US3724528A - Method for manufacturing of sound killed steel ingots - Google Patents

Method for manufacturing of sound killed steel ingots Download PDF

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Publication number
US3724528A
US3724528A US00035842A US3724528DA US3724528A US 3724528 A US3724528 A US 3724528A US 00035842 A US00035842 A US 00035842A US 3724528D A US3724528D A US 3724528DA US 3724528 A US3724528 A US 3724528A
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segregation
steel
ingot
solidification
percent
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US00035842A
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English (en)
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K Narita
T Mori
T Itoo
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Kobe Steel Ltd
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Kobe Steel Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/20—Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor

Definitions

  • Killed steel excels rimmed steel or semi-killed steel due to its greater degree of interior homogeneity which permits its use as a high grade structural steel or a forging steel which requires severe standards.
  • killed steel has excellent homogeneity, except for the presence of solidification shrinkage holes occurring at the upper portion of the ingot, segregation defects, resulting from a solidification segregation phenomena are often detected in the ingot. For instance, negative segregation sections may occur at the center of the bottom side of the ingot. Inverted V- shaped segregation zones may occur near the center portion of the upper half ofthe ingot and V-shaped segregation zones may occur at the center of the ingot.
  • Oxide type inclusions of relatively large size are often found in the negative segregation sections and it is these inclusions which are the frequent cause of defective steel.
  • Sulphide type inclusions of relatively large size are frequently found in the inverted V-shaped segregation zones which has the effect of deteriorating the workability and toughness of the steel.
  • Another method is the scraper method, wherein after casting the molten steel, it is solidified while stirring so that the boundary between the dendride section and the free crystal section can be defined without formation of V-shaped or inverted V- shaped regeneration.
  • a fine interior structure steel ingot can be obtained, the segregation of phosphorus, sulphur, oxygen, etc. is reduced and the mechanical properties of the central section of the steel ingot is improved.
  • Another technique is electromagnetic stirring, wherein the steel ingot is solidified in a rotating magnetic field and the inverted V-shaped segregation is removed to the center by the buoyance in the centrifugal field. The crystals are then pulverized.
  • Another method is the rotary casting method, wherein the growth of culumnar structure section is suppressed and the tesseral system zone is increased to provide a homogeneous ingot.
  • Still another method is vacuum casting wherein casting is carried out under vacuum to reduce gasses in molten steel and thereby minimize the extent of defects growing in the steel ingot, etc.
  • Another object of this invention is to reduce the quantity of negative segregation sections in killed steel.
  • Still another object of this invention is to reduce the quantity of inverted V-shaped segregation zones in killed steel ingots.
  • stirring agents include alloys, compounds or mixtures of ele' ments of Groups I-a, or II-a of the Periodic Table or zinc or the halides of an element: of Groups I-b, III-b, IV-a, IV-b, VI-a, VII-a, or VIII.
  • the molten steel stirring agent must have the following properties:
  • the boiling temperature must lie between 450" and 1,500 C. It the boiling temperature is lower than 450 C., the stirring action is too vigorous which is dangerous in practical application. If the boiling tempera-
  • the alloy as the molten steel stirring agent comprises two groups, one of which is alloys of the mutual alloys among the elemental substances mentioned above and the other is alloys containing other elements such as Cu, Al, Si, Ti, Zr, Nb, Ta, Mn, Fe, and Ni.
  • the alloy belonging to the first group may be any of the following or mixture thereof:
  • K-Na, Li-Na, K-Mg, Ca-Mg-Zn K-Mg-Na and the second group are as follows:
  • the compound as the molten steel stirring agent comprises inorganic halides, hydroxides, carbonates, bicarbonates and oxides of the La group and halides of the lb, lI-a, II-b, III-b, lV-a, IV-b, Vl-a, VII-a, and VIII Groups.
  • KCl, CsCl, NaCl, LiCl, Kl, Csl, Nal, CsBr, NaNr, LiBr, KF, CsF, CuCl, CuBr, CuBr BaCl Becl tends to form oxides to a high degree at this stage which cannot move as freely as carbon and sulphur.
  • the oxides therefore, accompany the settling ferrous crystals downward.
  • the rate of solidification from the bottom is reduced and solidification is apparently stagnant. Ferrous crystals of high purity and the oxides descend from the upper part and are accumulated in this portion.
  • the V-shaped segregation line which corresponds substantially to the shape of the solidification line is formed.
  • stirring agent in the form of an element, alloy, compoundor mixture thereof, is added to the molten steel so that the vaporization of the stirring agent will stir and homogenize the molten steel.
  • the stirring agent may be any substance containing the above-mentioned elements, for practical application, a Mg alloy contaning less than 50% Mg, Ca and the alloy thereof are desirable.
  • the stirring agent can be easily and effectively added to molten steel by attaching a suitable capsule containing the stirring agent to an iron rod, which is then inserted to the predetermined depth in the mold.
  • the amount to be added depends on the size of the steel ingot, but the use of amounts in excess of about 1% is apt to dangerously scatter molten steel. An amount of less than about 0.000196 will not exhibit a sufficient effect.
  • - preferred amount is such that when the stirring agent is added, the surface of molten steel at the feeder head section will shake'slightly. Excellent resultsare obtainable within the range of about 0.0005 to 0.02 percent.
  • the metal element inserted into the molten steel will quickly evaporate and the vapors produced will stir and homogenize the molten steel, reduce the segregation and compact the cast structure. It will also have the effect of accelerating solidification by removing evaporation heat from molten steel when the metal is vaporized. It will have the further effect of scattering the fine deoxidated products within the steel ingot through the evaporation of the metal producing numerous solidifications cores to produce a finer cast sturcture. As can be readily appreciated, therefore, the process of the present invention provides very desirable advantages.
  • the molten steel stirring agent should be added between the time slightly before the complete formation of the columnar structure of the steel ingot and the time of formation of V-shaped segregation zone is completed.
