GB2058140A - Removing oxide scale from surface of stainless steel - Google Patents
Removing oxide scale from surface of stainless steel Download PDFInfo
- Publication number
- GB2058140A GB2058140A GB8026245A GB8026245A GB2058140A GB 2058140 A GB2058140 A GB 2058140A GB 8026245 A GB8026245 A GB 8026245A GB 8026245 A GB8026245 A GB 8026245A GB 2058140 A GB2058140 A GB 2058140A
- Authority
- GB
- United Kingdom
- Prior art keywords
- rolled
- stainless steel
- wire
- solution
- sulphuric acid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 17
- 239000010935 stainless steel Substances 0.000 title claims abstract description 15
- 238000005554 pickling Methods 0.000 claims abstract description 23
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 21
- 235000011149 sulphuric acid Nutrition 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 13
- 239000001117 sulphuric acid Substances 0.000 claims abstract description 12
- 238000001816 cooling Methods 0.000 claims abstract description 5
- 238000005096 rolling process Methods 0.000 claims abstract description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 229910017604 nitric acid Inorganic materials 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 238000005406 washing Methods 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- GQPLMRYTRLFLPF-UHFFFAOYSA-N nitrous oxide Inorganic materials [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000009533 lab test Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- 230000002110 toxicologic effect Effects 0.000 description 1
- 231100000027 toxicology Toxicity 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/08—Iron or steel
- C23G1/081—Iron or steel solutions containing H2SO4
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Abstract
A method of removing the oxide scale on the surface of hot-rolled stainless steel, especially hot-rolled wire which has passed through a controlled, forced cooling directly after the final roll pair of the rolling mill. The hot-rolled, directly-cooled wire is treated for a period of about 1-120 minutes in a solution of dilute sulphuric acid with a concentration of 25-1200 g sulphuric acid per liter pickling solution. The temperature of the solution is kept at 40-100 DEG C during the course of the treatment.
Description
SPECIFICATION
Removing oxide scale from surface of stainless steel
The invention relates to a method of removing oxide scale from the surface of hot-rolled, stainless steel, which has been given a controlled, forced cooling directly after the final roll pair in the rolling mill.
In hot-rolling and subsequent annealing of stainless steel products such as rolled wire, a thin layer of metal oxides, so-called oxide scale, is formed on the surface of the rolled product. This scale must be removed before continued processing of the rolled product can be carried out.
The traditionally used method today for removing the scale is pickling by means of HF/H NO3 or by combination of HF/HNO3 and HCI.
The use of HF/HNO3 as pickling agent carries with it large environmental problems due to the nitrous gases which are formed during pickling.
Furthermore, there are also environmental problems when disposing of exhausted consumed pickling baths.
A hot-rolled stainless steel product of the type intended in the present invention, i.e. a product which has gone through a controlled, forced cooling directly after the terminal pair of rolls in the rolling mill, this cooling being done with water
and/or air, has a fine-grained structure with high
strength and high ductility. The oxide or scale on this product, e.g. rolled wire, cannot be removed solely by HF/HNO3, which is the most usual acid
mixture for removing oxide scale from stainless steel.
The oxide of the directly cooled, rolled product is namely of the character that so far it has required special treatment to enable its removal, namely (a) pickling in a reducing or oxidizing salt bath, possibly followed by pickling in an oxidizing alkali bath and final pickling in HF/HNO3 (or a combination of pickling in HF/HNO3 and HCI) or (b) pickling in HCI possibly followed by pickling in HF/H NO3, pickling in a reducing or oxidizing salt bath and final pickling in HCI.
The present invention has the object of providing a method of removing the oxide scale from the directly-cooled, stainless steel rolled product, such as rolled wire, with the help of a simpler, cheaper and more environmentally compatible chemical process.
In the method in accordance with the invention, the surprising effect has been established that the oxide scale or layer on the hot-rolled stainless steel product can be removed by treating it for a period of 1-120 minutes in a solution of diluted sulphuric acid with a concentration of 25-1200 g sulphuric acid per liter solution, the temperature of the solution being kept at 40-1 000C.
In a special embodiment in accordance with the invention, the sulphuric acid concentration is kept at 200-400 g/liter pickling liquor. Furthermore, in a special embodiment of the invention the
temperature of the pickling liquor is kept at 65--850C. In a still further embodiment of the
invention, the hot-rolled stainless steel product is
treated for a period of 10-20 minutes.
