DE19652335C1 - Seamless corrosion resistant steel bottle production used for storing high purity or corrosive gas or liquid - Google Patents

Abstract

Producing seamless corrosion resistant steel gas bottles, for use in contact with high purity and/or corrosive gases and/or liquids, involves the composition (by wt.) 0.02-0.06% C, 0.15-0.30% Si, 1.60-1.80% Mn, \}0.035% P, \}0.008% S, \}0.020% Al, 12.5-13.5% Cr, 0.3-0.8% Ni, \}0.07% V, 0.025-0.060% Nb, >= 0.03% W, \}0.01% Ti, 0.010-0.035% N, balance Fe and impurities, where the sum of C + N is \}0.07% and the sum of V + Ti is \}0.07%. A first process involves (a) hot extruding a bottle preform from a steel ingot; (b) soft annealing the preform at 650-750 deg C; (c) cold extruding at room temperature to the desired final wall thickness; (d) roll forming a bottle neck at 1150-1250 deg C; (e) hardening and tempering; and (f) descaling the steel bottle interior and exterior. Also claimed is are (I) second process involves (a') deep drawing a soft annealed blank of hot rolled steel sheet to form a bottle sleeve; and (b') carrying out the above steps (d), (e) and (f), and (II) third process involves (a") subjecting a seamless steel tube to end spinning or forging to form the bottom or bottle neck; and (b") carrying out the above steps (e) and (f).

Description

The invention relates to a method for producing seamless corrosion-resistant gas cylinders or containers made of steel, which in their further Use with corrosive gases and / or liquids in contact.

For many industrial or commercial applications gases are needed which stored in compressed or liquefied form in bottles or containers are. These gases also include hydrogen-containing gases down to pure Hydrogen. For example, in the electronics industry hydrogen is used with the highest Purity required. This results in high demands on the for the Used in bottles or containers. Possible particle secretions of The inner surfaces of the bottles often have to be reduced to extremely low values become. In addition, in the presence of an aqueous phase are occasionally strongly corrosive conditions that do not lead to corrosion on the material allowed to lead.

Increasing volume with more corrosive gases and high purity gases has increased dramatically in the gas industry in recent years. At the same time the requirements for the product compressed gas cylinder or pressure vessel with regard to Lifetime, safety and inert behavior towards the gas to be stored increased significantly. It is to be expected that the proportion of such products with increased requirement profile in the gas industry will continue to grow.

So far, such problematic gases have been welded in austenitic Stored stainless steel bottles. For the production of electronic chips, the Storage of hydrogen z. B. in stainless steel bottles made of the material 1.4301  or 1.4571. Such steel bottles made of austenitic materials However, they have found relatively little acceptance. The reasons are to be seen in particular in the extremely high production costs, about the Factor 10 over the corresponding manufacturing costs when using Carbon tempering steels lie, as well as in the considerably higher Bottle weight, which is an inevitable consequence of balancing the lesser Material strength required reinforcement of the wall thickness is. It therefore exists already for several years the desire for a better, d. H. technically satisfactory and more economical solution for storing aggressive and / or high purity gases. The on the material for such bottles or containers The following requirements can be cited as follows:

• - good forgeability
• - Yield strength of at least 690 MPa
• - adequate cold and hot workability properties
• - good corrosion resistance
• - Electropolability to ensure particle freedom

The well-known martensitic steel X 20 Cr 13 (material no. 1.4021) lies with a Chromium content of 13% close to the resistance limit, d. H. close to the theoretical Minimum content of chromium to form the passivity. This is considered stainless Steel is resistant to corrosion and would be suitable for the production of compressed gas cylinders sufficiently strong. But about the known production ways of Compressed gas cylinder production, such as the production of the pipe by Deep drawing from a blank or by hot extrusion from a block can be do not process this material. Therefore, so far only the already mentioned welded austenitic stainless steel bottles used. Furthermore, it should be noted that the material X 20 Cr 13 for the intended applications by no means a has sufficient corrosion resistance.

From WO 93/11270 is a weldable high-strength structural steel for the production of seamless steel tubes or flat products for pipes or containers known at their further use with gaseous or liquid hydrocarbons in Contact, the CO₂ and water and possibly contain small amounts of H₂S. In this case, the articles produced from this steel have a 0.2-proof strength of at least 450 N / mm². This steel has the following composition:

C 0.015% to 0.035% Si 0.15% to 0.50% Mn 1.0% to 2.0% P Max. 0.020% S Max. 0.003% Cr 12.0% to 13.8% Ni <0% to 0.25% Mo 0.01% to 1.2% N 0.002% to 0.02% Nb 0.01% to 0.05% rest Iron and usual impurities

Compared to the standard steel X 20 Cr 13 has the well-known from WO 93/11270 Mild steel significantly better toughness properties as well as a significantly improved Resistance to erosive corrosion. The strength properties of this However, steel is not sufficient for use as a bottle material.

