FR2491095A1 - IMPROVED PROCESS FOR THE PRODUCTION OF PRACTICALLY MONOCRYSTALLINE SILICON INGOTS - Google Patents

Abstract

THE INVENTION RELATES TO AN IMPROVED PROCESS FOR PRODUCING PRACTICALLY MONOCCRYSTALLINE SILICON INGOTS BY HEATING METAL SILICON ABOVE ITS MELTING POINT IN A CRUCIBLE 10 TO MELT, THEN BY EXTRACTING THE HEAT FROM THE BOTTOM 24 OF THE CRUCIBLE WITH A HEAT EXCHANGER 20 ESTABLISHING A THERMAL CONDUCTION WITH THE BOTTOM. THE SILICON OBTAINED CAN BE USED IN PARTICULAR IN SOLAR BATTERIES.

Description

249 1095

  The present invention relates to a low roll

  transverse resistivity for electrolytic deposition.

  To date we have used, to make a roll

  having a low transverse resistivity for electrical deposition

  trolytic, some corrosion-resistant steels such as those defined in the Japanese industrial standards under the classifications "JIS-SCS14", "JIS-SUS316", etc., but these corrosion-resistant steels are insufficient in terms of strength corrosion caused by the passage of an electric current, erosion by

  acidic solutions, etc. as well as the resistance to wear.

  The surface of the roll becomes very rough so that it is necessary to grind the roll after a relatively short period, for example every week for

  we can continue to use it.

  A main objective of the invention is a roll for electrolytic deposition having a low transverse resistivity and eliminating all the defects previously

  described specific to conventional steel resistant to corrosion

  erosion such as those defined by the "JIS-SCS14", "JIS-SUS316", etc. The invention also aims at a roller for

  electrolytic deposition with low transverse resistivity

  dirty, which is not altered by the passage of electrical current

  which has a higher resistivity under the severe conditions of passage of an electric current important for the electrolytic deposition of zinc, tin, etc., and which has a high value of hardness, toughness and mechanical resistance as well as a

excellent wear resistance.

  According to the invention, a roll for electrolytic deposition having a low transverse resistivity essentially consists, in percentages by weight, of less than 0.1% of C, less than 1.5% of Si, less than 1.5 phr of Mn. , 14 to 21% Cr, 13 to 20% o Mo, less than 6% Fe, the

rest is essentially Ni.

  According to one aspect of the invention, a roll for

  electrolytic deposition with low trans-resistivity

  also contains one or more elements selected from the group consisting of less than 0.5% Al, less than 1.0% Ti, less than 1.5 GB Nb, less than 0.5% of V and less than 3 of W. Other features and advantages of the invention

  will emerge from the description which follows

  of the attached figure which illustrates a method for studying the resistance to corrosion and wear of a roll

for electrolytic deposition.

  As previously stated, the roll of this

  invention is characterized in that it consists mainly of

  mainly nickel with addition of molybdenum and chromium

  as fundamental elements in determin-

  born. Also, as will be explained in more detail below, the roll according to the invention is subjected, after being shaped, to an improved dissolving heat treatment so as to make the austenite base structure uniform in order to show resistance. to corrosion and

wear resistance.

  First of all, the reasons why in the

  the particular chemical components and

  their particular ranges will be explained.

  Nickel is chosen as the fundamental component of the roll so that the roll matrix has a softenenite structure and is stabilized. Moreover, as nickel has

  a weak tendency to ionization, its rate of dissolu-

  corrosion is low and the coating produced

  corrosion is of little importance, has great

  and has excellent passivity. Cobalt

  as an impurity in nickel can be tolerated

than 2.5% by weight.

  Molybdenum, in combination with nickel, reduces the rate of dissolution due to corrosion when its content

  increases, it increases passivity and it improves remarkably

  resistance to corrosion. This resistance to corrosion appears when the amount added rises

  above 13% by weight, but at the saturation

  corresponds to an addition greater than 20% by weight, intermetallic compounds precipitate easily and harm

resistance to corrosion.

  Chromium has a slow dissolution rate

  corrosion and forms with nickel and molybdenum a

  a passivity trice forming a stronger protective coating that confers passivity. In the present

  roll chrome has a remarkable effect when the quanti-

  The added weight exceeds 14% by weight, but when the addition exceeds 21%, saturation occurs with the formation of intermetallic compounds rendering the roll fragile and

  altering the corrosion resistance.

  Although carbon, silicon and iron are

  vitally introduced during the production of the roll,

  their contents are preferably as low as possible.