The method of removing the oxide scale on
rolled products in accordance with the invention
entirely eliminates the problem with nitrous gases
occurring in pickling with HF/HNO3, disposal of the
exhausted pickling liquor being considerably
simplified.
Apart from the environmental advantages
gained by means of the method in accordance
with the invention, by the toxicological risks being
decreased therewith, there is also gained, from the
processing point of view the advantage, inter alia,
that handling the pickling bath will be simpler as a
result of simpler analysis and metering of
additives, the disposal of removed oxide scale
being also simpier and better. The invention also
gives very large economical advantages, because
sulphuric acid is the cheapest mineral acid, and
the management and recovery of metals as iron,
chromium and nickel from the exhausted pickling
liquor are simplified, as well as purification of the
gases (sulphuric acid mist) being considerably
simplified.The method in accordance with the
invention is described more closely in the
following while referring to the accompanying
working examples of the invention and a
comparative example, the latter being outside the
scope of the invention.
The invention is based on the fact that the oxide
composition on directly-cooled rolled products,
such as rolled wire, differs from the oxide
composition of the conventionally heat-treated
wire, both with regard to the content of the metal
oxide and the thickness of the layer thereon, and
for that reason can be removed by sulphuric acid.
In laboratory tests that have been carried out to
move the oxide scale on directly-cooled rolled wire
from stainless steel of the type SIS 2332, the wire
was treated in a 2M H2SO4 solution at a
temperature of 850C for ten minutes. During this
treatment a heavy reaction in the solution with the
generation of gas could be noted. The gas thus
obtained was hydrogen gas. When the wire was taken up from the H2SO4 solution, an attack on the oxide layer could be visually observed, as well as a
change of shade. On subsequent high-pressure washing with water, the completely unexpected result was that the wire was completely liberated from the oxide scale and a metallically clean surface was obtained. The oxide layer, which remained to 90% on the wire surface after the
H2SO4 treatment, could be removed either with high-pressure washing or with ultrasonic treatment in water.The sludge which collected on the bottom on the treatment vessel could be separated after some hours, and was thus easy to remove, e.g. by decanting. A number of further experiments have been carried out with different
H2SO4 concentrations on different qualities of directly-cooled stainless steel wire with the same good results as above. Two examples of such experiments are given below, as well as a comparative example of a mode not coming within the scope of the invention.
EXAMPLE 1
100 ml of a 5M H2SO4 mixture was prepared in a 150 ml glass beaker. The mixture was heated to 750C, and a plurality of pieces of directly-cooled stainless steel rolled wire were pickled for 15 minutes. The wire qualities were SIS 2320, 2332,2340,2343 and AISI 308L.
On subsequent high-pressure washing with water, the pieces of wire were liberated from oxide (oxide scale).
EXAMPLE 2
100 mi of a 5M H2SO4 mixture was prepared in a 150 ml glass beaker. The mixture was heated to 750C and a plurality of annealed stainless steel rolled wire pieces were pickled for between 15 and 120 minutes. The wire qualities were
SIS 2320,2332,2340,2343 and AISI 308L.
On subsequent high-pressure washing with water it could be established that 90% of the oxide remained on the surface of the wire.
EXAMPLE 3
Four coils of wire, with a weight of 300 kg per coil, of directly-cooled stainless steel rolled wire with a dimension of 5.60 to 8.0 mm diameter were treated in a bath of the concentration 5M H2SO4 and volume 5000 liter at a temperature of 750C. The wire qualities were SiS 2320, 2332, 2340,2343 and AISI 308L.
After treatment for 1 5 minutes in the pickling bath and subsequent high-pressure washing with water, the coils of wire were free from oxide. A total of 200 tons of the above-mentioned qualities, which were directly-cooled, have been treated with very good results. To ascertain whether the obtained effect was selective for sulphuric acid, a plurality of experiments were
performed with different combinations of mineral acids such as hydrochloric acid, nitric acid and phosphoric acid. The same good result as for
H2SO4 by itself was not obtained with any of the experimental combinations.
A plurality of attempts to remove the oxide from different annealed stainless steels using
H2SO4 have been carried out, but the pickling results have been poor. Usually about 90% of the oxide has remained.
The practical experiments which have so far been carried out in operational conditions have given good support for there being technical possibilities of using the method in accordance with the present invention in actual production conditions.