The standard bottle material 34 CrMo 4 has a minimum yield strength of 755 MPa and a minimum tensile strength of 850 MPa. The notched impact strength at a test temperature of - 50 ° C must be at least 50 joules / cm² (Mean test direction transverse).

The object of the present invention is to provide a process for the preparation of To propose steel bottles or containers which, when used with them, should continue to be used corrosive gases and / or liquids in contact and thereby are corrosion resistant and / or are suitable for storing high purity gases. The weight of these bottles or containers should be compared to the known Stainless steel versions be significantly lower. Likewise, the production should be less be expensive. It should be a sufficient level of strength and Toughness requirements to be ensured.

The invention solves this problem in three different variants, which in the Claims 1 to 3 are characterized in detail and by the features of  Dependent claims 4 to 12 are further ausgestaltetbar in an advantageous manner. this will explained in more detail below.

In a first variant, the inventive method provides for the production of seamless corrosion-resistant steel bottles, which in their further use come into contact with high-purity and / or corrosive gases and / or liquids, hot extrusion of a heated steel block to a bottle blank. The starting material is a steel alloy with the following composition used (in% by weight):

C 0.02% to 0.06% Si 0.15% to 0.30% Mn 1.60% to 1.80% P Max. 0.035% S Max. 0.008% al Max. 0.020% Cr 12.5% to 13.5% Ni 0.3% to 0.8% V Max. 0.07% Nb 0.025% to 0.060% W minute 0.03% Ti Max. 0.01% N 0.010% to 0.035% rest Iron and usual impurities,

where the sum of C and N is max. 0.07% and the sum of V and Ti Max. 0.07% is limited. The bottle blank thus produced is then at annealed at least 650 ° C and not more than 700 ° C. By subsequently it Cold extrusion at room temperature will produce the desired final thickness Bottle wall generated. After heating is then at a temperature of 1150 to 1250 ° C by rolling a bottle neck formed. After these individual Forming steps is then used to adjust the strength and Toughness properties performed a tempering treatment. Subsequently The steel bottle thus produced is descaled inside and out.  

In a second variant, the invention provides the production of seamless stainless steel cylinders by deep drawing before, in turn, the already mentioned material is used as a starting material. The starting material consists of annealed blanks from a hot-rolled sheet. These rounds will be formed by deep drawing to a bottle sleeve. After a warming will then a bottleneck formed at 1150 to 1250 ° C by rolling. After that a tempering treatment and a final descaling of the interior and Outer surface.

In a third variant of the process according to the invention, the production of Steel cylinders and containers for storing high purity and / or corrosive gases and / or liquids provided by a hot forming process, in which as Starting material seamless steel tubes with the aforementioned alloy composition be used. After heating a corresponding steel tube to 1150 up to 1250 ° C, the two tube ends by the so-called. Spinning method or a forging process to soils or a bottleneck formed. Subsequently, a tempering treatment for adjusting the strength and Toughness properties and a descaling of the inner and outer surface.

Surprisingly, the inventively used for the starting material covers Material not only the required strength spectrum (minimum yield strength of 690 MPa) with the greatest possible production reliability, but at the same time delivers towards the known materials with 13% Cr improved toughness properties and a improved corrosion resistance. This is achieved without the Significantly increase the manufacturing costs of the alloy. The purpose Measures are to be seen in particular in the following points:

The manganese content has been adjusted to the narrow range of 1.6 to 1.8%, while the nickel content was raised slightly to a value in the range 0.3% to 0.8%, preferably 0.4 to 0.6%. This will set the ferrite-martensite ratio reached to a very favorable value. In addition, results This increases the basic strength. By raising the Minimum content of niobium to 0.025%, the fine grain of the structure is improved in view of achieving higher strengths and improved toughness values. At the same time niobium also has a stabilizing effect with regard to achieving a  improved corrosion resistance. In this regard, in particular on the Alloying tungsten, already in very small quantities from 0.03% acts as a strong carbide stabilizer and corrosion resistance improved. The tungsten content should not exceed 1.0%, preferably 0.6%. Conveniently, the tungsten content is at least 0.1%, preferably at at least 0.15%. The addition of molybdenum was completely eliminated but low levels of molybdenum are not annoying. Furthermore, it is too mention that the content of vanadium to a maximum of 0.07% and titanium to a maximum 0.01%, the sum of both elements being at most 0.07% may be. It is recommended that the vanadium content because of its embrittling To limit the effect even more, preferably to a maximum of 0.03%. In terms of on the heat treatment of the bottles and containers according to the invention it is recommended to heat to 850-980 ° C for hardening and then cool the bottles or containers in air or in oil or Deter water. The tempering treatment after curing should be at 550 to 700 ° C take place. The appropriate height of the temperature depends on the desired properties. The higher the tempering temperature, the better Toughness properties. Lower tempering temperatures can be higher Set strength values. Very good toughness properties result itself when between tempering and tempering in the temperature range between Ac1 and Ac3 an intermediate annealing with subsequent cooling to below 100 ° C. he follows. The bottles or containers according to the invention can be very good electropolishing, so that the requirements for particle freedom to Storage of high purity gases can be easily met.

Reference to the following embodiments, the invention is explained in more detail:
Compressed gas cylinders were produced via the three variants of the method according to the invention, namely by hot extrusion from a steel block, by deep drawing from a sheet metal blank and by hot shaping of the ends of steel tubes by the spinning process. In each case, a steel having the following alloy composition (% by weight) was used in each case:

C | 0.041% Si 0.199% Mn 1.68%   P 0.012% S 0.005% al 0.003% Cr 13.1% Ni 0.52% V 0.03% Ti 0.005% Nb 0.048% W 0.04% N 0.0162%

a) reverse hot extrusion

There were compressed gas cylinders with 204 mm diameter and 4.7 mm wall thickness manufactured with integral floor. Processing took place via the use of forged tube round with a diameter of 175 mm. The Block sections were inductively heated to about 1200 ° C and then by three-stage extrusion (pre-pressing, increasing extrusion, Calibrating presses) formed. This was followed by soft annealing at 700 ° C after which, after cooling to room temperature, the final wall thickness was produced by forming after the cold flow molding process. Subsequently, the bottleneck after heating at a Temperature of about 1200 ° C formed by rollers. The so produced Bottles were then tempered in such a way that after annealing about 10 Minutes at 880 ° C a quench in water was made and finally annealed for 50 minutes at 590 ° C and finally in air was cooled. Thereafter, the bottles had the following mechanical Properties on (mean values):

Yield strength R _ea | 780 MPa Tensile strength R _m 878 MPa Elongation at break A₅ 10% Notched impact strength K _v (-50 ° C) 80J / cm²

The outer surfaces of the bottles were perfect, the bottoms well pressed and the inner surfaces smooth.  

b) deep drawing from the sheet

There were compressed gas cylinders of 204 mm diameter and 4.7 mm wall thickness made with concave bottom. Soft annealed sheet metal blanks were used a wall thickness of 7 mm. The steel bottles were cold (at Room temperature) by deep drawing by the Fielding method. After performing the forming steps, the following tempering treatment was performed carried out:

10 minutes 840 ° C / water + 50 minutes 590 ° C / air

Thereafter, the steel bottles had the following mechanical properties (Mean values):

Yield strength R _ea | 740 MPa Tensile strength R _m 835 MPa Elongation at break A₅ 20.5% Notched impact strength K _v (-50 ° C) 84 J / cm²

The outer surfaces of the steel bottles were without defects, the floors crack-free pressed out and the inner surfaces smooth.

c) molding of pipe ends by spinning

It was compressed gas cylinders with 229 mm diameter and 5.7 mm wall thickness made with concave bottom. The raw material was seamless steel tubes used, which had been produced on a plug street. The molding the pipe ends by the spinning process took place at a temperature of about 1190 ° C instead. The following compensation treatment was applied:

10 minutes 840 ° C / water + 50 minutes 590 ° C / air

The compressed gas cylinders then had the following mechanical Properties (averages) on:

Yield strength R _ea | 746 MPa Tensile strength R _m 836 MPa   Elongation at break A₅ 20% Notched impact strength K _v (-50 ° C) 83 J / cm²

The outer and inner surfaces of the steel bottles were faultless, the floors well expressed.

The experiments carried out clearly show that according to the invention Method used steel both hot-flow and Kaltfließdrückbar and thermoformable and warminformbar is. The targeted by the heat treatment Adjustable strength values were completely sufficient to with compressed gas cylinders To be able to interpret wall thicknesses that are comparable to those from the Heat-treated steel 34 CrMo 4 can be produced. Therefore, the Steel bottles and containers according to the invention both in weight as also comparable in handling with the known steel bottles. With the The present invention is the first time the production of steel bottles for the Storage of corrosive and / or high purity gases possible, not only decided are less expensive to produce, but also very significant Weight and handling advantages over the previously used Have stainless steel bottles.

