DE3235444A1 - Process for the production of a cleaned cold-rolled steel strip - Google Patents

Abstract

Process for the production of a cleaned cold-rolled steel strip, in which a low-concentration lubricant emulsion for the roll train is sprayed at high pressure onto both sides of the steel strip at the last roll stand 5 of the roll train, oil and metal dust thereby being removed from the strip surface (Fig. 1). <IMAGE>

Description

Process for making a cleaned cold rolled

Steel strip The invention relates to a method of production of a cleaned cold-rolled steel strip.

Cold rolling mill lubricants, such as mineral oil, beef tallow, synthetic oils or the like. Used, in order to achieve cooling and wrapping of the rollers. On the surface of one Remains of the cold rolling mill lubricant adhere to the strip after cold rolling was used in cold rolling. In addition, metal dust adheres to the surface, generated by abrasion during the rolling process. If the tape wrap is not If the remnants are afflicted by annealing, these residues carbonize and adhere on the surface of the tape as surface striations, the surface being a anniint considerably dirty appearance, thereby reducing the economic value and the protection and resistance to corrosion is significantly impaired.

As a result, there is always a high level of surface purity it is necessary to clean the surface of the hot-rolled strip and to Glowing through a cleaning line The use of water calls however, surface defects such as rust and water stain or stains emerge, so that the action of the rolling stand has an adverse effect on the rolling action lowered, objects rolling difficult and a large amount of dust that leads to contamination is generated.

Furthermore, the use of a cleaning agent is costly in comparison on the effects that will be achieved. There are also additional Difficulties in that a decrease in the mill stand lubricant is not possible and care must be taken for the disposal of waste water.

(2) Detergent spray method at high pressure In this method will apply a high pressure, high temperature cleaning agent to the belt surface sprayed on in the final rolling process. A typical example of this procedure is described as "Clean Cold Rolling Method" in Japanese Patent Publication No. 19682/80. With this method, there is an improvement in the cleaning effect achieved; in doing so, however, rust, which is caused by, is accepted the water and / or the detergent.

In addition, the lubricating properties are reduced. this I sent it through. Such a cleaning line, however, requires an additional expenditure of energy, for example in the form of electricity and steam, detergents, such as for example Alkalis, brushes with heavy wear and tear, and workload. This increases the total manufacturing cost.

In the case of cold rolling or annealing, various methods have so far been used Cleaning the surface of the belt without using a cleaning line for application came. However, none of these methods is satisfactory in terms of effort and expense the cleaning effect.

The following are some of such processes which are used in cold rolling used to clean the belt surface are described: (1) Detergent Process ei this method is water or a cleaning agent 2 at a pressure of 10 kg / cm or lower on the surface of the strip on the last roll stand or sprayed on during the last rolling pass, so that the strip surface of oil and metal dust is released.

leads to the generation of metal dust through abrasion. It surrender from this, difficulties after annealing resulting from contamination.

(3) Roll cleaning method In this method, a roll lubricant emulsion becomes used for cooling and tuning the rollers, evaporation during the glowing process or volatilization of the lubricant takes place. In this process I want one prevents the lubricant remaining on the strip during the annealing charred. Therefore efforts are made to decompose and evaporate the lubricant. However, the cleaning effect achieved is low. Plus you take one Reduction of the lubricant property in purchase because it is difficult to obtain one Roll mill lubricant emulsion to achieve both good lubricating properties as well as having a high evaporation capacity during annealing.

The object of the invention is therefore to provide a method for economical and easy production of a cold-rolled and cleaned steel strip by spraying a rolling mill scimper under high pressure at which one Cleaning effect is achieved, which is the same as a conventional cleaning line, without using such a road will.

This object is achieved by the features of claim 1, wherein Advantageous developments of the invention are specified in the subclaims.

The following table 1 shows results obtained in practice in a rolling train. Concentration of the amount of the Ooer amount of the evaluation Rolling mill lubrication surface contamination - residual coal Middle emulsion (%) tongues according to the lenstoffes purity Cold rolling (measured 2 (mO / cm) after the Ford process ren) (mg / cm2) 0.2 ISQ 11.0 bad 0.5 50 5.0 | Well 0.7 60 5.1 | Well 1.8 70 5.3 good 2O 80 5.3 good 2.5 200 12.5 strokes Table 1 above shows that when a scimper of a concentration less than 0.5% is used, various problems such as the use of water such as rust, water stains and a decrease in lubricant effect arise. As a result of the metal dust generated by increased abrasion, impurities arise on the surface of the metal strip after annealing. On the other hand, if a lubricant emulsion having a concentration higher than 2% is used, the amount of impurities adhering to the tape surface increases.

As can be seen from the foregoing, the various difficulties which are caused in the cleaning method using water or can be dissolved using a cleaning agent by spraying a Roll lubricant emulsion at a concentration of 0.5 to 2% at high pressure onto the surface of the strip at the entrance or exit of the last roll stand. In addition, an alkali lubricant emulsion of the same composition with little Pressure sprayed on the rollers as a lubricant.

ei the cleaning agent spraying process described in the introduction an oil separator must be used with high pressure, around the detergent to make repeatedly usable. however, in the method according to the present invention becomes a roller lubricant emulsion with a low concentration of .0.5 to 2 % is used, which does not require the use of an oil separator. It all that is necessary is the concentration of the lubricant emulsion in the area to hold from 0.5 to 2%.

The lubricant emulsion is preferably used at one pressure in 2 one Sprayed range from 50 to 200 kg / cm. When the 2 pressure is less than 50 kgXcm is dimensioned, the cleaning effect is low and if on the other hand the pressure If it exceeds 200 kg / cm2, the cleaning effect is saturated.