  • the stirring agent is added too soon after casting, the fluidity of molten steel will be too high and the segregation will be rather small, so that the desired effects will not be obtained. Moreover, if added too soon, the rather thin initial shell on the surface of the steel ingot can easily be broken, allowing the molten steel to exude through to form a double layer. On the other hand, if the stirring agent is added close to the complete solidification point, it will have very undesirable effects. In fact, even greater solidification shrinkage holes may be formed and segregation and rolling up of scums may actually increase.
  • the amount of the molten steel stirring agent and the number of doses depend on the kind of stirring agent used, its composition, the chemical composition of steel, the size of steel ingot, solidification time, etc., but in the ordinary ingot-making, one to five doses is sufficient for this purpose.
  • FIGS. 1, 2, and 3 are macrographs for comparison of corroded structures of steel ingots.
  • a shows a comparative example
  • b shows the example of the invention.
  • EXAMPLE 1 835C steel (C; 0.37 percent, Si:'0.32 percent, Mn: 0.65 percent, S: 0.018 percent, P: 0.013 percent, 0.0071 percent) which is melted in a basic highfrequency furnace was top-poured into 100 kg sand molds which were lined with an exothermic heat conservative. The casting temperature was l,569 C. and the pour rate wasl ton/3.0 min. Upon completion of casting, the exothermic heat conservative was added to the feeder head at the rate of Skg/t. One of the ingots cast as above was allowed to solidify as it was for comparison purposes while to the other ingot was added Fe- Si-Mg alloy containing 20% Mg, packed in-a capsule.
  • the ingot was treated three times, 9 min., 14 min., and '19 min. after casting at the rate of 200 g/t each time, by inserting the capsule through a guide into the center of the mold. Where sand molds are used for casting, the negative segregation section and the inverted V-shaped segregation zone were formed inthe steel ingot within from about min. to about 23 min. after casting.
  • FIG. 1 The macroscopic corroded structures in the longitudinal section of these steel ingots are shown in FIG. 1, wherein a shows a macrograph of the corroded structure of the steel ingot solidified without any addition. The branched dendrite zone is observed around the periphery of the steel ingot, and several stripes of the inverted V-shaped segregation lines are recognized in this zone.
  • b shows macroscopic corroded structure of the steel ingot to which was added the Fe-Si-Mg alloy during the solidification process thereof, and substantially the whole surface, except the surface layer section consists of fine tesseral system.
  • the inverted V-shaped segregation line is not recog nized.
  • the cast structure is highly dense and homogeneous.
  • Segregation Percentage ⁇ Maximum analytic value (average) in steel ingotl/Average value As evident from Table 1 above, by application of the method of the'invention, steel ingots having a lesser degree of segregation of carbon, sulphur, phosphorus, oxygen, etc. can be obtained.
  • the alloy was inserted in the form of a capsule which was atare shown in FIG. 2, wherein a shows the steel ingot which was solidified without addition of the alloy, in which the inverted V-shaped segregation lines though slight are observed in the branched dendride section, and the V-shapedsegregation lines are observed at the central section.
  • a shows the steel ingot which was solidified without addition of the alloy, in which the inverted V-shaped segregation lines though slight are observed in the branched dendride section, and the V-shapedsegregation lines are observed at the central section.
  • a tesseral system showing the negative segregation of carbon, sulphur, phosphoorus, etc. and the positive segregation of oxygen.
  • Segregation Percentage [Maximum analytic value (average) in steel ingot]/Average value
  • the steel ingot of the invention above had a smaller S30C steel (C: 0.29 percent, Si: 0.27 percent, Mn: 0.68 percent, S: 0.016 percent, P: 0.012 percent, 0: 0.0057 percent) which had been melted in a basic highfrequency furnace was top-poured into 1 ton sand molds. The pouring temperature was 1,510 C. and the pouring rate was 1 ton/1 min. 50 sec. After casting 5 kg of the exothermic heat conservative was added to the feeder head. The cast steel was in a round shape, 45 cm average diameter and 95 cm long. The feeder head weighed aBout 1.2 tons.
  • the inverted V-shaped segregation lines, V-shaped segregation lines and negative segregation section In the mascroscopic corroded structure of the steel ingot which was solidified without any metal addition was recognized the inverted V-shaped segregation lines, V-shaped segregation lines and negative segregation section. In the negative segregation section, a max- I imum size of silicate of about 350 p. was observed to exist. On the other hand, in the steel ingot to which Ca was added, the inverted V-shaped segregation lines were reduced to a minimum, the V-shaped segregation lines disappeared and the oxides present in the position corresponding to the negative segregation section were dispersed in a minute form. The maximum size thereof being about 50 u.
  • Segregation Percentage [Maximum anal tic value (average) in steel ingotl/Average alue EXAMPLE 4 S40C steel (C: 0.44 percent, Si: 0.26 percent, Mn: 0.67 percent, P: 0.009 percent, S: 0.019 percent, 0: 0.0028 percent) had been melted in a basic open hearth was bottom-poured into 4-ton metal molds. One of the steel ingots of the same surface plate was solidified per se, as a control while to the other steel ingot was treated according to the methods of this invention.
  • Fe-Si-Mg alloy containing 30% Mg was packed in a capsule which was attached to an iron rod and was inserted through a guide to the center of the mold in doses of 250g, 200g, and 150g, 15 min., 25 min., and 35 min. after casting, respectively.
  • the alloy was inserted to 15 cm above the solidifying surface at the time of the addition.
  • FIG. 3 shows the control steel ingot and b shows the steel ingot to which the methods of this invention were applied.
  • a shows the control steel ingot
  • b shows the steel ingot to which the methods of this invention were applied.
  • the inverted V-shaped segregation lines and V-shaped segregation lines are distinctly observed, whereas in the steelingot b of the invention, the inverted V-shaped segregation lines are reduced to minimum, and the V- shaped segregation lines have completely disappeared.
  • the density of thecast structure of the steel ingot is increased throughout the ingot.
  • the inverted V-shaped segregation zone and V-shaped segregation zone are reduced or eliminated, and large oxide type inclusions occurring in the negative segregations section are turned into finer form.
  • a markedly dense and more homogeneous cast structure can be obtained; also, the segregation of the component elements is reduced and the segregation condition of oxygen is notably improved.
  • the improvement comprising adding a stirring agent to the molten steel during the solidification process of the killed steel ingot at a time period between the period before the V-shaped segregation zone is formed and a after the negative segregation section and the inverted V-shaped segregation zones are formed, wherein said stirring agentis characterized by a boiling temperature of between 450,and 1,500 C., such that when introduced into the'molten steel, it will vaporize under,
  • stirring agent is selected from the Group consisting of:

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  • Mechanical Engineering (AREA)
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US00035842A 1969-05-08 1970-05-08 Method for manufacturing of sound killed steel ingots Expired - Lifetime US3724528A (en)

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US (1) US3724528A (ru)
AT (1) AT313499B (ru)
DE (1) DE2022086A1 (ru)
FR (1) FR2049090B1 (ru)
GB (1) GB1315005A (ru)
SE (1) SE357905B (ru)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113913673A (zh) * 2021-09-27 2022-01-11 武汉钢铁有限公司 一种用含镁合金控制钢中夹杂物尺寸和数量的方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1715065A3 (en) * 2005-04-20 2007-08-15 Corus Staal BV A cored-wire for injecting into a steel melt and process of treating a steel melt using said wire
CN102873282A (zh) * 2012-09-27 2013-01-16 北京科技大学 一种金属大铸锭点浇工艺

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE503905A (ru) *
US2837800A (en) * 1954-11-01 1958-06-10 Yawata Iron & Steel Co Casting of ferrous ingots
FR1352391A (fr) * 1963-03-26 1964-02-14 Reisholz Stahl & Roehrenwerk Procédé visant à éviter les défauts dans les coeurs des lingots
US3208117A (en) * 1962-03-28 1965-09-28 Reisholz Stahl & Roehrenwerk Casting method

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR443652A (fr) * 1911-11-28 1912-09-30 Goldschmidt Ag Th Procédé pour améliorer les propriétés du fer et autres métaux en lingots

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE503905A (ru) *
US2837800A (en) * 1954-11-01 1958-06-10 Yawata Iron & Steel Co Casting of ferrous ingots
US3208117A (en) * 1962-03-28 1965-09-28 Reisholz Stahl & Roehrenwerk Casting method
FR1352391A (fr) * 1963-03-26 1964-02-14 Reisholz Stahl & Roehrenwerk Procédé visant à éviter les défauts dans les coeurs des lingots

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113913673A (zh) * 2021-09-27 2022-01-11 武汉钢铁有限公司 一种用含镁合金控制钢中夹杂物尺寸和数量的方法

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FR2049090A1 (ru) 1971-03-26
SE357905B (ru) 1973-07-16
SU445186A3 (ru) 1974-09-30
FR2049090B1 (ru) 1973-07-13
AT313499B (de) 1974-02-25
DE2022086A1 (de) 1970-11-12
GB1315005A (en) 1973-04-26

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