Claims (12)

1. A process for the production of seamless corrosion-resistant steel gas cylinders, which in their further use come into contact with high-purity and / or corrosive gases and / or liquids, characterized

• in that a bottle blank is produced by hot extrusion of a heated steel block, using as starting material a steel alloy having the following composition (% by weight): C 0.02% to 0.06% Si 0.15% to 0.30% Mn 1.60% to 1.80% P Max. 0.035% S Max. 0.008% al Max. 0.020% Cr 12.5% to 13.5% Ni 0.3% to 0.8% V Max. 0.07% Nb 0.025% to 0.060% W minute 0.03% Ti Max. 0.01% N 0.010% to 0.035% rest Iron and usual impurities, where the sum of C and N is max. 0.07% and the sum of V and Ti to max. 0.07% is limited;
• - that the bottle blank is then annealed at not less than 650 ° C and not more than 750 ° C,
• - That then takes place at room temperature cold extrusion to the desired end wall thickness,
• - That then after heating at a temperature of 1150 to 1250 ° C by rolling a bottle neck is formed,
• - that then a compensation treatment is carried out and
• - Finally, the steel bottle is descaled inside and out.

2. A process for the production of seamless corrosion-resistant steel gas cylinders, which in their further use come into contact with highly pure and / or corrosive gases and / or liquids, characterized

• - That is used as the starting material in each case a soft annealed blank from a hot rolled sheet, the sheet following. Alloy composition (wt .-%) comprises: C 0.02% to 0.06% Si 0.15% to 0.30% Mn 1.60% to 1.80% P Max. 0.035% S Max. 0.008% al Max. 0.020% Cr 12.5% to 13.5% Ni 0.3% to 0.8% V Max. 0.07% Nb 0.025% to 0.060% W minute 0.03% Ti Max. 0.01% N 0.010% to 0.035% rest Iron and usual impurities, where the sum of C and N is max. 0.07% and the sum of V and T to max. 0.07% is limited;
• - That the blank is formed by deep drawing to a bottle sleeve,
• - That then after heating at a temperature of 1150 to 1250 ° C by rolling a bottle neck is formed,
• - that then a compensation treatment is carried out and
• - Finally, the steel bottle is descaled inside and out.

3. A process for producing seamless corrosion-resistant gas cylinders or containers made of steel, which in their further use come into contact with high-purity and / or corrosive gases and / or liquids, characterized

• - that a seamless steel tube with the following alloy composition (% by weight) is used as the starting material: C 0.02% to 0.06% Si 0.15% to 0.30% Mn 1.60% to 1.80% P Max. 0.035% S Max. 0.008% al Max. 0.020% Cr 12.5% to 13.5% Ni 0.3% to 0.8% V Max. 0.07% Nb 0.025% to 0.060% W minute 0.03% Ti Max. 0.01% N 0.010% to 0.035% rest Iron and usual impurities, where the sum of C and N is max. 0.07% and the sum of V and Ti to max. 0.07% is limited;
• - That after heating the steel tube used to 1150 to 1250 ° C, the two pipe ends are formed by the spinning process or a forging process to soils or a bottleneck,
• - that then a compensation treatment is carried out and
• - that the steel bottle or container is finally descaled inside and out.

4. The method according to any one of claims 1 to 3, characterized, that the V content to max. 0.03% is limited. 5. The method according to any one of claims 1 to 4, characterized, that the V content is at least 0.10%.   6. The method according to any one of claims 1 to 4, characterized, that the W content is at least 0.15%. 7. The method according to any one of claims 1 to 6, characterized, that the W content max. 1.0%. 8. The method according to any one of claims 1 to 6, characterized, that the W content max. 0.60%. 9. The method according to any one of claims 1 to 8, characterized, that the bottles or containers to a hardening temperature of 850 to 980 ° C. heated and then cooled in air or in oil or water be deterred. 10. The method according to claim 9, characterized, that after hardening a tempering treatment at 550 to 700 ° C takes place. 11. The method according to claim 10, characterized, that between hardening and tempering at a temperature between Ac1 and Ac3 an intermediate annealing followed by cooling to below 100 ° C takes place. 12. The method according to any one of claims 1 to 11, characterized, that the inner surface of the steel bottle or container is electropolished.