The flow rate when spraying the lubricant emulsion is preferably in the range from 20 to 150 1 / min per 100 mm per 100 mm width a surface side of the steel belt. Is the flow velocity below 20 1 / min, the cleaning effect is poor. Exceeds the flow rate 150 l / min, there is a saturation of the cleaning effect, and the drain of the Water becomes extremely weak With the help of the enclosed figures the invention explained in more detail. It shows: FIG. 1 schematically the structure of a KaltwalzstralSe to achieve a cold-rolled strip lap, in which the Method according to the invention for application korsnt and FIG. 2 shows a similar representation as in Fig. 1, showing a part of the cold rolling mill which is somewhat modified is.

In Fig. 1 is a method for making a purified cold-rolled tape roll shown. Fig. L shows schematically the structure of a continuously operating cold rolling mill with five four-roll stands. In this Rolling train comes a rolling train lubricant emulsion with a relatively high concentration from 3 to 5% for application. This lubricant emulsion is made up of a first Tank 3 delivered to the first four roll stands 1, 2. The lubricant emulsion used from this \ Valzgerüst is collected by means of a collecting trough 4 and in the first Tank 3 collected for reuse.

In the last roll stand or fifth roll stand 5, the rolls are one Lubricant emulsion of low concentration from 0.5 to 2% from a second Tank 6 via a low pressure pump 7 and a spray nozzle S supplied. Also will the lubricant emulsion from the second tank 6 at high pressure on both sides of the strip 11 is sprayed on via a high pressure pump <) 3 and a spray nozzle 10. The spray nozzle 10 can at the entrance (Fig. 1) and / or exit (Fig. 2) of the fifth respectively.

last roll stand 5 be provided. The spray nozzle is preferred 10, however, provided on the entry side of the last roll stand. The used Lubricant emulsion is collected in one collecting trough 12 and in the second Tank 6 collected for reuse.

The cold rolling was carried out under the following conditions: Dimensions of the starting material: 2.5 mn thickness x 1200 mn width Dimensions of the finished product Materials: 0, S in thickness x 1200 mm in width Cold rolling (1) reduction 8% (on the fifth roll stand) (2) Rolling speed 1500 m / min (on the fifth roll stand) (3) first to fourth mill stands bright machined rolls are used; one A mineral lubricant emulsion of 3% concentration is used.

(4) fifth stand nated rolls are used; a mineral lubricant emulsion of 0.8 o concentration is used.

(5) Low pressure spraying on the fifth roll stand (to lubricate the Rollers) 2 pressure: 10 kg / cm o temperature: 50 ° C. flow rate: 4000 1 / min (6) High pressure spraying on the fifth roll stand (to clean the strip surface) 2 Pressure: 100 kg / cm o Temperature: 50 C Flow rate: 50 1 / min (100 mm width on one side) Spray nozzle: sector nozzle o spray angle 30 o rotation angle 30 Tilt angle of the nozzle: 600 in relation to the direction of movement of the belt Distance between the spray jets: 390 mm batch annealing: N, H - gas atmosphere at 670 ° C; 2 2 15 hours.

Result The amount of contaminants including @@ and metal dust, adhering to the surface of the strip after cold rolling 2 is 50 mg / m 2 . After the wrap of sand has been annealed, a filter paper wipe test shows that the tape is is significantly cleaner than belts that have passed through a conventional electrolytic cleaning line were sent. An experiment based on the Ford process shows that the proportion of carbon which remains on the belt surface is sufficiently small, i.e. H. only 5 mg / m2. The end product is free of rust and water stains.

The tape has been subjected to chemical treatment and chemical coating process a corrosion resistance in the same quality as tapes, which by an electrolytic Cleaning route were sent through.

According to the invention, the percentage of cold rolled Conventional tapes that have to run through the cleaning line are opposite Process can be reduced by about 10%. In this way there is an energy saving and reducing the effort. In addition, the yield of the finished product can be around 0.2% can be increased by improving the surface quality according to the invention.

Claims (4)

SUMITOMO METAL INDUSTRIES, LTD. 15, 5-chome, Kitahama, Higashi-ku, Osaka-shi, Osaka, Japan NIHON PARKERIZING CO., LTD. 15-1, Nihonbashi 1-chome, Chuo-ku, Tokyo, Japan Method of manufacture of a cleaned cold-rolled steel strip Patent claims: 1. Method of production of a cleaned cold-rolled steel strip, d u r c h e k e n n n z e i c h n e t that a rolling mill lubricant emulsion of low concentration on both The surface of the sand on the last stand of the rolling mill is sprayed with high pressure so that contaminants such as oil or metal dust are removed from the belt surface and that the concentration of the lubricant emulsion set is to 0.5 to 2%, the pressure when spraying on 2 to 50 to 200 kg / cm and the Lubricant emulsion flow rate when spraying to 20 to 150 1 / min per 100 mm width can be set on one side of the hinge. 2. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that on the entry side of the last rolling frame of the cold rolling mill the Rolling mill lubricant emulsion of low concentration with high pressure on both sides is sprayed onto the steel belt. 3. The method of claim 1, d a d u r c h g e k e n n -z e i c h n e t that the rolling mill lubricant emulsion of low concentration with high Pressure on both sides on the exit side of the last stand of the cold rolling mill is sprayed onto the steel belt. 4. The method according to claim 1, d a d u r c h g e 1 <e n n n z e i c h n e t that as work rolls for the last roll stand of the cold rolling mill Inatted Valzen can be used.