JPH0481209A - Manufacture of seamless stainless steel tube - Google Patents

Abstract

PURPOSE:To enable piercing and elongation continuously, at a large quantity and with poor surface flaws by using an inclined roll mill, spraying cooling water to the rolls from a mist nozzle, and/or removing excessive cooling water on the roll surfaces with a wiper. CONSTITUTION:A billet, a bloom, a hollow tube stock 8 of austenitic stainless steel wherein component ranges in weight % are composed of <=0.5% C, 0.1-5.0% Si, 0.1-5.0% Mn, 10-50% Cr, 3-50%Ni, 1.0-5.0 Mo, <=0.01% S, <=0.03% P, <=0.03% O, 0.01-0.25% N, a content of each element satisfies an expression 1 and the balance is composed of Fe and unavoidable impurities are used. They are heated uniformly at a temperature zone 800-1300 deg.C, then, cooling water to rolls 1 is sprayed from mist nozzles 2 and/or they are pierced or elongated by an inclined roll mill for removing excessive cooling water by wipers 6 from the roll surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for drilling and stretching in a method for manufacturing seamless austenitic stainless steel pipes using a Mannesmann pipe-forming inclined roll rolling mill.

Conventional technology Seamless austenitic stainless steel pipes exhibit excellent corrosion resistance, oxidation resistance, and high-temperature strength in corrosive environments containing CO2 and I-I2S, and are therefore widely used in oil country tubular goods, geothermal country tubular goods, and geothermal country tubular goods.
It is becoming widely used for line pipes, etc.

Seamless austenitic stainless steel pipes are generally manufactured using inclined rolling methods such as the Mannesmann plug mill method and the Mannesmann Arasel mill method, or the Eugene Séjournet method.
It is manufactured using a hot extrusion method such as the Erhard-Buschbench method.

Among these, when manufacturing seamless pipes using the inclined rolling method using austenitic stainless steel as material, when drilling or stretching is performed while supplying roll cooling water, excess cooling water adhering to the rolls flows around to the rolled material. That will happen. As a result, the surface temperature of the material to be rolled decreases, and the deformation resistance increases locally on the surface, causing tool seizure flaws such as guide shoe flaws, and furthermore making subsequent mill rolling operations difficult. .

For this reason, during perforation or stretching with an inclined roll rolling mill, the roll cooling water is either completely stopped, or cooling water is supplied to the rolls during rolling intervals between the rolled material and the next material to cool the rolls. It is carried out.

Problems to be Solved by the Invention In manufacturing seamless pipes using the inclined rolling method using the austenitic stainless steel mentioned above, when the roll cooling water is completely stopped and a large amount of holes are perforated or stretched, the surface temperature of the inclined rolls increases. However, seizure occurs on the roll surface and a slip phenomenon occurs between the corrugated material and the roll due to plastic flow.

This slip phenomenon causes surface flaws to occur in the material to be rolled, misrolling such as bottom clogging, and rolling may become impossible. Furthermore, in the method of supplying cooling water to the rolls during rolling intervals between the material to be rolled and the next material, it is necessary to stop the rolling operation for 30 seconds or more until the rolls are completely cooled. This results in a decrease in production efficiency, and also causes the length of time the rolled material remains in the heating furnace to be extended, causing surface flaws on the rolled material due to high-temperature corrosion.

The purpose of this invention is to solve the above-mentioned problems in the production of seamless pipes made of austenitic stainless steel, and to produce seamless pipes that can be continuously punched and drawn in large quantities and stably with few surface defects. The purpose is to provide a manufacturing method.

In addition, hot workability is improved by limiting the content of each element, s, o, and p content in the austenitic stainless steel, and further adding Ca, B, and rare earth elements.

Means for Solving the Problems In order to achieve the above object, as a result of various studies, the rolling rolls are cooled by supplying roll cooling water so that it does not come into direct contact with the rolled material. Alternatively, we have reached the conclusion that the problem can be solved by removing excess cooling water before the rolls come into contact with the rolled material so that the roll cooling water does not come into direct contact with the rolled material.

That is, in this invention, the component range is, in weight%, C: 0.5% or less, Si: 0.1 to 5.0%, M
n: 0.1-5.0%, Cr: 10-50%, N
i: 3-50%, Mo: 1.0-5.0%,
S: 0.01% or less, P: 0.03% or less, 0:0
．． 03% or less, N: 0.01 to 0.25%, the content of each element satisfies the following formula (1), and the balance is Fe and unavoidable impurities. , Inclined roll rolling mill in which the hollow shell is soaked in a temperature range of 800 to 1300°C, then cooling water is sprayed onto the rolls from a mist nozzle, and excess cooling water on the roll surface is removed by a wiper. perforation or stretching.

△ [Ni] = %Ni+0.57. Mn+30(Z
C+ZN)+8.2-1.1 (%Cr+%Mo+1.
5ZSi+〇, 5%Nb) ≧-2,0-Formula (1) In addition, the component range is in weight%: C: 0.5% or less, Si: 0.1 to 5.0%, M
n: 0.1-5.0%, Cr: 10-50%,
Ni: 3-50%, Mo: 1.0-5.0%
, S: 0.01% or less, P: 0.03% or less, 0:
0.03% or less, N: 0.01 to 0.25%, the content of each element satisfies the following formula (1), and one or more rare earth elements, Ca5B, o, ooio
~0.3%, the balance being Fe and unavoidable impurities, billets, blooms, and hollow tubes of austenitic stainless steel are soaked in a temperature range of 800 to 1300°C, and then cooling water is applied to the rolls through a mist nozzle. Perforation or stretching is carried out using an inclined roll rolling mill in which excess cooling water is sprayed from the surface of the roll and/or excess cooling water on the roll surface is removed by a wiper.

△[Ni] = ZNi+0.5%Mn+30 (ZC
+ZN)+8.2-1.1 (Er+%Mo+1.5Z
Si+0.5XNb) ≧-2,0-(1) Formula % Formula % The reason why the composition range of the austenitic stainless steel is limited in the method of this invention will be explained. Note that all percentages of steel components hereinafter indicate weight percentages unless otherwise specified.

The reason why the C content is set to 0.5% or less is that if the C content is too large, corrosion resistance will decrease due to the generation of Cr carbides.

Setting Si to 0.1 to 5.0% deoxidizes better than Si, but if it is less than 0.1%, there is no effect, and if it exceeds 5.0%, the toughness of the steel decreases.

The reason for setting Mn to 0.1 to 5.0% is that Mn is necessary to increase high-temperature strength, but it has no effect if it is less than 0.1%, and if it exceeds 5.0%, it reduces the strength of the steel. decreases.

The reason why Cr is set at 10 to 50% is that Cr is necessary to increase high-temperature strength, but if it is less than 10%, it will not be effective as a stainless steel, and if it exceeds 50%, it will generally lose its austenitic state. .

The reason why Ni is set at 3 to 50% is that Ni is necessary to increase high-temperature strength, but if it is less than 3%, it has no effect on improving high-temperature strength, and if it exceeds 50%, it generally leaves the austenitic system. .

Mo is set at 1.0 to 5.0% because Mo is necessary to increase high-temperature strength, but if it is less than 1.0%, it has no effect on improving high-temperature strength, and if it exceeds 5.0%, This is because toughness decreases.

S 0.01% or less, P 0.03% or less, O 0.0
The reason why the content is set at 3% or less is that S, P, and 0 all weaken grain boundaries and deteriorate hot workability.

The reason why N is set at 0.01 to 0.25% is that N is a necessary element to improve hot workability, but if it is less than 0.01%, it has no effect. This is because the toughness deteriorates if it exceeds this.

The content of each element was limited to satisfy the following formula (1) in order to stabilize the austenite phase.