  However, as carbon, depending on its content, precipitates

  in the form of carbide and alters resistance to corrosion.

  its content is preferably less than 0.06% by weight; however, even if the carbon content reaches 0.1%

  by weight, the roller can be made satisfactory by

  putting to a complete improved dissolution heat treatment.

  However, to stabilize this excess carbon, the ad-

  of certain elements such as titanium and nickel

  bium, etc. is effective. For this titanium and niobium must satisfy the following relations relating to the carbon content: Ti> 5 x% C by weight, and Nb> 10 x 5C by weight, the respective contents of titanium and niobium being limited to the maximum below 1.0% by weight and

1.5% by weight.

  The addition of silicon, depending on the quantity, can

  intermetallic compounds, but in order to avoid

  ter alteration of the corrosion resistance, submit

  the roll to an improved dissolving heat treatment

  complete. Although the amount of silicon varies with the roll manufacturing process, less than 1.5% is required for deoxidation, melt flow, and the like.

  To avoid the precipitation of intermetallic compounds

  However, instead of silicon, other deoxidizing elements, such as aluminum, can be effectively used in a range that does not interfere with manufacture. The effective amount of aluminum is less than 0.5% by weight.

  With regard to iron, as long as its content is

  less than 70% by weight, although an alteration of the

  resistance to corrosion may appear in some

  As a measure, it has little effect on roll properties.

  Manganese has a significant effect on the properties of the roll, but it widens the range of the y-phase, stabilizing it and improving hot workability. Content

  in manganese must be less than 1.5% by weight.

  The addition of vanadium below 0.5% by weight,

  refines the grain and hardens the roll a little

  resistance to wear, but if the content rises above 0.5% by weight, an alteration occurs

corrosion resistance.

  Finally, with regard to tungsten, it improves the

  resistance to corrosion and increases the mechanical resistance

  as does molybdenum, but if its content is

  greater than 35% by weight, intermetallic compounds precipitate easily. To obtain a uniform structure,

  an improved dissolving heat treatment at a time

  - 1 2200C is needed. So the content is

  limited below 3% by weight.

  Several embodiments of the electrolytic deposition roll having a low transverse resistivity according to the invention will be described with reference to the results of experiments carried out to compare them with conventional rolls. Table 1 shows the chemical components (% by weight) of the various test rolls, Table 2 showing the results of the corrosion resistance tests and

249 1095

  to wear made with passage of an electric current through the test rollers, as well as the mechanical properties. The experiments were carried out so that, as shown schematically in the appended figure, a test roll 2 is immersed in a solution 1 comprising 30% ZnSO 4 and 3% H 2 S 4, the pH being 1, 2

  with a strip of mild steel passing over the roller of

  2 and on a brake roller 3 and a roller

  4 are arranged outside the solution 1, the steel strip 5 being moved continuously in the direction indicated by the arrow under a determined tension with an electric current passing from a lead anode to the test roller 2 with a current density of 20 A / dm. The results of the corrosion and wear resistance tests were evaluated by the longevity ratio and the

  defect formation report defined below. Rap-

  longevity port has been defined as the decrease

  the weight of the test roller expressed by the ratio

  from the weight reduction of the test roll to the decrease

  weight of the JIS-SUS316 steel test roll to

  which was assigned the value 1.0. The training report

  the number of defects such as scratches, marks, etc., formed on the surface of the test roll for mechanical reasons after one week of continuous operation, expressed as the ratio of the number of such defects. defects in the test roll to the number of defects in the JIS-SUS316 steel test roll,

assigned the value 100.

  Table 2 also presents the results of corrosion tests performed on some of the cast rolls

according to the present invention.

  Of the test rolls shown in Table 1,

  the test rolls Nos. 1 to 4, 9 and 14 to 17 according to the invention

  are those in which the levels of

  Ni, Mo and Cr have varied. Likewise, the scroll rolls

  Nos. 5 to 8 and 10 to 13 are those in which, in addition to the basic elements, Al, Ti, Nb and V have been added

  singly or in combination, AI has been added to

  the precipitation of Si, Ti or Nb-containing intermetallic compounds being added to prevent precipitation of

  carbides due to C and V being added to refine the grain.

  As shown in Table 2, in the roller according to the invention compared to the conventional steel roller

  JIS-SUS316, resistance to corrosion and wear

  The longevity ratio is 9 to 12 times higher.

