The Manufacturing Process of Seamless steel Tubes in China

China is known for its vast manufacturing capabilities and its ability to produce a wide range of products. One industry in which China has made significant strides is the production of seamless steel tubes. These tubes are widely used in various industries, including Oil and gas, automotive, and construction. In this article, we will explore the manufacturing process of seamless steel tubes in China.

Labels		Outside diameter (d/mm)	T&C (kg/m)	Wall thickness   (t/mm)	Type of end-finish
1	2				J55/ K55	M65	L80/ R95	N80-1/Q	C90/ T95	P110	Q125
4-1/2	9.50	114.30	14.14	5.21	PS	PS	–	–	–	–	–
	10.50	114.30	15.63	5.69	PSB	PSB	–	–	–	–	–
	11.60	114.30	17.26	6.35	PSLB	PLB	PLB	PLB	PLB	PLB	–
	13.50	114.30	20.09	7.37	–	PLB	PLB	PLB	PLB	PLB	–
	15.10	114.30	22.47	8.56	–	–	–	–	–	PLB	PLB
5	11.50	127.00	17.11	5.59	PS	PS	–	–	–	–	–
	13.00	127.00	19.35	6.43	PSLB	PSLB	–	–	–	–	–
	15.00	127.00	22.32	7.52	PSLB	PLB	SLB	PLB	PLB	PLB
	18.00	127.00	26.79	9.19	–	PLB	SLB	PLB	PLB	PLB	PLB
	21.40	127.00	31.85	11.10	–	PLB	PLB	PLB	PLB	PLB	PLB
	23.20	127.00	34.53	12.14	–	–	PLB	PLB	PLB	PLB	PLB
	24.10	127.00	35.87	12.70	–	–	PLB	PLB	PLB	PLB	PLB
5-1/2	14.00	139.70	20.83	6.20	PS	PS	–	–	–	–	–
	15.50	139.70	23.07	6.98	PSLB	PSLB	–	–	–	–	–
	17.00	139.70	25.30	7.72	PSLB	PLB	PLB	PLB	PLB	PLB	–
	20.00	139.70	29.76	9.17	–	PLB	PLB	PLB	PLB	PLB	–
	23.00	139.70	34.23	10.54	–	PLB	PLB	PLB	PLB	PLB	PLB
	26.80	139.70	39.88	12.70	–	–	–	–	P	–	–
	29.70	139.70	44.20	14.27	–	–	–	–	P	–	–
	32.60	139.70	48.52	15.88	–	–	–	–	P	–	–
	35.30	139.70	52.53	17.45	–	–	–	–	P	–	–
	38.00	139.70	56.55	19.05	–	–	–	–	P	–	–
	40.50	139.70	60.27	20.62	–	–	–	–	P	–	–
	43.10	139.70	64.14	22.22	–	–	–	–	P	–	–
6-5/8	20.00	168.28	29.76	7.32	PSLB	PSLB	–	–	–	–	–
	24.00	168.28	35.72	8.94	PSLB	PLB	PLB	PLB	PLB	PLB	–
	28.00	168.28	41.67	10.59	–	PLB	PLB	PLB	PLB	PLB	–
	32.00	168.28	47.62	12.06	–	–	PLB	PLB	PLB	PLB	PLB
7	17.00	177.80	25.30	5.87	–	–	–	–	–	–	–
	20.00	177.80	29.76	6.91	PS	PS	–	–	–	–	–
	23.00	177.80	34.23	8.05	PSLB	PLB	PLB	PLB	PLB	–	–
	26.00	177.80	38.69	9.19	–	PLB	PLB	PLB	PLB	PLB	–
	29.00	177.80	43.16	10.36	–	PLB	PLB	PLB	PLB	PLB	–
	32.00	177.80	47.62	11.51	–	PLB	PLB	PLB	PLB	PLB	–
	35.00	177.80	52.09	12.65	–	–	PLB	PLB	PLB	PLB	PLB
	38.00	177.80	56.55	13.72	–	–	PLB	PLB	PLB	PLB	PLB
	42.70	177.80	63.55	15.88	–	–	–	–	P	–	–
	46.40	177.80	69.05	17.45	–	–	–	–	P	–	–
	50.10	177.80	74.56	19.05	–	–	–	–	P	–	–
	53.60	177.80	79.77	20.62	–	–	–	–	P	–	–
	57.10	177.80	84.98	22.22	–	–	–	–	P	–	–
7-5/8	24.00	193.68	35.72	7.62	–	–	–	–		–	–
	26.40	193.68	39.29	8.33	PSLB	PSLB	PLB	PLB	PLB	–	–
	29.70	193.68	44.20	9.52	–	PLB	PLB	PLB	PLB	PLB	–
	33.70	193.68	50.15	10.92	–	PLB	PLB	PLB	PLB	PLB	–
	39.00	193.68	58.04	12.70	–	–	PLB	PLB	PLB	PLB	PLB
	42.80	193.68	63.69	14.27	–	–	PLB	PLB	PLB	PLB	PLB
	45.30	193.68	67.42	15.11	–	–	PLB	PLB	PLB	PLB	PLB
	47.10	193.68	70.09	15.88	–	–	PLB	PLB	PLB	PLB	PLB
	51.20	193.68	76.20	17.45	–	–	–	–	P	–	–
	55.30	193.68	82.30	19.05	–	–	–	–	P	–	–
7-3/4	46.10	196.85	68.61	15.11	–	–	P	P	P	P	P
8-5/8	24.00	219.08	35.72	6.71	PS	PS	–	–	–	–	–
	28.00	219.08	41.67	7.72		PS	–	–	–	–	–
	32.00	219.08	47.62	8.94	PSLB	PSLB	–	–	–	–	–
	36.00	219.08	53.58	10.16	PSLB	PSLB	PLB	PLB	PLB	PLB	–
	40.00	219.08	59.53	11.43	–	PLB	PLB	PLB	PLB	PLB	–
	44.00	219.08	65.48	12.70	–	–	PLB	PLB	PLB	PLB	–
	49.00	219.08	72.92	14.15	–	–	PLB	PLB	PLB	PLB	PLB
9-5/8	32.30	244.48	48.07	7.92	–	–	–	–	–	–	–
	36.00	244.48	53.58	8.94	PSLB	PSLB	–	–	–	–	–
	40.00	244.48	59.53	10.03	PSLB	PSLB	PLB	PLB	PLB	–	–
	43.50	244.48	64.74	11.05	–	PLB	PLB	PLB	PLB	PLB	–
	47.00	244.48	69.95	11.99	–	PLB	PLB	PLB	PLB	PLB	PLB
	53.50	244.48	79.62	13.84	–	–	PLB	PLB	PLB	PLB	PLB
	58.40	244.48	86.91	15.11	–	–	PLB	PLB	PLB	PLB	PLB
	59.40	244.48	88.40	15.47	–	–	–	–	P	–	–
	64.90	244.48	96.58	17.07	–	–	–	–	P	–	–
	70.30	244.48	104.62	18.64	–	–	–	–	P	–	–
	75.60	244.48	112.51	20.24	–	–	–	–	P	–	–
10-3/4	32.75	273.05	48.74	7.09	–	–	–	–	–	–	–
	40.50	273.05	60.27	8.89	PSB	PSB	–	–	–	–	–
	45.50	273.05	67.71	10.16	PSB	PSB	–	–	–	–	–
	51.00	273.05	75.90	11.43	PSB	PSB	PSB	PSB	PSB	PSB	–
	55.50	273.05	82.60	12.57	–	PSB	PSB	PSB	PSB	PSB	–
	60.70	273.05	90.33	13.84	–	–	–	–	PSB	PSB	PSB
	65.70	273.05	97.77	15.11	–	–	–	–	PSB	PSB	PSB
	73.20	273.05	108.94	17.07	–	–	–	–	P	–	–
	79.20	273.05	117.87	18.64	–	–	–	–	P	–	–
	85.30	273.05	126.94	20.24	–	–	–	–	P	–	–
11-3/4	42.00	298.45	62.50	8.46	–	–	–	–	–	–	–
	47.00	298.45	69.95	9.53	PSB	PSB	–	–	–	–	–
	54.00	298.45	80.36	11.05	PSB	PSB	–	–	–	–	–
	60.00	298.45	89.29	12.42	PSB	PSB	PSB	PSB	PSB	PSB	PSB
	65.00	298.45	96.73	13.56	–	–	P	P	P	P	P
	71.00	298.45	105.66	14.78	–	–	P	P	P	P	P
13-3/8	48.00	339.72	71.43	8.38	–	–	–	–	–	–	–
	54.50	339.72	81.11	9.65	PSB	PSB	–	–	–	–	–
	61.00	339.72	90.78	10.92	PSB	PSB	–	–	–	–	–
	68.00	339.72	101.20	12.19	PSB	PSB	PSB	PSB	PSB	PSB	–
	72.00	339.72	107.15	13.06	–	–	PSB	PSB	PSB	PSB	PSB
16	65.00	406.40	96.73	9.53	–	–	–	–	–	–	–
	75.00	406.40	111.62	11.13	PSB	PSB	–	–	–	–	–
	84.00	406.40	125.01	12.57	PSB	PSB	–	–	–	–	–
	109.00	406.40	162.21	16.66	P	–	P	P	–	P	P
18-5/8	87.50	473.08	130.22	11.05	PSB	PSB	–	–	–	–	–
20	94.00	508.00	139.89	11.13	PSLB	PSLB	–	–	–	–	–
	106.50	508.00	158.49	12.70	PSLB	PSLB	–	–	–	–	–
	133.00	508.00	197.93	16.13	PSLB	–	–	–	–	–	–

The process of manufacturing seamless steel tubes begins with the selection of high-quality raw materials. China has access to abundant resources of iron ore, which is the primary raw Material used in the production of steel. The iron ore is extracted from mines and undergoes a series of processes, including crushing, grinding, and magnetic separation, to obtain iron ore concentrate.

Item No	Product name	Standard	Steel grade		Size(mm)	Application
1	pressure fluid steel Pipe	ASTM A106	Gr.A、Gr.B、Gr.C		OD：21.3-1220	boiler,heat exchanger,medium low pipeline
		ASTM A53			Wall:2.0-100
2	casing,oil pipe,coupling	API5CT PSL1、	group1:J55、 K55、N80、R95		OD：26.7-762	Steel tube for oil field
		PSL2 PSL3	group2:L80、 C90、T95		Wall:2.87-40
			group3:P110
3	pipeline transportation system	API5L	A、B、X42、X46、X52、X60、X65、X70、X80		OD：26.7-1220	oil and gas pipeline, refining equipment pipeline
		PSL1			Wall:2.87-100
		PSL2
4	mechanical high precision seamless pipe	ASTM A519	SAE1018、SAE1020、SAE1045、SAE1518、SAE1541、SAE4130、SAE4135、SAE4140、SAE8620、ST78、ST52、E215、E235、E355、E410、C35E、C45E、25CrMo4、42CrMo4		OD：21.3-406	high precision machined seamless tube,construction machine,automobile engine
		EN10305-1			Wall:2.0-40
		DIN2391
		GB3639
5	heat exchanger and condenser low carbon cold drawn seamless pipe	ASTM A179	A179		OD：6-76.2	heat exchanger
					Wall:1.0-20
6	high pressure Carbon steel seamless boiler pipe	ASTM A192	A192		OD：12.7-177.8	high pressure boiler tube
					Wall:2.0-25.4
7	boder,superheater unit medium carbon Seamless steel pipe	ASTM A210	A210A-1		OD：12.7-127	high pressure toiler and heat exchanger
			A210-C		Wall:0.9-12.7
8	boiler,superheater unit femilic Alloy steel pipe	ASTM A213	T2、T11、T12、T22、T5、T5b、T5C		OD：6-127	high pressure boiler,superheater unit, heat exchanger alloy steel tube
					Wall:0.4-12
9	seamless steel pipe for pressure purpose	EN10216-1	195GH、P235GH、P265GH、20MnNb6、16Mo3、13CrMo4-5	OD：21.3-762		pressure piping
		EN10216-2		Wall:2.0-40
10	gas cylinder seamless steel pipe	GB18248	37Mn、34Mn2V、30CrMo、35CrMo、34CrMo4、30CrMnSiA、STH11、STH12、STH21、STH22、STH31	OD：76-356		high pressure gas cylinder
		JIS G3429		Wall:2.5-6.0
11	the automotive axle pipe	YB/T 5035	45#、45Mn2、40MnB、40Cr	OD：76-121		automobile application
				Wall:7.0-28.5

Once the iron ore concentrate is obtained, it is mixed with other additives, such as limestone and coke, and then smelted in a blast furnace. The smelting process involves the reduction of iron ore to molten iron, which is then converted into steel through a refining process. China has advanced steelmaking technologies and state-of-the-art facilities that ensure the production of high-quality steel. After the steel is produced, it is cast into billets or blooms, which are semi-finished forms of steel. These billets or blooms are then heated and pierced to create a hollow tube. This process is known as piercing, and it is a critical step in the manufacturing of seamless steel tubes. China has developed advanced piercing technologies that ensure the production of tubes with precise dimensions and smooth surfaces. Once the tubes are pierced, they undergo a series of processes to further refine their shape and dimensions. These processes include elongation, rolling, and sizing. Elongation involves stretching the tube to reduce its diameter and increase its Length. Rolling is done to improve the surface finish and remove any imperfections. Sizing is the final step in the process, where the tube is passed through a series of rollers to achieve the desired dimensions. China has invested heavily in the development of advanced manufacturing technologies for seamless steel tubes. These technologies include the use of computer-controlled machines and automated production lines. These advancements have not only improved the efficiency of the manufacturing process but also ensured the production of tubes with consistent quality.

Tensile and Hardness Requirements
Grade			Yield strength MPa		Tensile Strength	Hardness a,c		Specified Wall Thickness	Allowable Hardness Variation b
	Type	Total Elongation Under Load			min MPa	max
			min	max		HRC	HBW	mm	HRC
1	2	3	4	5	6	7	8	9	10
H40	—	0.5	276	552	414	—	—	—	—
J55	—	0.5	379	552	517	—	—	—	—
K55	—	0.5	379	552	655	—	—	—	—
N80	1	0.5	552	758	689	—	—	—	—
N80	Q	0.5	552	758	689	—	—	—	—
R95	—	0.5	655	758	724	—	—	—	—
L80 L80	1	0.5	552	655	655	23	241	—	—
L80	9Cr 13Cr	0.5	552	655	655	23	241	—	—
		0.5	552	655	655	23	241	—	—
C90	1	0.5	621	724	689	25.4	255	£12.70	3
								12.71 to 19.04	4
								19.05 to 25.39	5
								³ 25.40	6
T95	1	0.5	655	758	724	25.4	255	£12.70	3
								12.71 to 19.04	4
								19.05 to 25.39	5
								³ 25.40	6
C110	—	0.7	758	828	793	30	286	£12.70	3
								12.71 to 19.04	4
								19.05 to 25.39	5
								³ 25.40	6
P110	—	0.6	758	965	862	—	—	—	—
Q125	1	0.65	862	1034	931	b	—	£12.70	3
								12.71 to 19.04 19.05	4
									5
a In case of dispute, laboratory Rockwell C hardness testing shall be used as the referee method.
b No hardness limits are specified, but the maximum variation is restricted as a manufacturing control in accordance with 7.8 and 7.9.
c For through-wall hardness tests of Grades L80 (all types), C90, T95 and C110, the requirements stated in HRC scale are for maximum mean hardness number.

In addition to the manufacturing process, China also places great emphasis on quality control. Strict quality control measures are implemented at every stage of the production process to ensure that the tubes meet the required specifications. China has established testing laboratories equipped with advanced testing equipment to conduct various tests, including chemical analysis, mechanical testing, and Non-destructive testing.

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