△ [Ni] =χNi+0.5%Mn+30CZC+
ZN)+8.2-1.1 ('lcr+XMo+1.5
ZSi+0.5%Nb) ≧-2,0-(1) Formula rare earth metal, Ca, and B are set to 0.0010-0.3% because
Rare earth elements, Ca, and B are necessary to improve hot workability, but if they are less than 0.0010%, they are ineffective, and
This is because if it exceeds 0.3%, the cleanliness deteriorates.

In this invention, billets, blooms, and hollow tubes of austenitic stainless steel having the above-mentioned composition are
After soaking in a temperature range of 0 to 1300°C, perforation or stretching is performed using an inclined roll rolling mill that sprays cooling water onto the roll from a mist nozzle and/or removes excess cooling water on the roll surface with a wiper. Since the cooling water sprayed onto the rolls by the mist spray nozzle is in the form of extremely fine mist, it quickly evaporates due to the heat retained by the rolls and does not circulate into the material to be rolled. In addition, since the wiper is placed on the roll surface, the cooling water sprayed on the roll is scraped off by the wiper.
It does not go around to the rolled material, and local cooling of the rolled material can be completely prevented.

As a wiper placed on the roll surface, a heat-resistant rubber draining plate is placed along the entire length of the roll, and multiple air wipers are installed at a predetermined angle.
Excess cooling water used for cooling the rolls can be effectively removed.

Embodiment Figures 1 to 4 show an overview of the configuration of an apparatus for carrying out this Q-light method. FIG. 3 is an explanatory diagram of an air spray nozzle for an air wiper, and FIG. 4 is an explanatory diagram of a drain plate type wiper.

In FIG. 1, cooling mist spray nozzles (2) are provided on each rolling roll (1). The mist spray nozzle (2) is connected to the cooling water supply port (
3) and a compressed air supply port (4), which sprays cooling water in a mist form using compressed air. The specifications and number of the mist spray nozzle (2) are determined by taking into account the size of the roll (1) (roll diameter, roll length), operating conditions, etc., and the installation position and angle of the mist spray nozzle (2) are determined by are arranged as shown in FIG.

The drainer of the roll (1) is composed of an air spray nozzle (5) shown in FIG. 3 and a drainer plate (6) made of heat-resistant rubber. The drain plate (6) is attached to the plate (7) near the material to be rolled (8) as shown in Fig. 4.
Before that, an air spray nozzle (5) is installed to first blow off excess cooling water adhering to the roll (1) with air in the opposite direction to the rolled material (8). Then, the water is drained using a drain plate (6). Note that (9) is a guide shoe and (10) is a plug.

Example 1 Two types of austenitic stainless steel billets, A' and B shown in Table 1, with an outer diameter of 187 mm and a length of 1520 mm were soaked at 1170°C, and then rolled with a roll diameter of 1200 mm and a roll length as explained in Fig. 1. 711.2mm
Using Mannesmann's perforation machine, 80 perforation rolls were continuously perforated and rolled at a pitch of 25 seconds by changing the method of cooling the perforation rolls.
Outer diameter 192mm, wall thickness 15.0mm, length 5000mm
It was made into a hollow tube.

In this case, the setup of the drilling machine is as follows: roll crossing angle 10 degrees, roll inclination angle 15 degrees, roll opening 165 mm, guide opening 186 mm, plug diameter 149 mm, plug lead 120 mm.
It was mm.

For cooling the rolls, three mist spray nozzles are installed on each roll, and air pressure is 4 kg/cm2 and water pressure is 5 kg/cm.
The test was carried out at an air supply rate of 17.2 Nm3/hr/piece, a water amount of 14.6 liters/min/piece, and a distance between the nozzle and the roll of 200 mm.

In addition, for draining, five air spray nozzles for draining were installed on each roll, and the air pressure was 4 kg/cm2, the air supply amount was 80 ONI, /min/nozzle, and the distance between the nozzle and the roll was 200 mm. A draining board was also used.

Then, the perforation efficiency, roll surface seizure occurrence, guide shoe seizure flaw occurrence rate, and inner and outer surface blister flaw occurrence rate were measured and evaluated. The results are shown in Table 2.

Below is a margin Example 2 A tube with an outer diameter of 10 mm made of two types of austenitic stainless steel, C and D, having the composition shown in Table 3, was tested using a thermorester tester with a tensile workability of 40% and a strain rate of 5X10-
"5ec-', test temperature 900℃, 1000℃, 11
A tensile test was carried out under the test conditions of 00°C, and the longitudinal section of the test piece after tension was observed in 10 fields using an optical microscope with a magnification of 200 times.
■The total length of micrograin boundary cracks per field of view was measured. The results are shown in FIG.

As shown in FIG. 5, in the case of Ca-added austenitic stainless steel D, almost no micrograin boundary cracks are observed.

The following margin Example 3 The outer diameter of the same component composition as the third table of Example 2 is 457, 2
A high-frequency bending test was conducted on a seamless austenitic stainless steel pipe with a wall thickness of 19.1 mm.

The test conditions were bending radius 1.5DR [685,8R], feed rate Q, 2mm/sec [strain rate = lXl
0""5ec-'], processing temperature 1050-1100
It was ℃.

Microscopic observation after bending revealed no micrograin boundary cracks.

Effects of the Invention As described above, according to the method of the invention, seamless austenitic stainless steel pipes with excellent hot workability can be stably manufactured in large quantities with few surface defects using the Mannesmann pipe manufacturing method. , the effect is great.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an apparatus for carrying out the method of the present invention, Fig. 2 is an explanatory diagram of a mist spray nozzle, and Fig. 3 is an explanatory diagram of an air spray nozzle for an air wiper.
The figure is a front view, (b) is a partially cutaway view, Figure 4 is an explanatory diagram of a drain plate type wiper, and Figure 5 is the relationship between test temperature and micro elongation for each steel type in Example 2. This is a graph showing. 1... Roll, 2... Mist spray nozzle 3... Cooling water supply port, 4... Compressed air supply port, 5...
・Air spray nozzle, 6...Draining plate, 7...Mounting plate 8...Rolled material, 9...Guide shoe〇...Plug,

Claims (1)

[Claims] 1 Component range in weight%: C: 0.5% or less, Si: 0.1 to 5.0%, Mn: 0
．． 1-5.0%, Cr: 10-50%, Ni: 3-50
%, Mo: 1.0 to 5.0%, S: 0.01% or less, P
: 0.03% or less, O: 0.03% or less, N: 0.01
~0.25%, furthermore, the content of each element satisfies the following formula (1), and the balance is Fe and unavoidable impurities. After soaking in the temperature range of ℃, perforation or stretching is performed using an inclined roll rolling mill that sprays cooling water onto the rolls from a mist nozzle and/or removes excess cooling water on the roll surface with a wiper. A method for manufacturing seamless stainless steel pipe. △[Ni]=%Ni+0.5%Mn+30(%C+%N
)+8.2-1.1(%Cr+%Mo+1.5%Si+
0.5%Nb)≧-2.0...(1) Formula 2 The component range is in weight%: C: 0.5% or less, Si: 0.1 to 5.0%, Mn: 0
．． 1-5.0%, Cr: 10-50%, Ni: 3-50
%, Mo: 1.0 to 5.0%, S: 0.01% or less, P
: 0.03% or less, O: 0.03% or less, N: 0.01
~0.25%, the content of each element satisfies the following formula (1), and 0.0010~0.3% of one or more rare earth elements, Ca, and B, and the balance is Fe and After soaking billets, blooms, and hollow tubes of austenitic stainless steel containing unavoidable impurities in a temperature range of 800 to 1,300°C, cooling water for the rolls is sprayed from a mist nozzle and/or the roll surface is heated. A method for manufacturing a seamless stainless steel pipe, which comprises perforating or stretching the pipe using an inclined roll rolling mill that removes excess cooling water using a wiper. △[Ni]=%Ni+0.5%Mn+30(%C+%N
)+8.2-1.1(%Cr+%Mo+1.5%Si+
0.5%Nb)≧−2.0...Equation (1)