CN100450651C - Method for producing cogging by air-valve steel rolling - Google Patents

Abstract

The present invention discloses a production method of valve steel billet. It is characterized by that said production method adopts a hot-working cogging process of 'using continuous heating furnace to heat steel ingot and utilizing rolling mill to roll in one heat'.

Description

The production method of cogging by air-valve steel rolling

Technical field

The present invention relates to the preparation field of austenite or martensite type refractory steel, be particularly useful for the production method of internal combustion engine inlet and outlet valve with heat resisting steel.

Background technology

The air valve steel profile is meant the bar of surface through polishing or tumbling processing, is to be mainly used in the critical material of making gasoline, Diesel engine inlet and outlet valve.At present, Chang Yong air valve steel mainly contains 5Cr21Mn9N14N (being called for short 21-4N), 3Cr20Ni11Mo2PB (being called for short the PB steel) and 4Cr14Ni14W2Mo Austenitic air valve steel and martensite type air valve steel such as 4Cr9Si2 and 4Cr10Si2Mo such as (being called for short two 14).Because the air valve steel is operated in high temperature, high pressure, height washes away and harsh conditions such as high abrasion under, so have higher mechanical properties and decay resistance.Also just because of in this, series of features such as the air valve steel has intensity height under the room temperature, plasticity is low, fragility is big, cold deformation is difficult, work hardening is obvious, crack sensitivity is strong makes that the production and processing of air valve steel profile is very difficult.

At present,------process route of polishing or hot finishing---peeling---tumbling aligning is produced the air valve steel profile to aligning in the external hot finishing of employing usually.Certainly, this all is to be based upon on the basis of advanced tooling device and technology.It is domestic because rolling tooling device falls behind and technology falls behind, the dimensional tolerance of stocking is big, ovality is big, surface quality is poor, directly aligning polishing or peeling tumbling are aligned, only after rolling, increase cold-drawing process one, make the dimensional tolerance, ovality, surface quality etc. of stocking be able to the directly requirement of polishing.In addition, the general speed of domestic present milling train is slower, and steel billet is after repeatedly rolling, and blank cools off, and can not continue rollingly again, therefore produces the air valve steel profile, and cold-drawing process also has one its external diameter is reduced, and meets the requirements of effect.Because the air valve steel has aforementioned essential characteristic, cold drawn passage draft is not more than 15% usually, as surpassing 15%, then may cause a series of problems such as cold drawn material surface cracks, breaks, mould cracking.Yet, both made with 15% passage draft cold drawnly, also need the cold drawn of multi-pass, and each passage cold drawn after, all need processing such as annealed, pickling, alkali cleaning, not only increased production cost, and greatly reduce finished product rate, and influenced the internal soundness of steel.

At present, the traditional processing technology of " smelting ingot casting---forging and pressing cogging " is adopted in the production of air valve steel basically; The metallurgical ingot casting of≤200Kg (mainly being to solve the carbide problem of non-uniform and the consideration done) through 2-3 the forging that fire is inferior, just can be finished the hot-working cogging of 135 side mm, 55 side mm specifications, and the production cycle is long, cost is high.

Summary of the invention

The present invention develops a kind of production method of cogging by air-valve steel rolling, replace forging press to carry out the hot-working cogging with milling train, roll out qualified air valve steel steel billet, solved the problem that the air valve steel production cycle is long, the metal billet yield is low, reduce the metallurgical production cost of making greatly, satisfy customer requirements and market demand.

The production method of cogging by air-valve steel rolling provided by the invention adopts the hot-working cogging technics of " continuous furnace heats steel ingot+milling train heating once and rolling ", produces air valve steel steel billet:

(1), hot-working big mill heating once and rolling requires: (A) continuous furnace heating steel ingot, steel ingot weight 30-60Kg; (B) steel ingot enters the preheating zone, and charging temperature≤300 ℃ are incubated 100-150 minute; (C) jacking up steel machine is pushed steel ingot to middle warm area, and temperature is 700-900 ℃, is incubated 20-40 minute; (D) steel ingot enters the high-temperature region, and temperature is 1180-1200 ℃, is incubated 30-160 minute, between soak, steel ingot is stood up, and reduces steel ingot male and female face temperature difference; (E) the hot-working cogging just can be carried out in steel ingot male and female face temperature difference≤20 ℃, enters the milling train heating once and rolling;

(2), milling train hot-working cogging requires: before (A) rolling, close the cooling water of roll earlier, the cooling water of bearing shell suitably turns down, and avoids the cooling water of bearing shell to be splashed to the body of roll; Arrange the rolling 4-6 of other steel ingot elder generation to prop up, roll is preheated to 100-200 ℃ of temperature, allows rolling air valve steel; (B) rolling mill roll speed is with the execution of creeping, and the column crystal of the broken steel ingot as cast condition of similar road roller pressing physical circuit face form reduces the tension of roll to rolled piece to greatest extent, the speed of rolls≤20 rev/min; (C) start rolling temperature of steel ingot 〉=1150 ℃, finishing temperature 〉=1020 ℃, a fire time rolling schedule passage 10-18 road; (D) steel ingot is when the milling train flat-bottom hole of preceding 8 passages is rolling, and percentage elongation and surperficial broadening amount are controlled in strictness, drafts≤20mm, and keep the rolling of a direction.