  The defect formation ratio with respect to the conventional roll 1.0 is in the range of 1: 2.5 to 1/4, presumably as a result of the absence of scratching and the like on the surface of the roll whose mechanical properties are

  higher. Although the transverse resistivity of

  The test cells according to the invention are 130 mega cm -1, which is less than the 7ihp LCg value of JIS-SUS 316 steel, as a transverse resistivity up to 170 cc cm -1.

  been considered satisfactory, there is no pro-

serious blemish.

  When in Table 2 we study the rollers of

  Nos. 1 to 4, 9 and 14 to 17, the basic compositions of which

  In this way, it will be seen that the No. 4 test roll which contains chromium at a content in the middle of the range and molybdenum in an amount corresponding to the upper limit of the range, and that the test roll No. 9 which contains chromium and molybdenum at levels

  included in the middle of the corresponding ranges,

  feel excellent properties and that compared to the rou-

  water in steel JIS-SUS316, respectively

  longevity ratios of 11.5 and 12, the

  defects compared to a conventional roll.

  that having a value as low as 1/3.

  Test rolls Nos. 5 and 10, the content of which

  silicon is reduced but alumina has been added

  After the addition of titanium to stabilize the carbon, and test rollers Nos. 6 and 11, to which niohium has been added, the longevity ratios of 11.5 and 12 relative to the JIS-SUS 316 steel roller are observed. These results show that the longevity ratios of these test rollers are practically no different from those of the rollers.

  No 4 and 9 which contain the basic elements

  rate, i.e. do not exhibit the effect of adding aluminum and / or titanium and / or niobium. However, the corrosion values (in g / cm.day) of the tests

  immersing the test rollers as they have been

  immersed in a boiling solution of sulfuric acid

  than 50% and in a boiling solution of chlorinated

  20% water, show, as shown in Table 2, that test rolls Nos. 5 and 10, and 6 and 11 have properties superior to those of test rolls 4 and 9 which simply contain the basic elements , and these results show that the addition of aluminum,

  titanium or niobium alone or in combination is effective.

  in the case where a repair by welding is carried out, or that a rapid cooling treatment can not be carried out after an improved dissolution heat treatment. With regard to test rolls Nos. 7 and 12

  added vanadium, their long-term

  is 11 in relation to JIS-SUS316 steel and the ratio

  defect formation port is 1/4 relative to JIS-SUS316 steel. However, significant differences in mechanical properties can not be demonstrated

between the other test rolls.

  So we see that although the roll according to the invention

  be a roll whose basic elements are

  nickel, molybdenum and chromium, it presents a

  satisfactory corrosion resistance even when

  in highly corrosive conditions such as

  mersion in a corrosive solution with passage of

  electric power. Thus, the roller according to the present invention can be used in a corrosive solution having a pH of 0.6 to 1.8 with passage of an electric current, which are conditions under which the rolls made of JIS-SCS14 or JIS- SUS316 could never resist. The present roll has excellent corrosion resistance especially under severe conditions such as a pH of 0.6 to 1.8. Moreover, as the roller according to the invention has superior mechanical properties, it not only has sufficient wear resistance, but also a sufficiently low transverse resistivity which makes it possible to use it in practice during a period of time.

  longer period without any problem.

  The invention therefore provides a very suitable roll having a low transverse resistivity for the deposit

  electrolytic which necessarily requires these excellences

your properties.

  Finally, it will be appreciated that although the invention has been previously explained with respect to the material of the roll of the invention, it may have a shape and

  desired dimensions, the remarkable

  properties previously exposed manifesting whatever

  the shape and dimensions of the roll.

  Classification Chemical composition (% by weight) C Si Mn Cr Mo Fe Ni Ti Nb V A1 W

  Rolls JIS-SCS14 oo6! 163 154 19,13 2,34 remains -1248-

  classJIS-SUS316 0.04 0.82 1.53 17.03 2.52 remains 12.35 .. - -

  N 1 0.03 0.83 0.63 15.02 17.10 1.50 remainder - -

  N 2 0.0 0.79 0.59 16.07 18.02 1.23 remains .....

  N 3 0.03 0.68 0.62 15.97 15.03 1.63 remainder - - - - -

  N 4 0.03 0.89 0.54 17.51 19.07 1.96 remainder -

Examples I

  No. 5.a0.04 0.341 0.6917.42, 18.971.82reste 0.38 - 0.0.

  N0 6 0 | according to "NO 6" 40.360.52 17.53 419.02 1.6 remainder - 0.57 - 0.07

  Inven- N 70 0,0 821.64 17.62 19.09 2.05 remains 0.3 - -

  N0 8 0) 0 174 [tion NO 8 o.84053 0 17.46 18.q4 2.17 remains k __ _, 1. 3_

  N 9) 0.0302.49 17.46 6.5 1.63 remainder ....

  NO 10 0.04 0.2 O.68 17.53 16.491 1.54 remainder 0.321- - 0.0 -

  N 11 0.0529 o, 48 17.48 16.59l 1.96 remainder -

  N 12 0.03 0.79 053 I 17.9, $ 16,551.86! rest - - o -à -. _ INO 13 0.04 0.76 1o, 6 17.42I 16.62 1.72 remainder - 1.5

  N 14 0.03 0.91 0.57.3 13.98 1.74 remainder - - -

i 1.74 4 and

  0.030.82.53 19.02 18.10 1.59 rest - - -

  N 16 0o ,, 0o84 0.49 18.98 15.13 1.52 remainder - - -

  N_17 0.050.82 _051 120.131 16.49 2.0 remains_, - _ -,

  0.05, 0.820.51, 2.01, 13.16, 4.092.04.re.st.e. - _- 1-.

  Note 1. Test roll n 4 containing chromium at a range and molybdenum in an amount of 2. Test roll n 9 containing chromium and

  laying in the middle of the respective ranges.

  content included in the middle of the

the upper limit of the range.

molybdenum at levels corresponding to

N% c o Q Rulers trained

Table 1

Table 2

Resistance to Degree of Corrosion

  Corrosion and corrosion 2) Is mechanical properties lItusure g / cm2 / day iv tivit

Report Report Ebul- Ebul- trans-

  Classification of ion-of-formation lition Versal Resis- Resistance Alon Hardness gevity mation 5 0% x 20% j.XIcm tance of the H 2 S04 HC1 0d2 test in the water test 2 MM2 tion _____ _ _ _ _ _kg / mm2

JIS-T 1

  Rolls O-rolls ScSl4 O, 9 100 - - 74 32.2 61.3 49.7 82 conventional 1- 74., ___ JIS-sUs316 1.0 100 - - 21.7 56.3 54.2 78

NO 1 9 35 - -_ 30.5 64.5 49.2 91

N 2 10 30 - - 31.2 65.3 46.2 92

N 3 40 - 30, 63, 45.8

  Examples N 4 11.5 30 0.170 0.320 34.3 67.6 45.2 94 RO-NO 5 11.5 30 0.120 0.205 332 66.5 44.2 94

the

  according to No. 6 11.5 30 0.130 0.220 3 32.1 68.2 45.6 94 linven- N0 7 25 33.9 69.9 44.2 94 tsion N 6 N 8 11il 25 - - 34.6 69.2 43.2 95

  NO 9 12 30 0.125 0.270 31.3 65.9 47.2 2 ..

  N 10 12 30 0.100 0.165, 30.2 65.3 46.8 92

  Note: 1. In the table are the results obtained with test rollers which have undergone dissolving heat treatment with improved rapid cooling from

with a temperature of 1,150 C.

  2. The significance of the corrosions is the results obtained by immersion of the samples

  as cast in the respective solutions described above. O NO Ln

Resistance to Degree of Corrosion

  Corrosion and corrosion: 2) Resistance - Mechanical properties wear g / cm2 / day

trans-

  Ratio Ebulb-Resistance Ratio Resis- Resistance Allon- Hardness Classification of ion-of-formation lition "" cm tance tance gementity mation 50% x 20% test%

H-SO4 HC1 trac-

  water damage 2 kg / mm N 11l 12 3 0,900 0,185 T 30,5 65,2 45,2 92 Examples Ne 12 11 25 - - 31.8 67.2 47.1 92 of the wheels N 1 11 25 - - 2,5 64, 7 46,2 92 leaux N 14 9 40 - - 130 31,5 63,8 45,6 91 according to the invention 15 11 30 - - 35,2 68,2 44,8 94 tion N 161 tion NO 16 1il 4_0 - - _34,3 67,9 46,2 94 NO 17 10 25 I - T - 36,2 69,3 4o, 1 95 _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ ii _ _ _ _ _ _ _ i

Claims (2)

  1 - Roller with low transverse resistivity for electrolytic deposition, characterized in that it consists essentially, in percentages by weight, of less than 0.1% of C, of less than 1.5% of Si, less than 1.5 i to Mn, 14 to 21% Cr, 13 to 20% Mo,   less than 6% Fe, the remainder being practically nickel.   2 - Roller with low transverse resistivity for   the electrolytic deposition according to claim 1,   additionally one or more elements selected from the group   eg less than 0.5% Al, less than 1.0% Ti, less than 1.5 S of Nb, less than 0.5% of V and less than 3.0% of W.