Claims (4)
1. A method of removing the oxide scale from the surface of hot-rolled stainless steel which has passed through a controlled, forced cooling directly after the terminal pair of rolls in the rolling mill, characterized in that the rolled product is treated for a period of 1-120 minutes in a solution of dilute sulphuric acid with a concentration of 25-1200 g sulphuric acid per liter pickling liquor, the temperature of the solution being kept at 40-1 000C.
2. A method as claimed in claim 1, characterized in that the sulphuric acid concentration is kept at 200 400 g/liter pickling liquor.
3. A method as claimed in claim 1 or 2, characterized in that the temperature of the solution is kept at 65--850C.
4. A method as claimed in any one of claims 1-3, characterized in that the product is treated for a period of 5-20 minutes.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7907610A SE439025B (en) | 1979-09-13 | 1979-09-13 | SET TO REMOVE OXID LAYERS FROM THE SURFACE OF HOT ROLLED STAINLESS STEEL |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2058140A true GB2058140A (en) | 1981-04-08 |
| GB2058140B GB2058140B (en) | 1982-12-22 |
Family
ID=20338819
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8026245A Expired GB2058140B (en) | 1979-09-13 | 1980-08-12 | Removing oxide scale from surface of stainless steel |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5641012A (en) |
| BE (1) | BE885220A (en) |
| DE (1) | DE3029525A1 (en) |
| ES (1) | ES494393A0 (en) |
| FR (1) | FR2465012A1 (en) |
| GB (1) | GB2058140B (en) |
| IT (1) | IT1132666B (en) |
| NL (1) | NL8004889A (en) |
| SE (1) | SE439025B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1993023588A1 (en) * | 1992-05-18 | 1993-11-25 | Leif Inge Aanestad | A method and an apparatus for precipitation coating of internal surfaces in tanks and pipe systems |
| EP0808919A1 (en) * | 1996-05-24 | 1997-11-26 | Armco Inc. | Hydrogen peroxide pickling of stainless steel |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB385429A (en) * | 1931-12-31 | 1932-12-29 | Wiggin & Co Ltd Henry | Improvements relating to the treatment of corrosion or heat-resisting alloys to remove oxide scale therefrom |
| US2605775A (en) * | 1947-02-21 | 1952-08-05 | Superior Steel Corp | Process of teating cold rolled straight chrome type stainless steel |
| US2895856A (en) * | 1955-12-15 | 1959-07-21 | United States Steel Corp | Method of pickling chromium-containing steel tubes |
| US2981643A (en) * | 1958-02-19 | 1961-04-25 | Russell D Baybarz | Process for descaling and decontaminating metals |
-
1979
- 1979-09-13 SE SE7907610A patent/SE439025B/en not_active IP Right Cessation
-
1980
- 1980-08-04 DE DE19803029525 patent/DE3029525A1/en not_active Withdrawn
- 1980-08-12 GB GB8026245A patent/GB2058140B/en not_active Expired
- 1980-08-20 ES ES494393A patent/ES494393A0/en active Granted
- 1980-08-29 NL NL8004889A patent/NL8004889A/en not_active Application Discontinuation
- 1980-09-02 JP JP12072980A patent/JPS5641012A/en active Pending
- 1980-09-05 IT IT24478/80A patent/IT1132666B/en active
- 1980-09-12 FR FR8019698A patent/FR2465012A1/en active Pending
- 1980-09-12 BE BE0/202093A patent/BE885220A/en not_active IP Right Cessation
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1993023588A1 (en) * | 1992-05-18 | 1993-11-25 | Leif Inge Aanestad | A method and an apparatus for precipitation coating of internal surfaces in tanks and pipe systems |
| US5545433A (en) * | 1992-05-18 | 1996-08-13 | Aanestad Leif Inge | Method for precipitation coating of internal surfaces in tanks and pipe systems |
| EP0808919A1 (en) * | 1996-05-24 | 1997-11-26 | Armco Inc. | Hydrogen peroxide pickling of stainless steel |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3029525A1 (en) | 1981-04-02 |
| BE885220A (en) | 1981-03-12 |
| NL8004889A (en) | 1981-03-17 |
| SE439025B (en) | 1985-05-28 |
| GB2058140B (en) | 1982-12-22 |
| IT1132666B (en) | 1986-07-02 |
| ES8202065A1 (en) | 1982-02-01 |
| JPS5641012A (en) | 1981-04-17 |
| IT8024478A0 (en) | 1980-09-05 |
| ES494393A0 (en) | 1982-02-01 |
| SE7907610L (en) | 1981-03-14 |
| FR2465012A1 (en) | 1981-03-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |