Patent ID: 12258652

DETAILED DESCRIPTION OF THE EMBODIMENTS

In order to highlight the purpose, technical solutions and advantages of the present disclosure, the present disclosure will be further described below in combination with the examples which am illustrated by way of explanation of the disclosure rather than limiting the present disclosure. The technical solutions of the present disclosure are not limited to the specific embodiments listed below, but also include any combination of the specific embodiments.

The ferrochromium nitride of the present disclosure can be any brand of ferrochromium nitride with a nitrogen content of more than 3 wt %. In the following examples, ferrochromium nitride with the brand name FeNCr3-A is used as an example for illustration.

Example 1

In the example 1 of the present disclosure, a VIM furnace with a nominal capacity of 6 tons is used for smelting the high-temperature alloy with ultra-high N content, comprising the following steps:Step 1, Ferrochromium nitride baking: Ferrochromium nitride is baked in a high-temperature annealing furnace in the plant.

In the step, the parameters for baking the ferrochromium nitride comprise: N content (i.e., the mass percentage of N in ferrochromium nitride): 5.1%; baking (heating) temperature: 930° C.; baking time: 8.5 hours.Step 2, Charging before the smelting: Ni, Fe, Nb, Cr and other raw materials are successively charged into the VIM furnace; 100% of the ferrochromium nitride is reserved without addition; and 20% of the metallic chromium is reserved without addition.Step 3, Smelting process: The raw materials are smelted (including a melting period and a refining period, wherein the indication for the completion of the melting period is the monitored full melting temperature of 1530° C., and the temperature of the refining period is 1510° C., and the time thereof is 130 minutes), in which, in the later stage of the refining period, the required amount of metallic chromium is added to adjust the composition, and afterwards, in the later stage of the refining, argon gas is introduced into the furnace so that the argon pressure in the furnace of 10,000 pa is achieved. Then ferrochromium nitride is added to adjust the N content.Step 4, Casting process: The liquid molten steel obtained from the smelting process is cast, in which the time from the adding of ferrochromium nitride to the start of casting (steel tapping) is 14 minutes.Step 5, Inspection: The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.061%; Cr 25.40%; Ni: 37.03%; P: 0.006%; S: 0.002%; Mn: 0.74%; Si: 0.470%; B: ≤0.01%; Nb: 0.63%; N: 0.2857%; Al: 0.230%; Ti: 0.05%; Cu: 0.01%; H: 0.0001%.

The yield of nitrogen (i.e., nitrogen yield which is the ratio of the nitrogen content in the obtained product to the content of the nitrogen entrained from the raw materials used) and yield rate are 76.92% and 100%, respectively.

Example 2

In the example 2 of the present disclosure, a VIM furnace with a nominal capacity of 6 tons is used for smelting the high-temperature alloy with ultra-high N content, comprising the following steps:Step 1, Ferrochromium nitride baking: Ferrochromium nitride is baked in a high-temperature annealing furnace in a plant.

In the step, the parameters for baking the ferrochromium nitride comprise: N content: 5.1%; baking (heating) temperature: 930° C.; baking time: 8.0 hours.Step 2, Charging before the smelting: Ni, Fe, Nb, Cr and other raw materials are successively charged into the VIM furnace; 100% of the ferrochromium nitride is reserved without addition; and 20% of the metallic chromium is reserved without addition.Step 3, Smelting process: The raw materials am smelted (including a melting period and a refining period, wherein the indication for the completion of the melting period is the monitored full melting temperature of 1533° C., and the temperature of the refining period is 1510° C., and the time thereof is 130 minutes), wherein, in the smelting process, the required amount of metallic chromium is added to adjust the composition, and afterwards, in the later stage of the refining, argon gas is introduced to a pressure of 10000 pa. Then ferrochromium nitride is added to adjust the N content.Step 4, Casting process: The liquid molten steel obtained from the smelting process is cast, in which the time from the addition of ferrochromium nitride to the start of casting (steel tapping) is 15 minutes.Step 5, Inspection: The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.060%; Cr 25.60%; Ni: 37.00%; P: 0.005%; S: 0.001%; Mn: 0.76%; Si: 0.440%; Nb: 0.63%; N: 0.2893%; Al: 0.250%; Ti: 0.04%; Cu: 0.01%; H: 0.0001%.

The yield of nitrogen and yield rate am 76.90% and 100%, respectively.

Example 3

The Example 3 is carried out similarly to the Example 1, except that the baking temperature of the ferrochromium nitride is set to 800° C.Step 5, Inspection: The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.061%; Cr 25.30%; Ni: 37.05%; P: 0.005%; S: 0.002%; Mn: 0.75%; Si: 0.500%; B: ≤0.01%; Nb: 0.65%; N: 0.2937%; Al: 0.250%; Ti: 0.05%; Cu: 0.01%; H: 0.00015%.

The yield of nitrogen and yield rate am 76.70% and 100%, respectively.

Example 4

The Example 4 is carried out similarly to the Example 1, except that the baking temperature of ferrochromium nitride is 1050° C.Step 5: Inspection: The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.059%; Cr 25.33%; Ni: 37.00%; P: 0.004%; S: 0.001%; Mn: 0.70%; Si: 0.480%; B: ≤0.01%; Nb: 0.62%; N: 0.2900%; Al: 0.250%; Ti: 0.04%; Cu: 0.01%; H: 0.00015%

The yield of nitrogen and yield rate am 76.80% and 100%, respectively.

Comparative Example 1

The Comparative Example 1 is carried out similarly to the Example 1, except that the baking temperature of ferrochromium nitride is 650° C.Step 5: Inspection: The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.061%; Cr 25.35%; Ni: 37.01%; P: 0.005%; S: 0.001%; Mn: 0.72%; Si: 0.500%; B: ≤0.01%; Nb: 0.65%; N: 0.2955%; Al: 0.250%; Ti: 0.05%; Cu: 0.01%; H: 0.00035% (the lower the H content during the application of the alloy is, the better results are obtained. If it is too high, the durability and fatigue life may be affected in the application of users).

The yield of nitrogen is 76.80%.

Comparative Example 2

The Comparative Example 2 is carried out similarly to the Example 1, except that the baking temperature of ferrochromium nitride is 1200° C.Step 5, Inspection: The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.060%; Cr 25.30%; Ni: 37.05%; P: 0.005%; S: 0.001%; Mn: 0.72%; Si: 0.460%; B: ≤0.01%; Nb: 0.60%; N: 0.2890%; Al: 0.250%; Ti: 0.05%; Cu: 0.01%; H: 0.00009%.

The yield of nitrogen is 63.34%.

Comparative Example 3

The Comparative Example 3 is carried out similarly to the Example 1, except that the argon gas is introduced so that the pressure in the furnace of 9000 Pa is achieved.Step 5, Inspection: The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.059%; Cr 25.33%; Ni: 37.10%; P: 0.005%; S: 0.001%; Mn: 0.70%; Si: 0.510%; B: ≤0.01%; Nb: 0.66%; N: 0.2910%; Al: 0.260%; Ti: 0.06%; Cu: 0.01%; H: 0.0001%.

The yield of nitrogen and yield rate are 74.38% and 100%, respectively.

Comparative Example 4

The Comparative Example 4 is carried out similarly to the Example 1, except that the time from the addition of ferrochromium nitride to the steel tapping is 17 minutes.

The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.062%; Cr 25.28%; Ni: 37.15%; P: 0.005%; S: 0.001%; Mn: 0.60%; Si: 0.500%; B: ≤0.01%; Nb: 0.67%; N: 0.2913%; Al: 0.250%; Ti: 0.06%; Cu: 0.01%; H: 0.0001%.

The yield of nitrogen and yield rate are 75.80% and 100%, respectively.

Comparative Example 5

The Comparative Example 5 is carried out similarly to the Example 1, except that the step 1 in the Example 1, that is, the step of baking the ferrochromium nitride, is omitted.

The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.059%; Cr 25.30%; Ni: 37.20%; P: 0.005%; S: 0.001%; Mn: 0.68%; Si: 0.520%; B: ≤0.01%; Nb: 0.68%; N: 0.2910%; Al: 0.250%; Ti: 0.06%; Cu: 0.01%; H: 0.0005%.

A large amount of H element is brought into the alloy by the chromium nitride due to the fact that the chromium nitride is not baked, and accordingly, the content of H element in the alloy is too high and the alloy obtained is thus a waste product.

The yield of nitrogen and yield rate are 76.15% and 0.0%, respectively.

Comparative Example 6

The Comparative Example 6 is carried out similarly to the Example 1, except that the procedure of introducing argon gas into the furnace during the smelting process in the Example 1 is omitted, that is, no argon gas is introduced in the later stage of the refining.

The composition content of the cast (wt %) is inspected according to the standard requirements, C: 0.059%; Cr 25.34%; Ni: 37.15%; P: 0.005%; S: 0.001%; Mn: 0.71%; Si: 0.520%; B: ≤0.01%; Nb: 0.65%; N: 0.1010%; Al: 0.270%; Ti: 0.06%; Cu: 0.01%; H: 0.0001%.

In the case of no argon gas being introduced, after the ferrochromium nitride added to the furnace is melted and decomposed, a part of the nitrogen element is removed out of the furnace in the form of N2in free state with the vacuum system in a high vacuum condition. As a result, the yield of nitrogen element is very low, and the nitrogen element in the alloy cannot meet the standard requirements and eventually is a waste product.

The yield of nitrogen and yield rate am 33.34% and 0.0%, respectively.