine.

And then transferring the packaged stainless steel-refractory steel composite billet into a heating furnace of a steel rolling mill, heating to 1100 ℃, discharging, and rolling into phi 25 deformed steel by 16 passes.

And finally, after the phi 25 deformed steel bar is taken out of the finish rolling stand, carrying out water penetration treatment in a water inlet tank, controlling the temperature of the penetrated water to be 700-750 ℃, then loading the deformed steel bar on a cooling bed, cooling and shearing and bundling the deformed steel bar.

Taking the above sample with the length of 450mm for mechanical property detection, wherein the performance of the steel bar is as follows:

serial number	Specification of	Test temperature/. degree.C	Yield strength/MPa	Tensile strength/MPa	A/％	Agt/％	Ratio of yield to strength
								1	Φ25	23	626	860	17.2	13.2	1.37
2	Φ25	23	632	865	18.6	12.8	1.37
								3	Φ25	600	455	555	23.8		1.22
4	Φ25	600	458	560	25.2		1.22

Example four

Referring to fig. 1 to 4, in the stainless steel composite fire-resistant steel bar and the manufacturing method thereof of the present embodiment, the stainless steel corrosion-resistant outer layer 1 is 304 stainless steel, and the chemical composition (wt.%) of the fire-resistant steel core 2 is C: 0.18, Si: 0.55, Mn: 1.25, Cr: 0.35, Mo: 0.25, Ni: 0.35, Ti: 0.08, V: 0.05, and the balance of Fe and inevitable impurities.

Firstly, removing an oxide layer, impurities and oil stains on the inner wall of a 304 stainless steel pipe by adopting acid washing treatment, and removing defects of surface oxidation, slag inclusion and the like of a refractory steel billet by adopting a turning method; and sleeving the refractory steel billet into the stainless steel pipe by adopting a hydraulic device.

Then, transferring the sleeved stainless steel-refractory steel composite billet into vacuum packaging equipment, vacuumizing to remove air in a gap between the stainless steel pipe and the refractory steel billet, wherein the vacuum degree is greater than or equal to 0.001 MPa; welding and packaging two ends of the vacuumized stainless steel-refractory steel composite billet by using a plasma or electron beam welding machine

And then transferring the packaged stainless steel-refractory steel composite billet into a heating furnace of a steel rolling mill, heating to 1100 ℃, discharging, and rolling into phi 25 deformed steel by 16 passes.

And finally, after the phi 25 deformed steel bar is taken out of the finish rolling stand, a water inlet tank is subjected to water penetration treatment, the temperature after water penetration is controlled to be 600-700 ℃, and then the deformed steel bar is put on a cooling bed, cooled and sheared and bundled.

Taking a 450mm long sample for mechanical property detection, wherein the performance of the steel bar is as follows:

serial number	Specification of	Test temperature/. degree.C	Yield strength/MPa	Tensile strength/MPa	A/％	Agt/％	Ratio of yield to strength
								1	Φ25	23	545	730	23.2	15.8	1.34
2	Φ25	23	540	730	22.6	16.4	1.35
								3	Φ25	600	385	450	26.6		1.17
4	Φ25	600	382	455	28.4		1.19

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments.

The embodiments of the present invention are described in detail above with reference to the drawings, but the present invention is not limited to the described embodiments. Various changes, modifications, substitutions and alterations to these embodiments will occur to those skilled in the art without departing from the spirit and scope of the present invention.