Compare with prior art, the present invention has following advantage:

1, technology is simple, workable, and organization of production is convenient;

2, the production cycle shortens greatly;

3, the metal billet yield improves greatly;

4, metallurgical manufacturing cost reduces greatly.

Specific embodiments

Certain special steel company implements patent of the present invention, adopts the hot-working cogging of continuous furnace heating steel ingot (the heavy 40Kg of ingot)+milling train (400 milling train) heating once and rolling, produces air valve steel steel billet (55 * 55mm).During the milling train heating once and rolling, (A) steel ingot enters the preheating zone, and 300 ℃ of charging temperatures are incubated 120 minutes; (B) jacking up steel machine is pushed steel ingot to middle warm area, and temperature is 800 ℃, is incubated 30 minutes; (C) steel ingot enters the high-temperature region, and under 1180-1200 ℃ temperature, the steel ingot insulation was stood up after 60 minutes, reduced steel ingot male and female face temperature difference, and the steel ingot that climbs over body is incubated 10 minutes again; (D) the hot-working cogging just can be carried out in steel ingot male and female face temperature difference≤20 ℃, enters the milling train heating once and rolling; During milling train hot-working cogging, (A) rolling before, close the cooling water of roll earlier, the cooling water of bearing shell suitably turns down, and avoids the cooling water of bearing shell to be splashed to the body of roll; Arrange rolling 5 earlier on other steel ingot, make the roll preheat temperature reach 160 ℃; (B) rolling mill roll speed is with the execution of creeping, the speed of rolls≤20 rev/min; (C) start rolling temperature of steel ingot is 1150 ℃, 1020 ℃ of finishing temperatures, a fiery rolling schedule passage 13 roads; (D) steel ingot is when the milling train flat-bottom hole of preceding 8 passages is rolling, strict control percentage elongation and surperficial broadening amount, drafts 10-20mm (column crystal of the broken steel ingot as cast condition of similar road roller pressing physical circuit face form reduces the tension of roll to rolled piece to greatest extent), and keep the rolling of a direction.

Implement patent of the present invention the air valve steel is carried out the hot-working cogging, have that technology is simple, organization of production is convenient, the characteristics of metallurgical low cost of manufacture, compare with traditional " smelting ingot casting-forging and pressing cogging " production technology, production cycle shortens more than 5 times, the metal billet yield is more than 92%, and metallurgical manufacturing cost reduces by 300 yuan/ton more than the steel; The Φ 12mm finished product material of making by 55 side mm air valve steel (milling train hot-working cogging production), material amount all satisfies the regulation (see Table, table two) of GB/T12773-1991 standard in it, meet the product quality requirement, the billet surface quality is better than forging and pressing cogging, steel ingot cogging, the qualification rate 100% of becoming a useful person, remarkable in economical benefits.

The metal billet yield of strip plate, low multiple quality

Table 1

Φ 12mm finished product material low multiple quality and annealing hardness test result

Table 2

Claims (1)

1, the production method of cogging by air-valve steel rolling is characterized in that adopting the hot-working cogging technics of " continuous furnace heats steel ingot+milling train heating once and rolling ", produces air valve steel steel billet:

(1), hot-working big mill heating once and rolling requires: (A) continuous furnace heating steel ingot, steel ingot weight 30-60Kg; (B) steel ingot enters the preheating zone, and charging temperature≤300 ℃ are incubated 100-150 minute; (C) jacking up steel machine is pushed steel ingot to middle warm area, and temperature is 700-900 ℃, is incubated 20-40 minute; (D) steel ingot enters the high-temperature region, and temperature is 1180-1200 ℃, is incubated 30-160 minute, between soak, steel ingot is stood up, and reduces steel ingot male and female face temperature difference; (E) the hot-working cogging just can be carried out in steel ingot male and female face temperature difference≤20 ℃, enters the milling train heating once and rolling;

(2), milling train hot-working cogging requires: before (A) rolling, close the cooling water of roll earlier, the cooling water of bearing shell suitably turns down, and avoids the cooling water of bearing shell to be splashed to the body of roll; Arrange the rolling 4-6 of other steel ingot elder generation to prop up, roll is preheated to 100-200 ℃ of temperature, allows rolling air valve steel; (B) rolling mill roll speed is with the execution of creeping, and the column crystal of the broken steel ingot as cast condition of similar road roller pressing physical circuit face form reduces the tension of roll to rolled piece to greatest extent, the speed of rolls≤20 rev/min; (C) start rolling temperature of steel ingot 〉=1150 ℃, finishing temperature 〉=1020 ℃, a fire time rolling schedule passage 10-18 road; (D) steel ingot is when the milling train flat-bottom hole of preceding 8 passages is rolling, and percentage elongation and surperficial broadening amount are controlled in strictness, drafts≤20mm, and keep the rolling of a direction.